8,339 results on '"Constitutive model"'
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102. A Critical State Constitutive Model for Methane Hydrate‐Bearing Sediments Considering Hydrate Pore‐Filling and Cementing Effects.
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Zhu, Bin, Yuan, Simin, Wang, Lujun, Liu, Yanjing, and Chen, Yunmin
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METHANE hydrates , *SOIL particles , *SHEAR strength , *MECHANICAL models , *ANISOTROPY - Abstract
To safely and effectively explore the natural methane hydrate, it is crucial to examine the mechanical behavior of methane hydrate‐bearing sediments (MHBSs). Natural methane hydrate unevenly distributes in pores or bonds with soil particles in MHBS, changing the mechanical behavior of MHBS including stiffness, shear strength, and dilatancy. This paper presents an anisotropic critical state model for MHBS considering hydrate pore‐filling and cementing effects. Based on the unified critical state model for both clay and sand, an equivalent hydrate ratio is defined to address pore‐filling effect. Cohesive strength and its hardening law are introduced to characterize hydrate cementation. To describe the anisotropic behavior, the inherent anisotropy of soil particles and hydrates are modeled separately, and rotation hardening is introduced to describe the stress‐induced anisotropy. Comparisons with existing triaxial tests of both synthetic and natural MHBS demonstrate that the proposed model comprehensively describes the mechanical behavior of MHBS. Detailed predictions indicate that hydrate pore‐filling affects the hydrate‐dependent stiffness and dilatancy of MHBS, which become more pronounced with increasing hydrate saturation. Cementing effect increases the initial stiffness and peak strength of MHBS. The pronounced influence of inherent anisotropic parameters on pre‐peak stress–strain relation of MHBS is noted, and increasing hydrate saturation enhances the effect of hydrate anisotropy. These predictions contribute to a better understanding of the relation between hydrate morphologies and MHBS mechanical properties. [ABSTRACT FROM AUTHOR] more...
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- 2025
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103. A Small-Strain Hypoelastic Constitutive Model and Application to Foundation Field Tests for Initial Stiffness Evaluation.
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Huang, Yunhan, Gilbert, Robert, Wang, Shin-Tower, Stokoe, Kenneth, Kaçar, Onur, and Wang, Peipei
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MODULUS of rigidity , *FINITE element method , *SHALLOW foundations , *DYNAMIC testing , *CURVATURE - Abstract
The small-strain stiffness of soil measured through dynamic tests can be utilized in the finite element method to simulate static conditions. Although numerous soil constitutive models incorporated the elastic law of the maximum shear modulus and normalized shear modulus degradation curves to simulate the small-strain behavior of soil, rare models can be calibrated using the normalized shear modulus degradation curves measured from the resonant column and torsional shear tests varying a wide range of mean effective stresses. The poor calibration of the elastic law in the soil constitutive model may result in uncertainties when simulating the initial stiffness of the foundation in finite element modeling. The current study developed a small-strain hypoelastic model based on normalized shear modulus degradation curves using four material parameters that provide greater flexibility in controlling the curvature shape of the degradation curves. The small-strain hypoelastic model was evaluated using an element test and applied to a settlement test on a shallow foundation, a laterally loaded test on a slender pile, and a series of laterally loaded tests on monopiles. The results indicated that the reference strain and curvature parameter in the empirical equations for the normalized shear modulus degradation curves should be related to the mean effective stress, and the curves should be carefully calibrated by using resonant column and torsional shear tests under low mean effective stresses. The calibrated hypoelastic model significantly improved the accuracy of predicting the nonlinear initial stiffness in finite element modeling. The suggested procedure of calibrating the small-strain hypoelastic model was proposed to provide guidance in various engineering practices. [ABSTRACT FROM AUTHOR] more...
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- 2025
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104. Three-Dimensional Numerical Realization And Application Of Collapsible Loess Constitutive Model Considering Initial Water Content.
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Weng, Xiaolin, Hou, Lele, Li, Xuancong, Li, Zejie, and Zhou, Rongming
- Abstract
The structural evolution of loess under load and humidification plays an important role in the safety evaluation of engineering in loose area. A simplified constitutive model is developed by incorporating the structural composition of collapsible loess in this paper. The user defined material subroutine (UMAT) of this model is programmed using an improved Euler integration algorithm with error control. A stress correction technique is incorporated in the UMAT subroutine to improve the computational accuracy and efficiency. Comparisons between UMAT subroutine simulation results, existing experimental results and result from the MATLAB program shows the validity and stability of this UMAT subroutine. Examples of three-dimensional square foundation and pit excavation using the UMAT subroutine is analysed, the simulation results demonstrates its reliability in capturing the general features of the wetting collapse for collapsible loose. These results can provide reference for the secondary development of relevant critical state models and offer a new approach for the engineering application of constitutive models for collapsible loess. [ABSTRACT FROM AUTHOR] more...
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- 2025
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105. Nonlinearly elastic and anisotropic constitutive model for ePTFE vascular graft based on tensile and inflation experiments.
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Sobotka, Zbyněk, Horný, Lukáš, Chlup, Hynek, Kohan, Miroslav, Hudák, Radovan, and Valášek, Michael
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VASCULAR grafts , *EXPONENTIAL functions , *OPERATIVE surgery , *MECHANICAL models , *TISSUES - Abstract
AbstractThe long-term success of interventions in cardiovascular medicine can be enhanced by the computer-assisted planning of these procedures. However, the reliability of all computational simulations depends significantly on the input parameters. One of the most important is the constitutive model for the biological tissue and for the implant material. While the last few decades have brought great advances in modeling the mechanical properties of the arterial wall, synthetic grafts have not received as much attention. The primary goal of our research is to contribute to filling this gap. Our study is focused on determining a constitutive model for ePTFE vascular grafts. Uniaxial tensile experiments with strips cut from tubular vascular grafts SA1802 (Gore-Tex Stretch Vascular Graft – Large diameter) in the circumferential and longitudinal direction, and pressurization experiments with intact graft tubes V06010L (Gore-Tex Vascular Graft – Standard-walled) were carried out. A nonlinearly elastic anisotropic model was used to describe the mechanical response observed in these experiments. The four-fiber hyperelastic model based on the exponential function combined with the neo-Hookean term was able to fit the data observed in both the uniaxial tensile and inflation-extension experiments with one single set of parameters. Thus, the resulting model is suitable to be used in numerical simulations studying surgical procedures involving ePTFE vascular grafts in the mechanical states of uniaxial as well as multiaxial stress. [ABSTRACT FROM AUTHOR] more...
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- 2024
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106. Correction method of Mohr-Coulomb strength criterion for rock based on freeze-thaw and residual effects.
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Liu, Yang, Meng, Xiangzhen, Zhang, Huimei, and Shen, Yanjun
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ROCK deformation , *RESIDUAL stresses , *ROCK testing , *FREEZE-thaw cycles , *TEMPERATURE effect ,COLD regions - Abstract
Under confining pressure, rocks transition from brittle failure to plastic failure, and residual strength exists after complete failure. However, in the process of establishing rock damage constitutive models, the strength criteria used usually do not consider residual stress. In cold region engineering, the freeze-thaw effect caused by temperature changes should be considered in the constitutive model, and strength criteria should also be introduced. Considering the failure characteristics of micro element when rock is subjected to freeze-thaw and load, and based on the impact of reducing the effective bearing area on each damage, the total damage variable and constitutive model of rock under freeze-thaw and load are established. Starting from the characteristics of the entire process of rock deformation, the revised Mohr-Coulomb (M-C) strength criterion of rock is established by considering freeze-thaw cycles and residual effects. The results show that: The theoretical curve and test curve of the constitutive model are not completely consistent, but the variance R2 between the two does not exceed 0.6, indicating that the theoretical curve is in good agreement with the test curve and can reflect the entire process of rock deformation and failure, verifying the rationality of the constitutive model and damage variable description. With the increasing of freeze-thaw cycles, the strength decreases and the deformation increases of rock. As the number of freeze-thaw cycles increases, the strength decreases and deformation increases. When the freeze-thaw cycle reaches 40 cycles, the strength decreases by more than 60%. With the increasing of confining pressure, the strength and deformation also increase. When the confining pressure increases from 0 to 6 MPa, the strength of red sandstone increases by more than 80% under the same freeze-thaw cycles, which is consistent with the actual situation. The revised M-C strength criterion data does not exceed the test data and is relatively close to the test data. The difference between the two is less than 25%, indicating that the established strength criteria can be safely used as a basis for rock elemental failure, verifying the rationality of the strength standard considering freeze-thaw and residual effects. This Revised M-C strength criterion introduces the influence of freeze-thaw cycles and residual stress factors, which not only characterizes the relationship between internal stress parameters in rock limit states under different freeze-thaw cycles, but also addresses the disadvantage of Drucker-Prager (D-P) criterion being more conservative. This method is based on the measured results of rock triaxial test, which makes it more flexible and the calculation results closer to reality. [ABSTRACT FROM AUTHOR] more...
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- 2024
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107. Development of high-performance nanostructured aluminum and its constitutive modeling.
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Deka, Surja, Mozafari, Farzin, Mallick, Ashis, Thamburaja, Prakash, and Gupta, Manoj
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MECHANICAL alloying , *FINITE element method , *MATERIAL plasticity , *BALL mills , *ALUMINUM - Abstract
A new technique, an in-situ hot-extrusion-based synthesizing process, is proposed to develop high-performance nanocrystalline aluminum (nc-Al) with an optimally tuned strength-to-ductility ratio suitable for various technologically relevant applications. Comprehensive investigations are conducted by characterizing mechanical and microstructural properties to realize the influence of various synthesizing variables on the properties of the bulk nc-Al. Furthermore, a continuum-scale constitutive modeling approach is proposed based on dominant microstructural mechanisms of plastic deformation and implemented into a finite element solver using a user-defined material interface. It is shown that the proposed theory can provide a versatile platform to predict the nanocrystalline aluminum mechanical response quite well. [ABSTRACT FROM AUTHOR] more...
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- 2024
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108. Damage investigation of a pressurized elbow pipe using the XFEM technique under severe cyclic loading.
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Khiari, Mohamed El Amine, Mokhtari, Mohamed, Telli, Fatna, Benzaama, Habib, and Naimi, Oussama
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STRAINS & stresses (Mechanics) , *CRACK initiation (Fracture mechanics) , *STRAIN rate , *FINITE element method , *CRACK propagation (Fracture mechanics) , *STEEL fatigue , *BENDING moment - Abstract
Given the various loading cases possible in tubular structures, cyclic bending moment is one of the frequent cases presented in bent structures attached by straight tubular parts, as in straight tubular structures or a connecting tubular element; their loading is under various cyclic modalities; analyzing these pressurized tubular structures or unlocking the difficulties of numerically predicting or approximating to possible and actual fatigue behavior is of interest to several researchers, this work opts to use 316LN stainless steel, also known as Z2CND18.12 N of an elbow attached by straight parts, the study of the cyclic response up to the damage of the pressurized bend is aimed at evaluating the behavior under the effects of the parameters analyzed, namely the amplitude and the pattern of the cyclic bending moment, The fatigue behavior of the steel is formulated as a combined isotropic and kinematic Ohno-Wang model introduced into the ABAQUS calculation code by parameters calibrated to the experimental, using the finite element method. The damage to the structure under a high cyclic bending moment is introduced into the structure mesh. Of the cyclic accumulation of stress, the damage will occur in the structure by crack initiation and propagation, hence using the XFEM technique. The non-linear behavior, independent of the strain rate, is based on the Von Mises equivalent stress flow theory by mode effect at high cyclic bending moment; the results presented by moment-rotation curves show a significant effect on the response, as well as the level of damage. That damage by crack initiation and propagation precedes excessive ovalization at the level of the elbow cross-section. The approach followed in this analysis and the reliability of the results obtained were previously based on a validation of experimental results, which showed good agreement with the numerical model used. [ABSTRACT FROM AUTHOR] more...
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- 2024
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109. The Influence of Fresh Latex Coagulation on the Parameter Characteristics of the Yeoh Hyperelastic Constitutive Model for Natural Rubber.
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Ding, Li, Huang, Honghai, Wang, Yuekun, Li, Jianwei, Gui, Hongxing, and Chen, Yongping
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MECHANICAL behavior of materials , *LATEX , *CARBON-black , *CARBON composites , *RUBBER , *COAGULATION , *DEFORMATIONS (Mechanics) - Abstract
The coagulation of fresh latex is one of the critical processes that impacts rubber quality during natural rubber processing. Constitutive relationships are the basis for the study of the mechanical properties of rubber materials and serve as a prerequisite for material simulation studies. However, studies on the effect of different coagulation methods on natural rubber constitutive relationships have yet to be carried out, and the current models used for natural rubber constitutive relationships need to be improved. In order to investigate the effects of different coagulation methods on the hyperelastic properties of natural rubber, the impact of natural coagulation, enzyme coagulation, acid coagulation, microbial coagulation, and enzyme-assisted microbial coagulation on the hyperelastic constitutive relationship of natural rubber were analyzed in detail based on tensile experiments and the Yeoh model. The results show that after introducing a strain rate-related factor, the Yeoh model can describe well the mechanical behavior of natural rubber carbon black composites in different deformation regions, and the rubber, studied with varying coagulation methods, exhibits different mechanical properties in different deformation regions. This study provides new evidence for the study of high-performance natural rubber and serves as a reference for process selection in the primary processing of natural rubber. [ABSTRACT FROM AUTHOR] more...
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- 2024
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110. Establishment and Application of an Elastic–Plastic Damage Constitutive Model for Ceramic Fiber Insulation Tiles.
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Wang, Yiming, Zhong, Yesheng, Huang, Yining, Ma, Xiaoliang, Shi, Liping, and He, Xiaodong
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CERAMIC fibers , *WORK environment , *MECHANICAL models , *TILES , *DENSITY - Abstract
A thermal protection system is critical for ensuring the safe take-off and return of various aircraft. A key heat-resistant material within this system is the ceramic fiber insulation tile (CFIT), which is a porous three-dimensional network material with density ranges from 0.3 to 0.4 g/cm3 that exhibits complex mechanical behaviors. Due to the complexity of the service environment, experimental methods cannot accurately capture the mechanical behavior of a CFIT. Although simulation-based methods can provide insights, an accurate constitutive model for CFITs has yet to be established. To predict its complex mechanical behavior, an elastic–plastic damage constitutive model was established for CFITs. Based on the Hashin criteria and four fundamental assumptions, a yield rule was modified by introducing a damage factor in the TTT direction. The model was encoded into a user–material subroutine (UAMT) integrated within ABAQUS to capture the mechanical responses under four typical working conditions. The change trend of the simulation curve closely aligned with that of the experiment curve, better characterizing the stress–strain relationship of the CFIT under different working conditions such as compression, tension, and shear and the error was less than 18%. The proposed approach was validated by designing a millimeter-level indentation experiment. The results in this paper demonstrate that the maximum loading depths of the simulation and experiment were consistent, and the relative errors were within 12%, respectively. The research provides a reliable elastic–plastic damage constitutive model to predict the mechanical behavior of CFITs under complex working conditions. [ABSTRACT FROM AUTHOR] more...
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- 2024
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111. Intelligent Parameter Identification for a High‐Cycle Accumulation Model of Sand With Enhancement of Cuckoo Search Algorithm.
- Author
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He, Shao‐Heng, Yin, Zhen‐Yu, Sun, Yifei, and Ding, Zhi
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OPTIMIZATION algorithms , *PARAMETER identification , *SEARCH algorithms , *MATHEMATICAL optimization , *SAND - Abstract
This study presents a novel approach of intelligent parameter identification (IPI) for a high‐cycle accumulation (HCA) model of sand, which reduces the subjective errors on manual parameter calibration and makes the use of the HCA model more accessible. The technique is based on optimization theory and adopts the cuckoo search algorithm (CSA). To improve search ability and convergence speed of CSA, several enhancements are implemented. First, the improved CSA (ICSA) incorporates quasi‐opposition learning to expand the search space and replaces the original search strategy with a Cauchy random walk to enhance global search ability. Second, an adaptive scaling factor is introduced in the algorithm's control parameters to achieve a better balance between exploration speed and accuracy. Third, a dynamic inertia weight is used to balance the search between global and local spaces when generating new nest positions after abandoning old ones. The performance of the ICSA‐based IPI approach is evaluated by comparing it with the original CSA‐based IPI and manual calibration in determining the HCA model parameters. A comprehensive analysis is also conducted to assess the effectiveness and superiority of each improvement strategy introduced in the ICSA over the original CSA. All comparisons demonstrate that the proposed ICSA‐based IPI method is more powerful and efficient in finding optimal parameters. [ABSTRACT FROM AUTHOR] more...
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- 2024
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112. Mechanism Study on the Intrinsic Damage and Microchemical Interactions of Argillaceous Siltstone Under Different Water Temperatures.
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Liang, Ning, Jin, Tao, Zhang, Jingjing, and Lu, Damin
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WEIBULL distribution ,ELASTIC modulus ,DAMAGE models ,WATER temperature ,WATER immersion - Abstract
Argillaceous siltstone is prone to deformation and softening when exposed to water, which poses a great threat to practical engineering. There are significant differences in the degrees of damage to this type of rock caused by solutions with different water temperatures. This study aimed to better understand the effect of temperature on argillaceous siltstone by designing immersion tests at water temperatures of 5, 15, 25, and 35 °C, analyzing the mechanical properties and cation concentration shifts under each condition. A water temperature–force coupled geometric damage model for argillaceous siltstone was developed, incorporating a Weibull distribution function and composite damage factors to derive a statistical damage constitutive model. The findings reveal that, with increasing water temperature, the peak strength and elastic modulus of argillaceous siltstone display a concave trend, initially decreasing and then increasing, while the cation concentration follows a convex trend, first increasing and then decreasing. Between 15 and 25 °C, the stress–strain behavior transitions from a four-phase to a five-phase pattern, with pronounced plasticity. The model's theoretical curves align closely with experimental data, with the Weibull parameters m and λ effectively capturing the rock's strength and plastic characteristics. Changes in water temperature notably influence the damage variable D
12 in the context of water temperature–peak stress coupling, with D12 initially increasing and then decreasing with higher temperatures. These research results can provide new methods for exploring the paths of soft rock disasters and provide guidance for designing defenses in geotechnical engineering. [ABSTRACT FROM AUTHOR] more...- Published
- 2024
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113. Macroscopic and Mesoscopic Damage Characteristics and Energy Evolution Laws of Rock Mass With Double Arcuate Fractures Under Uniaxial Compression.
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Ren, Qingyang, Gao, Senlin, Xiao, Songqiang, Meng, Xin, and Li, Zhongyao
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ELASTIC modulus , *GRANULAR flow , *ACOUSTIC emission , *FLOW simulations , *CRACK propagation (Fracture mechanics) - Abstract
ABSTRACT In order to reveal the influence of double arc‐shaped fissure dip angles on the macro‐micro failure and energy evolution laws of rock masses, a numerical model of red sandstone was firstly established using the PFC2D. Moreover, mesoscopic parameters of the numerical model were calibrated based on the uniaxial compression tests on intact and single straight fissure red sandstone specimens. Then, particle flow simulation tests of red sandstone with different arc‐shaped fissure dip angles were carried out. The results show that the peak strength and elastic modulus both increase with the increase of arc‐shaped fissure dip angle
α , exhibiting an oblique shear‐tensile failure pattern. Six types of cracks evolved during the instability and rupture of the rock mass with double arc‐shaped fissures. The macroscopic fissures in the rock mass ultimately penetrate along the extension direction of the arc‐shaped fissures. As the arc‐shaped fissure dip angleα increases, the crack evolution is positively correlated with the acoustic emission (AE) of the specimen. When approaching instability failure, the AE ringing count rapidly increases. There is a critical angle limit inflection point for the total energy absorbed by the rock between 60° and 75°, with a total energy increase of about 54%. During instability failure, it is dominated by dissipative energy, with elastic energy as a supplement. This article derived a damage constitutive model of red sandstone with different arc‐shaped fissure dip angles, revealing the damage laws of red sandstone under different arc‐shaped fissure dip angles. [ABSTRACT FROM AUTHOR] more...- Published
- 2024
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114. Three-dimensional multi-physics simulation and sensitivity analysis of cyclic energy storage in salt caverns.
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Honório, Hermínio T. and Hajibeygi, Hadi
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ROCK salt , *HYDROGEN storage , *CAVES , *COMPRESSED air , *UNDERGROUND storage - Abstract
Large-scale storage technologies are crucial to balance consumption and intermittent production of renewable energy systems. One of these technologies can be developed by converting the excess energy into compressed air or hydrogen, i.e., compressed gas, and storing it in underground solution-mined salt caverns. Salt caverns are proven seals towards compressed air and hydrogen. However, several challenges, including fast injection/production cycles and operation of systems of caverns, are yet to be resolved to allow for a safe scale-up of energy storage in salt caverns. To address these challenges, it is important to identify key parameters that impact both the safety and efficiency of the operations. For this purpose, the present study conducts sensitivity analyses to show the importance of different parameters on the time-dependent mechanical behavior of salt caverns, individually and in a multi-cavern system. The impact of different deformation mechanisms (e.g. transient and reverse creep), model calibration, cavern shape, presence of interlayers and multi-cavern interactions are investigated in this study. The constitutive model adopted in this work and the mathematical formulation are presented in detail. Additionally, an open-source three-dimensional simulator, named "SafeInCave", is developed for the numerical solution of the non-linear governing equations. The findings provide insights into improving the reliability of numerical simulations for the safe and efficient operation of salt caverns in energy storage applications. • A constitutive model for salt rock comprising transient, reverse, and steady-state creep is employed. • A detailed procedure for obtaining the consistent tangent matrix for the numerical formulation is presented. • Development of an open-source 3D finite element simulator for the mechanics of salt caverns. • The impact of salt rock model calibration in laboratory scale and cavern scale is analyzed. • Sensitivity analyses to different deformation mechanisms, presence of interlayers, cavern shapes and mutual interactions are performed. [ABSTRACT FROM AUTHOR] more...
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- 2024
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115. Constitutive Relationship Study of Laves Phase NbCr2/Nb Two-Phase Alloy Using Modified J-C Model and Back Propagation Neural Network Model.
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JiangFeng, Jiancong, Lu, Shiqiang, Xiao, Xuan, Wang, Kelu, and Deng, Liping
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ARTIFICIAL neural networks ,LAVES phases (Metallurgy) ,BACK propagation ,STRAIN rate ,STATISTICAL correlation - Abstract
The Laves phase NbCr
2 /Nb two-phase alloy has received significant research interest as a potential high-temperature structural material. Based on isothermal and constant strain rate compression experiments conducted on the alloy within a temperature range of 1000 -1200 °C and strain rate range of 0.001-0.1 s−1 , the flow stress constitutive relationship of the alloy was established using the J-C model and BP artificial neural network model, respectively. It was found that the conventional J-C model fails to describe the flow stress softening behavior of the alloy. In contrast, the modified J-C model provides a better prediction of the flow stress softening phenomenon and accurately characterizes the flow stress behavior of the alloy, it exhibits high prediction accuracy as indicated by the correlation coefficient (R) of 0.9902, average absolute relative error (AARE) of 8.773% and mean relative error (MRE) of 7.389%. The flow stress behavior of the alloy can be more accurately characterized using the constitutive relationship built by the BP neural network model. The model exhibits higher prediction accuracy with R of 0.9998, AARE of 2.232% and MRE of 0.870%. The results demonstrate that the BP neural network model has superior capability in predicting the flow stress behavior of the alloy. The established flow stress constitutive relationship can provide more accurate and reliable fundamental data with respect to flow stress for finite element simulations of forging deformation process of the Laves phase NbCr2 /Nb two-phase alloy. In addition, it serves as theoretical basis for rational design of forging process and accurate calculation of the deformation force of the alloy. [ABSTRACT FROM AUTHOR] more...- Published
- 2024
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116. Fractional viscoelastic constitutive modelling of real-time strain response for asphalt pavement composites subjected to simulating wheel loadings.
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Li, Xinzhou, Sha, Aimin, Song, Ruimeng, and Jiao, Wenxiu
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ASPHALT pavements , *ASPHALT testing , *ANALYTICAL solutions , *LOADING & unloading , *STATISTICAL correlation - Abstract
This paper proposed a replacement of the Kelvin–Voigt model with fractional basic elements, and the model constructed with this method was used to describe the viscoelastic strain response of asphalt pavement materials under the simulated wheel loading. Similarities between Abel element and Kelvin–Voigt model were explored, and strain response analytical solutions of Burgers and 1S1A1D models under intermittent have sine loading were derived. Then, different intermittent loading tests of asphalt binder and mixture were carried out. The results showed that both the Abel element and the Kelvin–Voigt model could represent the delayed viscoelastic behaviours accurately, and the strain response represented by them could be fully recovered during the unloading stage. Furthermore, parameters of the Abel element and Kelvin–Voigt model showed a high degree of correlation, and the 1S1A1D model exhibited the best effects for asphalt binders, particularly during the unloading period, with correlation coefficients mostly above 0.999. Moreover, when expressing the strain response of asphalt mixture under simulated wheel loading, the 1S1A1D model outperformed the Burgers model in terms of peak strain value, residual strain and changing trends. This study demonstrated that the fractional constitutive model was advantageous in representing the strain response of asphalt pavement composites. [ABSTRACT FROM AUTHOR] more...
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- 2024
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117. Mechanical Performance of Structural Polymethyl Methacrylate Joints at Different Temperatures.
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Kang, Chenxing, Peng, Lei, Li, Yantao, and Zong, Jinhui
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GLASS construction , *TENSILE tests , *STRENGTH of materials , *GLASS structure , *IMPACT strength - Abstract
This paper introduces a novel technique for enhancing the joint strength in structural acrylic glass (polymethyl methacrylate, PMMA) under thermal cycling conditions. By employing bulk polymerization, the strength of PMMA joints was significantly reinforced. Tensile assessments from 20 °C to 140 °C were conducted to evaluate the mechanical properties of acrylic joints under varying temperature conditions. A constitutive model was established to correlate the strength of both the base material and the joints with temperature variations. The tensile test outcomes demonstrated that the innovative bulk polymerization method under thermal cycling conditions effectively increased the joint material strength to reach up to 90% of the base material's strength, and the post-thermal cycling tests demonstrate that post-thermal cycling has essentially no impact on the strength and modulus. This advancement in joint strength enhancement not only expands the potential applications of acrylic glass in architectural structures but also lays a substantial theoretical foundation for construction practices. [ABSTRACT FROM AUTHOR] more...
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- 2024
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118. Research on Compression Failure Characteristics and Damage Constitutive Model of Steel Fiber-Reinforced Concrete with 2% Copper-Coated Fibers Under Impact Load.
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Liu, Guangkun, Bai, Zhengxiong, Liu, Wei, and He, Yajie
- Abstract
This study systematically investigates the mechanical properties of plain concrete (PC) and 2% steel fiber reinforced concrete (SFRC) under both static and dynamic loading conditions, utilizing advanced mechanical testing equipment and dynamic impact testing methods. The strain rate range studied spans from 10−4 s−1 to 483.12 s−1. Under static loading conditions, the maximum bearing capacity and energy absorption capacity of 2% SFRC are 2.16 times and 3.83 times greater than those of PC, respectively, indicating a significant enhancement in toughness and resistance to failure. Under dynamic loading conditions, the energy absorption capacity of SFRC increases to 6.36 times that of PC. The impact failure behavior of SFRC was analyzed using the split-Hopkinson pressure bar—digital image correlation (SHPB-DIC) method, revealing that the failure was primarily driven by splitting tension. The failure process was subsequently categorized into four distinct stages. At high strain rates, the dynamic enhancement factor, peak stress, and peak strain of SFRC exhibit a linear increase with strain rate, whereas the energy absorption capacity increases in a nonlinear manner. This study presents a simplified viscoelastic constitutive model with four parameters and develops a damage-based viscoelastic constitutive model with seven parameters, demonstrating its broad applicability. The findings offer both theoretical insights and experimental evidence to support the use of SFRC under high strain rate conditions. [ABSTRACT FROM AUTHOR] more...
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- 2024
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119. A thermo-mechanical model for saturated and unsaturated soil–structure interfaces.
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Cui, Sheqiang and Zhou, Chao
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TEMPERATURE effect , *INTERFACE structures , *SHEAR strength , *SHEARING force , *CRITICAL temperature - Abstract
Shear behaviour of soil–structure interfaces greatly affects the performance of geotechnical structures. The soil–structure interfaces in geothermal structures (e.g., energy pile and energy wall) are often subjected to varying temperature and suction conditions. However, there is no constitutive model to simulate the coupled effects of suction and temperature on the shear behaviour of soil–structure interfaces. In this study, a thermo-mechanical model was newly developed based on the bounding surface plasticity framework to predict the thermo-mechanical behaviour of saturated and unsaturated interfaces. A power function was used to calculate the degree of saturation at the interface and improve the evaluation of suction effects on interface shear strength. A linear relationship between temperature and interface critical state friction angle was proposed to incorporate thermal effects. New equations were also proposed to describe the critical state lines (CSLs) in the void ratio versus stress plane (e- ln σ n * ) and to model the shearing-induced deformation at various temperatures and suctions. The experimental data from different interfaces in the literature were used to evaluate the model capability. Comparisons between measured and computed results suggest that this model can well capture the coupled effects of temperature, suction, and net normal stress on the shear behaviour of interfaces. [ABSTRACT FROM AUTHOR] more...
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- 2024
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120. Constitutive Model of Uniaxial Compression for Rock (Coal) and Bursting Liability Index Based on the Structure Ensemble Dynamics Theory.
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Chen, Shuai, Tang, Jupeng, and Pan, Yishan
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ROCK bursts , *COAL mining , *DIMENSIONAL analysis , *ROCK properties , *ROCK analysis , *MATERIALS compression testing - Abstract
The bursting liability is very important to evaluate the risk of rock burst in coal mine. Conducting uniaxial compression test is the main method to study the bursting liability of rock (coal). To establish an accurate uniaxial constitutive model, the structure ensemble dynamics theory is adopted. The model of rock (coal) specimen compression by testing machine is simplified. Through dimensional analysis, the stress–strain relationship of the specimen is a power model. The mechanical properties of rock (coal) vary with different levels of deformation and can be divided into four stages. The different states can be considered as different ensembles. By using the analysis method of structural ensembles dynamics, one formula completely represents the four stages accurately. The parameters in the formula are physically meaningful and can be uniquely determined based on experimental data. A criterion for instability criterion of the system of the specimen and the testing machine is derived, and a theoretical explanation of instability failure related to uniaxial compressive strength is given. Parameters sensitivity analysis and verification are conducted on the theoretical results. The theoretical results are highly accurate and can effectively reflect the stress–strain relationship of rock (coal) under uniaxial compression. A bursting liability index which contains the information of the peak and post-peak of the stress–strain relationship is proposed. The new index is positively correlated with the compressive strength and the bursting energy index and a classification of bursting liability levels for the new index was determined based on them. Highlights: The structure ensemble dynamics theory is used to establish a constitutive model. One formula completely represents the stress-stain relationship accurately. The parameters are physically meaningful and can be uniquely determined. A theoretical explanation of instability failure related to strength is given. A new bursting liability index based on the new constitutive model is proposed. [ABSTRACT FROM AUTHOR] more...
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- 2024
- Full Text
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121. Shear constitutive model for various shear behaviors of landslide slip zone soil.
- Author
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Zou, Zongxing, Luo, Yinfeng, Tao, Yu, Wang, Jinge, and Duan, Haojie
- Subjects
- *
SHEAR (Mechanics) , *WEIBULL distribution , *SOILS , *GORGES , *LANDSLIDES , *PLASTICS - Abstract
Soil constitutive models are widely investigated and applied in soil mechanical behaviors simulation; however, the damage evolution process of soil with various shear deformation behaviors was rarely studied. This study introduces a novel shear constitutive model for slip zone soil considering its damage evolution process. Firstly, an innovative method for determining the shear stiffness is proposed to assess the damage degree of slip zone soil during shear deformation. Further, a damage evolution model based on the log-logistic function is derived to characterize the damage evolution process of slip zone soil, and a new shear constitutive model based on the damage evolution process is subsequently proposed. Both the damage evolution model and the shear constitutive model are verified by the ring shear test data of the slip zone soil from the Outang landslide in the Three Gorges Reservoir area of China. Compared to the traditional peak-solving constitutive model based on the Weibull distribution, the proposed shear constitutive model has the distinct advantage of describing not only the brittle (strain softening) mechanical behavior but also the ductile and plastic hardening mechanical behavior of soil. In summary, this method offers a rapid determination of the damage evolution process and the shear behavior constitutive relationship of slip zone soil in landslides. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
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122. Evaluation of Soil–Structure Interface Models Considering Cyclic Loading Effect.
- Author
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Wang, Hai‐Lin, Yin, Zhen‐Yu, Gu, Xiao‐Qiang, and Jin, Yin‐Fu
- Subjects
- *
CYCLIC loads , *MODULUS of rigidity , *DISPLACEMENT (Psychology) , *GEOTECHNICAL engineering , *CRITICAL theory - Abstract
The simulation of the soil–structure interface (SSI) under cyclic loading is critically important in geotechnical engineering. Numerous studies have been conducted to explore the cyclic behaviors exhibited at the SSI. However, existing model evaluations primarily rely on direct comparisons between experiments and simulations, with limited analysis focused on specific behaviors like accumulated normal displacement and stress degradation under cyclic loading. This study proposes and adapts six SSI models, including three nonlinear incremental models and three elastoplastic models. These models incorporate nonlinear shear modulus, critical state theory, and particle breakage effects to enhance their capability to capture SSI behaviors. Utilizing optimization‐based calibration for a fair comparison, the model parameters are fine‐tuned based on the experimental data. Comprehensive assessments including global comparisons and specific behaviors like accumulated normal displacement and stress degradation are carried out to evaluate the models' performance. The results indicate that all models effectively replicate the typical behaviors of SSI systems. By incorporating the particle breakage effect, the models can represent both the reversible and irreversible normal displacements under cyclic loading with better performance. The irreversible normal displacement remains stable and is solely influenced by the soil properties rather than the stress level. Moreover, the models successfully capture the stress degradation under constant normal stiffness caused by the irreversible normal displacement. [ABSTRACT FROM AUTHOR] more...
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- 2024
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123. Study of the Bond Performance between GFRP Bar Reinforcement and Seawater–Sea Sand–Coral Concrete.
- Author
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Wang, Chao, Sun, Li, Zhang, Chunwei, Li, Chuang, Qiao, Pizhong, and Chen, Xingyi
- Subjects
- *
BOND strengths , *CHEMICAL bond lengths , *FAILURE mode & effects analysis , *MARINE engineering , *REINFORCING bars - Abstract
The world has abundant marine resources, and the use of seawater, sea sand, and coral instead of seawater, river sand, and gravel can compensate for the lack of traditional building materials for marine engineering construction. Additionally, glass fiber–reinforced polymers (GFRPs) have excellent corrosion resistance and can effectively solve the corrosion problem of steel reinforcement in harsh environments. The bond performance between GFRP bars and sea sand–coral concrete (SSCC) is an important factor in deciding whether this approach can be applied in actual projects such as RC. In this study, the effects of the SSCC strength grade, diameter, bond length, and rib height on the bond performance between GFRP bars and SSCC were investigated using direct pullout tests. The bond performance between GFRP bars and SSCC was compared with that between GFRP bars and ordinary concrete (OC). Furthermore, the microstructure and damage characteristics of the GFRP bars and SSCC were observed using scanning electron microscopy (SEM). The test results show that the main failure modes of the specimens include GFRP bar pullout failure and SSCC splitting failure. The rib height has a greater effect on the bond performance, and in specimens with a strength grade of SSCC25, diameter of 12 mm, and bond length of 5d , the bond strength between a deep-ribbed GFRP bar and the SSCC was 75.6% greater than that of specimens with a shallow-ribbed GFRP bar. The bond strength between the GFRP bars and SSCC decreased with increasing diameter and bond length, but the bond stiffness was almost the same. When the diameter increased from 8 to 14 mm, the bond length increased from 3d to 7d , and the bond strength decreased by 57.3% and 36.9% respectively. The bond strength and bond stiffness increased with increasing strength grade of the SSCC. Moreover, SEM showed that the surface damage of GFRP bars with pullout failure was severe, whereas the surface integrity of GFRP bars with splitting failure specimens was better. Based on the experimental results, the bond–slip constitutive model of the GFRP bar with SSCC yielded satisfactory results. [ABSTRACT FROM AUTHOR] more...
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- 2024
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124. Hysteresis constitutive model of C/SiC composites considering probabilistic matrix fragmentations.
- Author
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Li, Longbiao
- Subjects
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STOCHASTIC matrices , *DEBONDING , *HYSTERESIS , *LOADING & unloading , *MATRICES (Mathematics) , *HYSTERESIS loop - Abstract
In this paper, a new micromechanical hysteresis loop constitutive model of C/SiC composites with different interphases was developed considering the probabilistic‐statistical matrix fragmentation process. The lengths of matrix fragmentation were divided into three types, that is, long matrix fragments (LMFs), medium matrix fragments (MMFs), and short matrix fragments (SMFs). The distributions of the LMFs, MMFs, and SMFs with increasing tensile stress were determined using the probabilistic‐stochastic model by assuming the two‐parameter matrix strength distribution. The micro stress field of the LMFs, MMFs, and SMFs upon unloading and reloading was obtained and adopted to determine the corresponding stress‐strain relations. The interaction of matrix fragmentation lengths, especially for the LMFs with large debonding energy (LDE) and SMFs, was considered in the closed‐form constitutive model and hysteresis‐based inverse tangent modulus (ITMs) damage parameter. Synergistic effects of the fiber volumes, peak stresses, and interface debonding energy on the interface damage state, mechanical hysteresis loops, and related ITMs with small debonding energy and LDE were also analyzed. Comparisons of the mechanical hysteresis loops using the new hysteresis models considering matrix stochastic fragmentation and hysteresis models considering constant matrix fragmentation were also discussed. Experimental cyclic tensile hysteresis loops and unloading/reloading ITMs of C/(PyC)/SiC and C/(PyC+SiC)/SiC composites with different interphase thickness (i.e., t = 300, 600, 1000, and 2000 nm) were predicted using the developed constitutive model. Evolution of the unloading/reloading interface slip ratio was analyzed for different tensile peak stresses. [ABSTRACT FROM AUTHOR] more...
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- 2024
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125. 提前终止累加误差函数粒子群算法应用研究.
- Author
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康恒一
- Abstract
Copyright of Geotechnical Engineering Technique is the property of Geotechnical Engineering Technique Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) more...
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- 2024
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- View/download PDF
126. USS122G超高强度不锈钢热变形行为及热加工图.
- Author
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谢帅, 何峰, and 施文鹏
- Subjects
ISOTHERMAL compression ,STRAIN rate ,STRAINS & stresses (Mechanics) ,STAINLESS steel ,HOT working - Abstract
Copyright of Foundry Technology (1000-8365) is the property of Foundry Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) more...
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- 2024
- Full Text
- View/download PDF
127. 考虑应变率变化的岩石变形统计 损伤模拟适用性分析.
- Author
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张超, 朱东平, 杨楚卿, 颜桢炜, and 夏真荣
- Abstract
Copyright of Chinese Journal of Applied Mechanics is the property of Chinese Journal of Applied Mechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) more...
- Published
- 2024
- Full Text
- View/download PDF
128. Numerical and Constitutive Analysis of Granular Column Collapse Experiments Under Reduced-Gravity Conditions.
- Author
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Yang, Sen, Cheng, Xiaohui, and Hou, Meiying
- Abstract
The research on granular column collapse under various gravity levels is of great significance for the study of granular rheology and its applications in reduced-gravity space engineering. We firstly reviewed a rare experimental investigation that observed a gravity-related run-out distance of the granular column collapse in this paper. To identify the origin of the gravity-related run-out distance, a unified constitutive model was used to simulate the behavior of granular materials in these experiments based on a large deformation numerical method, the smoothed particle hydrodynamics (SPH). The parameters of this constitutive model were also discussed. Numerical simulations can reproduce the run-out distances that positively correlate with the gravity level, above 0.03 g in particular. Based on the numerical and constitutive analysis, this gravity-related runout distance is attributed to the combined influence of gravity-induced pressure and shear strain rate levels on granular flow. [ABSTRACT FROM AUTHOR] more...
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- 2024
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- View/download PDF
129. Finite Element Simulation of Ti-6Al-4V Alloy Machining with a Grain-Size-Dependent Constitutive Model Considering the Ploughing Effect Under MQL and Cryogenic Conditions.
- Author
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Chen, Guang, Wu, Zhuoyang, Caudill, James, and Jawahir, I. S.
- Subjects
CRYOGENIC liquids ,GRAIN refinement ,MATERIAL plasticity ,DEFORMATION of surfaces ,FINITE element method - Abstract
The finite element modeling method has been widely applied in the modeling of the cutting process to characterize the instantaneous and microscale deformation mechanism that was difficult to obtain using physical experiments. The lubrication and cooling conditions, such as minimum quantity lubrication and cryogenic liquid nitrogen, affect the thermo-mechanical behaviors and machined surface integrity in the cutting process. In this work, a grain-size-dependent constitutive model was used to model orthogonal cutting for Ti-6Al-4V alloy with MQL and LN
2 conditions. The cutting forces and chip morphologies that were measured in the cutting experiments of Ti-6Al-4V alloy were used to validate the simulated forces. The relative errors between the measured and simulated principal forces were less than 8%, while the relative errors of thrust forces were less than 19%. The predicted chip morphologies and surface grain refinement agreed well with the experimental results under the conditions with different uncut chip thicknesses and edge radii. Additionally, the relationship between the plastic displacement and grain refinement, as well as the microhardness and residual stresses under MQL and cryogenic conditions, were discussed. This work provides an effective modeling method for the orthogonal cutting of Ti-6Al-4V alloy to understand the mechanism of the plastic deformation and machined surface integrity under the MQL and LN2 conditions. [ABSTRACT FROM AUTHOR] more...- Published
- 2024
- Full Text
- View/download PDF
130. Deformation Characteristics and Mechanical Constitutive Model of Coal Under Stress Wave Action.
- Author
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Gu, Zhoujie, Shen, Rongxi, Zhang, Siqing, Zhou, Xin, Liu, Zhentang, Zhao, Enlai, Wang, Xiulei, and Jia, Jianbin
- Subjects
HEAD waves ,COAL sampling ,LATERAL loads ,DEFORMATIONS (Mechanics) ,ENERGY consumption - Abstract
The three-dimensional (3D) stress waves of coal samples were studied using a true triaxial split Hopkinson pressure bar compression rod. The results indicate that the 3D strain of the coal samples increased gradually under vibration load. The 3D stress wave of coal samples showed attenuation characteristics, and the change amplitude of the stress wave of coal samples along the direction of dynamic load was the most obvious. The amplitude of stress wave was the largest in the axial direction constrained by pre-stressing 3 MPa, while the amplitude of stress wave in the lateral 2 MPa pre-stressing was smaller than that under the constraint of 1 MPa. The results showed that the main deformation of coal samples was along the impact direction, while the larger horizontal and vertical lateral binding forces limited the deformation of coal samples. The Fourier transform was performed on the 3D stress wave of the coal samples, and the change in the amplitude of the stress wave spectrum was correlated positively with the vibration. The spectrum amplitude of the coal samples under the pre-stressed 3 MPa constraint (axial) direction was the largest, while the spectrum amplitude of the coal samples under the lateral 2 MPa pre-stressed constraint was smaller than that under the binding 1 MPa. However, the main frequency of the three-way stress wave was distributed in 0–10 kHz. By calculating the energy consumption rate and wave velocity decay rate, it was verified that the damage of coal samples increased with increase in dynamic load. This experimental testing provides an effective testing method for studying the 3D stress waves of coal samples under complex stress medium conditions. In addition, a dynamic constitutive model of coal was constructed according to the mechanical behavior of coal and rock mass and the measured data. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
- View/download PDF
131. 冲击压缩下 PlatSil® Gel 硅胶材料动态力学特性数值模拟.
- Author
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李 爽, 蒲 伟, 张 圩, 刘亚雷, and 刘 坤
- Abstract
Copyright of Ordnance Industry Automation is the property of Editorial Board for Ordnance Industry Automation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) more...
- Published
- 2024
- Full Text
- View/download PDF
132. Constitutive model of high-temperature rapid fracture of Si3N4 ceramics for engine turbine discs and their pore insensitivity parameters.
- Author
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Peng, JS, Li, FY, Ma, SJ, Dong, XH, and Zhang, XP
- Subjects
FINITE element method ,FRACTURE toughness ,COMPUTED tomography ,INFORMATION measurement ,CERAMICS - Abstract
The metallic materials used to manufacture turbine components can potentially be replaced with ceramics such as Si
3 N4 , but the stress on turbine discs is difficult to determine experimentally, which hinders the development and optimization of ceramics. The finite element method solves this problem, but it requires an accurate constitutive model and parameters. Existing methods for determining model parameters lack versatility and do not consider the internal pores of ceramics. This work proposes a method for determining the parameters of the high-temperature rapid fracture constitutive model of ceramics with internal pores based on the results of industrial computed tomography (CT) and high-temperature fracture toughness experiments. The constitutive model for a ceramic with internal pores was selected based on the typical service conditions of turbine discs. Industrial CT was used to measure pore information. A finite element preprocessor was developed to create simulated specimens with pores. The high-temperature fracture toughness of the ceramics was measured. Pore insensitivity was the parameter obtained from the high-temperature constitutive model of ceramics with pores using this method. The maximum relative error between the predicted and experimental flexural strengths was 6.8%. It provides a new idea for determining the parameters of constitutive models for materials with pores. [ABSTRACT FROM AUTHOR] more...- Published
- 2024
- Full Text
- View/download PDF
133. Effect of Gd Addition on Hot Deformation Behavior and Microstructure Evolution of 7075 Aluminum Alloy.
- Author
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Li, Yajie, Fan, Xuran, Qin, Fengming, Zhao, Xiaodong, and Cao, Kefan
- Abstract
In order to clarify the effect of rare earth Gd on the microstructure evolution and deformation behavior of 7075 aluminum alloy during hot compression, uniaxial compression tests of Al-Zn-Mg-Cu-0.5%Gd were conducted at strain rates of 0.001, 0.01, 0.1, and 1 s
−1 with the temperatures ranging from 350 to 450 °C. The microstructural evolution during deformation was characterized using optical microscopy and electron backscatter diffraction (EBSD) techniques. The experimental results indicate that the addition of the rare earth element Gd significantly increases the peak flow stress and thermal activation energy of the alloy. Due to the pinning effect of rare earth phases, dislocation movement is hindered, leading to an increased level of work hardening in the alloy. However, the dynamic recrystallization of the alloy is complicated. At a high Z (Zener-Hollomon parameter) values, recrystallization occurs in the form of DDRX (Discontinuous Dynamic Recrystallization), making it easier to nucleate at grain boundaries. As the Z value decreases gradually, the recrystallization mechanism transitions from discontinuous dynamic recrystallization (DDRX) to continuous dynamic recrystallization (CDRX). At a low Z values with the strain rate of 0.001 s−1 , the inhibitory effect of rare earths weakens, resulting in a comparable recrystallization ratio between Al-Zn-Mg-Cu-Gd alloy and 7075 aluminum alloy. Moreover, the average grain size of the aluminum alloy with Gd addition is only half that of 7075 aluminum. The addition of Gd provides Orowan and substructure strengthening for the alloy, which greatly improves the work-hardening of the alloy compared with 7075 aluminum alloy and improves the strength of the alloy. [ABSTRACT FROM AUTHOR] more...- Published
- 2024
- Full Text
- View/download PDF
134. Characterization of the mechanical behavior and constitutive modeling of sandstone under acidic dry-wet cycles and dynamic loading.
- Author
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Yuan, Pu, Zheng, Xiaobo, Wei, Ningning, and Li, Aobo
- Abstract
We investigate herein the role of acidic dry-wet cycles and dynamic loading on the mechanical stability of sandstone, which is crucial for managing closed and abandoned mines' safety. Using a split Hopkinson pressure bar, we conducted dynamic compression tests on sandstone samples exposed to four acidic conditions (pH = 3, 5, 6.5, 7) and five dry-wet cycle frequencies (1, 5, 10, 20, 30) at an impact pressure of 0.70 MPa. Our findings reveal that the dynamic stress-strain response of sandstone entails compacting, elastic, plastic, and failure phases, with peak stress and elasticity decreasing as the acidity and cycle frequency increase. Analytical techniques, including EDS, XRD, and NMR, showed changes in composition and porosity, indicating reduced deterioration compared to untreated stone. Based on Weibull distribution and damage mechanics, a dynamic damage constitutive model was developed to accurately predict the sandstone's behavior under these conditions. This model, validated by experimental data, effectively captures the dynamic stress-strain characteristics of sandstone, indicating the importance of understanding environmental degradation effects on rock stability in mining contexts. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
- View/download PDF
135. Effect of pile-head breaking methods on the triaxial creep behavior of a concrete: a constitutive modeling approach.
- Author
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Wu, Haikuan, Zhang, Hangqi, Kang, Shun, Zhang, Xin, Yang, Yongyi, Yang, Xudong, Shen, Rongxi, Liu, Baoxian, Yuan, Xun, and Shu, Zhile
- Abstract
This study investigated the long-term creep behavior of concrete in drilled shafts using conventional and soft-cutting head techniques, focusing on their propensity for internal defects and crack propagation under sustained loading. Triaxial creep tests were performed on concrete specimens subjected to multistage loading to examine the axial- and radial-creep responses associated with each cutting-head method. The findings reveal that concrete prepared with conventional cutting heads exhibits a higher susceptibility to creep failure, attributed to an increased presence of internal defects. In contrast, specimens using soft-cutting heads demonstrated reduced axial- and radial-creep deformations. Concrete cured in laboratory conditions and those cut with soft-cutting heads at various elevations predominantly experienced shearing failures, whereas specimens with soft-cutting heads positioned at higher elevations were more prone to radial tension-shear failures. Considering the Burgers model and fractional-order theory, we introduce a one-dimensional nonlinear damage creep model, alongside a more comprehensive three-dimensional damage creep model. Validation of these models confirms their effectiveness in describing the creep behavior of concrete under different cutting-head disturbances. Importantly, our analysis suggests that the role of soft-cutting head methods on the integrity of cast-in-place concrete piles is comparatively minimal. This insight underscores the potential for optimizing pile-head breaking techniques to mitigate creep-related failures in concrete structures. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
- View/download PDF
136. Characterization and modeling of the uniaxial thermo-mechanical compressive behavior of polymethacrylimide (PMI) foam at different temperatures.
- Author
-
Chen, Guotao, Lv, Yansong, Mei, Zhiyuan, Li, Huadong, and Bai, Xuefei
- Abstract
This paper investigates the uniaxial compressive failure behavior of polymethacrylimide (PMI) foam across a range of temperatures (20 °C–200 °C), at both macro- and microscales. The investigation includes dynamic mechanical analysis and dimensional stability tests to evaluate the material's heat resistance. The stress–strain curve of PMI foam under varying compressive failure mechanisms was analyzed, utilizing the Liu–Subhash model for accurate prediction of the material's stress–strain constitutive relationship at different temperatures. The results indicate that between 20 °C and 180 °C, PMI foam behaves as an elastoplastic material, displaying a "three-stage" pattern in its stress–strain curve. At 200 °C, the material transitions to a hyperelastic incompressible state, evidenced by a "two-stage" stress–strain pattern. The paper also determines how temperature affects yield strength and elastic modulus, as well as the influence of strain rate at different temperatures. A quasi-static compression constitutive model for PMI foam, considering temperature effects, was modified from the Liu–Subhash model. These findings offer crucial theoretical support and data for understanding the thermo-mechanical bearing mechanism in composite sandwich structures. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
- View/download PDF
137. Study on the Damage Behavior of Engineered Cementitious Composites: Experiment, Theory, and Numerical Implementation.
- Author
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Ding, Tingting, Wang, Zhuo, Liu, Yang, Wang, Xinlong, Sun, Tingxin, and Yang, Shengyou
- Subjects
CEMENT composites ,ENGINEERING models ,REQUIREMENTS engineering ,STRUCTURAL engineering ,CIVIL engineering - Abstract
The ever-increasing material performance requirements in modern engineering structures have thrust engineered cementitious composites (ECCs) into the limelight of civil engineering research. The exceptional tensile, bending, and crack-control abilities of ECCs have sparked significant interest. However, the current research on the mechanical behavior of ECCs primarily focuses on uniaxial tensile and compressive constitutive relationships, leaving a gap in the form of a comprehensive multidimensional constitutive model that can fully describe its complex behavior at large strains. This study rigorously addresses this gap by initially investigating the uniaxial tensile and compressive behavior of ECCs through experiments and establishing a one-dimensional constitutive relationship of ECCs. It then introduces the concepts of damage energy release rate and energy equivalent strain, and constructs a three-dimensional constitutive model of ECCs by introducing the damage variable function. We write the numerical algorithm of our theoretical model in terms of the VUMAT subroutine and implement it into ABAQUS 2019 finite element software. We validate the accuracy and practicality of the multidimensional constitutive model by comparing the experimental data of uniaxial tension/compression and four-point bending. This paper enriches the theoretical system of ECCs and provides rigorous guidance for the performance optimization and practical application of such advanced engineering materials. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
- View/download PDF
138. MS‐IS Hypoplastic Model Considering Stiffness Degradation Under Cyclic Loading Conditions.
- Author
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Wani, Sahil, Alipour, Mohammad Javad, Kandasami, Ramesh Kannan, and Wu, Wei
- Subjects
- *
CYCLIC loads , *LOADING & unloading , *SAND , *MEMORY , *FORECASTING - Abstract
ABSTRACT Modelling the cyclic response of granular materials is key in the design of several geostructures. Over the years, numerous constitutive models have been proposed to predict the cyclic behaviour of granular materials. However, pertaining to the hypoplastic constitutive models, one of the significant limitations is their inability to accurately predict the geomechanical response during the unloading and reloading phases. This study introduces an extension of the MS‐IS hypoplastic model designed to enhance the predictions during non‐monotonic loading conditions. Addressing the limitations observed in the hypoplastic models during the unloading and reloading phases, the proposed model incorporates an additional stiffness feature. This new stiffness function is integrated into the foundational framework to enhance the model's overall stiffness response. For the unloading phase, the introduction of a stiffness degradation factor aims to modify the volumetric response and account for the realistic stiffness degradation. Additionally, for the reloading phase, stiffness is now a function of the mean effective stress. The novel model's performance is validated against experimental data, encompassing diverse loading and boundary conditions. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
- View/download PDF
139. Progressive damage for 3D printed composites with variable fiber volume content and ply location.
- Author
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Meng, Zhe, Yali, Yang, Lu, Lei, Chen, Hao, Xu, Sha, Li, Yongfang, Zhang, Ruoping, and Zhou, Tianjun
- Subjects
FIBROUS composites ,DAMAGE models ,CARBON fibers ,TENSILE tests ,THREE-dimensional printing - Abstract
At present, 3D printed continuous carbon fiber reinforced composites (CCFRCs) are widely used in aviation and automotive fields. Most of the existing research on 3D printed CCFRCs focuses on fiber volume content and rarely explores the specific fiber ply location. However, the latter is one of the most important factors affecting the strength and stiffness properties of materials. In this paper, the constitutive model and progressive damage model of 3D printed CCFRCs are established, concentrating on the fundamental aspects of fiber volume content and fiber ply location. The mechanical properties of 3D printed CCFRCs with different fiber volume content and fiber ply location were studied by tensile tests. The mapping relationship between mechanical properties and fiber volume content and fiber ply location was obtained based on experimental data. In addition, the failure morphology and microstructure of the sample at the fracture section were analyzed, and the failure process under different fiber angles was studied to reveal the failure mechanism. The progressive damage model was used to predict and analyze the performance of 3D printed CCFRCs with different fiber volume content and fiber ply location. The results show that the feasibility and effectiveness of the present model are verified through the comparison between experiment and simulation. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
- View/download PDF
140. Characterization of Long‐Term Municipal Solid Waste Constitutive Behavior With Coupled Biodegradation and Fibrous Reinforcing Effects.
- Author
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Li, Xiulei, Yang, Chunwei, Zhang, Yuchen, Li, Yuping, Shi, Jianyong, and Sun, Yanan
- Subjects
- *
STRAINS & stresses (Mechanics) , *STRAIN hardening , *SHEAR strain , *SOLID waste , *SHEAR strength - Abstract
ABSTRACT To appropriately simulate the long‐term mechanical behavior of municipal solid waste (MSW), a constitutive model coupling the effects of biodegradation and fibrous reinforcement was developed. In the proposed model, the compressive deformation due to biodegradation was regarded as being caused by an additional equivalent stress. Considering the effect of biodegradation, an evolution equation of the equivalent stress was proposed, and a plastic volumetric strain hardening law was developed. A fibrous reinforcement parameter was introduced, which was associated with the fiber content, stress state, and plastic shear strain of MSW. A plastic shear strain hardening law was developed to model the fibrous reinforcement. Based on the associated flow rule and two plastic strain hardening laws, the proposed model was established. The proposed model well simulated the hardening properties of MSW, as evidenced by the stress‒strain curves and the consistent, nonlinear increase in volumetric strain with axial strain. The differences in the shear strength and volumetric deformation due to the confining stress and fiber content were also well simulated by the model. Furthermore, the model predictions accurately reflected the findings of experiments conducted over a period of 10 years. Finally, parametric investigations were used to calibrate this proposed model, which can well characterize the long‐term MSW mechanical behavior. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
- View/download PDF
141. Experimental Study on Mechanical Properties of Artificial Cores Saturated With Ice: An Analogical Simulation to Natural Gas Hydrate Bearing Sediments.
- Author
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Shen, Kaixiang, Xie, Wenwei, Yu, Yanjiang, Wang, Yingsheng, Wang, Zizhen, Wang, Xiaokang, and Zhang, Wensheng
- Subjects
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GAS hydrates , *SAND , *INTERNAL friction , *GAS-lubricated bearings , *TENSILE tests - Abstract
This work takes the natural gas hydrate (NGH) reservoir in the Shenhu area at the South China Sea as the target. Using the quartz sand, calcite grains, and illite powder as the main mineral composites, and Portland cement as the bonding material, the host skeleton with similar porosity and mechanical properties to the target reservoir were prepared. Ice was used to simulate natural gas hydrates for their high similarity in mechanical properties and distributions within porous host. The ice saturation in the host skeleton is quantitatively controlled by the quality method. As an analogical simulation, artificial samples with different ice saturations were tested by uniaxial compression measurements and the Brazilian tensile tests, aiming to reveal the mechanical behavior of NGH sediments. The results indicated that the plasticity of the artificial sample increases and its damage form transitions from brittleness to ductility as the ice saturation increases. The effects of free water and ice on the strength of saturated samples are quite different. The free water tends to reduce the strength of the sample due to illite hydration and change of internal friction. The bonding effect of ice tends to increase the strength of the sample, while the ice could also reduce the internal friction. When the ice saturation is larger than 30%, the compressive and tensile strengths of the sample increase with ice saturation, which could be regressed as yc = 2.2628S + 0.8322, and yt = 0.411S + 0.0273, respectively. The constitutive model was developed based on the equivalent medium theory and the D‐P criterion, which could describe the experiment data well with deviations less than 10%. [ABSTRACT FROM AUTHOR] more...
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- 2024
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142. Dynamic Mechanical Properties and Constitutive Modeling of Polyurethane Microporous Elastomers.
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Liu, Huiming, Xiao, Youcai, Zou, Yu, Han, Yong, Fan, Chenyang, and Sun, Yi
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STRAINS & stresses (Mechanics) , *POLYURETHANE elastomers , *ENERGY function , *STRAIN energy , *DENSITY - Abstract
The present study fabricated samples of polyurethane elastomers (PUEs) with three distinct densities and assessed their mechanical responses using split Hopkinson pressure bar (SHPB) tests. The findings reveal a significant increase in PUE stress with increasing strain rate and density. To further investigate the influence of strain rate sensitivity on PUEs, a strain rate sensitivity coefficient was employed to quantify the impact of strain rate on the mechanical properties of PUEs. Separate quantifications were performed for collapse stress, plateau stress, and densification strain as indicators of the strain rate sensitivity coefficient. The results demonstrate that the collapse stress sensitivity coefficient was notably affected by the applied strain rate. Additionally, both collapse and plateau stresses exhibited an increase with increasing density, which could be described by a power function relationship. Based on the theory of strain energy function, a constitutive model considering density and strain rate effects was developed to describe the stress–strain behavior of PUEs under various densities and strain rates. A comparison between this constitutive relationship and experimental results showed good agreement, highlighting its potential in describing dynamic mechanical behavior. [ABSTRACT FROM AUTHOR] more...
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- 2024
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143. Mechanical property deterioration and a full-stage constitutive model of shale subject to water-softening effect.
- Author
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Bian, Kang, Chen, Yanan, Zhang, Wei, Xiong, Qingrong, and Li, Bingyang
- Abstract
Water-softening effect has been widely recognized as one of the primary causes triggering large deformation and failure in soft-rock engineering; however, there is still a lack of a full-stage constitutive model for rock considering the water-softening effect and non-linear deformation characteristics at the compaction stage under triaxial stress conditions at present. In this paper, laboratory tests are firstly carried out to estimate the deterioration characteristics of mechanical properties with increase of saturation coefficient for shale samples. And then, a full-stage constitutive model of shale subjected to water-softening effect is proposed, which consists of the pre-yield and the post-yield constitutive relationships. The pre-yield constitutive relationships could well describe the non-linear deformation characteristics of compaction stage, which are derived based on the generalized Hooke’s law considering water-softening effect under anisotropic stress conditions. On the other hand, by introducing correction coefficients to solve the problem of numerical discontinuity at the yield point of the pre-yield and the post-yield constitutive relationships, the post-yield constitutive relationships are derived on the basis of the statistical damage mechanics theory. The comparison results with the experimental data show that the proposed model could well characterize the full-stage stress–strain relationship for shale under triaxial loading considering the water-softening effect. [ABSTRACT FROM AUTHOR] more...
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- 2024
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144. A thermodynamic based constitutive model considering the mutual influence of multiple physical fields.
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Wang, Zhen, Zhou, Zi-yu, Wu, Ming, and Zhu, Zhen-de
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STRAIN rate , *THERMODYNAMIC potentials , *LOW temperatures , *HIGH temperatures , *ELASTOPLASTICITY - Abstract
In multiple physical fields, the mutual influence among these fields can significantly impact material elastoplasticity. This paper proposes a thermodynamic-based constitutive model that incorporates the mutual influence of multiple physical fields. Rather than treating physical field characteristics as adjustable "parameters" affecting material coefficients, the proposed model employs a thermodynamic dissipation potential derived from the Onsager reciprocity relations, accounting for thermodynamic forces coupling. This dissipation potential ensures that the thermodynamic flow in the stress field is influenced by both stress field and other physical fields thermodynamic forces, which describes the plastic flow under multiple physical fields, while preserving thermodynamic duality. The paper begins with the formulation of a generalized thermodynamic model applicable to diverse materials and types of coupled fields, which is then degraded to a specific model for AA5182-O AlMg alloy under the influence of temperature and strain rate fields coupling. Given the universal applicability of the generalized model, such degradation provides a structured approach framework for developing thermodynamics-based constitutive models. For different materials encountered in practical engineering, new thermodynamic forces can be introduced to describe their unique mechanical properties while preserving the overarching thermodynamics-based model framework, thereby facilitating model scalability. The paper concludes with a validation example, showing that within the Portevin-Le Chatelie (PLC) regime, the plastic flow stress of AA5182-O AlMg alloy decreases with increasing strain rate at low temperatures but increases at high temperatures. The accurate simulation of these distinct strain rate effects crucially relies on integrating the mutual influence of temperature field and strain rate field. [ABSTRACT FROM AUTHOR] more...
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- 2024
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145. The role of breakage-dependent critical state lines in constitutive modelling of sand under axisymmetric drained and undrained loads: A comparative study.
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Shu, Shuang, Yan, Chen, Zhao, Wei, and Sun, Yifei
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STRAINS & stresses (Mechanics) , *COMPARATIVE studies - Abstract
Particle breakage usually takes place within sand when subjected to external loading, which changes the critical state line (CSL) and stress-strain behavior of sand. To consider such effect, different expressions for the CSL with consideration of particle breakage have been proposed, which can be sorted in two categories: (i) CSL through explicit incorporation of particle breakage ratio into the e – ln p′ relation, (ii) CSL through implicitly empirical correlation, e.g., e – p′0.7 and e – exp(p′ζ) relations. However, limited studies were made on comparing the performances of these expressions. This study inspects the efficiency of three representative CSLs from categories i and ii, for SANISAND modelling of sand. It was found that all the CSLs can capture the constitutive responses of sands under axisymmetric drained and undrained loads, to some extent. However, e – p′0.7 and e – exp(p′ζ) relations are comparatively simple and share an equivalently accurate performance at low to medium high pressures, whereas e – exp(p′ζ) relation works the best among others at high pressures. To more highlight the physical role of particle breakage, the CSL in category i can be suggested. Otherwise, the CSLs in category ii are recommended in modelling practices, because of the comparatively succinct expressions and less model parameters. [ABSTRACT FROM AUTHOR] more...
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- 2024
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146. Damage Properties and Rheological Model of Spatial-Rotation Fissured Red Sandstone Subjected to Freeze–Thaw and Loading.
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Li, Yongqi and Huang, Da
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FRACTURE mechanics , *DIGITAL image correlation , *RHEOLOGY , *FROST heaving , *ROCK creep - Abstract
The occurrence of preset flaws can influence the mechanical, physical, and other related properties of rock samples. To study the failure characteristics and crack growth of rock samples containing spatial-rotation (SR) fissures subjected to freeze–thaw (FT) cycles and loading, laboratory tests of SR fissured red sandstone under various factors were conducted. The frost heave pressure, creep deformation, P-wave velocity and damage variable of SR fissured rocks were monitored and analysed. Failure processes and 3D fracture patterns of the specimen were studied in great detail using Digital Image Correlation (DIC) and Acoustic Emission (AE) technologies. Based on the experimental results, a damage constitutive model of the SR fissured rocks under the freeze–thaw and loading (FT-L) was explored. The results revealed that the frost heave pressure can be classified into five types: hibernation, growth, eruption-stabilization, fluctuation, and dissipation. In addition, with the increase of initial damage and temperature (absolute value), the corresponding wave and creep curves increase gradually. Under the coupling of FT cycle and load at each stage, the damage variable exhibited a U-shaped change trend, and gradually increases with the increase of load level. It is worth noting that, the fracture pattern of rock bridge can be classified into three fundamental types (progressive, undulating and opening fracture). A new nonlinear damage constitutive model containing the Nishihara model and a rheological element was established in which the coupling model can characterize the whole creep process of SR fissured red sandstone under the combined action of FT cycles and creep loading. Thus, the proposed model is a very good tool for the analysis of load coupling problems involved in the slope of cold area. Highlights: The compression tests of spatial-rotation fissured sandstone under the freeze–thaw and loading were carried out. The progressive damage process of sandstone with a spatial-rotation fissure was given. The 3D fracture patterns containing rock bridge extension and fissure penetration were revealed. A damage rheological model that considers the temperature and load was established. [ABSTRACT FROM AUTHOR] more...
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- 2024
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147. Pore Tensor-Based Constitutive Model of Deep Coral Reef Limestone at High Loading Rates.
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Wu, Kai, Meng, Qingshan, Luo, Le, Liu, Haifeng, Shu, Siqi, Wang, Chi, and Shen, Tianli
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CORAL reefs & islands , *ARTIFICIAL neural networks , *COMPUTED tomography , *STRAINS & stresses (Mechanics) , *POROSITY - Abstract
The buried diagenesis and dolomitization in the deep stratum of coral reef island enable the Coral reef limestone (CRL) to exhibit a significant distinction compared with the calcified coral skeleton in mechanical properties. This paper utilized the Split Hopkinson Pressure Bar and X-ray computed tomography to investigatethe dynamic mechanical characteristics of deep CRL, revealing the effect of free water on stress–strain behaviors and the energy evolution law of CRL under high-rate impact. Furthermore, the concept of pore tensor proposed in our previous investigation was introduced to modify the dynamic constitutive model. The results indicate that the dynamic compressive strength (DCS) of CRL specimens is strongly related to stress rate, whereas the dynamic elastic modulus and DCS are independent of strain rate. The peak strains of dry specimens are significantly greater than those of saturated ones at comparative loading rates, and the viscosity effect of free water at a high loading rate impedes the deformation of CRL specimens. Moreover, the energy absorption efficiency of CRL is significantly higher than that of Bohus granite and Solnhofen limestone. Dry specimens have higher energy absorption efficiency under the same energy input, but the dynamic increase factor (DIF) of saturated specimens is larger under the same energy absorption efficiency. For the determination of DIF, this paper adopted the Back Propagation Neural Network model trained by pore tensor to predict the quasi-static compressive strength of CRL specimens, which solved the problem of considerable discreteness in mechanical parameters of CRL. The critical transition value of input energy proportion that the DIF increases rapidly is about 30%. In addition, the constitutive model modified by pore tensor reflects the influence of pore structure and water content of CRL specimens, and well describes the characteristics of dynamic elastic modulus and peak strain of deep CRL independent of loading rate. Highlights: Dynamic compressive strength of coral reef limestone strongly correlates with stress rate and weakly correlates with strain rate. The machine learning-based method for predicting quasi-static strength improves the determination accuracy of dynamic increase factor of coral reef limestone. The critical transition value of input energy proportion that the dynamic increase factor increases rapidly is about 30%. The modified constitutive model reflects the effects of pore structure and water content of coral framework limestone. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
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148. Effects of shield construction on dynamic characteristics and deformation of interlayer soil: A case study in Changchun, China.
- Author
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Jiang, Boyu, Wei, Haibin, Wei, Dongsheng, Ma, Zipeng, and Wang, Fuyu
- Abstract
Shield tunneling can cause deformation of the interlayer soil. Traditional static methods do not consider the shield dynamic load and the construction influence on the dynamic performance of interlayer soil, resulting in inaccurate results. Therefore, this paper proposes a dynamic analysis method to assess soil deformation. Firstly, the composition and stress state of interlayer soil were monitored on site. Secondly, the dynamic triaxial tests were conducted based on the monitoring results to analyze the soil dynamic characteristics. Then, a dynamic constitutive model of the interlayer soil was constructed, which considers the change of the dynamic performance. Finally, the dynamic effect of shield on soil is simulated based on viscoelastic mechanics, and the dynamic analysis of interlayer soil deformation is realized by three-dimensional finite element method. The results indicate that the interlayer soil near the excavation face is more significantly affected during the crossing stage. Shield construction increases the dynamic strength and dynamic modulus of the interlayer soil, while reducing the damping ratio. The Hardin-Drnevich model and the logarithmic-linear model can well describe the evolution laws of dynamic modulus and dynamic strength. The dynamic analysis method is closer to real construction and has higher prediction accuracy. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
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149. Plastic damage fracture characteristics and constitutive modeling of rocks under uniaxial compression considering crack geometry.
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Xu, Hongtao, Qi, Tingye, Feng, Guorui, Qiu, Tian, Wang, Haochen, Wang, Linfei, Zhang, Zhicheng, and Cheng, Siyuan
- Subjects
- *
WEIBULL distribution , *DAMAGE models , *COMPRESSIVE strength , *CRACK propagation (Fracture mechanics) , *GEOMETRIC modeling - Abstract
The study of damage and failure in fractured rock masses is crucial. This study employs the representative volume element (RVE) method to develop a microscale rock model. The model simulates the propagation and rupture of fractures by integrating factors including actual mineralogical composition, the Weibull distribution function, the Mohr–Coulomb damage criterion, and strain softening. Results indicate that fractures reduce the uniaxial compressive strength of the rock and that peak strength is significantly correlated with crack geometries. Plastic damage in rocks was categorized into three stages: elastic, rapid growth, and postpeak softening. A logistic growth model describes the plastic volume change curves for rocks with various fracture geometries, establishing the relationship between plastic damage volume and damage variables. Constitutive models for rocks with varying fracture geometries under uniaxial compression were formulated. The accuracy and applicability of these models were validated, providing a theoretical basis for rock engineering applications. Highlights: A heterogeneous plastic damage model based on representative volume elements is developed.A logistic growth model was used to describe the plastic volume change curves for rocks containing different fracture geometries.The relationship between rock plastic damage volume and damage variables was established.Plastic damage constitutive models of rocks containing different fracture geometries under uniaxial compression were obtained and validated. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
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150. Low-Temperature Mechanical Properties of AA 6063-T6 and 7075-T6: Tests and Full-Range Constitutive Models.
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Xi, Rong, Xie, Jian, and Yan, Jia-Bao
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TENSILE tests , *ALUMINUM alloys , *LOW temperatures , *FRACTURE strength , *STORAGE tanks - Abstract
Aluminum alloys (AAs) are potential alternative constructional materials for low-temperature infrastructures in cold regions and liquefied natural gas (LNG) storage tanks. This study investigated the mechanical properties of AA 6063-T6/7075-T6 materials through tension tests on 32 AA coupons at low temperatures ranging from 20°C to −165°C. All the AA 6063-T6 coupons exhibited ductile failure modes, and AA 7075-T6 coupons failed in brittle modes at 20°C to −165°C. The experimental results showed that decreasing the temperature from 20°C to −165°C , respectively, increased the yield, ultimate, and fracture strengths of AA 6063-T6 (or 7075-T6) by 26.8% (8.5%), 21.2% (6.5%), and 27.6% (9.7%), but their ductility was not compromised. Furthermore, regression analyses were performed to establish prediction equations for the low-temperature mechanical indexes of AAs. Finally, a full-range constitutive model was proposed to estimate the stress–strain behaviors of AA 6063-T6 and 7075-T6. The validation results confirmed that the proposed constitutive models accurately described the stress–strain behaviors of AA 6063-T6 and 7075-T6 within the temperature range of 20°C to −165°C. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
- Full Text
- View/download PDF
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