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Skin tissue is a kind of complex biological material abundant with fibers. A new constitutive model, relating macroscopic responses with microstructural fiber configuration alteration, is developed to investigate the stress softening behaviors of skin tissue observed during cyclic loading–unloading tests. Two influential factors are introduced to describe the impact of fiber configuration change and stretch-induced damage. The present model achieves good agreement between predicted stress distribution of human skin and corresponding ex vivo experimental data obtained from the literature, affirming its capability to effectively capture the characteristic softening behaviors of human skin under cyclic loading conditions. [ABSTRACT FROM AUTHOR]

Since dielectric elastomers (DEs) exhibit obvious nonlinear visco-hyperelasticity, and remarkable temperature dependence, it is difficult to accurately predict the cyclic deformation of DEs at various temperatures. To address this issue, an improved visco-hyperelastic constitutive model is proposed here to reproduce the complex temperature-dependent cyclic deformation of DEs. In the improved model, the Ogden model is chosen to provide the strain energy density representing the hyper-elastic response, a nonlinear viscosity evolution equation is used to depict the strong viscosity of DEs, and specific temperature-dependent parameters are incorporated to describe the cyclic deformation of DEs at various temperatures. Finally, the prediction capability of the proposed visco-hyperelastic model is validated by reproducing the cyclic deformation of VHB 4910 DE observed in experiments at different temperatures. This study provides a theoretical basis for the rational design of DE devices. [ABSTRACT FROM AUTHOR]

Throughout the entire operational lifespan of a solid rocket motor, the propellant grain experiences creep due to gravitational forces, potentially influencing the motor′s reliability. To enhance the efficiency of creep tests for solid propellants, short‐term (3000 seconds) creep tests were conducted on nitrate ester plasticized polyether (NEPE) propellant at stress levels of 0.15 MPa, 0.20 MPa, 0.25 MPa, and 0.30 MPa using both the step stress method (SSM) and the conventional constant creep test (CCT). Furthermore, mid‐term (10000 seconds) and long‐term (7 days) creep tests were conducted. Based on the traditional generalized Kelvin model, the Saint‐Venant body was incorporated to derive a visco‐elastic‐plastic model with overstress considered, and constitutive model parameters were determined through data fitting. The findings demonstrate the efficacy of the constitutive model in well characterizing propellant creep behavior. According to the model, the yield stress of NEPE propellant was determined to be 0.2302 MPa, representing a significant 64.03% reduction compared to its design strength. This insight holds relevance for structural integrity analysis and the evaluation of solid motor storage life. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Explosives & Propellants is the property of Chinese Journal of Explosives & Propellants 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.)

Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute 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.)

In order to study the evolution law of uniaxial compression damage and its characterization method, three kinds of rocks with different lithology that commonly exist in coal measure rock were taken as the research objects to explore the relationship between their mineral composition, microstructure and mechanical properties, and the feasibility of acoustic emission (AE) characteristic parameters and AE spatial location to characterize the evolution process of uniaxial compression damage of rocks was compared and analyzed. A damage constitutive model based on AE cumulative ringing count was established and verified by numerical simulation. The results show that the differences in the micromorphology and mineral composition of coal measures with different lithology directly affect their physical and mechanical properties and load damage characteristics. AE characteristic ringing count can effectively represent the damage evolution process of rock during loading. Based on rock porosity characteristics and AE cumulative ringing count during loading, a constitutive model considering initial damage and cumulative damage was established. The theoretical analysis results of the damage constitutive model are in good agreement with the results of laboratory experiments and numerical simulation, which can be used to analyze the damage process of coal measure rock under load. [ABSTRACT FROM AUTHOR]

This study investigates the uniaxial tensile behavior of high-strength engineered cementitious composites (HS-ECCs) in sulfate erosion environments. Five different sulfate erosion ages were established (0 days, 30 days, 60 days, 90 days, and 120 days), and the development of the macro-mechanical properties of HS-ECCs was revealed from a microscopic perspective using scanning electron microscopy (SEM). The results indicate that, under the influence of sulfate erosion, the strength of HS-ECCs exhibits a trend of initial increase followed by a decrease, while ductility shows a continuous decline. This phenomenon is primarily attributed to changes in the microstructure and reaction products. Based on the test results, an aging growth factor was introduced to fit the stress–strain curve, demonstrating that the model can effectively predict the tensile performance of HS-ECCs with greater accuracy compared to traditional models. This study not only provides data references for the engineering application of HS-ECCs in sulfate environments but also offers a novel approach for constructing predictive models in other environmental contexts. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology 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.)

Copyright of Journal of the Chinese Society of Rare Earths is the property of Editorial Department of Journal of the Chinese Society of Rare Earths 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.)

Coatings are essential for protecting steel structures from corrosion and mechanical stresses, especially under challenging environmental conditions. To this end, this study systematically examines the effects of temperature (−20 °C to 50 °C), strain rate (6.67 × 10−4 s−1 to 1.67 × 10−2 s−1), and intermediate coat thickness (140 μm to 700 μm, the layer between the primer and topcoat) on the uniaxial tensile properties of heavy-duty coatings for steel structures. Experimental and theoretical analyses were conducted to quantitatively assess the influence of these factors on the mechanical properties of the coatings. A multifactor constitutive model was developed based on the Sherwood–Frost model by integrating material characteristics and fitting experimental data, incorporating response functions for temperature, strain rate, and intermediate coat thickness. The results reveal that increased temperature causes temperature-induced softening, while higher strain rates lead to strain rate-dependent strengthening of the coatings. In contrast, the effect of layer thickness on mechanical properties follows a non-monotonic trend, influenced by the structural and material characteristics of the coatings, with the most significant mechanical response occurring at 560 μm thickness. These findings suggest that optimal coating design must consider multiple factors to enhance mechanical performance. Additionally, the correlation coefficients (r) between the model predictions and experimental results are 0.97 or higher, indicating the model's effectiveness in predicting and optimizing the mechanical performance of heavy-duty coatings under complex conditions. [ABSTRACT FROM AUTHOR]

The structural performance of shield segments plays an important role in the safety and normal service of shield tunnel construction, so it is necessary to study and understand the mechanical performance of shield segments in detail. At present, the main test methods for the bearing capacity of shield segment structure are prototype segment test method and more economical symmetrical inclined beam test method. In order to study the relationship between the bearing performance of shield segments obtained by symmetrical Inclined Beams and the bearing performance of actual prototype segments, based on the cohesion model, considering the friction between concrete joints and the normal separation of reinforcement concrete interface, the constitutive models of potential fracture surface of concrete and steel reinforced concrete interface were established respectively. A numerical analysis model for the whole process of fracture damage of reinforced concrete structures suitable for the analysis of the bearing capacity of shield segments is proposed, and the model was verified based on the existing prototype tests of shield segments. Finally, based on the typical segment used in Fuzhou Metro Binhai Express, the relationship between the bearing capacity of the segment obtained from the prototype segment test and the symmetrical inclined beam test was analyzed by using the established model, and the results are analyzed and evaluated. [ABSTRACT FROM AUTHOR]

Highlights Composites are undergoing extensive research and utilization due to their excellent mechanical properties, driven by human needs. Traditionally, the research methods in materials science predominantly rely on empirical theory or experimental trial and error approaches. However, the increased complexity of composite materials results in a greater intricacy in their mechanical behavior. Consequently, the utilization of traditional research methods may not achieve sufficient efficiency. Materials science is rapidly transitioning into a data‐driven era, with machine learning (ML) emerging as a potent tool to expedite materials development and enhance properties prediction. Significant advancements have been achieved in the application of ML to the study of composite mechanics. In this review article, we elucidate various ML methods employed in the construction of constitutive models for isotropic and anisotropic composites, and delve into the research on construction ML models that leverage input data derived from composite processes, structures, and environmental conditions to predict material mechanical properties. Additionally, we summarize recent noteworthy ML applications in composite design and optimization. Finally, possible prospective viewpoints are proposed for future development, with the aim of providing essential scientific guidance for advancing material science and technology through ML. Machine learning can address complexity in constitutive model of the anisotropic composites. Machine learning predicts mechanical properties of composites well by process and structure. Machine learning enhances efficiency in inverse design to optimize composites. Limitations, challenges, development trends of ML in composites. [ABSTRACT FROM AUTHOR]

Ethylene-propylene-diene monomer (EPDM) is a key engineering material; its mechanical characterization is important for the safe use of the material. In this paper, the coupled effects of thermal degradation temperature and time on the tensile mechanical behavior of EPDM rubber were investigated. The tensile stress-strain curves of the aged and unaged EPDM rubber show strong nonlinearity, demonstrating especially rapid stiffening as the strain increases under small deformation. The popular Mooney–Rivlin and Ogden (N = 3) models were chosen to fit the test data, and the results indicate that neither of the classical models can accurately describe the tensile mechanical behavior of this rubber. Six hyperelastic constitutive models, which are excellent for rubber with highly nonlinearity, were employed, and their abilities to reproduce the stress-strain curve of the unaged EPDM were assessed. Finally, the Davis–De–Thomas model was found to be an appropriate hyperelastic model for EPDM rubber. A Dakin-type kinetic relationship was employed to describe the relationships between the model parameters and aging temperature and time, and, combined with the Arrhenius law, a thermal aging constitutive model for EPDM rubber was established. The ability of the proposed model was checked by independent testing data. In the moderate strain range of 200%, the errors remained below 10%. The maximum errors of the prediction results at 85 °C for 4 days and 100 °C for 2 and 4 days were computed to be 17.06%, 17.51% and 19.77%, respectively. This work develops a theoretical approach to predicting the mechanical behavior of rubber material that has suffered thermal aging; this approach is helpful in determining the safe long-term use of the material. [ABSTRACT FROM AUTHOR]

This paper proposes a new thermodynamically consistent anisotropic continuum damage mechanics model that the degradation of material is described by a set of damage variables. We adopt a set of novel equivalent strains which are functions of both the strain and the damage state variables as well. A viscous stabilization method is considered to improve the convergence during the material softening. The evolution of damage state variables is updated through a Newton-Raphson iterative process. The expression of the consistent tangent stiffness matrix is also derived. A smoothed exponential damage evolution shape function with rescaling regularization method is proposed to describe the material softening process and the mesh dependency phenomenon is relieved. Several sets of numerical examples including three-point-bending of a notched beam, uniaxial tension of unnotched and notched plate of composite material with multiple layups are presented to verify the anisotropic damage models. [ABSTRACT FROM AUTHOR]

The continuous softening behavior of the brain tissue, i.e., the softening in the primary loading path with an increase in deformation, is modeled in this work as a state of hyperelasticity up to the onset of failure. That is, the softening behavior is captured via a core hyperelastic model without the addition of damage variables and/or functions. Examples of the application of the model will be provided to extant datasets of uniaxial tension and simple shear deformations, demonstrating the capability of the model to capture the whole-range deformation of the brain tissue specimens, including their softening behavior. Quantitative and qualitative comparisons with other models within the brain biomechanics literature will also be presented, showing the clear advantages of the current approach. The application of the model is then extended to capturing the rate-dependent softening behavior of the tissue by allowing the parameters of the core hyperelastic model to evolve, i.e., vary, with the deformation rate. It is shown that the model captures the rate-dependent and softening behaviors of the specimens favorably and also predicts the behavior at other rates. These results offer a clear set of advantages in favor of the considered modeling approach here for capturing the quasi-static and rate-dependent mechanical properties of the brain tissue, including its softening behavior, over the existing models in the literature, which at best may purport to capture only a reduced set of the foregoing behaviors, and with ill-posed effects. [ABSTRACT FROM AUTHOR]

BACKGROUND: As a new intelligent polymer material, shape memory polymer (SMP) was a potential orthodontic appliance material. OBJECTIVE: This study aimed to investigate the thermodynamic responses of SMP under different loads via finite element analysis (FEA). METHODS: FEA specimens with a specification of 0.1 × 0.1 × 1 mm were designed. One end of the specimen was fixed, and the other was subjected to displacement load. Different loading, cooling, and heating rates were separately exerted on the specimen in its shape recovery process and used to observe the responses of the SMP constitutive model. Furthermore, specimens with various tensile elongation and sectional areas were simulated and used to elucidate their effect on shape recovering force. RESULTS: The specimens obtained a similar stress of 0.5, 0.44, and 1.07 Mpa for different loading, cooling, and heating rates after a long time. The shape recovering force of specimen increased from 0.0102 to 0.0315 N when the elongation improved from 10% to 40% and to 0.0408 N when the sectional areas were expanded to 0.2 × 0.2 mm. CONCLUSION: The stiffness of SMP was small at a high temperature but large at a low temperature. The effects of the loading, cooling, and heating rates on SMP can be eliminated after a long time. Furthermore, it was possible to increase the recovering force by increasing the elongation or expanding the sectional area of the specimen. The force was quadratically dependent on the elongation ratio. [ABSTRACT FROM AUTHOR]

The accuracy of the constitutive model affects the precision of the finite element analysis. Four advanced sand constitutive models—the DM04 model, the SANISAND-MS model with memory surface (MS), the SANISAND-Sf model with semi-fluidized state (Sf), and the SANISAND-MSf model with both memory surface and semi-fluidized state—are examined in this article based on a comparison of simulation and experiment results of element tests. First, four constitutive models are implemented in OpenSees, and the constitutive models are calibrated based on the cyclic loading experiments of Karlsruhe fine sand. After that, the advantages and disadvantages of four constitutive models under different test conditions are analyzed. Finally, the finite element model of the LEAP-UCD-2017 (Liquefaction Experiments and Analysis Project, University of California Davis, 2017) centrifuge test is established to evaluate the performance of the four constitutive models for solving boundary value problems. It is found that the SANISAND-MSf model can well reproduce the undrained cyclic properties. [ABSTRACT FROM AUTHOR]

A precise Johnson-Cook (J–C) constitutive model is the foundation for precise calculation of finite-element simulation. In order to obtain the J–C constitutive model accurately for a new cast and forged alloy GH4198, an inverse identification of J–C constitutive model was proposed based on a genetic–particle swarm algorithm. Firstly, a quasi-static tensile test at different strain rates was conducted to determine the initial yield strength A, strain hardening coefficient B, and work hardening exponent n for the material's J–C model. Secondly, a new method for orthogonal cutting model was constructed based on the unequal division shear theory and considering the influence of tool edge radius. In order to obtain the strain-rate strengthening coefficient C and thermal softening coefficient m, an orthogonal cutting experiment was conducted. Finally, in order to validate the precision of the constitutive model, an orthogonal cutting thermo-mechanical coupling simulation model was established. Meanwhile, the sensitivity of J–C constitutive model parameters on simulation results was analyzed. The results indicate that the parameter m significantly affects chip morphology, and that the parameter C has a notable impact on the cutting force. This study addressed the issue of missing constitutive parameters for GH4198 and provided a theoretical reference for the optimization and identification of constitutive models for other aerospace materials. [ABSTRACT FROM AUTHOR]

Metals manufactured by selective laser melting (SLM) with different directions exhibit different mechanical properties. This study conducted dynamic and static mechanical tests using a universal testing machine and split-Hopkinson bar (SHPB). The mechanical properties of 18Ni300 with 0° and 90° build directions manufactured by SLM were compared, and the micro-structure properties of the two build directions were analysed by metallographic tests. The Johnson–Cook (J-C) constitutive model was fitted according to the experimental results, and the obtained constitutive parameters were verified by numerical simulations. The results revealed that the constitutive model could predict the mechanical properties of 18Ni300 in a dynamic state. The build direction had little influence on the mechanical properties in a static state, but there was a significant difference in the dynamic state. The difference in the dynamic compressive yield strength of the 18Ni300 material manufactured by SLM with two build directions was 9.8%. The SLM process can be improved to produce 18Ni300 with uniform mechanical properties by studying the reasons for this difference. [ABSTRACT FROM AUTHOR]

The mechanical properties of granular soils are significantly influenced by stress paths and particle breakage. In this study, a four-modulus incremental nonlinear model that incorporates the effects of the stress path and particle breakage was established based on an analysis of triaxial compression test results conducted on calcareous sands subjected to varying stress paths. A mathematical expression for this model and the process of determining its parameters was proposed. Subsequently, the model was experimentally verified. Our findings revealed that the isotropic compression consolidation volumetric strain modulus exhibited a curvilinear relationship with the average effective principal stress, whereas it demonstrated a linear correlation with the relative breakage index. Furthermore, a four-parameter nonlinear model was constructed, integrating the dilatancy equation to consider stress path effects and establishing a functional relationship between the stress ratio and shear strain. By comparing the experimental results with the calculated results for calcareous sands and rockfill materials, the model effectively simulated the stress ratio-axial strain behavior of granular soils under different stress paths. However, it failed to fully capture the volumetric strain-axial strain characteristics of granular soils after reaching the peak stress ratio. Therefore, further research is necessary to develop a more comprehensive correction method for incremental nonlinear models. [ABSTRACT FROM AUTHOR]

The water sensitivity and structural characteristics of collapsible loess are two typical factors that significantly influence its mechanical behaviors. This paper presents a simple and practical elastic-plastic model based on the modified Cam-Clay model to well capture the essential behavior of unsaturated intact loess. The model employs deviator stress and spheric stress as the stress variables, with the water content serving as the moisture variable. The critical state surface of the model can be determined by utilizing the shear strength parameters of unsaturated soil under axisymmetric stress conditions. An initial yield surface equation is established by incorporating structural strength into the elliptical yield surface equation, which is used to determine the starting point for elastic-plastic deformation calculations under different humidity and stress combinations. The model comprises several parameters, each of which has a clear physical interpretation and can be conveniently obtained through conventional triaxial tests. The validity of the model for unsaturated intact loess is confirmed through a comparison with the stress–strain relationship of unsaturated intact loess in the axisymmetric stress state. This work has the potential to significantly enhance our ability to predict and mitigate potential geotechnical disasters, such as foundation deformation under axisymmetric conditions and slope stability problems under non-axisymmetric conditions. Ultimately, the application of this model could contribute to the safety and stability of infrastructure and construction projects in loess regions. [ABSTRACT FROM AUTHOR]

Brittle to ductile transition with the increase of confining pressure is a common behavior of porous geomaterial. In the present work, a micromechanics-based multiscale constitutive model is constructed to describe the macroscopic mechanical behavior of porous chalk. At the microscopic scale, the Drucker–Prager criterion is adopted to describe the plastic behavior of the solid matrix with dissymmetric responses between tensile and compressive loading. Based on the macroscopic yield criterion derived in Shen et al. (Int J Plast 126:102609, 2020), an effective damage parameter is introduced and then a complete multiscale constitutive model is constructed and implemented with a plastic hardening law and a macroscopic plastic potential to describe the overall mechanical behavior of porous geomaterial. Through the evolution of microstructure of the studied porous materials, the proposed micromechanics-based multiscale model well describes the transition from brittle behavior to ductile one with the increase of confining pressure. The proposed constitutive model is then applied to porous chalk and validated by the comparisons between its numerical predictions and experimental results under different confining pressures. The main features of porous materials are captured by the proposed model which improves significantly the phenomenological ones. Highlights: A novel elastoplastic damage constitutive model is established for porous material. The model considered explicitly the effects of porosity and matrix properties. The brittle-ductile transition in porous material is well taken into account. The variation of material microstructure during the loading is considered. The new model is general and can be applied to a large range of geomaterials [ABSTRACT FROM AUTHOR]

Thermomechanical coupling effects, which are almost inevitable in materials processing, are particularly notable in NiTi shape memory alloy (SMA). Understanding the dynamic mechanical properties of NiTi SMA at high temperatures and high strain rates is important to reveal its cutting mechanism. In the present work, the split Hopkinson pressure bar experiments under different temperatures and strain rates are carried out. The dynamic mechanical behaviors are discussed from both macro- and microperspectives. The results indicate that nonlinear deformation behaviors of Ni50.8Ti SMA strongly depended on strain rates and temperatures. The influence mechanisms of temperature and strain rate on the nonlinear deformation of Ni50.8Ti SMA are clarified in detail. Moreover, a constitutive model for nonlinear deformation of Ni50.8Ti SMA is established to depict the dynamic characteristics. This is helpful to study the thermomechanical effects on the Ni50.8Ti SMA during machining. [ABSTRACT FROM AUTHOR]

Understanding the behavior of weak rock masses is important for predicting the stability of structures under different loading conditions. Traditional models such as the generalized Hoek–Brown and Coulomb weak plane are widely used; however, they often fail to capture the nonlinear and irreversible behavior of weak rock masses. This study offers a comprehensive overview of a critical analysis of constitutive models' strengths and limitations for simulating weak rock masses. By comparing traditional and advanced novel approaches such as the strength degradation of rock (SDR) masses and continuous damage mechanics (CDM), this investigation shows that the new advanced methods significantly enhance the quality and accuracy of simulations. Moreover, SDR models address the limitations of classical plasticity models by incorporating nonlinear stress paths and irreversible stress changes, while CDM offers detailed insights into microstructural defect progression. These advancements allow for more accurate and practical predictions of long-term stability in geomechanical engineering tailored to specific requirements of each project. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Southeast University / Dongnan Daxue Xuebao is the property of Journal of Southeast University 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.)

To ensure the long-term safety and stability of bridge pile foundations in permafrost regions, it is necessary to investigate the rheological effects on the pile tip and pile side bearing capacities. The creep characteristics of the pile-frozen soil interface are critical for determining the long-term stability of permafrost pile foundations. This study utilized a self-developed large stress-controlled shear apparatus to investigate the shear creep characteristics of the frozen silt-concrete interface, and examined the influence of freezing temperatures (−1, −2, and −5°C), contact surface roughness (0, 0.60, 0.75, and 1.15 mm), normal stress (50, 100, and 150 kPa), and shear stress on the creep characteristics of the contact surface. By incorporating the contact surface's creep behavior and development trends, we established a creep constitutive model for the frozen silt-concrete interface based on the Nishihara model, introducing nonlinear elements and a damage factor. The results revealed significant creep effects on the frozen silt-concrete interface under constant load, with creep displacement at approximately 2–15 times the instantaneous displacement and a failure creep displacement ranging from 6 to 8 mm. Under different experimental conditions, the creep characteristics of the frozen silt-concrete interface varied. A larger roughness, lower freezing temperatures, and higher normal stresses resulted in a longer sample attenuation creep time, a lower steady-state creep rate, higher long-term creep strength, and stronger creep stability. Building upon the Nishihara model, we considered the influence of shear stress and time on the viscoelastic viscosity coefficient and introduced a damage factor to the viscoplasticity. The improved model effectively described the entire creep process of the frozen silt-concrete interface. The results provide theoretical support for the interaction between pile and soil in permafrost regions. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society 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.)

Copyright of Iron Steel Vanadium Titanium is the property of Iron Steel Vanadium Titanium 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.)

Copyright of Journal of Central South University is the property of Springer Nature 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.)

To minimize the impact on nearby structures during deep excavations, choosing an appropriate soil constitutive model for analysis holds significant importance. This study aims to conduct a comparative analysis of various constitutive soil models—namely, the Mohr–Coulomb (MC) model, the hardening soil (HS) model, the hardening soil small strain (HSS) model, and the soft soil (SS) model—to identify the most suitable model for the lacustrine deposit. To implement these models, the soil's index properties and mechanical behavior were evaluated from undisturbed soil samples. The numerical simulation and verification of these properties were carried out by comparing the laboratory test results with the outcome of the finite element method; the most suitable constitutive soil model for the soil was identified as the HSS model. Upon analyzing the wall deflection and ground settlement profiles obtained from respective constitutive models, it was observed that the HS and HSS models exhibit similar characteristics and are well-suited for analyzing typical lacustrine soil. In contrast, the MC and SS models yield overly optimistic results with lower wall deflection and ground settlement and fail to predict realistic soil behavior. As a result, this research highlights the significance of selecting the appropriate constitutive soil model and refining the parameters. This optimization process contributes significantly to the design of support systems, enhancing construction efficiency and ensuring overall safety in deep excavation projects. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department 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.)

Bond performance served as a crucial foundation for the collaboration between concrete and steel rebar. This study investigated the bond performance between coal gasification slag (CGS) concrete, an environmentally friendly construction material, and steel rebar. The effects of fine aggregate type, steel rebar diameter, and anchorage length on bond performance were examined through bond-slip tests conducted on 16 groups of reinforced concrete specimens with different parameters. By utilizing experimental data, a formula for the bond strength between steel rebar and CGS concrete was derived. Additionally, the BPE bond-slip constitutive model was modified by introducing a correction factor (k) to account for relative protective layer thickness. Findings indicated that substituting 25% of manufactured sand with coal gasification slag did not cause significant adverse effects on concrete strength or bond stress between concrete and steel rebar. The effect of steel rebar diameter on the ultimate bond stress was not obvious, whereas when the steel rebar diameter was fixed; the increase in anchorage length led to uneven distribution of bond stress and eventually reduced the ultimate bond stress. The modified bond-slip constitutive model agreed well with the experimental values and was able to more accurately reflect the bond-slip performance between CGS concrete and steel rebar. This study provided a theoretical basis for the conversion of CGS into a resource and for the application of CGS concrete. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology 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.)

This paper examines the mechanical behavior of fiber reinforced polymer (FRP)-confined concrete under cyclic compression using the 3D cohesive zone model (CZM). A numerical modeling method was developed, employing zero-thickness cohesive elements to represent the stress-displacement relationship of concrete potential fracture surfaces and FRP-concrete interfaces. Additionally, mixed-mode damage plastic constitutive models were proposed for the concrete potential fracture surfaces and FRP-concrete interface, considering interfacial friction. Furthermore, an anisotropic plastic constitutive model was developed for the FRP composite jacket. The CZM model proposed in this study was validated using experimental data from plain concrete and large rupture strain (LRS) FRP-confined concrete subjected to cyclic compression. The simulation results demonstrate that the proposed model accurately predicts the mechanical response of both concrete and FRP-confined concrete under cyclic compression. Lastly, various parametric studies were conducted to investigate the internal failure mechanism of FRP-confined concrete under cyclic loading to analyze the influence of the inner friction plasticity of different components. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering 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.)

Isothermal compressive experiments on a Ni-based superalloy were performed at strain rates from 0.001 to 1 s-1 and temperatures between 920 and 1040 to study its high--temperature deformation. Utilizing the experimental data, a Long Short-Term Memory (LSTM) model, optimized with the Particle Swarm Optimization (PSO) algorithm (LSTM--PSO), was developed to characterize this behavior. The LSTM component of the model effectively handles the complexity and nonlinear characteristics of time-series data, while the PSO component performs parameter optimization, enhancing the model's accuracy and generalization capability. The model's inputs include deformation temperature, strain rate, and true strain, with true stress as the output. A comparison of experimental and forecasted results revealed that the LSTM-PSO model accurately predicts high-temperature deformation, achieving a correction coefficient of 0.9988 and an average absolute relative error of 1.16, demonstrating superior performance compared to other advanced methods. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the impact of various ambient temperatures on the mechanical properties of full aeolian sand concrete (ASC100). Using ordinary concrete (ASC0) as the control group, we analyzed the effects of different ambient temperatures (−20, −15, −10, −5, 0, and 20°C) on the mechanical properties of both ASC0 and ASC100 through cube compression, splitting tensile, and uniaxial compression tests. The results demonstrate that the compressive strength and splitting tensile strength of concrete cubes increased with decreasing temperature. At −20°C, the compressive strength of ASC100 increased by 30.1% and that of ASC0 increased by 27.31% compared to that at 20°C. Additionally, compared to normal temperatures, the elastic modulus of ASC0 and ASC100 at subzero temperatures increased by 28.2–61.4% and 6.8–65.7%, respectively, while the peak stress increased by 7–35% and 6.8–38%, respectively. The stress–strain curve of ASC100 showed three stages: elastic, elastic-plastic, and yield failure, serving as the reference group. Finally, based on the classical constitutive model, we modified the constitutive parameters by axial compressive strength and temperature, proposing a constitutive model of concrete suitable for different low-temperature environments, which is in good agreement with experimental data.

Polytetrafluoroethylene(PTFE)has the advantages of high and low temperature resistance,chemical corrosion resistance and high thermal stability,and has become an indispensable sealing material in the industrial field.Its compression performance is crucial to the safe service of the sealing structure.By carrying out the compression experiments and compression creep experiments on PTFE,the compression properties of PTFE at different temperatures were studied,and the coupling effect of stress and temperature on creep behavior was explored.The results show that the compressive yield strength and compressive modulus of PTFE decrease with the increase of temperature.The compression creep performance is influenced by the coupling of temperature and stress.At the same temperature,the instantaneous strain and creep rate of PTFE increase with the increase of stress.Under the same stress,as the temperature increases,the compressive modulus decreases,the molecular energy and free volume increase,resulting in an increase in the instantaneous strain and creep of PTFE,and an increase in the total strain.Finally,the Burgers model,Findley model,and Time-Hardening model were used to analyze the creep behavior of PTFE under different loading conditions.It was found that the Burgers model and Findley model can better describe the creep behavior of PTFE at different temperatures.This study can provide theoretical guidance and data support for the design and engineering application of sealing structures that consider the compressive creep performance of PTFE.

The complex mechanical and damage mechanisms of rocks are intricately tied to their diverse mineral compositions and the formation of pores and cracks under external loads. Numerous rock tests reveal a complex interplay between the closure of porous defects and the propagation of induced cracks, presenting challenges in accurately representing their mechanical properties, especially under true triaxial stress conditions. This paper proposes a conceptualization of rock at the mesoscopic level as a two-phase composite, consisting of a bonded medium matrix and frictional medium inclusions. The bonded medium is characterized as a mesoscopic elastic material, encompassing various minerals surrounding porous defects. Its mechanical properties are determined using the mixed multi-inclusion method. Transformation of the bonded medium into the frictional medium occurs through crack extension, with its elastoplastic properties defined by the Drucker–Prager yield criterion, accounting for hardening, softening, and extension. Mori–Tanaka and Eshelby’s equivalent inclusion methods are applied to the bonded and frictional media, respectively. The macroscopic mechanical properties of the rock are derived from these mesoscopic media. Consequently, a True Triaxial Macro-Mesoscopic (TTMM) constitutive model is developed. This model effectively captures the competitive effect and accurately describes the stress-deformation characteristics of granite. Utilizing the TTMM model, the strains resulting from porous defect closure and induced crack extension are differentiated, enabling quantitative determination of the associated damage evolution.

Abstract Deep coal‐rock formations are subjected to complex stress environments characterized by high static stresses and dynamic disturbances. To study the damage, fracture, and energy evolution characteristics of coal‐rock under dynamic–static combined loading, a new multiscale constitutive model for coal‐rock under dynamic–static combined loading is proposed based on micromechanics, and it is implemented into the LS‐DYNA solver. A numerical model of coal‐rock Split Hopkinson Pressure Bar under dynamic–static combined loading is established using LS‐DYNA, and research on the mechanical and energy evolution characteristics of coal‐rock under one‐dimensional and three‐dimensional dynamic–static combined loading is conducted. The results show that under one‐dimensional dynamic–static combined loading, with the increase of precompression, the dynamic peak stress linearly decreases while the combined peak stress linearly increases, and the dissipated energy of the specimen shows a decreasing trend. The fracture patterns of the coal‐rock specimen include internal shear fracture and external tensile fracture, and eventually, these two modes of fracture intersect to form macroscopic mesh cracks. As the axial pressure increases, the degree of specimen fragmentation gradually increases. Under three‐dimensional dynamic–static combined loading, with the increase of preconfining pressure, the stress–strain curve of the specimen will transition from “stress drop” to “stress rebound” after the peak. The peak stress increases with the increase of confining pressure, and the energy dissipation density of the specimen increases first and then decreases with the increase of confining pressure. With the increase of confining pressure, the hoop deformation of the specimen plays a constraining role, and the degree of specimen fracture gradually weakens, and the time of fracture occurrence gradually delays. The research results contribute to revealing the mechanical and energy mechanisms of rockburst disasters in deep coal mines.

Abstract The creep characteristics and potential deformation patterns of gangue backfill material are crucial in backfill mining operations. This study utilizes crushed gangue from the Gangue Yard in Fuxin City as the research material. An in-house designed, large-scale, triaxial gangue compaction test system was used. Triaxial compaction creep tests were conducted on gangue materials with varying particle size distributions. Analysis was performed based on different particle sizes, stresses, and confinement pressures. The study investigates the creep characteristics of the gangue under different conditions and explores the underlying causes. It reveals the relationship between the creep deformation of gangue materials and the passage of time. Mathematical methods are applied to develop a triaxial compaction creep power law model for gangue backfill materials. Finally, the creep results are fitted using an empirical formula approach.

Prediction of the flow stress of materials using a flow constitutive model provides strong support for engineering practice and promotes the continuous development of aluminum alloys and relevant application fields. Optimizing the parameters of flow constitutive models is a key concern to explain and predict the flow behavior. In this study, a genetic algorithm (GA) is used to optimize the parameters of flow constitutive models widely used for the flow behavior of Al alloy including modified Johnson-Cook model, hyperbolic sinusoidal Arrhenius-type model, SK-Paul model, modified Zerilli-Armstrong model, Kobayashi-Dodd model, and modified Fields-Backofen model. AA6061−T6 alloy is used in this study since it has been used as a representative Al alloy. The performance of the models optimized by GA was evaluated through comparative analysis with mechanical test. The Gleeble-3800 thermal simulation testing apparatus was employed to conduct unidirectional thermal compression tests under multi conditions, including different temperatures (573 ∼ 783 K), diverse strain rates vary from 0.001 to 1 s−1, and a range of strains (0 ∼ 0.8). The performance of all the models optimized by GA is enhanced, and the optimization effect of GA on SK-Paul model is most pronounced, which exhibits a maximum correlation coefficient (R) of 0.99731 and a minimum average absolute relative error (AARE) of 6.53%. The findings highlight the validity of GA optimization in flow constitutive models in the prediction of the flow behavior of Al alloy.

Static liquefaction is a form of unstable behaviour of granular soil. It is most common in saturated loose sands under monotonically loaded undrained conditions. Predicting static liquefaction using an elastic-plastic model that incorporates the non-associated plastic flow rule and strain hardening is possible. The article briefly describes the unstable behaviour of saturated sand in undrained conditions under a monotonic load. A simple elastic-plastic model with deviatoric hardening and a Drucker–Prager load surface is presented. The constitutive relationships were programmed in a Python script. Simulations of triaxial tests under mixed stress-strain control demonstrated the model’s ability to predict various undrained sand responses, including fully stable responses (no liquefaction) and partial and complete liquefaction under triaxial compression and tension. Predicting static liquefaction is possible by properly selecting the proportions of the parameters involved in plastic potential and loading functions and the parameter A used in the deviatoric hardening rule of hyperbolic type.

CO2 adsorption causes damage degradation to the coal body and thus reduces its stability, challenging the long-term safety of CO2 sequestration, and it is important to clarify the role of CO2 degradation and establish an ontological model. The damage mechanics theory and statistical theory were used to derive the calculation formula that can comprehensively reflect the total damage variables of the coal body under CO2 adsorption and load coupling, and focusing on the influence of the pressure-tight section, the fine statistical damage ontological equation of the coal body under the action of CO2 was established by segmentation, and the method of determining each parameter of the model was clarified. Finally, the parameters of the constitutive model were determined by CT scanning experiment system and MTS 816 experiment system, and the uniaxial compression experiments of coal body under different CO2 pressures were carried out by the self-developed gas-solid coupling experiment system to verify the rationality of the model. The results show that: ① The damage variables under adsorption and loading were defined based on the fracture rate obtained from CT scanning and by applying the Weibull distribution theory, respectively, and the total damage variable under the coupling of the two was further obtained by combining the damage theory, and a fine-scale statistical damage constitutive model was established; ② Three-dimensional reconstruction of the fracture based on CT scanning technology realistically reflects the fracture extension characteristics before and after CO2 interaction， the higher the CO2 pressure, the fuller the fracture expansion, the greater the three-dimensional fracture parameters and damage variables of the coal samples, and the more complex the spatial fracture network formed; ③ CO2 had a significant deterioration effect on the physical properties of the coal body, and the compressive strength and modulus of elasticity of the coal body were both reduced by 49.78% and 22.63%, respectively, with the increase of CO2 pressure, and the combined effect of dissolution, plasticization and air wedge effect of CO2 on the coal body led to the reduction of the mechanical parameters; ④ The theoretical curves of the fine statistical damage model of the coal body under the action of CO2 have a high degree of agreement with the uniaxial experimental curves, which indicates that the present structural model can better reflect the damage degradation effect of CO2 on the physical properties of the coal body, and embodies the reasonableness and applicability of the constitutive model and the method for determining the model parameters.