Search

The aim of this work was to develop an experimental protocol that takes into account the influence of experimental conditions on these perineal tissues, before determining their mechanical properties. Samples of each perineal tissue layer were obtained from the skin, the vagina, the external anal sphincter (EAS), the internal anal sphincter (IAS) and anal mucosa of freshly dead sows. They were tested in quasi-static uniaxial tension using the Mach-1 testing machine. Stress-strain curves of each perineal tissue layer before the first damage for each sow were obtained and modeled by hyperelastic laws described by three coefficients: C1, C2, and C3 (Yeoh model). The influence of sample preparation conditions such as tissue freezing, hygrometry and sample orientation were evaluated, and the conditions under which the tests were performed such as the displacement velocity during testing were also evaluated by analysing C1-coefficient. This study suggested that sample preparation conditions such as tissue freezing for 24 h, storage in cellophane paper for two hours and the strain rate did not statistically affect the C1-hyperelastic coefficient for each perineal layer (p > 0.05). Samples should not be stored in saline for 2 h (p < 0.05). Sample orientation did not influence C1-hyperelastic coefficient (p > 0.05). This experimental protocol could be used to study in vitro biomechanical properties of perineal tissues in order to better understand perineal tears during delivery. [ABSTRACT FROM AUTHOR]

Brittleness is an important mechanical property of rock. Accurately evaluating rock brittleness and its influence on the TBM tunnelling performance is necessary. In this work, via two practical engineering cases, with the aim of overcoming the difficulty of penetrating extremely hard rock (breccia fused tuff) in the Z huxi project, the influence of rock brittleness on the TBM tunnelling performance was studied via comparative analysis with that Nabang project. Seven commonly used rock brittleness indices based on stress‒strain curves were summarized, and a brittleness evaluation method suitable for extremely hard rock was determined by introducing the normalized specific energy to obtain brittleness indices for two lithologies (breccia fused tuff and biotite hornblende plagioclase gneiss) in two projects. The influences of rock brittleness on penetration and the specific energy were compared and analysed. The results showed that the brittleness indices B 3 and B 5 were more suitable for evaluating rock brittleness. Rock brittleness influenced the TBM tunnelling performance, but this influence gradually decreased with decreasing uniaxial compressive strength ( UCS ), which is obviously less than that of the rock strength. When the UCS was lower than 150 MPa, the TBM tunnelling parameters could be adjusted within a significant margin to eliminate the influence of rock brittleness, which could be ignored when predicting the tunnelling performance. When the UCS was greater than 150 MPa, rock brittleness imposed a notable influence on the tunnelling performance, which must be considered when predicting the tunnelling performance. This research could provide reference data for evaluating the hard rock brittleness index and accurately predicting the TBM tunnelling performance in engineering practice. [ABSTRACT FROM AUTHOR]

This study investigates the influence of expanded perlite (EP) replacement rate and curing methods on the compressive strength of concrete at different ages through the uniaxial compression test. The stress–strain full curve model of concrete considering EP replacement rate is established, and a damage evolution model considering curing conditions, EP replacement rate and load effects is developed based on the damage theory. The results show that: (1) The lack of water in concrete curing will have a huge negative impact on its mechanical properties, and the internal curing effect of pre‐wet EP can effectively alleviate the phenomenon of incomplete hydration. (2) Under dry curing, the addition of EP will reduce the early compressive strength of concrete, while its internal curing effect can improve the compressive strength of concrete in the later stages. (3) The C & C model and the Guozhenhai model are used to construct the segmented model in the rising and falling sections, and the model parameter formula is deduced by the replacement rate. The model can fully describe the stress–strain relationship of expanded perlite concrete (EPC). (4) The damage evolution model of EPC shows an "S" shape growth curve. Dry curing and EP replacement can both reduce the development rate of damage, while the former has a more significant impact. [ABSTRACT FROM AUTHOR]

The classical phase field model has wide applications for brittle materials, but nonlinearity and inelasticity are found in its stress–strain curve. The degradation function in the classical phase field model makes it a linear formulation of phase field and computationally attractive, but stiffness reduction happens even at low strain. In this paper, generalized polynomial degradation functions are investigated to solve this problem. The first derivative of degradation function at zero phase is added as an extra constraint, which renders higher-order polynomial degradation function and nonlinear formulation of phase field. Compared with other degradation functions (like algebraic fraction function, exponential function, and trigonometric function), this polynomial degradation function enables phase in [0, 1] (should still avoid the first derivative of degradation function at zero phase to be 0), so there is no Γ convergence problem. The good and meaningful finding is that, under the same fracture strength, the proposed phase field model has a larger length scale, which means larger element size and better computational efficiency. This proposed phase field model is implemented in LS-DYNA user-defined element and user-defined material and solved by the Newton–Raphson method. A tensile test shows that the first derivative of degradation function at zero phase does impact stress–strain curve. Mode I, mode II, and mixed-mode examples show the feasibility of the proposed phase field model in simulating brittle fracture. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials 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.)

In this study, we conducted a single-factor experiment where fine aggregates in each mixture were replaced with coal-fired slag at replacement rates in the range of 0–100%. We investigated the effect of slag substitution rate on the cubic compressive strength, splitting tensile strength, axial compressive strength, and static modulus of elasticity of slag concrete. Based on the experimental data, the stress–strain curve of the coal-fired slag concrete was divided into four phases: elastic, elasto-plastic, peak, and decline phases. A stress–strain constitutive equation was established to describe the coal-fired slag concrete. A replacement rate of 50% of the formulated coal-fired slag concrete meets the strength requirements of C60 structural applications, and the cubic compressive strength is the same as that of ordinary concrete. Coal-fired slag can be utilized in large quantities, improving the economic value of coal-fired slag and expanding the scope of application of slag concrete. [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.)

Microscopic stress-strain curves were obtained by applying stress measurements using the HR-EBSD method and strain measurements using the DIC method to the same field of view in SEM in-situ tensile tests. From the analysis of these microscopic stress-strain curves, yield stress map and work hardening rate map were successfully produced. The relationship between these mechanical property value maps and the microstructure is investigated. The yield stress maps confirm the tendency of the local yield stress to show different values for different grains, but the Schmid factor alone cannot explain the magnitude of the yield stress. When adjacent grains with significantly different Schmid factors deformed cooperatively, the yield stress is found to increase as a result of stress partitioning. Localized regions of extreme work hardening rates were observed in the work hardening rate maps. These regions were located close to grain boundaries with low mA values where slip transfer was difficult and an interruption of the slip bands was observed. In addition, the rate of increase of GND density with strain was large in these regions. From these results, it can be understood that the extreme work hardening rates are due to increased back stresses caused by the accumulation of dislocations on low mA grain boundaries. [ABSTRACT FROM AUTHOR]

Abstract The aim of this work was to develop an experimental protocol that takes into account the influence of experimental conditions on these perineal tissues, before determining their mechanical properties. Samples of each perineal tissue layer were obtained from the skin, the vagina, the external anal sphincter (EAS), the internal anal sphincter (IAS) and anal mucosa of freshly dead sows. They were tested in quasi-static uniaxial tension using the Mach-1 testing machine. Stress-strain curves of each perineal tissue layer before the first damage for each sow were obtained and modeled by hyperelastic laws described by three coefficients: C1, C2, and C3 (Yeoh model). The influence of sample preparation conditions such as tissue freezing, hygrometry and sample orientation were evaluated, and the conditions under which the tests were performed such as the displacement velocity during testing were also evaluated by analysing C1-coefficient. This study suggested that sample preparation conditions such as tissue freezing for 24 h, storage in cellophane paper for two hours and the strain rate did not statistically affect the C1-hyperelastic coefficient for each perineal layer (p > 0.05). Samples should not be stored in saline for 2 h (p 0.05). This experimental protocol could be used to study in vitro biomechanical properties of perineal tissues in order to better understand perineal tears during delivery.

The in-situ synthesized particle reinforced TC4 matrix composites were prepared by powder metallurgy pressureless sintering using polycarbosilane （PCS） as precursor. The thermal compression simulation experiments were conducted on TC4-1PCS （mass fraction of PCS is 1%） composites at 850-1100 ℃ and 0.001-1 s-1 to analyze the stress-strain curves of the composites under different parameters using the Gleeble-3500 thermal simulation testing machine. The effects of deformation parameters on the reinforced phase particles， matrix structure and densification were analyzed by OM， SEM and EBSD methods. The results indicate that the TiC reinforced phase particles with the size of 5-10 μm and large amount of residual pores are observed in the TC4-1PCS composites before hot deformation. The β transition temperature（Tβ） of TC4-1PCS matrix is 1000-1050 ℃. When deformed above Tβ， matrix of composite consists of lamellar quenched martensite， while the matrix turns into duplex microstructure， when deformed below Tβ. The deformation temperature determines the relative density and microstructure types of the composites， while the strain rate affects the phase size in the matrix and residual porosity. The densification of TC4-1PCS composites can be promoted by the increase of deformation temperature and the decrease of strain rate， while the increase of strain rate has obvious effect on the microstructure refinement. The microstructure refinement and densification of TC4-1PCS composites can be achieved by the deformation at 1050 ℃ and 0.1 s-1.

Abstract Brittleness is an important mechanical property of rock. Accurately evaluating rock brittleness and its influence on the TBM tunnelling performance is necessary. In this work, via two practical engineering cases, with the aim of overcoming the difficulty of penetrating extremely hard rock (breccia fused tuff) in the $$Z{\text{huxi}}$$ Z huxi project, the influence of rock brittleness on the TBM tunnelling performance was studied via comparative analysis with that $$Nabang$$ Nabang project. Seven commonly used rock brittleness indices based on stress‒strain curves were summarized, and a brittleness evaluation method suitable for extremely hard rock was determined by introducing the normalized specific energy to obtain brittleness indices for two lithologies (breccia fused tuff and biotite hornblende plagioclase gneiss) in two projects. The influences of rock brittleness on penetration and the specific energy were compared and analysed. The results showed that the brittleness indices $$B3$$ B 3 and $$B5$$ B 5 were more suitable for evaluating rock brittleness. Rock brittleness influenced the TBM tunnelling performance, but this influence gradually decreased with decreasing uniaxial compressive strength ( $$UCS$$ UCS ), which is obviously less than that of the rock strength. When the $$UCS$$ UCS was lower than 150 MPa, the TBM tunnelling parameters could be adjusted within a significant margin to eliminate the influence of rock brittleness, which could be ignored when predicting the tunnelling performance. When the $$UCS$$ UCS was greater than 150 MPa, rock brittleness imposed a notable influence on the tunnelling performance, which must be considered when predicting the tunnelling performance. This research could provide reference data for evaluating the hard rock brittleness index and accurately predicting the TBM tunnelling performance in engineering practice.

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.

The distribution pattern of cracks in rock masses, known as the geometric distribution, holds significant significance in understanding the progressive failure mechanism and stress concentration can lead to instability and even failure of the specimens. However, the macroscopic and microscopic mechanisms of crack coalescence and the failure of the sample are not yet clear. Thus, the discrete element method was used to investigate the influence of stress distribution on the fracture coalescence and failure of dual-crack specimens with different arrangements under uni-axial compression in this study. The obtained results were compared and analyzed with laboratory test results. The results show: When the double-crack specimens are under overlapping arrangement, the stress concentration area only appears at the end of the crack, which is conducive to crack propagation, resulting in no coalescence. However, if the two preexisting cracks were arranged in a co-planar or non-overlapping manner, the stress concentration of the sample would not only occur at the end of the cracks, but also between the cracks. As the stress increases, the cracks will gradually expand and connect, forming shear coalescence and mixed mode coalescence (shear and tensile) respectively. In addition, the arrangement of cracks greatly changes the influence of stress concentration on the failure mode of the specimen, leading to the possibility that the coalescence of the specimen may occur in three periods: before, during, and after the peak stress. The findings of this research hold immense importance in comprehending the mechanisms behind the coalescence and failure of rock fractures. Moreover, they provide valuable insights for the analysis and design of rock engineering projects, offering practical guidance for ensuring stability. [ABSTRACT FROM AUTHOR]

Rapid freeze-thaw (F-T) tests were conducted to study the frost resistance of desert sand concrete (DSC) at different stress levels (SL), desert sand replacement rate (DSRR) and the number of F-T cycles. The impact of the SL, DSRR, and number of F-T cycles on the mass loss rate, ultrasonic wave velocity, and stress-strain curve of DSC was investigated through uniaxial compression tests. Scanning electron microscope (SEM) was used to examine the microstructure of DSC. The constitutive relationship was established considering the influence of the SL and number of F-T cycles. The results indicated that the frost resistance and uniaxial compressive mechanical properties of DSC could be effectively enhanced when desert sand was added at 40%. The peak strain initially decreased and then increased as the DSRR increased. In contrast, the peak stress first increased and reached a maximum value as the DSRR increasing to 40%, followed by a gradual decrease. The F-T cycles gradually deteriorated the macroscopic properties of DSC. The proposed constitutive model of DSC was established by combining the two classical models as the ascending and descending sections, respectively. The model prediction results matched well with the experimental results, which can provide a theoretical basis for the engineering application of DSC under F-T cycles and loading environments. [ABSTRACT FROM AUTHOR]

The active metal brazing of a Si3N4 substrate with Cu has been evaluated for excellent reliability, demonstrating durability up to 1000 cycles in a cycling test ranging from −40°C to 250°C. While the finite element method (FEM) is commonly used for predicting thermal stress–strain in cyclic tests, experimental data on the measurement of thermal stress–strain on metallized substrates have remained limited. In this study, a digital image correlation (DIC) method was employed for the in situ measurement of thermal strain on a fully Cu‐coated Si3N4 substrate (AMB‐SN substrate) in various consecutive thermal cycles, ranging from 1–2 to 199–200. The thermal strains exhibited hysteresis curves that expanded slightly with cycles. By incorporating the coefficients of thermal expansion (CTE) of plain Cu and Si3N4, both the thermal stress and strain of Si3N4 and Cu on the AMB‐SN substrate were computed. The stress–strain curves of Cu revealed that the yield stress of Cu increased with the number of cycles, attributed to the cyclic hardening of the Cu layer. The Cu stress–strain curve calculated in this work showed a good agreement with the previous results obtained from compression/tension test of Cu at room temperature, which indicates the stress–strain curve of Cu on the composite was not sensitive to the temperature during the thermal cycle. [ABSTRACT FROM AUTHOR]

Abstract Geological hazards related to soft–hard interbedded rock are frequent in rock engineering. The material point method (MPM) is a mesh-free numerical approach specifically designed for analyzing large deformations. Notably, significant grid-crossing errors frequently arise when material points traverse the underlying grid. To investigate the failure mechanism of soft–hard interbedded rock, an enhanced MPM incorporating B-spline basis functions and Voronoi polygon discretization is developed and subsequently validated through comparisons with uniaxial compression test data and other numerical methods. The numerical results of soft–hard interbedded rock specimens associated with different soft layer dips (SLD) and confining pressures indicate that the SLD has a great effect on compressive strength and crack extension at low confining pressure. Rocks from SLD-30° to SLD-75° correspond to the “sliding failure along discontinuities” failure mode and have lower compressive strength than rocks with other SLD angles. It is also demonstrated that the propagation of cracks leads to a significant alteration in the internal stress state of the rock, and that stress concentrations at the crack tip exacerbate the development of failure surface. Furthermore, the failure mode of soft–hard interbedded rock can be categorized into four types: (1) sliding failure across multiple discontinuities, (2) tensile fracture across multiple discontinuities, (3) sliding failure along discontinuities, (4) tensile-split along discontinuities.

Abstract In order to further promote the application of cementitious sand gravel (CSG), the mechanical properties and variation rules of CSG material under triaxial test were studied. Considering the influence of fly ash content, water-binder ratio, sand rate and lateral confining pressure, 81 cylinder specimens were designed and made for conventional triaxial test, and the influence laws of stress–strain curve, failure pattern, elastic modulus, energy dissipation and damage evolution of specimens were analyzed. The results showed that the peak of stress–strain curve increased with the increase of confining pressure, and the peak stress, peak strain and energy dissipation all increased significantly, but the damage variable D decreased with the increase of confining pressure. Under triaxial compression, the specimen was basically sheared failure from the bonding surface, and the aggregate generally did not break. Sand rate had a significant effect on the peak stress of CSG, and decreased with the increase of sand rate. Under the conditions of the same cement content, fly ash content and confining pressure, the optimal water-binder ratio 1.2 existed when the sand rate was 0.2 and 0.3. After analyzing and processing the stress–strain curve of triaxial test, a Cuckoo Search-eXtreme Gradient Boosting (CS-XGBoost) curve prediction model was established, and the model was evaluated by evaluation indexes R2, RMSE and MAE. The average R2 of the XGBoost model based on initial parameters under 18 different output features was 0.8573, and the average R2 of the CS-XGBoost model was 0.9516, an increase of 10.10%. Moreover, the prediction curve was highly consistent with the test curve, indicating that the CS algorithm had significant advantages. The CS-XGBoost model could accurately predict the triaxial stress–strain curve of CSG.

Artificial frozen soil can be regarded as the blending of ideal solid and ideal fluid in a certain proportion. Its mechanical properties neither comply with the Hooke’s law nor the Newton’s viscosity law, but obey certain relationship between them. Fractional derivative can well describe this blending phenomenon. Uniaxial compression tests were performed on the expansive soils of Hefei under different freezing temperatures, and the influence law of freezing temperature on stress and strain were obtained. The fractional derivative was introduced into the exponential model, and the improved exponential model was the fractional exponential model of stress-strain under uniaxial compression of artificial frozen soil. By taking natural logarithms on both sides of the improved model, the stress-strain linear equations at different temperatures were obtained, and the fractional derivative model parameters were determined by solving the established equations. To further verify the applicability of the established model, a set of triaxial shear tests of frozen silty clay in Nanjing were quoted and the influence of confining pressure was taken into account in the fractional order coefficient. The stress-strain fractional order exponential model was improved to take the influence of confining pressure into account. Comparing the calculated results of the improved stress strain exponential equation of artificial frozen soil with the experimental results, the results show that the calculated results are in good agreement with the experimental results and can accurately predict the changing trend of the shear stress strain curves under uniaxial compression and triaxial compression. The improved fractional derivative model has few parameters and definite physical meaning, which is convenient for engineering application. The current model is only applicable to the strain hardening type. In order to further describe the mechanical properties of the strain softening type, the further study is to establish a fractional exponential model of the strain softening type by considering the damage in the model. At the same time, how to reflect the influence of the structure and anisotropy of frozen soil on the stress-strain in the model will also be investigated.

Featured Application: The maximal vertical distance (MVD) algorithm is intended to be used for the discretization of stress–strain metallic material curves for defining a multilinear material model when conducting a finite element analysis of engineering components with included material nonlinearities. The maximal vertical distance (MVD) recursive algorithm, a novel approach for the optimal discretization of stress–strain material curves, is proposed. The algorithm simplifies the process of defining multilinear curves from material stress–strain curves when conducting a finite element analysis (FEA) of components. By directly selecting points on the material curve, the MVD algorithm eliminates the requirement for initial discretization, thereby minimizing information loss. As the measure of goodness of fit of the simplified polyline to the original curve, the percentage of stress deviation (SD) is proposed. The algorithm can generate multiple multilinear curves while keeping the stress deviation of each curve within a predefined limit. This feature is particularly beneficial during the finite element analysis of components exhibiting complex and position-dependent material properties, such as surface-hardened components, ensuring consistent modelling accuracy of material properties across the components' geometry. Consistent accuracy also proves advantageous when exploring multiple differing material states of quenched and tempered steel, ensuring fair and reliable comparisons. The MVD algorithm was compared with existing algorithms from the literature, consistently maintaining the accuracy of the multilinear curves within predetermined limits using the fewest possible points. [ABSTRACT FROM AUTHOR]

The efficient characterization of material properties of porous multi-phase sintered steels by instrumental indentation is still an open question. To the authors' knowledge, so far only a characterization of single-phase porous sintered steel by nanoindenation has been reported in literature. This paper for the first time offers a study about the applicability of microindentation techniques for characterizing the matrix material in a multi-phase sintered steel. This preliminary study is motivated by the relatively wide availability of necessary equipment, and simplicity of material identification procedures. Herein, a dual-phase ferrite/bainite Astaloy steel with 9% porosity is studied. Various commonly used methods for the reconstruction of stress–strain curves from microindentation data are considered, whereby both Vickers and spherical tips are used. In addition, some homogeneous solid materials are investigated to better asses the performance of applied identification procedures. Two approaches for the mesoscale identification of the considered sintered steel are attempted. The first one is based on the identification of individual material phases, while in the other one the homogenization of the metallic matrix is adopted. To assess the reliability of obtained parameters, the direct numerical simulation of representative volume elements of realistic steel microstructure subjected to uniaxial tension is conducted. Numerical results are compared with the data from the macroscopic uniaxial tensile test. The obtained results indicate that microindentation is adequate for the identification of elastic properties of individual material phases, but results for local plastic parameters are largely inconclusive and a further analysis is needed, focusing on applying smaller forces and investigating the influence of pores on identification results. Nevertheless, it seems that macroscopic stress–strain curves could be captured more accurately by the methodology based on the matrix homogenization if relatively large indentation forces are applied. [ABSTRACT FROM AUTHOR]

Crack stress thresholds in rocks have long been a popular subject in rock mechanics and engineering research. In this study, the applicability of existing methods for determining the crack stress thresholds of granite and weakly cemented porous siltstone is investigated using step loading and unloading tests. In addition, a novel method for decomposing the volumetric strain into solid-phase linear elastic strain, gas-phase nonlinear elastic strain, and plastic volumetric strain is presented. A quantitative calculation method for determining these thresholds is proposed based on the evolution law of the gas-phase volumetric strain and the physical significance of crack stress thresholds. The initiation and termination points of the stationary stage of the gas-phase volumetric strain are determined as σ cc and σ ci ; the point at which the gas-phase strain changes from positive to negative is determined as σ cd . To validate the proposed method, statistical results of the existing methods after screening are compared with the results of the proposed method. The results show that the proposed method provides reasonable crack stress thresholds for siltstone and granite and is applicable to rocks with similar stress–strain behaviors. The proposed method offers the advantages of independence from other methods, suitability across high and low confining pressures, and the capability for the quantitative calculation and processing of numerous samples. [ABSTRACT FROM AUTHOR]

The use of ferronickel slag powder (FNSP) as a cementitious additional material has been supported by numerous reports. FNSP concrete has the same shortcomings as ordinary concrete, including low hardness. In this study, in order to make FNSP concrete more durable, end-hooked type steel fibers were incorporated. To understand how various elements affect the mechanical properties of steel fibers, an experiment was carried out on the mechanical properties of steel FNSP concrete (SFNSPC). FNSP's principal ingredients, with a particle size distribution ranging from 0.5 to 100 μm and a sheet-like powder shape, are CaO, SiO2, Al2O3, MgO, and others, according to tests conducted on the material's microstructure and composition. Then, eighteen mix proportions were developed, comprising six distinct FNSP replacement rate types and three distinct steel fiber content types. Crucial metrics were evaluated and analyzed, including the relationship among the toughness, tensile strength, and compressive strength as well as slump, splitting tensile strength, compressive strength, and uniaxial compressive stress–strain curve of SFNSPC. The results showed that the slump of SFNSPC under different FNSP replacement rates decreased with increasing steel fiber volume. Steel fibers have a small but positive effect on SFNSPC's compressive strength; nonetheless, as FNSP replacement rates increased, SFNSPC's slump gradually decreased, though not by much. These results show that FNSP is a viable alternative cementitious material in terms of strength. Specifically, the splitting tensile strength of SFNSPC improves with an increase in steel fiber content, and the pace at which SFNSPC strength drops with an increase in the FNSP replacement rate. With varying mix proportions, the stress–strain curve trend of SFNSPC remains mostly constant, and steel fibers improve the compressive toughness of SFNSPC. After adding 0.5% and 1.0% steel fibers, the toughness index of concrete with different FNSP replacement rates increased by 8–30% and 12–43%, respectively. [ABSTRACT FROM AUTHOR]

In order to further promote the application of cementitious sand gravel (CSG), the mechanical properties and variation rules of CSG material under triaxial test were studied. Considering the influence of fly ash content, water-binder ratio, sand rate and lateral confining pressure, 81 cylinder specimens were designed and made for conventional triaxial test, and the influence laws of stress–strain curve, failure pattern, elastic modulus, energy dissipation and damage evolution of specimens were analyzed. The results showed that the peak of stress–strain curve increased with the increase of confining pressure, and the peak stress, peak strain and energy dissipation all increased significantly, but the damage variable D decreased with the increase of confining pressure. Under triaxial compression, the specimen was basically sheared failure from the bonding surface, and the aggregate generally did not break. Sand rate had a significant effect on the peak stress of CSG, and decreased with the increase of sand rate. Under the conditions of the same cement content, fly ash content and confining pressure, the optimal water-binder ratio 1.2 existed when the sand rate was 0.2 and 0.3. After analyzing and processing the stress–strain curve of triaxial test, a Cuckoo Search-eXtreme Gradient Boosting (CS-XGBoost) curve prediction model was established, and the model was evaluated by evaluation indexes R2, RMSE and MAE. The average R2 of the XGBoost model based on initial parameters under 18 different output features was 0.8573, and the average R2 of the CS-XGBoost model was 0.9516, an increase of 10.10%. Moreover, the prediction curve was highly consistent with the test curve, indicating that the CS algorithm had significant advantages. The CS-XGBoost model could accurately predict the triaxial stress–strain curve of CSG. [ABSTRACT FROM AUTHOR]

The effects of different flyash content, steel fibre content and water-binder ratio on the dynamic compressive strength of alkali-activated slag high performance concrete (ASHPC) were studied. When flyash and water-binder ratio rose, the dynamic compressive strength of ASHPC fell by 27.3% and 23.5%, respectively, and increased by 81.6% when steel fibre content increased. The dynamic elastic modulus rises by 35.0% with an increase in steel fibre content and falls by 48.0% and 65.6%, respectively, with an increase in flyash content and water-binder ratio. The toughness conversion ratio and pre-peak toughness ratio dropped by 34.1% and 9.5%, respectively, whereas the post-peak toughness ratio rose by 36.4% with an increase in flyash content. The test block's pre-peak toughness ratio and toughness conversion ratio increased by 12.7% and 60.0%, respectively, with an increase in steel fibre , whereas the post-peak toughness ratio declined by 31.0%. With the increase of water-binder ratio, the pre-peak toughness ratio and toughness conversion rate of the test block increased by 31.0 % and 132 %, respectively, and the post-peak toughness ratio decreased by 42.8 %. The energy absorption and reflection rise while the energy transmission falls as flyash concentration and the water-binder ratio rise. The transmission energy rises as the amount of steel fibre grows, while the energy absorption and reflection fall. [ABSTRACT FROM AUTHOR]

Introduction: Data concerning the mechanical properties of the perineum during delivery are very limited. In vivo experiments raise ethical issues. The aim of the study was to describe some of the biomechanical properties of each perineal tissue layer collected from sows in order to better understand perineal tears during childbirth. Material and methods: Samples of each perineal tissue layer were obtained from the skin, the vagina, the external anal sphincter (EAS), the internal anal sphincter (IAS), and the anal mucosa of fresh dead sows. They were tested in quasi‐static uniaxial tension using the testing machine Mach‐1®. Tests were performed at a displacement velocity of 0.1 mm·s−1. Stress–strain curves of each perineal tissue layer before the first damage for each sow were obtained and modeled using a hyperelastic Yeoh model described by three coefficients: C1, C2, and C3. Pearson correlation coefficients were calculated to measure the correlation between the C1 hyperelastic coefficient and the duration between the first microfailure and the complete rupture for each perineal tissue layer. Pearson correlation was computed between C1 and the number of microfailures before complete rupture for each tissue. Results: Ten samples of each perineal tissue layer were analyzed. Mean values of C1 and corresponding standard deviations were 46 ± 15, 165 ± 60, 27 ± 10, 19 ± 13, 145 ± 28 kPa for the perineal skin, the vagina, the EAS, the IAS, and the anal mucosa, respectively. According to this same sample order, the first microfailure in the population of 10 sows appeared at an average of 54%, 27%, 70%, 131%, and 22% of strain. A correlation was found between C1 hyperelastic coefficient and the duration between the first microfailure and the complete rupture (r = 0.7, p = 0.02) or the number of microfailures before complete rupture only for the vagina (r = 0.7, p = 0.02). Conclusions: In this population of fresh dead sow's perineum, the vagina and the anal mucosa were the stiffest tissues. The IAS and EAS were more extensible and less stiff. A significantly positive correlation was found between C1 and the duration between the first microfailure and the complete rupture of the vagina, and the duration between the first microfailure and the complete rupture of the vagina. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on the determination of the mechanical behaviors of Grade 8.8 and 10.9 high-strength bolts at elevated temperatures. Strength reduction coefficients are obtained based on test results at temperatures ranging from 20°C to 900°C, for both yield and ultimate stresses. Simplified expressions are presented to identify the strength reduction factors at considered temperatures. At 400°C, the yield and ultimate strengths of bolts decrease by 30%–35% for both grades compared to those in ambient temperature. Yield strengths are 30% and 20% of yield strengths of Grade 8.8 and 10.9 bolts at ambient temperature, respectively, when the temperature exceeds 500°C. The ultimate strength decreases slightly slower than the yield strength at high temperatures. Although the decrease in ultimate strength follows the decrease in yield strength at elevated temperatures, it is slightly slower. About 3%–6% of yield and ultimate strengths at ambient temperature remain for both grades at 700°C. Moreover, a series of expressions are provided to obtain the full range stress–strain curve of high-strength bolts at elevated temperatures. Comprehensive literature studies are taken into consideration to propose a more generalized description of the stress–strain curves. The proposed model can be fully drawn by only using elastic modulus, yield, and ultimate stresses at ambient temperature. It is shown that the proposed model has enough efficiency to describe the general material behavior at elevated temperatures. [ABSTRACT FROM AUTHOR]

The equivalent stress block is recommended for use in the design of reinforced concrete sections to simplify the analysis of the composite behavior of concrete and steel reinforcement. In most current codes, a rectangular equivalent stress block is provided. The design parameters of the equivalent block were recommended many years ago. Due to the importance of the equivalent stress block concept, numerous investigations have been performed to increase its accuracy. In the current paper, an exploration of the rectangular equivalent stress block has been carried out using the energy modeling approach. Energy modeling is a new general approach for studying the behavior of concrete elements. In this method, the energy consumed (work done) can be determined by integrating the force-displacement diagram (in the current study this will be the concrete stress-strain curve in compression). Schematic and equivalent stress-strain curves for concrete in uniaxial compression provided in most current codes and relevant textbooks were considered in this research. The codes taken into account in the current study are ACI-318-19, Canadian Code CSA A23.3-04, Eurocode EC-2, and Chinese standard GB 500 10 - 2002. The energy consumed by these curves for different values of concrete strength has been compared with numerous experimental results. This comparison shows that the results of the equivalent stress block provided in most of the considered current codes are conservative. Applying the energy modeling for the considered experimental stress-strain curves a modified equivalent stress block is recommended for practical use. The results of the proposed equivalent stress block are in good agreement with the experimental ones. The ratio between the predicted total energy engaging the proposed model and the total energy calculated for the experimental results ranges between 0.95 and 1.08 with a mean value equal to unity. [ABSTRACT FROM AUTHOR]

In this paper, steel fiber coal gangue concrete is examined for its fire resistance, high strength, and stability, aiming to achieve both green sustainability and resistance to elevated temperatures. We conducted tests on concrete specimens with varying coal gangue aggregate volume replacement rates (0%, 20%, 40%, 60%) and steel fiber volume contents (0%, 0.5%, 1.0%, 1.5%) to assess their post-high-temperature mechanical properties. These tests were performed at five temperature levels: 20 °C, 200 °C, 400 °C, 600 °C, and 800 °C. The focus was on analyzing the residual mechanical properties and constitutive relationship of the steel fiber coal gangue concrete after exposure to high temperatures. The findings indicate that as the temperature rises, the compressive strength, split tensile strength, and modulus of elasticity of the steel fiber coal gangue concrete specimens undergo varying degrees of reduction. However, the peak strain and ultimate strain increase gradually. The incorporation of steel fibers enhances the mechanical properties of the coal gangue concrete, resulting in improvements in the elastic modulus and peak strain, both before and after exposure to high temperatures. Furthermore, the established constitutive relationship for steel fiber coal gangue concrete after high temperatures, derived from calculations and validated with experimental data, provides a more accurate representation of the entire damage process under uniaxial compressive loading at elevated temperatures. [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.)

During the operation of the Salt Cavern Flow Battery (SCFB) system, the rock surrounding a salt cavern is subjected to erosion by the electrolyte. To study the creep characteristics of electrolyte-bearing salt rock under long-term triaxial cyclic loading in SCFB, a triaxial creep experiment with a cycle period of 1 day was conducted. The results indicated that, when not subjected to failure, the axial stress-strain curve of electrolyte-bearing sample undergoes only two phases of “sparse-dense”, entering dense phase approximately 4 cycles earlier than that of sample without electrolyte. Under the same stress conditions, the strain generated in electrolyte-bearing salt rock surpasses that of sample without electrolyte, demonstrating an initial rapid increase followed by a gradual stabilization trend. The stress-strain curve of electrolyte-bearing sample in a single cycle can be divided into six stages. The number of cycles has almost no effect on the axial strain in stages I, IV, V and VI, and the axial strain in stages IV and VI is basically 0. Additionally, the elastic deformation generated in stage I is basically recovered in stage V. The strain in stage II gradually decreases and disappears in the 4th cycle, which is 13 cycles earlier than that of the sample without electrolyte. The creep rate of electrolyte-bearing sample shows a trend of “gradual decrease—basically stabilization” as the number of cycles increases, and the creep experiment contains only the decay creep stage and steady creep stage. Irreversible deformation of electrolyte-bearing sample exhibits a gradual decrease followed by stabilization with increasing number of cycles. The research findings hold significant implications for the stability analysis of SCFB systems.

In the preparation of large-sized ceramics, the use of a green body with relatively high plasticity is crucial to minimize the risk of cracking during processing. To achieve this goal, glycerol and polyethylene glycol (PEG) were utilized as plasticizers in the shaping of green bodies of oxide ceramics through spontaneous coagulation casting (SCC). This study investigated the effects of plasticizers and particle sizes ranging from the submicron to nanoscale on the slurry viscosity, drying shrinkage of wet gels, and mechanical properties of green bodies. The plasticity of the green bodies was assessed by measuring the impact toughness and flexural stress‒strain curves. By incorporating an appropriate plasticizer, the peak width of the flexural stress‒strain curve for dried green bodies from particles of different sizes was nearly twice that without plasticizers, and the impact toughness was enhanced by approximately 71%, 34%, and 41% when the particle size decreased from the submicron scale to the nanoscale (0.45 μm, 0.18 μm, and 50 nm, respectively). The drilling test revealed that there was nearly no cracking around the holes in the green bodies with plasticizers. The plasticity mechanism of the green bodies was examined based on ultraviolet–visible (UV–Vis) spectroscopy and scanning electron microscopy (SEM). It was discovered that plasticizers might mitigate the brittleness of green bodies by adjusting the interactions between molecules and modifying the gel network properly.

To enhance the mechanical properties of the Nitrate Ester Plasticized Polyether solid propellant matrix, the uniaxial tension of multi-component systems is simulated and the factors influencing the mechanical properties of the propellant matrix are investigated. First, mesoscale models of five types of systems include poly alpha olefin (PAO(3)), polyethylene glycol (PEG200, PEG400, PEG600), and 1,4-butanediol (BDO) are established, followed by uniaxial tensile simulations. The results show PEG600, PEG400, PEG200, BDO, and PAO(3) in order of enhancing the mechanical performance of the matrix. Second, the diffusion behavior of nitroglycerin (NG) and butanetriol trinitrate (BTTN) in various systems is investigated. The results show that NG exhibits higher diffusion capacity than BTTN, and the diffusion coefficient increases with an increment in the molecular weight of PEG. Additionally, the influence of different plasticizer ratios (2.8–3.0), curing parameters (1.58–1.62), and chain extension parameters (0.08–0.10) on the mechanical properties of the PEG600 system are investigated. The results demonstrate that as the plasticizer ratio increases, there is a gradual decrease in the modulus of the matrix. Additionally, an increase in the curing parameter leads to a substantial enhancement in the tensile strength of the matrix, while increasing the chain extension parameter significantly expands the maximum tensile length of the matrix. Finally, employing the Slip-Spring model, the effects of the physical and chemical cross-linked network of the propellant are simulated. The result shows that increasing the content of a chemical cross-linked network significantly improves the tensile strength of the matrix.

Polycrystalline materials are essential in engineering due to their ability to withstand various forces, heat, and environmental conditions. The arrangement of atoms within these crystals significantly affects their mechanical properties. This study used molecular dynamics simulations to explore how initial pressure affects the mechanical resilience of aluminum polycrystals. Aluminum composite materials, known for their strength, flexibility, and environmental sustainability, are the focus of this investigation. We particularly investigated stress-strain reactions at 1, 2, and 3 bar initial pressures. Reduced free volume causes atomic migration to be hampered as pressure increases, therefore affecting mean square displacement and diffusion coefficient. The results show that ultimate strength and Young's modulus of the polycrystalline samples were 30 and 6.64 GPa at 1 bar pressure. Moreover, the results demonstrated a notable decrease in mechanical performance by increasing pressure; the ultimate strength and Young's modulus of the polycrystalline samples diminished to 5.66 GPa and 22.43 GPa, respectively, at 3 bar. Furthermore, the heat flux increased by rising initial pressure in the Al-polycrystalline sample due to the compression of material that reduced atomic distances. This improved atomic arrangement facilitated more efficient heat transfer. These insights are essential for engineering applications, as they establish a foundation for the production of aluminum components that maintain structural integrity in the face of extreme conditions.

This study investigates the influence of High-Toughness Polypropylene (HTPP) fiber content (0 %, 0.3 %, 0.6 %, 0.9 %) on the axial compressive performance of ceramsite concrete. Four sets of ceramsite concrete cube and prism specimens were prepared, and the cube compressive strength and full stress-strain curves for each set were tested. Based on the experimental results, it analyzed the variation characteristics of HTPP fibers on the stress-strain curve of ceramic concrete at different stages, studied the peak stress, peak strain, elastic modulus, toughness, and energy absorption capacity of ceramic concrete. Finally, the stress-strain curve has been fitted. The results indicate that: HTPP fibers can significantly enhance the strength and toughness of ceramic concrete, the compressive strength of the cube increased by 23.8 %, the axial compressive strength increased by 19.0 %, the residual stress increased by 143.0 %, the absolute modulus increased by 164.1 %, the toughness increased by 51.5 %, and the energy dissipation coefficient increased by 9.4 %. By fitting the experimental curve, the mathematical expression for the uniaxial compressive stress-strain curve of ceramic concrete reinforced with high tenacity polypropylene (HTPP) fibers has been proposed. The model matches well with the experimental results, which provides a theoretical basis for the structural analysis and design of this type of concrete.

Copyright of Clinical Neuroscience / Ideggyógyászati Szemle is the property of LifeTime Media Kft. 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.)

By exploring the microstructure and mechanical properties of dispersed soil under different freeze-thaw cycles, the influence of freeze-thaw environment on soil strength was analyzed. Triaxial test and scanning electron microscope were used to study the mechanical properties and microstructure of dispersed soil under freeze-thaw cycle, and the image processing software IPP was used to obtain the microscopic pore parameters of soil samples, including porosity, average pore diameter and average shape coefficient. Research results indicated that the number and pore size of pore parameter in the soil structure showed an increasing trend, and the bonding effect between soil particles weakened. The breaking strength of dispersed soil was mainly influenced by the number, size, and shape of soil pores, and was negatively correlated with the average pore diameter, porosity, and average shape coefficient. The results of this study indicated that the microstructure of dispersed soils was constantly changing under the conditions of different numbers of freeze-thaw cycles, which in turn lead to changes in the mechanical properties of the soils. [ABSTRACT FROM AUTHOR]

This study employs density functional theory calculations to analyze the structural and mechanical properties of stanene nanosheets (SnNs), including elastic moduli, Poisson's ratio, and plastic behavior under various loads. Parameters of the Morse potential function governing stanene atom interactions are explored. The nanosheets demonstrate isotropic behavior with minimal discrepancy in Young's modulus between armchair and zigzag directions. Additionally, a progressive finite element method investigates fracture mechanics, simulating the mechanical response using a modified Morse potential function. The nonlinear stress–strain relationships for both pristine and defective armchair and zigzag stanene nanosheets are elucidated, revealing brittle behavior and slightly higher mechanical properties in armchair stanene. Single-vacancy defects significantly impact mechanical properties of stanene, while Stone–Wales defects have negligible effects. [ABSTRACT FROM AUTHOR]

Copyright of New Building Materials / Xinxing Jianzhu Cailiao is the property of New Building Materials 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.)

Thermal treatment temperature strongly influences the compressive fracture mechanical properties of brittle rocks with many microcracks. However, the correlation between thermal treatment temperature, microcrack variation, and macroscopic compressive fracture properties is rarely established. A micro–macro model is suggested to evaluate the influence of thermal treatment temperature on the quasi-static compressive fracture relating to microcrack damage in brittle rocks. This model consists of the strain-crack relation, the wing crack model, and the proposed temperature-dependent initial damage and fracture toughness equations. The temperature-dependent equations of initial damage and fracture toughness are determined by the experimental data. The relationship curves between stress and strain are drawn under different temperatures. The effects of the thermal treatment temperature on the compressive strength, crack initiation stress, peak axial strain, and elastic modulus are studied. Sensitivities of the confining pressure and the size, friction, and angle of initial crack on the thermal treatment temperature-dependent compressive strength and crack initiation stress are discussed. The study results have an important role in the estimation of the stability of artificial underground engineering and the disaster of natural geology. [ABSTRACT FROM AUTHOR]

In this study, a mathematical model based on graph theory is developed to analyse the deformed structures and mechanical properties of thermoplastic elastomers (TPEs) using ABA-type triblock copolymers. TPEs exhibit a network structure formed by bridge chains; deformation of this network structure causes stress. During the deformation of TPEs, domain breakage and coalescence occur, accompanied by topological changes in the chains, such as conformational transitions between the bridge and loop chains. By employing the mathematical concepts of harmonic realization of graphs in the physical space and the tension tensor to quantify the stress in the bridge-chain network structure, an effective method for analysing topologicalchanges in microstructures caused by elongation is proposed. As an application of this method, optimal geometric structures of block copolymers with desired functionalities can be determined. [ABSTRACT FROM AUTHOR]

The environmental impact of non-biodegradable rubber waste can be severe if they are buried in moist landfill soils or remain unused forever. This study deals with a sustainable approach for reusing discarded tires in construction materials. Replacing ordinary Portland cement (OPC) with an environmentally friendly geopolymer binder and integrating crumb rubber into pre-treated or non-treated geopolymer concrete as a partial replacement of natural aggregate is a great alternative to utilise tire waste and reduce CO2 emissions. Considering this, two sets of geopolymer concrete (GPC) mixes were manufactured, referred to as core mixes. Fine aggregates of the core geopolymer mixes were partially replaced with pre-treated and non-treated rubber crumbs to produce crumb rubber geopolymer concrete (CRGPC). The mechanical properties, such as compressive strength, stress–strain relationship, and elastic modulus of a rubberised geopolymer concrete of the reference GPC mix and the CRGPC were examined thoroughly to determine the performance of the products. Also, the mechanical properties of the CRGPC were compared with the existing material models. The result shows that the compressive strength and modulus of elasticity of CRGPC decrease with the increase of rubber content; for instance, a 33% reduction of the compressive strength is observed when 25% natural fine aggregate is replaced with crumb rubber. However, the strength and elasticity reduction can be minimised using pre-treated rubber particles. Based on the experimental results, stress–strain models for GPC and CRGPC are developed and proposed. The proposed models can accurately predict the properties of GPC and CRGPC. [ABSTRACT FROM AUTHOR]

In order to study the changes in elastic modulus and the dynamic evolution of cracks in sandstones with different inclination angles of rock bridges under cyclic loading, uniaxial cyclic loading and unloading tests, along with PFC2D simulations were carried out on sandstone specimens with rock bridge inclination angles of 15°, 45°, 75°, 90° and 105° when the fissure inclination angle was fixed at 45°. The results show that a significant strengthening of the elastic modulus of sandstone with different fissures due to cyclic loading. There is a correlation between the stress ‐ strain curve and the instantaneous microcrack evolution curve of specimens obtained from discrete element simulation under cyclic loading. The rock bridge inclination angle has an influence on the damage mode of sandstone, and the dynamic crack evolution in the PFC2D simulation can reasonably reflect the initiation location and growth direction of cracks in the rock. The damage defined based on the number of microcracks, corresponds well to the damage pattern, with the maximum original damage at a rock bridge inclination angle of 45°. [ABSTRACT FROM AUTHOR]

Dough extensional properties obtained from 14 wheat flours hydrated at 50% (/flour weight) were assessed by the empirical test of Alveograph, a bubble inflation test, and by the rheometric test of uniaxial compression in lubricated conditions (LSF) at large deformations. In baking industry, comparison between flours is based on several parameters (n ≥ 5) defined from the alveogram, which is the time variations of pressure inside dough. In this study, the alveogram is converted into a stress-strain curve (σ = f(εb)). Then, from this curve, the extensional behavior coefficient of the flours, assessed by the consistency k0, is fitted between 0 ≤ εb ≤ 1.5, assuming ε b ˙ = 0.25 s−1 (R2 = 0.99 ± 0.01 for 14 flours). The flow index (n = 0.36) and strain hardening index (SHI = 1.73) are kept constant. The model is validated by comparing the stress values calculated from the alveogram to those measured in LSF for wheat flour doughs hydrated at 50% (R2 = 0.91) at εb = 1 and 0.25.10−2 < ε b ˙ < 2.5 s−1. Therefore, the Alveograph, which allows classifying flours according to several dough stretching properties, also provides access to the model of dough extensional behavior. Determining dough extensional properties for alveograph test and validating by comparison with resutls obtained by LSF [ABSTRACT FROM AUTHOR]