Stress-strain Behavior Research Articles

Responses of Ice-Soil Mixtures to Ice Melting

Numerous ice-soil-mixture landslide dams have formed in the cryosphere such as the Tibetan Plateau and resulted in disastrous consequences after these dams broke. The dam forming materials are often ice-soil mixtures that consist of graded soil particles and fragmented ice particles. The performance of such mixtures when subject to ice melting has rarely been studied; yet understanding the thermal-hydro-mechanical behavior of such ice-soil mixtures is essential for mitigating glacier hazards. In this study, the mechanical responses of ice-soil mixture to ice melting were investigated using an advanced stress- and temperature-controlled triaxial apparatus. Ice-soil mixtures with various initial ice contents were tested under different stress states. In each test, the progression of ice melting, local and global deformation, and post-melting stress-strain behavior were measured and evaluated. The test program led to the first batch of experiment data on the mechanical responses of ice-soil mixtures to ice melting. A relationship between normalized volumetric change and normalized time was established to describe the progression of ice melting. The melting of ice particles caused significant deformation, increases in the void ratio and degree of saturation, and reductions in the shear strength. These properties reached a steady state when the initial ice content exceeded 30%.

Optimization and Prediction of the Mechanical Properties of Concrete with Crumb Rubber and Stainless-Steel Fibers Under Varying Temperatures

This research develops an equation to describe the relationship between stress (σ) and strain (ε) in concrete under different conditions. It includes important parameters from earlier studies to improve predictions of stress–strain behavior, especially for concrete with crumb rubber and stainless-steel fibers at various temperatures. The initial phase assessed three existing stress–strain formulas as a basis for optimization. Using the Genetic Algorithm (GA) and the Whale Optimization Algorithm (WOA), a new equation was created to simulate the stress–strain relationship while considering temperature changes and material additions. Results showed that Formula (1), optimized with the WOA, performed much better than other polynomial and exponential formulas, proving the WOA’s effectiveness over the traditional GA. A comparison of the mechanical properties from experiments and those predicted by the new formula showed a high level of accuracy. Key properties like the maximum stress, strain at maximum stress, modulus of elasticity, and toughness were well captured. The findings highlight how temperature and material composition significantly affect concrete’s mechanical behavior. Overall, this research offers important insights into the factors influencing concrete performance, providing a solid framework for future studies and practical applications in engineering and construction. The proposed formula is a reliable tool for predicting concrete’s mechanical properties under various conditions, which aids in better modeling and optimization in concrete design.

An Experimental Study on Axial Stress-Strain Behaviour of FRP-Confined Square Lightweight Aggregate Concrete Columns

An Experimental Study on Axial Stress-Strain Behaviour of FRP-Confined Square Lightweight Aggregate Concrete Columns

Dynamic Tensile Response of Basalt Fibre Grids for Textile-Reinforced Mortar (TRM) Strengthening Systems.

The present work constitutes the initial experimental effort to characterise the dynamic tensile performance of basalt fibre grids employed in TRM systems. The tensile behaviour of a bi-directional basalt fibre grid was explored using a high-speed servo-hydraulic testing machine with specialised grips. Deformation and failure modes were captured using a high-speed camera. Tensile strain values were extracted from the recorded images using the MATLAB computer vision tool, 'vision.PointTracker'. The specimens, consisting of one and four rovings, were tested at intermediate (1-8/s) and quasi-static (10-3/s) strain rates. After the tensile tests, scanning electron microscopy (SEM) analyses were performed to examine the microscopic failure of the material. Linear and non-linear stress-strain behaviours were observed in the range of 10-3 to 1/s and 4 to 8/s, respectively. Tensile strength, ultimate strain, toughness, and elastic modulus increased at intermediate strain rates. Overall, the dynamic increase factors for these properties, except for the latter, were between 1.4 and 2.3. At the macroscopic level, the grid failed in a brittle manner. However, microscopic analyses revealed that the failure modes of the fibre and polymer coating were strain-rate sensitive. The enhanced tensile performance of the grid under dynamic loading conditions rendered it suitable for retrofitting structures prone to extreme loading conditions.

Enhancing the Performance of Concrete Coupled Shearwall Using Shape Memory Alloys

ABSTRACTUtilizing self‐centering materials, such as shape memory alloys (SMA), as reinforcement in concrete structures can positively influence their performance during and after earthquakes. Despite the high cost of SMAs, their unique flag‐shaped stress–strain behavior and effective energy dissipation make them an attractive material choice in some structures. This study evaluates the application of iron‐based SMAs in enhancing the seismic performance of coupled concrete shear walls. The purpose is to identify optimal SMA placement strategies within the walls' plastic hinges to improve energy dissipation, reduce residual drift, and enhance ductility. This research explores pre‐tensioned and non‐pre‐tensioned SMA configurations through macro‐element modeling and cyclic analysis. Presenting a comparative framework that balances material efficiency and structural performance differentiates this study from prior studies focused predominantly on SMA benefits in isolated structural applications. Two optimization scenarios are proposed: maximizing energy dissipation and minimizing residual drift, and reducing SMA usage while maintaining structural efficiency. The results indicate that pre‐tensioned SMAs in the wall web provide the most significant improvement in seismic behavior, significantly reducing residual drift and increasing ductility. This approach offers a cost‐effective solution for improving earthquake resilience in structures.

Tailoring Mechanical Performance in Bulk Nanoparticle-Structured ZnO and Al₂O₃: Insights from Deep Learning Potential Molecular Dynamics Simulations

The rapid advancements in nanotechnology have created unique opportunities to manipulate material properties at the nanoscale, particularly through the design of nanoparticle-structured (NP-structured) materials. Due to their distinctive mechanical and chemical properties, materials composed of nanoparticles, such as ZnO and Al₂O₃, are of high interest for applications in structural reinforcements, electronics, and catalysis. However, accurately predicting the mechanical behavior of NP-structured materials remains a challenge. This study investigates the mechanical properties of bulk nanoparticle-structured (NP-structured) materials composed of ZnO and Al₂O₃ nanoparticles in FCC and BCC configurations. We used deep learning potentials (DLPs) derived from density functional theory (DFT) calculations to comprehensively analyze stress-strain behavior, local shear strain distributions, and elastic properties across various nanoparticle sizes and compositions. Our findings reveal that nanoparticle size and crystalline arrangement are crucial in determining the mechanical performance of these materials. Smaller ZnO nanoparticles exhibit higher yield stress, ultimate stress, and Young's modulus in both FCC and BCC configurations, attributed to their higher surface-to-volume (S/V) ratio. In contrast, larger Al₂O₃ nanoparticles demonstrated superior mechanical properties, especially in FCC configurations, due to the strong ionic bonding and effective stress distribution inherent in Al₂O₃. In ZnO/Al₂O₃ composite systems, we found that the mechanical properties could be precisely tuned by adjusting the nanoparticle size and ratio. Larger nanoparticles in FCC arrangements contributed to higher yield stress and stiffness, while smaller nanoparticles in BCC arrangements provided better overall mechanical performance. This work highlights the potential of DLPs in accurately predicting and optimizing the mechanical properties of NP-structured materials, offering valuable insights for the design of advanced materials with tailored mechanical characteristics.

Study on the scale effect and mechanical properties of gravel materials in riverbed cover layers

To address the challenges of performing in-situ tests on riverbed overburden gravel, this study employs three scaling methods—equal mass substitution, similar gradation, and the mixed method—to investigate the original gradation of the gravel. Large-scale triaxial consolidated drained shear tests were conducted to evaluate the effects of the maximum particle size reduction ratio (M) and confining pressure on the stress–strain behavior, fractal dimension, particle breakage, and the parameters of the Duncan-Chang model (an elastic model describing nonlinear stress-strain relationships). The study explores how scaling, based on fractal dimension and particle breakage rate, impacts the strength and deformation characteristics of gravel materials. The results show that increasing confining pressure typically leads to higher material strength. As confining pressure increases, particle breakage becomes more pronounced across the various scaling methods. Gravel processed using the similar gradation method exhibited the highest strength, the smallest change in fractal dimension, and the lowest breakage rate, followed by the mixed method. Furthermore, as the M value increases, peak stress also rises, with the modulus coefficient (k) and bulk modulus coefficient (Kb) in the Duncan-Chang model increasing by 4.5 times and 3.3 times, respectively, for M = 15 compared to M = 0. A clear relationship was observed between the change in fractal dimension before and after testing and the breakage index (Bg). As the M value increases, both the difference in fractal dimension and the breakage rate decrease, suggesting that larger M values lead to reduced particle breakage and improved mechanical stability.

Effect of surface condition on fatigue life of 7075 aluminium alloy

ABSTRACT This study investigates the effects of surface treatments on the mechanical properties of 4 mm thick flat test specimens made from annealed AA 7075 alloy in three conditions: as-received, shot-peened, and electropolished. Experimental investigations, including cyclic stress response, fatigue life, microstructural observations, and mechanical properties, are conducted to provide insights into the fatigue behaviour of the alloy. The surface roughness (Ra) values were measured at 546 nm for as-received, 830 nm for shot-peened, and 72 nm for electropolished samples. Push–pull fatigue tests conducted at a stress amplitude of 500 MPa with a load ratio (R) of -1 yielded average fatigue lives of 1200 cycles for as-received, 990 cycles for shot-peened, and 2700 cycles for electropolished samples. These results align with the general observation that smoother surfaces yield better fatigue life, which can be explained by the influence of surface conditions on stress–strain behaviour, microstructure, and fracture mechanisms. The smoother surfaces have lower stress concentration points, so the propensity for crack nucleation and propagation is lower in these samples, leading to improved mechanical properties.

Application of computer models of rock mass quality and stress–strain behavior for stability assessment of mine openings

Application of computer models of rock mass quality and stress–strain behavior for stability assessment of mine openings

Crystal Plasticity Simulation of Cyclic Behaviors of AZ31B Magnesium Alloys via a Modified Dislocation-Twinning-Detwinning Model.

In this study, a probabilistic model within the dislotwin constitutive framework of DAMASK (the Düsseldorf Advanced Material Simulation Kit) was established to describe the cyclic loading behaviors of AZ31B magnesium alloys. Considering the detwinning procedure within the twinned region, this newly developed dislocation-twinning-detwinning model was employed to accurately simulate stress-strain behaviors of AZ31B magnesium alloys throughout tension-compression-tension (T-C-T) cycle loading. The investigations revealed that the reduction in yield stress during the reverse loading process was attributed to the active operation of twinning and detwinning modes. Furthermore, the evolution of the twin volume fraction during cycle loading scenarios was quantitatively determined. According to these results, the relative activities of plastic deformation modes during T-C-T loading were further analyzed.

Dynamic In-Plane Compression and Fracture Growth in a Quasi-Isotropic Carbon-Fiber-Reinforced Polymer Composite.

This study presents an experimental investigation of the quasi-static and dynamic behavior of a quasi-isotropic carbon-fiber-reinforced composite subjected to in-plane compressive loading. The experiments were performed at strain rates ranging from 4×10-5 to ∼1200 s-1 to quantifythe strain-rate-dependent response, failure propagation, and damage morphology using advanced camera systems. Fiber bridging, kink band formation, dominance of interlaminar failure, and inter-fiber failure fracture planes are evidenced through post-mortem analysis. The evolution of the in-plane compressive strength, failure strength, and stiffness are quantified across the strain rates considered in this study. For an in-depth understanding of the failure propagation, crack speeds were determined in two subsets; (i) primary and secondary cracking, and (ii) the interfaces participating in the crack propagation. Lastly, a modified Zhu-Wang-Tang viscoelastic constitutive model was used to characterize the dynamic stress-strain and compressive behavior of the quasi-isotropic composite under in-plane compression.

Axial compressive performance of low-carbon high-strength recycled aggregate concrete

AbstractThis paper introduces a novel material, low-carbon high-strength recycled aggregate concrete (LCHRAC), developed by activating ground granulated blast-furnace slag (GGBS) and silica fume (SF) in an alkaline environment and integrating recycled aggregate. To evaluate its mechanical properties, uniaxial compressive tests were performed, systematically analyzing the effects of recycled concrete aggregate (RCA) substitution ratios, as well as the characteristic parameters of steel and polypropylene(PP) fibers, on LCHRAC’s mechanical behavior. The results indicated that compressive strength shows a gradual decline as the RCA substitution ratio increases, with a moderate reduction of 7.1% up to 50% replacement, and a more significant drop, retaining only 68.6% at 100% replacement. In contrast, the peak strain increases linearly, showing a 29% improvement at full replacement, while the toughness index exhibits a consistent upward trend, increasing by approximately 123% at a 100% replacement rate. Based on experimental data, empirical models were developed to predict the influence of key control variables on the compressive strength, peak strain, elastic modulus, and the uniaxial compressive stress–strain behavior of LCHRAC. Additionally, advanced characterization techniques, including X-ray diffraction (XRD), thermogravimetric analysis (TGA/DTG), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS), were employed to elucidate the hydration mechanisms of the slag-silica fume composite system. These findings provide a comprehensive understanding of the mechanical performance and microstructural characteristics of LCHRAC, contributing to its potential application in sustainable construction practices.

Continuum-Particle Coupling for Polymer Simulations.

We report a concurrent hybrid multiscale simulation method, in which a particle domain is coupled with a surrounding continuum domain. The particle domain consists of a coarse-grained model of poly(lactic acid) and the continuum domain is treated using the finite element method. The coarse-grained model is derived from an atomistic model, using the iterative Boltzmann inversion scheme. The particle- and the finite element-domains overlap in a bridging domain through anchor points. In this coupling, the information passes back and forth between the high- and the low-resolution domains, effectively bridging the gap between the nano and macro-scales. This scheme is employed to simulate the coupled particle-continuum domains under both stochastic and semistochastic boundary conditions. While the anchor points keep the volume of the particle domain fixed in the former case, there is no anchor point in the planes normal to the periodic direction, in the latter case. The stress-strain behavior of polymer under both stochastic and semistochastic boundary conditions is investigated and the results are compared with those calculated from pure finite element reference simulations. Furthermore, the stress-strain relationship for the coupled system under the semistochastic boundary conditions is examined under plane stress and plane strain conditions, and the results are compared with those of pure finite element reference simulations. The hybrid particle-continuum method reproduces the pure finite element simulation results well.

Mechanism Study on the Intrinsic Damage and Microchemical Interactions of Argillaceous Siltstone Under Different Water Temperatures

Argillaceous siltstone is prone to deformation and softening when exposed to water, which poses a great threat to practical engineering. There are significant differences in the degrees of damage to this type of rock caused by solutions with different water temperatures. This study aimed to better understand the effect of temperature on argillaceous siltstone by designing immersion tests at water temperatures of 5, 15, 25, and 35 °C, analyzing the mechanical properties and cation concentration shifts under each condition. A water temperature–force coupled geometric damage model for argillaceous siltstone was developed, incorporating a Weibull distribution function and composite damage factors to derive a statistical damage constitutive model. The findings reveal that, with increasing water temperature, the peak strength and elastic modulus of argillaceous siltstone display a concave trend, initially decreasing and then increasing, while the cation concentration follows a convex trend, first increasing and then decreasing. Between 15 and 25 °C, the stress–strain behavior transitions from a four-phase to a five-phase pattern, with pronounced plasticity. The model’s theoretical curves align closely with experimental data, with the Weibull parameters m and λ effectively capturing the rock’s strength and plastic characteristics. Changes in water temperature notably influence the damage variable D12 in the context of water temperature–peak stress coupling, with D12 initially increasing and then decreasing with higher temperatures. These research results can provide new methods for exploring the paths of soft rock disasters and provide guidance for designing defenses in geotechnical engineering.

Optimization of carbon nanotubes in carbon black‐filled natural rubber: Constitutive modeling and verification using finite element analysis

AbstractCarbon nanotubes (CNTs) are novel one‐dimensional nanomaterials with a large aspect ratio and specific surface area, exhibiting excellent electrical and thermal properties that have led to their extensive utilization in rubber nanocomposites. In this paper, the effect of CNTs and carbon black juxtaposition on the properties of natural rubber is investigated using two different structures of CNTs, namely GC‐30 and GT‐210. The experimental results show that GT‐210 CNTs exhibit superior performance when incorporated into natural rubber. In addition, finite elements are employed for constitutive modeling to facilitate meaningful explorations in mechanical calculation and characterization of rubber filled with CNTs. Simulating the mechanical behavior of rubber materials under different working conditions (tensile and compressive) offers a cost‐effective and time‐efficient approach to predicting and optimizing material performance.Highlights Characterization of filler dispersion by Mooney–Rivlin curves. Fitting material stress–strain behavior using constitutive models. Offers an approach to predicting and optimizing material performance.

An investigation of recycled rubber composites reinforced with micro glass bubbles: an experimental and numerical approach

ABSTRACT Recycled rubber is widely used for its lightweight and cost-effective properties but often has limited mechanical strength, restricting its applications. This study enhances the mechanical performance of devulcanised recycled rubber by reinforcing it with micro glass bubbles (GBs) featuring a density of 0.65 g/cm³ and an elastic modulus of 3.5 GPa, offering a high strength-to-density ratio. Uniaxial compression tests were conducted on samples with GB volume fractions of 5%, 10%, and 15%. Results were validated through finite element analysis (FEA) in ABAQUS/Standard, incorporating randomised GB distributions. A 2D representative volume element (RVE) with randomly distributed GBs was modelled, applying periodic boundary conditions to simplify the composite into an equivalent homogeneous material. Numerical simulations assessed the effects of GB diameters (30, 40, and 50 µm) and inclusion size ranges (20–50 µm and 10–60 µm), finding minimal impact on results. The RVE, sized at 238 µm, accurately represented macroscale composite behaviour. Stress-strain behaviour was analysed using average stress and strain tensors. The strong agreement between experimental and numerical results validates the proposed method, demonstrating its accuracy in predicting the mechanical behaviour of the reinforced composite material.

Radial mechanical properties of deoxyribonucleic acid molecules

Given the small diameter of deoxyribonucleic acid (DNA), the difficulty in studying its radial mechanical properties laid in the challenge of applying a precise and controlled small force. In this work, the radial mechanical properties of DNA were measured in the AFM. DNA adhesion properties were analyzed through force-distance curves and adhesion images. The adhesion force values applied on DNA obtained from the force-distance curves were consistent with those obtained from the adhesion images. The Young's modulus of DNA was determined by collecting the data of indentation depth and the force applied on DNA and using the Hertz model for calculation. At the same compression speed, the Young's moduli increased with increasing forces, but exhibited a nonlinear growth. This reflected the complex stress-strain behavior of DNA. The impact of speeds on mechanical properties of DNA was explored. Higher speed resulted in greater Young's moduli and adhesion. This study not only deepens the understanding the mechanical properties of DNA, but also provides a strategy for investigating the mechanical properties of other thin and soft materials.

Tensile Properties, Strain Rate Sensitivity and Microstructural Analysis of SN100C Solder Alloys

Sn-Cu-Ni-Ge (SN100C®) is a high-performance Pb-free solder alloy widely used in the electronics manufacturing industry due to its excellent soldering performance and lower cost. SN100C has a huge potential to replace the commonly used Sn-Ag-Cu solders. This work investigates the effect of different strain rates (10-3 to 8×10-1s-1) on tensile performance for bulk SN100C samples at room temperature. The tensile properties, e.g., elastic modulus (E), yield strength (σy) and tensile strength (σT) are determined from the stress-stress curves. The value of σy and σT increases with increasing strain rates and this increase becomes less prominent at higher strain rates. Necking and ductile fracture are observed for all samples with a significant number of dimples, voids and tongues formed. The level of ductility of the samples decreases with increasing strain rates, which is further confirmed by the stress-strain behaviour. The microstructural evolution of the samples is evaluated by optical microscope (OM), scanning electron microscope (SEM) and energy dispersive X-ray (EDX) to reveal the generation of recrystallisation and fracture of the intermetallic compounds (IMCs) at the fracture tips and identify the embedded of IMCs within the sample matrix.

Simulations of Physical Properties of Alkoxy-Azoxybenzene Liquid Crystalline Homologous Series and Comparison with Experimental Results

This study investigates the intricate inter- and intra-molecular interactions that govern the range and nature of mesophases observed in homologous series of liquid crystalline materials. Using computational modelling, we compared the results with reported experimental values for several members of the series. Our analysis focused on various parameters, including lattice energy, orientational order parameter, moduli, stress-strain behaviour, Helmholtz free energy, orientational distribution function, zero-point energy, and molecular polarizabilities. Our findings reveal a strong correlation between the computational results and experimental data, providing valuable insights into the mesophases of these compounds. This alignment underscores the significance of our approach in understanding the fundamental behaviors of liquid crystalline materials.

Machine Learning–Enhanced Modeling of Stress–Strain Behavior of Frozen Sandy Soil

Machine Learning–Enhanced Modeling of Stress–Strain Behavior of Frozen Sandy Soil