Failure Strain Research Articles

Mechanical Properties and Stress–Strain Relationship of Grade 14.9 Superhigh-Tension Bolt (SHTB) Under Fire

Grade 14.9 superhigh-strength bolts (SHTBs) are a type of high-strength steel bolt with a nominal tensile strength of 1400 MPa, which is significantly higher than the commonly used Grade 10.9 high-strength bolt (HSB), which has a nominal tensile strength of 1000 MPa. The use of an SHTB can reduce the number of bolts required in connections or joints, leading to material savings and improved construction efficiency. However, like HSB, the mechanical properties of an SHTB can be significantly degraded at high temperatures, though the extent of this reduction may differ. In this study, the authors designed and conducted experiments on SHTBs under elevated temperatures including both vibration and tensile coupon tests. Based on the test data, the stress–strain curves and key mechanical properties such as the Young’s modulus, yield stress, ultimate stress, ultimate strain, percentage elongation, cross-sectional area reduction, and failure strain were obtained and analyzed for various high-temperature conditions. Furthermore, a new three-stage model was proposed to describe the stress–strain relationship of SHTBs under fire conditions. Additionally, empirical formulae were developed to predict the mechanical properties of SHTBs under elevated temperatures, providing valuable insights for engineering applications and fire safety design.

Assessing compatibility of clayey soils using state variables for sustainable DMM in Saga Lowland, Kyushu, Japan

The deep mixing method (DMM) has become a leading ground improvement technique in Japan over 60 years. However, recent cases of construction defects suggest not only environmental factors but also human errors, such as poorly constructed improved columns. Engineers may struggle to visualize soil behavior from geotechnical borehole survey data from structural viewpoint. This study focuses on the unconfined compression characteristics, sensitivity, and compressibility of clayey soil samples collected from the Kyushu region of Japan. Statistical data, such as the mean values of state variables including failure strain (εf), normalized deformation modulus (E50/su), liquidity index (IL), and compression index ratio (Cc1/Cc2) were calculated. By incorporating soil structure considerations into the comparative analysis of these variables, the study aimed to identify thresholds that indicate the "compatibility" or "incompatibility" of clayey soils. Clayey soils with εf < 2.8%, E50/su ≥ 110, IL ≥ 1.11, and Cc1/Cc2 ≥ 1.43 were classified as “compatible” with a bulky structure, while those with εf ≥ 2.8%, E50/su < 110, IL < 1.11, and Cc1/Cc2 < 1.43 were “incompatible” with a dense structure. The findings provide a structural framework for engineers to interpret soil data, improving DMM quality, risk management, and sustainable construction.

Manufacturing and Characterisation of a Tungsten Fibre-Reinforced Polymer Composite

Using metal fibres in fibre-reinforced polymers is a way to tailor not only the mechanical properties but also material properties like, e.g., electrical and thermal conductivity or toughness. While recent works focus on ductile steel fibres, this work demonstrates the manufacturability of tungsten fibre-reinforced polymers. The Vacuum Assisted Process works well to quasi-unidirectionally reinforce an epoxy matrix with tungsten fibres of 150 µm diameter, achieving a fibre volume content of 23 ± 1% (±standard deviation). Tensile tests of 10 mm-wide tungsten fibre-reinforced polymer specimens yield a Young’s modulus of 89 ± 5 GPa, an ultimate tensile strength of 615 ± 33 MPa, and a failure strain of 1.9 ± 0.2%. The fractured specimens are further investigated, revealing that 66% of the tungsten fibres fail in a dominantly ductile manner with a strongly localised region of plastic deformation. This is a unique feature of tungsten fibres with the potential to enhance the fracture toughness of fibre-reinforced polymers.

Predictive Modeling of Tensile Fracture in Synthetic Fiber Ropes Using Generalized Additive Models

ABSTRACTThis study investigates the tensile failure behavior of synthetic fiber ropes composed of nylon (6‐PA), polypropylene (i‐PP), and polyester (PET) fibers. A comprehensive experimental program was conducted using 202 rope specimens, with nominal diameters ranging from 4 to 20 mm, subjected to monotonic and cyclic loading conditions. The resulting load–strain data were systematically compiled for advanced statistical analysis. Generalized additive models (GAMs) were developed using R programming to predict failure forces and strains, incorporating a Weibull distribution framework for failure responses. The GAM approach demonstrated superior predictive capability, revealing a linear correlation between rope diameter and failure strain across all materials, as well as a nonlinear relationship between diameter and failure force. Notably, GAM models utilizing natural‐spline representations exhibited enhanced performance over conventional Weibull models. These findings contribute to a deeper understanding of the tensile properties of synthetic ropes, offering a data‐driven approach to optimize testing efforts and improve the reliability of these materials for engineering applications.

Smart Cement Behavior with Aggregates, Silicate, Clay, Carbon Dioxide and Real-Time Monitoring Characterized Using Vipulanandan Models

Chemo-thermo-piezoresistive smart cement is a highly sensing binder that was recently developed to be used in multiple infrastructure applications in new constructions and also integrated into in-service infrastructures for real-time monitoring. In this study, the effects of up to 75% aggregates (representing concrete), 0.3% silicate, 5% clay (inorganic contamination) and 3% carbon dioxide (CO2) on the curing and compressive piezoresistive behavior of the smart cement with less and 0.1% well dispersed carbon fibers was investigated. Also, the effect of temperature on the smart cement with silicate additive was investigated. A new material characterization method has been developed and was used to identify the critical electrical property of the smart cement with aggregates and other additives and the electrical resistivity was identified as the critical property to monitor. Hence a two-probe method was developed to monitor the resistivity changes in the cement. The piezoresistive axial strain at peak stress for the concrete with smart cement was over hundred percent which is 336 times (33,600%) higher compared to the concrete failure strain of 0.3%. The effects of silicate, clay and carbon dioxide on the initial resistivity (quality of mixing), temperature and compressive piezoresistivity have been quantified using Vipulanandan Models. It is important to monitor the real material property changes in the field and not just the temperature which is not a material property. A new approach has been developed to wirelessly transfer the two probes monitoring of the changes in resistivity of smart cement, smart concrete, regular cement and concrete to the phone and computers.

Microstructural Deformation and Failure of Highly Explosive-Filled Polymer Composites Under Dynamic Compression.

The dynamic mechanical properties and damage behaviors of polymer-bonded explosives (PBXs), as a kind of highly particle-filled polymer composite, must be known to ensure the safe use of related weapons and munitions. The high particle volume fraction of PBXs, which can reach approximately 95%, makes it difficult to investigate their mechanical properties and damage behavior via conventional methods. In this study, a microstructural model was developed by employing the Voronoi correction method to achieve a highly particle-filled PBX. Additionally, a bilinear model was used to accurately represent the nonlinearity of the stress-strain curve, while a zero-thickness cohesive zone model was incorporated to effectively describe the damage mechanism. The dynamic mechanical properties and damage behavior of PBXs with high particle fractions were elucidated to comprehensively understand the effects of strain rate, interface strength, and particle volume fraction on peak stress, failure strain, and damage extent. The numerical results exhibit excellent concurrence with existing experimental measurements and other computational simulations. The mechanical behavior of PBXs was also described by developing a viscoelastic model based on damage, which incorporated the equations associated with macroscopic and microscopic damage evolution. Overall, the proposed numerical technique is effective for comprehending the mechanical behavior and microscopic damage response of PBXs subjected to dynamic compression.

Effect of defect on mechanical properties of two-dimensional MoS2 membranes

Abstract Molybdenum disulfide (MoS2) has wide applications in many fields, such as electrode materials and energy storage. Therefore, it is crucial to investigate and determine how defects affect the mechanical characteristics of 2D MoS2 membranes. This work examined the impact of vacancy defects on the tensile characteristics of uniaxially and biaxially stressed monolayer MoS2 using molecular dynamics simulations. We have separated them into different cases, including the impact of the length size and width size of the vacancy defect, defect rotation angle, and vacancy defect’s quantity on the fracture behavior under various tensile loads. The tensile characteristics were examined in both the armchair and zigzag directions. The presence of a vacancy defect causes localized stress concentration, which initiates crack formation at the defect site, resulting in reduced fracture strain. When the size or the number of vacancies increases in the orientation perpendicular to the applied tensile force, it decreases Young’s modulus, ultimate stress, and failure strain of the material. With the same length and width of the defect, altering the angle (θ) between the defect edge and the tensile orientation—significantly impacts the material’s mechanical properties. Under uniaxial tension, an increase in the angle θ decreases Young’s modulus, ultimate stress, and failure strain, with the maximum strength occurring at θ = 0°. In contrast, during biaxial tension, the relationship between the mechanical properties and the rotation angle lacks a clear trend, notably, the minimum ultimate stress value is observed when θ = 45°.

Enhancing structural integrity of magnesium with hydroxyapatite and tantalum reinforcement

The present study reports on the development and characterization of Mg-Ta-HA composites with powder metallurgy. The densities and porosities of magnesium composites and pure magnesium are calculated, and the Rule-of-Mixture method used to determine the theoretical density of the composites. It verified that dense pure magnesium and magnesium composites be produced using powder metallurgy techniques. Examining the composites’ microstructures reveals the uniformity of the grain size as well as the impact of changing the Ta and HA reinforcement. The lack of intermetallic compounds between magnesium and reinforcement confirmed by X-ray diffraction analysis. Magnesium powders undergo mechanical milling to lower their average particle size, and reinforcement materials added to further reduce the particle size. The milling process results in a decrease in powder size due to the friction generated by the reinforcement materials. Both the compressibility of the green compacts and the attachment of particles during sintering impact the densification and porosity of the composites. The results indicate that composites with 3 and 6 wt% Ta have fine Ta and HA particles evenly dispersed in the Mg matrices, with no voids. In contrast, composites with 8 wt% HA and 9 wt% Ta show agglomeration of Ta particles in the Mg matrices and the appearance of noticeable voids. As the Ta, content increases from 0 to 6 wt%, the ultimate compression strengths, failure strain, and elastic moduli of the composites tend to rise. However, these properties seem to decrease as the Ta content increases further from 6 to 9 wt%. Nonetheless, the yield strength increases as the Ta reinforcement goes from 6 to 9 wt%. It suggested identify the optimal parameters for producing biocompatible Mg composites with appropriate strength, hardness, and ductility.

The Dynamic Mechanical Response of Anchored Fissured Rock Masses at Different Fissure Angles: A Coupled Finite Difference–Discrete Element Method

Anchored surrounding rock is prone to large nonlinear deformation and instability failure under dynamic disturbances. The fissures and defects within the surrounding rock make the rock mass’s bearing characteristics and deformation instability behavior increasingly complex. To investigate the effect of the fissure angle on the dynamic mechanical response of the anchored body, a dynamic loading model of the anchored, fissured surrounding rock unit body was established based on the finite difference–discrete element coupling method. The main conclusions are as follows: Compared to the indoor test results, this numerical model can accurately simulate the dynamic response characteristics of the unit body. As the fissure angle increased, the dynamic strength, failure strain, and dynamic elastic modulus of the specimen generally decreased and then increased, with a critical angle at approximately 45°. Compared to 0°, when the fissure angle was 45°, the dynamic strength, failure strain, and dynamic elastic modulus decreased by 17.08%, 15.48%, and 9.11%, respectively. Additionally, the evolution process of cracks and fragments shows that the larger the fissure angle, the more likely cracks are to develop along the initial fissure direction, which then triggers the formation of tensile cracks in other regions. Increasing the fissure angle causes the specimen to rupture earlier, making the main rupture plane more directional.

The effects of high strain-rate and temperature on tensile properties of UHMWPE composite laminates

The effects of high strain-rate and temperature on tensile properties of UHMWPE composite laminates

Rate dependency and fragmentation response of phase field models with micro inertia and micro viscosity terms

Rate dependency and fragmentation response of phase field models with micro inertia and micro viscosity terms

Numerical simulation and R-curves computation of CFRP compact tension tests using the discrete ply model

Efficient and accurate failure modelling of composite materials is crucial due to their extensive use in the industry. Specifically, simulating translaminar failure, such as Compact Tension (CT) tests using finite element analysis, has proven particularly challenging. This study applies the mesoscale finite element Discrete Ply Model (DPM) to the case of unidirectional carbon fibre CT tests. The stacking sequence employed is [45/-45/[0/90]4]s. This configuration has demonstrated significant experimental advantages, such as reduced specimen buckling and minimal shear matrix plasticity. However, it also displays a more complex combination of failure modes, including extensive delamination during crack propagation. This may result in inaccurate computation of the critical Strain Energy Release Rate (SERR), thus requiring new analysis methods. In the DPM, matrix cracking and delamination are explicitly represented. Failure modes such as fibre failure in tension/compression, shear damage and crushing are modelled within the behaviour volume elements. A new law that accounts for the increase in compressive failure strain in the presence of planar or strain gradients is proposed and shown to be crucial to the correct complete computation of the failure scenario. This approach shows relevant numerical and experimental correlation, both for the force-displacement curves and for the critical SERR computed with the compliance method. To address the issue of the complex CT failure scenario, the model estimates the energy dissipated by each failure mode. A numerical R-curve is also computed directly from these energies, allowing the discussion of the different ways of computing R-curves, numerically and experimentally.

Effects of Thermal Cycles on Mechanical Properties of RPECC: Static and Dynamic Splitting Tensile Performance.

This paper examines the splitting tensile properties of rubberized polyethylene-engineered cementitious composites (RPECC) through static and dynamic experimental tests, highlighting the effects of thermal cycles, impact strain rates, and rubber powder substitution rates for fine aggregates. Damage patterns, ultimate tensile strength, time-dependent stress curves, dynamic failure strain, and the dynamic increase factor of the RPECC are presented. The microstructure of the material is analyzed using scanning electron microscopy and energy-dispersive X-ray spectroscopy. Experimental results reveal that incorporating rubber powders significantly enhances the deformability and ductility of RPECC in splitting tension. However, a high content of rubber powders, such as a substitution percentage of 30%, significantly reduces static and the dynamic ultimate tensile strength of the RPECC by 16.8% and 34.2%, respectively. Microstructural examinations indicate that thermal cycling weakens the internal adhesion between the rubber particles, polyethylene fibers, and the ECC matrix, resulting in the frequent withdrawal of fibers and the formation of calcium hydroxide, which diminishes the material tensile strength by up to 20.6% in static tests and 45.1% in dynamic tests. Despite these challenges, the RPECC with 20% rubber achieves a favorable balance between splitting the tensile properties and thermal resistance, even after undergoing 270 heat-cool cycles, suggesting its potential applicability in harsh environments.

Study on the Transverse Properties of T800-Grade Unidirectional Carbon Fiber-Reinforced Polymers.

This paper focuses on the transverse tensile and compressive mechanical properties of T800-grade unidirectional (UD) carbon fiber-reinforced polymers (CFRPs). Firstly, transverse tensile and compressive tests were conducted on UD composite laminates, yielding corresponding stress-strain curves. The results indicated that, for tension, the transverse tensile modulus, strength, and failure strain were 8.7 GPa, 64 MPa, and 0.74%, respectively, whereas for compression, these values were 8.4 GPa, 197.1 MPa, and 3.43%, respectively. The experimental curves indicated brittle failure under tensile loadings and significant plastic failure characteristics under compressive loading for the T800-grade composite. Subsequently, fractography experiments were performed to observe the fracture morphologies, revealing that tensile fractures were through-thickness cracks perpendicular to the loading direction, while compressive fractures were at a 52° angle to the loading direction. Finally, a micromechanical finite element method (FEM) was employed to simulate the tensile and compressive failure processes of the unidirectional composite, and the tensile and compressive properties were predicted. The simulation results showed that under both tensile and compressive loadings, interfacial elements failed first, causing stress concentration and damage to nearby resin elements. The damaged resin and interfacial elements expanded and connected, leading to ultimate failure. The predicted tensile stress-strain curve exhibited linear characteristics consistent with the experimental results in most regions but showed more pronounced nonlinearity before ultimate failure. The predicted compressive stress-strain curve aligned well with the experimental results in terms of nonlinearity. The predicted elastic modulus, failure strengths, and failure strains were in good agreement with the experimental results, with differences of 1.1% (tension modulus), 3.2% (tension strength), and 13.5% (tension failure strain), and 3.6% (compression modulus), -8.5% (compression strength), and -3.8% (compression failure strain). The final failure morphologies were in good accordance with the fractography experimental observations.

Does quercetin affect tendon healing? An experimental study in a rat model of Achilles tendon injury.

The objective of this study was to investigate the impact of quercetin, a potent antioxidant, on tendon healing utilizing a rat Achilles tendon injury model. The study involved 32 male Wistar-Albino rats, randomly split into experimental (quercetin) and control groups, each with 16 rats. A bilateral Achilles tenotomy model was applied, with the experimental group receiving quercetin and the control group receiving corn oil via oral gavage from surgery until sacrifice. One Achilles tendon per rat underwent histopathological and immunohistochemical evaluations, while the other underwent biomechanical analysis. Tendons were evaluated histopathologically in terms of tenocyte, ground substance, collagen, and vascularity, and quercetin was observed to significantly increase tendon healing in the experimental group (p-values = 0.0232, 0.0128, 0.0272, 0.0307, respectively). In the immunohistochemical analysis, type I collagen, type III collagen, alpha smooth muscle actin (SMA), and Galectin-3 were evaluated, and it was observed that quercetin increased tendon healing (p-values = 0.0166, 0.0036, 0.0323, 0.0295, respectively). In the biomechanical analysis, the rupture strength was evaluated with six parameters (failure load, maximum energy, displacement, stiffness, ultimate stress, and strain), and it was observed that quercetin significantly increased the rupture strength (p-values = 0.032, 0.014, 0.026, 0.025, 0.045, 0.012, respectively). Quercetin significantly enhanced tendon healing both biomechanically and immunohistochemically. However, further clinical studies are needed to understand its effects on human tendon healing, as this is the first study of its kind.

Effects of specimen size and loading rate on the mechanical property of Bentonil-WRK bentonite for engineered barrier system

Effects of specimen size and loading rate on the mechanical property of Bentonil-WRK bentonite for engineered barrier system

Improved Mesenchymal Stem Cell Viability in High-Stiffness, Translational Cartilage Matrix Hydrogels.

Scaffolds made from cartilage extracellular matrix are promising materials for articular cartilage repair, attributed to their intrinsic bioactivity that may promote chondrogenesis. While several cartilage matrix-based scaffolds have supported chondrogenesis in vitro and/or invivo, it remains a challenge to balance the biological response (e.g., chondroinductivity) with structural (e.g., robust mechanical performance, >1 MPa in compressive stiffness) and translational (e.g., ease of surgical implantation) considerations. Few studies have evaluated encapsulated cell viability within high-stiffness (>1 MPa) hydrogels. We previously fabricated one formulation of a high-stiffness (>3 MPa) pentenoate-functionalized, solubilized, devitalized cartilage (PSDVC) hydrogel that possessed an injectable, paste-like precursor for easy surgical application. In the current study, the characterization of the PSDVC material was expanded by varying the degree of functionalization (i.e., 0.45-1.09 mmol/g) and amount of crosslinker, dithiothreitol (DTT), to improve the reproducibility of the high compressive moduli and evaluate the viability of encapsulated human bone marrow-derived mesenchymal stem cells (hBMSCs) in high-stiffness cartilage matrix hydrogels. Prior to crosslinking, specific formulations functionalized with 0.80 mmol/g or less of pentenoate groups retained a paste-like precursor rheology. After crosslinking, these formulations produced hydrogels with greater than 1 MPa compressive stiffness. However, hBMSCs encapsulated in PSDVC hydrogels with lower functionalization (i.e., 0.57 mmol/g, no crosslinker) had a higher stiffness (i.e., 1.4 MPa) but the lowest viability of encapsulated hBMSCs (i.e., 5%). The middle PSDVC functionalization (i.e., 0.70 mmol/g) with DTT (i.e., 0.50 mmol thiols/g) demonstrated high cell viability (77%), high mechanical performance (1.65 MPa, 31% failure strain), and translational features (i.e., paste-like precursor, 1.5 min crosslinking time). For future evaluations of PSDVC hydrogels in cartilage repair, a middle functionalization (i.e., 0.70-0.80 mmol/g) with the addition of a crosslinker (i.e., 0.50 mmol thiols/g) had a desirable balance of high mechanical performance (i.e., >1 MPa compressive stiffness), high viability, and paste-like precursor for surgical translation.

Optimizing solvent systems for electrospun PLGA scaffolds: effects on microstructure and mechanical properties for biomedical applications.

Electrospun scaffolds fabricated from poly(lactic-co-glycolic acid) (PLGA) have garnered widespread interest in biomedical applications due to their ability to mimic the extracellular matrix (ECM) structure with a tunable degradability profile. The properties of electrospun scaffolds are meticulously tailored for specific applications through the adjustment of polymer properties, solution parameters, and processing conditions. Solvent selection is crucial, influencing polymer spinnability and scaffold topographical, physical and mechanical features. Hansen solubility theory aids in predicting suitable solvent systems. The absence of specific data prompted a solubility experiment to determine Hansen solubility parameters for PLGA. Subsequently, various solvent systems were investigated for their impact on the microstructure of electrospun PLGA scaffolds. Optimizing the electrospinning process resulted in fibrous scaffolds with consistent average fibre diameter from different solvent systems, allowing a focused examination of the solvent's isolated influence on mechanical properties. PLGA samples electrospun using hexafluoro isopropanol (HFIP) displayed lower Young's modulus and ultimate tensile strength but higher failure strains than those created using binary solvent systems composed of tetrahydrofuran (THF), dichloromethane (DCM), and dimethylformamide (DMF). This research advances the understanding and optimization of electrospun PLGA scaffolds, enhancing their potential for biomedical applications.

Research on biaxial tensile fracture prediction of 5052 aluminum alloy on electromagnetic sheet bulging

High-speed deformation fracture prediction of aluminum sheet, especially for biaxial tension state deformation, was a major problem in the development of electromagnetic bulging process. In this study, the biaxial tension failure limit of the AA5052 sheet was tested by the electromagnetic high-speed biaxial tensile testing equipment and quasi-static Nakazima experiment. A Digital Image Correlation (DIC) system was used to measure failure strain. Based on the tested data, a failure model considered stress state and strain rate coupling effect was established, which available for electromagnetic bulging failure prediction. Electromagnetic free bulging experiments were conducted to verify the failure criteria effectiveness. Results showed that the strain rate effects of the failure strain were influenced by the loading path. The strain rate effect of the sheet failure strain under plain strain state was higher than the loading stress triaxiality of uniaxial and biaxial tension state. Compared with the fracture prediction criterion ignored stress state effect on strain rate influence factor, the modified fracture model considered stress state and strain rate coupling effect could well predict the failure of electromagnetic bulging, which would exhibit different failure models at the rounded corner or the top under different discharge energies.

Prediction of Strength Properties of Reinforced and Stabilized Sandy Soil as a Building Foundation Material

Sandy soils are a type of geomaterial that may require improvements due to lack of cohesion. In this study, first, the lack of cohesion of sand was resolved using clay, and the soil was stabilized with cement and lime (4% and 3% of the dry weight of materials, respectively) and finally reinforced with recycled tire fibers of 20 to 30 mm in length for improved strength and ductility. Next, 747 samples with different fiber contents at different curing temperatures and ages were prepared and a unconfined compressive strength (UCS) test was carried out. Next, a novel approach employing multivariate nonlinear regression techniques and obtained empirical data was applied to formulate a mathematical model for predicting the UCS and the modulus of elasticity (Es) of the reinforced and stabilized soil. This model can serve as a valuable tool for building engineers in designing building foundations. The comparison of the obtained UCS and Es results and those predicted using the proposed model showed a correlation of &gt;95% (R2 ≥ 0.95). The fibers effectively increased the failure strain, thus resulting in the greater ductility of the samples. As an example, in 14-day samples cured at 60 °C with 0%, 0.4%, 1%, 1.7%, and 2.5% fibers, the failure strain showed an incremental trend of 1.47%, 1.87%, 2.08%, 2.20%, and 2.92%, respectively. Scanning electron microscopy (SEM) was used to study the microstructure of the samples and to explain the strength experimental outcomes. SEM images showed a desirable interaction between the fiber surfaces with the soil mass and the reduction in porosity and the occurrence of pozzolanic reactions through stabilization. The results also showed that the reinforcement effectively improved the ductility, as desired for building foundations; however, it resulted in reduced strength, although a greater strength compared to the untreated soil was achieved. Although soil stabilization has been widely studied, limited research focuses on stabilizing soil with clay, lime, cement, and recycled tire fibers. This study offers design engineers an estimation scheme of the strength properties of stabilized and reinforced foundations.