Search Results (567)

Metallic nanofoams with amorphous structures demonstrate exceptional properties and significant potential for diverse applications. However, their mechanical properties at different temperatures are still unclear. By using molecular dynamics simulation, this study investigates the mechanical responses of representative CuZr amorphous metallic nanofoam (AMNF) under uniaxial tension and compression at various temperatures. Our results reveal that the mechanical properties, such as Young’s modulus, yield stress, and maximum stress, exhibit notable temperature sensitivity and tension–compression asymmetry. Under tensile loading, the Young’s modulus, yield strength, and peak stress exhibit significant reductions of approximately 30.5%, 33.3%, and 32.9%, respectively, as the temperature increases from 100 K to 600 K. Similarly, under compressive loading, these mechanical properties experience even greater declines, with the Young’s modulus, yield strength, and peak stress decreasing by about 34.5%, 38.0%, and 41.7% over the same temperature range. The tension–compression asymmetry in yield strength is temperature independent. Interestingly, the tension–compression asymmetry in elastic modulus becomes more pronounced at elevated temperatures, which is attributed to the influence of surface energy effects. This phenomenon is further amplified by the increased disparity in surface-area-to-volume ratio variations between tensile and compressive loading at higher temperatures. Additionally, as the temperature rises, despite material softening, the structural resistance under large tensile strains improves due to delayed ligament degradation and more uniform deformation distribution, delaying global failure. Full article

Despite the strength and ductility of steel reinforcing bars, their susceptibility to corrosion can limit the long-term durability of reinforced concrete structures. Fiber-reinforced polymer (FRP) reinforcing bars made with a thermosetting matrix offer corrosion resistance but cannot be field-bent, which limits flexibility during construction. FRP reinforcing bars made with fiber-reinforced thermoplastic polymers (FRTP) address this limitation; however, their high processing viscosity presents manufacturing challenges. In this study, the Continuous Forming Machine, a novel pultrusion device that uses pre-consolidated fiber-reinforced thermoplastic tapes as feedstock, is described and used to fabricate 12.7 mm nominal diameter thermoplastic composite rebars. Simple bend tests on FRTP rebar that rely on basic equipment are performed to verify its ability to be field-formed. The manual bending technique demonstrated here is practical and straightforward, although it does result in some fiber misalignment. Subsequently, surface deformations are introduced to the rebar to promote mechanical bonding with concrete, and tensile tests of the bars are conducted to determine their mechanical properties. Finally, flexural tests of simply-supported, 6 m long beams reinforced with FRTP rebar are performed to assess their strength and stiffness as well as the practicality of using FRTP rebar. The beam tests demonstrated the prototype FRTP rebar’s potential for reinforcing concrete beams, and the beam load–deformation response and capacity agree well with predictions developed using conventional structural analysis principles. Overall, the results of the research reported indicate that thermoplastic rebars manufactured via the Continuous Forming Machine are a promising alternative to both steel and conventional thermoset composite rebar. However, both the beam and tension test results indicate that improvements in material properties, especially elastic modulus, are necessary to meet the requirements of current FRP rebar specifications. Full article

In this study, a new fibre combination for an interlayer hybrid fibre-reinforced polymer laminate was investigated to achieve pseudo-ductile behaviour in tensile tests. The chosen high-strain fibre for this purpose was S-Glass, and the low-strain fibre was flax. These materials were chosen because of their relatively low environmental impact compared to carbon/carbon and carbon/glass hybrids. An analytical model was used to find an ideal combination of the two materials. With that model, the expected stress–strain relation could also be predicted analytically. The modelling was based on preliminary tensile tests of the two basic components investigated in this research: unidirectional laminates reinforced with either flax fibres or S-Glass fibres. Hybrid specimens were then designed, produced in a heat-assisted pressing process, and subjected to tensile tests. The strain measurement was performed using distributed fibre optic sensing. Ultimately, it was possible to obtain repeatable pseudo-ductile stress–strain behaviour with the chosen hybrid when the specimens were subjected to quasi-static uniaxial tension in the direction of the fibres. The intended damage-mode, consisting of a controlled delamination at the flax-fibre/glass-fibre interface after the flax fibres failed, followed by a load transfer to the glass fibre layers, was successfully achieved. The pseudo-ductile strain averaged 0.52% with a standard deviation of 0.09%, and the average load reserve after delamination was 145.5 MPa with a standard deviation of 48.5 MPa. The integrated fibre optic sensors allowed us to monitor and verify the damage process with increasing strain and load. Finally, the analytical model was compared to the measurements and was partially modified by neglecting the Weibull strength distribution of the high-strain material. Full article

To address the issue of the low compression–tension ratio in the traditional parallel bond model (PBM), this study proposes an improved PBM incorporating a random distribution strategy of strong–weak contact groups. An L₂₇(3¹²) orthogonal experimental design was employed to construct 27 sets of numerical simulation schemes. Combined with Pearson correlation coefficient analysis and multivariate regression, the influence of twelve microscopic parameters on seven of the macroscopic mechanical properties of sandstone was systematically investigated, including elastic modulus (E), Poisson’s ratio (v), uniaxial compressive strength (σ_c), internal friction angle (φ), cohesion (c), crack damage stress ratio (σ_cd/σ_c), and compressive–tensile strength ratio (σ_c/σ_t). Based on these analyses, a quantitative relationship model between the macro and micro parameters was established and validated through numerical simulation and experimental comparison. The proposed method provides a theoretical foundation for the mechanical modeling of sandstone and the inversion of microscopic parameters. Full article

The accurate description of plasticity and fracture behavior is essential in numerically investigating the mechanical responses of high-strength bolts under tension, shear and coupling loads. However, based on the von Mises criterion, inputting the constitutive relation and damage model from the tensile coupon test into the finite element method cannot properly predict the shear behavior of high-strength bolts. Cylindrical tensile coupons and shear specimens of common and weathering high-strength bolts are tested to obtain the complete tensile and shear responses. The combined S-V model and the modified shear constitutive model are collaboratively used to calibrate and describe the tensile and shear constitutive relations of high-strength bolts, and then the Bao–Wierzbicki model is used to predict the tensile and shear fracture behaviors. Furthermore, the collaborating method is used to discuss the applicable range of tensile and shear constitutive models for high-strength bolts under a tensile–shear coupling load, based on numerical analysis against available experimental data in the literature. The loading angle of 30° along the bolt rod is defined as the cut-off to differentiate high-strength bolts under a tensile- or shear-dominated state, and the corresponding mechanical responses of high-strength bolts can be predicted well based on the tensile and shear constitutive models, respectively. Full article

Granite is the main rock type in hot dry rock reservoirs, and hydraulic fracturing is always required during the process of geothermal production. It is necessary to understand the strength parameters and failure criterion of granite after high-temperature and water-cooling treatment. In this paper, laboratory uniaxial and triaxial compression experiments are carried out on granite samples after high-temperature and water-cooling treatment. Combined with some experimental data collected from pre-existing studies, the variation behaviors of cohesion (c), the internal friction angle ($\phi$) and tensile strength $\left({\sigma }_{\mathrm{t}}\right)$ are systematically studied considering the heating and cooling treatment. It is found that c and $\phi$ generally show two different types of variation behaviors with the increasing heating temperature. Tensile strength decreases in a similar way for the different granite samples with the increasing treatment temperature. Empirical equations are provided to describe these strength parameters. Finally, a modified Mohr–Coulomb failure criterion with a “tension cut-off” is established for the granite samples, considering the effects of high-temperature and water-cooling treatment. This study should be helpful for understanding the mechanical behavior of hot dry rock during hydraulic fracturing in geothermal production, and the proposed failure criterion can be applied for the numerical modeling of reservoirs. Full article

In contrast to brittle normal-strength concrete (NSC), high-performance steel-fiber-reinforced concrete (HPSFRC) provides better tensile and shear resistance, enabling enhanced bridge girder design. To achieve a balance between cost efficiency and quality, reducing conventional reinforcement is a viable cost-saving strategy. This study focused on the flexural behavior of a type of pre-tensioned precast HPSFRC girder without longitudinal and shear reinforcement. This type of girder consists of HPSFRC and prestressed steel strands, balancing structural performance, fabrication convenience, and cost-effectiveness. A 30.0 m full-scale girder was randomly selected from the prefabrication factory and tested through a four-point bending test. The failure mode, load–deflection relationship, and strain distribution were investigated. The experimental results demonstrated that the girder exhibited ductile deflection-hardening behavior (47% progressive increase in load after the first crack), extensive cracking patterns, and large total deflection (1/86 of effective span length), meeting both the serviceability and ultimate limit state design requirements. To complement the experimental results, a nonlinear finite element model (FEM) was developed and validated against the test data. The flexural capacity predicted by the FEM had a marginal 0.8% difference from the test result, and the predicted load–deflection curve, crack distribution, and load–strain curve were in adequate agreement with the test outcomes, demonstrating reliability of the FEM in predicting the flexural behavior of the girder. Based on the FEM, parametric analysis was conducted to investigate the effects of key parameters, namely concrete tensile strength, concrete compressive strength, and prestress level, on the flexural responses of the girder. Eventually, design recommendations and future studies were suggested. Full article

Glass fiber reinforced polypropylene composite plates have gradually attracted more attention because of their repeated molding, higher toughness, higher durability, and fatigue resistance compared to glass fiber reinforced thermosetting composites. In practical engineering applications, composite plates have to undergo bending effect at different angles in corrosive environment of concrete, including bending bars from 0~90°, and stirrups of 90°, which may lead to long-term performance degradation. Therefore, it is important to evaluate the long-term performance of glass fiber reinforced polypropylene composite bending plates in an alkali environment. In the current paper, a new bending device is developed to prepare glass fiber reinforced polypropylene bending plates with the bending angles of 60° and 90°. It should be pointed out that the above two bending angles are simulated typical bending bars and stirrups, respectively. The plate is immersed in the alkali solution environment for up to 90 days for long-term exposure. Mechanical properties (tensile properties and shear properties), thermal properties (dynamic mechanical properties and thermogravimetric analysis) and micro-morphology analysis (surface morphology analysis) were systematically designed to evaluate the influence mechanism of bending angle and alkali solution immersion on the long-term mechanical properties. The results show the bending effect leads to the continuous failure of fibers, and the outer fibers break under tension, and the inner fibers buckle under compression, resulting in debonding of the fiber–matrix interface. Alkali solution (OH⁻ ions) corrode the surface of glass fiber to form soluble silicate, which is proved by the mass fraction of glass fiber decreased obviously from 79.9% to 73.65% from thermogravimetric analysis. This contributes to the highest degradation ratio of tensile strength was 71.6% (60° bending) and 65.6% (90° bending), respectively, compared to the plate with bending angles of 0°. A high curvature bending angle (such as 90°) leads to local buckling of fibers and plastic deformation of the matrix, forming microcracks and fiber–resin interface bonding at the bending area, which accelerates the chemical erosion and debonding process in the interface area, bringing about an additional maximum 10.56% degradation rate of the shear strength. In addition, the alkali immersion leads to the obvious degradation of storage modulus and thermal decomposition temperature of composite plate. Compared with the other works on the long-term mechanical properties of glass fiber reinforced polypropylene, it can be found that the long-term performance of glass fiber reinforced polypropylene composites is controlled by the corrosive media type, bending angle and immersion time. The research results will provide durability data for glass fiber reinforced polypropylene composites used in concrete as stirrups. Full article

Marine risers are essential for offshore resource extraction, yet traditional metal risers encounter limitations in deep-sea applications due to their substantial weight. Fiber-reinforced polymer (FRP) composites offer a promising alternative with advantages including low density and enhanced corrosion/fatigue resistance. However, FRP risers remain susceptible to fatigue damage from vortex-induced vibration (VIV). Therefore, this study investigated VIV behavior of FRP composite risers considering the coupled effect of tensile-flexural moduli, top tensions, slenderness ratios, and flow velocities. Through an orthogonal experimental design, eighteen cases were analyzed using multivariate nonlinear fitting. Results indicated that FRP composite risers exhibited larger vibration amplitudes than metal counterparts, with amplitudes increasing to both riser length and flow velocity. It was also found that the optimized FRP configuration demonstrated enhanced fiber strength utilization. Parameter coupling analysis revealed that the multivariate nonlinear fitting model achieved sufficient accuracy when incorporating two coupled parameters, with the most significant interaction occurring between flexural modulus and top tension. Full article

Steel-fiber-reinforced geopolymer recycled-aggregate concrete (SFGRC) represents a promising low-carbon building material, yet data on its bond behavior remains scarce, limiting its structural application. To study the mechanical properties and bond strength of SFGRC, five groups of different mix proportions were designed. The main variation parameters were the content of recycled aggregate and the volume content of steel fiber. The cube compressive strength, splitting tensile strength, and flexural strength tests of SFGRC were completed. The influence law of different anchorage lengths on the bond strength between steel bars and SFGRC was studied through the central pull-out test. A multi-parameter probability prediction model of bond strength based on Bayesian method was established. The results show that with the increase of the content of recycled aggregate, the compressive strength of the specimen shows a downward trend, but the tension-compression ratio is increased by 18–22% compared to concrete with natural aggregates at equivalent strength grades. The content of steel fiber can significantly improve the mechanical properties of SFGRC. The bond strength between steel bars and SFGRC is 14.82–17.57 MPa, and the ultimate slip is 0.30–0.38 mm. A probability prediction model of ultimate bond strength is established based on 123 sets of bond test data. The mean and covariance of the ratio of the predicted value of the probability model to the test value are 1.14 and 2.61, respectively. The model has high prediction accuracy, and continuity and can reasonably calculate the bond strength between steel bars and SFGRC. The developed Bayesian model provides a highly accurate and reliable tool for predicting SFGRC bond strength, facilitating its safe and optimized design in sustainable construction projects. Full article

The shear strength of a steel shear wall (SSW) is typically governed by the yield strength of the steel. However, changes in mechanical properties beyond yielding—particularly those related to steel hardening and the effects of gravity loads—are not yet fully understood. These factors are critical for accurately assessing the shear capacity of SSWs during seismic events. In the current study, a method to calculate the shear force–displacement curve of a steel shear wall while considering the compression effect is presented, which incorporates both steel hardening and gravity effects. The analysis derives strains in tensile strips undergoing shear deformation using a strip model. Corresponding stresses are then determined using the stress–strain relationships obtained from tensile tests of the steel. Furthermore, the vertical stress induced by gravity loads is modeled using a three-segment distribution proposed before. For each tensile strip, the tension field stress is calculated by accounting for reductions due to vertical stress and the influence of steel hardening through the von Mises yield criterion. This approach enables the development of a shear force–displacement curve, which is subsequently validated against results from an experimentally verified finite element model. The findings demonstrate that the pushover curves predicted by this method closely align with those obtained from finite element analysis. Notably, the results indicate that the shear strength provided by the CAN/CSA-S16-01 equation may be overestimated by approximately 4%, 9%, and 18% when the vertical compression stresses are 50, 100, and 150 MPa for a wall with a slenderness of 150, respectively. Full article

This narrative review aims to provide an in-depth understanding of the biomechanical consequences of medial meniscus posterior root tears (MMPRTs), with a particular focus on the role of hoop tension in meniscal function. By revisiting fundamental principles such as load transmission, contact mechanics, and structural stabilization, this review elucidates how MMPRTs compromise both the integrity and function of the knee joint. The disruption of hoop tension is analyzed across various tear patterns, and through a synthesis of biomechanical experiments, the superiority and necessity of anatomical structural restoration over conservative management or meniscectomy are emphasized. A comprehensive grasp of these biomechanical foundations offers a critical perspective on the pathomechanics of MMPRTs and serves as a basis for more rational, evidence-based surgical decision-making in clinical practice. Full article

This paper investigates nine PVA fiber-reinforced cementitious composites with varying fiber content (1–2.5%) and types (oil-coated and non-coated). The experimental compositions utilize locally available cement, high volumes of fly ash, silica fume, PVA fibers, and a superplasticizer, entirely omitting natural aggregates. Key parameters evaluated include bulk density, compressive strength, secant modulus of elasticity, flexural tensile strength, fracture energy, and structural design applicability. The results show that FRCs without natural aggregates achieves significantly lower densities (1500–1720 kg/m³). Compressive strength is influenced by matrix density, with the highest value recorded at 30.98 MPa. The high fly ash content reduces the secant modulus of elasticity, while flexural tensile strength follows a similar pattern to compressive strength. Oil-coated fibers generally lower fracture energy, except for the 1.5% PVA content, where the 2.5% composition performs best. All specimens exhibit tension softening rather than the strain-hardening behavior of ECCs. Structural design equations were developed, though experimental validation is necessary. The 2.5% PVA composition increases the compression zone height by 7% while requiring 2% more reinforcement. As a sustainable alternative to conventional concrete, the composites offer promising mechanical properties and structural viability for construction applications. Full article

To overcome the limitation of traditional elastic phase field models that neglect plastic deformation in rock compressive-shear failure, this study developed an elastoplastic phase field fracture model incorporating plastic strain energy and established a coupling framework for plastic deformation and crack evolution. By introducing the non-associated flow rule and plastic damage variable, an energy functional comprising elastic strain energy, plastic work, and crack surface energy was constructed. The phase field governing equation considering plastic-damage coupling was obtained, enabling the simulation of the energy evolution in rock from the elastic stage to plastic damage and unstable failure. Validation was carried out through single-edge notch tension tests and uniaxial compression tests with prefabricated cracks. Results demonstrate that the model accurately captures characteristics such as the linear propagation of tensile cracks, the initiation of wing-like cracks under compressive-shear conditions, and the evolution of mixed-mode failure modes, which are highly consistent with classical experimental observations. Specifically, the model provides a more detailed description of local damage evolution and residual strength caused by stress concentration in compressive-shear scenarios, thereby quantifying the influence of plastic deformation on crack driving force. These findings offer theoretical support for crack propagation analysis in rock engineering applications, including hydraulic fracturing and the construction of underground energy storage caverns. The proposed plastic phase field model can be effectively utilized to simulate rock failure processes under complex stress states. Full article

Understanding the tensile properties of extraocular muscles (EOMs) is crucial for successful strabismus surgery and accurate predictions of surgical outcomes. Assessments of EOM tensile strength are traditionally highly dependent on the expertise of the ophthalmic surgeon, since they involve manually pulling the EOM in opposite directions. This approach only provides subjective measurements that are not quantifiable. Previous quantitative approaches have utilized various devices such as implanted force transducers or dial tension gauges connected to muscle tendons with nylon sutures, but these methods are complex and so are rarely used outside of research settings. Consequently, the goal of this study was to create a quantitative and clinically applicable device for assessing EOM tensile strength. This developed device uses a strabismus hook connected to a strain gauge load cell that measures the tensile force and includes a tilting sensor to ensure that the hook is pulled at a consistent angle when a force is applied. The performance of the device was tested on 22 EOMs in 11 patients with intermittent exotropia during surgery for resecting the medial rectus (MR) and recessing the lateral rectus (LR) under general anesthesia. The measured tensile strengths of the MR and LR were 284.9 ± 58.3 and 278.3 ± 64.6 g (mean ± SD), respectively. In conclusion, the novel device developed in this study for quantitative measurements of EOM tensile strength in clinical settings will facilitate understanding of the pathophysiology of strabismus, as well as of the mechanical properties of the EOMs, and enhance the precision of surgical interventions. Full article