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NiTi wires used for biological implants demonstrated ductile fracture. NiTi 40, 60, and 90 µm thick wires were tested in uniaxial tension to fracture and loading-unloading. Uniaxial stress-strain curves demonstrate superelastic behavior. The inelastic martensite transformation strain is completely recovered upon unloading, forming thermo-mechanical hysteresis. A mathematical model was developed to describe superelasticity effects in NiTi wires. Modeling results are qualitatively and quantitatively similar to experimental data, and capture elastic deformation of austenite, forward martensite phase transformation stress plateau before the onset of martensite elastic deformation and the entire unloading range. The elastic limit and strength increase with the wire thickness. [ABSTRACT FROM AUTHOR]

AbstractIt is one of the most advanced technologies to use automated fiber placement (AFP) to manufacture aero-engine composite blades. The layup sequence of composite blades has strong designability due to the variation of section thickness. In this article, tapered laminates are manufactured by AFP. The influence of different resin pockets and laying methods on the properties of tapered laminates are analyzed by tensile test, finite element modeling and macroscope images. The specimens are analyzed by failure mode, strength and crack propagation and suggestions for improvement are put forward. The results show that the resin pocket height and taper ratio have a great influence on the tensile strength. The 1:30 taper ratio has a higher strength than the 1:20 taper ratio, at least 54.22% higher. In addition, the crack near the thin end of the resin pocket is tend to cause cracks, and the delamination is also tend to reach this position. Experimental measurements and FEM results correlate very well. [ABSTRACT FROM AUTHOR]

The constituent recalcitrant color pigments and other organic pollutants (such as COD, and MLSS) in palm oil mill effluent (POME) are detrimental, yet the commonly employed conventional remediation method has been inefficient. This study focused on the development of an innovative hybrid membrane designed for efficient decolorization and separation of pollutants. The research involves the incorporation of magnesium oxide (MgO) nanoparticles at a varied loading (0.0–0.75 wt%) into polyvinylidene fluoride (PVDF) and polyethylene-glycol (PEG) hollow-fiber using blending dry-jet wet-swirling phase inversion technique. Initially, the crystallinity and purity of the MgO were examined using X-ray diffraction before the application. Then, morphological characteristics, elemental constituents, mechanical strength, and thermal stability of the resultant membranes were examined using Scanning Electron Microscopy, Energy Diffraction X-ray, tensile loading, and thermogravimetric analysis. The performance results indicated that the membrane sample with the nanoparticles MgO-0.50wt% demonstrated superior mechanical and thermal stability, as well as separation performance. The membrane was able to remove the colorants, COD, suspended solids, total nitrogen, and turbidity by 80.05, 94.10, 98.67, 87.02, and 96.01 %, respectively. Additionally, the sample has the highest flux recovery ratio of 0.929 (or 92.9 %) with a minimal irreversible fouling ratio of 0.071 (or 7.1 %). The regeneration and reusability analysis indicates that at the end of the 4th filtration cycle, the modified membrane (0.50 wt% MgO) exhibited only a 23.22 % reduction in permeability flux. This finding suggests that the nanoparticles MgO 0.50wt% PVDF/PEG sample is a promising technology for POME treatment.

Fatigue strength of concrete decks for large composite bridges In the support area of large composite bridges, tensile stresses occur in the concrete deck slab due to the negative bending moment of the main girders, leading to cracks in the concrete deck. Transverse steel cantilever beams are arranged under the deck at the transverse frame spacing in order to support e. g. prefabricated concrete elements, so that the deck slab predominantly spans in the longitudinal direction. Cyclic transverse forces due to local wheel loads caused by high variable traffic loads must then be transferred to the cross girders via the cracked concrete slab, as a result of the tensile loading. Up to now, no tests have been carried out to determine the fatigue strength of the cracked concrete deck slab. Based on tests from the literature (whereby so far only well documented tests without longitudinal tensile loading have been available) and own experiments (with longitudinal tensile loading), a database has been developed which formed the basis for the derivation of S‐N‐lines and which allowed the evaluation of the influence of specific parameters on the fatigue strength. Since the fatigue strength of reinforced concrete elements without shear reinforcement is dependent on the static load‐bearing capacity, the influence of the scatter of the static shear capacity on the fatigue strength is discussed in particular. Based on the results and the current state of standardization, a design concept for the fatigue strength of the concrete deck slab is presented. [ABSTRACT FROM AUTHOR]

Recently, Co–Cr–Ni medium-entropy alloys (MEAs) have garnered significant attention in the materials field owing to exceptional properties. However, the various mechanisms of transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP) effects with variation of chemical compositions, strain rates, temperature and grain size in polycrystalline Co–Cr–Ni MEAs remains challenging. By utilizing molecular dynamics simulations, the uniaxial tensile deformation of polycrystalline Co–Cr–Ni MEAs, including equiatomic CoCrNi, and non-equiatomic Co10(CrNi)90, Cr10(CoNi)90 and Ni10(CoCr)90, has been investigated. The influence of strain rates and deformation temperatures on the mechanical properties and deformation mechanisms of CoCrNi MEA has also been explored under uniaxial tensile loading. Further, dislocation multiplication, slip motion, microstructure evolution, and their interplay with tensile deformation under different conditions have also been studied. Additionally, the relationship between different grain sizes and the flow stress of polycrystalline CoCrNi MEA has also been discussed. The findings reveal that Co10(CrNi)90 MEA exhibits highest yield stress, Young's modulus, and flow stress. While CoCrNi MEA and Cr10(CoNi)90 MEA with equiatomic ratios display similar mechanical properties, Ni10(CoCr)90 MEA demonstrates superior ductility owing to the strong TWIP and TRIP effects. Besides, strain rate, deformation temperature, and grain size all have significant impacts on the deformation mechanisms of polycrystalline CoCrNi MEA.

To investigate the effect of crack angle on the fracture performance of brittle materials under tensile load, a molecular dynamics simulation method based on ReaxFF is used to establish an amorphous silica model through the high-temperature melting and annealing process. Under the simulation environment of 300 K, 1.013 × 105 Pa and 5 × 109 s−1, the impact of crack angle on the fracture performance of the model from three perspectives is analyzed: material mechanical properties, micro fracture process, and energy evolution. The result indicates that as the crack angle increases, the ultimate strain and stress of the model decrease accordingly. The crack propagation path of the model will exhibit a "Z" shape due to the coupling effect of tensile and shear stress. The elastic energy efficiency and new surface energy efficiency of the model increase with the increase in crack angle, and the most new surface is generated at 45° crack angle. The linear regression model and asymptotic regression model are used to fit the trends of elastic energy efficiency and new surface energy efficiency with crack angle, respectively, with correlation coefficients R2 of 0.986 and 0.994. In the actual comminution process, the input energy required for crushing as well as the surface area and morphology of the material after crushing can be changed by adjusting the angle between the load and the main crack of the material being broken. [ABSTRACT FROM AUTHOR]

Biomedical degradable materials would be subjected to different degrees and forms of static stress after being implanted in the human body. In this work, the biocorrosion behaviors of AZ31B magnesium alloy under different stress forms with different magnitudes (20 ∼ 150 MPa) were studied. It was found that the corrosion behaviors at stressed conditions were severer than those at unstressed conditions and corrosion rates were obviously accelerated. The biocorrosion behaviors are more sensitive to the effects of tensile loads than to compressive loads. A biocorrosion numerical model on the degradation process of Mg alloy under static loads was established. The corrosion current density (icorr) of Mg alloy and the applied static stress (σ) matches a linear relationship of ln icorr ∼ σ well during the early stage (within 24 hrs) while deviated gradually in the latter period of corrosion. This work could provide a guidance and theoretical reference for further researches on the biocorrosion behaviors and practical clinical applications of the biomedical materials subjected to physiological loads.

Durability of concrete with supplementary cementitious materials (SCMs) is crucial to the longevity of our built environment. Current research on the carbonation performance of concrete focuses on determining changes in microstructure induced by the chemical and physical interactions of CO2 with the cement phase in samples that do not undergo loading. Although this approach has enabled us to understand the chemical carbonation durability of concrete, the deterioration process is certainly not realistic considering the in-service conditions of structural concrete. Therefore, five different laboratories from RILEM TC 281-CCC WG4 conducted comparative testing of Portland cement concrete with/without SCMs under the combined action of carbonation and mechanical loading. The results indicated that the carbonation depth of concrete undergoing mechanical loading is lower in the case of a limited compressive load, and higher in the case of a high compressive load or tensile load, compared with unloaded specimens. The relative carbonation depth was decreased by 9–16% at 30% of the failure load in compression, independent of CO2 concentration and the presence of SCMs, while it was increased up to 13% at a 60% load level at most. Tension made the carbonation depth gradually increase, and up to 70% higher carbonation depth was reached at 60% of the tensile failure load. The combined effect of carbonation in concrete with SCMs and mechanical loading should therefore not be neglected in the service life prediction of concrete structures. [ABSTRACT FROM AUTHOR]

In this study, strain energy evolution characteristics of polycarbonate at different loading rates were measured under the tensile loading using infrared thermography. The variation of elastic strain energy, plastic strain energy and infrared radiation were analysed. The experimental results revealed that elastic strain energy and infrared radiation variation have a linear correlation, and the third power correlation between plastic strain energy and infrared radiation variation was obtained. Based on the principle of energy transfer and storage, the elastic strain energy infrared radiation coefficient and the plastic strain energy infrared radiation coefficient were proposed to quantitatively determine the elastic and plastic strain energy via infrared radiation. It is provided a valuable reference to predict and monitor the deformation and failure of polycarbonate based on the infrared thermography. [ABSTRACT FROM AUTHOR]

In many technical domains, adhesively bonded joints have been employed extensively. These joints perform poorly against peel stresses despite having good shear characteristics. A step-lap joint (SLJ) is one of the techniques used to reduce the peel stresses at the edges of the overlap area to avoid damages. In these joints, the butted laminations of each layer are successively offset in succeeding layers in the same direction. Bonded joints are subjected to cyclic loadings in addition to static loads. It is difficult to predict their fatigue life accurately; however, this information must be clarified to explain their failure characteristics. To this end, the fatigue response of an adhesively bonded step-lap joint subjected to tensile loading was investigated with the developed finite-element (FE) model. In the joint, toughened type DP 460 and A2024-T3 aluminium alloys were used for the adhesive layer and adherends, respectively. The cohesive zone model with static and fatigue damages were linked to each other and were used to represent the response of the adhesive layer. The model was implemented using an ABAQUS/Standard user-defined UMAT subroutine. Experiments found in the literature served as a basis for validating the numerical model. The fatigue performance of a step-lap joint for various configurations subjected to tensile loading was examined thoroughly. [ABSTRACT FROM AUTHOR]

Featured Application: This paper presents an experimental and analytical methodology for the mechanical characterization of metal anchors in ancient brick masonry walls. The presented results contribute to the identification of the most efficient anchoring systems for strengthening and retrofitting of historical brick masonry structures. The repair and strengthening of historical masonry buildings is a fundamental aspect in the conservation of the built cultural heritage. Temporary shoring or strengthening are often used and, usually, involve the introduction of new metallic elements. The connection between the original substrate and the new elements must be analyzed carefully to prevent further damage to the building. This paper presents a study on the mechanical behavior of metal anchors applied to brick masonry walls. An experimental campaign is developed, and a series of pull-out tests are carried out on masonry walls built in a laboratory with natural hydraulic lime mortar and low mechanical strength bricks. Two groups of tests are conducted, namely, with the actuator in the direction of the anchor axis and with the actuator inclined with respect to the fastener axis. Moreover, two types of anchoring systems are used, namely, adhesive (chemical and cementitious grout) and mechanical anchors. The experimental results are compared to predictive analytical formulas available in the literature for estimation of the ultimate load capacity, according to the type of failure. From the comparison between experimental and analytical values, it is proven that the analytical formulation originally developed for concrete substrates cannot be directly extrapolated to brick masonry cases, and specific predictive formulas should be developed. The presented research can be used to select the most efficient anchoring system for strengthening and retrofitting of historical brick masonry structures. [ABSTRACT FROM AUTHOR]

Biomedical degradable materials would be subjected to different degrees and forms of static stress after being implanted in the human body. In this work, the biocorrosion behaviors of AZ31B magnesium alloy under different stress forms with different magnitudes (20 ∼ 150 MPa) were studied. It was found that the corrosion behaviors at stressed conditions were severer than those at unstressed conditions and corrosion rates were obviously accelerated. The biocorrosion behaviors are more sensitive to the effects of tensile loads than to compressive loads. A biocorrosion numerical model on the degradation process of Mg alloy under static loads was established. The corrosion current density (i corr) of Mg alloy and the applied static stress (σ) matches a linear relationship of ln i corr ∼ σ well during the early stage (within 24 hrs) while deviated gradually in the latter period of corrosion. This work could provide a guidance and theoretical reference for further researches on the biocorrosion behaviors and practical clinical applications of the biomedical materials subjected to physiological loads. [ABSTRACT FROM AUTHOR]

In recent years, it has been demonstrated that the lightweight potential of load-carrying structural components could be further enhanced using additive manufacturing technology. However, the additive manufacturing process offers a large parameter space that highly impacts the part quality and their inherent mechanical properties. Therefore, the most influential parameters need to be identified separately, categorised, classified and incorporated into the design process. To achieve this, the reliable testing of mechanical properties is crucial. The current developments concerning additively manufactured lattice structures lack unified standards for tensile testing and specimen design. A key factor is the high stress concentrations at the transition between the lattice structure and the solid tensile specimen's clamping region. The present work aims to design a topology-optimised transition region applicable to all cubic unit cell types that avoids high samples potentially involved in structural grading. On the basis of fulfilling the defined objective and satisfying the constraints of the stress and uniaxiality conditions, the most influential parameters are identified through a correlation analysis. The selected design solutions are further analysed and compared to generic transition design approaches. The most promising design features (compliant edges, rounded cross-section, pillar connection) are then interpreted into structural elements, leading to an innovative generic design of the load introduction region that yields promising results after a proof-of-concept study. [ABSTRACT FROM AUTHOR]

The real physiological environment of the human body is complicated, with different degrees and forms of loads applied to biomedical implants caused by the daily life of the patients, which will definitely influence the degradation behaviors of Mg-based biodegradable implants. In the present study, the degradation behaviors of modified WE43 alloys under the combination of torsional and tensile stress were systematically investigated. Slow strain rate tensile tests revealed that the simulated body fluid (SBF) solution could deteriorate the ultimate tensile stress of WE43 alloy from 210.1 MPa to 169.2 MPa. In the meantime, the fracture surface of the specimens tested in the SBF showed an intergranular corrosion morphology in the marginal region, while the central area appeared not to have been affected by the corrosive media. The bio-degradation performances under the combination of torsional and tensile stressed conditions were much more severe than those under unstressed conditions or single tensile stressed situations. The combination of 40 MPa tensile and 40 MPa torsional stress resulted in a degradation rate over 20 mm/y, which was much higher than those under 80 MPa single tensile stress (4.5 mm/y) or 80 MPa single torsional stress (13.1 mm/y). The dynamic formation and destruction mechanism of the protective corrosion products film on the modified WE43 alloy could attribute to the exacerbated degradation performance and the unique corrosion morphology. The dynamic environment and multi-directional loading could severely accelerate the degradation process of modified WE43 alloy. Therefore, the SCC susceptibility derived from a single directional test may be not suitable for practical purposes. Complex external stress was necessary to simulate the in vivo environment for the development of biodegradable Mg-based implants for clinical applications. [ABSTRACT FROM AUTHOR]

Two advanced high-strength steels (AHSSs) with varying percentages of bainite present in the microstructure were examined for their deformation behaviour under tensile loading. Despite having comparable yield strength (680–700 MPa) and tensile strength (775–780 MPa), the two steels behaved differently in terms of deformation and damage during tensile loading. The strengthening mechanism was governed by the combined effect of precipitates and the harder bainite phase. Also, the two steels’ strain-hardening behaviour differed. At the early stages of the deformation, the amount of harder bainite phase determined the strain hardening rate, however, in the later stages, the strain hardening rate became sluggish and gradual due to restricted mobility of the dislocations caused by the nano-precipitates. This phenomenon was further confirmed by the EBSD and KAM maps, revealing differences in grain misorientation resulting from the deformation. Overall, steel with a reduced volume fraction of bainite phase demonstrated a ductile fracture behaviour in contrast to the steel with a predominantly bainitic microstructure. In this case, the quasi-cleavage kind of fracture was discovered. [ABSTRACT FROM AUTHOR]

The micromechanical behavior of an Al/Al2Cu/Cu multilayer with characteristic crystal orientation during uniaxial tensile deformation was investigated by molecular dynamics. The simulation results showed that under tensile loading, the dislocation nucleates at the Cu/Al2Cu heterogeneous interface and moves toward the Cu layer along the {111} crystal plane. The deformation mechanism is intralayer confinement slip. As the dislocations proliferated, interactions between them occurred; resulting in the formation of insertion stacking faults and deformation twins in the Cu and Al layers. However, no dislocation lines were generated in the Al2Cu layer during tensile deformation. As the load increased, the stress concentration at the Al2Cu/Al interface led to the fracture of the complex. In addition, the microplastic deformation mechanism and mechanical properties of Al/Al2Cu/Cu composites at different temperatures and strain rates were significantly different. These results revealed the microdeformation mechanism of laminated composites containing brittle phases.

In this paper, the effect of aluminum oxide, Al2O3, nanoparticles' inclusion into Epocast 50-Al/946 epoxy adhesive at different temperatures, subjected to quasi-static tensile loading, is numerically investigated. The single-lap adhesive joint with two different types of material adherends (composite fiber-reinforced polymer (CFRP) and aluminum (Al) 5083 adherends) and adhesive Epocast 50-A1/hardener 946 were modeled in ABAQUS/CAE. A numerical methodology was proposed to analyze the effect on peel stress and shear stress by adding Al2O3 nanoparticles into the neat adhesive at 25 °C, 50 °C, and 75 °C temperatures at four different locations of the adhesive regions: the interface of the adhesive and aluminum adherend (location A), the middle plane of the adhesive region (location B), the middle longer edge (along the length of the adhesive, location C), and the middle shorter edge (along the width of the adhesive, location D). The results showed that adding nanoparticles into the neat adhesive improves joint strength at room and elevated temperatures. High peel and shear stresses were recorded near both edges of the locations (A, B, C, and D). For location A, adding nanofillers into the adhesive resulted in the reduction in peak peel stress by 1.3% for 25 °C; however, it increased by 2.7% and 10.7% for 50 °C and 75 °C temperatures, respectively. Furthermore, the peak shear stress observed a considerable reduction of 19.6% for 25 °C, but it increased by 7.7% and 8.7% for 50 °C and 75 °C temperatures, respectively, for location A. The same trend was also observed for other locations (i.e., B, C, and D). This signified that adding aluminum oxide nanoparticles in the adhesive resulted in increased stiffness at higher temperatures and increased ductility of the joint, as compared to the joint with neat adhesives at room temperature. Moreover, it was observed that locations A and B were more vulnerable to damage initiation, as the peak of stresses lay near the edges, indicating that the crack initiation would take place close to the edges and propagate towards the center, leading to ultimate failure. [ABSTRACT FROM AUTHOR]

This paper presents a modified re-entrant honeycomb auxetic structure. The structure is constructed by adding an additional horizontal member between the vertical and re-entrant member of the semi-re-entrant honeycomb model to increase the overall compliance of the structure in order to obtain higher values of negative Poisson's ratio (NPR). An analytical model of the structure is presented, taking into account the bending, shear, and axial deformations. The model is verified using finite element analysis (FEA) and tensile testing. The results of FEA and tensile testing corroborate the results of the presented mathematical model. The structure is also compared to the existing re-entrant honeycomb structure. The newly added strut has shown a direct effect on the directional properties of the overall structure. With an increase in the newly added strut to re-entrant lengths, NPR was significantly enhanced in the x-direction and reduced in the y-direction loadings. The structure shows an improved Young's modulus compared to solid material in both loading directions, especially for the low values of the new strut and re-entrant lengths ratio. The structure also shows that high NPR can be achieved for low relative density compared to semi re-entrant honeycomb structure. [ABSTRACT FROM AUTHOR]

Al-Cu Nanocomposites (NCs) are widely used in industrial applications for their high ductility, light weight, excellent thermal conductivity, and low-cost production. The mechanical properties and deformation mechanisms of Metal Matrix NCs (MMNCs) strongly depend on the matrix microstructure and the interface between the matrix and the second phase. The present study relies on Molecular Dynamics (MD) to investigate the effects of temperature on the mechanical properties and elastic and plastic behavior of the Al-Cu NC with single-crystal and polycrystalline matrices. The effects of heating on microstructural defects in the aluminum matrix and the Al/Cu interface were also addressed in the following. It was found that the density of defects such as dislocations and stacking fault areas are much higher in samples with polycrystalline matrices than those with single-crystal ones. Further, by triggering thermally activated mechanisms, increasing the temperature reduces the density of crystal defects. Heating also facilitates atomic migration and compromises the yield strength and the elastic modulus as a result of the increased energy of atoms in the grain boundaries and in the Al-Cu interface. The results showed that the flow stress decreased in all samples by increasing the temperature, making them less resistant to the plastic deformation.

To investigate mechanical properties of Ti6321 titanium alloy, tensile tests at different strain rates are carried out. The changes of microstructure and properties at the range of 10−3 s−1–105 s−1 have been studied. Lower density and larger size of dimples produce when stretched at high strain rates of 103 s−1 compared to quasi-static stretching. The yield strengths of the alloy are 805, 1096 and 2440 MPa at strain rates of 10−3 s−1, 2 × 103 s−1 and 105 s−1, respectively with obvious strain rate strengthening effect. At 105 s−1 strain rate, parallel twins generate at grain boundaries to coordinate the deformation when dislocations cannot meet indicating the twinning mechanism comes into play. [ABSTRACT FROM AUTHOR]

Since the physical and mechanical properties of semicrystalline polymers strongly depend on crystalline morphology, understanding the correlation between the crystallization kinetics and crystalline structure of polythene is beneficial for their rational processing and applications. In this study, united-atom (UA) molecular dynamics (MD) simulations were employed to elucidate the variations in crystalline structure, phase transition temperatures, and uniaxial tensile deformation among polyethylene (PE) with randomly oriented and flow-induced crystallization (FIC). The results showed that crystallization occurs in areas with low potential energy. For the FIC process, the entanglement parameter and interplanar spacing was less than for randomly oriented crystallization, and the crystallinity was higher. The relationship between the deformation and the crystallinity of PE with randomly oriented crystallization was expressed, which indicates that the crystalline structure promoted elongation at break of PE in tensile deformation. As PE was oriented to crystallize during the FIC process, the polymer stiffness is positively correlated with the deformation ratio of the PE model, so crystal conformation systems with higher deformation ratios produce higher ultimate stresses in tensile loading. From the visualization results, the crystalline phase was stable and does not easily transform into an amorphous phase during tensile loading. Additional results show that the fracture region of PE at tensile fracture tends to develop in the amorphous phase under tensile loading. Energy analysis showed that the elastic and yield regions were mainly dominated by intra-chain bonds, angles, and dihedral motion of PE, whereas interchain nonbonded interactions mainly dominated strain-hardening regions. [Display omitted] • Flow-induced crystallization (FIC) enhances PE system crystallinity, reducing interplanar spacing. • Highly deformed PE systems exhibit elevated phase transition temperatures after FIC process. • Crystallinity and orientation influence stress-strain behavior in PE during uniaxial tensile testing. • Non-bond energy played a crucial role in PE during tensile loading process. [ABSTRACT FROM AUTHOR]

The nanocrystalline metal material has been an investigation hotspot due to its excellent mechanical property. The high content of grain boundaries (GBs) in microstructure is the key factor affecting its fracture behavior during service. Therefore, it is essential to investigate the effect mechanism of nanoscale GB on crack propagation. In this study, four molecular dynamics (MD) models of nanocrystalline aluminum (Al) with different GB contents are established. The results show that the high‐content GBs in polycrystals can increase the toughness and absorb energy, reducing the risk of brittle crack propagation. The presence of GB can reduce the stress concentration of the crack, and the dislocation emission from the crack tip can be absorbed by the front GB. The microstructure with high‐content GBs can actuate more plastic deformation mechanisms such as multiple slips, GB slip, and migration. The region with more GBs can induce a more even deformation of the whole microstructure by means of dislocation emission and GB migration to the region with fewer GBs. The purpose of this study is to provide a rational mechanism reference for the failure of nanocrystalline metal material. [ABSTRACT FROM AUTHOR]

This paper presents a modified high-accuracy empirical formula for the strain concentration factor in a centrally-placed countersunk holes in isotropic plate under uniaxial tension. Finite Element Method (FEM) was used to investigate the effect of the problem geometric parameters including, plate width and thickness, as well as the hole radius, countersinking depth and angle on the strain concentration factor. The important influence of Poisson's ratio was also thoroughly discussed. Based on the FEMgenerated data and nonlinear regression, a general and high-precision equation for the strain concentration factor was developed. The formulation process was based on producing a general formula for computing the strain concentration factor with unknown coefficients. Such coefficients are determined by minimizing the relative error between the fitted equation and the FE data using nonlinear least squares method. The results of this newly-developed equation were validated with FEA. The comparison showed high accuracy of the present equation in evaluating strain concentration factor in countersunk holes with a relative approximate error of less than 7%. Besides, this equation was efficiently employed to test the various geometric and material parameters on the strain concentration value of countersunk holes. The results of the present equation were compared to the results of older equation available in literature. The comparison proved much higher accuracy of the present equation in evaluating strain concentration factor especially for deeper and larger countersunk holes than the previously published formula. [ABSTRACT FROM AUTHOR]

Understanding the tensile behavior of geosynthetic reinforcement materials at different temperatures is essential for the design of reinforced soil structures in seasonally cold regions. This study describes a series of tensile tests performed on two polypropylene geogrid materials, namely a biaxial geogrid and a geogrid composite. A total of 84 tests were performed in an environmental chamber with temperatures as low as −30°C and as high as +40°C. The response of each material is examined over the range of investigated temperatures to evaluate the effect of temperature changes on the tensile strength of the two geogrid materials. The response of the biaxial geogrid is found to be sensitive to temperature variations, with samples tested at low temperatures exhibiting brittle behavior characterized by high rupture strength and small ultimate strain while samples tested at elevated temperatures displayed ductile behavior with large elongation at failure and comparatively small rupture strength. A similar response was found for the geogrid composite, however, the rupture strength seemed to be less sensitive to temperature changes. The modes of failure observed at each temperature are examined based on photographic evidence taken during the experiments. [ABSTRACT FROM AUTHOR]

Understanding material behavior is key to discovering innovative applications in any field. Regardless of the exciting mechanical properties of polyurea, there has been a limited effort in studying the use of polyurea for structural retrofit and strengthening applications. This study aims to understand the behavior of polyurea under different tensile loading conditions to provide critical information towards enabling the future use of polyurea in structural applications. Several standard coupons are tested under various tensile loading conditions to understand the mechanical behavior of eight different commercial polyureas. The study provides the full stress–strain characteristic curves that can be used for constitutive modeling purposes. The results show that polyurea has a wide range of properties from low strength flexible nature to high strength rigid nature. All tested polyureas displayed some level of rate dependency, i.e., ultimate strength is a function of loading rates. The high-strength polyureas tested only show slight rate dependency and good strength retention under cyclic and fatigue tensile loading, suggesting that polyureas have promising mechanical properties for potential structural applications. [ABSTRACT FROM AUTHOR]

Screw micropiles or "ground screws" (diameter less than 200 mm, length less than 5 m) consist of a steel tubular shaft with continuous spiral threads, and a threaded tapered segment; the installation is achieved by rotary driving. Although ground screws are useful in many applications as well as environment-friendly, research on their behaviour is limited. The paper presents an experimental study on the response of screw micropiles subjected to tensile and compressive axial loading. Twenty full-scale load tests were conducted on four types of screws, with diameter 66-114 mm and length 0.8-1.6 m, at a test site in Italy, characterized by the presence of predominantly clayey soils. The micropiles achieved tensile and compressive capacities of 23-60 kN and 20-75 kN respectively, with pile movements in the range 1-9 mm. The results were interpreted in the light of a recently developed method to compute bearing capacity of screw micropiles. [ABSTRACT FROM AUTHOR]

This article investigates the interest of using in-situ piezoelectric (PZT and PVDF) disks to perform real-time Structural Health Monitoring (SHM) of glass fiber-reinforced polymer composites submitted to various tensile loadings. The goal is to evaluate the working range and SHM potential of such embedded transducers for relatively simple mechanical loadings, with the long-term aim of using them to monitor complete 3D structures submitted to more complex loadings. SHM is performed acquiring the electrical capacitance variation of the embedded transducers. To study the potential links between the in-situ capacitance signal and the global response of the loaded host specimens, a multi-instrumentation composed of external Nondestructive Testing techniques was implemented on the surfaces of the specimens to search for multi-physical couplings between these external measurements and the capacitance curves. Results confirmed the non-intrusiveness of the embedded transducers, and allowed estimating their working domain. PZT capacitance signal follows well the mechanical loadings, but the piezoceramic transducer gets damaged after a determined relatively low strain level due to its brittleness. The limits of this working domain are extended by using a stretchable PolyVinylidene Fluoride (PVDF) polymer transducer, allowing this one to perform in-situ and real-time SHM of its host tensile specimens until failure.

In recent years, it has been demonstrated that the lightweight potential of load-carrying structural components could be further enhanced using additive manufacturing technology. However, the additive manufacturing process offers a large parameter space that highly impacts the part quality and their inherent mechanical properties. Therefore, the most influential parameters need to be identified separately, categorised, classified and incorporated into the design process. To achieve this, the reliable testing of mechanical properties is crucial. The current developments concerning additively manufactured lattice structures lack unified standards for tensile testing and specimen design. A key factor is the high stress concentrations at the transition between the lattice structure and the solid tensile specimen’s clamping region. The present work aims to design a topology-optimised transition region applicable to all cubic unit cell types that avoids high samples potentially involved in structural grading. On the basis of fulfilling the defined objective and satisfying the constraints of the stress and uniaxiality conditions, the most influential parameters are identified through a correlation analysis. The selected design solutions are further analysed and compared to generic transition design approaches. The most promising design features (compliant edges, rounded cross-section, pillar connection) are then interpreted into structural elements, leading to an innovative generic design of the load introduction region that yields promising results after a proof-of-concept study.

The real physiological environment of the human body is complicated, with different degrees and forms of loads applied to biomedical implants caused by the daily life of the patients, which will definitely influence the degradation behaviors of Mg-based biodegradable implants. In the present study, the degradation behaviors of modified WE43 alloys under the combination of torsional and tensile stress were systematically investigated. Slow strain rate tensile tests revealed that the simulated body fluid (SBF) solution could deteriorate the ultimate tensile stress of WE43 alloy from 210.1 MPa to 169.2 MPa. In the meantime, the fracture surface of the specimens tested in the SBF showed an intergranular corrosion morphology in the marginal region, while the central area appeared not to have been affected by the corrosive media. The bio-degradation performances under the combination of torsional and tensile stressed conditions were much more severe than those under unstressed conditions or single tensile stressed situations. The combination of 40 MPa tensile and 40 MPa torsional stress resulted in a degradation rate over 20 mm/y, which was much higher than those under 80 MPa single tensile stress (4.5 mm/y) or 80 MPa single torsional stress (13.1 mm/y). The dynamic formation and destruction mechanism of the protective corrosion products film on the modified WE43 alloy could attribute to the exacerbated degradation performance and the unique corrosion morphology. The dynamic environment and multi-directional loading could severely accelerate the degradation process of modified WE43 alloy. Therefore, the SCC susceptibility derived from a single directional test may be not suitable for practical purposes. Complex external stress was necessary to simulate the in vivo environment for the development of biodegradable Mg-based implants for clinical applications.

The infrared (IR) thermography and acoustic emission (AE) monitoring are employed to evaluate the damaging process of C/SiC composite material bolts (M10) under tensile loading. The temperature variation over time before and after the breaking moment, as well as the temperature distribution near the fracture are investigated on the basis of real-time temperature evolution results obtained from IR analyzing. Multiple AE parameters including AE hits, duration time and energy are employed for comprehensive investigation on the failure mechanism based on the behavior of the fibers, matrix and the interphase. The results indicate that the IR signal mostly originates from the breaking process (lasting period less than 0.1 s) and localizes at the thread root (∼2 mm around the fracture) on the fixture surface. The histogram of AE activity indicates that the intensity of the crack propagation peaks at the middle stage of the tensile loading process, while the energy abruptly outbreaks at clustered and isolated loading forces, as a result of damage accumulation in the tensile loading process. The IR and AE results fit well with the microstructure of the fracture. The proposed in-situ evaluation method makes it possible to evaluate the real time damaging process and failure mechanism of C/SiC composite material bolts.

A molecular dynamics simulation-based study has been performed to examine the deformation behaviour of the predetermined parallel and perpendicular centreline cracks in CNTs embedded nanocrystalline aluminum (CNTs-NC Al) composite specimens under uniaxial loading. The hybrid potential (i.e. EAM, AIREBO, and LJ) method is adopted for carrying out the tensile deformation at three different temperatures (such as 10 K, 300 K, and 653 K). The mechanical properties are evaluated for both cases of parallel and perpendicular cracks of NC Al and CNTs-NC Al specimens. (30,30) CNT-NC Al specimen has shown superior fracture strain and ultimate tensile strength (UTS) at low temperature, whereas, higher fracture strain and lower UTS at high temperature than NC Al specimen. The mechanical properties of CNTs-NC Al nanocomposites are affected by the pre-existing crack and loading direction. The CNTs-NC Al nanocomposite specimens have exhibited the highest dislocation density compared to the NC Al specimen. The Shockley partial dislocations are a major driving factor for the parallel and perpendicular cracks of both (NC Al and CNTs-NC Al) specimens. The structural evolution and defect variation (such as stacking faults interaction with various dislocations, twin boundary, and grain boundary widening) has been elucidated during the tensile deformation of NC Al and CNT-NC Al nanocomposites. [ABSTRACT FROM AUTHOR]

Conventional tensile energy absorbers are often limited in their efficacy by erratic and unpredictable force responses. Additionally, the published literature on devices of this nature is sparser in comparison to compressive energy absorbers and hence engineers are further limited by a lack of existing designs. Axial cutting is an energy dissipating technology studied extensively under compressive loading with promising results. A novel apparatus was explored in this study to implement axial cutting under tensile loading; this is an application which sees significantly less attention in the open literature. An analytical modeling approach was utilized as a design tool to assess the specimens in this study and to precisely engineer energy absorbers with adaptive force responses. The tests were conducted quasi-statically utilizing a hydraulically powered testing apparatus with a capacity of 300 kN. AA6061-T6 and T4 extrusions were utilized with wall thicknesses ranging from 0.794 mm to 3.175 mm. Force responses with tensile force efficiencies between 85% and 92% were observed. Energy absorption values ranging from 2.2 kJ to 7.7 kJ and specific energy absorption values between 12 kJ/kg to 16 kJ/kg were measured, greatly exceeding the mechanical capabilities of multiple, established tensile energy dissipating solutions. Highly stable and repeatable deformation was observed between consecutive tests within most specimen categories. Numerical models were created utilizing LS-DYNAⓇ and average validation metrics and cumulative errors of approximately 0.90 and 0.09 were calculated, respectively, indicating excellent predictive capabilities.

Using a molecular dynamics (MD) simulation and an embedded atom method (EAM), this article aims to study the structural properties of five Cu‐ and Ag‐based metallic glasses (MGs) with different compositions (Cu75Ag25, Cu50Ag50, Ag75Cu25, Cu‐monatomic, and Ag‐monatomic MGs) to shed light on the effect of composition on MGs' properties. According to the radial distribution function (RDF) analysis, it is revealed that Ag atoms promote the glass forming ability (GFA) of the samples. Furthermore, increasing Ag content is found to favor the formation of face‐centered cubic (fcc) clusters and reduce the atomic fraction of icosahedral clusters, and this seems normal, because the distorted icosahedra are just an intermediate state between the icosahedra structure and the fcc structure as mentioned in the literature. Moreover, it is shown that Ag atoms tend to be at the center space of clusters with higher coordination numbers. It is also found that the obtained microstructure of the MGs, especially the full icosahedra, influences their mechanical response toward uniaxial tensile loading, as it enhances their strength by resisting to shear strain and reducing their plasticity, which encourages the accumulation of shear strain in shear bands. [ABSTRACT FROM AUTHOR]

Abstract Atomistic simulations are capable of providing insights into physical mechanisms responsible for mechanical properties of the transition metal of Tantalum (Ta). By using molecular dynamics (MD) method, temperature and pressure dependences of the elastic properties of Ta single crystals are investigated through tensile loading. First of all, a comparative study between two types of embedded-atom method (EAM) potentials is made in term of the elastic properties of Ta single crystals. The results show that Ravelo-EAM (Physical Review B, 2013, 88: 134101) potential behaves well at different hydrostatic pressures. Then, the MD simulation results based on the Ravelo-EAM potential show that Ta will experience a body-centered-cubic (BCC) to face-centered-cubic (FCC) phase transition before fracture under tensile loading at 1 K temperature, and model size and strain rate have no obvious effects on tensile behaviors of Ta. Next, from the simulation results at the system temperature from 1 to 1500 K, it can be derived that the elastic modulus of E 100 linearly decrease with the increasing temperature, while the yielding stress decrease with conforming a quadratic polynomial formula. Finally, the pressure dependence of the elastic properties is performed from 0 to 140 GPa and the observations show that the elastic modulus increases with the increasing pressure overall.

The failure types and ultimate loads for eight carbon-epoxy laminate specimens with a central circular hole subjected to tensile load were tested experimentally and simulated using two different progressive failure analysis (PFA) methodologies. The first model used a lamina level modeling based on the Hashin criterion and the Camanho stiffness degradation theory to predict the damage of the fiber and matrix. The second model implemented a micromechanical analysis technique coined the generalized method of cells (GMC), where the 3D Tsai–Hill failure criterion was used to govern matrix failure, and the fiber failure was dictated by the maximum stress criterion. The progressive failure methodology was implemented using the UMAT subroutine within the ABAQUS/implicit solver. Results of load versus displacement and failure types from the two different models were compared against experimental data for the open hole laminates subjected to tensile displacement load. The results obtained from the numerical simulation and experiments showed good agreement. Failure paths and accurate damage contours for the tested specimens were also predicted. [ABSTRACT FROM AUTHOR]

This article investigates the interest of using in-situ piezoelectric (PZT and PVDF) disks to perform real-time Structural Health Monitoring (SHM) of glass fiber-reinforced polymer composites submitted to various tensile loadings. The goal is to evaluate the working range and SHM potential of such embedded transducers for relatively simple mechanical loadings, with the long-term aim of using them to monitor complete 3D structures submitted to more complex loadings. SHM is performed acquiring the electrical capacitance variation of the embedded transducers. To study the potential links between the in-situ capacitance signal and the global response of the loaded host specimens, a multi-instrumentation composed of external Nondestructive Testing techniques was implemented on the surfaces of the specimens to search for multi-physical couplings between these external measurements and the capacitance curves. Results confirmed the non-intrusiveness of the embedded transducers, and allowed estimating their working domain. PZT capacitance signal follows well the mechanical loadings, but the piezoceramic transducer gets damaged after a determined relatively low strain level due to its brittleness. The limits of this working domain are extended by using a stretchable PolyVinylidene Fluoride (PVDF) polymer transducer, allowing this one to perform in-situ and real-time SHM of its host tensile specimens until failure. [ABSTRACT FROM AUTHOR]

Bone being a hierarchical composite material has a structure varying from macro- to nanoscale. The arrangement of the components of bone material and the bonding between fibers and matrix gives rise to its unique material properties. In this study, the micromechanisms of cortical bone failure were examined under different loading conditions using scanning electron microscopy. The experimental tests were conducted in longitudinal and transverse directions of bone diaphysis under tensile as well as compressive loading. The results show that bone material has maximum stiffness under longitudinal tensile loading, while the strength is higher under transverse compressive loading. A reverse trend of compressive mechanical properties of bone is observed for longitudinal and transverse loading as compared to trends reported in the previous studies. Therefore, micromechanisms of cortical bone failure were analyzed for different loading conditions to reveal such type of behavior of cortical bone and to correlate bone microstructure with mechanical response of bone. [ABSTRACT FROM AUTHOR]

The paper describes the study carried out to determine the relationships between the amount of vibrations that happen inside the rock at the time of failure under tensile loading and different rock properties such as uniaxial compressive strength, uniaxial tensile strength, Young's modulus, cohesion, angle of internal friction and density. It is then tried to interpret what are the factors that affect the vibrations and the time to failure. To capture the vibrations piezoelectric sensors are used which capture the acoustic signals and convert them into electric signals. With the help of Picoscope, it was then possible to recover the acoustic signals. At the time of failure, the peak voltage (h) was recorded along with the span of time the rock took to fail (w). The h/w ratio was then obtained and used to relate it with different rock properties. h/w ratio is the measure of how much vibrations happen inside the rock and for what amount of time. It was observed to be highly related to uniaxial tensile strength, angle of internal friction and rock density. [ABSTRACT FROM AUTHOR]

TiAl alloys can be used in aircraft and high-performance vehicle engines owing to their structural stability at high temperatures and their light weight. Although many studies have focused on developing this alloy material, there is still a lack of information about the changes in the structure of TiAl alloys under tensile and compressive loading. Therefore, we performed molecular dynamics simulations of the tensile and compressive loading of TiAl alloys in the direction at temperatures of 10 and 300 K. From our simulation results, we found that the tensile and compressive strengths of TiAl alloys are significantly affected by temperature. It was found that TiAl alloys can withstand greater compression loading than tensile loading. This is due to the change in the crystal structure of TiAl alloys after being deformed to a strain of 0.4 by compressive loading, according to the analysis of structural changes under loading conditions. From the radial distribution analysis results, there was a change in the orientation of the face-centered cubic-like structure as it reached the maximum compressive stress compared to the initial structure.