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Landslides, ground fissures, and soil collapses are common natural disasters frequently associated with the tensile strength of loess. However, due to measurement difficulties, previous studies have often overlooked the tensile failure characteristics and processes of loess. This paper utilizes electrical resistance and Digital Image Correlation (DIC) technologies to investigate the changes in electrical resistance and surface strain fields during the Brazilian split test on remolded loess under various dry densities, moisture contents, and loading methods. The experimental results indicate that an increase in dry density and a reduction in moisture content decrease the tensile strength of loess. Cracks appear and electrical resistance begins to increase after reaching the peak load. The tensile strength under platen loading is lower than that under loading disc application, and the latter is not suitable for soils with high plasticity. Borehole water injection reduces the tensile strength and peak displacement of high moisture content soil samples, whereas for low moisture content samples, the peak displacement remains unchanged after water injection, but the tensile strength decreases. The failure stages of loess in the Brazilian split test are divided into four phases: stress adjustment contact phase, elastoplastic deformation phase, tensile cracking phase, and residual deformation phase. The angle between the load–displacement curves before and after the peak load is proposed as a criterion for determining brittleness. [ABSTRACT FROM AUTHOR]

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The induction welding has been recognized as one of potential and high-efficiency joining methods for thermoplastic composite materials. In this study, a numerical simulation model with containing both induction wielding heat transfer and joint tensile failure process for CF/PPS-Al alloy interlocking induction welding was established based on software COMSOL Multiphysics and Abaqus/Explicit. The CF/PPS-Al7075 interlocking welding joints with special designed macro-scale interlocking were tested under tensile loads, and the corresponding single-lap shear strength, energy absorption, and failure mechanisms were investigated by combining the experimental and numerical approaches. Finally, the influence of macro-scale interlocking geometric parameters on joint tensile strength was also discussed. The results indicate that the proposed model can effectively predict the temperature distribution in the welding process and the tensile failure process of the joint. It is also presented that the addition of macro-scale interlocking features can effectively improve the ultimate load (47%) of the CF/PPS-Al alloy induction welded joints. Meanwhile, the number of addition PPS films in the welding zone and the inclination angle have greater contribution on the tensile strength of the welded joints. [ABSTRACT FROM AUTHOR]

Abstract A better understanding of the tensile performance and tensile failure mechanism of cement paste is significant in preventing rock reinforcement failure. Therefore, this paper aims to reveal the tensile performance and failure mechanism of a modified Portland cement: Stratabinder HS cement. To achieve this objective, the split tensile test was conducted on specimens followed by simulating the failure mechanism numerically. The results indicated that the water–cement rate significantly influenced the tensile performance of the cement paste. When the water–cement rate increased from 0.35 to 0.42, the tensile strength declined from 1.9 MPa to 1.5 MPa. It was also observed that vertical tensile failure constantly occurred regardless of the water–cement rate. During the testing process, tensile cracks and shear cracks occurred. The increasing rate in the number of specimen cracks was dependent on the tensile stress state. Before the tensile stress reached the peak, the crack quantity increased slightly. After the peak, the crack quantity increased dramatically. During the vertical loading process, horizontal tensile stress occurred in the specimen. This horizontal tensile stress zone showed a diamond shape. The higher the tensile stress is, the larger the area of the horizontal tensile stress zone. When the tensile strength was reached, horizontal tensile stress mainly concentrated at the vertical centre of the specimen. This finally led to tensile failure of the specimen. This paper indicated that the water–cement rate was the key factor in evaluating the tensile strength of the Stratabinder HS cement.

This study focused on the in-plane rocking behavior of unreinforced masonry (URM) walls. Three URM wall specimens were designed and fabricated based on a typical masonry house in Korea. The experimental parameters were the layout of openings (its presence or absence) and configuration of openings (window or door). Static cyclic loading tests were conducted to investigate nonlinear performance curves of masonry walls subjected to a rocking behavior in the in-plane direction. In this paper, the mortar-joint tensile crack strength and rocking strength of masonry walls (i.e., peak and residual strengths) were evaluated, and the effects of opening configurations on the masonry wall strength were examined, due to the proposed procedure. The deformation capacity of a rocking behavior was also identified by the procedure. As a result, specimens without initial cracks showed the rocking behavior after mortar-joint tensile crack failure, whereas a specimen with initial cracks exhibited only the rocking behavior. Since no remarkable strength deterioration was found until final loading in all specimens, an in-plane rocking URM wall may have very good deformation performance. The estimated mortar-joint tensile crack strength, rocking strength, stiffness, and ultimate deformation were in good agreement with the experimental results, regardless of the layout and configuration of openings. [ABSTRACT FROM AUTHOR]

A better understanding of the tensile performance and tensile failure mechanism of cement paste is significant in preventing rock reinforcement failure. Therefore, this paper aims to reveal the tensile performance and failure mechanism of a modified Portland cement: Stratabinder HS cement. To achieve this objective, the split tensile test was conducted on specimens followed by simulating the failure mechanism numerically. The results indicated that the water–cement rate significantly influenced the tensile performance of the cement paste. When the water–cement rate increased from 0.35 to 0.42, the tensile strength declined from 1.9 MPa to 1.5 MPa. It was also observed that vertical tensile failure constantly occurred regardless of the water–cement rate. During the testing process, tensile cracks and shear cracks occurred. The increasing rate in the number of specimen cracks was dependent on the tensile stress state. Before the tensile stress reached the peak, the crack quantity increased slightly. After the peak, the crack quantity increased dramatically. During the vertical loading process, horizontal tensile stress occurred in the specimen. This horizontal tensile stress zone showed a diamond shape. The higher the tensile stress is, the larger the area of the horizontal tensile stress zone. When the tensile strength was reached, horizontal tensile stress mainly concentrated at the vertical centre of the specimen. This finally led to tensile failure of the specimen. This paper indicated that the water–cement rate was the key factor in evaluating the tensile strength of the Stratabinder HS cement. [ABSTRACT FROM AUTHOR]

The investigation into the effects of acidizing treatment on the mechanical property of hot dry rocks (HDR) is beneficial for our understanding of the fracturing and stimulation mechanisms in HDR reservoirs. In this article, Brazilian disk tests were first carried out for hollow hot dry rocks with different internal diameters after acidizing treatments. The influences of acidizing treatments on the physical properties, tensile strength, and failure patterns of hot dry rock specimens were presented. Besides, the effects of the diameter of the internal hole on the peak load and failure patterns of the hot dry rock specimens were also investigated. The peak load decreases with the increase in the internal diameter. The results indicated that the acidizing treatments can dissolute the minerals, decrease rock mass, and tensile strength. The investigation of failure patterns demonstrated that the acidizing treatment is beneficial for the fracturing of hot dry rocks. The present study can provide some basic and theoretical data for the development of geothermal reservoir. [ABSTRACT FROM AUTHOR]

The mechanical behavior of loess is highly predicated on variation in its moisture content. While the impacts of the water content on the shearing behavior and collapsibility of loess have been extensively studied, its effect on tensile characteristics has received relatively little attention. In this study, a series of tensile tests were conducted on remolded specimens of a clayey loess that were collected from Ili Valley in China. Two sets of loess specimens with varying water contents were prepared separately using wetting and drying methods. The influence of the water content on the tensile stress–strain response, failure mode and tensile strength was investigated by combining the tensile test results and particle image velocimetry (PIV) analysis. On this basis, a nuclear magnetic resonance (NMR) test and scanning electron microscopy (SEM) observations were implemented in order to assist with the interpretation of the underlying mechanism. The test results indicate that the tensile failure process and the variation of tensile strength with varying water contents differ for specimens that are prepared with wetting and drying methods; a finding which arises from the differences in the soil microstructure, clay–water interaction and the distribution of capillary and adsorbed water. This research has shown that the tensile strength of clayey loess is essentially dominated by the clay's hydration/cementation and the development of capillary and adsorption suction as well as the microstructural evolution that occurs with the change in the water content. Based on the experimental observations, a conceptual model is proposed in order to interpret the effect of water content on loess' tensile behavior. [ABSTRACT FROM AUTHOR]

In situ synchrotron radiation computed tomography (SRCT) was used to compare the fibre damage progression in five configurations of (902/02)s carbon-epoxy coupons loaded to failure. The effects of different sizing types, surface treatments and fibre diameters on the macroscopic properties, for example, ultimate tensile strength (UTS), and on the damage accumulation at a microscopic scale, for example, fibre break accumulation, were assessed. A semi-automated approach was adopted to process the large amount of data obtained from the SRCT scans and further method applicability areas can be envisaged. Single fibre break accumulation was seen to be influenced by the fibre type, while the formation of interacting fibre break groups by the surface treatment and the sizing type. For the materials presented, it can be suggested that an increased defect tolerance can be obtained by moving from stronger to weaker fibre-matrix adhesion, with sub-critical multiplet behaviour emerging as independent of the average UTS value. [ABSTRACT FROM AUTHOR]

The mechanical behavior of loess is highly predicated on variation in its moisture content. While the impacts of the water content on the shearing behavior and collapsibility of loess have been extensively studied, its effect on tensile characteristics has received relatively little attention. In this study, a series of tensile tests were conducted on remolded specimens of a clayey loess that were collected from Ili Valley in China. Two sets of loess specimens with varying water contents were prepared separately using wetting and drying methods. The influence of the water content on the tensile stress–strain response, failure mode and tensile strength was investigated by combining the tensile test results and particle image velocimetry (PIV) analysis. On this basis, a nuclear magnetic resonance (NMR) test and scanning electron microscopy (SEM) observations were implemented in order to assist with the interpretation of the underlying mechanism. The test results indicate that the tensile failure process and the variation of tensile strength with varying water contents differ for specimens that are prepared with wetting and drying methods; a finding which arises from the differences in the soil microstructure, clay–water interaction and the distribution of capillary and adsorbed water. This research has shown that the tensile strength of clayey loess is essentially dominated by the clay’s hydration/cementation and the development of capillary and adsorption suction as well as the microstructural evolution that occurs with the change in the water content. Based on the experimental observations, a conceptual model is proposed in order to interpret the effect of water content on loess’ tensile behavior.

The seismic responses of asphalt slabs in asphalt concrete-faced rockfill dams (ACFRDs) under the oblique incidence of seismic waves and the effect of a high strain rate on failure evaluation are still understudied. In this paper, formulas for the free field of SV waves at arbitrary incident angles are derived, a wave input model for SV wave spatial oblique incidence is established, and a method is proposed for assessing the failure of asphalt slabs. In this method, the real-time change in the tensile strength as it relates to the strain rate is considered. Taking an actual ACFRD as the research object, 16 obliquely incident SV wave conditions with different azimuthal and oblique incidence angles are considered, the influences of the incidence angle on the seismic response of an asphalt slab are analyzed in terms of the stress and acceleration, and the differences between the static and dynamic damage assessment methods are explored. The results show that the established SV-wave spatial oblique incident wave input model can accurately simulate the free-field half-space. The numerical solution of the wave input agrees well with the analytical solution. Compared with that of the vertical input, the maximum acceleration of the slab in the axial and vertical directions increased for 13 of the 15 oblique incidence conditions. The spatially oblique input leads to an increase in the dynamic stresses on the slabs, with the maximum tensile and compressive stresses increasing by 63 % and 153 %, respectively. Neglecting the oblique incidence of seismic motion may result in a significant underestimation of the seismic response of the slab. Moreover, the traditional method of increasing the static strength by 20 % as a criterion for determining the strength of slab tensile failure is overly strict. [ABSTRACT FROM AUTHOR]

It is quite common for fill slopes such as embankments and airport foundations to be constructed in mountainous areas. Steep fill—rock interfaces in such areas undergo tensile failure owing to differences in the stiffness values and tensile strengths of the soil and hard rock. In this study, a new anchor system, termed "radial cable," is proposed to increase the pullout capacity of cables in the fill; this in turn helps control tensile deformation in the fill slope along the interface. In a radial cable, the steel ropes of a conventional cable are equally and symmetrically separated into three sub-cables (a central sub-cable and two branch sub-cables) with a radial distribution starting from the position of the interface. Moreover, each of the sub-cables is fixed in the fill using short U-shaped rigid rods along the cable length and a rigid baffle at its end to further increase pullout resistance. Experimental and numerical uplift tests were conducted to analyze the pullout capacity and anchoring behavior of the radial cables in soil to study the effect of branching. The reinforcement effect of the radial cables was also examined using a case study. [ABSTRACT FROM AUTHOR]

In recent decades, numerous geotechnical hazards, including landslides, foundation settlements, and tunnel collapses, have been linked to block-in-matrix rock (bimrock), resulting in substantial damage. The investigation and analysis of the engineering properties and mechanical behavior of both the rock and soil have become increasingly intriguing research areas. However, analyzing bimrock remains a formidable challenge due to its inherent heterogeneity. In this study, to investigate the tensile behavior of the bimrock, the numerical method that couples discontinuous deformation analysis (DDA) and smoothed particle hydrodynamics (SPH) is improved. First, a tension damage model is implemented in SPH for simulating the tensile behavior of the soil. The effectiveness of the presented model is verified through the direct tensile test model and the Brazil disc split model as an indirect tensile test. The contact algorithm of DDA-SPH is then modified by adding a tensile contact spring to introduce tensile strength at the interface between the matrix and the rock in the bimrock. Through a simple pulling numerical model, the accuracy of this modification has been verified, and the appropriate tensile contact stiffness is discussed. Furthermore, using the proposed method, the overall tensile strength of the bimrock with respect to the interface tensile strength is investigated. Finally, the proposed numerical method is applied to the simulation of geoengineering problems, demonstrating the capacity to analyze the stability and large deformation of bimrocks. • A tension damage model is added to the soil-particle based SPH method for simulating the tensile behavior of the matrix. • The contact algorithm of DDA-SPH is then modified by adding a tensile contact spring to introduce tensile strength at the interface. • The overall tensile strength of the bimrock with respect to the interface tensile strength is investigated. • The proposed method is applied to analyzing the bimrock slope and bimrock shallow tunnel. [ABSTRACT FROM AUTHOR]

Abstract An experimentally validated multiscale computational model for predicting the progressive damage and failure analysis (PDA) of 3D woven textile composites (3DWTCs), is presented. The 3DWTCs are made through a 3D textile weaving process and the dry fiber tows are infused with SC-15 polymer matrix into a single composite material. A thick symmetric configuration of hybridized (carbon, glass and kevlar tows) textile architecture is examined at the entire coupon level to determine the progression of damage under tensile loading and to understand the benefits of hybridization and the resulting performance enhancements. Results also include micro-CT analysis of the laboratory scale coupon to study the effect of microstructure imperfections response. A finite element (FE) model is generated directly from micro-CT data using the software, Simpleware [1]. A three-scale modeling strategy is adopted, where the meso-scale representative volume elements (RVEs) are modeled explicitly in the failure prone gage-area to consider the tow architecture and a 2-layer concentric cylinder (2CYL) [2,3] micromechanics model is used within the fiber tows to consider the fiber/matrix scale and the pre-peak nonlinearity, as caused by matrix microdamage. The analytical subscale model results in a computationally efficient framework for PDA of 3DWTCs. [ABSTRACT FROM AUTHOR]

In a unidirectional composite under static tensile loading, breaking of a fiber is shown to be a locally dynamic process, leading to stress concentrations in the matrix and neighboring fibers and debonding of the interface, which can propagate at high speed over long distances. In our previous work, a fiber break within a two-dimensional fiber array embedded in elastic epoxy matrix (with cohesive interface) was modeled to quantify the effects of these dynamic stresses. The results indicated that the elastic limit of the polymer matrix can be exceeded. In this study, the effects of matrix plasticity on dynamic stress concentrations due to a single fiber break are investigated. For the range of matrix yield stresses considered, the dynamic stress concentrations are significantly higher than corresponding values predicted by a quasi-static model with a pre-broken fiber. Based on the ratio of shear yield strength of the matrix and mode II peak traction of the interface cohesive law, two distinct regimes of damage are shown to exist. Only matrix yielding occurs when this ratio is less than 1.0, while both interfacial debonding and matrix yielding occur when it is greater than 1.0. At higher fiber break strengths, where the elastic matrix model predicts unstable interfacial debonding, reduction in matrix yield strength leads to a transition to stable debonding and arrest. Reducing the matrix yield strength also leads to a lowering of the peak dynamic stress concentrations in adjacent fibers, while spreading the stress concentrations over a larger volume of the composite microstructure. [ABSTRACT FROM AUTHOR]

Horizontal borehole instability raises concern due to negative impacts on success of drilling, reaming and pipe installation during Horizontal Directional Drilling. Shear failure (blow-out) and tensile failure (hydraulic fracture) are the two main failure mechanisms controlling borehole instability in saturated clay. Criteria for categorizing shear failure versus tensile failure are given which are functions of the ratio of undrained shear strength to vertical effective stress S u / σ v ′ and the Lateral Earth Pressure Coefficient at Rest K 0 ′ . Given that S u / σ v ′ and K 0 ′ can be expressed as a function of soil parameters like friction angle, Over Consolidation Ratio (OCR) and Liquidity Index (LI), new forms of these criteria are developed for situations where S u / σ v ′ and K 0 ′ cannot be obtained directly. It is confirmed that tensile failure generally controls in brittle clays like heavily overconsolidated and/or low liquidity index materials. Cases from the laboratory and the field as reported in the literature are used to examine the effectiveness of the new criteria, with inconsistency between theory and the physical evidence explained. [ABSTRACT FROM AUTHOR]

Introduction: This study aims to investigate the strength characteristics of fiber composites under uniaxial tensile stress. Methods: A tensile failure finite element model based on fracture mechanics was built for fiber composites. The principal stress concentration–release–transfer evolution and the crack propagation of the composites under the conditions of equal single fiber width, unequal quantity, and equal total fiber width and unequal quantity were discussed. Results: The tensile strength of the composites increased with fiber quantity when the width of each single fiber was equal. Conclusions: The tensile strength of the composites increased with fiber quantity when the total width of the composite fiber was equal. [ABSTRACT FROM AUTHOR]

• The experimental results indicate that the specimens undergo three types of local compressive failure modes. • The calculation model for the local bearing capacity of concrete with spiral stirrups F l is formulated. • To ensure simultaneous tensile and compressive failures, a critical reinforcement ratio of the spiral stirrup ρ v u is proposed. • The calculation model is highly accurate. This study evaluates the mechanical and failure modes of 30 concrete specimens under local compression. The experimental results indicate that the specimens undergo three types of local compressive failure modes. These modes primarily depend on the strengths of the tensile and compression regions. Based on the test results, a calculation model for the local bearing capacity of concrete with spiral stirrups F l is formulated. In the model, the local compressive failure of concrete with spiral stirrups is classified into tension and compression. The yielding of spiral stirrups in the tensile region is regarded as tensile failure, and compressive failure is considered to have occurred when the strain value in the compression region reaches 0.002. To simplify the model calculation, the spacing s , diameter d , and yield strength f y of spiral stirrup as well as the local compression area ratio A b / A l (ratio of the concrete bearing area A b to the loading area A l) are comprehensively analyzed. Based on the analysis results, a formula for the bearing capacity of the reinforcement N s is derived. The independent variables of the formula are yield force of spiral stirrup f y A ssl , stirrup spacing s , and ratio of specimen side length to loading plate side length h / a. A simplified formula for calculating the tensile failure of the specimen is derived. To ensure simultaneous tensile and compressive failures, a critical reinforcement ratio of the spiral stirrup ρ v u is proposed based on the calculation model. Test data from similar axial local compression tests are collected to verify the accuracy of the calculation model. The local bearing capacity of concrete is recalculated according to the calculation method proposed in this study. Results show that the calculation model is highly accurate. Accordingly, it may be used as reference for calculating the local bearing capacity. [ABSTRACT FROM AUTHOR]

Natural fractures and laminations are common features in many unconventional resources which require hydraulic fracturing for economic production. To better understand the effect of such features on rock failure, we have conducted indirect tensile or Brazilian testing on several rock samples from Green River and Niobrara formations. Brazilian experiments were conducted at various orientations of laminations or natural fractures with respect to the loading direction. In contrast to isotropic rocks, we observed that rock failure can occur away from the vertical central line of rock parallel to lamination or natural fracture when the approaching angle between the lamination and loading direction is less than 30° in the tested samples. It was also determined that the tensile strength parallel to laminations or calcite-filled fractures is lower than the tensile strength perpendicular to lamination and/or the natural fractures; for instance the tensile strength of Niobara calcite-filled fractures were almost one third of the rock matrix. [ABSTRACT FROM AUTHOR]

The influence of defect band on the tensile failure in high pressure die casting of AM60B magnesium alloy was studied by in situ scanning electron microscope. Results showed that the size and distribution of the externally solidified crystals (ESCs) had a significant influence on the tensile behavior induced by defect band in the specimen. In the specimen with few ESCs, the crack would initiate at the gas-shrinkage pore in the center of the specimen. Further crack propagation at the defect band was hindered by the surrounding dense microstructure, and the effect of defect band on the tensile failure was just reducing the efficient force bearing area. In the specimen with large and complex ESCs, the microstructure around the defect band would become coarse and comprised of large porosities with complex morphology. The defect band would act as crack initiation site and facilitate the crack propagation to both center and surface of the specimen, leading to the final fracture. [ABSTRACT FROM AUTHOR]

Fibre-reinforced composites are rapidly increasing their market share in structural applications. Nevertheless, this increase would be much stronger if reliable failure predictions were available. These predictions are not only insufficiently reliable for complex loading of multidirectional composites, but even for longitudinal tensile failure of unidirectional (UD) composites. Since composite failure usually coincides with longitudinal failure of a 0° ply, the reliability often hinges on longitudinal failure predictions of UD composites. Despite great progress in the state-of-the-art models, significant obstacles remain in collecting the necessary input data and understanding the influence of the modelling assumptions. This review therefore surveys the mechanics, chemistry and physics involved in tensile failure of UD composites and highlights potential areas for improvement. Specific proposals are made to advance the state-of-the-art strength models, which could catalyse the use of composites in structural applications. [ABSTRACT FROM AUTHOR]

The development of realistic numerical tools to efficiently model the response of concrete structures subjected to close-in detonations and high velocity impact has been one of the major quests in defense research. Under these loading conditions, quasi-brittle materials undergo a multitude of failure (damage) mechanisms. Dynamic tensile failure (e.g. spalling), characterized by a significant strength increase associated with loading rate, has revealed to be particularly challenging to represent. In this contribution, a rate-dependent stress-based nonlocal damage model has been introduced for the simulation of dynamic tensile failure of quasi-brittle materials. The recently proposed stress-based nonlocal criterion has been updated in order to be consistently combined with a rate-dependent version of the well-known Mazars damage model. The model was implemented in LS-DYNA using a fully explicit computational scheme. Two sets of numerical examples have been presented. First, one-dimensional numerical analyses were conducted to evaluate the model capabilities, applicability and limitations. Second, the model has been validated against experimental results. It has been shown that the proposed model, in addition to correcting spurious mesh sensitivity, also provides a more realistic representation of damage initiation and growth, in particular around discontinuities (notches and free boundaries) and damaged areas. [ABSTRACT FROM AUTHOR]

• The wave input method for P-wave spatial oblique-incidence is established. • A new core safety evaluation method based on instantaneous tensile stress and strength is proposed. • The responses of an asphalt concrete core embankment dam under P-wave spatial oblique incidence are investigated. • The damage mechanism of the core caused by spatial oblique incidence is revealed. • The tensile weak zone of the core under different incident modes are clarified. The research on asphalt concrete core embankment dam under the spatial oblique incidence of seismic wave and the dynamic tensile failure of the core is still insufficient. This paper considers the spatial arbitrariness of P-wave incident azimuth angle γ and oblique incident angle α , constructs the non-uniform free field on the foundation boundary based on the wave field superposition principle, and establishes a wave input method for P-wave oblique-incidence in three-dimensional space. Then, an empirical formula for the change in the instantaneous tensile strength of asphalt concrete with the strain rate is established on the basis of the test results. Furthermore, a new core safety evaluation method based on instantaneous tensile stress and strength is proposed to discriminate element tensile failure. Finally, the influence law of incident azimuth and oblique incident angles on the acceleration and stress spatial distribution of asphalt concrete core is analyzed. The damage mechanism of the core caused by the surge of local tensile stress caused by spatial oblique incidence is revealed. The traditional static strength discrimination method has an error in discriminating the core failure compared with the method proposed in this paper. The distribution characteristics of tensile weak zone and failure zone of the core under different incident modes are clarified. Results show that compared with the vertical incident, the core accelerations in the water flow and dam axis directions increased by a maximum of 9.6 times and 68% under spatial oblique incidence (γ ∈ [0°, 90°] and α ∈(0°, 75°]), and the core acceleration in the vertical direction can be reduced by 69%. The core compressive and tensile stresses increased by a maximum of 31.3% and 4.0 times under spatial oblique incidence (γ ∈ [0°, 90°] and α ∈(0°, 75°]). Neglecting spatial oblique incidence will underestimate the core accelerations and stresses seriously. The more the incident direction deviates to the dam axis and the larger the oblique incident angle is, the more prone it is to tensile failure on the wave-facing side of the core. When the incident direction is consistent with the dam axis and the incident angle is 75°, the tensile failure on the wave-backing side of the core is more serious than that on the wave-facing side. The use of the traditional static strength discrimination method will result in the large crack failure error of the core. [ABSTRACT FROM AUTHOR]

The failure strain of fibre-reinforced composites can be increased by fibre hybridisation. A recently developed model for unidirectional composites was extended to hybrid composites to analyse this synergetic effect, called the hybrid effect. The model predicts individual fibre breaks and interactions among clusters of fibre breaks. Three key parameters were studied to understand how they can maximise the hybrid effect, namely low elongation fibre strength scatter and hybridisation fibre stiffness and failure strain. Larger strength scatter of the low elongation fibres leads to larger hybrid effects, as the scatter spreads out the cluster development over a larger strain interval. The failure strain ratio of the two fibre types should be above 2 for the properties used here, but a higher ratio did not yield any additional benefits. Increasing the stiffness of the hybridisation fibre reduces the stress concentrations on the low elongation fibre and may also enlarge the hybrid effect. These conclusions provide guidelines for designing optimal hybrid composites. [ABSTRACT FROM AUTHOR]

Unstable failure of brittle rocks is a hazardous problem in deep mining and tunneling projects. Failure of brittle rocks around excavation boundaries is dominated by tensile fracturing. Homogeneous models cannot capture this rock failure mechanism while heterogeneous models are proven capable of capturing it. A question that may arise is how a change in failure mechanism influences the failure intensity. In this paper, an explicit FEM tool (Abaqus) is employed to simulate failure of homogeneous and heterogeneous rocks. Material heterogeneity is introduced into Abaqus models using Python scripts and the simulation results demonstrate that heterogeneous models can capture splitting rock failure. The effect of material heterogeneity on rock failure intensity in unconfined and confined compression tests is investigated. The simulation results from both types of models show that rock failure is more violent when the loading system is softer and the confinement is lower. However, it is observed that when two materials have the same peak strength, the heterogeneous model has more released energy than the homogeneous model due to the difference in the failure mode. The tensile splitting failure mode of the heterogeneous model releases more energy than the shear failure mode of the homogeneous model. This can be an important point to be considered for rockburst support design. Furthermore, the simulation results show that for two models with similar material composition, the strength of the more heterogeneous model is lower than the less heterogeneous model; as a result, the failure of the more heterogeneous model will be less violent if it fails in an unstable fashion, and this is in good agreement with field observation results. [ABSTRACT FROM AUTHOR]

A modified smoothed particle hydrodynamics (SPH) method is applied to simulate the dynamic tensile failure of rock-like heterogeneous materials. The material heterogeneities are represented by different mechanical properties with a Weibull distribution at different particles over the specimen. An elasto-plastic-damage model is adopted to simulate material failure. Numerical simulations are performed for three specimens with different degrees of heterogeneity under quasi-static and dynamic loading conditions, respectively. The effects of strength criterion coefficient on the predicted tensile strength are also discussed. Results show that the material heterogeneity has significant effect on the dynamic tensile failure, especially at a higher strain rate loading condition. At a lower strain rate, the failure mode of heterogeneous material is very much similar to that of homogeneous materials. At a higher strain rate, plenty of micro cracks occur forming a failure band in the tension zones. Moreover, the value of strength criterion coefficient has a considerable influence on the tensile strength under a higher loading rate. [ABSTRACT FROM AUTHOR]

A self-developed rotary multi-cutter device cuts stainless steel wire ropes into segments to fabricate twisted wires. Stainless steel porous twisted wire materials (PTWMs) with a spatial composite intertexture structure are produced by the compaction and subsequent vacuum solid-phase sintering of twisted wires. The stainless steel PTWMs show two types of typical uniaxial tensile failure modes, i.e., a 45° angle fracture mode and an auxetic failure mode (the PTWMs expand along the direction perpendicular to the tension). The effects of the sintering parameters, porosities, wire diameters, and sampling direction on the tensile properties of the PTWMs are carefully investigated. By increasing the sintering temperature from 1130 °C to 1330 °C, the tensile strength of the PTWMs with 70% target porosity increased from 7.7 MPa to 28.6 MPa and the total failure goes down to 50%. When increasing the sintering time from 90 min to 150 min, the tensile strength increases from 12.4 MPa to 19.1 MPa and the total failure elongation drops to 78.6%. The tensile strength of the PTWMs increases from 28.9 MPa to 112.7 MPa with decreasing porosity from 69.5% to 46.0%, and the total failure elongation also increases from 14.8% to 40.7%. The tensile strength and the failure strain of the PTWMs with fine wires are higher than those of the PTWMs with coarse wires under the same porosity. Sampling direction has a small influence on the tensile properties of the PTWMs. [ABSTRACT FROM AUTHOR]

High brittleness is the prerequisite for the creation of a hydraulic fracture network, which is crucial for shale reservoir development. The test evaluation methods are restricted in the field by lack of continuous brittleness profiles. Mineralogical evaluation cannot incorporate the external factors like stress state. The most widely used method is mechanical evaluation method based on statistical results of Young's modulus and Poisson's ratio. This method cannot explain the brittle tensile failure mechanism of shale and contradiction between high brittleness and barriers of high strength rock. With these methods, brittle evaluation and interval selection errors will happen in the application. Starting from the mechanism of rock failure and considering the effect of rock mechanical properties on brittleness, a new method for rock brittleness evaluation has been established. Firstly, the failure surface features were analyzed and the dominant mechanisms in complex failure were identified with triaxial test and scanning electron microscopy test. Secondly, a stress model for shale reservoirs with thin sand and shale interbedded was set up based on elasticity and the factors affecting the stress distribution and failure modes have been analyzed. Eventually, based on experiments and theoretical recognition, the brittleness index for shale was proposed by integrating Young's modulus, Poisson's ratio and fracture toughness. Moreover, a method for acquiring brittleness index from well logs was developed from which brittleness profiles for shale formations in Sichuan basin were obtained. Failure features analysis demonstrates that tensile failure dominates during rock brittle failure. It was observed that compression stress on rock is only relevant to mechanical parameters and independent of space location under both internal and external stresses. Finally, comparison with the results from Rickman's method and microseismic monitoring demonstrates that the method developed in this work possesses more satisfactory results of brittleness evaluation and interval selection in field application. [ABSTRACT FROM AUTHOR]

Uniaxial tensile behavior of concrete plays an important role in the behavior of concrete specimens as well as structural elements. A 2D mesoscale analysis is performed to investigate the fracture process of concrete subjected to uniaxial tension by using the extended finite element method. The concrete considered includes the hydrated cement paste, aggregate particles, and the interfacial transition zones. In the cracked domain, to represent the discontinuities of a displacement field, the Heaviside jump function is added to the common finite element approximation for the local enrichment based on the framework of partition of unity. A user-defined subroutine for the extended finite element method is implemented with FORTRAN codes and embedded into the commercial software ABAQUS. The failure process of the L-specimen is studied, and good agreement is obtained between the experimental observation and the present simulation results. Based on the extended finite element method, the fracture process of the concrete under uniaxial tension is investigated subsequently. The influences of aggregate distribution, aggregate size, and aggregate shape as well as the strength of interfacial transition zone on the failure process and the global deformation process of concrete are analyzed. The crack initiation, propagation, and failure mode of concrete specimens are also discussed in detail. The simulation results indicate that the macroscopic mechanical properties of concrete are merely dependent on the aggregate distribution, but dependent on aggregate shape, size, and strength of the interfacial transition zone. [ABSTRACT FROM PUBLISHER]

• Shale's tensile strength increases as bedding angle, while coal not. • Inverted Trumpet-shaped trend lines are established for shale and coal. • Ultimate loading rate exists for shale and coal is different. • Microstructures is the main cause of strength and failure anisotropy. • Bedding effects weakens as loading rate increases. Shale and coal samples were selected to clarify the tensile failure of layered sorptive rocks under the co-influence of bedding planes and loading conditions. Results indicate that, for these two rocks, tensile strength exhibited anisotropy. As loading rates rises, inverted Trumpet-shaped trend lines is proposed to reflect bedding effects with loading effects. The tensile strength of shale increases linearly with the bedding angle rises, while the value of coal shows great dispersion. The former is greater than the latter. An ultimate loading rate exists for shale and coal. Empirical relations were established to describe tensile strength with varying loading rate and bedding angle. Under the co-influences of bedding plane and loading conditions, more complex failure modes happened for coal and shale samples. Hydraulic fracturing along the direction of 60° (for shale reservoirs) or 45° (for coal reservoirs) to the bedding plane is more likely to produce a complex fracture network. [ABSTRACT FROM AUTHOR]

Damage accumulation in compact bovine femur subjected to uniaxial tensile loading was examined by strong light illumination effects of microcracking. Imaging was done using a high-speed camera capturing image at 200 to 1500 FPS. The tensile tests were performed in a multipurpose tensile testing system with cross-head speeds ranging from 0.5 to 10 mm/min which leads to strain rates of 0.0001 to 0.0012 s-1 (physiologically relevant to walking and running Hansen et al., 2008). The post-failure images were then examined in a scanning electron microscopy (SEM) and effects of microstructure, strain rate, and orientation were evaluated. Correlation of the high-speed images with stress-strain curves indicated that optically visible microcracks were most likely initiated at yielding, and the specimens with dispersed microcracks exhibited a higher energy-absorption capacity compared to the specimens with coalesced local cracks. It was found that damage accumulation negatively correlates to strain rate and that transverse specimens exhibited a different failure pattern compared to the longitudinal specimens. Strain hardening and softening were found in the longitudinal and transverse specimens respectively. The microcracking in the transverse specimens instantly increased to peak after yielding compared to the gradual growth until failure in the longitudinal specimens. The average Young's modulus (21.5 GPa) and ultimate stress (93.5 MPa) of the specimens loaded in the longitudinal direction were more than twice that of the specimens (10.9 GPa and 36.2 MPa respectively) loaded in the transverse direction. The current technique has shown potential in relating damage accumulation real time in bone samples subjected to tensile loading condition. This information will be helpful in relating the role of micro damage accumulation in initiating failure and/or remodeling in bone. [ABSTRACT FROM AUTHOR]

Due to the characteristic that shape memory materials can quickly return to their original shape and have large deformation, such materials can be used as the connection in active disassembly devices. However, existing active disassembly devices typically require two moulding steps and complicated machining processes that result in high manufacturing cost. The active disassembly device based on the proposed decapitated head method has only one moulding step and lower manufacturing cost. Its disassembly mode is local damage disassembly, which can decrease the active disassembly cost and improve disassembly efficiency. This paper describes the active disassembly theory and the design methodology based on the decapitated head method, and then analyses the design criteria and feasibility of this method with a real case study. [ABSTRACT FROM PUBLISHER]

Essentially, every failure of a short fiber reinforced composite (SFRC) under tension is induced from a matrix failure, the prediction of which is of fundamental importance. This can be achieved only when the homogenized stresses of the matrix are converted into true values in terms of stress concentration factors (SCFs) of the matrix in an SFRC. Such an SCF cannot be determined in the classical way. In this paper, a closed-form formula for the longitudinal tensile SCF in the SFRC is derived from the matrix stresses determined through an elastic approach. The other directional SCFs in an SFRC are the same as those in a continuous fiber composite already available. A bridging model was used to calculate the homogenized stresses explicitly, and a failure prediction of the SFRC with arbitrary fiber aspect ratio and fiber content was made using only the original constituent strength data. Results showed that the volume fraction, the aspect ratio, and the orientation of the fiber all have significant effect on the tensile strength of an SFRC. In a certain range, the tensile strength of an SFRC increases with the increase in fiber aspect ratio and fiber volume content, and the strength of the oriented short fiber is higher than that of the random short fiber arrangement. Good correlations between the predicted and the available measured strengths for a number of SFRCs show the capability of the present method. [ABSTRACT FROM AUTHOR]

Tensile strength of rocks is an important parameter involved in the design and stability analysis of rock structures. The present paper is devoted to develop a new experimental method to investigate tensile strength, and the effect of confining pressure (P c) on tensile behavior of rocks in underground rock engineering. A triaxial direct tension (noted as TDT) apparatus was developed based on the conventional triaxial compression (noted as CTC) device with the inspiration of the glue on steel cap type of method. TDT tests were carried out on the Fontainebleau quartz sandstone specimens under four different confining pressures. CTC tests under nine confining pressures were also carried out in order to compare the tension and compression behavior of the tested quartz sandstone. Tensile stress-strain curves were obtained during the CTC and TDT tests. Post-failure specimen analysis was also carried out to identify the failure mode in TDT test. The triaxial tension failed surfaces was sampled and scanned with the optical microscopy to obtain three dimensional images to show the effect of the confining stress on the failed surface roughness. The relationship between tensile and compressive strength and the strength criteria were analyzed with the experimental data. The results show the failure mechanism under TDT loading is different from that under CTC. The inter-grain cement is the dominant factor that contributes to the triaxial tensile strength of the quartz sandstone although the increase of confining pressure can induce a decrease of the triaxial direct tensile strength. It is suggested that the direct tensile strength of rocks should be tested directly for underground structures that confining pressure exists since uniaxial tensile strength can induce overestimate of the triaxial tensile strength. [ABSTRACT FROM AUTHOR]

Dominant crack algorithm (DCA) is a statistical micromechanics model for the dynamic tensile response of brittle materials. In the DCA model, both microscopic and macroscopic material parameters are included to construct the constitutive relation, and the damage evolution is described by the growth of the dominant crack. In this study, the sensitivity analysis of the microscopic parameters (i.e. the characteristic volume size a , the initial crack size c 0 , and the crack velocity related parameter m) in the DCA model is conducted. The results demonstrate that the dynamic tensile strength is sensitive to the value of c 0 / a. Compared with the influence of the c 0 / a on the dynamic tensile strength, the dynamic tensile strength is less sensitive to the variation of the characteristic volume size a or the variation of the crack velocity related parameter m. Furthermore, the DCA model is applied to predict the dynamic tensile response of Laurentian granite (LG). A nonlinear regression method - Particle Swarm Optimization (PSO) - is utilized to optimize the values of the microscopic parameters. The results indicate that the dynamic tensile response of LG predicted by the DCA modeling has a good agreement with that obtained from the experiments. Therefore, the DCA modeling is valid and applicable to describe the dynamic tensile response and predict the dynamic tensile strength of rock-like materials. • The sensitivity of the microscopic parameters in the DCA model is analyzed. • The dynamic tensile strength predicted by the DCA model is sensitive to the value of c 0 / a. • The dynamic tensile strength predicted by the DCA model is less sensitive to the value of a and m. • The predicted and measured dynamic tensile responses of rocks are consistent. • The DCA modeling is valid to predict the dynamic tensile response of rocks. [ABSTRACT FROM AUTHOR]