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This study systematically investigates the effects of high-power continuous wave laser (CWL) treatment on the mechanical behavior and failure mechanisms of SM400A steel, comparing these outcomes with those of untreated specimens. The findings reveal that while CWL treatment enhances surface hardness, it has minimal impact on the strength of thick structural steel components. However, excessive laser energy density leads to surface defects and softening of the microstructure, adversely affecting the material's toughness. This results in a reduction in elongation at fracture, transitioning the failure mode from ductile to brittle. The study concludes that to ensure the safe use of laser-treated structures, the laser energy density should be carefully controlled not to exceed 3000 J/cm2.

The tensile behavior of an injection mold glass fiber reinforced polyamide matrix composite was determined between 10-6-10-1 s-1 strain rates at 25, 65 and 90°C for the loading axis 0o, 30o and 90o to the fiber plane. Microscopic studies were conducted to identify typical fracture mechanism involved at different temperatures. The composite exhibited the highest flow stress and elastic moduli sensitivities on the strain rate in the 0o specimens, followed by the 30o and 90o specimens. The highest rate sensitivity was detected in the specimens tested at 25°C and the rate sensitivity declined as the test temperature increased from 25°C to 65 and 90°C. The observed rate sensitivity of the composite was ascribed to the rate sensitivity of the matrix while the elevated temperatures enhanced the fiber-matrix bonding.

Inspired by the microstructures of shells, SiC fibers (SiCf) are introduced into Ti layers, creating hybrid layers of SiCf/Ti, which are combined with Ti2AlNb foils to prepare multilayer SiCf/Ti–Ti2AlNb hybrids in a hot-pressed sintering instrument. The solid-phase bonding interface, mainly including the α+β biphasic structures and B2-rich phases, guarantees an ideal interface connection between the SiCf/Ti and Ti2AlNb layers after the sintering. Herein, the SiC fibers-made SiCf/Ti–Ti2AlNb presents a higher tensile strength and elasticity modulus on the tensile instrument of Model No. Byes (2010), compared with Ti/Ti2AlNb. During the tensile process, the brittle fractures of SiCffirst occur, and the loads are transferred to the bonding interface of the Ti2AlNb and Ti layers, generating the crack propagation and resulting in SiCf/Ti–Ti2AlNb fracture. This is mainly because the crack is extended in succession to the bonding interface that is composed of brittle phases such as O and α2, as well as ductile phases such as α, β and B2. This produces the ductile and brittle ruptures at the bonding interface, forming the ductile-brittle mixture fractures at the SiCf/Ti and Ti2AlNb interfaces. In the case of vertical fractures related to the fiber length, brittle fractures are observed on the SiC fibers, which produce high forces that affect their bonding interfaces, resulting in axial interstices and transverse fractures. These obtained results demonstrate a novel method for structural design and fabrication of the innovative composite materials.

This paper focuses on the high-temperature tensile failure mechanism of RTM (resin transfer moulding)-made symmetric and asymmetric composite T-joints. The failure modes as well as the load-displacement curves of symmetric (three specimens) and asymmetric (three specimens) composite T-joints were determined by tensile tests at room and high temperatures. Progressive damage models (PDMs) of symmetric and asymmetric composite T-joints at room and high temperatures were established based on mixed criteria, and the result predicted from the aforementioned PDMs were compared with experimental data. The predicted initial and final failure loads and failure modes are in good agreement with the experimental results. The failure mechanisms of composite T-joints at different temperatures were investigated by scanning electron microscopy. The results reveal that while the failure mode of asymmetric T-joints at high temperatures resembles that at room temperature, there is a difference in the failure modes of symmetric T-joints. The ultimate failure load of symmetric and asymmetric T-joints at elevated temperatures increases and reduces by 18.4% and 4.97%, albeit with a more discrete distribution. This work is expected to provide us with more knowledge about the usability of composite T-joints in elevated temperature environments.

Since Al-Mg-Si alloys are widely used in the transportation industry, it is important to produce a sound and robust weld between the sheets of these alloys. The focus of this work is on the tensile-shear and cross-tension strengths of the consumable pin-friction stir spot welds (CP-FSSWs) without an exit-hole between the Al-6061 aluminum sheets. Before welding, a hole was created at the joint region in the base sheets and then, it was filled using a rotating consumable pin. The tensile-shear, cross-tension, and microhardness tests were employed to evaluate the mechanical properties of the spot welds. The results showed that the pre-created hole was entirely filled during the welding process. While a complete bond was formed between the consumable pin and the lateral surface of the hole, there were three distinct regions at the interface of the pin and the bottom of the hole: complete bond, kissing bond, and defects. Enhancement of the tool rotational speed decreased the area of the complete bond in the weld compared to the other regions. A linear relationship existed between the bonding area and weld failure load in the cross-tension test. The proposed relationship approved the impact of the swirly region at the interface of the base sheets on the weld strength. While in the cross-tension test, the weld failure load decreased from ∼2800 to ∼1950 N, it improved from ∼10,500 to ∼12,000 N in the tensile-shear test with enhancement of the tool rotational speed from 700 to 2000 rpm. The hardness measurements demonstrated that there was no common heat affected zone softening after CP-FSSW.

Two types of the weld joint of Inconel 617 alloy were produced using gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW) processes with ERNiCrCoMo-1 filler metal and ENiCrCoMo-1 electrode, respectively. The weld metal showed the segregation of the principle alloying elements like Mo and Cr along the inter-dendritic spaces, triggering the formation of secondary phases. The microstructure characterization of the interface ensured the high dilution, which could be attributed to the closeness in melting point and chemistry of base and filler metal. Microhardness variation, tensile testing at room and high temperature, and Charpy impact test were conducted to investigate the effect of the Mo segregation in the weld zone and heterogeneity in the microstructure of weldments on the mechanical behavior of both the welded joints. The cross-weld tensile tests were conducted at room temperature and 550°C. The tensile test samples failed from the weld zone for each condition with a tensile strength value close to the base metal, which ensured the applicability of the joint for end service. The tensile strength of GTAW-RT, GTAW-HT, SMAW-RT, and SMAW-HT were measured as 766 ± 22 MPa, 570 ± 5 MPa, 760 ± 7 MPa, and 600 ± 8 MPa, respectively. A non-uniform hardness plot was witnessed with the hardness of the GTAW-weld and SMAW-weld zone of 257 ± 8 HV and 285 ± 5 HV, respectively, in the transverse direction. The impact toughness of the weld zone was 84 ± 2 J and 48 ± 4 J for GTAW and SMAW weld zone. The average impact toughness of the GTAW-weld zone was approximately 42% higher than the value of the SMAW-weld zone. In a nutshell, it can be concluded that the welded joint of Inconel 617 produced using the GTAW process with ERNiCrCoMo-1 filler had the best metallurgical and mechanical properties.

Three-dimensional (3D) needled carbon fiber reinforced carbon and silicon carbide (C/C–SiC) composites have the significant advantages of low density, high strength, and long lifespan, which are widely used in aerospace and other industrial fields. In this paper, based on the microstructure of the composites, a multi-scale finite element model is established to predict their mechanical properties and failure behaviors under the tensile load. The multi-scale model has been validated by the static tensile test and the microstructure of fracture. With this model, the effects of the fiber volume fraction, the interfacial bonding strength, the content of residual silicon (Si) elements, and the porosity on the mechanical properties of needled C/C–SiC composites are systematically analyzed. The results show that the stress-strain curve of the composites under the longitudinal tensile load has two nearly linear segments. The final failure strength of the composites increases with the increase of the interfacial bonding strength, the fiber volume fraction and residual Si elements, while decreases with the increase of the porosity. In addition, based on the established multi-scale finite element model, the damage evolution process and failure mechanism of the needled composites are investigated in detail. The proposed scheme could effectively predict the mechanical properties of the needled C/C–SiC composites and capture the microscopic damage evolution, which would help to optimize the design of composites.

The addition of steel fibres to concrete can result in changes to its mechanical properties. Therefore, research has been conducted on the characterisation of unidirectional tensile performance failure of steel fibre nano high-strength concrete. Increasing the amount of steel fibre can significantly improve the concrete's crack resistance, tensile strength, and flexural stiffness. However, it also affects the deformation characteristics of concrete and reduces its stiffness. Research has shown that as the steel fibre content increases, the total deformation of concrete increases while the crack propagation width decreases. Excessive steel fibre content can lead to a decrease in the stiffness of concrete and adverse degradation. In practical applications, the appropriate amount of steel fibre should be selected based on the specific situation to ensure the mechanical properties and effectiveness of concrete.

Dynamic tensile fracturing of two quasi-brittle geomaterials during high strain rate spalling as observed in situ utilizing ultra-high speed single bunch X-ray phase-contrast radiography is presented (image acquisition rate of 1.4 MHz with 32 μm pixel size). A spalling experimental set-up, based on a single Hopkinson bar, has been developed to apply indirect dynamic tension with strain rates up-to 1000 s-1. Experiments were performed on a pink granite (low porosity content and large quantity of pre-existing cracks) and an ultra-high strength concrete (comparatively high porosity content and low quantity of pre-existing cracks). The in situ results show that the two tested materials exhibit notable differences in tensile failure patterns. In parallel, point-wise measurements of the rear face velocity have been obtained showing a pronounced difference in the velocity pull-back response. X-ray micro-tomography inspection has been performed on the samples post-mortem. The effects on the microstructure and the initial quantity of defaults on the observed dynamic tensile failure are discussed.

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Tensile failure in superplastic alumina shows a close similarity to ductile failure in metallic materials containing microvoids or hard inclusions. Microcracking, which appears as strain exceeding ~ 90% of the failure strain and leading to macroscopic cracking for final failure, is not caused by the propagation of the largest preexistent defects, but by extensive cavity coalescence. Such coalescence is found to occur as the thickness of the intervoid matrix decreases to a certain level due to an increase in the number and size of cavities. The data also show that there is no explicit critical grain size for the onset of microcracking, although microcracking and failure tend to occur at smaller strains as the initial grain size increases.

Sheet molding compounds (SMCs) as an alternative material for low-cost and lightweight automotive structural components require special attention to their failure behavior and collision safety. This study aims to analyze the energy-absorbing response and variability of unsaturated polyester matrix SMCs under the range of strain rates from 10−3/s to 500/s through quasi-static and dynamic tensile tests. Additionally, the tensile process and fracture morphology were characterized using Digital Image Correlation and Scanning Electron Microscopy to reveal the underlying rate-dependent failure mechanism. The results demonstrate a pronounced positive correlation between the tensile strength and absorbed energy of SMCs with strain rates. Specially, the absorbed energy exhibits substantial variability, primarily attributable to the plastic damage behavior during the nonlinear phase. A transition in the failure mode from debonding to pseudo-delamination, accompanied by a more extensive failure area at high strain rates, serves as the main mechanism for enhancing the material energy absorption capacity.

In this paper, shale gas cores from the Lower Silurian Longmaxi Formation in the Zhaotong National Shale Gas Demonstration Area were selected to study the hydration effect of different fluids on the fracture morphology inside the shale, the rock tensile strength and the Brazilian tensile failure mode. Fresh water and slick water were adopted for hydration pretreatments and the CT technique was used to compare the changes of the fabric in the shale. Then, Brazilian tensile tests were carried out to study the tensile strength and tensile failure modes of the shale specimen after hydration pretreatment. Finally, two horizontal wells in the study area were selected to perform pilot tests of hydration pretreatment in their fracturing operation sites. And the following research results were obtained. First, in the process of spontaneous imbibition, the hydration effect of fresh water is superior to that of slick water in promoting the fracture complexity of marine shale in the same hydration duration. Second, fresh water has greater surface tension and lower viscosity and its hydration effect can not only promote the propagation of original fractures but induce new micro-fractures or branches, while the hydration effect of slick water mainly promotes the propagation of original fractures. Third, due to hydration effect, marine shale is damaged and its tensile strength is reduced. After the hydration pretreatment by fresh water and slick water, the tensile strength of the shale specimens are reduced by 35.6% and 18.1%, respectively. Fourth, according to the propagation paths of main fractures, the Brazilian tensile failure modes of hydrated shale can be divided into four types (i.e., step shaped, dog-leg shaped, branching shaped and arc shaped) or their combinations, while the tensile failure mode of unhydrated shale is only a straight line. Fifth, hydration effect can effectively increase the complexity of the hydraulic fractures in marine shale, so if the conditions permit, it is recommended to inject a certain amount of fresh water at a high pumping rate within the limited pressure after perforation and to shut in the well until the hydraulic fracturing operation. And in order to reduce the difficulties of pumping the proppant during the hydraulic fracturing operation, a pumping strategy of “low proppant concentration, large volume of slurries” can be adopted to reach the expected proppant volume.

Fracture toughness and surface energy density are critical parameters in the simulation of hydraulic fracturing in shale formations. In this study, a microscopic insight into the mechanisms of tensile failure in kerogen is advanced by molecular dynamics simulations for the first time. The elastic properties, critical stress, surface energy density, and fracture toughness of kerogen are analyzed systematically. Our work reveals that kerogen is potentially a weak component in shale, which may serve as a region of fracture initiation and preferential fracture propagation path. The critical energy release rate Gcis higher than the doubled surface energy density γs(Gc≥ 2γs), which indicates that there may be pronounced plastic deformation in kerogen in the tensile failure. This work sets the stage for the determination of various shale mechanical properties and surface energy density to examine fracturing effectiveness in shale media from the molecular scale.

Softening of the heat-affected zone degrades the mechanical properties of high-strength steel-welded joints. This work revealed the key mechanism to suppress the adverse effects of the soft zone on joint performance by analyzing the constraint between different zones. The base metal (BM) can compete with the soft zone for plastic deformation when the soft zone is strongly constrained by the hard zone, which helps to disperse local strain and prevent premature necking. The constraint mode of the soft zone tends to evolve asymmetrically from bilateral to unilateral during the deformation. Reducing the width of the soft zone helps to achieve unilateral constraint, thus shifting the fracture location from the soft zone to the BM.

Sand production is a challenging issue in upstream oil and gas industry, causing operational and safety problems. Therefore, before drilling the wells, it is essential to predict and evaluate sanding onset of the wells. In this paper, new poroelastoplastic stress solutions around the perforation tunnel and tip based on the Mohr–Coulomb criterion are presented firstly. Based on the stress models, a tensile failure induced sanding onset prediction model for cased-perforated gas wells is derived. Then the analytical model is applied to field data to verify its applicability. The results from the perforation tip tensile failure induced sanding model are very close to field data. Therefore, this model is recommended for forecasting the critical conditions of sand production analysis. Such predictions are necessary for providing technical support for sand control decision-making and predicting the production condition at which sanding onset occurs.

Sills, saucer‐shaped sills, and cone sheets are fundamental magma conduits in many sedimentary basins worldwide. Models of their emplacement usually approximate the host rock properties as purely elastic and consider the plastic deformation to be negligible. However, many field observations suggest that inelastic damage and shear fracturing play a significant role during sill emplacement. Here we use a rigid plasticity approach, through limit analysis modeling, to study the conditions required for inelastic deformation of sill overburdens. Our models produce distinct shear failure structures that resemble intrusive bodies, such as cone sheets and saucer‐shaped sills. This suggests that shear damage greatly controls the transition from flat sill to inclined sheets. We derive an empirical scaling law of the critical overpressure required for shear failure of the sill's overburden. This scaling law allows to predict the critical sill diameter at which shear failure of the overburden occurs, which matches the diameters of natural saucer‐shaped intrusions' inner sills. A quantitative comparison between our shear failure model and the established sill's tensile propagation mechanism suggests that sills initially propagate as tensile fractures, until reaching a critical diameter at which shear failure of the overburden controls the subsequent emplacement of the magma. This comparison also allows us to predict, for the first time, the conditions of emplacement of both conical intrusions, saucer‐shaped intrusions, and large concordant sills. Beyond the application to sills, our study suggests that shear failure significantly controls the emplacement of igneous sheet intrusions in the Earth's brittle crust. We investigate the conditions for inelastic deformation induced by inflating sills for which we propose an empirical scaling lawThe damage patterns calculated in our simulations resemble the inclined sheets of cone sheets and saucer‐shaped sillsSills propagate laterally by tensile opening at sill tips, but at a given size shear failure may become favored

The aim of the present study is to utilize fractographic methods employing scanning electron microscope (SEM) images to investigate the effects of build direction and orientation on the mechanical response and failure mechanism for Acrylonitrile–Butadiene–Styrene (ABS) specimens fabricated by fused deposited modeling (FDM). The material characterized here is ABS-M30 manufactured by Stratasys, Inc. Measurements of tensile strength, elongation-at-break and tensile modulus measurements along with the failure surfaces were characterized on a range of specimens at different build direction and raster orientation: ±45°, 0°, 0/90°, and 90°. The analysis of mechanical testing of the tensile specimens until failure will contribute to advances in creating stronger and more robust structure for various applications. Parameters, such as build direction and raster orientation, can be interdependent and exhibit varying effects on the properties of the ABS specimens. The ABS-M30 specimens were found to exhibit anisotropy in the mechanical response when exposed to axial tensile loading. The stress-strain data was characterized by a monotonic increase with an abrupt failure signifying brittle fracture. In certain combinations of build direction and raster orientation tensile failure was preceded by slight softening. The tensile strength and modulus, and elongation-at-break were found to be highly dependent upon the raster orientation and build direction. The relationship between the mechanical properties and failure was established by fractographic analysis. The fractographic analysis offers insight and provides valuable experimental data for the purpose of building structures in orientations tailored to their exemplified strength. For instance, specimens loaded such that bonds between adjacent rasters are the primary load bearing mechanism offer the least significant failure resistance. Other examples are shown where artifacts of the FDM fabrication process act to enhance tensile strength when configured properly with respect to the load. The results highlighted in this study are fundamental to the development of optimal design of complex ultra-light structure weight with increased structural efficiency. The study also presents a systematic scheme employing analogs to traditional fiber-reinforced polymer composites for the designation of build orientation and raster orientation parameters.

This paper investigates the influence of concrete/gypsum bedding layers and their orientation angles on the tensile failure mechanism in the three-point bending test based on experiments and numerical simulations. Rectangular samples containing different combinations of concrete and gypsum layers were prepared, i.e. one layer of gypsum and one layer of concrete, one layer of gypsum and two layers of concrete, and two layers of gypsum and two layers of concrete. In each configuration, bedding layer angles varied between 0° and 90° with increment of 30°. A total of 36 specimens including 12 configurations were prepared and tested. In addition, numerical simulations were conducted on the concrete/gypsum bedding layers at different angles of 0°, 15°, 30°, 45°, 60°, 75°, and 90°. Results show that the bedding layer orientation and bedding layer thickness affect the observed tensile failure process including the failure pattern and tensile strength. A pure tensile failure occurred when the bedding layer angle was 0°, while a sliding failure evolved by increasing the joint angle. When the bedding layer angle was 90°, the failure in boundary of layer was observed. Specimens with one layer of concrete and one layer of gypsum at 0° inclination angle had the highest tensile strength. However, increasing the number of layers and inclination angles decreased the tensile strength of specimens as the number of weak layers in the direction of loading increased.

Welding armour steel plate is a crucial task in the construction of combat vehicle structures. The shield metal arc welding (SMAW) with austenitic stainless steel (ASS) filler is used to prepare the defect free weld joints under suitable welding parameters. Tensile property enhancement in the fusion zone of the weld joint inhibits bullet penetration in a combat environment. An examination has also been conducted into the effect of microstructures in base metal, weldments, and the influence on tensile fractured surfaces. Tensile failure occurs in the weld centreline due to the reduced tensile strength of the filler material. When compared to the relevant literature, these welds demonstrated 48% joint efficiency and good tensile strength. This present work was development of a finite element analysis (FEA) model to analyse the tensile failure of base metal and weld joints with different factors of safety (FOS) such as FOS 0, FOS 1.5, and FOS 3. The FEA was carried out to predict the load-carrying capacity under tensile load. The simulation and experimental findings concur, implying that the suggested approaches were utilized effectively for structural analysis of armour weld joint using typical FEA techniques.

Natural and synthetic inclusions may modify the tensile strength and the failure pattern of surrounding rocks. Understanding the failure mechanism could improve rock failure prediction and induced geohazard mitigation. Due to difficulties in controlling the geometrical and mechanical properties of embedded inclusions in the laboratory, we simulate the dynamic tensile failure of inclusion-bearing rock specimens using a two-dimensional particle flow code model. We investigate the effects of strength ratio, loading rate, and treatment temperature on the nominal tensile strength of inclusion-bearing specimens and discuss the brittleness index to interpret the strength evolution. We identify the dominant effect on the nominal tensile strength as strength ratio for a low tensile strength inclusion and loading rate and treatment temperature for a high tensile strength inclusion. The change in dominant effect is associated with induced cracks primarily formed in the rock/inclusion part with lower tensile strength and highlights key factors to control inclusion-induced rock failure. This study also reveals that low strength, large size inclusions promote a decrease in brittleness index and accelerate the degradation of inclusion-bearing rocks.

Static and dynamic splitting tests were conducted on ring marble specimens with different internal diameters to study the tensile strength and failure modes with the change of the ratio of internal radius to external radius (ρ) under different loading rates. The results show that the dynamic tensile strength of disc rock specimen is approximately five times its static tensile strength. The failure modes of ring specimens are related to the dimension of the internal hole and loading rate. Under static loading tests, when the ratio of internal radius to external radius of the rock ring is small enough (ρ<0.3), specimens mostly split along the diametral loading line. With the increase of the ratio, the secondary cracks are formed in the direction perpendicular to the loading line. Under dynamic loading tests, specimens usually break up into four pieces. When the ratio ρreaches 0.5, the secondary cracks are formed near the input bar. The tensile strength calculated by Hobbs' formula is greater than the Brazilian splitting strength. The peak load and the radius ratio show a negative exponential relationship under static test. Using ring specimen to determine tensile strength of rock material is more like a test indicator rather than the material properties.

Overpressure within a circular magmatic chamber embedded in an elastic half space is a widely used model in volcanology. However, this overpressure is generally assumed to be bounded by the bedrock tensile strength since gravity is neglected. Critical overpressure for wall failure is thus greater. It is shown analytically and numerically that wall failure occurs in shear rather than in tension, because the Mohr–Coulomb yield stress is less than the tensile yield stress. Numerical modelling of progressively increasing overpressure shows that bedrock failure develops in three stages: (1) tensile failure at the ground surface; (2) shear failure at the chamber wall; and (3) fault connection from the chamber wall to the ground surface. Predictions of surface deformation and stress with the theory of elasticity break down at stage 3. For wall tensile failure to occur at small overpressure, a state of lithostatic pore-fluid pressure is required in the bedrock which cancels the effect of gravity. Modelled eccentric shear band geometries are consistent with theoretical solutions from engineering plasticity and compare well with shear structures bordering exhumed intrusions. This study shows that the measured ground surface deformation may be misinterpreted when neither plasticity nor pore-fluid pressure is accounted for.Supplementary material:The numerical benchmark data are available at: http://www.geolsoc.org.uk/SUP18517.

A new continuum model for directional tensile failure has been developed that can simulate weakening and void formation due to directional tensile failure. The model is developed within the context of a properly invariant nonlinear thermomechanical theory. A second order damage tensor is introduced which allows simulation of weakening to tension applied in one direction, without weakening to subsequent tension applied in perpendicular directions. This damage tensor can be advected using standard methods in computer codes. Porosity is used as an isotropic measure ouf volumetrie void strain and its evolution is influence by tensile failure. The rate of dissipation due to directional tensile failure takes a particularly simple form, which can be analyzed easily. Specifically, the model can be combined with general constitutive equations for porous compaction and dilation, as well as viscoplasticity. A robust non-iterative numerical scheme for integrating these evolution equations is proposed. This constitutive model has been implemented into an Eulerian shock wave code with adaptive mesh refinement. A number of simulations of complicated shock loading of different materials have been performed including problems of fracture of rock. These simulations show that directionality of damage can play a significant role in material failure.

The study presented in this paper discusses a discontinuum-based model for investigating strength and failure in sedimentary rocks. The model has been implemented by UDEC to incorporate an innovative orthotropic cohesive constitutive law for contact. To reach this purpose, a user-defined model has been established by creating dynamic link libraries (DLLs) and attaching them into the code. The model reproduces rock material by a dense collection of irregular-sized deformable particles interacting at their cohesive boundaries which are viewed as flexible contacts whose stress-displacement law is assumed to control the fracture and the fragmentation behaviours of the material. The model has been applied to a sandstone. The individual and interactional effects of the microstructural parameters on the material compressive and tensile failure responses have been examined. In addition, the paper presents a new methodical calibration procedure to fit the modelling microparameters. It is shown that the model can successfully reproduce the rock mechanical behaviour quantitatively and qualitatively. The study also shows how discontinuum-based modelling can be used to characterize the relation between the microstructural parameters and the macro-scale properties of a material.

AlN passivation layer-mediated improvement in tensile failure of ZnO:Al thin films on polyethersulfone substrates is investigated. ZnO:Al films without any passivation layer were brittle with a crack-initiating bending strain εcof only about 1.13% with a saturated crack density ρsof 0.10 μm−1and a fracture energy Γ of 49.6 J m−2. On passivation by an AlN overlayer, the fracture energy of the system increased considerably and a corresponding improvement in εcwas observed. AlN layers deposited at higher discharge powers yielded higher fracture energy and exhibited better performance in terms of εcand ρs.

The sedimentologic and tectonic histories of clastic cap rocks and their inherent mechanical properties control the nature of permeable fractures within them. The migration of fluid through mm- to cm-scale fracture networks can result in focused fluid flow allowing hydrocarbon production from unconventional reservoirs or compromising the seal integrity of fluid traps. To understand the nature and distribution of subsurface fluid-flow pathways through fracture networks in cap-rock seals we examine four exhumed Paleozoic and Mesozoic seal analogs in Utah. We combine these outcrop analyses with subsidence analysis, paleo-loading histories, and rock-strength testing data in modified Mohr-Coulomb-Griffith analyses to evaluate the effects of differential stress and rock type on fracture mode. Relative to the underlying sandstone reservoirs, all four seal types are low-permeability, heterolithic sequences that show mineralized hydraulic-extension fractures, extensional-shear fractures, and shear fractures. Burial-history models suggest that the cap-rock seal analogs reached a maximum burial depth >4 km (2.5 mi) and experienced a lithostatic load of up to 110 MPa (15,954 psi). Median tensile strength from indirect mechanical tests ranges from 2.3 MPa (334 psi) in siltstone to 11.5 MPa (1668 psi) in calcareous shale. Analysis of the pore-fluid factor (λv = Pf/σv) through time shows changes in the expected failure mode (extensional shear or hydraulic extension), and that failure mode depends on a combination of mechanical rock properties and differential stress. As expected with increasing lithostatic load, the amount of overpressure that is required to induce failure increases but is also lithology dependent. [ABSTRACT FROM AUTHOR]

The influence of hydrogen embrittlement on the tensile failure of 316L stainless-steel notched bars is phenomenologically modeled in this paper. Tensile tests of notched samples suffering hydrogen embrittlement show that hydrogen damage consists in multicracking in the area surrounding the notch, but the macromechanical behavior of the specimens remains ductile. This suggests two different ways for modeling the damage in order to explain its effect on the tensile failure load. The Notch Extension Model (NEM) considers that damage intensity around the notch is high enough to cancel out the mechanical resistance of this multicracked zone, so it assumes that the hydrogen effect is equivalent to a geometric enlargement of the notch. In the Notch Cracking Model (NCM), it is assumed that high intensity damage is concentrated at the notch root and causes this area to behave as a macroscopic crack that extends the original notch. Experimental values from tests and calculated values from models indicate that the notch extension model describes well the influence of hydrogen on the tensile notch behavior of 316 L stainless steel.

The tensile strength of skin is associated, in part, with its potential for laceration from impact. The quasi-static tensile strength of skin depends on orientation. The objective of this study was to determine whether the strength of skin in high speed tensile failure experiments exhibits a similar dependence on orientation. Tensile experiments were conducted at 6000 percent/s and 30 percent/s on dorsal skin of rats aged 1–6 months. Experiments were performed on specimens cut perpendicularly and longitudinally to the spine at cranial and caudal locations. The tensile failure properties depended on location, orientation, age and strain rate. The strength was dependent on orientation to the same degree in high and low speed tests. This helps explain why accident statistics show that skin lacerates preferentially on the body.

Based on the progressive failure analysis method, taking account of 7 kinds of failure modes: stitch thread failure mode, resin extend (or compress) failure mode, fibre extend (or compress) failure mode, extend (or compress) delamination failure mode, a new failure analysis FE model was proposed for predicting the tensile strength of stitch-reinforced composite T-stiffened structures. The 3D solid element and truss element were used to simulate laminate and stitch thread individually in the FE model. The Hashin failure criterion and stiffness degradation technology are used to analyze damage failure of the stitch T-stiffened structure. Comparing the initial and final damage failure strength with those of experiments on stitch composite T-stiffened structures validated the Python secondary development program for the FE model presented in the paper. There was good agreement between the failure strength from the damage failure analysis and that of the experiment. This indicated that the model was correct, and that it could be a reference for stitch-reinforced composite design and analysis.

Tensile failure mechanisms in type I carbon fibre-reinforced epoxy resin have been studied by examining the modes of failure of cured and semi-cured CFRP and of fibre bundle specimens. The rigid matrix in the cured material modified the appearance of the fractured specimen but by detecting the acoustic emission generated during loading the basic fibre bundle behaviour was found to exert a major influence on fracture. Microscopic examination of fractured CFRP specimens has revealed that consecutive fibre failure may be restricted to sub-bundles as a result of shearing between these sub-bundles, and that the material is weakened by a number of internal failures that are not necessarily connected. Ultimate failure seems to be statistically determined and it is a characteristic of the material that some scatter in the strength of CFRP must be expected.

Variation of critical cut lengthIc in tensile failure of rubber vulcanizates has been studied with respect to the following variables: addition of short silk fibre, fibre concentration and orientation, ageing, reinforcing carbon black filler and elevated temperature. Strain crystallizing rubbers, e.g. natural (NR) and polychloroprene (CR), show higherIc values than non-strain crystallizing nitrile rubber (NBR). The addition of short fibres was found to cause an increase inIc in all cases. The increase is more prominent in the case of NBR than for NR and CR. TheIc values for unfilled NBR vulcanizates are low and a marginal increase is noted on the addition of carbon black. Addition of short fibres leads to a significant improvement in theIc values, which show a gradual increase with increase in fibre concentration in the composites.Ic exists only in the composites wherein the fibres are oriented along the direction of application of tensile stress rather than across it, and the decrease in tensile strength is marginal at the initial stages but a sharp fall is observed with increasing size of cut lengths. On ageing,Ic values for composites increase while those for unfilled vulcanizates decrease. Critical cut length values for the fibre reinforced composites at a higher temperature (e.g. 100° C) remained unchanged, but dropped in the case of unfilled vulcanizates.

Tensile tests have been performed at up to five different displacement rates, from about 1 mm/s to over 20,000 mm/s, on braided glass-fibre tubes of both square and circular cross-section and the corresponding force-displacement curves have been derived. In general both the maximum tensile force and the displacement at failure increase with increasing loading rate, implying a greater energy absorbing capability at the higher deformation rates. At all rates of loading the square cross-section tubes support a lower maximum force and fail at a higher overall deformation. Two stages in the failure process are considered, the realignment of the fibres against the resistance of the matrix followed by the tensile failure of the fibres. Both these processes are found to be rate dependent.

Scanning electron microscopy and acoustic emission are used to investigate the initial stages of tensile failure in unflawed polycrystalline alumina. It is found that deformation twinning plays an important role in crack initiation even at low homologous temperatures, and that the temperature-dependent strength behaviour between 23 to 410° C is controlled by twinning.

Abstract: The tensile failure strength of ceramic composites can be measured by tests in bending or in tension, but care must be exercised over the experimental conditions. The strength values obtained are dependent on the test method and specimen size. It is shown that differences between strengths measured in bend and tensile tests can be understood in terms of the statistical distribution of the strengths of individual fibres.

Abstract: An ion microprobe has been used to identify silicon as the embrittling agent responsible for the tensile failure of a Pt-30Rh-8W alloy. Silicon was found to be segregated on the grain boundaries of the alloy, and to have a concentration gradient along them from the outer surfaces toward the interior of the sample.

Results are discussed from experimental and theoretical studies on the tensile failure of short, steel fiber‐reinforced mortar/concrete (SFRC) composites. A displacement‐controlled test method for conducting stable fracture tests on tension‐weak brittle materials developed in an earlier study has been used for conducting uniaxial tension tests. Several concrete, mortar, paste, and SFRC mixes were tested. Fracture of SFRC in tension is observed to be influenced largely by the matrix softening behavior, the fiber‐matrix interfacial response, and its composition parameters. The theoretical model proposed for the idealized SFRC composite takes into account these two primary nonlinear aspects of the failure mechanism in such composites, i.e.: (1) The inelastic behavior of the fiber‐matrix interface; and (2) the softening characteristics of the matrix. The model, in addition, is also realistically sensitive to the reinforcement parameters like fiber volume content, aspect ratio, and the elastic properties of the fiber.

Composite soil-nailing is a new technology developed from abroad in recent years, to be used in excavation of soil, slope stability. This paper studied the stress and deformation of composite soil nailing wall by nonlinear FEM. According to the structure characteristic, the finite element analysis for composite soil nailing construction process is carried out. Based on geotechnical elastic-plastic constitutive model, the adopted failure criterion was a composite Drucker-Prager criterion with tension cut-off. A kind of rotational Goodman interface element is employed to simulate the behavior of interface between the soil-mixed cement which forms the barrier of seepage flow along the boundary of foundation pit, and soil ground. Through the comparative analysis with on-site monitoring data, the finite element calculation results have good precision.

AbstractAbstractWeibull strength size scaling in a rotary ground, hot pressed boron carbide is described when strength test coupons sampled effective areas from very small (~0·001 mm2) to very large (~40?000 mm2). The testing of this ceramic is relevant because it is a candidate material for use in personnel armour. Equibiaxial flexure and Hertzian testing were used for the strength testing. Characteristic strengths for several different specimen geometries are analysed as a function of effective area. Characteristic strength was found to substantially increase with decreased effective area and exhibited a bilinear relationship. Machining damage limited strength as measured with equibiaxial flexure testing for effective areas greater than ~1 mm2, and microstructural scale flaws limited strength for effective areas <0·1 mm2for the Hertzian testing. The selections of a ceramic strength to account for ballistically induced tile deflection and expanding cavity modelling are uniquely considered in context with the measured strength size scaling.

Weibull strength size scaling in a rotary ground, hot pressed boron carbide is described when strength test coupons sampled effective areas from very small (∼0·001 mm2) to very large (∼40 000 mm2). The testing of this ceramic is relevant because it is a candidate material for use in personnel armour. Equibiaxial flexure and Hertzian testing were used for the strength testing. Characteristic strengths for several different specimen geometries are analysed as a function of effective area. Characteristic strength was found to substantially increase with decreased effective area and exhibited a bilinear relationship. Machining damage limited strength as measured with equibiaxial flexure testing for effective areas greater than ∼1 mm2, and microstructural scale flaws limited strength for effective areas <0·1 mm2for the Hertzian testing. The selections of a ceramic strength to account for ballistically induced tile deflection and expanding cavity modelling are uniquely considered in context with the measured strength size scaling.

The investigation on the behavior of a specimen under uniaxial tension and the process of microfracture attracts considerable interest with a view to understanding strength characterization of brittle materials. Little attention has been given to the detailed investigation of influence of heterogeneity of rock on the progressive failure leading to collapse in uniaxial tension. In this paper, a numerical code RFPA3D (Realistic Failure Process Analysis), newly developed based on a three-dimensional model, to simulate the fracture process and associated fractal characteristic of heterogeneous rock specimen subjected to direct uniaxial tension. Specimens with different heterogeneity are prepared to study tension failure. In a relatively homogeneous specimen, the macrocrack nucleates abruptly at a point in the specimen soon after reaching peak stress. In more heterogeneous specimens, microfractures are found to appear diffusely throughout the specimen, and the specimens show more ductile failure behavior and a higher residual strength. Development of fractal theory may provide more realistic representations of rock fracture. The fractal dimension of distributed AE is computed during the fracture process. For all specimens, the fractal dimension increases as the loading proceeds, and it reaches the peak value when macrocrack nucleates abruptly. It is also found that fractures scatter more diffusely in relatively heterogeneous specimens, and the fractal dimension has a smaller value. The homogenous rock specimens have flat and smooth rupture faces which are consistent with the fractal results.

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The stress distribution on the midsection of a pure bending beam where tensile strain localization band initiates on the tensile side of the beam and propagates within the beam is analyzed. Using the static equilibrium condition on the section of the midspan of the beam and the assumption of plane section as well as the linear softening constitutive relation beyond the tensile strength, the expressions for the length of tensile strain localization band and the distance from the tip of the band to the neutral axis are derived. After superimposing a linear unloading stress distribution over the initial stress distribution, the residual stress distribution on the midsection of the beam is investigated. In the process of strain localization band’s propagation, strain-softening behavior of the band occurs and neutral axis will shift. When the unloading moment is lower, the length of tensile strain localization band remains a constant since the stress on the base side of the beam is tensile stress. While, for larger unloading moment, with an increase of unloading moment, the length of tensile strain localization band decreases and the distance from the initial neutral axis to the unloading neutral axis increases. The neutral axis of midsection of the beam will shift in the unloading process. The present analysis is applicable to some metal materials and many quasi-brittle geomaterials (rocks and concrete, etc) in which tensile strength is lower than compressive strength. The present investigation is limited to the case of no real crack. Moreover, the present investigation is limited to the case that the length of strain localization band before unloading is less than half of depth of the beam. Otherwise, the residual tensile stress above the elastic neutral axis will be greater than the tensile strength, leading to the further development of tensile strain localization band in the unloading process.

Mechanisms of blast-induced Traumatic Brain Injury (BTBI), particularly those linked to the primary pressure wave, are still not fully understood. One possible BTBI mechanism is cavitation in the cerebrospinal fluid (CSF) caused by CSF tensile failure, which is likely to increase strain and strain rate in the brain tissue near the CSF. Blast loading of the head can generate rarefaction (expansion) waves and rapid head motion, which both can produce tensile forces in the CSF. However, it is not clear which of these mechanisms is more likely to cause CSF tensile failure. In this study, we used a high-fidelity 3-dimensional computational model of the human head to test whether the CSF tensile failure increases brain deformation near the brain/CSF boundary and to determine the key failure mechanisms. We exposed the head model to a frontal blast wave and predicted strain and strain rate distribution in the cortex. We found that CSF tensile failure significantly increased strain and strain rate in the cortex. We then studied whether the rapid head motion or the rarefaction wave causes strain and strain rate concentration in cortex. We isolated these two effects by conducting simulations with pure head motion loading (i.e. prescribing the skull velocity but eliminating the pressure wave) and pure blast wave loading (i.e. eliminating head motion by fixing the skull base). Our results showed that the strain increase in the cortex was mainly caused by head motion. In contrast, strain rate increase was caused by both rapid head motion and rarefaction waves, but head motion had a stronger effect on elevating strain rate. Our results show that rapid motion of the head produced by blast wave is the key mechanism for CSF tensile failure and subsequent concentration of strain and strain rate in cortex. This finding suggests that mitigation of rapid head motion caused by blast loading needs to be addressed in the design of protective equipment in order to prevent the tensile failure of CSF.

The dependence of temperature and strain rate on the mechanical properties of pineapple leaf fiber (PALF) reinforced polyethylene (LDPE) composites has been investigated. The effects of fiber loading, fiber orientation, and fiber treatment on the test properties were studied. The tensile strength of the composite was found to be decreased and elongation increased up to 40'C, decreasing thereafter as the temperature was increased from 40 to 80'C. Failure at low temperature and or high strain rate occurred due to brittle matrix fracture, which was evident from SEM micrographs. Activation energy of the failure was calculated using an Arrhenius equation. Failure envelope is generated in order to understand the effect of temperature and strain rate on composite properties. Composites with longitudinally oriented fibers showed higher retention of tensile properties at elevated temperatures. Fibers treated with poly(methylene) poly(phenyl) isocyanate (PMPPIC) showed maximum retention in strength at higher temperature.

The nonlinear finite deformations and ultimate failure modes of photo-cured polymers are closely related to the ambient temperatures, typically exhibiting enhanced stretchability and a peak of ultimate break strain near the glass transition temperature Tg. The origin of this type of temperature-dependent failure phenomenon lies in the evolution of visco-elasto-plastic flowing dynamics as well as the alteration of polymer chain mobility during glass transition. In the past few decades, theoretical models for the strength of polymers were developed independent of the visco-elasto-plastic deformation history and the glass transition dynamics. These models could not provide reasonable explanations for the peak of ultimate break strain in photo-cured polymers, nor predict the poor stretchability at ultra-low and ultra-high temperatures. In this paper, we propose a general model for the temperature-dependent deformation and tensile failure of photo-cured polymers, in which the breaking phenomenon is dominated by a competition between the brittle failure at low temperature, the visco-plastic failure at moderate temperature and the hyperelastic failure at high temperature. Through the comparison between theoretical predictions and typical experiments, the model is proved to be efficient in predicting the deformation and failure of both photo-cured thermosets and thermoplastics.