Tensile Shear Load Research Articles

An Apparatus for Measuring Combined Shear-Tensile Loading in Fibrous Tissues Ex Vivo.

Soft tissues such as tendon and ligament undergo a combination of shear and tensile loading in vivo due to their boundary conditions at muscle and/or bone. Current experimental protocols are limited to pure tensile loading, biaxial loading, or simple shear, and thus may not fully characterize the mechanics of these tissues under physiological loading scenarios. Our objective was to create an experimental protocol to determine the shear modulus of fibrous tissues at different tensile loads. We assembled a four-actuator experimental system that facilitated shear deformation to be superimposed on a tissue subjected to an axial preload. We measured shear modulus in axially loaded electrospun nanofiber scaffolds with either randomly oriented or aligned fibers. We found that shear modulus in the nanofiber phantoms was shear-strain stiffening and dependent on both the axial load (p < 0.001) and fiber alignment (p < 0.001) of the scaffold. The proposed system can enhance our understanding of microstructure and functional mechanics in soft tissues, while also providing a platform to investigate the behavior of electrospun scaffolds for tissue regeneration. Our experimental protocol for determining loaded shear modulus would be further useful as a method to gauge tissue mechanics under loading conditions that are more representative of physiological loads applied to tendon and ligament.

Initiation and growth of fatigue cracks in sheets with U-shaped notches in the first and mixed modes of fracture

Initiation and growth of fatigue cracks in sheets with U-shaped notches in the first and mixed modes of fracture

On the Micro-Stress Fields in Fibre-Hybrid Polymer Composite Laminae with Periodic Microstructure Under Transverse Tension and Transverse Shear Loading

AbstractThis paper investigates the effect of intra-laminar fibre hybridisation, i.e., primary and secondary fibres within a matrix, on the homogenised properties and micro-stress fields in uni-directional polymer composite laminae. The study is focused on S-glass/epoxy laminae which are hybridised with secondary fibres (e.g., polypropylene). Two-dimensional repeating unit cells (2D RUCs) with periodic microstructures are developed to conduct the micro-mechanical analyses under transverse tensile and transverse shear loading conditions. Uni-directional fibre-hybrid S-glass/epoxy laminae with different secondary fibres are studied by varying (a) the periodic microstructure and (b) the material properties of the constituent fibres to assess the effect of such geometric and material variations on the homogenised elastic lamina properties and intra-lamina micro-stress fields. The results show that intra-laminar fibre hybridisation significantly affects the elastic lamina properties and micro-stress fields. Notably, the presence of the secondary fibres significantly increases or reduces the stress fields in the matrix and at the fibre-matrix interfaces (i.e. normal and shears stress components)–depending on the microstructure and the stiffness of the secondary fibres–which could be explored to manipulate the damage modes and thus energy dissipation mechanisms.

Single-step self-punching lockbolt process for aluminum sheets without pre-hole

For the mechanical joining of aviation-grade aluminum alloys, the study introduces an innovative approach using self-punching lockbolts. This method involves the utilization of a profiled collar and a specially designed bolt to seamlessly join EN AW-2024 T42 aluminum sheets, up to a thickness of 8.0 mm, without the need for pre-holes. In this process, when the aluminum sheets are punched, the collar undergoes slight deformation, effectively functioning as a die. Subsequently, the collar is systematically formed by applying increased force. By fine-tuning the design of the bolt ring groove, it becomes feasible to create a joint with a bolt length that accommodates sheet thickness variations of up to 1.6 mm. To facilitate this development, the joining process was meticulously designed and the auxiliary part was optimized with the aid of numeric simulation tools. The process simulation enabled the identification of deformation mechanisms within the collar, accounting for both geometry and material properties. The important factors influencing collar deformation include collar thickness, shoulder height, and shoulder diameter. Furthermore, experimental investigations were conducted to assess the mechanical properties of the joint and evaluate how material-specific factors influence joint failure behavior. It can be seen that the formation of the mechanical fit is influenced by the ring groove depth and the fitting position. The joints failed under shear tensile load exclusively at the bolt head.

Application of a hierarchical quadrature element method to interface crack analysis in bi-material systems

This paper presents an extension of the hierarchical quadrature element method (HQEM) with p-convergence to evaluating fracture mechanical parameters of bi-material interface cracks. The numerical implementation of HQEM in combination with the virtual crack closure method (VCCM) is comprehensively illustrated, and the formulas for calculating the strain energy release rate (SERR) are rederived. The relationship between components of SERR and the complex stress intensity factors (SIFs) is established. In addition, the effectiveness of an auxiliary parameter related to the dual energy release rates in measuring the accuracy of the present method is examined.The feasibility of applying HQEM to the interface crack problems is demonstrated by investigating the benchmark problem of an infinite bi-material plate with a central interface crack. Two loading cases are considered, including pure tensile loading and mixed tensile-shear loading. The influence of the crack tip element size Δa on the convergence characteristics and computational accuracy of fracture parameters is quantitatively investigated to provide guidance for choosing the most reasonable value of Δa. Numerical results show that even with very coarse meshes, together with a virtual crack extension consisting of only one element, HQEM yields highly accurate results for the total SERR and the complex SIFs, making it suitable for complex, large-scale interface crack problems in dissimilar media.

A low-cost multiscale model with fiber/matrix interface for cryogenic composite storage tanks considering temperature effects based on self-consistent clustering analysis

Matrix (including interface) failure is a typical form of failure in the composite laminates for cryogenic storage tanks causing functionally useless of the structure. In this work, a low-cost multiscale model based on the Self-consistent Clustering Analysis (SCA) method is developed to predict the matrix failure process of the composite storage tanks. First, a reduced order model modeling method with fiber/matrix interfaces is proposed. Then, in conjunction with Progressive Failure Analysis (PFA), a reduced-order model is used to predict matrix failure and interface failure of the composites, mesh sensitivity analyses were carried out, and strength damage envelopes were obtained for unidirectional composites subjected to a combination of transverse stresses and in-plane shear. Compared with the prediction results of the Puck criterion, the errors in predicting damage strength for compressive-shear load and tensile-shear load do not exceed 10% and 30%, respectively. And finally, the thermal-mechanical load analysis of the composite storage tanks is carried out and the effect of homogenous temperature field and heterogenous temperature field on the load-bearing performance of the composite structure is analyzed. The method is proved to have good accuracy and to be very efficient. Its main feature is the ability to rapidly predict the stiffness and strength properties of composite structures under different environmental conditions, in agreement with experimental results, showing the potential to reduce the time and cost required for structural design.

Performance and Interfacial Microstructure of Al/Steel Joints Welded by Resistance Element Welding.

In this study, an upper sheet of an A6061 aluminum alloy and a lower sheet of Q235 steel were welded by resistance element welding with a steel rivet. The temperature field during welding was calculated using ABAQUS numerical simulation software, and the interfacial microstructure was observed. A nugget was formed between the rivet shank and the lower sheet. With increases in welding current and welding time, the tensile shear load of the joint increased first and then decreased slightly. When the welding current was 14 kA and the welding time was 300 ms, the tensile shear load of the joint reached a maximum of 7.93 kN. The smaller the distance from the position to the lower sheet along the interface between the rivet shank and upper sheet, the longer the high-temperature duration and the higher the peak temperature during welding. At the junction of the rivet shank, upper sheet, and lower sheet in the joint, the high-temperature duration was the longest, at about 392 ms, and the peak temperature was the highest, at about 1237 °C. The results show that the smaller the distance from the position to the lower sheet along the interface between the rivet shank and the upper sheet in the joint, the thicker the reaction layer generated there, and that the thickness of the reaction layer was about 2.0 μm at the junction of the rivet shank, upper sheet, and lower sheet in the joint.

Numerical simulation of hybrid CFRP/Al hole-clinched joints at different tensile shear loading rates

In this study, the tensile-shear damage mechanisms and mechanical responses of carbon fiber reinforced plastic (CFRP)/Al clinched joints were investigated at different loading rates. A continuous damage model was developed that incorporated strain rate effects and nonlinear in-plane shear behaviors. The nonlinear in-plane shear behaviors included two stages: the plastic deformation stage and the strengthening by fiber rotation stage. The finite element algorithm was implemented by applying the VUMAT user subroutine in Abaqus to analyze the responses of the CFRP/Al clinched joints with three layups (orthogonal, diagonal, and hybrid). The experimental and simulation results were highly consistent in terms of the joint failure modes, damage evolution predictions and load–displacement responses. The strain rate effects on CFRP damage were determined. Under high-strain-rate conditions, the average reductions in deformation required for the various damage modes were 51.5%, 13.2% and 13.1% for the orthogonal, diagonal and hybrid layup joints, respectively. Furthermore, the corresponding average area reductions in the damage modes were 16.0%, 41.7% and 70.6%, respectively. Then, the strain rate effects on joint mechanical performance were evaluated. The mechanical properties of the orthogonal layup joints did not exhibit strain rate sensitivity, whereas the energy absorption levels decreased by 21.1% and 36.6% for the diagonal and hybrid layup joints, respectively. For the diagonal layup joints, the maximum load increased by 22.4% under dynamic loading.

Effect of tool rotational speed on friction stir spot welds of AZ31B Mg alloy to AISI 304 stainless steel

Abstract AZ31B Mg alloy were welded to AISI 304 stainless steel (which is a very challenging task because of their huge different chemical and physical features) by friction stir spot welding (FSSW) at different tool rotation speeds (700, 1000, and 1300 rpm) while keeping other conditions the same. Welds were evaluated and compared by examining their cross-sectional geometry, XRD pattern, tensile shear strength, fracture way and area. From cross-sections of welds, it was obtained that joining area expanded when speed was enhanced and the weld made through 1300 rpm had the largest one. Therefore, weld fabricated with the highest speed of 1300 rpm displayed the biggest tensile shear load of 3741 N while that manufactured with the lowest speed of 700 rpm possessed the lowest of 2430 N. All welds showed tensile shear type fracture and fracture occurred from the hooking regions where joining took place. From the fracture joint region, the weld of 700 rpm had the smallest joined area, whereas that of 1300 rpm showed the biggest. Higher speed produced a stronger joint, which agreed with a bigger bonding area and broken joint region. Also, joint became more ductile with increasing speed. Some phases were detected in joints.

Measurement of three-dimensional volumetric displacement fields in structural porous adhesive joints, under tensile and tensile-shear load, by means of in-situ X-ray microtomography

Nowadays, structural bonding is increasingly used for its advantages over conventional joining methods such as riveting or welding. Bonding defects (incomplete polymerization, gradient of mechanical properties, and presence of pores, among others.) can significantly impact the mechanical behavior of these assemblies. Among these defects, the presence of pores, detectable by means of X-ray microtomography measurements, could have a significant influence on the mechanical strength of a bonded structure (reduction of the useful section, questioning of the continuity of the joint, and stress concentration, among others). The study of these pores populations by means of microtomographic measurements, as well as their evolution under mechanical stress, can therefore provide valuable information regarding the mechanical behavior. These data can provide information on (i) the mechanical behavior on a microscopic scale, (ii) the identification of mechanisms of damage and failure of the adhesive joint, or (iii) the measurement of volume displacement fields. In this work, a method for calculating volume displacement fields in an adhesive joint is presented, using the detected pores as markers. The robustness, limits, and effects of different parameters (noise, voxelization, among others.) on this algorithm are identified on synthetic data representative of an adhesive joint. Finally, the validation of the method is based on interrupted tests on relatively small bonded specimens (called mini-Scarf) under tensile and tensile-shear loads.

Experimental and numerical analysis of the Microstructure and mechanical properties of unidirectional glass fiber reinforced epoxy composites

This paper proposes a numerical model to predict the pattern and features of the fracture surface and to understand the mechanisms and cause of the failure. Various fiber orientations of 0°, 90°, 0°/90° and ± 45° were utilized in the production of unidirectional glass-fiber-reinforced epoxy composites via the vacuum bagging technique. The mechanical properties of the manufactured composites were evaluated by measuring parameters including tensile strength, compressive strength, flexural strength and interlaminar shear strength. High-resolution scanning electron microscopy was used to examine the mechanisms of fracture in laminates. The mechanical properties of the composite material were found to be considerably improved when a unidirectional 0° fiber orientation was used, as compared to other fiber orientations. This was true for tensile, compressive, flexural and interlaminar shear loading modes. The composite laminates demonstrated several modes of breaking, including fibers pulling away from the matrix, holes in the matrix and river flow lines, depending on the direction of the fibers. The outcomes of the numerical simulation demonstrate a high level of fidelity with experimental findings. This study provides a valuable reference for predicting numerical analysis of the microstructure and mechanical properties.

Achieving excellent properties of resistance spot welded 2GPa-grade press hardened steel and galvanized DP980 steel via double-pulse

Obtaining the excellent resistance spot welding (RSW) properties of press hardened steel is a challenge due to the high strength with 2GPa-grade. In this study, the microstructure, mechanical properties of the RSW weld in 2GPa-grade PHS and galvanized DP980 steel were investigated. During the single pulse welding, the coarse columnar martensite is generated in the fusion zone (FZ). The low peak load is 13.2 kN for tensile-shear (TS) loading and 3.4 kN for cross-tension (CT) loading and the corresponding failure energy is 6.5 J and 16.7 J, respectively. The fracture mode under two loading conditions is partial thickness-partial pullout (PT-PP) mode. To enhance mechanical properties, the suitable double pulse welding was applied. Compared with that of the single pulse weld, double pulse weld has three special zones in FZ: the Re-melted FZ with columnar martensite, the recrystallization zone (RX-zone) with equiaxed martensite and the tempering zone (T-zone) with tempered columnar martensite. The peak load under the TS and CT loading is significantly improved by 39 pct and 44 pct and the failure energy for TS loading is enhanced by 38 pct and 186 pct for CT loading, respectively. The failure mode changes from the PT-PP mode to the pullout failure (PF) mode for CT loading in double pulse welds.

Al heat affected zone-less resistance element welded lap joints of Al alloy and 1 GPa class steel: Transition of microstructure and fracture with heat transfer

In this study, Al joint systems without heat-affected zones (HAZ) were developed on Al/Fe alloy lap joints fabricated by resistance element welding (REW). The robustness of the joints with and without HAZs was quantitatively evaluated to consider another side effect in REW Al/Fe alloy systems. Compared to conventional REW, removing the Al HAZ not only alters the steel properties, but also reduces the work hardening of the Al alloy due to the difference in the distinct heat transfer paths. Furthermore, the presence of Al HAZ significantly influenced the hardness characteristics of the molten steel portion. In the cold wall configuration without Al HAZ, hardness values exceeding those of the hot wall by approximately 100 Hv or more were observed. At a welding current of 10.5 kA, the hot wall configuration demonstrated an approximate 30 % increase in tensile shear load and a 66 % increase in displacement compared to the cold wall configuration without HAZ. In the cold wall conditions, interfacial failure (IF) was not attributed to microstructural disparities but was linked to the formation of an inherent notch root when S20C melted due to the absence of Al HAZ. Contrary to previous reports, the presence of HAZ in Al alloys results the production of tough steel through REW.

Improvement of laser welded TC4/CFRTP joint strength by combination of surface modification of MAO and laser texturing

Laser texturing and MAO (micro-arc oxidation) hybrid process was adopted to enhance the tensile-shear strength of laser welded CFRTP/TC4 joint. Introduction of porous MAO coating enhanced wetting ability of molten peek from CFRTP and increased surface roughness. Porous structure could also provide a mechanical interlocking effect in CFRTP/TC4 interface and improve the resistance to tensile-shear load. Highest tensile-shear force of 1587 N was obtained when 2.3 μm MAO coating was prepared. Based on this, influence of various laser texturing patterns with different MAO coating thickness on the tensile-shear forces was clarified by combination of experiment and reasonable SVR (Support Vector Regression) model. Maximum predicated surface roughness of 3.075 mm was produced at texturing width of 0.327 mm, texturing depth of 100.54 μm and MAO duration of 1.667 min. Furthermore, highest predicated tensile-shear force of 2995.1 N was achieved at texturing width of 0.331 mm, texturing of depth of 100.6 μm and MAO duration time of 1.718 min.

Evolution of bonding mechanism and fracture mechanism of Ti alloy-steel joint by dual-beam laser welding using Mg-RE (RE=Gd, Y) filler

In this paper, a novel coaxial continuous-pulsed dual-beam laser was proposed to join TC4 titanium alloy with QP980 high-strength steel, and magnesium alloy containing rare-earth elements (Mg-RE) was creatively as filler. The weld appearance, microstructure and mechanical properties of joints obtained by single-beam and dual-beam laser welding were compared and analyzed. And the evolution of bonding mechanism and the fracture mechanism with laser beam energy density was analyzed. The results showed that the appearance and mechanical strength of the joint obtained by dual-beam laser were better than that by single-beam laser. And the maximum tensile shear load of TC4/QP980 lap joint welded by dual-beam laser reached 303 N/mm, which was 124 % of that of single-beam laser welding. The bonding of Mg-RE with QP980 affected by temperature of laser welding and mainly depended on Gd and Y. They just diffused to QP980 under low power and reacted with Fe under high power. And the inter-diffusion of Zr of Mg-RE with Ti of TC4 produced to the bonding of Mg-RE with TC4. The roles of continuous laser and pulsed laser in dual-beam laser welding were revealed in this paper and it showed a great application potential of coaxial dual-beam laser welding technology in dissimilar metal joining.

Damage behavior and mechanical property investigation of CFRP/CFRP washer-bushing riveted joints

Carbon fiber reinforced composites (CFRP) are prone to occur riveting damage. Therefore, the damage behaviors and mechanical properties of CFRP/CFRP washer-bushing riveted joints were investigated experimentally in this paper. Results showed that due to the uneven expansion of rivet shank and local pressure caused by upsetting head, CFRP/CFRP riveted joints occurred multiple damage modes by using net riveting method and bushing method. The damage was mainly located in the layer around the CFRP hole near the upsetting head. However, washer-bushing riveting method effectively limited the uneven expansion and the local pressure of upsetting head, and no obvious damage was observed. Load-displacement curves of direct riveted joints and washer-bushing riveted joints exhibited obvious linear stage, progressive damage stage and final failure stage in both tensile shear and pull-off tests. However, the bushing reduced the effective fastening area of upsetting head, and load-displacement curves of bushing riveted joints only included linear and failure stages. Besides, the tensile shear and pull-off peak load were also the lowest. Tensile failure modes of both net riveted joints and washer-bushing riveted joints were dominated by the coupling failure mode of shear failure and rivet pull-off. The CFRP connecting hole was observed with obvious shear damage and extrusion deformation area. Besides, pull-off failure modes were laminate fracture and ply delamination, and also accompanied by laminate bending deformation. In contrast, bushing riveted joints failed by rivet pull-off in both tensile shear and pull-off tests.

Multilayer bonding of A1N30H foils to A1050 plates using cold spot forge welding

The cold spot forge-welding method, recently developed to achieve high-productivity and high-strength dissimilar material joining, was applied to multiple solid-phase joining of aluminum (Al) foils simulating tab-lead electrodes. Fifty Al foils of 12-μm thickness were sandwiched between 0.5 and 0.8 mm A1050 Al alloy plates and pressurized with 6-mm diameter punch for 1 s. The effect of bonding temperature (330–420 °C) and the reduction ratio (R, 1.4–3) on the tensile shear load of the joint was investigated. A lower R value at a higher bonding temperature resulted in base metal fracture (i.e., plug fracture) of the Al alloy plate. The maximum load reached 410 N using a reduction ratio of higher than 2.1 and bonding temperature of 420 °C. The processed foils were properly stretched in the plane without breakage, and a total of 51 sound layered bonded interfaces were formed. The results also confirmed that the oxide film became more rarefied with increasing R. These results are expected to be applicable to high-throughput, high-reliability bonding of secondary battery electrodes.

Characterization of friction stir-based linear continuous joining of aluminium alloy to structural polymer

Dissimilar continuous joining of lightweight metal alloys to structural polymer is a major manufacturing challenge, demanding feasible and reliable solutions. Through-slot extrusion joining (TSEJ) is a friction stir-based processing technique investigated in the manufacturing of continuous linear joints between aluminium alloy AA5754 overlapping structural polymer polyether ether ketone (PEEK). An intermediate rigid and thin titanium extrusion die protects the polymer locally from thermal degradation and promotes the formation of a continuous double hook-like feature of extruded aluminium into the polymer component along the joint path. The structure of the joint provides macro-mechanical interlocking between the joined components. A set of four tools, and other key process parameters, were investigated for process stability, tensile-shear strength, and microstructure. The best TSEJ condition is chosen for microstructural analysis via optical microscopy and scanning electron microscopy. Three distinct failure modes were identified. The best condition provided an average tensile-shear load of 110 kN/m. The tool position with bias toward the flow side of the extrusion slot shows to improve the strength of joints. The microstructural analysis along the interface of AA5754 to PEEK exhibits micro-mechanical interlocking, intercalated layers of these materials and adhesion as joining mechanisms.

Tensile-shear properties of steel-Al adhesively bonded dissimilar joints and the effect of Al plate thickness

Lap shear dissimilar joints between aluminium (Al) alloy, A6061-T6, and stainless steel, type 304, were fabricated by adhesive bonding. Three Al plates with different thicknesses were used to investigate the effect of the Al plate thickness on the tensile-shear properties, namely the effect of bending stiffness of Al plates. The maximum tensile-shear loads increased with increasing Al plate thicknesses. The fracture through the adhesive layer (cohesive fracture) occurred when the Al plate was the thickest, while the interface fracture between Al plate and adhesive layer appeared on the fracture surface with decreasing Al plate thickness. Fatigue strengths also increased with increasing Al plate thickness. When the fatigue strengths were normalized by the tensile strengths, the effect of the plate thickness became negligible. FEM analyses revealed that the stress concentration at the edge of adhesive on Al side decreased with increasing Al plate thickness, which could be related to the dependence of tensile and fatigue properties on the Al plate thickness.

Experimental Study on Performance of Bolted Joints Under Tensile–Shear Loads

Experimental Study on Performance of Bolted Joints Under Tensile–Shear Loads