Tensile Shear Load Research Articles

Microstructure and mechanical properties of resistance-spot-welded joints for A5052 aluminum alloy and DP 600 steel

The microstructure and mechanical properties of resistance-spot-welded A5052 aluminum alloy and DP 600 dual-phase steel joint were studied. The fusion zone (FZ) and heat-affected zone (HAZ) of DP 600 exhibited lath martensite and ferrite-martensite structures, respectively. The microstructure of FZ and HAZ in the A5052 side was composed of cellular crystals and the boundary region of FZ exhibited a columnar crystal morphology. A Fe2Al5 intermetallic compound (IMC) layer with 3.3μm thickness was found adjacent to the DP 600 side, whereas a needle-shaped Fe4Al13 IMC layer with length of 0.67μm to 15.8μm was found adjacent to the aluminum alloy side. The maximum tensile shear load of the A5052/DP 600 joint was 5.5KN, with a corresponding molten nugget diameter of 6.3mm. The fracture morphology of the optimized A5052/DP 600 joint was mainly an elongated dimple fracture accompanied by cleavage fracture.

Microstructures and mechanical properties of resistance spot welded joints of 16Mn steel and 6063-T6 aluminum alloy with different electrodes

The dissimilar resistance spot welding of 16Mn high strength steel and 6063-T6 aluminum alloy was studied by using different welding electrodes and welding parameters. The aluminum alloy nuggets consist of cellular crystals, cellular dendrites and equiaxed dendrites with tangled dislocations and fine Mg2Si particles. There exist intermetallic compound layers including Fe2Al5 layer at steel side and Fe4Al13 layer at aluminum side in the interface zone, and their evolution process has been summarized. The excessive Fe-Al intermetallic compounds deteriorated the steel-aluminum joint strength. The welding electrode morphology and welding parameters had great effects on the steel-aluminum joints. When F-type electrodes were used, the tensile shear load and indentation ratio of the joint are 2534N and 28.0%, respectively under the condition of optimized welding parameters. When optimized electrodes were used, the tensile shear load of the joint reached 3623N and the indentation ratio decreased to 18%, which is related to improving welding temperature distribution. It is more favorable to use the optimized electrodes for increasing the steel-aluminum joint strength and improving its appearance quality.

Resistance Spot Welds of 304L Austenitic Stainless Steel, Part 3:1 & 1, 1 & 2 and 2 & 2 mm Thickness of Weld Joints

Part 1 of this research introduces the spot weld growth on 304L stainless steel, mainly by explaining information: such as the specimen size, static resistance, welding lobe, welding schedule, simulation, tensile shear load, failure mode, and elongation. In part 2, the analysis explains the dynamic resistance, force profile, electrically generated forging force, macro and micro structural orientation and also the hardness distribution. In part 3, the investigation reveals similar and dissimilar thicknesses: pertaining to macrograph orientation, electrode indentation and the weld growth. Three types of different thicknesses are investigated for the macrograph development and subsequently found the symmetrical weld bead geometry despite thicknesses. Electric current increment is mainly analysed in this experiments as it increases the weld size significantly. Strength tests show that the weld geometries have been widened in proportion to the escalation of electric currents. The astonishing factor is that the bead thickness reduction due to electrode indentation does not affect the tensile strengths at all.

Investigation of resistance spot welds between DP450 steel and aluminum alloys

Abstract In this study, the resistance spot weldability of DP450 steel and aluminum alloys (AA1050, AA6061 and AA7075) was investigated and the interfacial characteristics of fracture zones was examined via microanalysis, scanning electron microscopy and energy dispersive spectroscopy (EDX). In addition, tensile shear load tests and hardness tests were performed to determine the mechanical properties and fracture behavior of welded joints. These results suggest that the tensile shear strength of the DP450/AA1050 and DP450/AA7075 joints was not affected by the reaction layer formed at the welding interface. This indicates that the spot weldability of DP450/AA6061 is better than DP450/AA1050 and DP450/AA7075 Al alloys.

Microstructural and mechanical performance of ultrasonic spot welded Al–Cu joints for various surface conditions

The ultrasonic metal welding (USMW) offers a potential solution to join highly thermal conductivity dissimilar materials like aluminium and copper. In this work, the effects of different welding parameters and surface conditions like lubricated, normal, electrolytic polished and emery polished are investigated to obtain the maximum mechanical strengths of the weld joints. The results show that tensile shear and T-peel failure loads increased with weld time and reached the highest value of 1550.48N and 370.46N, respectively. It is also observed that these joint strengths decreased with the increase of surface roughness because of the disappearance of relative motion between the sheets. Thus, the temperature that is obtained from emery paper condition is the lowest among all the four surface conditions. Meanwhile, the maximum interface temperature obtained when the ethanol droplet is added to the faying surface. This is to say, a substantial plastic deformation is observed at the welded region due to this high temperature of 375°C and thus, it facilitates the rupture of the oxide film. From the microstructural analysis, a dimple pattern is noticed in the welding zone, indicating an expansion of weld area and grain refinement has been taken place due to the adhesion of ethanol. Similarly, the microhardness study also revealed that there is no formation of the large heat affected zone in USMW. An average microhardness of HV 88.45 is observed for the joint which is quite high than other solid state welding processes.

Fatigue behavior and life prediction of self-piercing riveted joint

The fatigue behavior of self-piercing riveted joints of aluminum alloy AA6111-T4 and steel HSLA340 sheets has been experimentally and numerically investigated in present paper. Fatigue results reveal that the mating sheet stiffness and load ratio have significant impact on the fatigue strength, and the dominant failure mode under tensile–shear loading is eyebrow crack with an approximately semi-elliptical crack front. New stress intensity factor equations are derived for a semi-elliptical surface crack in a finite plate near a rigid cylindrical inclusion with axial shear force and bending moment, including the ratio of crack depth to crack length ranged from 0.2 to 1 and the ratio of crack depth to sheet thickness ranged from 0.2 to 0.8. A new structural load fatigue crack growth model is proposed, and predictions of fatigue lives and final crack aspect ratios show good agreement with experimental results.

Fatigue strength and fatigue fracture mechanism of three-sheet spot weld-bonded joints under tensile–shear loading

This paper deals with fatigue behavior of three-sheet spot weld-bonded (SWB) joints to investigate the influence of adhesive bonding on fatigue strength and fracture mechanism. From the results of tensile–shear fatigue tests, the fatigue strength of the SWB joint was higher than that of the spot welded (SW) joint. For fatigue behavior in the SWB joint, debonding between a steel sheet and adhesive propagated from an edge of bonded area to a nugget edge, and a fatigue crack initiated at the nugget edge. It was concluded that the delayed fatigue crack initiation at the nugget edge in the SWB joint resulted in the fatigue strength improvement of SW joint.

Effects of multi-pulse tempering on resistance spot welding of DP590 steel

Multi-pulse tempering (MPT) on the resistance spot welding (RSW) is a considerable method to improve the quality of spot weld joints. For its uncertain tempering temperature and large temperature fluctuation, some stable sequential coupling finite element (FE) models for RSW and MPT of DP590 dual phase steel are developed to control the tempering temperature and further determine the experimental parameters. The nugget shape and size of simulation are verified by experimental observation, and the effects of MPT on microstructure, microhardness, and mechanical property during tensile-shear loading condition are experimentally investigated. The results show that MPT and its tempering temperature have no effect on the tensile-shear failure mode and have slight impact on nugget size and tensile-shear peak load. Besides, MPT leads to lower nugget hardness and better mechanical properties of spot weld joints than that of ordinary RSW due to the formation of a tempered martensite, and the higher tempering temperature expands these effects of MPT. However, the extent of the impact by MPT temperature on microstructure and mechanical property of spot weld joints is inferior to that of the impact by the MPT process itself.

Analysis on Adhesively-Bonded Joints of FRP-steel Composite Bridge under Combined Loading: Arcan Test Study and Numerical Modeling.

The research presented in this paper is an experimental study and numerical analysis on mechanical behavior of the adhesively-bonded joint between FRP sandwich bridge deck and steel girder. Generally, there are three typical stress states in the adhesively-bonded joint: shear stress, tensile stress, and combination of both. To realize these stress states in the adhesively-bonded joint during tests, a specific loading device is developed with the capacity of providing six different loading angles, which are 0°(pure tension), 18°, 36°, 54°, 72° and 90°(pure shear). Failure modes of adhesively-bonded joints are investigated. It indicates that, for the pure shear loading, the failure mode is the cohesive failure (near the interface between the adhesive layer and the steel support) in the adhesive layer. For the pure tensile and combined loading conditions, the failure mode is the combination of fiber breaking, FRP delamination and interfacial adhesion failure between the FRP sandwich deck and the adhesive layer. The load-bearing capacities of adhesive joints under combined loading are much lower than those of the pure tensile and pure shear loading conditions. According to the test results of six angle loading conditions, a tensile/shear failure criterion of the adhesively-bonded joint is obtained. By using Finite Element (FE) modeling method, linear elastic simulations are performed to characterize the stress distribution throughout the adhesively-bonded joint.

Microstructure and Fatigue Properties of Ultrasonic Spot Welded Joints of Aluminum 5754 Alloy

The purpose of this investigation was to evaluate the microstructural change, lap shear tensile load, and fatigue resistance of ultrasonic spot welded joints of aluminum 5754 alloy for automotive applications. A unique “necklace”-type structure with very fine equiaxed grains was observed to form along the weld line due to the mechanical interlocking coupled with the occurrence of dynamic recrystallization. The maximum lap shear tensile strength of 85 MPa and the fatigue limit of about 0.5 kN (at 1 × 107 cycles) were achieved. The tensile fracture occurred at the Al/Al interface in the case of lower energy inputs, and at the edge of nugget zone in the case of higher energy inputs. The maximum cyclic stress for the transition of fatigue fracture mode from the transverse through-thickness crack growth to the interfacial failure increased with increasing energy input. Fatigue crack propagation was mainly characterized by the formation of fatigue striations, which usually appeared perpendicular to the fatigue crack propagation.

Resistance Spot Welds of 3041 Austenitic Stainless Steel, Part 2:Signals Measurement, Dynamic Resistance, Electrically Generated Forging Force, Metallurgy and Hardness Distribution Analysis

Part 1 of this research introduces the spot welds growth on 304L stainless steel; primarily supported by information such as the chemical property, specimen size, calculated-static resistance, welding lobe, welding schedule, simulation, tensile shear load, indentation, failure mode, and also the elongation during tensile test. In part 2, the analysis is furthered to understand the dynamic resistances, force profiles, electrically generated forging forces, macro and micro structural orientation and also the hardness distribution. Heat development during the welding process is proportionally influenced by the dynamic resistances and therefore several detailed analytical approaches have been included to understand the process variables certainly. Literally the dynamic resistances are proportionally related for the welding current and welding time changes but reversely behaved for the electrode force changes within the welding lobe limits. These resistive changes became the ischolar_main cause of weld growth pertaining to heat variations. So the computations have been carried out from the perspective of welding current against the terminal voltage. On the other end, the force profiles are relatively measured to observe the electrode force variation with respect to the welding current changes. With the changes of process variables, the corresponding weld growth is analysed in terms of dynamic resistances in this experiment. Eventually the micro structural changes show the enrichment of coarsened grains but transformed in phases as results; which lead to slight increment of hardness at the welded areas as Rockwell hardness proves these increments as well.

Friction stir spot welding of 2024-T3 aluminum alloy with SiC nanoparticles

In this study, the Friction stir spot welding (FSSW) of 2024-T3 aluminum alloy with 1.6 mm thickness was investigated. The effects of the silicon carbide (SiC) nanoparticles on the metallurgical and mechanical properties were discussed. The effects of particles on tensionshear and wear tests were also investigated. The process was conducted at a constant rotational speed of 1000 rpm. Results showed that adding SiC nanoparticles to the weld during FSSW had a major effect on the mechanical properties. In fact, the addition of nanoparticles as barriers prevented grain growth in the Stir zone (SZ). The data obtained in the tensile-shear and wear tests showed that tensile-shear load and wear resistance increased with the addition of SiC nanoparticles, which was attributed to the fine grain size produced in the SZ.

GS0307 引張せん断負荷を受ける異種材料波型重ね合わせ接着継手の強度特性と有限要素解析

GS0307 引張せん断負荷を受ける異種材料波型重ね合わせ接着継手の強度特性と有限要素解析

Microstructure and mechanical properties evolution of friction stir spot welded high-Mn twinning-induced plasticity steel

Friction stir spot welding of high-Mn twinning-induced plasticity steel was studied. Welds were made at different tool rotation speeds and constant plunge rate and dwell time. The microstructure evolution was examined by optical microscopy, scanning electron microscopy and electron backscattered diffraction technique. In addition, the microhardness distribution and tensile-shear load bearing capacity were measured. The friction stir spot welding process successfully produced high integrity completely defect-free joints at all the proposed welding parameters. However, the complex plastic deformation and high thermal cycle experienced had a significant effect on the weld region, which consisted of three distinct zones. The flow transition zone, stir zone and torsion zone were all characterized by a recrystallized grain structure. The heat affected zone was characterized by a coarse grain structure as a result of grain growth caused by the high thermal cycles experienced. The hardness was significantly affected by friction stir spot welding, resulting in a softened region in the joint area. The softening increased as the rotation rate increased. The maximum peak tensile shear load of 13kN was obtained at 750rpm, and a considerable amount of extension was obtained in all the joints with a maximum of 4mm at 500rpm.

The effects of corn zein protein coupling agent on mechanical properties of flax fiber reinforced composites

The aim of this study was to investigate the effect of zein protein treatments on the mechanical performance of flax fiber/thermoset resin composites. Flax fibers treated with corn zein protein to improve compatibility with epoxy and vinyl ester resin were processed into composites and tested under tensile, flexural, and short beam shear loadings. Pure zein treatments were tested at 1, 2.5, and 5% concentrations. Zein was also introduced to flax fibers through treatments with Corn Gluten Meal (CGM) and Dried Distiller Grains with Solubles (DDGS). The addition of zein protein increased the strengths of the composite for all three tests. Results demonstrated that the 2.5% pure zein treatment produced the largest gains with an increase of tensile strength by 8%, flexural strength by 17%, and short beam shear strength by 30% compared to untreated samples. To further investigate the effectiveness of zein treatments, Fourier Transform Infrared Spectroscopy (FTIR), chemical analysis, and Scanning Electron Microscopy (SEM) techniques were used. Results showed promise of using zein protein as an all-natural, environmentally friendly, coupling agent for flax fiber composites.

Pinless Friction Stir Spot Welding of Mg‒3Al‒1Zn Alloy with Zn Interlayer

With the addition of a thin Zn interlayer, 2.4 mm thick Mg‒3Al‒1Zn alloy sheets were friction stir spot welded (FSSW) using a pinless tool with flat, convex and concave shoulder shapes. The results showed that an alloying reaction took place between the Mg substrate and Zn interlayer during FSSW, forming a discontinuous intermetallics layer composed of dispersive (α-Mg + MgZn) eutectic structure underneath the shoulder and a Mg‒Zn intermetallics bonding zone at the outside of the joints. This alloying reaction increased the bonded area and eliminated the hook defects, thereby producing sound FSSW joints with a shallow keyhole without hook defects. The increase of plunge depth was beneficial to the Mg‒Zn diffusion, thereby increasing the tensile-shear load of the joints. However, excessive plunge depths resulted in a decrease of the effective sheet thickness, reducing the strength of the joints. At a small plunge depth, the convex and concave shoulders were more beneficial to the interface reaction than the flat shoulder. The maximum joint load of 6.6 kN was achieved by using the concave shoulder at a plunge depth of 1.0 mm. A post-welding heat treatment promoted the dissolution of the discontinuous reaction layer in the joints; however, it led to the occurrence of void defects, influencing the bonding strength.

Elastin governs the mechanical response of medial collateral ligament under shear and transverse tensile loading

Elastin is a highly extensible structural protein network that provides near-elastic resistance to deformation in biological tissues. In ligament, elastin is localized between and along the collagen fibers and fascicles. When ligament is stretched along the primary collagen axis, elastin supports a relatively high percentage of load. We hypothesized that elastin may also provide significant load support under elongation transverse to the primary collagen axis and shear along the collagen axis. Quasi-static transverse tensile and shear material tests were performed to quantify the mechanical contributions of elastin during deformation of porcine medial collateral ligament. Dose response studies were conducted to determine the level of elastase enzymatic degradation required to produce a maximal change in the mechanical response. Maximal changes in peak stress occurred after 3h of treatment with 2U/ml porcine pancreatic elastase. Elastin degradation resulted in a 60–70% reduction in peak stress and a 2–3× reduction in modulus for both test protocols. These results demonstrate that elastin provides significant resistance to elongation transverse to the collagen axis and shear along the collagen axis while only constituting 4% of the tissue dry weight. The magnitudes of the elastin contribution to peak transverse and shear stress were approximately 0.03MPa, as compared to 2MPa for axial tensile tests, suggesting that elastin provides a highly anisotropic contribution to the mechanical response of ligament and is the dominant structural protein resisting transverse and shear deformation of the tissue.

The quantitative investigation of mechanical properties and characterization of fractured position for friction stir lap welded A6111/A5023

Abstract The effects of plunge depth (PD) revolutionary pitch (RP) and materials arrangement on deformation and softening material at the fractured position of a friction stir welded AA6111 to AA5023 lap joint were investigated. As a result, the main factor determining tensile shear load and fracture was different with the location of soft material. When the soft material was located on top, the softening material and the deformed surface height occurred by friction heat generation of the rotating shoulder. The main factor was the deformed surface height rather than the softening material, and the deformed surface height was decreased with increasing RP. On the other hand, when the soft material was located at the bottom, the movement of the un-bonded line and hooking occurred due to the vertical flow of the rotating probe. The crucial factor was the position of the un-bonded line rather than the height of the hook. The un-bonded line occurred along the interface between two materials affected by the lowest strength, which were deformed toward the hard material affected by a higher joint strength.

Mechanical performance of AA6181 refill friction spot welds under Lap shear tensile loading

AbstractThis study investigates the fracture behaviour of refill friction spot welding welds under shear tensile loading. Overlap joints of 6181‐T4 aluminium were produced in 1.7‐mm sheets by varying the rotational speed from 1900 to 2900 rpm and the welding time from 2 to 3.4 s while keeping the plunge depth constant at 1.75 mm. After shear tensile tests, the samples were analysed using optical microscopy and scanning electron microscopy. The strength of the weld and its ductile/brittle behaviour are associated with the nucleation, growth and propagation of two types of cracks: circumferential cracks and annular cracks. Welds produced with longer welding times (≥3 s) and slower rotational speeds (1900 rpm) had higher strengths, low scattering and high energy absorption prior to failure, while welds produced with short welding times (2 to 2.4 s) resulted in poor joints, especially when they also used high rotational speeds.

RETRACTED ARTICLE: An investigation on mechanical and metallurgical properties of 2024-T3 aluminum alloy spot friction welds

In this study, the spot friction welding of 2024-T3 aluminum alloy with 1.6 mm in thickness has been investigated. The effects of the tool rotational speed (630, 1000, and 1600 rpm), shoulder penetration depth (0.3 and 0.7 mm), and pin geometry (cylindrical and triangular shape) have been discussed on the metallurgical and mechanical properties. Results indicated that the pin geometry has a considerable effect on the shape of the stir zone. The results of tensile shear tests showed that the tensile shear load increased with increasing rotational speed in the shoulder penetration depth of 0.3 mm, while high shoulder penetration depth had a bilateral effect on the tensile shear load. In addition, the results showed that the tensile shear load of welds made with the triangular pin at a low rotational speed, and a low shoulder penetration depth was more than of welds made with the cylindrical one, which was attributed to a finer grain size generated in the stir zone. Observation of the failed specimens indicated two types of failure modes under tensile shear loading conditions including the fractures that occurred in the vicinity of keyhole (shear fracture) and the fractures that occurred in shoulder indentation (tensile shear-mixed fracture mode). The microhardness tests with both pins showed that the minimum hardness was measured in the heat-affected zone.