scholarly journals An approach to improving the mechanical properties of friction stir spot welded joints on the basis of hook formation mechanism

2020 ◽  
Vol 01 ◽  
Author(s):  
Shuaishuai Du ◽  
Huijie Liu ◽  
Yanying Hu ◽  
Tengfei Yang
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Formation Mechanism ◽  
Material Flow ◽  
Low Pressure ◽  
Tensile Shear Strength ◽  
Tensile Shear ◽  
Friction Stir ◽  
Pressure Zone ◽  
Hook Geometry

Background: Partial metallurgical bond (namely 'hook') is formed between the overlapped metal sheets during friction stir spot welding (FSSW). The geometry of hook is found to significantly affect the mechanical performance of FSSWed joints, while that how to adjust hook geometry to a better state remains to be studied. Methods: The conventional FSSW joints under different plunge depths and dwelling time were obtained. The cross-sectional morphology of each spot weld was investigated to clarify the material flow behavior and deduce the formation mechanism of hook. The tensile shear strength and fracture features were examined to reveal the effect of hook geometry on the mechanical properties. Results: The weld geometry affects the tensile shear strength of FSSWed joints by determining their fracture modes. The formation mechanism of hook is deduced by a material flow model. In the tool-plunging stage, the faying interface is broken by upward-flowing materials, hook is therefore initiated and driven up gradually. During the tool-dwelling stage, hook continues to migrate to the low-pressure zone, surrounding the stir zone. Conclusion: The uncertainty of crack-propagating endpoint along hook makes it difficult to ensure the mechanical properties of welds. If the hook endpoint has not yet reached the low-pressure zone at the end of welding process, welds with ideal hook geometry can be obtained. Target friction stir spot welds were produced by the use of a tool possessing smaller pin diameter.

Effect of Tool Geometry on Strength of Friction Stir Spot Welded Aluminum Alloys

2012 ◽  
Vol 579 ◽  
pp. 109-117 ◽  
Author(s):  
Yuan Ching Lin ◽  
Ju Jen Liu ◽  
Ben Yuan Lin
Keyword(s):  
Tensile Strength ◽  
Shear Strength ◽  
Spot Welding ◽  
Tool Geometry ◽  
Al Alloy ◽  
Tensile Shear Strength ◽  
Tensile Shear ◽  
Friction Stir ◽  
Hook Geometry ◽  
Spot Welded

The effects of tool geometry on the microstructure and tensile shear strength of friction stir spot-welded A6061-T6 Al alloy sheets were investigated in the present study. Friction stir spot welding (FSSW) was carried out at a tool speed of 2500 rpm, plunging rate of 1 mm/s, and dwell time of 3 s. Four types of tools with the same shoulder shape and size, but different pin profiles (threaded cylindrical, smooth cylindrical, threaded triangular, and smooth triangular) were used to carry out FSSW. The mechanical and metallurgical properties of the FSSW specimens were characterized to evaluate the performance of the different tools. Experimental results show that the pin profile significantly alters the hook geometry, which in turn affects the tensile shear strength of the friction stir spot welds. The welds made using the conventional thread cylindrical tool have the largest elongation and yield the highest tensile strength (4.78 kN). The welds made using the smooth cylindrical tool have the lowest tensile strength. The welds made using the threaded triangular and smooth triangular tools both have a tensile-shear load of about 4 KN; however, the welds made using the threaded triangular tool have a better elongation than those made using the smooth triangular tool.

Tensile shear strength of UF- and MUF-bonded veneer related to data of adhesives and cell walls measured by nanoindentation

Holzforschung ◽  
2010 ◽  
Vol 64 (3) ◽  
Author(s):  
Frank Stöckel ◽  
Johannes Konnerth ◽  
Wolfgang Kantner ◽  
Johann Moser ◽  
Wolfgang Gindl
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Bond Strength ◽  
Cell Walls ◽  
Urea Formaldehyde ◽  
Lap Joints ◽  
Tensile Shear Strength ◽  
Tensile Shear ◽  
Interphase Cell ◽  
Cure Time

Abstract The tensile shear strength of veneer lap joints was characterised. The joints were produced with an Automated Bonding Evaluation System (ABES) using urea-formaldehyde (UF) as well as melamine-urea-formaldehyde (MUF) adhesive formulated for particleboard production. At a fixed heating temperature of 110°C, a systematic increase in bond strength was observed for both adhesives with increasing cure time. The absolute bond strength was significantly higher for MUF compared to UF. Nanoindentation experiments with the same specimens used for ABES revealed a very hard, stiff and brittle character of the UF resin, whereas the MUF proved significantly less hard and stiff, and less brit-tle. Wood cell walls in contact with adhesive, i.e., where adhesive penetration into the cell wall was assumed, showed significantly altered mechanical properties. Such cell walls were harder, stiffer and more brittle than unaffected reference cell walls. These effects were slightly more pronounced for UF than for MUF. Comparing UF and MUF, the micro-mechanical properties of cured adhesive and interphase cell walls confirm earlier observations that tougher adhesives can lead to higher macroscopic bond strength. In strong contrast to that, no obvious correlation was found between micromechanical properties and the strong cure time dependence of macroscopic bond strength.

scholarly journals Effect of Microstructure and Texture on Mechanical Properties of Resistance Spot Welded High Strength Steel 22MnB5 and 5A06 Aluminium Alloy

Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 685
Author(s):  
Xiaoqing Jiang ◽  
Shujun Chen ◽  
Jinlong Gong ◽  
Zhenyang Lu
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Aluminium Alloy ◽  
High Strength Steel ◽  
High Strength ◽  
Welding Parameters ◽  
Tensile Shear Strength ◽  
Tensile Shear ◽  
Resistance Spot ◽  
Effect Of Microstructure

The present study aims to investigate the effect of microstructure and texture on mechanical properties of resistance spot welding of high strength steel 22MnB5 and 5A06 aluminium alloy as a function of welding parameters. The pseudo-nugget zones (NZs) at the steel side have undergone full recrystallisation with a fine-grained ferrite structure containing a small amount of retained austenite and a high hardness of approximately 500 HV, which is a 35% increase in hardness compared to the base material (BM) with fine lath martensitic structure. The NZs at the Al side contain both a recrystallisation texture and shear texture. Higher tensile shear strength with increasing weld time could be linked to the random texture at the Al side. The highest tensile shear strength was achieved at an intermetallic layer thickness of 4 mm.

Effects of process time and thread on tensile shear strength of Al alloy lap joint produced by friction stir spot welding

2010 ◽  
Vol 24 (3) ◽  
pp. 169-175 ◽  
Author(s):  
Mitsuo Fujimoto ◽  
Daisuke Watanabe ◽  
Natsumi Abe ◽  
Sato S. Yutaka ◽  
Hiroyuki Kokawa
Keyword(s):  
Shear Strength ◽  
Spot Welding ◽  
Friction Stir Spot Welding ◽  
Process Time ◽  
Al Alloy ◽  
Tensile Shear Strength ◽  
Lap Joint ◽  
Tensile Shear ◽  
Friction Stir

The investigation into vibration effect on microstructure and mechanical characteristics of friction stir spot vibration welded aluminum: Simulation and experiment

2020 ◽  
Vol 234 (9) ◽  
pp. 1809-1822 ◽  
Author(s):  
Behrouz Bagheri ◽  
Mahmoud Abbasi ◽  
Reza Hamzeloo
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Shear Strength ◽  
Finite Element Simulation ◽  
Stir Zone ◽  
Tensile Shear Strength ◽  
Tensile Shear ◽  
Friction Stir ◽  
Element Simulation ◽  
Workpiece Vibration

In this study, an innovative technique is employed to modify the microstructure and increase the mechanical characteristics of the Al5083 joint made by friction stir spot welding (FSSW). In this technique entitled FSSVW (friction stir spot vibration welding), the workpiece is vibrated during FSSW. Noted processes were modeled and finite element simulation results were also analyzed. The results showed that workpiece vibration during FSSW led to grain refinement, larger weld region, and improvement of the mechanical properties, namely tensile shear strength and hardness, of the joint. Stir zone grain size decreased by about 25% and tensile shear strength value increased by about 20% by applying workpiece vibration during FSSW. The results also indicated that the tensile shear strength and hardness enhanced, as vibration frequency increased. It was concluded that the presence of vibration increased the material deformation in the stir zone and led to enhanced deformation of the material. This intensified the dynamic recrystallization and resulted in grain refinement. It was also found that tensile residual stresses developed in the stir zone of FSS and FSSV welded specimens and tensile residual stress values for FSSV welded specimens were higher than those for FSS welded specimens for about 10%. It was concluded that the effect of grain size on hardness is higher than the effect of residual stress. Higher ductility is predicted for FSSV welded specimen with higher vibration frequency and also for specimen welded with less dwell time; finite element simulation was also applied to analyze the effects of workpiece vibration during FSSW on strain distribution as well as hardness and residual stress distribution within the joint during FSSW and FSSVW processes. Finite element simulation results had good compatibility with experimental results. It was concluded that the strain values and flow velocity relating to the FSSVW process are higher than those relating to the FSSW process.

Friction Stir Lap Joining of Blanks under Different Conditions

2015 ◽  
Vol 651-653 ◽  
pp. 1433-1438 ◽  
Author(s):  
Carlo Bruni ◽  
Alessio D'Orazio ◽  
Mohamad El Mehtedi
Keyword(s):  
Numerical Simulation ◽  
Shear Strength ◽  
Numerical Simulations ◽  
Welded Joints ◽  
Rotational Velocity ◽  
Tool Geometry ◽  
Tensile Shear Strength ◽  
Trial And Error ◽  
Tensile Shear ◽  
Friction Stir

The present investigation aims at studying the effect of the tool geometry and of rotational velocity of the tool, at different welding velocities, on the tensile shear strength of the friction stir welded joints realised with blanks of different thicknesses. The proposed trial and error methodology was based on experiments, numerical simulations and microstructure observations.It was observed that, at the lowest rotational velocity, the slender tool determines tensile shear strength values lower than those obtained with the thick tool in particular at the highest welding velocity investigated. The numerical simulation evidenced a wider stirred zone for the thick tool when compared with that realised with the slender tool at the lowest rotational velocity. Microstructure observations evidenced that the increase in the welding velocity determines reduced stirred zones and an homogenisation of material particularly relevant for the slender tool.

Effects of Process Parameters on Tensile Shear Strength of Friction Stir Spot Welded Aluminium Alloy (EN AW 5005)

2014 ◽  
Vol 59 (1) ◽  
pp. 221-224 ◽  
Author(s):  
M.K. Kulekci
Keyword(s):  
Shear Strength ◽  
Aluminium Alloy ◽  
Process Parameters ◽  
Dwell Time ◽  
Tensile Shear Strength ◽  
Tensile Shear ◽  
Friction Stir ◽  
Tool Pin ◽  
Tool Rotation ◽  
Spot Welded

Abstract Aluminium and its alloys have been used in automotive technology since the first model of the car. The need for aluminium material is getting increased for weight reduction, improved fuel economy and vehicle performance. The amount of the aluminium used in a car is mainly related with joining processes of aluminium alloy. This can be achieved by developing the welding techniques for aluminium alloys. The purpose of this study was to determine the effects of friction stir spot welding parameters on tensile shear strength of friction stir spot welded lap joint EN AW 5005 Aluminium alloy. The variable parameters were tool rotation (rpm), dwell time (s) and the tool pin height (mm). Tensile shear test results indicated that the weld performance was significantly affected by the tool rotation, dwell time and the tool pin height. The results of the study indicates that there are optimum process parameters which give the highest tensile shear strength.

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