Effect of stirring time on the mechanical behavior of friction stir spot weld of Al 6061-T6 lap-shear configuration

2018 ◽  
Vol 233 (10) ◽  
pp. 3583-3591 ◽  
Author(s):  
Amirreza Shahani ◽  
Ali Farrahi
Keyword(s):  
Mechanical Behavior ◽  
Failure Modes ◽  
Static Strength ◽  
High Load ◽  
Welding Condition ◽  
Friction Stir ◽  
Al 6061 ◽  
Lap Shear ◽  
Low Load ◽  
Stirring Time

The effect of five different stirring times of friction stir spot welding on lap-shear specimens of Al 6061-T6 alloy has been experimentally analyzed. The welding condition with 2 s of stirring shows the optimum mechanical behavior in comparison to the others. The static strength and fatigue behavior of the joint are justified using the microhardness profiles. The static results prove that the increase of stirring time beyond the 2 s case has little effect on improving the static strength. The fatigue results reveal two different failure modes, which are shear fracture at high load levels and transverse crack growth at low load levels. At medium load levels, although the final failure is similar to high load levels, the transverse growth of the crack outside the welding zone, just like low load levels, is also observed.

Sensor Fusion and On-Line Monitoring of Friction Stir Blind Riveting for Lightweight Materials Manufacturing

2021 ◽  
pp. 1-36
Author(s):  
Zhe Gao ◽  
Haris Khan ◽  
Jingjing Li ◽  
Weihong Guo
Keyword(s):  
Sensor Fusion ◽  
Failure Modes ◽  
Processing Parameters ◽  
Data Driven ◽  
Structure Property ◽  
Cross Sectional ◽  
Friction Stir ◽  
In Situ Data ◽  
Lap Shear

Abstract This research focused on developing a hybrid quality monitoring model through combining the data driven and key engineering parameters to predict the friction stir blind riveting (FSBR) joint quality. The hybrid model was formulated through utilizing the in-situ processing and joint property data. The in-situ data involved sensor fusion (force and torque signals) and key processing parameters (spindle speed, feed rate and stacking sequence) for data-driven modeling. The quality of the FSBR joints was defined by the tensile strength. Further, the joint cross-sectional analysis and failure modes in lap-shear tests were employed to confirm the efficacy of the proposed model and development of the process-structure-property relationship.

scholarly journals Preliminary study on the mechanical behavior of friction spot welds

2009 ◽  
Vol 14 (3) ◽  
pp. 238-247 ◽  
Author(s):  
José Antônio Esmerio Mazzaferro ◽  
Tonilson de Souza Rosendo ◽  
Cíntia Cristiane Petry Mazzaferro ◽  
Fabiano Dornelles Ramos ◽  
Marco Antônio Durlo Tier ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mechanical Behavior ◽  
Spot Welding ◽  
Mechanical Response ◽  
Analysis Procedure ◽  
Research Centre ◽  
Friction Stir ◽  
Lap Shear ◽  
State Process ◽  
Welding Processes

The Friction Spot Welding - FSpW is a solid-state process that allows joining two or more metal sheets in lap configuration with no residual keyhole as occurs in the Friction Stir Welding - FSW process. The present work reports part of the efforts made at GKSS Research Centre to better understand the complex phenomena that take place during FSpW of aluminum alloys and establish the mechanical response of the resulting joints. Over the recent years the research on modeling friction based welding processes has increased considerably. Most of the works related to this subject deal with the process mechanics. On the other hand, some investigations have shown how the process variables affect the mechanical properties of the joints, but it is very difficult to find quantitative results that can be readily used for mechanical design purposes. The aim of this work is to develop an analysis procedure based on the process characteristics that allows evaluating how the resulting geometry and microstructure affect the joint mechanical behavior. For this, the results of the mechanical tests obtained on AA2024-T3 aluminum alloy were used to calibrate and validate a numerical model that was used to predict the joint failure mode. The model reproduced the specimen geometry and load conditions adopted in the lap-shear and cross-tensile tests. The joint was considered as formed by three main regions (SZ - stir zone, TMAZ - thermo mechanically affected zone and HAZ - heat affected zone) whose properties and dimensions were based in microhardness evaluation and macrographic analysis of welded specimens. It was observed a good agreement between the simulation results and experimental data. The numerical modeling of the joints allows the prediction of the joint mechanical properties, as well as to understand how a change in geometry and property of each region affects the final mechanical behavior. Based in the obtained results, the analysis procedure can be easily extended to the related friction based spot processes as Friction Stir Spot Welding - FSSW.

scholarly journals Dynamic Behavior of Self-Piercing Riveted and Mechanical Clinched Joints of Dissimilar Materials: An Experimental Comparative Investigation

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Yulong Ge ◽  
Yong Xia
Keyword(s):  
Mechanical Behavior ◽  
Failure Modes ◽  
Dissimilar Materials ◽  
Dynamic Effect ◽  
Comparative Investigation ◽  
Rate Dependent ◽  
Lap Shear ◽  
Baking Process ◽  
Before And After ◽  
Peel Tests

The present work compares the dynamic effect of a self-piercing riveted (SPR) joint with that of a mechanical clinched joint having the dissimilar materials combination. The substrates used in this investigation are aluminum alloy AA5182-O and deep drawing steel DX51D+Z. The static and dynamic behaviors and the failure modes of the SPR and clinching joints are characterized by lap-shear, cross-tension, and coach-peel tests. The influence of the strain-rate-dependent mechanical behavior of the substrates on the joints is examined; this can help improve prediction of the energy absorption of the joints under impact loading. Considering the realistic baking process in a painting shop, the deforming and hardening effects on the SPR and the clinched joints induced by baking are also studied. The specimens are heated to 180°C for 30 min in an oven and then cooled down in air. The SPR and the clinched joints before and after the baking process are compared in terms of the mechanical behavior.

scholarly journals Experimental investigation of typical connections for fabricated cold-formed steel structures

2018 ◽  
Vol 22 (1) ◽  
pp. 141-155
Author(s):  
Weiming Yan ◽  
Tingting Mu ◽  
Zhiqiang Xie ◽  
Cheng Yu
Keyword(s):  
Mechanical Behavior ◽  
Failure Modes ◽  
High Efficiency ◽  
Design Method ◽  
Sheet Thickness ◽  
Steel Structures ◽  
Comparative Investigation ◽  
Lap Shear ◽  
Cold Formed Steel ◽  
European Standards

This article presents a comparative investigation on mechanical behavior and construction characteristics of some typical connections in cold-formed thin-walled steel. The lap shear tests of 96 specimens considering four typical connections with a self-piercing rivet, clinching, self-drilling screw, and blind rivet were conducted. The effects of sheet thickness and thickness ratio on failure modes and mechanical behavior of the four types of connections were investigated. Through analyzing the feasibility of mechanic and construction, the applicability of the four types of connections in fabricated cold-formed steel structures was comprehensively evaluated. The result of the research shows that compared with the other three connections, self-piercing rivet connections are more suitable for modularly fabricated cold-formed steel structures because of its superior mechanical properties, well-formed quality, high efficiency, and potential industrialization. Based on the design methods of fasteners in North American (AISI S100-16) and European standards (prEN1999-1-4) on cold-formed steel structures, an appropriate design method is proposed for self-piercing riveting connections.

Classification of Failure Modes in Friction Stir Blind Riveted Lap-Shear Joints With Dissimilar Materials

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Wei-Ming Wang ◽  
Haris Ali Khan ◽  
Jingjing Li ◽  
Scott F. Miller ◽  
A Zachary Trimble
Keyword(s):  
Failure Modes ◽  
Dissimilar Materials ◽  
Polymeric Composite ◽  
Tensile Tests ◽  
Great Promise ◽  
Lightweight Structures ◽  
Friction Stir ◽  
Lap Shear ◽  
Transportation Sector ◽  
Static Tensile

In transportation sector, there is an increasing need for joining dissimilar materials for lightweight structures; however, substantial barriers to the joining of dissimilar materials have led to an investigation and development of new joining techniques. Friction stir blind riveting (FSBR), a newly invented method, has shown great promise in joining complex structures with dissimilar materials. The process can be utilized more effectively if knowledge regarding the failure mechanisms of the FSBR joints becomes available. This research focuses on investigating the different mechanisms that lead to a failure in FSBR joints under lap-shear tensile tests. An in situ, nondestructive, acoustic emission (AE) testing method was applied during quasi-static tensile tests to monitor the initiation and evolution of damage in FSBR joints with different combinations of dissimilar materials (including aluminum, magnesium, and a carbon-fiber reinforced polymeric composite). In addition, a fractographic analysis was conducted to characterize the failure modes. Finally, based on the analysis, the distinct failure modes and damage accumulation processes for the joints were identified. An AE accumulative hit history curve was found to be efficient to discriminate the deformation characteristics, such as the deformation zone and failure mode, which cannot be observed through a traditional extensometer measurement method. In addition, the AE accumulative hit history curve can be applied to predict the failure extension or moment of FSBR joints through an identification of the changes in curve slope. Such slope changes usually occur around the middle of Zone II, which is defined in this study.

Fatigue Characterization and Modeling of Friction Stir Spot Welds in Magnesium AZ31 Alloy

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
J. B. Jordon ◽  
M. F. Horstemeyer ◽  
S. R. Daniewicz ◽  
H. Badarinarayan ◽  
J. Grantham
Keyword(s):  
Fatigue Life ◽  
Stress Intensity ◽  
Failure Modes ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Az31 Alloy ◽  
Spot Welds ◽  
Friction Stir ◽  
Lap Shear ◽  
Magnesium Az31

The fatigue behavior of friction stir spot welds in magnesium AZ31 alloy is experimentally investigated and modeled. The friction stir spot welds employed in this study are representative of preliminary welds made in developing the joining process for potential use in automobile manufacturing. Load control cyclic tests were conducted on single weld lap-shear coupons to determine fatigue life properties. Optical fractography of the failed fatigue coupons revealed that fatigue cracks initiated from the interfacial “hook” and eventually failed by either nugget pullout or full width separation, depending on the cyclic load amplitude. The failure modes of the magnesium AZ31 alloy were similar to the aluminum alloys of comparable friction stir spot welds. To predict the fatigue life of the lap-joint coupons, a crack growth modeling approach based on a kinked crack stress intensity solution was used. The fatigue model predictions compared well to the experimental fatigue life results, despite an approximate stress intensity factor solution for this weld geometry. The experiments and modeling conducted in this study suggest that the size of the interfacial hook, which comes about from the speed, depth of plunge, dwell time, and tool configuration of the friction stir spot weld process, is a major contributor to the fatigue life of the joint.

scholarly journals Refill Friction Stir Spot Welding Al Alloy to Copper via Pure Metallurgical Joining Mechanism

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Zhikang Shen ◽  
Yuquan Ding ◽  
Wei Guo ◽  
Wentao Hou ◽  
Xiaochao Liu ◽  
...  
Keyword(s):  
Spot Welding ◽  
Friction Stir Spot Welding ◽  
Alloy Sheet ◽  
Weld Strength ◽  
Al Alloy ◽  
Hardness Profile ◽  
Copper Sheet ◽  
Welding Condition ◽  
Friction Stir ◽  
Lap Shear

AbstractThe current investigation of refill friction stir spot welding (refill FSSW) Al alloy to copper primarily involved plunging the tool into bottom copper sheet to achieve both metallurgical and mechanical interfacial bonding. Compared to conventional FSSW and pinless FSSW, weld strength can be significantly improved by using this method. Nevertheless, tool wear is a critical issue during refill FSSW. In this study, defect-free Al/copper dissimilar welds were successfully fabricated using refill FSSW by only plunging the tool into top Al alloy sheet. Overall, two types of continuous and ultra-thin intermetallic compounds (IMCs) layers were identified at the whole Al/copper interface. Also, strong evidence of melting and resolidification was observed in the localized region. The peak temperature obtained at the center of Al/copper interface was 591 °C, and the heating rate reached up to 916 °C/s during the sleeve penetration phase. A softened weld region was produced via refill FSSW process, the hardness profile exhibited a W-shaped appearance along middle thickness of top Al alloy. The weld lap shear load was insensitive to the welding condition, whose scatter was rather small. The fracture path exclusively propagated along the IMCs layer of Cu9Al4 under the external lap shear loadings, both CuAl2 and Cu9Al4 were detected on the fractured surface on the copper side. This research indicated that acceptable weld strength can be achieved via pure metallurgical joining mechanism, which has significant potential for the industrial applications.

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