Fatigue analyses for swept friction stir spot welds in lap-shear specimens of alclad 2024-T3 aluminum sheets

2014 ◽  
Vol 61 ◽  
pp. 129-140 ◽  
Author(s):  
Z.-M. Su ◽  
R.-Y. He ◽  
P.-C. Lin ◽  
K. Dong
Keyword(s):  
Spot Welds ◽  
Friction Stir ◽  
Aluminum Sheets ◽  
Lap Shear

Fatigue Behavior of Magnesium AZ31 in Friction Stir Spot Welds

2009 ◽  
Author(s):  
J. B. Jordon ◽  
M. F. Horstemeyer ◽  
H. Badarinarayan ◽  
J. Grantham
Keyword(s):  
Fatigue Life ◽  
Crack Growth ◽  
Fatigue Behavior ◽  
Spot Welds ◽  
Friction Stir ◽  
Lap Shear ◽  
Magnesium Az31 ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Crack Growth Modeling

In this study, the fatigue behavior of AZ31 magnesium friction stir spot welded joints is experimentally investigated. The friction stir spot welds employed here 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 and were fatigued until failure to determine stress-life properties. The fractured coupons were examined under optical and scanning electron microscopes with the intent to determine fatigue crack characteristics. Fractography analysis suggests that long crack growth accounts for a majority of the fatigue life. To predict the fatigue life of the lap-joint coupons, a long crack growth modeling approach, based on a kinked crack stress intensity solution, was employed. The fatigue model predictions compared well to the experimental stress-life results.

Failure Mode and Fatigue Behavior of Dissimilar Friction Stir Spot Welds in Lap-Shear Specimens of Transformation-Induced Plasticity Steel and Hot-Stamped Boron Steel Sheets

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
S. H. Hong ◽  
S.-J. Sung ◽  
J. Pan
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Behavior ◽  
Boron Steel ◽  
Loading Conditions ◽  
Test Results ◽  
Spot Welds ◽  
Transformation Induced Plasticity ◽  
Friction Stir ◽  
Lap Shear ◽  
Cycle Loading

Failure mode and fatigue behavior of dissimilar friction stir spot welds in lap-shear specimens of transformation-induced plasticity steel (TRIP780) and hot-stamped boron steel (HSBS) sheets are examined in this paper. Optical micrographs of the dissimilar TRIP780/HSBS friction stir spot welds made by a concave silicon nitride tool before and after testing are obtained and examined. These micrographs indicate that subject to quasi-static and cyclic loading conditions, the TRIP780/HSBS welds fail from cracks growing through the TRIP780 sheets where the tool was plunged into and the thickness was reduced. The bending moments and the transverse shear force near the welds are derived with consideration of the load offset, the weld gap, and the bend distance for calculation of analytical global stress intensity factor solutions for the welds in lap-shear specimens. A fatigue model of kinked crack growth is used to estimate fatigue lives based on the local stress intensity factor solutions for kinked cracks. The estimated fatigue lives with consideration of the weld gap and the bend distance are in agreement with the fatigue test results under low-cycle loading conditions and lower than the fatigue test results under high-cycle loading conditions. The estimated fatigue lives suggest that the weld gap and the bend distance can significantly affect fatigue lives of the friction stir spot welds in lap-shear specimens under cyclic loading conditions.

The Effect of Microstructural and Geometrical Features on Fatigue Performance in Mg AZ31 Friction Stir Spot Welds

2011 ◽  
Author(s):  
J. B. Jordon
Keyword(s):  
Optical Microscopy ◽  
Weld Zone ◽  
Sheet Thickness ◽  
Fatigue Performance ◽  
Welding Parameters ◽  
Spot Welds ◽  
Friction Stir ◽  
Lap Shear ◽  
Nugget Diameter ◽  
Geometrical Features

The relationship of microstructural and geometrical features to fatigue performance is investigated in friction stir spot welds made using AZ31 magnesium alloy sheets. Lap-shear coupons were spot welded using two sets of welding parameters. Optical microscopy of the initial state of the microstructure of each set of spot welds revealed differences in the hook formation, sheet thickness in the weld zone, and nugget diameter. Both sets of welds were fatigue tested in load control until failure at various load ratios. Optical microscopy of the failed coupons revealed differences in the fracture mode between the two sets of coupons. A linear elastic fracture mechanics model was used to correlate the fatigue life in the two processes. The fatigue model, which is a function of hook size, sheet thickness, and nugget diameter, showed good correlation to the experimental results. The model was also employed to show that the fatigue of the friction stir spot welds was most sensitive to the sheet thickness in the weld zone, followed by hook height, and then nugget diameter.

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.

Dissimilar Friction Stir Lap Welding of AA2198 and AA7075 Sheets: Forces, Microstructure and Mechanical Properties

2021 ◽  
Author(s):  
Antonello Astarita ◽  
Fausto Tucci ◽  
Alessia Teresa Silvestri ◽  
Michele Perrella ◽  
Luca Boccarusso ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Welding Process ◽  
Processing Parameters ◽  
Processing Parameter ◽  
Friction Stir Lap Welding ◽  
Friction Stir ◽  
Lap Shear ◽  
Microstructure And Mechanical Properties ◽  
Lap Welding ◽  
Factorial Design Of Experiments

Abstract This paper deals with the dissimilar friction stir lap welding of AA2198 and AA7075 sheets. The influence of processing parameters, namely welding speed and tool rotational speed on joint features, microstructure, and mechanical properties were investigated implementing a full factorial design of experiments. During the welding process, axial and transversal forces were continuously measured using a dedicated sensed fixture aiming at the correlation of this processing parameter with the quality of the achieved joints. The reported outcomes showed a very narrow processing window in which it was possible to avoid the formation of defects while the formation of an hook was observed for all the joints welded. The influence of the weld bead morphology on the lap shear strength was elucidated proving that the strength is ruled by the hook morphology. A correlation between the process parameters and the forces arising was also attempted. The final microstructure of the joints was studied and explained and also compared with the microhardness results.

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.

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