Strength and fatigue failure of spot friction welds between similar anddissimilar sheet materials.

Strength and Fatigue Failure of Spot Friction Welds (Or Friction Stir Spot Welds) Between Similar and Dissimilar Sheet Materials Are Investigated Base;Mechanical Engineering;Engineering;Mechanical Engineering

Tran, Van-XuanLu, Wei ;

University of Michigan

关键词: Strength and Fatigue Failure of Spot Friction Welds (Or Friction Stir Spot Welds) Between Similar and Dissimilar Sheet Materials Are Investigated Base;    Mechanical Engineering;    Engineering;    Mechanical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/63732/xuantran_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Strength and fatigue failure of spot friction welds (or friction stir spot welds) between similar and dissimilar sheet materials are investigated based on a combined experimental, numerical and theoretical approach.Aluminum 5754-O and 6111-T4 welds, two types of dissimilar welds joining aluminum 5754-O and 7075-T6 sheets (denoted as 5754/7075 and 7075/5754 welds), and dissimilar welds joining aluminum 6000 and coated steel sheets (denoted as Al/Fe weld) in lap-shear and cross-tension specimens are tested under quasi-static and cyclic loading conditions.Optical and scanning electron micrographs of the 5754, 6111, 5754/7075, 7075/5754 and Al/Fe welds before and after failure are examined to investigate the fracture and failure mechanisms.Effects of processing time on the strength and failure mode of the 5754/7075 and 7075/5754 welds under lap-shear loading conditions are investigated.Different fatigue life estimation models based on the closed-form structural stress and stress intensity factor solutions, and the Paris law with the parameters obtained from finite element analyses and experiments predicted well the fatigue lives of the welds with different cracking patterns.The effective stress intensity factor and integral solutions at the critical locations of the welds appear to be good parameters to correlate the experimental fatigue data for the 5754/7075, 7075/5754 and Al/Fe welds in lap-shear and cross-tension specimens.The analytical stress intensity factor and integral solutions for spot welds with ideal geometry, gap and bend joining two sheets of different materials and thicknesses in lap-shear specimens are developed.The results obtained from three-dimensional finite element analyses confirm the accuracy of the analytical solutions. Comparisons of the results obtained from the finite element models based on the micrographs of the welds before testing and the analytical solutions for spot welds with ideal geometry indicate that the complex geometries of aluminum 6111 resistance spot weld and aluminum 5754 spot friction weld appear not to affect the stress intensity factor and integral solutions, whereas the complex geometry, gap and bend of the Al/Fe spot friction weld appear to strongly affect the stress intensity factor and integral solutions.The results obtained from the theoretical and numerical models are in agreement with experimental observations.