Stress Intensity Factor Solutions For Laser Welds in Lap-Shear Specimens and Spot Welds in the Square Overlap Parts of Cross-Tension Specimens.

Stress Intensity Factor;Cross-tension Specimen;Spot Welds;Laser Welds;Lap-shear Specimen;Mechanical Engineering;Engineering;Mechanical Engineering

Sripichai, KulthidaLu, Wei ;

University of Michigan

关键词: Stress Intensity Factor;    Cross-tension Specimen;    Spot Welds;    Laser Welds;    Lap-shear Specimen;    Mechanical Engineering;    Engineering;    Mechanical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/91592/kulthida_1.pdf?sequence=1&isAllowed=y

瑞士|英语

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

【 摘 要 】

In the first part of the thesis, the stress intensity factor solutions for laser welds in lap-shear specimens are investigated.Finite element analyses of laser welded lap-shear specimens are carried out.Approximate closed-form stress intensity factor solutions based on the results of the finite element analyses in combination with the analytical solutions based on the beam bending theory and Westergaard stress function for a full range of the normalized weld widths are developed. Next, finite element analyses for local stress intensity factor solutions for kinked cracks in laser welded lap-shear specimens are carried out for selected normalized weld widths.The global and local stress intensity factor solutions for vanishing and finite kinked cracks are then adopted in a fatigue crack growth model to estimate the fatigue lives of the laser welds.The fatigue life estimations based on the fatigue crack growth model compare well with the experimental results.In the second part of the thesis, the stress intensity factor solutions for spot welds in the square overlap parts of cross-tension specimens are investigated.Three-dimensional finite element analyses for a rigid inclusion in a square plate are performed.The computational results indicate that the equivalent radius obtained from finite element analyses are lower than the equivalent radius used in the closed-form solutions of Lin and Pan.This is the main reason for the inaccuracy of the closed-form stress intensity factor solutions of Lin and Pan.The other deficiency of the closed-form stress intensity factor solutions of Lin and Pan comes from the flexibility of the spot welds as identified in this investigation.The structural stress solutions for a rigid inclusion in a square plate based on the closed-form structural solutions of Lin and Pan with the proposed equivalent radius and correction factors are developed and used to calculate the stress intensity factor solutions.The new stress intensity factor solutions at the critical locations for spot welds between sheets of different thicknesses and materials are presented in the normalized form for engineering applications for fatigue analyses of similar and dissimilar welds in lightweight automotive body structures and batteries.