Date

2014

Document Type

Thesis

Degree

Master of Science

Department

Mechanical Engineering

First Adviser

Nied, Herman F.

Abstract

Thermomechanical simulation of welding is very useful for developing a better understanding of how residual stresses evolve during welding operations. Detailed information about welding residual stresses can be of great benefit for better predictions of fatigue behavior in welded structures, since it is generally recognized that improvements in weld quality and reduction in welding residual stresses are necessary for increased fatigue life. In this study, we use computational simulation to simulate the residual stress distribution after welding. Of particular interest are the local stresses at the edge of a fillet weld; a location known to be the most likely site for fatigue crack initiation. Three models with different fillet geometry are developed to investigate how the geometry of fillet weld influences the residual stress under different clamping conditions and with different material properties. The fillet geometry not only affects the residual stresses directly, because of the stress concentration due to the geometry change, but also affects the residual stresses indirectly, through metallurgical changes in the Heat Affect Zone (HAZ). The results near the weld toe, where stress concentration effects are strongest, are are of the greatest interest. The convergence and accuracy of the stress results are verified by systematically preforming repeated simulations using different mesh refinements close to the weld toe.

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