Fatigue behavior of AHSS lap shear and butt arc welds including the effect of periodic overloads and underloads

摘要

The effect of periodic overloads and underloads, which is a common occurrence in service load histories, on the fatigue behavior of AHSS (Advanced High Strength Steel) single lap shear and butt arc welds is investigated. A series of constant amplitude tests under tensile loading condition (R=P_(min)/P_(max)=0.1) were performed to obtain load amplitude-life curves for each type of arc welded joint. Variable amplitude load history tests, one with periodic overloads and another with periodic underloads were then conducted for each type of welded joint Additional constant amplitude fatigue tests at a high load ratio (R ≈ 0.6) representing the small cycles in the periodic underload loading were also performed. The validity of linear cumulative damage rule in the prediction of the fatigue life of these structures under variable amplitude loading is investigated. The results of the tests show that while periodic overloads did not affect the fatigue life of the welded joints, periodic underloads decreased the fatigue life. Finite element analyses were conducted to simulate the stress and strain states at the weld locations under overloads and underloads, the results of which were used to explain the observed experimental observations.