十字接头恒幅和变载荷历程疲劳试验结果及预测

对十字接头分别进行恒辐轴向载荷和变载荷历程疲劳试验，接头疲劳裂纹通常开始发生在焊缝根部，但如果接头变形引起的弯曲应力较大，疲劳裂纹也可能发生在焊缝趾部。本研究试图找出影响焊接接头疲劳寿命各参数之间的相互关系，并利用作者引伸的焊接接头疲劳裂纹起始－扩展模型较精确地预测复杂焊件的疲劳寿命。该模型把疲劳裂纹起始寿命看成是疲劳裂纹萌生，早期生成并聚合成主疲劳裂纹的循环次数，利用应变控制疲劳数据和Ｐａｌｍｇ

Constant Amplitude and Variable Load History Fatigue Test Results and Predictions for Cruciform Weld

Cruciform welds were fatigue tested under constant amplitude axial load and variable load history conditions.Fatigue cracks generally initiate at the root but may initiate at the toe if higher bending stresses are induced by joint distortion.This study attempts to interrelate the parameters that influence the fatigue life of weldments and to predict accurately the fatigue lives of complex weldments using an initiation-propagation model developed by author.The model for the predictions assumes that the fatigue crack initiation period(N I) is the number of cycles for the initiation of a fatigue crack and its early growth and coalescence into a dominant fatigue crack.N I is estimated using strain-controlled fatigue data and the Palmgren-Miner linear damage cumulation rule through Knowledge of the local stress and strain response at the tip of the notch.The fatigue crack propagation period(N I) is estimated using fatigue propagation data and the power law of Paris.The fatigue test results were compared with predictions made using the analytical model and good agreement between experiment and theory was observed.Moreover,the study indicated that the fatigue crack initiation period is the main portion of the total fatigue life at long lives.