This paper has got the magnetic memory testing signals ( the normal component and the grads of the magnetic field) and analyzed the diversification character of the magnetic memory testing signals of the welded line when it has or don′t has cracks through the tensile loading aimed at the steel jointing workpiece of Q345R. The experimentation result has shown that this method can′t estimate the existing of the crack in the welded line because of the residual stress before the tensile loading. And the two kinds jointing workpieces have shown obviously elimination process of residual stress through the tensile load-ing. When there is a load the jointing workpiece with crack presents itself partial change during the elas-ticity phase and the whole yield phase,and the grads of the magnetic field around the welded line of the jointing workpiece without crack diminishes stage by stage during the elasticity phase. Only when it turns into the yield phase it has the same character diversification as the jointing workpiece with crack.%针对Q345R钢焊接试件,通过拉伸加载,获取拉伸过程中磁记忆检测信号(磁场的法向分量、磁场变化梯度),比较分析了焊缝中有无裂纹时磁记忆信号的变化特征.试验结果表明,在加载之前,由于焊接残余应力的存在,该方法并不能判断焊缝中是否有裂纹,经拉伸加载,两类焊接件出现明显的残余应力消除过程,加载后有裂纹焊接件在弹性阶段出现局部变化,且存在于整个屈服阶段;在弹性阶段,无裂纹焊接件随载荷增加焊缝部位磁场梯度值逐渐减小,进入屈服阶段后才开始出现与有裂纹试件有相似特征的变化.
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