单边裂纹电磁热止裂强化的残余应力分析

建立带有单边裂纹的无限大金属薄板模型,给出脉冲放电瞬间的温度场,应用一维条件下的热弹塑性理论,导出了单边裂纹金属构件电磁热止裂后的一维残余应力解;对带有单边裂纹的导电薄板脉冲放电后裂纹尖端产生的残余应力进行数值分析,理论与数值分析结果基本吻合;对40CrNiMo试件的残余应力超声波无损检测发现,止裂后残余应力变大。研究表明,在对带有单边裂纹的导电薄板进行电磁热止裂时,裂纹尖端周围温度急剧升高,使得裂纹尖端受热膨胀,由于裂尖受到周围材料的刚性约束,在受热和冷却过程中会残留一个压缩塑性应变,其产生的残余应力可有效的抑制裂纹扩展。

Analysis on residual stress after crack arrested by using electromagnetic heating

Establishing infinite metal sheet model with an single side crack,giving the temperature field for the pulse discharge,applying heat elastic-plastic theory under the condition of one-dimension,the one dimensional residual stress solution for the metal components with single side crack after electromagnetic heating crack arrest was derived.Numerical analysis on the residual stress at the crack tip of thin conductive plate with single side crack after pulse discharge shows the theoretical calculation is coincide with numerical analysis.The residual stress around the crack tip in 40CrNiMo component before and after pulse discharge was checked by ultrasound contrast method.Results show that the residual stress change greatly after crack arrest.When the side-crack of thin conductive plate is arrested using electromagnetic heating,the temperature around the crack tip rise quickly and the crack tip expands due to heating.The crack tip is rigidly constrained by the surrounding material,so a compressed plastic strain would remain within the heating and cooling process,the residual stress produced would effectively constrain the extending of the crack.