挤压强化对LY12CZ板材疲劳裂纹起始寿命的影响

THE EFFECT OF COLD EXPANSION ON FCIL OF LY12CZ ALLOY

1.引言 以往研究者着重研究了挤压强化对疲劳裂纹扩展速率和总寿命的影响,而最近研究分析表明,挤压强化对改善裂纹起始寿命(N_i)也具有很大作用,但是,关于挤压强化后,疲劳裂纹起始寿命的定量表达式还未见报道。

The effect of cold expansion of holes on the fatigue crack initiation life of LY12CZ aluminium alloy sheets are experimentally investigated, and a quantitative expression of the fatigue crack initiation life is also given. The observation during fatigue testing shows that, after the cold expansion of holes, the fatigue crack almost initiates on the entry face, from which the mandrel is introduced into the holes, Therefore, it may be thought that the entry face is less resistant to fatigue crack initiation. In addition, the assumption on the equivalence of the residual stress and strain hardening conditions on both of the entry and exit faces may be questionable.