小缺口疲劳启裂门槛值的平面应力与平面应变效应

On the plane stress and plane strain effect of fatigue-crack initiation at sharp notch

文章报告了两组 Q2 3 5钢小缺口试件在平面应力与平面应变条件下的疲劳启裂门槛值的测定结果。实验表明 :不论平面应力还是平面应变状况 ,当ρ→ 0时 ,Δσ∞th均有截止性。但对平面应力状况 ,Δσ∞th截止后持平 ,而对平面应变状况 ,Δσ∞th截止后反有小幅上升。该文从缺口顶端应力场和循环塑性区的展开出发对试件结果作了分析和讨论。

In this paper,the experimental results of fatigue initiation threshold at sharp notch are reported for two groups of Q 235 steel under plane stress and plane strain conditions. It is found that whether under plane strain conditions or under plane stress conditions, when ρ→0, Δ σ ∞ th  has the characteristic of cut off.Under plane stress conditions,  Δ σ ∞ th  was constant after cut off. But under plane strain conditions,  Δ σ ∞ th  increased within a narrow range after cut off. Based upon the analysis of the solutions of stress field and circular plastic zone at crack tip, the obtained results are discussed.