拉-拉疲劳载荷对孔壁强度的影响

在疲劳断裂的中心圆孔试样孔壁取样进行显微硬度与残余应力的测试,结合有限元模拟结果对测试数据进行分析,从孔壁强度变化的角度研究孔零件在拉-拉载荷作用下发生疲劳断裂的原因。结果表明:疲劳断裂中心圆孔试样孔壁出现显微硬度梯度,长度方向孔壁表面获得最大硬度,宽度方向孔壁亚表层获得最大硬度,说明孔壁不同部位经受循环塑性应力影响程度不同,宽度方向孔壁发生应变硬化后循环软化成为薄弱区域;孔壁不同部位获得不同的切向残余应力场分布,长度方向孔壁表面获得最大残余压应力,宽度方向孔壁亚表层获得最大残余压应力,应力集中效应最强的宽度方向孔壁表面成为薄弱区域。

Influence of Tensile Fatigue Load on Hole Wall Strength of Parts with Hole

Further research was performed to find out the causes of fatigue fracture from the perspective of hole wall strength change under tensile load;test data were analyzed based on the tested microhardness and residual stress, combined with the finite element simulation result. The analysis results show that the fatigue fracture samples present microhardness gradient. The hole wall surface of length direction has maximum hardness;the hole wall subsurface of width direction has maximum hardness. The effect of cyclic plastic stress on the hole wall differs with the change of position of the hole wall. The hole wall of width direction presents strain hardening first and then cyclic softening, and thus becomes the weak area. Different position of hole wall has different tangential residual stress field distribution. The hole wall surface of length direction has maximum residual compressive stress;the hole wall subsurface of width direction has maximum residual compressive stress. The hole wall surface of width direction becomes the weak area, resulting from stress concentration effect.