渗碳层断裂韧性评定新方法

Evaluation of the Fracture Toughness of Deep Carburized Layer

本文依据裂纹沿渗碳层扩张时所特有的ＰＯＰ－ｉｎ现象提出了一种评定渗碳层断裂韧性的新方法。研究表明：ＰＯＰ－ｉｎ现象是渗碳层断裂韧性正梯度分布造成的；根据ＰＯＰ－ｉｎ点处的载荷及相应的裂纹长度计算出的渗碳层ＫＩＣ－ｘ分布曲线是评定其断裂韧性的基础。

The composite nayure of case hardened materials,in which there exista gradients of microstructure、toughness and residual stress,ensures that the fracture in the case layer is quite different from that of homogeneous materials.In this paper an improved method to evaluate the fracture toughness of a deep carburized layer is discussed according to the appearance of 'pop in' phenomenon when the crack propagates through the carburized layer.The results show that:'pop in' phenomenon is caused by the gradient distribution of the fracture toughness、microstructure and the residual stress in the carburized layer.The K IC X (distance from notch)distribution curves calculated from the load and the crack length at the 'pop in' point is the basis for evaluation of the fracture toughness.