一种疲劳长裂纹扩展率新模型

NEW MODEL FOR LONG FATIGUE CRACK GROWTH RATE

基于LZ50车轴裂纹扩展数据分析,提出描述长裂纹扩展的新模型。新模型包含门槛值和断裂韧度,并考虑循环比效应,可有效描述门槛值附近和高应力强度因子范围长裂纹的扩展行为及其趋于断裂点的行为；该模型克服了现有Paris-Erdogan模型不能描述门槛值附近和高应力强度因子范围,Forman-Kearney-Engle模型不能描述门槛值附近,Elber方程不能描述高应力强度因子范围疲劳裂纹扩展规律的缺陷。

A new model is presented for characterizing the propagation of long fatigue crack based on the analysis of test data of LZ50 carbon steel. The cracking threshold, fracture roughness and cyclic ratio are incorporated in the model. The behaviour of fatigue crack propagation nearby the cracking threshold is well reflected. And in the high stress intensity factor range the growth rate growing up to the critical fracturing point is well also revealed. The present model is derived from a comparing analysis of the existent models, i.e. Paris-Erdogan equation, Forman-Kearney-Engle model, and Elber equation. Paris-Erdogan equation is invalid to the regimes of nearby the cracking threshold and the stress intensity factor range. Forman-Kearney-Engle model is also invalid to the regime nearby the cracking threshold. And the Elber equation has a big deviation to the critical fracturing point in the high stress intensity factor range. All of the disadvantages in the existent models have been well overcome by the present model.