金属材料疲劳裂纹扩展速率估计的分层模型

裂纹扩展速率与应力强度因子幅值的关系曲线，是金属构件损伤容限设计及寿命预测的重要疲劳性能数据．为了充分、合理地运用在不同测试条件下获得的试验数据，分层随机样本模型，将总体样本分为若干层，每一层样本都是在相同的测试条件下获得的试验数据，结合压力容器的实际工作状况，对每一层样本赋予适当的权重，从而对疲劳裂纹扩展速率方程做出更符合实际要求的估计．实际计算表明，对不同炉号试样提供的Q235A级钢材的裂纹扩展速率数据，运用分层随机样本模型得到的结果，明显地优于运用简单随机样本模型分别处理每个炉号试样提供的数据所得的结果．

Stratified Model for Estimating Fatigue Crack Growth Rate of Metallic Materials

The curve of relationship between fatigue crack growth rate and the stress strength factor amplitude represented an important fatigue property in designing of damage tolerance limits and predicting life of metallic component parts. In order to have a more reasonable use of testing data, samples from population were stratified suggested by stratified random sample model (SRAM). The data in each stratum corresponded to the same experiment conditions. A suitable weight was assigned to each stratified sample according to the actual working states of the pressure vessel, so that the estimation of fatigue crack growth rate equation was more accurate for practice. An empirical study shows that the SRAM estimation by using fatigue crack growth rate data from different stoves is obviously better than the estimation from simple random sample model.