基于内部失效机理预测评估渗碳Cr-Ni齿轮钢的超高周疲劳强度

对渗碳Cr-Ni齿轮钢进行应力比为0和0.3的室温超高周疲劳实验，观测试样中诱发裂纹萌生的夹杂和疲劳断口形貌，以全面评估渗碳Cr-Ni齿轮钢疲劳性能。将疲劳失效模式分为有细颗粒区(Fine granular area,FGA)的内部疲劳失效和有表面光滑区(Surface smooth area, SSA)的表面疲劳失效，并阐明了渗碳Cr-Ni齿轮钢的超高周内部疲劳破坏机制。基于累积损伤和位错能量法并结合细颗粒区形成机理和夹杂的最大评估尺寸，分别构建了两种渗碳Cr-Ni齿轮钢内部疲劳强度的预测模型。利用FGA尺寸与夹杂尺寸的比值和夹杂应力强度因子及应力比之间的关系，修正所提出的两种疲劳强度预测模型并给出了最大夹杂尺寸下的l_FGA-S-N曲线。结果表明，基于累积损伤法和位错能量法分别构建的疲劳强度预测模型都可用于预测评估渗碳Cr-Ni齿轮钢在多种应力比下的内部疲劳强度，基于位错能量法的强度预测模型精度较高。

Prediction and Evaluation of Very-high Cycle Fatigue Strength of Carburized Cr-Ni Gear Steel Based on Interior Failure Mechanism

To evaluate the fatigue properties of carburized Cr-Ni gear steel, very high cycle fatigue tests were carried out at room temperature by stress ratios of 0 and 0.3. The fatigue failure modes of carburized Cr-Ni gear steel can be differentiated into interior fatigue failure with fine granular area (FGA) and surface fatigue failure with surface smooth area (SSA). According to the observation results of sites of inclusions and fatigue fracture morphology of the tested steels, therewith the interior very high cycle fatigue failure mechanism is clarified. Based on the cumulative damage method and the dislocation energy method, two kinds of interior fatigue strength prediction models for carburized Cr-Ni gear steels were established by taking the formation mechanism of fine granular area and the evaluated maximum size of inclusions into consideration. Based on the relationships between the relative size of FGA and the stress intensity factor of inclusion and stress ratio, the two fatigue strength prediction models were further modified, and the l_FGA-S-N curves for the maximum size of inclusions was given. The results show that the fatigue strength prediction model based on the cumulative damage method and the dislocation energy method can be used to evaluate the interior fatigue strength of carburized Cr-Ni gear steel by various stress ratios, however the prediction accuracy of the model based on the dislocation energy method is higher.