不同加载速率下PD3钢轨疲劳裂纹扩展行为研究

Study on Growth of Fatigue Crack of PD3 Rail Steel under Different Load Rate Condition

为研究弯矩作用下PD3钢轨的疲劳特性,在NENE-2型微动实验机上,对不同加载速率下的PD3钢轨进行了疲劳裂纹扩展性能实验研究。结果表明:PD3钢轨在弯矩作用下,随着载荷加载速率的增加,疲劳裂纹长度呈先增加,再减少的趋势。这说明该材料动态条件下断裂韧性与加载速率有较强的相关性。此时,疲劳裂纹由位错的移动速度和促进位错运动的热能共同作用与控制,当二者达到平衡时,疲劳裂纹最容易萌生与扩展。

The growth behavior of fatigue crack of PD3 rail steel under moment of flexure condition was investigated using NENE-2 fretting test machine. The results indicate that the size of fatigue crack firstly increases and then decreases with the increase of loading velocities under the bending moment. Fracture toughness is highly related to the loading rate under dynamic condition. Fatigue crack is the interaction of the moving speed of dislocation and the heat energy which promote the motion of the dislocation. When they reached equilibrium, the initiation and growth of fatigue crack is easily.