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研究了三种高强度或超高强度高韧性空冷贝氏体钢在油润滑条件下的接触疲劳行为。发现引起麻点剥落的疲劳裂纹不仅可在接触表面 ,也可以在距表面一定深度下的亚表面萌生 ,亚表面萌生裂纹的深度比理论计算最大剪切应力所在深度小近一个数量级 ,裂纹萌生由塑性变形和剪应力共同作用产生 ,一端向接触表面扩展 ,到达表面后润滑油被挤压进入裂纹中产生支点效果 ,另一端向最大剪应力深度扩展 ,最后在外力和润滑油支点共同作用下 ,由裂纹包围的金属屑被折断 ,形成疲劳剥落坑。钢的初始硬度或强度在低接触应力下对接触疲劳寿命影响不明显 ,在高接触应力下影响显著 ,初始硬度越高 ,接触疲劳寿命越长。
The contact fatigue behavior of three kinds of high strength or ultrahigh strength and toughness air cooled bainitic steels under oil lubrication was studied. It was found that the fatigue crack caused by flaking of pitting was not only on the contact surface but also on the sub-surface at a certain depth from the surface. The depth of sub-surface initiation crack was one order of magnitude smaller than the depth at which theoretical maximum shear stress was calculated. Plastic deformation and shear stress together, one end to the contact surface expansion, arrived at the surface after the oil is squeezed into the crack to produce the fulcrum effect, the other end to the maximum shear stress depth extension, and finally in the external force and lubricating oil joint action, The metal shavings surrounded by the crack are broken to form a fatigue peel pit. The initial hardness or strength of steel has little effect on the contact fatigue life under low contact stress, but has a significant effect under high contact stress. The higher the initial hardness, the longer the contact fatigue life.