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在不同条件下,由于滚动接触疲劳而在各种材料中产生的组织变化,可分为四种类型(黑色区、黑针、黑线条和白色条带)。组织变化的类型取决于试验温度、材料的抗回火性、接触应力和负载循环次数。某些情况下,在负载循环过程中的不同阶段上,可挨次观察到称为黑色区、黑针、黑线条的组织变化。 在滚动接触疲劳的初始阶段,由剪切应力T_(45)产生残余压应力。当接触应力大于Pmax=600公斤/毫米~2时,应力峰达到饱和状态,试样硬度较低时,应力峰值也较小。 经10~6次循环之后,显微硬度升高。被认为是由Y_o产生的加工硬化所致。一旦当负荷循环次数增加,出现黑线条类型的组织变化时,硬度就会局部降低。虽然变化的组织实际上是软的,但这组织变化却使滚动疲劳寿命更长。 不同研究者得到的不同类型的组织变化,被认为是由于试验条件的不同所致,特别是试样温升,它不仅受接触应力的影响,也受旋转速度和接触面积的影响。
Under different conditions, tissue changes in various materials due to rolling contact fatigue can be classified into four types (black area, black stitch, black streak and white streak). The type of tissue change depends on the test temperature, the tempering resistance of the material, the contact stress and the number of load cycles. In some cases, changes in the tissue called black areas, black needles, black lines can be observed in sequence at different stages of the load cycle. In the initial stage of rolling contact fatigue, the residual compressive stress is generated by the shear stress T_ (45). When the contact stress is greater than Pmax = 600 kg / mm ~ 2, the stress peak reaches the saturation state, and the stress peak value is also smaller when the hardness of the sample is lower. After 10 to 6 cycles, the microhardness increased. It is thought to be caused by work hardening caused by Y_o. Once the load cycle increases, the occurrence of black line type of tissue changes, the hardness will be reduced locally. Although the changing organization is actually soft, this organizational change leads to longer rolling fatigue life. Different types of tissue changes obtained by different researchers are considered due to different test conditions, especially the temperature rise of the sample, which is affected not only by the contact stress but also by the rotation speed and the contact area.