高温不锈钢与钛合金微动疲劳特性的实验研究

用桥式试样研究了接触压力、微动幅度、温度、循环次数、高低周载荷幅值比等参数对微动疲劳寿命影响。结果表明拉应力和法向压力均影响微动疲劳寿命。当拉应力较大时，微动疲劳寿命（FFL）与普通疲劳寿命（PFL）相差不大，法向压力的影响不明显；拉应力较小时，FFL显着低于PFL,且法向影响显着。FFL随法向压力增加而降低，但当超过200MPa后，反而提高。高低周幅值比的增加，FFL大幅度降低。当幅值比为0.125,从室温到450℃，PFL持续降低。而FFL从室温到200℃降低幅度较大，在300℃左右恢复，随后又降低。研究表明FFL的恢复是微动表面形成了防护性釉质层的结果。

EXPERIMENTAL STUDIES ON FRETTING FATIGUE OF STAINLESS STEEL AND TITANIUM ALLOY

The effects of contact pressure, amplitudes, applied loads, temperature, number of cycles and the ratio of high cycle load to low cycle one on fretting fatigue life and frictional coefficient were carried out. The test results indicate that both the tensile stress and the contact pressure affect the FFL. The difference between the PFL and FFL is not obvious for large tensile stresses and so does the effect of the contact pressure on the FFL. For small tensile stresses FFL is reduced greatly and the contact pressure affects the FFL heavily; it is reduced first with the increase of contact pressure at low contact pressure, but increases when the latter is greater than 200Mpa because of the decrease of amplitude. With the increase of temperature the FFL decreases from room temperature to 200℃, increases at about 300℃, and decreases again. The SEM studies reveal that it is flake like oxide that protects the contact surface from further damage and results in an enhancement of FFL.