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采用自行研制的超声疲劳实验装置,研究不同表面粗糙度下Ti-6Al-4V合金的超高周疲劳性能.结果表明,当表面凹痕宽深比a/c(a为凹痕宽度,c为凹痕深度)在2~10之间时,Ti-6Al-4V合金的临界凹痕深度在0.49~1.10μm之间.当表面凹痕深度小于临界深度时,表面粗糙度对Ti-6Al-4V合金的超高周疲劳性能没有影响.当表面凹痕深度大于临界深度时,Ti-6Al-4V合金疲劳寿命随表面粗糙度的增加而下降,并且随着循环周次的增加,Ti-6Al-4V合金疲劳性能对表面粗糙度的敏感性下降.随着表面粗糙度的增加,Ti-6Al-4V合金超高周疲劳裂纹的萌生方式发生变化.超高周疲劳裂纹源有由一个向多个、由内部向次表面转移的趋势;当表面凹痕深度增加到一定程度后,在超高周疲劳寿命区间,Ti-6Al-4V合金疲劳寿命随粗糙度的增加而大幅下降.疲劳裂纹全部从合金表面凹痕根部处萌生,没有内部萌生的情况.
The ultrahigh-cycle fatigue behavior of Ti-6Al-4V alloy with different surface roughness was studied by using the ultrasonic fatigue experimental device developed by ourselves.The results show that when the ratio of surface depth to width a / c (a is the width of dent, c is The depth of the dents of Ti-6Al-4V alloy is between 0.49 and 1.10μm when the depth of dents is between 2 and 10. When the depth of surface dents is less than the critical depth, the surface roughness of Ti-6Al-4V The fatigue life of Ti-6Al-4V alloy decreases with the increase of surface roughness when the depth of surface pitting is greater than the critical depth. With the increase of cycle times, the fatigue life of Ti-6Al- 4V alloy decreased the surface roughness sensitivity.With the increase of surface roughness, Ti-6Al-4V alloy ultrahigh cycle fatigue crack initiation method changes.High cycle fatigue crack source from one to more than one , The trend of the transfer from the interior to the sub-surface tends to decrease.When the depth of the surface indentation increases to a certain degree, the fatigue life of the Ti-6Al-4V alloy decreases sharply with the increase of the roughness in the ultrahigh-cycle fatigue life. Dents root initiation at the alloy surface, there is no internal initiation.