污染颗粒对Si_3N_4陶瓷球疲劳影响的研究

Effect of debris contamination on Si_3N_4 ceramic fatigue balls

为了准确评价Si_3N_4陶瓷球间接触疲劳行为和抗污染能力,用四球疲劳试验机在7.01 GPa名义接触应力条件下分别进行了由清洁的32号机械油润滑(A组)和质量分数1％SiO_2颗粒污染的32号机械油(B组)润滑的Si_3N_4球的成组疲劳试验。结果表明超细颗粒污染影响陶瓷的特征寿命和寿命指数,使疲劳寿命L_(10)和L_(50)分别降低到30.7％和55.4％;分析了颗粒污杂对Si_3N_4陶瓷滚动接触疲劳失效机理及寿命的影响,指出颗粒污染引起疲劳寿命缩短的主要原因是进入接触区的硬质颗粒导致局部接触应力远远高于名义接触应力,从而加速疲劳裂纹的产生,颗粒污染使寿命指数减小的主要机理是疲劳以后超细颗粒进入疲劳裂纹开口后对裂纹开口处产生支撑作用,导致裂纹的扩展速率降低,从而延缓疲劳的加速过程。

In order to evaluate the rolling contact fatigue property and the ability of anti-contamination of Si3N4 ceramic when it is lubricated by clean oil (group A) and SiO2 debris contaminated oil (Wt 1%, group B), four ball fatigue tests were conducted on a four-ball fatigue tester under the nominal contact stress of 7.01 GPa, and the result showed that debris contamination had simultaneous effect on the characteristic life and the life exponent of Si3N4, which reduced the fatigue life of L10 and L50 by 30.7% and 55.4%. The effect of debris contamination on the forming mechanism of fatigue and the fatigue life of Si3N4 ceramic balls is analysed. It is concluded that the main reason for the reduced life of Si3N4 ceramic balls lubricated by debris contaminated oil is that the debris enters the contact area and makes the contact stress much higher than the nominal contact stress, which accelerates the forming of the fatigue crack.