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利用超声疲劳低-高应力两步变幅加载技术研究了JIS SUJ2高强轴承钢疲劳断口上GBF(granular bright facet)内裂纹萌生与扩展规律。结果表明,随外加应力幅增加GBF尺寸减小,固定应力幅下的GBF尺寸为恒定值,与夹杂物尺寸无关;且在固定应力幅下,N f∝A槡inc-8,疲劳寿命N f随着夹杂物尺寸的增加而降低。研究表明,GBF形成于疲劳初期(在105周次左右,相应于小于1%的总寿命),随循环周次的增加,GBF尺寸基本不增加,直至接近最终疲劳寿命时(超过90%总寿命)GBF裂纹快速扩展直到最终尺寸。
The initiation and propagation of cracks in GBF (granular bright facet) on the fatigue fracture surface of JIS SUJ2 high-strength bearing steel were studied by ultrasonic fatigue with low-high-stress two-step luffing loading. The results show that with the increase of applied stress amplitude, the size of GBF decreases and the size of GBF under constant stress amplitude is constant, which is independent of the size of inclusions. Under constant stress amplitude, N fαA 槡 inc-8, fatigue life N f As inclusion size decreases. Studies have shown that GBF is formed at the initial stage of fatigue (around 105 weeks, corresponding to a total life of less than 1%), with the increase in the number of cycles, the GBF size does not increase substantially until near final fatigue life (over 90% ) GBF crack quickly expands to the final size.