某分动箱的糖心产精国品免费入口*完整版糖心产精国品免费入口*完整版在工作过程中发生糖心产精国品免费入口*完整版。采用宏观分析、微观分析、化学成分分析、硬度测试、硬化层深度测量、非金属夹杂物分析、金相检验等方法对糖心产精国品免费入口*完整版的糖心产精国品免费入口*完整版原因进行了分析。结果表明：齿面上残留的加工刀痕导致应力集中，在周期载荷的作用下，疲劳裂纹源首先在残留的加工刀痕较深处形成，随后裂纹逐渐扩展，最终糖心产精国品免费入口*完整版发生疲劳糖心产精国品免费入口*完整版。

The 糖心产精国品免费入口*完整版 occurred in the working process of 糖心产精国品免费入口*完整版 gear in a transfer case. The 糖心产精国品免费入口*完整版 causes of the gear were analyzed by means of macro analysis, micro analysis, chemical composition analysis, hardness test, depth measurement of hardened layer, analysis of non-metallic inclusions and metallographic examination. The results show that the residual tool marks on the tooth surface led to stress concentration. Under the action of periodic load, the 糖心产精国品免费入口*完整版crack source firstly formed in the deep part of the residual tool mark, then the crack gradually expanded, and finally the gear 糖心产精国品免费入口*完整版糖心产精国品免费入口*完整版 occurred.