钎头套筒疲劳断裂失效分析

Failure analysis of fatigue fracture of drill sleeve

运用金相、SEM观察等试验手段,从断口形貌、夹杂物、显微组织和硬度方面对两个45CrNiMoV钢钎头套筒断裂原因进行了对比分析。结果表明,疲劳源区平整光滑,主要是拉压应力起主导作用,疲劳扩展断裂面是约呈45°方向的斜面,剪切应力在起主导作用,最终由于材料承载面积减小,材料瞬时断裂。钎头断裂源位于套筒最薄处。疲劳裂纹扩展阶段占总的疲劳寿命期的比例较小,提高疲劳裂纹扩展的门槛值,减少疲劳源的产生才能使钎头获得高疲劳寿命。

Failure cause of the 45CrNiMoV steel drill sleeve was investigated by optical microscope and scanning electron microscope , and the comparative analysis was carried out on the fatigue fracture morphology , inclusions , microstructure and hardness .The results show that the fatigue source is subjected to predominantly normal stresses , causing crack propagation in the perpendicular direction .The fatigue cracking propagation region is subjected to major shear stresses , causing crack propagation in a 45°plane.Eventually due to the material loaded area is reduced , the drill sleeve cracks quickly .The fatigue source is initiated at the thinner sleeve .The proportion of fatigue propagation stage is smaller in the total fatigue life , thus high fatigue life of the drill sleeve can be obtained by increasing fatigue crack growth threshold and decreasing fatigue crack initiation .