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渭阳柴油机厂引进的联邦德国风冷发动机曾多次发生因连杆螺栓或平衡块螺栓断裂而引起整个发动机报废事故,经扫描电镜分析,证实螺栓均为穿晶疲劳断裂,连杆螺栓为首先破坏件。疲劳源于螺纹根部应力集中区,并承受了较大的动应力。动应力来源主要是预紧力不足。连杆螺栓的断裂导致平衡块螺栓过载,继而发生了低周疲劳断裂,螺栓材料的冷金质量较差,但不是断裂的直接原因,本文还讨论了预紧力对紧固螺栓疲劳强度的影响。
The introduction of the German federal air-cooled diesel engine plant in Germany has repeatedly occurred due to the connecting rod bolts or balance bolt fracture caused the entire engine scrapped the accident by scanning electron microscopy, confirmed that the bolts are transgranular fatigue fracture, connecting rod bolt first Destruction pieces. Fatigue originates from the stress concentration zone in the root of the thread and suffers from greater dynamic stress. The main source of dynamic stress is insufficient preload. The breakage of the connecting rod bolt leads to the overloading of the balancing block bolt, followed by the low cycle fatigue fracture, the poor cold-quality of the bolt material, but not the direct cause of the fracture. The paper also discusses the effect of the pre-tightening force on the fatigue strength of the fastening bolt .