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采用化学成分分析、组织观察和硬度测试等分析方法,对铁路机车用51CrV4弹簧进行失效分析。结果表明:断簧的化学成分、非金属夹杂物级别和金相显微组织均符合技术规范要求。但弹簧的强度、断口处硬度及疲劳源附近残余压应力值偏低,且存在全脱碳层。此外,弹簧支撑圈和工作圈间因反复接触产生的压痕破坏了表面完整性,易于引发应力集中而导致弹簧疲劳裂纹萌生。在这几个因素综合作用下,弹簧在高频交变应力作用下产生裂纹导致早期疲劳断裂失效。
The failure analysis of 51CrV4 spring for railway locomotives was carried out by chemical composition analysis, microstructure observation and hardness test. The results show that the chemical composition, non-metallic inclusions and metallurgical microstructure of the broken spring all meet the technical specifications. However, the strength of the spring, the hardness at the fracture site and the residual compressive stress near the fatigue source are low, and the full decarburized layer exists. In addition, the indentation caused by repeated contact between the spring support ring and the work ring destroys the surface integrity and tends to cause stress concentration and lead to spring fatigue crack initiation. Under the combined action of these several factors, the spring cracks under the action of alternating high-frequency alternating stress and leads to the failure of early fatigue fracture.