This study investigates the fatigue failure behavior of coil compression springs and various influencing factors. The intrinsic and induced causes of fatigue failure in metro steel springs were revealed by systematic tests. Macroscopic observation and metallographic analysis of the fracture indicate that decarburization, which leads to a reduction in the fatigue limit of the material, was the essential cause of the failure. The resonance of the steel spring caused by rail corrugation leads to an increase in dynamic stress, which is the induced cause of the failure. The combined effect of the two factors promoted the failure of the springs. In addition, decarburization led to a decrease in the microhardness of the spring surface from 462 HV to 151 HV and a decrease in fatigue life from over 3.6 million kilometers to 521,000 km (with the decarburization depth of 0.3 mm). The effects of different stress ratios and decarburization depths on the equivalent shear stress (ESS) were comprehensively investigated. The ESS of steel springs with decarburization and different stress ratios were calculated according to the FKM Guideline and the EN 17149 standard. The ESS decreases from 188 MPa to 77 MPa at a stress ratio of = 0, and from 168 MPa to 76 MPa at a stress ratio of = 0.5. If the effects of rail corrugation are not taken into account, the ESS meets the design life requirements. Furthermore, the effects of different rail fastener types and track structures on the dynamic stress were compared. It was found that the double-layer nonlinear vibration damping fasteners can significantly improve steel spring vibration. Finally, improvement measures and recommendations are proposed based on the root causes of failure and the influencing factors.

中文翻译：

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螺旋弹簧疲劳耐久性及影响因素研究——以地铁车辆为例


本研究研究了螺旋压缩弹簧的疲劳失效行为以及各种影响因素。通过系统试验揭示了地铁钢弹簧疲劳失效的内在原因和诱发原因。断口宏观观察和金相分析表明，脱碳导致材料疲劳极限降低，是失效的根本原因。钢轨波磨引起的钢弹簧共振导致动应力增大，是诱发失效的原因。两个因素的共同作用促进了弹簧的失效。此外，脱碳导致弹簧表面显微硬度从462 HV下降至151 HV，疲劳寿命从超过360万公里下降至52.1万公里（脱碳深度为0.3毫米）。综合研究了不同应力比和脱碳深度对等效剪切应力（ESS）的影响。根据FKM指南和EN 17149标准计算脱碳和不同应力比的钢弹簧的ESS。当应力比 = 0 时，ESS 从 188 MPa 降至 77 MPa；当应力比 = 0.5 时，ESS 从 168 MPa 降至 76 MPa。如果不考虑钢轨波磨的影响，ESS满足设计寿命要求。此外，还比较了不同扣件类型和轨道结构对动应力的影响。结果发现，双层非线性减振紧固件可以显着改善钢弹簧振动。最后，根据失败的根源和影响因素，提出改进措施和建议。