某航空用扭转弹簧失效分析(英文)

某型扭转弹簧零件主要用于航空机构中,在装配过程中出现裂纹和发生断裂。通过视频显微镜、扫描电镜、金相显微镜等分析方法,对断裂弹簧裂纹、断口特征及其附近损伤形貌进行了宏、微观观察和覆盖物的能谱分析。在试验结果和数据的基础上,结合加工工艺综合分析失效的性质和原因。金相组织检查未发现材质异常,失效与材质无关。弹簧裂纹和断裂都起始于内表面,因此裂纹的萌生发生在弹簧绕制后镀镉前。裂纹张开方向与弹簧内表面的残余拉应力方向一致,而且绕制后、镀镉前接触氢介质。弹簧失效的原因是残余拉应力和氢共同作用下发生氢致延迟开裂。

Failure Analysis of Aviation Torsional Springs

Cracks and fractures occur during the assembly process to a type of torsional springs used in the aviation mechanism. Besides visual examination, other experimental techniques used for the investigation are: 1) fracture characteristics, damage morphology and fractography by scanning electron microscopy (SEM), 2) spectrum analysis of covering, 3) metallographic observation of cracks and 4) hydrogen content testing. The results are obtained through the analysis of manufacture process and experimental data. Since no changes of microstructure are found, failures are irrelevant to the material. The cracks and fractures initiate on the inner surface, cracks initiate before the cadmium plating and after the winding. No obvious stress corrosion cracks are found near the crack source region. The opening direction of cracks is consistent with the residual tensile stress of the spring inner surface, and the springs are easy to contact hydrogen media between the spring winding and the cadmium plating. The cracks are caused by hydrogen-induced delayed cracking under the action of the residual tensile stress and hydrogen.