某航空发动机的燃油冷却机匣在经历高低温试验后发现筒体外缠绕的冷却油管多处爆裂, 通过对爆裂油管宏观及断口形貌的观察、油管材料的金相检验、硬度测试等对其开裂原因进行了分析。结果表明: 油管表面有大量的平行于管道轴向的加工沟槽, 开裂即起源于此应力集中处; 其开裂性质为韧性开裂;气密试验后管道内局部有残留水, 在高低温试验的低温阶段, 水转化为冰时产生高的膨胀应力, 而管道本身在低温阶段则产生高收缩应力; 在反复的冷热试验中局部不断产生变形、硬化、塑性减薄;当低温试验阶段二者的叠加应力超出了材料的强度时管道发生爆裂。

There were many cracks in the cooling oil tubes wrapping the cyclinder of the fuel oil cooling case for an areo-engine after high and low temperature testing. The fracture reasons were analyzed through macroscopic observation and fracture observation of the cracked oil tubes, hardness test and metallography examination for tube material. The results show that the cracks originated from the stress concentration of scathing grooves parallel to the tube axis on the surface of oil tubes. The fracture of the tubes was toughness cracking. Some water remained in part of the tubes during air tightness test. Residual water turning into ice can produce high expansion stress in low temperature zone during high and low temperature testing; meanwhile the tubes in the low temperature stage can produce high shrinkage stress. The repetitive high and low temperature tests led the deformation, hardening and plastical thinning of the tube. And finally the tube ruptured when the superimposed stress exceeded the strength of the material in the low temperature stage.