在生产运行中WK－4挖掘机的行走机构容易发生主动轮或中间轴断裂事故．其中间轴断型的原因有以下几种：（1）应力集中检查断裂的中间轴发现，断裂均产生在花键退刀槽处（尺寸为100mm），即轴的最小截面处。并且，有时花键根部无退刀相或退刀槽过小，致使花键根部应力集中；（2 WK-4 excavators in the production operation of the running gear prone to the driving wheel or the intermediate shaft rupture accident. The reasons for the middle shaft breakage are the following: (1) stress concentration inspection found that the middle shaft fracture, breakage occurred in the spline undercut groove (size 100mm), the minimum cross-section of the shaft. And sometimes spline roots without retraction phase or undercut groove is too small, resulting in spline root stress concentration; (2