某款发动机贴合试验活塞裙部开裂问题解析

Analysis on Cracking of Piston Skirt in Fitting Test of an Engine

某款发动机活塞贴合试验完成后,拆机时发现第3缸活塞主推力侧裙部出现裂纹,裂纹分布在止口到大点位置。经分析,原因为活塞内腔为非对称结构,加工外圆面时活塞反放,活塞头部压紧工装下压时,内腔支撑块与活塞干涉,产生挤压缺陷,导致局部应力集中,在发动机运转中出现裂纹。通过对活塞加工进行防错,解决了因挤压缺陷而产生裂纹的问题。

After the piston fitting test of a certain engine is completed, when the engine is disassembled, it is found that there are cracks on the skirt of the main thrust side of the third cylinder piston, and the cracks are distributed from the lip to the large point. The analysis shows that the reason is that the inner cavity of the piston is of asymmetric structure. When the outer circular surface is processed, the piston is reversed. When the piston head is pressed down by the tool, the inner cavity support block interferes with the piston. As a result, extrusion defects occur, resulting in localized stress concentrations and cracks during engine operation. The problem of cracks due to extrusion defects is solved by adopting error proofing for piston machining.