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L207E型柴油机活塞的损坏率是比较高的,必须引起有关方面的重视。对一些机务段调查的结果表明,现用活塞在机车运行七万公里左右,在活塞内四个螺柱座与活塞筒壁连接的圆弧处出现裂纹;严重时,裂纹贯穿连通,使活塞的头部与裙部分离,造成连杆和机体被打坏、曲轴箱爆炸等机破事故,威胁列车的安全运行。此外,在活塞顶部还出现网状热蚀裂纹,在活塞螺柱座孔出现径向、横向和垂向裂纹。经统计,1971～1978年活塞损坏情况列于下表。一、产生裂纹的原因上述三种裂纹的产生,都是活塞受到热应力和机械应力综合作用的结果。但每一种裂纹的产生与发展,又有它各自的主要因素。 (一)活塞顶中部的网状裂纹活塞在高温高压燃气的冲刷下工作,活
L207E diesel engine piston damage rate is relatively high, we must draw the attention of the parties concerned. The investigation results of some locomotive depots show that the existing piston runs around 70,000 km on the locomotive and cracks occur on the circular arc where the four stud seats in the piston are connected with the piston cylinder wall. In severe cases, the crack penetrates through to make the piston’s Head and skirt separated, resulting in connecting rod and the body was broken, crankcase explosion and other machine crash, threatening the safe operation of the train. In addition, mesh-like hot-corrosion cracking also occurs at the top of the piston and radial, lateral and vertical cracks appear in the piston-stud bore. According to the statistics, the piston damage from 1971 to 1978 is listed in the following table. First, the cause of the crack Crack generation of the above three are the result of the combined effect of thermal stress and mechanical stress on the piston. However, the occurrence and development of every kind of crack have their own major factors. (A) the top of the piston mesh crack piston in the high temperature and pressure gas under the erosion of work, live