240/275系列柴油机新结构钢顶铝裙活塞的研制

铁路提速、重载后，240／275系列柴油机钢顶铝裙组合活塞出现了裙裂损、环槽磨损过快等严重质量问题。为提高该活塞的寿命，通过一系列研究和试验，查明活塞失效的主要原因是由于活塞结构不舍理局部应力集中而导致严重的活塞裙疲劳破坏。同时还给出了活塞环槽磨损过快的四个主要因素。通过结合仿真分析的一系列试验，设计了一种新结构活塞。目前，大量的新结构活塞已经安全运行60万km以上。

Development of a New Structure Piston with Steel Crown and Aluminum Skirt for 240/275 Series Diesel Engines

In order to deal with the severe cracks created in the piston skirt and the rapid over-wear happened in piston ring grooves of some pistons, which is composted of a steel crown and an aluminum skirt, in 240/275 series diesel engines, and to increase its working life, the conclusion about piston failures has been found out by a series of researching and testing. First, the failure mode is fatigue damage, which is caused by the stress concentration due to unreasonable structure. Second, the reason of rapid over-wear in piston ring grooves is caused by 4 main factors. Based on the analysis above and a series of tests combined with FEA simulation, a new design scheme of this kind of piston has been obtained. Up to now, a lot of these new pistons have safely run over 600,000 km.