Thermo-mechanical fatigue damage and failure of modern high performance diesel pistons

This study resulted from an engineering failure investigation related to diesel engine pi failures which occurred during a bench dynamometer engine durability test program The test programme aimed at evaluating the effects of various fuel types on the durable of fuel system components in passenger car diesel engines. A number of unexpected c. der head, turbocharger and piston failures were experienced during the course of the programme. This study focused on the cause of the piston failures experienced during the tests. Analyses of the fractured pistons revealed that thermo-mechanical fatigue initiative occurred as a result of primary silicon phase cracking and subsequent micro-crack for tion due to excessive thermo-mechanical loading. Progressive formations of such m cracks lead to flaws that were of sufficient magnitude to initiate propagation by high fatigue mechanisms. The investigation also revealed that the excessive therrno-mechanical piston loading caused by over-fuelling and a combination of elevated and poorly controlled post it cooler air temperature. There was no evidence to suggest that the failures were relation the test fuel formulations. (C) 2011 Elsevier Ltd. All rights reserved.