Evaluation of low cyclic thermal fatigue life and safety for diesel engine´s pistons

The axisymmetric temperature fields and cyclic elastic-plastic stress-strain fields and Mises´ equivalent stress-strain fields of 12V180 and 42-160 engines´ pistons were calculated by the program “ADINAT/ADINA”. The tests of thermal-mechanical and isothermal low-cycle fatigue at elevated temperatures were carried out with the cylindrical notched specimens according to the “start-stop” wave. The results of tests and calculations showed that the relationships between the equivalent strain ranges and fatigue lives accorded with the Manson-Coffin formula and were not affected by specimens´ shapes and sizes, at the same time, it was also verified that the relationships between the fatigue crack growth rates and equivalent J-integral ranges did not depend on specimens´ shapes and sizes. Finally, these results were applied to the pistons life prediction and safety evaluation and it was verified that the in-phase thermal-mechanical fatigue estimation was effective.