Cumulative Fatigue Damage in the Diesel Engines application

The development of a new design criterion was necessary to provide the application of the engine MWM TD229-4 in a new agricultural tractor.

The engine is a four stroke, Diesel cycle with four in line cylinders and it was applied to the tractor CNH TL75/85/95. The structural exigencies imposed to the tractor in a bench test demanded the study of a design criterion based on cumulative fatigue damage which utilized the Palmgren-Miner linear cumulative damage rule. This criterion was utilized in substitution of the current fatigue criterion by modified Goodman.

The experimental tests have known loads and cycles where the modified Goodman criterion does not present a good correlation because it is developed to stress base, which does not consider plastic strains.

The results obtained through Palmgren-Miner rule, in fatigue cumulative damage calculations, allowed to determine the engine structural components which needed to be modified to avoid crack opening during the experimental tests.