Transient dynamics analysis and fatigue life prediction of V type diesel engine block

Transient dynamics analysis of a V type heavy duty diesel engine block was carried out using the dynamic load data attained from the multi-body dynamics analysis of engine moving mechanisms. The stress-time history of the structure was gained by calculation of the block dynamic response under excitation condition, and it showed that stress varying magnitude at node in the block diaphragm was caused by the explosion exciting force of opposite side cylinder, and the stress distributions at symmetrical points in diaphragms exhibited inverse shape roughly. In consideration of the block material and the stress state, the critical plane method was used to predict fatigue life at several key points of the block. It is found that the fillet of the block scapular is liable to fatigue damage under typical tensile-compressive load. Bench tests show that there appears a fracture at left side of the second diaphragm after running 387 hours in the evaluating condition spectrum, just as indicated by the prediction.