Effects of Initial Crack Defect on Fatigue Crack Growth of Camshaft for Nuclear Emergency Diesel Engine

Abstract

In this paper, the finite element analysis model of camshaft for nuclear emergency diesel engine with initial crack defect is established based on ABAQUS finite element analysis software. The effects of initial crack defect parameters on crack tip stress intensity factor are studied by a working condition discretization method. The numerical results show that the crack tip stress intensity factors of transverse crack and longitudinal crack are quite different in a load cycle of camshaft. The crack tip stress intensity factors of transverse crack fluctuate greatly, and the crack tip stress intensity factor range is much larger than that of longitudinal crack, which indicates that the fatigue fracture risk of transverse crack on the camshaft journal is higher. With the increase of initial crack depth from 1 mm to 4 mm, the crack tip stress intensity factor range increases from 410.84 MPa·mm1/2 to 720.24 MPa·mm1/2 by 75.3%, which indicates that the increase of initial crack depth can lead to a significant increase of the fatigue fracture risk. As the initial crack defect moves away from the cam, the maximum of the crack tip stress intensity factor initially increases and then decreases after reaching a maximum value. When the initial crack is 3 mm away from the end face of the cam, the crack tip stress intensity factor range is the largest (843.98 MPa·mm1/2), which indicates that the fatigue fracture risk of transverse crack at this position is the highest. The research results obtained in this paper may provide some reference for the fracture assessment and reliability analysis of camshaft for nuclear emergency diesel engine.