Stress intensity factor and the crack shape changes in turn affect the crack propagation life

Since the position of welded structures there is a high weld toe nonlinear stress distribution, the weld toe surface near the crack tip stress field will inevitably be affected. Meanwhile, due to the nonlinear stress crack surface makes the existence of the peak stress at the end increases, the speed surface cracks extended along the longitudinal  Valve manifolds  of the crack, changing the shape of the crack propagation. Near the crack tip stress field variations and changes will affect the shape of the crack surface crack stress intensity factor of size. Stress  Instrument valve manifolds  and the crack shape changes in turn affect the crack propagation life. Therefore, the discussion of non-linear distribution of stress on the surface crack stress  High pressure needle valve , crack shape and crack propagation life of welded structures for an accurate calculation of fatigue life is important. In this paper, butt weld toe surface crack crack propagation behavior of a large number of finite element analysis. Analysis assumes that there is no residual stress, porosity, incomplete penetration, dislocation, undercut other welding defects, the study focused on non-linear distribution of stress at the weld toe surface crack extension.