The Numerical Simulation Of Fatigue Crack Growth Of Structure

This paper made an investigation on the method of numerical simulation of fatigue crack growth, Meanwhile, combining the two degree of freedom model the author calculated the crackle stress intensity factors and fatigue growth of crack increment, consequently realized the technology for fatigue crack growth.1.Owing to the existence of the stress singularities on the crack tip, stress intensity factors of plate surface crack are calculated by three-dimensional finite element method, and 3-D prismatic quarter point 20-node isoperimetric degenerate paradoxical elements are used for the region near the crack tip. This paper discusses the ratio of the length of 1st element (L)to crack depth(a) of the crack front, the effect which the rings of element (R) and every ring of element mesh density(m) round the crack front, on the calculated results and the representation of the stress intensity factors by dimensionless shape factors(Y), which induces that the results are in the proximity of the calculated results by Newman-Raju formula.2. In order to prove up expansion rule of 3-D surface crack under fatigue load ulteriorly, this paper presented the theoretical derivation and finite element calculation the shape changes of three-dimensional surface cracks under constant amplitude fatigue in tension loading,, then acquired an effective method to deduce the crackle shape during the process of crack growth.3. In practical engineering, mixed-mode fractures of material are commonplace. So the analysis of mixed-mode crack is of both theoretical importance and practical value. This paper simulate crack propagation path on mode â… -â…¡ compound load by Ansys FE Software.4.Calculating the surface crackle stress intensity factors of welded structure by using crackle object FE model in this paper, Investigation on the effect on stress intensity factors of welded strrcture geometrical parameter is significance for enhancing fatigue intensity of welded structure.