Predicting Fatigue Crack Initiation in 3D Structures with ADAPCRACK3D

The total service life of structures or components that have been under cyclic loading is the combination of load cycles required to initiate a crack or multiple cracks and the load cycles needed to propagate those cracks. Thus prediction of fatigue crack initiation as well as fatigue crack growth is very important in determining the lifetime of structures. Various simulation programs are available to foresee the fatigue crack growth and to calculate load cycles required for crack growth. ADAPCRACK3D is one such automatic crack growth simulation program which uses finite element method to simulate crack growth behavior in 3D structures. It also calculates the crack path, crack growth rate and the load cycles needed for the crack growth up until failure of the structure. ADAPCRACK3D generally uses mechanical and thermal loading conditions. Until now the software only calculates load cycles required for propagating an already initiated crack. Thus the user provided FE-Model contains the location and shape of the initial crack which ADAPCRACK3D uses for simulating the growth of the crack. This paper is an attempt to introduce a numerical procedure in ADAPCRACK3D for automatic crack initiation in 3D structures. 3D models are created with necessary loading conditions and without the initial technical crack. Simulations are performed on these models for finding the stress tensor and maximum principal stresses in the structure. The software then uses this information to calculate the position and the surface where a crack is most likely to occur. The load cycles required to initiate the crack are also calculated using the Smith Watson Topper damage parameter. The automatically initiated crack is then used for a crack growth simulation, thereby determining the total lifetime of structure. 2019 The Authors. Published by Elsevier B.V.