PSI - Issue 18

Tintu David Joy et al. / Procedia Structural Integrity 18 (2019) 287–292 T. D. Joy, G. Kullmer./ Structural Integrity Procedia 00 (2019) 000–000

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1. Introduction

The failure of structures that are subjected to cyclic loading has been a problem for many years. One of the main causes of this failure is fatigue crack growth which starts with a micro crack formed in the material because of reasons such as material imperfections, overloading etc. These cracks are formed due to the localized plastic deformation during the cyclic loading of components, see Chan (2010). The crack initiation in components with pores or inclusions are faster as compared to defect-free components. Some studies show that at least half of the structures in the mechanical field fail due to fatigue see Sangid (2013). The aftermath of the damages resulting from fatigue cracks are costly and irreversible. There are plenty of real world applications where fatigue crack growth has caused disastrous consequences. Some of the examples are explained in Richard et al. (2013). These examples exhibit the importance of fracture mechanics in designing and creating a safer structure. The lifetime of a structure is a combination of the lifetime required to initiate a crack and the lifetime needed to propagate the crack. There are various simulation programs available to simulate crack growth which calculate only the crack growth lifetime. A DAPCRACK 3D is one such 3D automatic crack growth simulation software developed in the Institute of Applied Mechanics at Paderborn University. It is generally used for simulating crack propagation and predicting crack propagation lifetime, see Schöllmann et al. (2003). Some other programs that are used for crack growth simulation are F RANC 3D, Ingraffea et al. (2003) and Zencrack, Hou et al. (2001). This paper describes the newly implemented function in A DAPCRACK 3D that automatically initiates a crack in a 3D structure. 2. Simulation Software A DAPCRACK 3D A DAPCRACK 3D is a software based on finite element method (FEM) for simulating mixed-mode loading situations. The current schematic structure of the software is displayed in Fig.1. In this architecture of A DAPCRACK 3D the two modules N ETADAPT 3D and N ETCRACK 3D are used exclusively for crack growth simulation. N ETADAPT 3D performs the FE-Mesh adaptation required for the crack growth simulation and N ETCRACK 3D carries out the fracture mechanical evaluation. The FE-Model and the initial technical crack surface are generated in A BAQUS TM and are submitted to the module N ETADAPT 3D. N ETADAPT 3D inserts the crack surface in the input model and creates two new models: a global model with the crack and a submodel which is generated only along the crack front.

Fig. 1. Structure of A DAPCRACK 3D