PSI - Issue 18

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2019) 000–000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2019) 000–000

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 18 (2019) 287–292

25th International Conference on Fracture and Structural Integrity Predicting Fatigue Crack Initiation in 3D Structures with A DAPCRACK 3D Tintu David Joy*, Gunter Kullmer Institute of Applied Mechanics, Paderborn University, Pohlweg 47-49, Paderborn 33098, Germany 25th International Conference on Fracture and Structural Integrity Predicting Fatigue Crack Initiation in 3D Structures with A DAPCRACK 3D Tintu David Joy*, Gunter Kullmer Institute of Applied Mechanics, Paderborn University, Pohlweg 47-49, Paderborn 33098, Germany

Abstract Abstract

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. A DAPCRACK 3D 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. A DAPCRACK 3D 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 A DAPCRACK 3D uses for simulating the growth of the crack. This paper is an attempt to introduce a numerical procedure in A DAPCRACK 3D 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. 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. A DAPCRACK 3D 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. A DAPCRACK 3D 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 A DAPCRACK 3D uses for simulating the growth of the crack. This paper is an attempt to introduce a numerical procedure in A DAPCRACK 3D for automatic crack initiation in 3D structures. 3D odels 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. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo.

Keywords: Automatic crack initiation; crack initiation and crack propagation program, crack initiation lifetime Keywords: Automatic crack initiation; crack initiation and crack propagation program, crack initiation lifetime

* Corresponding author. Tel.: +49-5251-60-5339; fax: +49-5251-60-5322. E-mail address: joy@fam.upb.de * Corresponding author. Tel.: +49-5251-60-5339; fax: +49-5251-60-5322. E-mail address: joy@fam.upb.de

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. 2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo.

2452-3216  2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. 10.1016/j.prostr.2019.08.167