Issue 35

H. Dündar et alii, Frattura ed Integrità Strutturale, 35 (2016) 360-367; DOI: 10.3221/IGF-ESIS.35.41 360 Focussed on Crack Paths Multiple and non-planar crack propagation analyses in thin structures using FCPAS H. Dündar, A. O. Ayhan Department of Mechanical Engineering, Sakarya University, 54187, Sakarya, TURKEY, A BSTRACT . In this study, multiple and non-planar crack propagation analyses are performed using Fracture and Crack Propagation Analysis System (FCPAS). In an effort to apply and validate FCPAS procedures for multiple and non-planar crack propagation analyses, various problems are solved and the results are compared with data available in the literature. The method makes use of finite elements, specifically three-dimensional enriched elements to compute stress intensity factors (SIFs) without special meshing requirements. A fatigue crack propagation criterion, such as Paris-Erdoğan equation, is also used along with stress intensity factors to conduct the simulation. Finite element models are generated within ANSYS™ software, converted into and solved in FRAC3D program, which employs enriched crack tip elements. Having computed the SIFs for a given crack growth increment and using a growth criterion, the next incremental crack path is predicted and the fracture model is updated to reflect the non-planar crack growth. This procedure is repeated until cracks reach a desired length or when SIFs exceed the fracture toughness of the material. It is shown that FCPAS results are in good agreement with literature data in terms of SIFs, crack paths and crack growth life of the structure. Thus, accuracy and reliability of FCPAS software for multiple and non-planar crack propagation in thin structures is proven. K EYWORDS . Fracture; Nonplanar Crack Growth; Crack Propagation. I NTRODUCTION lthough in-plane crack propagation under mode-I loading conditions is very common for machinery parts and structures and is still a popular research subject, some parts can fail under mixed mode loading, causing nonplanar crack surface. This type of crack propagation can occur under mixed mode loading conditions or when crack surface is not perpendicular to an axial load. Under mixed mode conditions, multiple cracks growing in a nonplanar manner can even be more critical for the structure due to interaction effects. Cracks can accelerate each other, coalesce or change direction due to the interaction effects. This situations can be seen in thin walled structures such as sheet or integral panels of aircrafts or engine parts that are subjected to high temperatures. Other examples can also be given in applications in the areas of transportation, energy and aviation. Therefore, accurate prediction of nonplanar crack propagation in machine parts or structures is very important to assure safety, efficiency and reliability of some engineering structures. In the literature, there are several numerical and experimental studies that deal with fracture and propagation analyses of multiple cracks and nonplanar crack growth. One of the numerical studies is by Wessel [1]. In that study, Wessel A