Abstract
The main objective of this work was to present a numerical modelling of crack growth path in linear elastic materials under mixed-mode loadings, as well as to study the effect of presence of a hole on fatigue crack propagation and fatigue life in a modified compact tension specimen under constant amplitude loading condition. The ANSYS Mechanical APDL 19.2 is implemented for accurate prediction of the crack propagation paths and the associated fatigue life under constant amplitude loading conditions using a new feature in ANSYS which is the smart crack growth technique. The Paris law model has been employed for the evaluation of the mixed-mode fatigue life for the modified compact tension specimen (MCTS) with different configuration of MCTS under the linear elastic fracture mechanics (LEFM) assumption. The approach involves accurate evaluation of stress intensity factors (SIFs), path of crack growth and a fatigue life evaluation through an incremental crack extension analysis. Fatigue crack growth results indicate that the fatigue crack has always been attracted to the hole, so either it can only curve its path and propagate towards the hole, or it can only float from the hole and grow further once the hole has been lost. In terms of trajectories of crack propagation under mixed-mode load conditions, the results of this study are validated with several crack propagation experiments published in literature showing the similar observations. Accurate results of the predicted fatigue life were achieved compared to the two-dimensional data performed by other researchers.
Highlights
The assessment of fatigue crack growth (FCG) and the fracture toughness of materials is commonly performed using the CT specimen (ASTM 2013)
The results of XFEM analysis were compared with experimental data for different configurations of modified compact tension specimen (MCTS) depending on the third hole position from the crack tip with excellent agreement for all cases
The structure and configuration of the specimen play a crucial role in the acquisition of higher values of stress intensity factors (SIFs) in mixed modes which demonstrated the crack growth trajectory
Summary
The assessment of FCG and the fracture toughness of materials is commonly performed using the CT specimen (ASTM 2013). In fatigue crack growth (FCG) studies, the specimen geometry typically investigates the ratio of minimum stress to maximum stress (R) [1,2]. The compact tension CT specimen has the beneficial effects of a relatively smaller material volume and comparatively less stress for FCG evaluation [3]. Practical structures are almost subjected to many loading types like tension, shear and torsion resulting in a mixed-mode interaction. The stress state ahead of a crack is commonly based on mixed-mode I/II type of interactions, indicating the magnitude of the stresses at the crack tip. Cracks can grow in the skin of aircraft fuselages and may subject to mixed-mode type of loading. Fatigue crack analysis is essential in different fields of engineering since fatigue cracks are one among the main sources of catastrophic fracture failures
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