Experimental and Predicted Crack Paths for Al-2024-T351 Under Mixed-Mode I/II Fatigue

Abstract

The aerospace industry has experience with a range of structural failures, oftentimes due to fatigue cracks in aircraft fuselage components that are exposed to relatively high stress levels during cyclic loading effects that lead to fatigue crack initiation at material defects and near stress concentrations. These aircraft components are under complex stress states. In this study, mixed mode I/II fatigue experiments and simulations are performed for an Arcan fixture and a 6.35 mm thick Al-2024-T351 specimen, a popular aerospace alloy. Experiments were performed for Arcan loading angles that gave rise to a range of Mode I/II crack tip conditions from 0 Ä KII/KI Ä 1. Measurements include the crack paths, loading cycles, and maximum and minimum loads for each loading angle. Simulations were performed using three-dimensional finite element analysis (3D-FEA) with 10-noded tetrahedral elements via the custom in-house FEA code, CRACK3D. While modeling the entire fixture-specimen geometry, a modified version of the virtual crack closure technique (VCCT) with automatic crack tip re-meshing and a maximum circumferential stress criterion was used to predict the direction of crack growth. Results indicate excellent agreement between experiments and simulations for the measured crack paths during the first several millimeters of crack extension.

Comprehensive Comparisons of Two-and Three-Dimensional Numerical Estimation of Stress Intensity Factors and Crack Propagation in Linear Elastic Analysis

“…The remaining space between is filled with additional elements Insufficiently robust mesh modification algorithms can cause premature termination of a progressive fracture simulation. [20]. Merely a geometric updating of a crack path during each simulation step because cracks are not represented explicitly in an adaptive mesh.…”

Finite element-based model for crack propagation in linear elastic materials

“…The remaining space between is filled with additional elements. Insufficiently robust mesh modification algorithms can cause premature termination of a progressive fracture simulation (Miller et al 2015). Only a geometric description of a crack path needs to be updated during each simulation step because cracks are not represented explicitly in an adaptive mesh.…”

Mode-II Fatigue Crack Growth Model from Shear-Type Low Cycle Fatigue Properties

“…The shear-type fatigue crack growth characteristics attract many researchers' attention. For mode-II and even mode-mixed cracks, meanwhile, a few investigators have reported experimental data in the propagation rate versus the corresponding to SIF range [3][4][5][6][7][8][9]. A number of geometric configurations for mode-II crack have been used in the test for FCG rate.…”