CRACK GROWTH OF CORNER CRACKS AT OFFSET HOLES: EXPERIMENTAL VALIDATION OF PREDICTIONS FROM COMMERCIAL CODES

摘要

The stress intensity solution for corner cracks emanating from an offset hole is the most commonly used stress intensity solution in the aircraft industry. During an evaluation program of three widely used commercial crack growth codes (CRACKS, AFGROW, NASGRO), significant differences in crack growth predictions for the case of corner cracks at offset holes were found. A limited validation test program was performed by Cessna Aircraft Company consisting of 20 specimens manufactured from two different aerospace aluminum alloys with corner cracks at offset holes subjected to constant amplitude loading at two R-ratios. The developers of NASGRO and AFGROW both had revised their codes after the preliminary study to improve the accuracy for offset hole configurations and the experimental crack growth lives are compared with predictions from current versions of all three codes. In general all three codes resulted in adequate crack growth life predictions, with no one code demonstrating consistently superior accuracy.