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This paper presents the results of an experimental and predictive round robin conducted by the American Society for Testing and Materials (ASTM) Task Group E24.06.02 on Application of Fracture Analysis Methods. The objective of the round robin was to verify whether fracture analysis methods currently used can or cannot predict failure loads on complex structural components containing cracks. Fracture results from tests on compact specimens were used to make these predictions. Results of fracture tests conducted on various-size compact specimens made of 7075-T651 aluminum alloy, 2024-T351 aluminum alloy, and 304 stainless steel were supplied as baseline data to 18 participants. These participants used 13 different fracture analysis methods to predict failure loads on other compact specimens, middle-crack tension (formerly center-crack tension) specimens, and structurally configured specimens. The structurally configured specimen, containing three circular holes with a crack emanating from one of the holes, was subjected to tensile loading.
The accuracy of the prediction methods was judged by the variations in the ratio of predicted-to-experimental failure loads, and the prediction methods were ranked in order of minimum standard error. The range of applicability of the prediction methods was also considered in assessing their usefulness. For 7075-T651 aluminum alloy, the best methods (predictions within ±20% of experimental failure loads) were: the effective KR-curve, the critical crack-tip-opening displacement (CTOD) criterion using a finite-element analysis, and the KR-curve with the Dugdale model. For the 2024-T351 aluminum alloy, the best methods were: the Two-Parameter Fracture Criterion (TPFC), the CTOD criterion using the finite-element analysis, the KR-curve with the Dugdale model, the Deformation Plasticity Failure Assessment Diagram (DPFAD), and the effective KR-curve with a limit-load condition. For 304 stainless steel, the best methods were: limit-load (or plastic collapse) analyses, the CTOD criterion using the finite-element analysis, the TPFC, and the DPFAD. The failure loads were unknown to all participants except the author, who used both the TPFC and the CTOD criterion (finite-element analysis).
fracture (materials), elastic-plastic fracture, ductile fracture, tearing, stable crack growth, instability, stress-intensity factor, finite-element method, Dugdale model, J-integral, fracture criteria, elasticity, plasticity
Senior scientist, NASA Langley Research Center, Hampton, VA