Fatigue-Crack Growth Rate Testing at High Stress Intensities

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Abstract
Controlled load fatigue-crack growth rate tests are conducted using compact specimens of various widths between 1 and 10 in. Two engineering metals are tested: A533B pressure vessel steel and A469 alloy rotor steel. In these high-toughness materials, the upper limit of data interpretation based on linear-elastic analysis appears to be controlled by fully plastic limit load behavior. This resulted in the largest specimens yielding data at higher stress intensities than can be investigated in the smaller specimens usually employed in fatigue-crack growth rate testing. Test methods and limitations relative to plasticity are discussed, and it is recommended that deflections be monitored during load controlled testing. Some observations also are made concerning the relevance of static fracture toughness to failure following fatigue-crack growth.