Development of a Crack Growth Rate Test for Quality Control
Final technical rept. Apr 1975-Jun 1977
DEL WEST ASSOCIATES INC WOODLAND HILLS CA
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A test method has been developed which reliably and inexpensively provides the fatigue crack growth rate of a material sample at any given stress intensity level. The method employs a notched three point bend bar, typically 4 i4 in. x 12 in. x 14 in., in a controlled displacement amplitude test mode. The specimentest system is configured such that a constant stress intensity amplitude exists over the central region of the test specimen. Due to the unique attributes of a displacement controlled constant K test specimen, no visual or COD measurements of crack length are required for the crack growth rate measurement. An autographic record of load amplitude versus cycles exhibits a straight line portion, the slope of which provides a measurement of the central region crack growth rate. The test is simple enough so that a well trained quality control laboratory technician can perform it employing about one hour of his time to set it up, run the test and analyze the result. Capability has been demonstrated by comparing the results of 137 tests using the newly developed method with crack growth rate data generated employing compact tension geometry samples.
- Metallurgy and Metallography
- Test Facilities, Equipment and Methods