What Does Fatigue Crack Growth Testing Mean?
Fatigue crack growth testing is a procedure used to determine the rate at which a crack in a specimen will grow under specified, time-varying loading conditions. The test involves initiating a flaw in the specimen, subjecting the specimen to loading, and employing various crack measuring techniques such as DC potential drop, compliance changes and visual measurements.
Fatigue crack growth testing may also be known as crack propagation testing or da/dN testing.
Corrosionpedia Explains Fatigue Crack Growth Testing
Fatigue crack growth testing is used to evaluate the safety and reliability of various materials by subjecting them to repeated loading and unloading cycles.
Fatigue crack growth testing is usually conducted using a servo-hydraulic test frame. A hydraulic actuator controlled by a computer applies a cyclic load to the test specimen. The increase in length (da) of a preexisting "starter crack" is then measured against the number of load cycles (dN).
This procedure is typically carried out in accordance with ASTM E647 (Standard Test Method for Measurement of Fatigue Crack Growth Rates). A graph of cyclic stress versus the crack growth rate is produced as an output of this test for further analysis.