New testing procedure to determine da/dN–ΔK curves at different, constant R-values using one single specimen

A new concept for fatigue crack propagation tests has been developed. Using a single specimen, it is possible to determine fatigue crack growth curves (da/dN–ΔK) for every stress ratio between R = 0.9 and R = −1. Additionally, the new concept also provides threshold values for fatigue crack growth for different values of R. In combination with a continuous, autonomous crack length measurement tool (such as the DC potential drop method) this testing procedure can be implemented with minimal time and effort. The test procedure consists of a sequence of Kmax-constant tests with decreasing crack growth rates. There should be no load history effects. According to the procedures described in the ASTM Standard E 647, the results using this new testing procedure fit very well to the da/dN–ΔK curves generated with different specimens. The tests also fulfil all the requirements of ASTM Standard E 647.