Theoretical analysis and experimental verification on ternary-waves method to compile accelerated spectra

The equivalent damage calculation formulae of fatigue crack formation and growth are established. In order to compile the fatigue crack formation and growth accelerated load spectra, the main wave shapes and load sequence of the actual load spectrum are kept constant, and the carrier waves are cut off. And secondary waves are put together into new secondary waves to shorten the test time according to the equivalent damage calculation formulae respectively. Then by the fatigue cumulative damage calculation of the fatigue crack formation and growth accelerated load spectra, the one corresponding to the bigger damage is determined as the fatigue accelerated test load spectrum. Therefore in the test process, the fatigue accelerated test spectrum may be applied till fatigue failure, the engineering fatigue crack length of full-scale structure need not be inspected, and the fatigue crack formation accelerated load spectrum need not be transferred into the fatigue crack growth accelerated load spectrum. Finally, it is verified by tests of two kinds of specimens that the damages of the specimens caused by the accelerated load spectra are near to those by the actual load spectra; namely, the tested life of actual load spectra is similar to that of accelerated load spectra. But the test time of accelerated load spectra is shortened by about three-quarters that of actual load spectra. From these tests, it is also found that the fatigue accelerated test spectrum has an advantage over FALSTAFF spectra.