Abstract: These were analysed the varying processes of the local stress-strain and the crack opening stress which determine respectively amount of damage and crack propagation rate after loading spectrum was transformed into load-time course. They vary at a instrinsic periodicity. A concept of intrinsic periodic spectrum block was put out, which represents a damage element of load-time course. Various fatigue spectra were analysed further so that it was found that they are of united intrinsic periodic spectrum block. Thus the damage differences which various fatigue spectra produce to a component are not so big as people consider usually. It was still verified by the theoretic analysis tests.

Key words: Crack closure, Damage, Fatigue, Loading spectrum, High-speed EMU Rolling contact fatigue Curving Shakedown map, Tγ model