Abstract:

Extrapolation method of multiple load histories is presented, and compilation of fatigue test load spectrum for underfloor equipment bearing structure is given. The extrapolation method is based on multiple load histories rainflow matrix and two-dimensional kernel density estimation(KDE) theory. According to the rainflow counting matrix extrapolated above, the compilation of fatigue test load spectrum is completed by applying mean stress correction formula, the cumulative damage theory and equivalent damage criterion. The extrapolation method is verified by EMU underfloor equipment line test vibration data, then fatigue test load spectrum of equipment bearing structure is compiled, and the fatigue strength of bearing structure is calculated respectively under fatigue test program load spectrum and line test vibration data. The extrapolation results of line test data show that error of damage between KDE extrapolated load and actual load is 3.6%, the low cycles and large amplitude load can be obtained by KDE extrapolation method when the extension scale is big enough. Fatigue strength calculation results show that damage from fatigue test program spectrum increased by 43.8% than that from line test data due to the large amplitude load produced by the KDE extrapolation method. So, in the compilation of fatigue test program load spectrum, it is essential to calculate the large amplitude load which may occur. This research provides load spectrum compilation reference for other bearing structure.

Key words: bearing structure, extrapolation, fatigue test, load spectrum, program spectrum, underfloor equipment