Abstract: Carbody acceleration is determined as the input parameter of the load computation formula derived from the balancing equations of the bogie frame. The parameter evolution respect to the operation mileage is also obtained by statistical analysis of the vibration data in two typical re-profiling intervals. The long-term expanding spectrum and feature accelerations computing method is proposed for the specific worn states of the wheelsets through exceeding cumulative frequencies according to the linear damage accumulation principle. The deterioration function is proposed as the facts that vibration levels of the bogie are gradually increased due to the stability downgrading and thread roughness increasing. Deterioration function describes the loads increasing process with the operation mileages and is fitted by long-term tracking test data. The equivalent feature acceleration as the test rig spectrum for the life cycle is derived from the deterioration function based on the generalized Basquin formula. The test spectrum is damage consistent with respect to the real operation conditions as the critical factors such as frequency compacting, damage expanding, and periodic loading deterioration are taken accounts.

Key words: bogie frame, loading spectrum, test rig, loading deterioration function