Abstract: Dynamic stress tests are carried out on the line of Beijing to Chengdu, with the test car unit composed of one C70E general open wagon and one NX70 general flat wagon equipped by the test devices. The stress-time histories of different critical locations are gained for the C70E gondola car body. To research the car body fatigue strength of the C70E gondola with high accuracy, different fatigue threshold values are chosen to compile the stress spectra. The signals are transferred from time domain to frequency domain by the rain flow counting method, to establish spectra. Under the Miner linear accumulative damage law, fatigue damage accumulations are calculated from different spectra gained by different fatigue threshold values and the results show that small stress cycles contribute to the fatigue damage. Considering both the amount of work required and the influence level of the small stress cycles, it is reasonable to choose 5% of the stress range (the difference of the maximum amplitude and the minimum amplitude) as the threshold value for compiling stress spectra. By comparing the fatigue damage for different critical locations, it is observed that the relatively weak parts of the car body are located in the welded joint with bolster cover plate and center sill and the welded joint with large cross beam and side beam near an end side. The fatigue life of C70E open wagon is assessed, which satisfies the design and operational requirements.

Key words: small stress cycle;C70E car body;stress spectrum;fatigue damage, energy absorption rate, fretting wear, impact force, tube deformation , low-energy impact