Research On Load Spectrum Compiling For Transmission Shaft In Transmission System Of Tracked Vehicle

This paper aims at establishing load spectrum that can reflects real load usage condition of transmission shaft.Torque and relevant driving signals on unsurfaced road were obtained through vehicle experiments,then real regularities of distribution of load usage were extracted from load information through classified processing by gears.The load extrema were extrapolated reasonably and the load distribution was fitting in high level,and the multi-profile load spectrum was obtained.According to the fatigue analysis theories,variable load spectrum was gained,which can provide supporting data and research experience for fatigue design and reliability improving of this transmission shaft.RF telemetry torque sensor was installed on the transmission shaft of tracked vehicle,and CANoe device was adopted as synchronous acquisition equipment for all vehicle signals.Through unified sampling frequency,one point to point relationship of torque,rotational speed and gear signals was achieved on the time axis.According to the unfavorable ingredients existing in the real torque signal,chose methods such as zero drift correcting,spike removing and rain flow filtering to process the raw data of torque.Based on the criteria of least testing times,the load sample data was validated to have a higher confidence level.Analyzed the bimodal distribution form of rain flow matrix(RFM)in amplitude and mean dimensions,then based on the goodness of fit,chose the best distributions to respectively fit amplitude and mean independent distributions.The load extrema were extrapolated and their rationality was validated.The compiling flow was designed on 2D kernel density estimation,and the multi-profile load spectrum with high-level fitting distribution was obtained from it.Adopted methods such as mean stress modifying and equivalent damage conversion,chose 0.8 time of eighth amplitude as small load deleting value,eight variable amplitude load spectrum was gained on the condition that total cycles decreased by 99.33% and total damage decreased by 0.29%,which accelerated the fatigue validation test.According to the relationship of torque and rotational speed of transmission shaft,three-level speed loading method was provided.Combined fatigue analysis theories with material fatigue properties of this shaft,its fatigue total damage was calculated,which validated the reasonability of the truncation value of small load.