Study On Random Vibration Analysis And Simulation Method Of Road Transport Packaging

Vehicles suffer shock and vibration unavoidably caused by pavement irregularity and travel speed mutation,which results in package damage and causes a big economic losses.Study on random vibration characteristics and simulation method of road transport packaging,and reappearing the actual random vibration of distribution packaging for random vibration test of product in laboratory,which will be of great significance for accurate protection packaging design.The research advance about random vibration characteristics and simulation method on transport packaging,random excited dynamics of packaging cushioning were reviewed firstly.Five representative types of vehicles widely used for express delivery were chosen for random vibration measurement with different payload,speed and road type in South China.The vibration levels,power spectral density,probability density distribution and vibration characteristics of those measured vibration signals were analyzed.Assessments in comparison with the international standards(American Society of Testing and Materials,ASTM;International Safe Transit Association,ISTA)and previous studies were presented in this paper.The factors which influence vehicle vibration were concluded to four aspects including road,vehicle,driver and signal measurement.The results revealed that vibration levels were significantly higher in the vertical axis as compared with the lateral and longitudinal axis for all journeys.Vibration levels increased with the travel speed,and vibration levels were higher in unload or light load condition especially with high speed.Vibration level of the sedan car was the smallest,terminal distribution vehicles were the second largest,and the highest vibration level happened in the trunk transportation vehicles.The Hilbert Huang Transform method was used for analyzing random vibration signal of transport packaging for the first time.The non-stationary and non-Gaussian random vibrations were decomposed into a series of intrinsic mode functions and one residual.It was useful in separating the high-frequency shock components from the underlying low-frequency vibration.Not only a new approach for shock detection and extraction was proposed,but also a new approach for random vibration simulation of transport packaging was proposed.Shock events which buried in random vibration can be accurately detected and extracted.This method decomposed the original signal into a series of approximate Gaussian vibration segments and a shock segment with a higher kurtosis value.Simulating Gaussian distribution vibration one by one from the power spectral density of each decomposed segments,and the overall signal was simulated by concatenating of each simulated Gaussian segments.Results showed that the simulated signal had not o nly the same overall acceleration root-mean-square,duration with the original signal,but also had a similar power spectral density curve and statistic characteristics to the original signal.Three vibration signals from different vehicles were chosen for simulation performance comparison.Simulation effects comparison of the new proposed method(Shock Extraction)with the Single Level PSD,Three Way Wplit Wpectral and Wavelet Decomposition methods were evaluated in both time and frequency domain finally.The results confirmed that the simulated signal which generated by the new proposed simulation method(Shock Extraction)was more approximate to the original signal.