Study On Frequency-Weighted Accelerated Random Vibration Test Method For Transportation Packaging

With the advancement of technology and the enhancement of manufacturing capabilities,the ability of products to withstand vibration fatigue damage has increased correspondingly,resulting in increased difficulty and time cost in product reliability evaluation testing.Accelerated random vibration testing is a commonly used method to address this issue.Currently,laboratory accelerated vibration testing for product transportation packaging is based on the principle of "simple scale accelerated random vibration".This principle limits the value of the acceleration factor to avoid excessive amplification of the vibration magnitude near the resonance frequency,which can lead to changes in the damage mechanism and limit testing efficiency.In response to this situation,this paper employs theoretical research,numerical simulation,and comparative experiments as the main research methods to conduct in-depth research on the theory and methods of accelerated random vibration testing for product transportation packaging,and proposes a segmented acceleration testing method.The specific research contents are as follows:(1)The frequency-domain method for calculating fatigue damage under random vibration excitation was studied.Based on numerical simulations of the bimodal spectrum model,a simplified Bands method(BD method)was proposed to reduce computation and simplify calculation steps.The BD method uses a series of deformation spectra generated by ASTM standard power spectral density curves for fatigue damage calculation.The calculation error of the BD method was compared with commonly used TB and NB methods,using the Dirlik method as the benchmark for the highest recognized calculation accuracy in the industry.The results showed that the BD method had the smallest error(0.72%),greatly ensuring the accuracy of damage calculation while reducing the computational intensity of the model.This laid the theoretical foundation for the proposed frequency-domain weighted acceleration test method in the following sections.(2)A theory and method for frequency-weighted acceleration random vibration testing based on the BD method has been established.Firstly,the relationship between the response of key points and excitation within different frequency ranges was established by the dynamic model of the packaging system and finite element analysis.Then,based on the fatigue damage equivalence of the BD method,an expression for the time compression ratio for frequencyweighted acceleration random vibration testing of transport packaging was constructed.Furthermore,the design method and implementation process of frequency-weighted acceleration testing for transport packaging were given.Finally,the frequency-weighted acceleration experimental methods based on the BD method,Dirlik method,and TB method were used to design the measured PSD in different frequency ranges.By comparing the acceleration factor error,the accuracy and effectiveness of the proposed acceleration testing method were verified.(3)The simulation effects between the proposed frequency-weighted acceleration test method and the commonly used acceleration simulation test method in the laboratory were compared.Field transportation tests were conducted on packaging materials,and transportation vibration signals of a medium-sized box truck on city roads in Wuxi were collected.The measured PSD was processed using the proposed frequency-weighted acceleration method and the simple scale acceleration method.Laboratory acceleration simulation tests were conducted using the frequency-weighted acceleration PSD,simple scale acceleration PSD,and national standard PSD,with the plastic deformation,load-bearing capacity,and cushioning performance of the corrugated padding as the evaluation criteria for padding damage.The advantages and disadvantages of the three laboratory acceleration simulation test methods were compared from the perspectives of fatigue damage equivalence and time cost savings.The results show that the national standard test method had the lowest simulation accuracy and provided conservative test results.The frequency-weighted acceleration test method had the best simulation accuracy,and the error rate of cushion damage and test time were reduced by 10.1% and 29.7%,respectively,compared to the simple scale acceleration test.This study establishes a frequency-weighted acceleration random vibration test theory and method suitable for product transportation packaging.This method optimizes the weight ratio of different frequency bands to reduce the additional risks caused by nonlinearity due to resonance and shorten the test time.It enables the laboratory damage of the system to approach the actual circulation environment in a shorter test time,and has certain engineering value in improving the accuracy and efficiency of product reliability evaluation under laboratory accelerated random vibration conditions.