Development Of An Energy-dissipating Rear Underrun Protective Device And Finite Element Analysis

Traffic accidents occur frequently with the increase of vehicle ownershipincrease in China. Rear end crash accidents account for nearly20%of all reportedtraffic accidents, of which the car-truck rear end crash accidents resulted in thehighest casualty rate in all types of accidents. In car-truck rear end crash accidents thecar is damaged severely and the occupants often suffer fatal injuries because of theobvious differences between cars and trucks in mass, structure and stiffness.Therefore, an effective rear underrun protective device (RUPD) has a greatsignificance to protect the car occupants from this type of crash accidents.The objective of this study is to develop an effective energy-dissipative RUPDwith excellent performance to reduce risk of the car occupants in car-truck rear endcrash accidents.The methods and process for development of the RUPD are described as follows.First, the sizes of20trucks’ chassis are measured. The profiles of110d omesticpassenger cars are statistically analyzed to collect data for determination of designvariables. A prototype of the new RUPD is designed according to GB11567.2-2001and the collected data above. The geometry model of the new RUPD is built by UGand its finite element model is made by HyperMesh afterwards. In order to make acomparison of the performance of the existing RUPD with the new RUPD, arepresentative RUPD is selected as the typical RUPD and is modeled by using finiteelement method. Simulations of moving barrier (MB) rear-end crash to RUPDs arecarried out by using LS-DYNA code. The configurations of the simulations aredesigned in accordance with the test requirements of the national standard. The peakvalues of the MB’s acceleration, rebound velocity and underrun length are the threecriteria to evaluate the performance of the RUPDs in the tests. Finally, theoptimization of the new RUPD is performed by using the design variables of thicknessof the new RUPD components. An orthogonal test is carried out with6thicknessfactors and3levels. The comprehensive evaluation method is used to find a bestcombination of the variables which is then submitted to perform MB crash simulationto check the effectiveness of the optimization results.The results of the study show that in the crash simulation for the new RUPD, theMB’s acceleration peak value is12.2g; the rebound velocity peak value is1.3m/s and the underrun length peak value is-100.6mm. The negative sign means the MB doesn’tunderrun. All of the peak values calculated from MB can meet the requirement ofGB11567.2-2001. So the new RUPD has effective function in block of underrun andenergy absorption. In the simulation for the typical RUPD, the MB met no effectiveresisting and underran, so the typical RUPD can’t meet the requirements of theregulation. The optimized new RUPD lose weight to27.3kg, which is46.5%less thanthe prototype’s weight of51.0kg. In the MB crash simulation for the optimized RUPD,the MB’s acceleration peak value is9.0g; the rebound velocity peak value is0.7m/sand the underrun length peak value is-28.7mm. The three peak values are26.2%,46.2%and71.5%less, respectively than the results before optimization. The methodsand results in this study have certain engineering significance, which can be areference in improving of the car-truck rear-end crash safety.