Calculating Vehicle Side Structure Stiffness from Crash Test Data: Effects of Impactor Characteristics

This research examines the effects of impactor characteristics on the calculated structural stiffness parameters A and B for the struck sides of late-model vehicles. Such studies were made possible by the fact that for the 2018 model year, the National Highway Traffic Safety Administration conducted New Car Assessment Program side impacts (with known DOT numbers) on 29 vehicles using both a rigid pole and a moving deformable barrier (MDB). In all, a total of 60 side impacts with known DOT numbers were identified for analysis. However, due to various deficiencies A and B were calculable for 47 of these, which meant that there were only 21 2018 vehicles for which A and B could be compared between the two types of tests. Structural behaviors of two of these vehicles were judged to be outliers, and were thus excluded from further analysis. Classifying the 19 remaining vehicles according to the categories defined by Siddall and Day, only Class 2 multipurpose vehicles (MPVs) were represented by sufficient vehicles (10) to search for trends within a given vehicle category. More scatter in the results was observed in both A and B values for the MDB impacts compared to the pole impacts. B parameters showed more variation than did the A parameters. Standard deviation for the MDB B values was about 71% of the average. Little to no correlation was found between stiffness values in the two test modes. In either test mode, there was poor correlation between either A or B and vehicle wheelbase. These studies confirm previous findings; namely, that the side structure stiffness parameters vary widely, even within a given class, and that they cannot be predicted on the basis of other vehicle characteristics. Detail results, and the methods by which they were obtained, are presented in the paper.