Finite element simulation of the Offset-Deformable Barrier Euro NCAP crash test reproduction on a HYGE sled for assessing ten-year-old child safety

This research focuses on the definition of the guidelines to simulate a sled test which reproduces the ODB Euro NCAP crash test, using LS-DYNA Finite Element code. In addition, the last sections are based on the validation of the model, comparing numerical results with those of an experimental sled test performed with the same equipment in late 2018, and on a sensitivity study on the friction coefficient of a virtual slip ring. Several FE models have been utilized, to represent vehicle body, seats and restraint system with LS-DYNA. The subject of the test is a ten-year-old child dummy (Q-series Q10), placed on a booster seat in the second-row seat of the vehicle. Both experimental and numerical dummies were provided by Humanetics®. All the pre-processing steps needed to perform this kind of simulation have been described throughout this thesis. The most investigated step was the generation and calibration of the virtual restraint system, built utilising ANSA by BetaCAE. The LS-DYNA pretensioner and retractor were calibrated using different data from the experimental test as reference. The model was verified and validated computing cumulative error and validation metric. The head accelerations showed values of V equal to 78, 79 and 76% respectively, reasonably predicting the trend of the experimental curves. Additionally, the HICs have been well predicted, with coincident time instants and peak relative error below 15%. Chest and pelvis accelerations were predicted with an average V equal to 85%, constituting the areas of highest performance of the FE model. Upper neck forces and moments displayed an acceptable level of prediction, with V at least equal to 70%, whereas the lower neck showed the lowest correlation of the results, mostly on x and z-moments. It is important to underline that all biomechanical data in this thesis document were normalized for confidentiality reasons. Lastly, a sensitivity study on the influence of the dynamic friction coefficient FC of the lower LS-DYNA slip ring on the dummy injury responses was performed, obtaining a more correlated operation of the belt with respect to the experimental setting. The analysis was performed comparing all values of E and V among the different configurations, concluding that the most correlated setting has FC = 0.4, with an increase in V of 10% in the upper neck region.