SENSITIVITY STUDY OF PLASTIC MATERIAL FAILURE AND COUNTER MEASURE TO IMPROVE THE ECE R17 SEAT BACK ENERGY ABSORPTION

摘要

ECE R17 seat back energy absorption test is critical for limiting head injury of the passenger in the rear seat during frontal impact. The challenge is to meet opposing requirements for the head restraint; it needs to be provide soft impact to head while meeting the other strength requirements. In the physical test, the plastic handle used for dumping the seat cracked and the 3ms clip was met by a margin of 3%. Sharp edges observed on the plastic handle was not acceptable even though the acceleration requirement was met. The objective of this study is to correlate the plastic handle failure in the test with CAE and to develop counter measures to mitigate the risk due to direct contact of the head form on the plastic handle thus avoiding failure of the plastic handle. LS Dynais used to simulate the seat back (Head Restraint System) energy absorption test. The impact load from the free moving head form was transferred to the head restraint foam and then to the top mounted plastic handle on seat back, which resulted in failure of the plastic handle. The baseline CAE model did not show failure for the plastic handle. The material model used for the plastic handle is updated with a MAT_024 material model with plastic failure strain defined as 1%. This is found to givebetter correlation of the plastic failure happening in the test. Then countermeasure wasdeveloped using the correlated model to absorb energy thus transferring less load to the plastic handle. The performance has been validated using physical test. The analysis results helped to understand influence of material failure definition of plastic components. In addition, how effectively MAT_024 card with failure can be used to improve correlation. Variation in the material properties of the plastic handle due to manufacturing process is not considered in this study.