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In order to reduce the number of head injuries sustained by pedestrian accidents, safety engineers are developing pedestrian friendly hood systems through gauge optimization of the hood inner panel. In this study, the clinch method was employed to assemble a pedestrian friendly hood with a 0.5mm thick inner panel. Static and dynamic analyses were carried out to determine the clinch experiencing the highest loads and to understand the fatigue behavior of a clinched hood during a slam event. The macroscopic failure modes of clinched joints by hood slam were studied by means of a scanning electron microscope. A simple equation was derived to correlate the hexahedron spot weld model as a substitute for clinching in order to obtain an equivalent stiffness for a clinched joint within the linear region of an F-D curve. The F-D curve was obtained by lap shear testing.

In order to meet the safety requirements and to reduce the component weight, it is necessary that destructive tests for new bumper system to be performed. These tests are very expensive and time consuming. Therefore, the economical design and analysis of bumper system using finite element method becomes very popular. This paper attempts to show a method using computer simulation which has been broadly adapted in the various design stages of vehicle development. The analyses have been performed for center-center pendulum and barrier impact of bumper system of thermoplastic material under the process of injection molding. Also, the results predicted from finite element analysis are compared with test results to evaluate the propriety of analysis procedure.