Liftgate Slam by Bilinear Quasistatic Approach Using Modal Transient Method under Equivalent Static Loads

<div class="section abstract"><div class="htmlview paragraph">Automotive closure slam is the most crucial attribute affecting the closure structure and its mountings on BIW due to its high occurrence in real-world usage. Thus, virtual simulation of closure slam becomes necessary and is generally carried out using explicit codes with associated technical hitches like all-requisite inputs availability, FE modeling and analysis techniques, substantial human effort, high solution time, human and computational resource competence, or even access to suitable expensive explicit FE solver. Hence it becomes challenging to virtually analyze the design at every design phase of product development cycle under strict timelines leading to possibilities of both over- and under-designed parts, sometimes resulting in physical testing or even field failures. So, the need for an alternative simplified representation of closure slam, addressing the typical issues faced during explicit dynamic simulation and producing acceptable analysis outputs, gains significance. In this article the rotation of the liftgate about its hinge axis during slam is first segregated into two successive rotation phases based on the geometric configuration of its latch/locking components in terms of initial state to half-latched and half-latched to full-latched condition. Linear springs are introduced at critical locations in the FE model and the two rotation phases are initially represented by two linear static analysis, under equivalent static loads, determined using kinematic and inertia properties relationships at a particular operating velocity. This is followed by modal transient analysis on the linear static analysis setups in successive time domains in accordance to the rotation phase. Kinematic and inertia properties compliance are ensured during each phase. The combined modal transient analysis results, representing the entire event, shows outputs consistent with explicit dynamics simulation and stress history in tandem with the loading dynamics, thus resulting in a reasonable estimate of fatigue life of the structure.</div></div>