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.