Novel Technique to Simulate Hood Closing Effort under Quasi-Static Condition and Its Strategic Correlation 2019-26-0342

Hood closing effort under quasi-static conditions, known as static latching, is an event where the hood latch moves from secondary position to primary latched position due to external force applied by the customer to the hood. When customers close the hood slowly, it may not get latched due to insufficient force transfer to the latch thus requiring additional effort. Recent vehicle designs have the hood latch mounted further rearward than typical from the hood leading edge due to architectural challenges. Pedestrian protection (PedPro) requirements drive hood designs with reduced stiffness above the latch resulting in poor load transfer from the customer to the latch. This often results in high customer effort during quasi-static hood closing events. This additional effort may cause undesirable permanent deformation on the hood outer panel. In absence of proper simulation procedures, design engineers must adjust the latch and hood bumper interfaces on a trial basis during vehicle builds, leading to potential gap and flushness issues on the vehicle. Poor closing effort can result in costly engineering changes late in the vehicle development cycle. To shorten the hood development time and avoid late design changes, it is critical to develop a virtual simulation procedure that can reproduce the hood quasi-static closing event. This paper proposes a strategy to sense hood latching by calculating the force at the latch striker wire through simulation. The proposed strategy was validated with hardware measurements on multiple vehicles. The proposed method was able to achieve excellent correlation with the test in predicting hood latching for a specific customer effort. This paper also examines the sensitivity of various other parameters like seal stiffness, bumper interference (pre-load), latch connection type, non-linearity and loading direction in order to identify significant parameters contributing to hood latching effort.