Kulkarni, H., Wang, Y., and Alanoly, J., "Effective Application of CAE Guidance for Hemmed Closures Throughout the Vehicle Development Process," SAE Technical Paper 2017-01-1310, 2017.
The perceived quality of automotive closures (flushness and margin) is strongly affected by flanging and hemming of the outer panels and assembly respectively. To improve the quality of closures, the traditional hardware approach needs significant amount of time and costly die re-cuts and trials with prototype panels. Thus, such approach may delay the vehicle program and increase the overall investment cost.The proposed CAE methodology provides upfront design guidance to dies and panels, reduces time and increases cost savings associated with flanging and hemming while improving overall quality of the closures. In this proposed approach, as a first step, analytical formulae and design of experiments (DOE) are followed to estimate magnitude of design parameters of panels and dies as the upfront design guidance. Secondly, finite element (FE) models are developed based on nominal design (uniform thickness) of the outer and inner panels, and also used to optimize the design parameters, such as flanging die radius, clearance, etc., to eliminate failure modes during flanging and hemming, for example - large spring back angles, roll-in and out, etc. In the third stage, CAE models of varying thickness of the inner and outer are used to tune design parameters and eliminate any presence of the failure modes and to assure good quality of the hemmed closure. At the final stage, physical hardware test data are used to correlate simulation results and validate the effectiveness of CAE methodology to guide design. This forms a closed-loop process that improves simulation quality and confidence over time, and also resource and cost savings.