The Application of Simplified Loadpath Models (SLMs) to Improve Body Structure Knowledge and Efficiency 2020-01-0912
Simplified Loadpath Models (SLMs) of the advanced body in white (BIW) design concept provide a highly flexible and rapid platform to explore body structure loadpath alternatives and performance:weight optimization. The SLM modelling process combines higher order Beam and Bush finite elements with coarsened Shell-meshed panels to represent the body structure. FCA US LLC has understood and validated the SLM build process for a BIW, and correlated key structural performance metrics to higher order, detailed Finite Element (FE) models. While the benefits of loadpath optimization through Beam element parameter variation is well-documented and applied extensively for these types of models, this paper covers another valuable benefit of the SLMs; to provide a better understanding of the sensitivities and influence of joint stiffnesses on key body structure attributes to promote more intelligent and efficient body structure joint designs.
Current techniques for joint sensitivity studies typically change the stiffness of a zone of finite elements within a prescribed joint geometry and provide some insight into the critical joints and panels for key body stiffness metrics. However, this approach cannot effectively de-couple the stiffness of each joint arm, as property changes across a zone of elements may coincidentally change the rotational stiffness of multiple arms. The parameterization of Bush elements used to characterize SLM joints provides a better mechanism to discretely vary and de-couple the rotational stiffness of each arm of the joint, enabling a more thorough understanding of joint behavior in the body structure through large scale Design of Experiments and data mining. The analysis of design variable sensitivities provides an improved understanding of critical joint parameters for each joint, and valuable insight to develop more efficient joint geometries.