Modeling Snap-Fit Stiffness for Improved BSR Predictions in Automotive Design

Squeak and Rattle (S&R) issues present significant challenges in the automotive industry, negatively affecting the perceived quality of vehicles. Early identification of these issues through rigorous testing protocols-such as auditory assessments and dynamic simulations-enables the development of more robust systems while optimizing resource use. Finite Element Method (FEM) simulations are crucial for identifying S&R issues during the design phase, allowing engineers to address potential problems before the creation of physical prototypes. By developing high-fidelity virtual models and accurately simulating flexible connections, these simulations effectively capture rattle effects, enhancing prediction reliability. Traditional snap stiffness calculations typically employ a cantilever-based formulation, which is suitable for simple snap-fit designs but insufficient for more complex geometries that require enhanced stiffness. To address this limitation, the proposed methodology utilizes non-linear simulations for precise snap stiffness determination. A snap-fit was isolated from CAD and meshed using solid elements, with appropriate contact properties established for non-linear static analysis. The pull-out force was captured and validated against previous work to ensure accurate physics representation. Snap stiffness was calculated based on head deflection, revealing noticeable differences compared to standard calculations. An updated model incorporating these new stiffness values demonstrated a change in maximum peak displacement, underscoring the importance of accurate stiffness values in BSR simulations to properly capture system behavior. This proposed methodology represents a step toward standardizing snap stiffness calculations, ensuring the repeatability and reliability of results generated from S&R simulations.