Physics-Based Friction Modeling for Bolted Structures

Justin Porter, Rice University

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Bolted connections are ubiquitous in large structures that are impossible or impractical to manufacture as a single part. Understanding the dynamic vibration characteristics of these structures is critical to improving reliability and efficiency in aerospace and energy generation systems. Specifically, it is important to characterize how structures dissipate energy (damping) and the frequency of vibrations. Both properties are strongly influenced by the friction within bolted connections. However, this friction is not well understood; thus, extensive experimental testing is required to characterize the dynamic structural behavior. Furthermore, the inclusion of friction results in nonlinear behavior with the frequency and damping depend on the amplitude of vibration. The present work develops a physics-based model of friction within bolted connections by summing over probable interactions of surface features to determine contact forces. The simulations leverage HPC resources to perform the computationally intensive calculations of these frictional forces and develop further insight into the physical mechanisms of friction in bolted structures. The present model produces smooth variations from sticking to slipping at the contact interface allowing it to better capture the qualitative trends of experimental structural responses. Furthermore, the present work highlights the importance of capturing the curvature of the contacting surfaces and hardening characteristics of the material. Numerical results are benchmarked against experimental results for a characteristic three bolt joint. The current effort highlights a path towards a predictive model of bolted structures with the potential to improve reliability and efficiency while reducing the billions of dollars spent annually on vibration testing.

Abstract Author(s): Justin H. Porter, Matthew R. W. Brake