An Efficient Solution Procedure For Elastohydrodynamic Contact Problems Considering Structural Dynamics

This work presents an efficient solution procedure for the elastohydrodynamic (EHD) contact problem considering structural dynamics. The contact bodies are modeled using reduced finite element models. Singly diagonal implicit Runge-Kutta (SDIRK) methods are used for adaptive time integration. The structural model is coupled with the nonlinear Reynolds Equation using a monolithic coupling approach. Finally, a reduced order model of the complete nonlinear coupled problem is constructed. This work was published by Saint Philip Street Press pursuant to a Creative Commons license permitting commercial use. All rights not granted by the work's license are retained by the author or authors.

This work considers dampers that do not solely focus on a single strategy but instead combine them. The capabilities of conventional dry friction dampers are expanded by taking into account piecewise defined contact geometries. This leads to friction dampers that change their behavior depending on the amplitude of the oscillations. The vibration damping device in this work, introduces damping at high oscillation amplitudes and takes advantage of absorption at low oscillation amplitudes.

The gas foil bearing (GFB) technology is a key factor for the transition to oil-free rotating machinery. Among numerous advantages, GFBs offer the unique ability to be lubricated with working fluids such as refrigerants. However, the computational analysis of refrigerant-lubricated GFB–rotor systems represents an interdisciplinary problem of enormous complexity. This work pushes forward existing limits of feasibility and establishes a new strategy that enables stability and bifurcation analyses.

The impact of two non-uniform elastic rods is considered and a recursive method was developed that solves the inverse problem: Find the location-dependent impedance function of the impacting rod that generates a prescribed impact force. The developed method delivers exact solutions in closed-form. Moreover, a condition is derived which states if a physically meaningful solution exists. Finally, the underlying 1D model has been validated experimentally.

Elasto-Hydrodynamic Lubrication deals with the mechanism of elasto-hydrodynamic lubrication, that is, the lubrication regime in operation over the small areas where machine components are in nominal point or line contact. The lubrication of rigid contacts is discussed, along with the effects of high pressure on the lubricant and bounding solids. The governing equations for the solution of elasto-hydrodynamic problems are presented. Comprised of 13 chapters, this volume begins with an overview of elasto-hydrodynamic lubrication and representation of contacts by cylinders, followed by a discussion on equations relevant to lubrication, including the Reynolds equation. The reader is then introduced to lubrication of rigid cylinders; the importance of film thickness in highly loaded rigid contacts; the elasticity of solids in contact; and the theory of elasto-hydrodynamic lubrication. Subsequent chapters focus on apparatus and measurements of film thickness and film shape; friction and viscosity; and lubrication of gears and roller bearings. This book will be of interest to tribologists.

In today's product development process, fast and exact simulational models of complex physical problems gain in significance. The same holds for the elastohydrodynamic (EHD) contact problem. Thus, the objective of this work is to generate a compact model for the EHD contact problem by the application of model order reduction. Thereto, the EHD contact problem, consisting of the nonlinear Reynolds equation, the linear elasticity equation and the load balance, is solved as a monolithic system of equations using Newton's method. The reduction takes place by projection onto a low-dimensional subspace, which is based on solutions of the full system. Moreover, a so-called system approximation is executed at which the reduced system matrices are substituted by less complex surrogates. For the stationary EHD contact problem, an algorithm for the automated generation of the compact model is presented. This algorithm provides fast and numerically stable reduced systems on a given parameter range. Additionally, the reduced Newton method is extended to the consideration of Non-Newtonian fluids whereat highly accurate results are obtained requiring a very low computational time. Furthermore, a new formulation for the transient EHD contact problem is introduced, at which the computational area is adapted to the current contact size. This kind of morphing enables efficient reduced models in particular for excitations of large amplitude. Beside of the reduced Newton-method with system approximation, the method Trajectory Piecewise Linear (TPWL) is applied to the transient EHD contact problem. Here, further speed-up potential arises. Despite a distinctly lower computational time, the reduced model is in very good accordance with the full system.

Nonlinear Structures & Systems, Volume 1: Proceedings of the 40th IMAC, A Conference and Exposition on Structural Dynamics, 2022, the first volume of nine from the Conference brings together contributions to this important area of research and engineering. The collection presents early findings and case studies on fundamental and applied aspects of Nonlinear Dynamics, including papers on: Experimental Nonlinear Dynamics Jointed Structures: Identification, Mechanics, Dynamics Nonlinear Damping Nonlinear Modeling and Simulation Nonlinear Reduced-Order Modeling Nonlinearity and System Identification