The Effect of Non-Flat Interfaces On System Dynamics

Abstract

Manufactured surfaces are never completely flat due to a variety of reasons including: variability in manufacturing operations, material behavior and achievable geometric tolerances. The curvature of surfaces is a local geometric effect that affects part-to-part variability of jointed surfaces. Joints with different interface geometries behave in unpredictable ways (Brake (2018) The Mechanics of Jointed Structure: Recent Research and Open Challenges for Developing Predictive Models for Structural Dynamics. Sandia National Laboratories, William Marsh Rice University. Springer, Cham). Among the factors that drive the uncertainty in joint performance are frictional micro and macro sliding events, surface tribology effects, residual stress from manufacturing and assembly, loss of bolt pre-load, changes in contact area and the resulting pressure field variation around the joint. The goal of this research is to identify key variables that account for the measured uncertainty in the dynamics of jointed structures, which may have local regions of conformal and non-conformal contact due to variability inherent in the manufacturing process. Using the standard benchmark system of the Brake-Reuβ beam (BRB), recommendations are made for which design parameters require higher tolerances than others to minimize variability in a cost-effective manner. Conformal beams with strong and weak curvature are studied as well as non-conformal (flat vs. curved) beams. Experimental and numerical approaches model and validate the physical behavior of beams to understand primary causes of non-linearity in joints with different interface geometries.