Finite element analysis of frictional damping forces in structural joints subjected to flexural vibration

A major source of damping that occurs in a structure results from frictional damping forces and relative motion of the connected parts at a joint interface. This dissertation presents a numerical finite element method for determining the frictional damping in high strength structural joints subjected to flexural vibration.;The analysis first considers the dynamic response of the structural joint without interface friction. A normal modes analysis determines the natural frequencies and corresponding mode shapes of the structural joint without friction. Next, a scaled modal vector is applied as an enforced displacement load in an incremental linear static load scaling analysis to determine the energy dissipated by friction in one load cycle. This frictional energy dissipation can be used to calculate an equivalent viscous damping coefficient and subsequently a linearized forced response calculation.;Test/analysis correlation of an example structural joint is included.;Elastostatic contact problems with friction form a class of problems that are load history dependent because of the non-conservative, irreversible nature of the frictional forces. In the analysis, the contacting bodies are coupled together using appropriate contact and friction conditions. Then the use of substructuring is proposed to develop a governing system of equations. An iterative procedure is employed to solve the system of equations. Iterations are chosen to select incremental load level, determine the total contact area at each load step, and determine the nonsliding portion of contact (due to friction) at each load step.