Effect of Energy Dissipation Due to Friction at the Joint of a Simple Beam Structure

摘要

The Strategic Defense Initiative has generated new interest in the development of more stable space structures. This interest has increased the need for more detailed knowledge of the behavior of engineering structures under dynamic loading. Interests lie in decreasing the amount of vibration by both passively and actively damping the structure. A means exists to passively damp structures by friction damping resulting from relative slip between joint interfaces. It may be feasible to increase the damping in a structure by allowing more friction damping than is normal and thereby controlling the vibration response. This thesis incorporates friction damping in a one-dimensional model. Finite element techniques are used to accomplish the numerical analysis. A clamped-clamped beam is used as the physical model. The mid-point of the two element beam is allowed to slip in rotation, but not in translation. Because the one-dimensional program cannot handle rotations at continuous nodes, the beam is modeled by symmetry about the joint and a cantilever beam with an applied end moment is studied. Results for the response of a beam in vibration are presented showing displacement of the joint, relative rotation at the joint, and relative angular velocity at the joint; all versus time. Various clamping pressures and initial loads are explored. Diagrams of the beam shape versus time show the shape the beam takes on when slip occurs at the joint. Frequency calculations show that the priod of the response is affected by clamping presusre, but not by the initial loading. Energy loss calculations are presented for various clamping pressures. Keywords: Joint damping, Friction damping, and Coulomb damping.