Experimental investigation of damping characteristics of bolted structural connections for plates and shells.

Abstract

Reducing the contact force in bolted structural connections can reduce system vibration amplitudes by enhancing joint damping capacity. A test model consisting of two concentric circular cylindrical shells and four vanes connected by groups of bolts was tested and analyzed to investigate the relationship between the contact force and the system damping. A viscoelastic material was then introduced between the contacting surfaces and its effect on systems damping were again investigated. Experimental results show that resonant frequencies of modes whose mode shapes provided the most differential motion at the joint connection were shifted down in frequency and the damping increased. This damping increase and frequency shift continued as contact force was reduced until the structural joints moved into the total slip regime where the response becomes nonlinear. The maximum damping and maximum frequency shift were obtained just prior to this total slip. The greatest increase in damping was achieved with the introduction of viscoelastic material between contact surfaces. This damping material also postponed the transition from microslip to macroslip.