Free vibration analysis of pyroshock-loaded hardened structures

Abstract

The free vibration response of a high stiffness, high strength (hardened) structural member is characterized under a variety of energetic and simulated pyroshock system inputs. The hardened structure studied is a structural pipe which includes a reinforcing material, e.g., a composite potting, with threaded end caps. Impulsive loads are imparted on the structure using bulk explosives and non-energetic impacts. The free vibration response of the structure is measured using a variety of sensors (accelerometers and strain gages); the observed experimental modes are compared with computationally estimated and experimentally observed principle modes up to approximately 5 kHz. The operating (output-only) response of the system is also compared to show the effects of damaged reinforcing materials on the vibration frequencies and observed damping. The operating mode shapes also exhibit nonlinearities which are discussed, with possible explanations including rate- and amplitude-dependent damping. ©2010 Society for Experimental Mechanics Inc.