SEDL / STP / STP1250-EB / STP13990S

Equating Damped Vibration to Constant Amplitude Fatigue Loading for a Thick-Walled Pressure Vesselz

Stephens, RI
Professor and research assistants, The University of Iowa, Iowa City, IA

Adams, TB
Professor and research assistants, The University of Iowa, Iowa City, IA

Carlson, SL
Professor and research assistants, The University of Iowa, Iowa City, IA

Pages: 17    Published: Jan 1994

Download this paper for $25 PDF (288K)          View License Agreement
Abstract

A single impulse firing of an A723 steel thick-wall cannon tube has been considered by the U.S. Army to be equivalent in fatigue to a single 0.2 Hz laboratory simulated constant load amplitude test. However, a high frequency (15 kHz) resonant damped vibration has been found to accompany the firing in some situations and hence raise concern about the single loading equivalent simulation fatigue test philosophy. This case describes the analytical and test programs to determine a new fatigue equivalence that incorporates both the normal impulse, the resonant damped vibration, and the constant amplitude simulation tests. Analytical and experimental fatigue lives were based upon strain life (µ-N), stress-life (S-N), and linear elastic fracture mechanics LEFM (da/dN-ΔK) models. Quasi-equivalence testing was conducted between 0.2 and 30 Hz using both constant amplitude and a damped vibration spectrum with axial smooth specimens and SE(T) specimens. The analytical and experimental results, modified for frequency effects, provide a new fatigue equivalence with significant differences.