Effect of Fastener Preload on Structural Damping

• Published in: Journal of failure analysis and prevention 2013-12, Vol.13 (6), p.744-747
• Main Authors: WEIWEI XU, HESS, Daniel P
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Friction-type joining (riveting, screwing, clamping, bending); Fundamental areas of phenomenology (including applications); Joining, thermal cutting: metallurgical aspects; Metals. Metallurgy; Physics; Solid mechanics; Structural and continuum mechanics; Vibration, mechanical wave, dynamic stability (aeroelasticity, vibration control...)
• ISSN: 1547-7029; 1864-1245
• DOI: 10.1007/s11668-013-9740-z

This paper presents results from an extensive set of frequency response measurements from a simple plate structure with a single bolt lap joint. The frequency response measurements are obtained from modal impact tests. Both damping ratios and natural frequencies are found to remain fairly constant for medium to high levels of bolt preload. At low levels of preload, damping ratios increase significantly by 25-75%, whereas natural frequencies decrease by only 1-2%. These results identify the monitoring of vibration damping as a means for detecting low preload and fastener loosening. Comparative tests with monolithic plate structures show the introduction of a single bolt lap joint results in an increase in damping and a decrease in frequency for the first three modes of vibration. Similar results are found for steel and aluminum plate materials with grade 5 and 8 fasteners.[PUBLICATION ABSTRACT]