Characteristics of damping in components of a spot-welded frame

This paper describes a damping ratio for each component of a spot-welded frame composed of cold-rolled steel sheets. A spot-welded frame is used as part of an automotive body and a cabin of construction machinery. Their damping ratios need to be understood in design. The spot-welded frame is divided into spot-welded flange parts and other portions. Damping ratios of these components have been measured by impact tests. It was found that damping ratios of nonspot-welded sheet metals have little dispersion and are independent of frequency and shape. It was found that damping ratios of spot-welded flange members are related to the spot-pitch and thickness. Additionally it was found that a damping ratio of a spot-welded frame is smaller than that of a spot-welded flange member under the same parameters and is larger than that of a non-spot-welded sheet metal. It was found that the difference in their damping ratios depends on the shape of the non-spot-welded sheet metal portion in a spot-welded frame. The degree of the difference was clarified by our suggested method to evaluate the damping ratio of a spot-welded frame.