Evaluation method of damping ratio for spot-welded frame

The purpose of this study is a purpose to construct the cab model of the construction machinery that design engineer is able to carry out the dynamic analysis, especially frequency response analysis, in conceptual design stage easily. As a previous step of the frequency response analysis for the cab model, evaluation method of damping ratio for spot-welded frame was suggested in this paper. First, the impulse excitation experiments for three types of test pieces, flat type, hat type, and spot-welded frame, were carried out to investigate the difference of those damping ratios. Next, it was considered that damping was mainly caused by friction of spot-welded points in the flange. Then, it was assumed that all of energy loss by friction damping was converted to the heating energy. Therefore damping ratio could be identified by measuring the temperature difference by using the thermography, as single degree of freedom for a spot pitch. As a result, it was clarified that damping ratio for spot-welded frame was dependent on frequency and acceleration.