Thermal ratchetting of straight pipe under alternating cold and hot thermal shocks with substained load, 1

Analytical study has been made on the thermal ratchetting of a straight pipe under alternating cold and hot shocks with the existence of constant axial load. The analytical method developed by Bree was used in this study. Firstly, it was shown that the present problem is equivalent to the fundamental problem analyzed by Bree with the existence of specific residual stress. Secondly, it was shown that if the residual stress was linearly distributed in the direction of thickness of pipe wall, this was effective only for the first several thermal shocks. Thirdly, it was found that the method applying alternating cold and hot thermal shocks to a specimen can obtain a large range of thermal stress with small temperature difference. Thus, the method giving alternating shocks is very effective for shortening the time required for the general thermal ratchetting experiments. Analysis was made separately for elastic region, shakedown region, plastic cycle region, and ratchet region. The equations for accumulated strain are given for respective regions, and the results of analyses are presented with many curves. (Aoki, K.)