供用下にある構造物の溶接施工に関する研究 （第二報） 変動荷重下の擬凝固割れに対する力学的検討

Abstract

Repair works by welding on the structures in service condition are often done under the pulsating loads. In this study, the deciding method of the initiation of quasi-solidifiaction crack was investigated by using the results of hot weld crack test under the pulsating loads. Moreover, hot crack was considered from a mechanical point of view. The main results are as follows.(1) The equation for the initiation condition of quasi-solidification crack under the pulsating loads was shown. Moreover, based on it, the equation to decide the initiation of quasi-solidification crack was also shown, in which relative root gap opening displacement, Δδ, that can be easily measured before welding was used as a practical mechanical measure.(2) For the case that the uniform pulsating loads are applied, the practical deciding equation for the initiation of quasi-solidification crack was shown in non-dimensional form. Moreover, applying it to the result of hot crakc test, the validity was concretely shown.(3) Without distinction between solidification and quasi-solidification crack under the pulsating loads, the critical strain curve for hot crack of weld metal used in this study was shown.(4) The main mechanical factor was the product of repeat number of times and Δδ by the external loads concerning the solidification crack and was the opening rate of root gap and the magnitude of Δδ in a cycle concerning the quasi-solidification crack.(5) The concrete procedure to apply the evaluating equation for hot crack, that is solidification and quasi-solidification crack, was shown. Besides, so far as the evaluating equation proposed in this paper is used, critical strain of each crack is not necessary to be obtained.