On the Study of Restraint and Residual Stress due to Welding on Erecting Butt Joint of Ship's Hull (Report No.1)

Abstract

The new proposed experimental “Restrained-Joint” method, includes a reproductive condition which tboth ends of plate are fixed in perfect rigid. The distance between both rigid ends fixed, we call it restrained distance, are always let constant.For this purpose, a gauge with a dial indicator that is equal to restrained distance, is set, and the ensile loading suffered from the both of plate that are bitten by chuck of the Mohr tension tester, are as well as controlled in quick responsible to maintain the gauge length constant. Due to the experiments carried out, it could be considered that so-called intensity of restraint was equivalent to the reaction stress which was obtained by this loading test method.Hence. 400 mm breadth, 20 mm thickness of plate and 300, 400, 600, 850 and 1, 000 mm restrained distance, the condition was appreciable for varios restraint intensity, and 3. 7 and 12 mm root openings was used to find effect of excessive root opening and the material for every specimens was SM-41 (mild steel).Thus, the obtained results was summarized as follows.1. Expanding and shrinking region upon restrained condition, plastic and elastic deformating zone in adjacent butt joint was clarified.2. Some excessive root opening not hardly effected on intensity of restraint and amount of locken-in stress residual welding stress on restrained butt weld, was found.3. The intensity of restraint could be varied by various restrained distances, in 400 mm and the less was increased abruptly but in 600-1, 000mm. restrained distance-intensity of restraint curve had a gently-slope.4. Longitudinal residual welding stress along weld line on butt weld was decreased and transverse locked-in stress due to welding was increased by increasing of restraint, was appeared. The increased amount of transverse locked-in stress from free joint (no restraint) was almost equal to the intensity of restraint i. e. reaction stress value measured by the test.5. Reaction stress of each passes during multi-pass welding showed a maximum value when weld metal was deposited 30-40% throat per full thickness of plate.6. At the condition t =20 mm, b=100 mm and R. D =850 mm it was a significant result that the reaction load was measured by tester as large approximately 130 Tons according to this experiments.