| Budget Amount *help |
¥7,500,000 (Direct Cost: ¥7,500,000)
Fiscal Year 1986: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1985: ¥7,000,000 (Direct Cost: ¥7,000,000)
|
|---|
| Research Abstract |
Toe cracking is one of the most important cracking occurring on the welded fabrication in heavy steel constructions.This study is concerned the developement of the toe cracking reproducing test method and using this method,the effect of various factors affecting to the toe cracking is examined experimentally.
The test speciment is 300x130x30 mm size rectangular shape.During deformation by bending statically on one side of the specimen,multipass single beads are welded into the groove made on the opposite side on the specimen.Moreover,the specimen is cooled forcibly by water from its back side.Therefore,a large tensile strain is produced at the toe of the last bead for the superpose effect of restraining and thermal stress,and thus toe crack occurs.
Four pressure vessel steels and three covered electrodes were used in this experiment.After welding,penetrant testing is applied for the detect of cracking,and furthermore,on the cracked specimens,the fractgraphy by the scattering type electron microscopy,microstructures,hardness distributions and the shapes of the vicinity of the welded toe are examined.
As the test results,it is found that cracks are initiated mostly from the weld toe of first pass in the last layer,and propagated to the coarse grain boundaries.Stress concentration,rest raint,deep of groove and preheating affect to crack sensitivities,respectively.Above the studies,this testing method was confirmed as a simple reproducing device for the toe cracking of multipass welds in heavy steel plates.
|
