任意板厚の斜めY形溶接割れ試験片の力学的特性

抄録

Welded structures are inevitably accompanied by deformation and residual stresses produced by construction, which sometimes cause initiation of various types of weld cracking. In order to avoid the weld cracking, the y-Groove cracking test specimen has been widely used as the cold cracking sensitivity specimen to determine appropriate materials and welding conditions.
In this paper, the dynamical characteristics of the y-Groove cracking test specimen of arbitrary thickness are clarified by discussing the restraint stresses and strains produced in this specimen for general cases of welding where the size of the specimen changes and heat input varies. The results are as follows:
(1) For evaluation of restraint stresses and strains produced perpendicular to the weld line in the weld metal of a y-Groove cracking test specimen, the analytical calculation method which was already presented for comparatively thin plates is extended for thicker plates. Then, the restraint stresses and strains under the influence of the ratio of plate thickness to throat thickness can be analytically calculated without conducting three dimensional elastic-plastic analysis.
(2) The magnitude of restraint stresses and strains produced in a slit weld specimen vary with the amount of heat input, that is, they are dependent on the ratio of l/hcr. Judging the severity of the dynamical condition of the specimen from the magnitude of restraint stresses and strains, the infinite plate is the severest. The infinite plate may be replaced by a finite plate of which size ratio is (B/l≥4.0, L/l≥3.7). Then, the size ratio of the y-Groove cracking test specimen is not necessarily the severest.
(3) Among the slit weld specimens with the same size ratio as the y-Groove cracking test specimen, the actual size of the y-Groove cracking test specimen achieves the severest dynamical condition for the specific heat input Q=17000J/cm.
(4) When the thickness of the y-Groove cracking test specimen increases, the restraint strain (the sum of the elastic and plastic components) produced in the weld metal of the first pass also increases. However, the increasing tendency saturates at the plate thickness of approximately h=50 mm. From this fact, the necessary plate thickness for the specimen is 50 mm to determine the welding condition for the first pass of very thick plates.
(5) For the slit specimen (B/l=1.875, L/l=2.5), the plastic restraint strains increase with an increase of the effective average restraint intensity (Rp)η, and their increasing tendencies are very similar (in Fig. 6). Therefore, (Rp)η may be used as a simple dynamical measure to compare the severity of the dynamical condition in place of the restraint strain.