Dealing with cold cracking of welded joints, it is rather convenient to devide the type of joint into two; butt and fillet welded. For butt joint, many good research works have been done and detail in-formation of the joint during welding has been provided.
On the other hand, concerning cold cracks of fillet weld, many experimental researchs have been performed. With slight changes in the restraint for thermal deformation, various types of cracking have been observed, for example, at the toe and root, and under bead on the web side, and at the toe, heel and root on the flange side, etc., since local stress strain history may differ to a great extent.
In this paper, a series of theoretical analysis of elastic-plastic behavior of fillet weld of the first bead was performed under various restraining conditions for steel of 50 kg/mm
2 by the finite element method developed by one of the authors. Based on the results of the theoretical analysis, the following information was obtained.
(1) When the restraint for uniform contraction of web is low, possible weld cracks many occur at the toe, root, and heel on the flange side, on the other hand, when this restraint becomes higher, the crack initiation is considered to move on the web side, such as at the root, toe, of the weld of the web. When the restraint is extremely strong, crack initiates at the root on the web side and propagates to the toe on the flange side.
(2) When the restraint for rotation is low, the type of cracking is just similar to the previous case where the restraint for uniform contraction is low. When this restraint becomes severer and constrains free contraction along the flange, crack may be observed at the toe on the flange.
(3) When fillet weld is laid on both sides of T-connection, crack is liable to occur in the first fillet weld, since the restraint stresses of the second weld are superimposed on the residual stresses produced by the first one. And cracks may be located at the root on the web and the toe on the flange.
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