Abstract
A new test method has been proposed to evaluate bond's fracture toughness (δc) easily. Three points bend (BNP) specimens were extracted from welded test blocks with notch of poor penetration.
The tip of the notch in BNP specimen was located on a fusion line in modified-Vee joint. Three points bend tests have been made on weldments of three kinds of structural steels, and fracture toughness of bond has been measured over a wide temperature range using BNP test specimens. Results can be summarrized as follows;
1. To estimate the bond's toughness exactly, notch tip must be laid in the coarse grained HAZ zone, but it is wearisome to machine such notch.
2. The notch tip of the BNP specimen is precisely on fusion line, and it is easy to prepare BNP specimen.
3. Bond's toughness of BNP specimen largely depends on angular distortion of joint.
4. Temperature dependenceiof bond's toughness can be easily estimated with safety, by using BNP specimen welded under high bending constraint to prevent the occurence of angular distortion during welding.
