This paper develops a new procedure for the fracture toughness requirement of materials. A new concept, equivalent CTOD concept, is introduced on the basis of the Local Approach. The equivalent CTOD is defined by the CTOD of the fracture toughness specimen, at which the fracture toughness specimen gives a compatible Weibull stress with the structural component of concern. Numerical analyses in the large scale yielding condition indicate that the equivalent CTOD is much smaller than the CTOD of a wide plate component. This implies that the required fracture toughness which is to be achieved in the fracture toughness test can be relaxed to a large extent, compared to the conventional toughness specification. Major factors controlling the equivalent CTOD are the work hardening property of materials and the size and type of a crack assumed in the structure. A high yield-to-tensile ratio and a short/deep crack lead to a low equivalent CTOD. The validity of the equivalent CTOD concept is verified through the transferability analysis of fracture toughness results to the fracture performance evaluation of welded joints.
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