Effect of Plate Thickness on Fracture Toughness by Means of Elastic-Plastic Fracture Mechanics

Abstract

The effect of plate thickness on fracture toughness in terms of J-integral concept, J_c, has been investigated using a heavy section A533B steel (165mm in thickness) which has highly uniform toughness in thickness direction except for surface layer. Notched bend specimens were prepared from this uniform region by varing thicknesses from 3mm to 100mm in order to minimize the metallurgical effects and tested at various low temperatures.
The results are summarized as follows:
(1) A new, simple technique of J_c estimation is proposed. According to this method, J_c values can be easily obtained using only the information from COD test which is represented by fracture load and critical clip gage displacement.
(2) There exists an evident effect of plate thickness on fracture toughness in cleavage fracture. Using K_C which is converted from J_c, the effect is formulated as follows:
K_IC=K_C/ (1+2.3β_C) ¹/², β²_C= (K_C/δ_Y) ²/B
where K_IC is plane strain fracture toughness and K_C is fracture toughness at plate thickness of B. δ_Y is yield stress.