Assessing Fracture Toughness for Welded Joints of KAS Steel with Crack-like Weld Flaws

Abstract

The role of crack-like weld flaws has been studied on fracture toughness of welded structures. Tensile tests were conducted at low temperature with small size specimens taken from MIG welded joints of KAS steel including lack of penetration, surface flaw, embedded flaw or through thickness flaw.
The main results are summarized as follows:
(1) Critical J-values Jc obtained through Rice's equation depended on the flaw shape and flaw size for σnc>σY and sensitively increased with increase of temperature when ρ_c>b
(2) The relationships between Jc and critical elongation e_c were analytically led out and have been experimentally confirmed;
σnc<σY J_c/eyσ_Y =πa( e^*_c/e_Y )² σnc>σY J_c/e_Yσ_Y =lo( e^*_c/e_Y -0.5)
e=h/l₀ a<<;B, W
where σ_nc: fracture net stress, σ_Y: yield strength, ρ_c: critical length of plastic zone, b: ligament width, h: displacement, i_o: gauge length, 2_α: crack length, ep: yield strain, B: specimen thickness and W: specimen width.