JIC evaluation and effective thickness of thin specimens with and without side-grooves

Effects of side‐groove depth on creep crack‐tip constraint and creep crack growth rate in C(T) specimens

“…A large number of numerical and experimental studies have indicated that crack‐tip constraint can remarkably affect fracture behavior of materials . Under elastic‐plastic conditions, there are some studies on the effects of side groove on constraint, fracture parameter, stress, and deformation states in the side‐grooved specimens . It has been shown that side grooves in fracture specimens can significantly alter the distributions of displacement, strain, and stress along the crack‐front, thus affect crack‐tip constraint level and fracture behavior of materials.…”

“…1 Under elastic-plastic conditions, there are some studies on the effects of side groove on constraint, fracture parameter, stress, and deformation states in the side-grooved specimens. [2][3][4][5][6][7][8] It has been shown that side grooves in fracture specimens can significantly alter the distributions of displacement, strain, and stress along the crack-front, 2 thus affect crack-tip constraint level and fracture behavior of materials. Under creep condition, many experimental, theoretical analyses, and numerical simulations have been conducted to investigate creep crack initiation and growth, with the results showing that crack-tip constraint Nomenclature: a, crack depth; a 0 , initial crack depth; _ a, creep crack growth rate; _ a 0 , creep crack growth rate of the standard plane strain specimen; A, constant in Norton creep model; A 1, A 2 , constants in 2RN creep model; A c , unified characterization parameter of in-plane and out-of-plane creep constraint; A CEEQ , area surrounded by equivalent creep strain isoline; A ref , area surrounded by equivalent creep strain isoline in a standard specimen; B, specimen thickness; B n , net specimen thickness; C * , C * integral analogous to the J integral; C 1 * , C * value in cracked specimen or component; C 2 * , C * value in standard reference C(T) specimen in plane strain; C * avg , average C * integral; E, Young 0 s modulus; F, applied load; h, stress triaxiality factor; H, factor to estimate C * in experiment using load line displacement; K in , initial stress intensity factor; L, characteristic length; n, stress exponent in Norton creep model; n 1 , n 2 , stress exponents in 2RN creep model; Q, constraint parameter under elastic-plastic or creep condition; r, distance from a crack tip; R, creep constraint parameter; R*, load-independent creep constraint parameter; t, creep time; t red , creep redistribution time; T z , out-of-plane constraint parameter; W, specimen width; z, distance from specimen center along specimen thickness; _ ε c , creep strain rate; ε Ã f , multiaxial creep ductility; ε f , uniaxial creep ductility; ε c , equivalent creep strain; σ 0 , normalizing stress, usually taken as yield stress; σ 22 , opening stress; σ 22,CT , opening stress of C(T) specimen under plane strain; σ e , von Mises effective stress; σ m , hydrostatic stress; σ y , yield stresses; ω, damage parameter; _ ω, damage rate; η, factor to estimate C * in experiment using load line displacement; _ Δ, load line displacement rate Abbreviations: 2-D, two-dimensional; 2RN, 2-regime Norton; 3-D, three-dimensional; C(T), compact tension; CCG, creep crack growth; CEEQ, equivalent creep strain in ABAQUS code; FEM, finite element method; SDV1, equivalent stress; SDV2, stress triaxiality; SDV3, damage contours can significantly influence CCG rate.…”