No abstract

No abstract

No abstract

No abstract

A B S T R A C T The paper presents four equations for Fatigue Crack Growth Rate (FCGR) description taking into account J, CTOD, CMOD and K. CT specimens made of steel were tested for different values of stress ratio (R) by P = constant method. The influence of Rratio has been studied on crack propagation and crack initiation region. The experimental results show that J and CTOD, contrary to K and CMOD which are constant in R-ratio variations, vary with the variations of R-ratio in the range R = 0.3-0.6. Therefore, there is no need to enter R parameter directly in the well-known Paris equation if J or CTOD parameter is used instead of K in this equation. The constants of these equations are independent of loading unlike the constants of Paris equation. a = crack length A = constant coefficient in the equation A pl = plastic component of area under load-displacement curve b 0 = initial ligament (W − a 0 ) B = specimen thickness B * = characterize the material property (independent of stress ratio) C , C 0 , C 1 , C 2 , C 3 = material constant (constant coefficient in the equations) CMOD = crack mouth opening displacement CMOD max /CMOD min = crack mouth opening displacement value under maximum/minimum load level CTOD = crack tip opening displacement CTOD max /CTOD min = crack tip opening displacement value under maximum/minimum load level CTOD e /CTOD p = elastic/plastic component of crack tip opening displacement da dN = fatigue crack growth rate d s = arc length E = material elastic modulus G = energy release rate J = J-integral J el /J pl = elastic/plastic component of J-integral J IC = ductile fracture toughness J max /J min = J-integral value under maximum/minimum load level