3-D elastic-plastic investigation of fracture parameters in side-grooved compact specimen

Surface and interior stress intensity factor measurement by a random speckle method

“…When plane strain value of K is used for the calculation, the SIF reduces an amount of 23 percent at the free surface and most of this reduction is confined to a layer about 0.5 cm thick. This result agrees well with the finite element calculations of deLorenzi and Shih [10], where a reduction of 20 percent was found in spite of the fact that both the specimen geometry and loading condition were different and the Poisson's ratio used was 0.3 (as against 0.36 in the present study). Experimental studies [10,12] using frozen stress photoelasticity reveal a reduction of about 40-50 percent depending on specimen geometry and loading configuration (the value on the free surface can only be estimated by extrapolation).…”

“…This result agrees well with the finite element calculations of deLorenzi and Shih [10], where a reduction of 20 percent was found in spite of the fact that both the specimen geometry and loading condition were different and the Poisson's ratio used was 0.3 (as against 0.36 in the present study). Experimental studies [10,12] using frozen stress photoelasticity reveal a reduction of about 40-50 percent depending on specimen geometry and loading configuration (the value on the free surface can only be estimated by extrapolation). The result of using moire on annealed photoelastic slices [12] shows a difference of about 30 percent when plane strain is assumed for all slices including the surface slice, and a variation of about 50 percent when plane stress is assumed at the surface slice.…”

“…In the present study, we have used the plane strain value of • for all the interior sections and both the plane strain and plane stress values of tc for the free surface SIF determination. This is done so as to compare with some numerical results [10]. In our experimental evaluation of K~, we selected the displacement data along the crack mouth (i.e.…”

A framework to correlate a/W ratio effects on elastic-plastic fracture toughness (J c )

“…is the trace of the stress tensor and 6ij is the Kronecker delta. Details of the numerical implementation follow those described by de Lorenzi and Shih [29]. The finite-element analyses for each configuration are repeated for three levels of strain hardening, high (n = 5), moderate (n = 10), and very low (n = 50), The parameter ~ is assigned a value of 1.…”

Application of fracture toughness scaling models to the ductile-to- brittle transition

“…The specimens used in this investigation had side-grooves to help control the crack front straightness during ductile crack extension. The sidegrooves have been shown [12] to promote plane strain behavior, but the effects of the sidegrooves has not been explicitly incorporated into the development of the scaling models. Observations of the fracture surfaces of the short crack specimens did not indicate that the cleavage initiation sites were influenced by the side-grooves.…”