Two-parameter fracture criterion (K ρ,c -T ef,c ) based on notch fracture mechanics

Abstract

A two-parameter fracture criterion has been proposed to predict fracture conditions of notched components. This criterion includes the critical notch stress intensity factor K ρ,c , which represents fracture toughness of a material with a notch of radius ρ, and the effective T -stress. The effective T -stress T e f has been estimated as the average value of the T -stress distribution in the region ahead of the notch tip at the effective distance X e f . These parameters were derived from the volumetric method of notch fracture mechanics. The results of numerical T e f,c -stress estimation are compared to the T e f,c -stress results obtained from experimental analysis. The material failure curve or master curve K ρ,c = f T e f,c has been established as a result of the notched specimen tests. A large T e f,c range was covered from −0.80 σ Y to +0.19 σ Y using SENT, CT, RT (roman tile) and DCB specimens. It was shown that the notch fracture toughness is a linear decreasing func-

Design based on ductile–brittle transition temperature for API 5L X65 steel used for dense CO2 transport

“…Specimen geometry T-stress and associated transition temperature. For that purpose, it is necessary to obtain the "material master curve" which is the relationship between fracture toughness and constraint and effective T-stress (T ef ) at critical pressure for a test according to the procedure described in [13]. Unfortunately, these data are not yet available for X 65 and an estimation has been evaluated on the basis of the API 5L X52 pipe steel and a pipe diameter of 610 mm and thickness equal to 5.8 mm.…”

A two-parameter approach to assessing notch fracture behaviour in clay/epoxy nanocomposites

“…Hadj Meliani et al [26] have also pointed out this effect on the notch fracture toughness K ρ ,c with the critical constraint T ef,c described by the critical value of the T ef,Xef parameter. The authors found a linear relationship between the two parameters:…”

“…The shift in the stress distribution is introduced into the plastic constraint. In the literature, we can note the following constraint parameters: the plastic constraint factor [23], the stress triaxiality [24], the Q parameter [25], T stress [26] and A 2 [27].…”

“…9. The procedure is based on William's asymptotic solution[36] for crack tip strains in the vicinity of a mode I crack in a planar elastic body and gauge measurement technique proposed by Hadj Meliani et al[26] for evaluating Tstress under static loading directly from experiments. William's asymptotic description for radial strain ε rr in the angular direction can be expressed as polar coordinates (r, θ) rotated by an angle αas follows:…”

Nonlocal criterion of bridged cracks growth: analytical analysis

“…In such cases, the fracture conditions are considered not only at cracks tips, but also in some zones in the vicinity of flaws, taking into account stresses induced by crack surfaces interaction in these zones. Nonlocal fracture criteria, which can be used in these cases, have been intensively developed recently, see [4][5][6][7][8][9][10]. These criteria are based, as a rule, on two fracture conditions for the crack tip advancing (the stress and energy conditions in [4][5][6], the critical stress intensity and the T -stress in [7], and the finite fracture mechanics conditions in [8][9][10]), but they were implemented for cracks without consideration of large-scale process zone effects.…”