Elastic‐plastic Fracture Mechanics for Pressure Vessel Design

Abstract

The project has been concerned with the verification of the J-philosophy for initiation and growth of cracks on laboratory type specimens as well as on larger surface cracked plates. The analysis of the experiments involved extensive fully three-dimensional finite element calculations. It was found that the.initiation events for the six surface cracked plates occurred at approximately the same J-value. A corksponding relation to the laboratory type specimen was less successful, mainly because of the short-comings of current methods for J,,-evaluations. A somewhat puzzling feature of the surface crack experiments was that unstable crack growth occurred immediately after crack growth initiation in four out of six tests, while some amount of stable crack growth was evident in the remaining two and in all of the laboratory type specimens. An evaluation of the surface experiments by a type of Rdanalysis was also performed. Using as K,, the mean value from the surface crack experiments, it was found that the R6-method yielded conservative predictions. NOMENCLATUREJ = path-independent integral JD = deformation theory value of J JF = flow theory value of J J, = critical value of J JQ = provisional critical value of J J,, = averaged value of J Au = crack growth increment P = load K, = stress-intensity parameter in the R6-method L, = limit load parameter in the R6-method P, = limit load JR = resistance value of J Kl = stress intensity factor K,, = critical value of the stress intensity factor K, = fracture toughness w = deformation work density n, = unit normal vector ui = displacement vector crii = stress tensor E~ = strain tensor C = integration contour A = integration surface s = line coordinate along crack front r = distance from crack border E = Young's modulus v = Poisson's ratio uY = yield strength N =tensile normal load M = bending moment g = non-dimensional constant in J-evaluation formula VJ = specimen width 73 74 FRED NILSON et al. t = specimen thickness 6 = specimen displacement 6 , = plastic part of specimen displacement a, = initial crack length @ , = plastic part of specimen rotation & = initial slant angle e = initial offset a = crack depth I = crack length a = aspect ratio of crack axes y = relative crack depth N, = limit normal force

Modeling ductile to brittle fracture transition in steels—micromechanical and physical challenges

“…All the experiments on this material taken from a decommissioned 20-year old chemical reactor were performed at room temperature, which falls in the middle of the DBT interval determined from Charpy tests (Nilsson et al 1992). The tensile properties of the material were: σ Y = 300 MPa, UTS = 530 MPa.…”

An experimental and numerical investigation of ductile crack growth characteristics in surface cracked specimens under combined loading

“…It should also be mentioned that h is rather uniform over a large part of the crack front in the CT specimen, though drastically decreasing when approaching the side groove (2]z[/BN --+ 1).…”

“…The first two conditions, (2) and (3), ensure that the elastic unloading and the non-proportional plastic loading associated with crack advance will take place in a zone characterized by J. The first two conditions, (2) and (3), ensure that the elastic unloading and the non-proportional plastic loading associated with crack advance will take place in a zone characterized by J.…”

“…This material has been the main material in a large Nordic cooperation project [29] and also in [1]- [2]. This material has been the main material in a large Nordic cooperation project [29] and also in [1]- [2].…”

“…This material has been the main material in a large Nordic cooperation project [29] and also in [1]- [2]. 2 in [2]). The test temperature in the present study was 60 ° C, at which the material is expected to exhibit fully ductile behaviour (cf.…”