Crack initiation and propagation close to the interface in a ferrite-austenite joint

International audienceThe safety assessment of welded structures and joints still remains an important industrial problem. In this study, a simple diffusion bonded bi-material joint has been made in order to analyze the plastic mismatch effect. It consists of an assembly of ferritic and austenitic steels which are representative of nuclear pressure vessel components. Tests were performed on various specimens including smooth and notched tensile bars, Charpy V-notch specimens and single-edge notch bend specimens. Homogeneous and bimaterial specimens were tested. On deeply notched specimens, the effect of the distance between the notch root and the interface on fracture initiation and crack propagation direction was studied. Tests were modeled using elasto-plastic finite element simulations. These simulations were post-processed in order to determine crack initiation based on the Rice and Tracey criterion according to the “local approach of fracture” procedure

Effect of weld metal mis-matching on crack driving force

This paper presents the results of a comparative study on the application of CTOD and J design curves as well as the Engineering Treatment model for Mis-Matched joints (ETM-MM) procedures to mis-matched weld joints. Inhomogeneous through thickness centre-cracked tensile (CCT) panels are prepared by electron beam welding (EBW) a transverse strip of austenitic steel of 18 mm height to the middle of the panel of another austenitic steel of different mechanical properties. The crack tip opening displacement (CTOD) and the experimental J values obtained from such bimaterial panels which simulate the 20 percent undermatched (UM) and 25 percent overmatched (OM) welds are compared with those predicted by the three above-mentioned procedures. Design curves, developed to predict the failure of homogeneous structure, only use the mechanical properties of one material as an input. Moreover, the predictions of such procedures are very sensitive to the mechanical properties and applied strain definitions. Therefore, the significance of the choice of the mechanical properties (weld or base metal properties) to be used in those procedures on the predictions of the crack driving force are discussed. In contrast to the design curves, the recently developed ETM-MM for welded structures includes the mechanical properties of the weld and base metal. Its predictions of the CTOD (#delta#_5) are compared with the experimental results. The mechanical properties of the base or weld metal in the design curves have no significant influence on crack driving force predictions for undermatched specimens. In contrast, for overmatched specimens, the use of mechanical properties of the base metal provides conservative predictions. The predictions obtained using ETM-MM are reasonably conservative for small cracks in an undermatching weld. (orig.)Reprinted from: Mis-Matching of Welds, ESIS 17 (edited by K.H.Schwalbe und M.Kocak) 1994, Mechanical Engineering Publications, London, pp.589-607 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Defect assessment in weld including mismatch

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : 26165 A, issue : a.1998 n.3 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Prediction of overmatching effect on the fracture of austenitic stainless steel

SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : 26165 A, issue : a.1995 n.178 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Evaluation experimentale de J par l'aire sous la courbe force-deplacement pour les eprouvettes SENB ou CCT homogenes ou en situation d'overmatching

Available at INIST (FR), Document Supply Service, under shelf-number : 26165 A, issue : a.1996 n.148 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Performance of strength mis-match welded joints: comparison of experimental and numerical results

Two 70 mm thick 316L austenitic plates have been butt-welded using a TIG welding process. The weld metal yield strength is more than twice the base metal yield strength. From this overmatched weld, 25 mm thick Compact Tension (CT), Single Edge Notched Bend (SENB) and Center Cracked panels in Tension (CCT) specimens (a/W=0.5) have been prepared and tested at room temperature. The crack was located in the middle of the weld metal. Those experiments have been modeled by 3D finite element calculations using the Aster code developed at EDF. This paper presents the comparison between the experimental and the numerical results in terms of load, load line displacement, crack mouth opening displacement (CMOD) and crack tip opening displacement (CTOD) measured experimentally using the #delta#_5-clip developed at GKSS. FE calculations and experimental results are in good agreement. Moreover, the J and CTOD (#delta#_5) resistance curves determined on those various specimens are compared. The CTOD (#delta#_5) resistance curve of the CCT specimen is higher than those of the bending specimens (SENB or CT). In contrast, the J resistance curves of all the specimens are similar when J is evaluated correctly. (orig./MM)First published in: Schwalbe, K.H.; Kocak, M. (eds.): 2. International symposium on mis-matching of interfaces and welds, performance of strength mis-matched welded or bonded joints. GKSS, Geesthacht (DE), 1997, ISBN 3-00-001951-0, pp. 771-780Available from TIB Hannover: RA 3251(97/E/44) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Analyse de l'integrite des composants soudes fissures

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : 26165 A, issue : a.1998 n.42 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Evaluation experimentale de J par l'aire sous la courbe force-cmod pour les eprouvettes SENB et CCT fissurees au milieu d'un joint soude

SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : 26165 A, issue : a.1997 n.06 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Cerebral lupus erythematosus responding to plasmaphaeresis A. RIGLAR ¶

Summary A 44-year-old nurse with a 12-year history of systemic lupus erythematosus developed a schizophrenialike psychosis due to cerebral lupus. Prednisolone in doses up to 200 mg daily was ineffective. Levels of immune complexes by the Raji cell assay were greatly increased in serum and cerebrospinal fluid. Plasma exchange was performed on 4 occasions over 4 days

Performance des jonctions soudees en situation de mismatching : comparaison entre resultats experimentaux et numeriques

SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : 26165 A, issue : a.1997 n.08 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc