Vol.11, No1, 2011, pp.51-56
UDC  66.011-034.1 : 519.711-034.1

NUMERICAL SIMULATION OF CONSTRAINT EFFECT ON FRACTURE INITIATION IN WELDED SPECIMENS USING A LOCAL DAMAGE MODEL

B. Younise1, M. Rakin2, N. Gubeljak3, B. Medjo2, A. Sedmak1

1) University of Belgrade, Faculty of Mechanical Engineering, Belgrade

2) University of Belgrade, Faculty of Technology and Metallurgy, Belgrade

3) University of Maribor, Faculty of Mechanical Engineering, Maribor, Slovenia

Abstract

In this paper, two micromechanical models: the Gurson-Tvergaard-Needleman (GTN) model and Complete Gurson Model (CGM) are used to predict ductile fracture initiation of two different welded specimens, SE(B) and C(T). The effect of strength mismatch and weld metal width on fracture initiation is studied also. High strength low-alloyed (HSLA) steel welded specimens are analysed, with the pre-crack length/specimen width ratio a0 /W = 0.32. Two different weld metals with two different widths: 6 and 12 mm are used to make strength overmatch and undermatch joints. Numerical analysis is done previously to adopt Gurson parameters and to determine the values of critical void volume fraction (fc), which are used in the prediction of crack growth initiation in the two welded specimens. Crack tip opening displacement and J-integral at crack growth initiation (CTODi and Ji) are estimated using the GTN and CGM models. Transferability of fracture initiation parameters (CTODi and Ji) between the two welded specimens is analysed based on stress triaxiality in front of the crack tip.

Keywords: stress triaxiality, void volume fraction, ductile fracture, transferability

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