Numerical simulation of constraint effect on fracture initiation in welded specimens using a local damage model

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 analyzed, with the precrack 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 analyzed based on stress triaxiality in front of the crack tip.

U ovom radu, primenjena su dva mikromehanička modela: Gurson-Tvergard-Nidlman (GTN) model i Potpuni Gurson model (CGM) za procenu inicijacije duktilnog loma kod dve različite zavarene epruvete, SE(B) i C(T). Uticaj mismečinga čvrstoće i širine metala šava na inicijaciju loma je takođe proučen. Analizirani su zavareni uzorci od niskolegiranog čelika povišene čvrstoće (HSLA), sa izvedenom prslinom, dužina prsline/širina epruvete a0/W = 0.32. Upotrebljena su dva različita metala šava sa dve širine: 6 i 12 mm radi izvođenja overmečing i andermečing spojeva. Prethodno je urađena numerička analiza radi usvajanja Gurson parametara i određivanja vrednosti kritičnog zapreminskog udela šupljine (fc), koji su iskorišćeni za predviđanje inicijacije rasta prsline u obe zavarene epruvete. Pomeranje pri otvaranju vrha prsline i J integral pri inicijaciji rasta prsline (CTODi i Ji) su sračunati prema modelima GTN i CGM. Transferabilnost parametara inicijacije loma (CTODi i Ji) između obe zavarene epruvete je analizirana na osnovu troosnosti napona ispred vrha prsline.