C. Ruggieri et al., NUMERICAL MODELING OF DUCTILE CRACK-GROWTH IN 3-D USING COMPUTATIONALCELL ELEMENTS, International journal of fracture, 82(1), 1996, pp. 67-95
This study describes a 3-D computational framework to model stable ext
ension of a macroscopic crack under mode I conditions in ductile metal
s. The Gurson-Tvergaard dilatant plasticity model for voided materials
describes the degradation of material stress capacity. Fixed-size, co
mputational cell elements defined over a thin layer at the crack plane
provide an explicit length scale for the continuum damage process. Ou
tside this layer, the material remains undamaged by void growth, consi
stent with metallurgical observations. An element vanish procedure rem
oves highly voided cells from further consideration in the analysis, t
hereby creating new traction-free surfaces which extend the macroscopi
c crack. The key micro-mechanics parameters are D, the thickness of th
e computational cell layer, and f(0), the initial cell porosity. Calib
ration of these parameters proceeds through analyses of ductile tearin
g to match R-curves obtained from testing of deep-notch, through-crack
bend specimens. The resulting computational model, coupled with refin
ed 3-D meshes, enables the detailed study of non-uniform growth along
the crack front and predictions of specimen size, geometry and loading
mode effects on tearing resistance. here described by J-Delta a curve
s. Computational and experimental studies are described for shallow an
d deep-notch SE(B) specimens having side grooves and for a conventiona
l C(T) specimen without side grooves. The computational models prove c
apable of predicting the measured R-curves, post-test measured crack p
rofiles, and measured load-displacement records.