A NUMERICAL INVESTIGATION ON THE GEOMETRY DEPENDENCE OF THE CRACK-GROWTH RESISTANCE IN CT SPECIMENS

The influence of the specimen thickness B and the ligament length b on the J(R)-curves is numerically investigated for CT specimens. The thi ckness effect is taken into account with 2-D analyses by dividing a pl ain sided specimen into a plane stress part and a plane strain part. T he fracture process is controlled by experimentally determined critica l values of the crack tip opening displacement for crack growth initia tion (CTOD(i)) and the crack tip opening angle for stable crack growth (CTOA(C)). It is shown that for the global behaviour of a plain sided specimen, the B/b ratio is essential. The difference between the geom etry dependence of the initiation value of the J-integral and the geom etry dependence of the slope of the J(R)-curves is also shown.