ABAQUS user subroutines for the simulation of viscoplastic - loicz

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Fig. 3. Contour plots of the maximum principal damage for β = 0.1, 0.5 and 1.0.
Other experimental investigations of KOBAYASHI et al. show that under relatively low loads, σ2, creep
voids nucleated on a plane inclined by about 45° against the tensile direction. Though pure aluminium
was used in these tests for which no material data exist, the experiments motivated the simulation of the
damage behaviour at a lower creep load of σ2 = 100 MPa for the present Ni-based alloy and β = 0.1.
The contour plots of the second direction cosine of the principal direction corresponding to DI,
D
cos∠( n ,e2 I ), at t = 11000 hours and the maximum damage distribution at t = 11000 and
12000 hours, respectively, are shown in Fig. 5. The values of the direction cosine at the location of
maximum damage, i.e. where local fracture will occur, is −0.7÷−0.8. That means that maximum principal
damage is inclined at about 45° against the tensile direction, which indicates that cracks may form a
cone-type fracture surface. Once the meso-crack has been formed or even local fracture has been taken
place, the local behaviour of the material will strongly depend on the shape and size of the crack. Further
experimental investigations are needed.