ABAQUS user subroutines for the simulation of viscoplastic - loicz

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16 −1 −1 D1 = 0 , L1 = 0, Z i1 = 0 (i = 1, 2,3) . (24a-c)
5. User material routines and their applications The material models mentioned above are implemented into the commercial FE code ABAQUS as user-defined material model by writing the corresponding user subroutines, UMAT, see Table 1. With help of these UMATs one can apply the models in an FE analysis of viscoplastic damage behaviour of engineering components and structures. All the routines are written in the computer language FORTRAN using the forward integration algorithm for numerical integration. Only isothermal loading conditions have been considered and the damage deactivation has not been included in any of the routines. Viscoplastic FE calculations are very time consuming. In the routines however, no automatic time step control is used, so that there is a necessity to improve the respective algorithms. All examples presented below are conducted using ABAQUS/Standard 5.8. model UMAT CHABOCHE model coupled with damage d-chaboche.f BODNER-PARTOM model coupled with damage d-bodner.f anisotropic creep and damage model of BERTRAM, OLSCHEWSKI & QI d-scsrr99.f Table 1: Constitutive models and names of the respecitve UMATs 5.1 Circumferentially notched bar — CHABOCHE model coupled with damage The material parameters of the CHABOCHE model of IN 738 LC have been determined by OLSCHEWSKI et al. [1990] and their values at 850 °C are shown in Table 2. The material parameters of the damage model were estimated by using numerical optimization methods to fit the creep data of the three creep tests presented in the work of OLSCHEWSKI et al. [1990]. During this process the above values of the parameters of the CHABOCHE model were kept constant. Table 3 shows a set of damage parameters for IN 738 LC at 850 °C. Note that just three uniaxial tests are not sufficient for parameter identification, so that the values given in Table 3 are only first estimates. For lack of biaxial test data, the anisotropy parameter β can not be determined. Comparison of the experiments and the predictions by the CHABOCHE model and by the coupled model with damage, respectively, using the material 17
Page 1 and 2: Technical Note GKSS/WMS/01/5 intern
Page 4 and 5: 0. Nomenclature 3 1. Introduction 7
Page 6 and 7: R ∞ Wi Z I , Z D Zij 6 saturated
Page 8 and 9: W internal variable, eq. (20b) four
Page 10 and 11: where S is the CAUCHY stress tensor
Page 12 and 13: 12 0 for x ≤ xm 1 h(x) = 2 1− c
Page 14 and 15: flow rule: E Ý i = p Ý ˜ S ′
Page 18 and 19: parameters of Tables 2 and 3, and t
Page 20 and 21: 20 Fig. 1. Experiments and model pr
Page 22 and 23: 22 Fig. 3. Contour plots of the max
Page 24 and 25: 24 Fig. 5. Contour plots of directi
Page 26 and 27: 26 Fig. 6. FE-mesh and loading cond
Page 28 and 29: 28 Fig. 13. FE-mesh and loading con
Page 30 and 31: proove that the model performs well
Page 33 and 34: 6. References AI, S.H.; LUPINC, V.
Page 35 and 36: 7. Appendices: ABAQUS-Inputfiles 7.
Page 37 and 38: ** auflagerung ** *BOUNDARY, OP=NEW
Page 39 and 40: ** E, nu, Do, n, K1, K2, K3, m1 149
Page 41 and 42: ** ====== 2. load ein ** *STEP, INC
Page 43 and 44: 7.3 Appendix 3: Single crystal plat
Page 45 and 46: *NODE FILE, FREQUENCY=0 *EL FILE, F
Page 47 and 48: 7.4 Appendix 4: TiAl turbine blade
Page 49 and 50: *AMPLITUDE, NAME=CYCLEONE, DEFINITI

ABAQUS user subroutines for the simulation of viscoplastic - loicz

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