MATX60

Format

Example

Definitions

Comments

1. The material identification number must be that of an existing MAT1 Bulk Data Entry. Only one MATX60 material extension can be associated with a particular MAT1.
2. MATX60 is only applied in geometric nonlinear analysis subcases which are defined by ANALYSIS = EXPDYN. It is ignored for all other subcases.
3. The first point of yield stress functions (plastic strain versus stress) should have a plastic strain value of zero. If the last point of the first (static) function equals 0 in stress, the default value of EPSMAX is set to the value of the corresponding plastic strain.
4. When the plastic strain reaches EPSMAX, the element is deleted.
5. If the first principal strain $\text{ε}$ ₁ reaches $\text{ε}$ _t1 (EPST1), the stress $\sigma$ is reduced by:
   (1)

   $$\sigma =\sigma \left(\frac{{\epsilon }_{\text{t}2}-{\epsilon }_1}{{\epsilon }_{\text{t}2}-{\epsilon }_{\text{t}1}}\right)$$

   with $\text{ε}$ _t2 = EPST2.

6. If the first principal strain $\text{ε}$ ₁ reaches $\text{ε}$ _t2 (EPST2), the stress is reduced to 0 (but the element is not deleted).
7. If the first principal strain $\text{ε}$ ₁ reaches $\text{ε}$ _f (EPSF), the element is deleted.
8. Strain rate filtering is used to smooth strain rates. The input FCUT is available only for shell and solid elements.
9. Hardening is defined by ICH.

   
   
   Figure 1. Isotropic Hardening

   
   
   Figure 2. Prager-Ziegler Kinematic Hardening

10. The kinematic hardening model is not available with global formulation (NIP = 0 on PSHELX), that is hardening is fully isotropic.
11. In case of kinematic hardening and strain rate dependency, the yield stress depends on the strain rate.
12. TPID is used to distinguish the behavior in tension and compression for certain materials (that is pressure dependent yield). This is available for solid elements only. The effective yield stress is then obtained by multiplying the nominal yield stress by the yield factor PSCA corresponding to the actual pressure.
13. If ${\dot{\epsilon }}_{\text{n}}\le \dot{\epsilon }\le {\dot{\epsilon }}_{\text{n}+1}$ ( ${\dot{\epsilon }}_{\text{n}}$ =EPSRn), yield stress is a cubic interpolation between functions f_n-1, f_n, f_n+1 and f_n+2.

    If $\dot{\epsilon }\le {\dot{\epsilon }}_1$ , yield stress is interpolated between functions f₁, f₂, and f₃.

    If ${\dot{\epsilon }}_{\text{Nfunc-}1}\le \dot{\epsilon }\le {\dot{\epsilon }}_{\text{Nfunc}}$ , where Nfunc is the function number for strain rate, yield is extrapolated between functions f_Nfunc-3, f_Nfunc-2, f_Nfunc-1 and f_Nfunc.

    If $\dot{\epsilon }>{\dot{\epsilon }}_{\text{Nfunc}}$ , yield is extrapolated between functions f_Nfunc-2, f_Nfunc-1, and f_Nfunc.

14. Strain rate values must be given strictly in ascending order. Separate functions must be defined for different strain rates.
15. This card is represented as an extension to a MAT1 material in HyperMesh.