# MATVP

Bulk Data Entry Defines material properties for nonlinear creep materials.

## Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
MATVP MID CTYPE A n m B R dH
thetaZ

## Example

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
MATVP 2 STRAIN 3.28e-11 3.15 -0.2

## Definitions

Field Contents SI Unit Example
MID Unique material identification number.

No default (Integer > 0)

CTYPE Specifies the creep material model type.
STRAIN (Default)
Strain hardening form.
TIMEC
Time hardening form using creep time.
TIMET
Time hardening form using total time.
HYPERB
Hyperbolic Sine hardening form.

A Material parameter.

Default = blank (Real > 0.0)

n Material parameter.

Default = blank (Real > 0.0)

m Material parameter.

Default = blank (-1.0 ≤ Real ≤ 0.0)

B Material parameter. 9

No default (Real > 0.0)

R Universal gas constant. 9

No default (Real > 0.0)

dH Activation energy. 9

No default (Real > 0.0)

thetaZ Absolute zero temperature.

Default = 0.0 (Real)

1. CHEXA, CTETRA, CPENTA, CPYRA elements are supported.
2. Specifying a MAT1 and a MATVP with the same MID allows modeling creep material. Specifying a MAT1, a MATS1 and a MATVP with the same MID can model a creep material with plasticity.
3. You can choose explicit or implicit time integration for creep materials by using the TINT field of the VISCO card.
4. The STRAIN hardening formulation is:(1)
${\stackrel{˙}{\overline{\epsilon }}}^{c}={A}^{\frac{1}{m+1}}{\overline{\sigma }}^{\frac{n}{m+1}}{\left(\left(m+1\right){\overline{\epsilon }}^{c}\right)}^{\frac{m}{m+1}}$
The TIME hardening formulation is:(2)
${\stackrel{˙}{\overline{\epsilon }}}^{c}=A{\overline{\sigma }}^{n}{t}^{m}$
Where,
${\stackrel{˙}{\overline{\epsilon }}}^{c}=\sqrt{\frac{2}{3}{\stackrel{˙}{\epsilon }}^{c}:{\stackrel{˙}{\epsilon }}^{c}}$
Equivalent creep strain rate
$\overline{\sigma }$
Equivalent deviatoric stress
$t$
Total time
The HYPERB hardening form is:(3)
${\stackrel{˙}{\overline{\epsilon }}}^{c}={\text{Asinh}}^{n}\left(B\overline{\sigma }\right)\text{exp}\left(-\frac{dH}{R\left(\theta -{\theta }^{z}\right)}\right)$
Where,
$\theta$ and ${\theta }^{z}$
The current and absolute zero temperatures, respectively.

If $dH$ is set to zero, the temperature dependence is absent.

5. The units for $A$ is ${F}^{-n}{L}^{2n}{T}^{-\left(m+1\right)}$ .
Where,
$F$
Force
$L$
Length
$T$
Time

You might consider switching to another set of units if the value of $A$ is too small.

6. A VISCO Subcase Entry is mandatory to conduct creep material analysis in a particular subcase.
7. If CNTNLSUB is used with the time hardening form:
• TIMEC indicates the accumulative time, only from the subcases with the VISCO entry.
• TIMET indicates the accumulative time from all the connected subcases.

For example, if there are 4 subcases – Subcase 1, Subcase 2, Subcase 3 and Subcase 5, where only Subcases 1, 3, and 5 are connected by CNTNLSUB.

If Subcases 1 and 5 have VISCO entry while Subcase 3 does not have the VISCO entry, then:
• TIMEC will indicate the accumulative time from Subcases 1 and 5 only.
• TIMET will indicate the accumulative time from Subcases 1, 3 and 5.

If CNTNLSUB is not used, then both TIMEC and TIMET have the same effect of denoting the time for a specific subcase (only for subcases with the VISCO entry).

8. MATVP is supported for small displacement and large displacement nonlinear analysis.
9. The values of B, R and dH are required only when the Hyperbolic Sine hardening form (CTYPE = HYPERB) is used.