# MATVP

Bulk Data Entry Defines material properties for nonlinear creep materials.

## Format A: For Power law-based definition

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MATVP MID CTYPE A n m B R dH
thetaZ

## Format B: For material parameter calibration from test data

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
MATVP MID TEST TID SIG ALB AUB nLB nUB
mLB mUB

## Example A

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MATVP 101 STRAIN 3.28e-11 3.15 -0.2

## Example B

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MATVP 102 TEST 1001 39.3

## Definitions

Field Contents SI Unit Example
MID Unique material identification number.

No default (Integer > 0)

CTYPE Specifies the creep material model type.
STRAIN (Default)
Based on strain hardening form.
TIMEC
Based on time hardening form using creep time.
TIMET
Based on time hardening form using total time.
HYPERB
Based on hyperbolic Sine hardening form.
TEST
Based on experimental test data. 9.

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. 8

No default (Real > 0.0)

R Universal gas constant. 8

No default (Real > 0.0)

dH Activation energy. 8

No default (Real > 0.0)

thetaZ Absolute zero temperature.

Default = 0.0 (Real)

TID Table identification number of a TABLES1 entry containing experimental test data. 9
In the TABLES1 definition,
• y-values should be the creep strains
• x-values should be the time points.

(Integer > 0)

SIG von Mises stress of the experimental test data.

No default (Real ≥ 0.0)

ALB Lower bound for the material parameter A.

Default = 1.0 E-09 (Real > 0.0)

AUB Upper bound for the material parameter A.

Default = 1.0 E04 (Real > 0.0)

nLB Lower bound for the material parameter n.

Default = 0.0 (Real ≧ 0.0)

nUB Upper bound for the material parameter n.

Default = 6.0 (Real > 0.0)

mLB Lower bound for the material parameter m.

Default = -1.0 (-1 ≦ Real < 0.0)

mUB Upper bound for the material parameter m.

Default = 0.0 (-1 < Real ≦ 0.0)

1. Support information for MATVP is:
• Analysis types: Nonlinear static/transient for both small/large displacement types.
• Elements: CHEXA, CTETRA, CPENTA, CPYRA.
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

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 – 1, 2, 3 and 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. The values of B, R and dH are required only when the Hyperbolic Sine hardening form (CTYPE = HYPERB) is used.
9. Format B can be used for a basic material parameter calibration functionality based on experimental creep test data. The calibration is based on a time hardening formulation. The upper and lower bounds can be used for searching the suitable parameter values during the calibration process.