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)

Comments

CHEXA, CTETRA, CPENTA, CPYRA elements are supported.
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.
You can choose explicit or implicit time integration for creep materials by using the TINT field of the VISCO card.
The STRAIN hardening formulation is:(1)
${\dot{\bar{ε}}}^{c} = A^{\frac{1}{m + 1}} {\bar{σ}}^{\frac{n}{m + 1}} {((m + 1) {\bar{ε}}^{c})}^{\frac{m}{m + 1}}$

The TIME hardening formulation is:(2)
${\dot{\bar{ε}}}^{c} = A {\bar{σ}}^{n} t^{m}$

Where,

${\dot{\bar{ε}}}^{c} = \sqrt{\frac{2}{3} {\dot{ε}}^{c} : {\dot{ε}}^{c}}$

Equivalent creep strain rate

$\bar{σ}$

Equivalent deviatoric stress

$t$

Total time

The HYPERB hardening form is:(3)
${\dot{\bar{ε}}}^{c} = {Asinh}^{n} (B \bar{σ}) exp (- \frac{d H}{R (θ - θ^{z})})$
Where,

$θ$ and $θ^{z}$

The current and absolute zero temperatures, respectively.

If $d H$ is set to zero, the temperature dependence is absent.
The units for $A$ is $F^{- n} L^{2 n} T^{- (m + 1)}$ .
Where,

$F$

Force

$L$

Length

$T$

Time

You might consider switching to another set of units if the value of $A$ is too small.
A VISCO Subcase Entry is mandatory to conduct creep material analysis in a particular subcase.
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).
MATVP is supported for small displacement and large displacement nonlinear analysis.
The values of B, R and dH are required only when the Hyperbolic Sine hardening form (CTYPE = HYPERB) is used.