# MATX62

Bulk Data Entry Defines additional material properties for Hyper-visco-elastic material for geometric nonlinear analysis. This material is used to model rubber, polymers, and elastomers. This material is compatible with solid and shell elements.

## Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
MATX62 MID MUMAX
LAW MU1 ALFA1 MU2 ALFA2 MU3 ALFA3
MU4 ALFA4 MU5 ALFA5 etc
Optional continuation lines for Maxwell value:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
MAXWELL GAM1 T1 GAM2 T2 GAM3 T3
GAM4 T4 GAM5 T5 etc

## Example

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
MAT1 102 10.0   0.495 6.0E-10
MATX62 102
LAW 0.10 2.0 -0.010 -2.0

## Definitions

Field Contents SI Unit Example
MID Material ID of the associated MAT1. 1

No default (Integer > 0)

MUMAX Maximum viscosity.

Default = 1030 (Real)

LAW Indicates that material parameters MUi and ALFAi follow.
MUi Parameter $\mu$ i.

(Real)

ALFAi Parameter αi.

(Real)

MAXWELL Indicates that MAXWELL model parameter pairs GAMi and Ti follow.
GAMi Stiffness ratio ${\gamma }_{i}$ .

(Real)

Ti Time relaxation ${\tau }_{i}$ .

(Real)

1. The material identification number must be that of an existing MAT1 Bulk Data Entry. Only one MATXi material extension can be associated with a particular MAT1.
2. MATX62 is only applied in geometric nonlinear analysis subcases which are defined by ANALYSIS = EXPDYN. It is ignored for all other subcases.
3. NU is defined on the corresponding MAT1.
4. If no pair GAM1, T1 is given the law is hyper-elastic.
5. The strain energy density W is computed using the following equation:
(1)
$\text{W}\left({\lambda }_{1},{\lambda }_{2}{\lambda }_{3}\right)=\sum _{\text{i}=1}^{\text{N}}\frac{2\mu }{{\alpha }_{\text{i}}^{2}}\left({\lambda }_{1}^{{\alpha }_{\text{i}}}+{\lambda }_{2}^{{\alpha }_{\text{i}}}+{\lambda }_{3}^{{\alpha }_{\text{i}}}-3+\frac{1}{\beta }\left({\text{J}}^{-\alpha \text{i}\beta }-1\right)\right)$

with ${\lambda }_{i}$ being the ith principal stretch, J = $\lambda$ 1 * $\lambda$ 2 * $\lambda$ 3 being the relative volume and $\beta =\frac{\text{v}}{\left(1-2\text{v}\right)}$ . O < NU < 0.5

The ground shear modulus is:(2)
$\text{G}=\sum _{1}^{\text{N}}{\mu }_{\text{i}}$
6. This card is represented as a material in HyperMesh.