# MATX70

Bulk Data Entry Defines additional material properties for tabulated visco-elastic foam material for explicit dynamic analysis.

## Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
SHAPE HYS
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
TIDL EPSRL FSCALL
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
TIDU EPSRU FSCALU
SHAPE HYS

## Example

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
MATX1 170 0.1   0.1 9.9E-07
MAT70 170 1.0 0.8     1   4

2

## Definitions

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

No default (Integer > 0)

EMAX Maximum young modulus.

(Real > 0)

EPSMAX Maximum plastic (failure) strain.

(Real > 0)

FSMOOTH Strain rate smoothing flag.
OFF (Default)
ON

FCUT Cutoff frequency for strain rate filtering.

Default = 1.E30 (Real ≥ 0)

Default = 1 (Integer ≥ 1)

Default = 1, if IFLAG = 0

Default = 0, if IFLAG = 1, 2, 3, 4

(Integer > 0)

0 (Default)
1
2
3
4

(Integer)

SHAPE Shape factor.

Default = 1.0 (Real)

Default = 1.0 (Real)

(Integer > 0)

Default = 0.0 (Real)

Default = 1.0 (Real)

No default (Integer > 0)

Default = 0.0 (Real)

Default = 1.0 (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. MATX70 is only applied in explicit dynamic analysis subcases which are defined by ANALYSIS = EXPDYN. It is ignored for all other subcases.
3. This material law can be used only with solid elements. The corresponding PSOLIDX property must define ISOLID = 1 (Belytschko element), ISMSTR = 1 (small strain), and IFRAME = OFF (not co-rotational).
$\sigma =\left(1-D\right)\left(\sigma +p\cdot l\right)-p\cdot l$

Where, $D$ is calculated from the quasi-static unloading curve.

are the current stresses computed respectively from the unloading and quasi-static curves.

The pressure is: (2)
$p=-\left({\sigma }_{xx}+{\sigma }_{yy}+{\sigma }_{zz}\right)/3$
• IFLAG = 2 - Both loading and unloading curves are used respectively. For unloading, the stress tensor is modified using the quasi-static unloading curve $\sigma$ = (1 - D) $\sigma$ , where, D is calculated from the quasi-static unloading curve.

are the current stresses computed respectively from the unloading and quasi-static curves.

$\sigma =\left(1-D\right)\left(\sigma +p\cdot I\right)-p\cdot I$
(4)
$D=\left(1-Hys\right)\left(1-{\left(\frac{{W}_{cur}}{{W}_{\mathrm{max}}}\right)}^{Shape}\right)$

Where, Wcur and Wmax are the current and maximum energy, respectively.

• IFLAG = 4 - The loading curves are used for both loading and unloading behavior. The unloading curve is ignored. The unloading stress tensor is modified using $\sigma =\left(1-D\right)\sigma$ (5)
$D=\left(1-Hys\right)\left(1-{\left(\frac{{W}_{cur}}{{W}_{\mathrm{max}}}\right)}^{Shape}\right)$

Where, Wcur and Wmax are the current and maximum energy, respectively.

• For IFLAG = 3, 4 the unloading curves are not used
6. For stresses above the last load function, the behavior is extrapolated by using the two last load functions. In order to avoid huge stress values, it is recommended to repeat the last load function.
7. When maximum plastic strain EPSMAX is reached, EMAX is used whatever the curve definition is.
8. If EMAX is blank, EMAX is set and equal to Young modulus on MAT1 card.
9. If EPSMAX is blank, it will be calculated automatically if EMAX is less than the maximum tangent according to the input stress-strain curves.
10. Young's modulus E on MAT1 card would be modified automatically if it is less than the initial value according to the input stress-strain curves' tangents.
11. This card is represented as a material in HyperMesh.