# *MAT_138 (COHESIVE_MIXED_MODE)

LS-DYNA Input Interface KeywordThis model expresses a constitutive relation of ductile adhesive materials in 2 modes for normal and tangential directions.

## Format

(1) (2) (3) (4) (5) (6) (7) (8)
*MAT_138 or *MAT_COHESIVE_MIXED_MODE
mat_ID ${\rho }_{i}$ ROFLG Idel EN ET GIC GIIC
XMU TN TT UDN UTD Gamma

## Definition

Field Contents SI Unit Example
mat_ID Material identifier.

(Integer)

${\rho }_{i}$ Initial density.

(Real)

$\left[\frac{\text{kg}}{{\text{m}}^{\text{3}}}\right]$
ROFLG Mass calculation flag.
= 0 (Default)
Element mass is calculated using density and volume.
= 1
Element mass is calculated using density and mean area.

(Integer)

Idel Failure flag indicating the number of integration points to delete the element (between 1 and 4).

Default = 1 (Integer)

EN Stiffness normal to the plane of the cohesive element.

(Real)

$\left[\text{Pa}\right]$
ET Stiffness into the plane of the cohesive element.

(Real)

$\left[\text{Pa}\right]$
GIC Energy release rate for mode I.

(Real)

$\left[Pa.m\right]$
GIIC Energy release rate for mode II.

(Real)

$\left[Pa.m\right]$
XMU Exponent of the mixed mode criteria.

(Real)

TN Peak traction in normal direction.
< 0
Function ID (abs(T)) of peak traction value as a function of the square root of the area of ​​the median plane of the connecting element.
= 0
Peak traction computed from UDN and GIC.
> 0
Peak traction value.

(Real)

$\left[\text{Pa}\right]$
TT Peak traction in tangential direction.
< 0
Function ID (abs(S)) of peak traction value as a function of the square root of the area of ​​the median plane of the connecting element.
= 0
Peak traction computed from UTN and GIIC.
> 0
Peak traction value.

(Real)

$\left[\text{Pa}\right]$
UDN Ultimate displacement in the normal direction.

Used only if TN=0, then $TN=\frac{2*GIC}{UDN}$

(Real)

$\left[\text{m}\right]$
UTD Ultimate displacement in the tangential direction.

Used only if TT=0, then $TT=\frac{2*GIIC}{UTN}$

(Real)

$\left[\text{m}\right]$
Gamma Benzeggagh-Kenane exponent for the mixed mode.

(Real)