MCOHE

Bulk Data Entry Defines the material properties for cohesive materials.

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
MCOHE	`MID`	`MODEL`
	`COHE`	`CRTOD`	`MAXOD`	`BETA`	`EXP`	`VED`		`SFC`

Example

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
MCOHE	2	2
	10.0	0.03		0.5		1.0e-3		-1.0

Definitions

Field	Contents	SI Unit Example
`MID`	Material identification number. No default (Integer > 0)
`MODEL`	Indicates the traction-separation relationship profile type. 5 1 Bilinear 2 Exponential 3 Linear-Exponential No default (Integer)
`COHE`	The energy per area that can be absorbed by the cohesive elements. It is the area under the traction-separation curve. No default (Real > 0.0)
`CRTOD`	Critical opening distance. No default (Real ≥ 0.0)
`MAXOD`	Maximum opening displacement (bilinear model only). No default (Real > 0.0)
`BETA`	Coefficient on the shear opening for mode mix based on displacement. Default = 1.0 (Real ≥ 0.0)
`EXP`	Exponential decay factor (linear-exponential model only). No default (Real > 0.0)
`VED`	Viscous energy dissipation factor. Default = 0.0. (Real > 0.0)
`SFC`	Stiffening factor in compression. Positive value (= Real > 0.0) Directly prescribed stiffness. Negative value (= Real < 0.0) Defines a stiffness scaling factor. The stiffness scaling factor is equal to \|Real < 0.0\|. The scaling is applied to the initial stiffness in separation condition. SOFT Takes the maximum diagonal value in the global stiffness of the numerical model multiplied by 1.0E2 as the compression stiffness. HARD Takes the maximum diagonal value in the global stiffness of the numerical model multiplied by 1.0E6 as the compression stiffness. AUTO Takes the maximum diagonal value in the global stiffness of the numerical model multiplied by 1.0E4 as the compression stiffness. Default = -1.0

Comments

The material identification number must be unique for all MAT1, MAT2, MAT3, MAT8, MAT9, MGASK, MCOHE, and MCOHED entries.
The normal direction of cohesive material is the principal direction (local 3-direction) in cohesive solids. Cohesive closure is defined as the relative change in position of the top and bottom surfaces of the cohesive element along the cohesive thickness direction.
MCOHE mainly defines nonlinear properties for cohesive materials under separation. MCOHE has anisotropy only in normal direction, which is called normal anisotropy. For linear analysis, the normal direction modulus is defined by the slope of traction-separation curve.
In some cases, snap-back phenomena could appear in numerical models with cohesive elements. VED can be used to stabilize the solution.
The three types of traction-separation curve are:

Figure 1. Bilinear

Figure 2. Exponential

Figure 3. Linear-Exponential
Normal and shear modes are mixed based on displacement. The mixing formulation is:(1)
$d_{e f f} = \sqrt{{(β d_{x})}^{2} + {(β d_{y})}^{2} + {(\max {0.0, d_{z}})}^{2}}$

Where,

$d_{x}$ , $d_{y}$ , and $d_{z}$

Relative displacements of the top and the bottom faces of a cohesive element along elemental x-, y- and z-axes.

$β$

Mixing coefficient, which can be input on the BETA field.