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
0
Bilinear
1
Exponential
2
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

  1. The material identification number must be unique for all MAT1, MAT2, MAT3, MAT8, MAT9, MGASK, MCOHE, and MCOHED entries.
  2. 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.
  3. 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.
  4. In some cases, snap-back phenomena could appear in numerical models with cohesive elements. VED can be used to stabilize the solution.
  5. The three types of traction-separation curve are:


    Figure 1. Bilinear


    Figure 2. Exponential


    Figure 3. Linear-Exponential
  6. Normal and shear modes are mixed based on displacement. The mixing formulation is:(1)
    d e f f = ( β d x ) 2 + ( β d y ) 2 + ( max { 0.0 , d z } ) 2 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamizamaaBa aaleaacaWGLbGaamOzaiaadAgaaeqaaOGaeyypa0ZaaOaaaeaadaqa daqaaiabek7aIjaadsgadaWgaaWcbaGaamiEaaqabaaakiaawIcaca GLPaaadaahaaWcbeqaaiaaikdaaaGccqGHRaWkdaqadaqaaiabek7a IjaadsgadaWgaaWcbaGaamyEaaqabaaakiaawIcacaGLPaaadaahaa WcbeqaaiaaikdaaaGccqGHRaWkdaqadaqaaiGac2gacaGGHbGaaiiE amaacmaabaGaaGimaiaac6cacaaIWaGaaiilaiaadsgadaWgaaWcba GaamOEaaqabaaakiaawUhacaGL9baaaiaawIcacaGLPaaadaahaaWc beqaaiaaikdaaaaabeaaaaa@558E@
    Where,
    d x MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamizamaaBa aaleaacaWG4baabeaaaaa@3809@ , d y MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamizamaaBa aaleaacaWG4baabeaaaaa@3809@ , and d z MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamizamaaBa aaleaacaWG4baabeaaaaa@3809@
    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.