MCOHED

Bulk Data Entry Defines the material properties for damage-based cohesive material models.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
MCOHED MID KI KII KIII SFC VED RHO MXDMG  
  DMGINIID DMGEVOID              
  RAYL ALPHA              

Example 1 (no damage, no Rayleigh damping)

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
MCOHED 2 9000. 3000. 3000. -1.0 1.0e-3   0.99  

Example 2 (with damage, no Rayleigh damping)

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
MCOHED 2 9000. 3000. 3000. -1.0 1.0e-3   0.99  
  20 23              

Example 3 (no damage, with Rayleigh damping)

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
MCOHED 2 9000. 3000. 3000. -1.0 1.0e-3 1.0e-5 0.99  
± RAYL 0.22              

Definitions

Field Contents SI Unit Example
MID Material identification number.

No default (Integer > 0)

  
KI, KII, KIII Elasticity modulus corresponding to Mode I, II and III deformation, when the card is used in cohesive elements.

Penalty stiffness corresponding to Mode I, II and III deformation, when the card is used in cohesive contacts. 2

No default (Real)

 N m 2 MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaSaaaeaaca WGobaabaGaamyBamaaCaaaleqabaGaaGOmaaaaaaaaaa@38B4@ for cohesive elements

N m 3 MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaSaaaeaaca WGobaabaGaamyBamaaCaaaleqabaGaaGOmaaaaaaaaaa@38B4@ for cohesive contacts
SFC Stiffening factor in compression.

This is applicable only for Cohesive elements. For Cohesive contact, the compression stiffness is controlled by the contact penalty.

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

  
VED Factor for viscous energy dissipation. 3

Default = 0.0 (Real > 0.0)

  
RHO Density (mass per volume)

Default = 0.0 (Real ≥ 0.0)

  
MXDMG Maximum damage index, above which the cohesive element is excluded from analysis.

Default = 1.0 (Real ≥ 0.0)

  
DMGINIID Damage initiation entry ID. 4

Default = blank (Integer > 0)

  
DMGEVOID Damage evolution entry ID. 4

Default = blank (Integer > 0)

  
RAYL Continuation line flag for material-dependent Rayleigh damping 5  
ALPHA Material-dependent Rayleigh Damping coefficient for the mass matrix 5

Default = blank (Real ≥ 0.0)

  

Comments

  1. The material identification number should be unique for all MAT1, MAT2, MAT3, MAT8, MAT9, MGASK, MCOHE, MCOHED entries.
  2. In cohesive contacts, it is recommended to use KII = KIII.
  3. In some cases, snap-back phenomena could appear in numerical models with cohesive elements. VED can be used to stabilize the solution.
  4. Cohesive material with traction only can be defined by leaving the DMGINIID and DMGEVOID fields as blank. In this case, cohesive material behavior is linear elastic in nature. This is only supported for cohesive elements.

    DMGINIID and DMGEVOID must be specified with cohesive contact.

  5. For material-dependent Rayleigh damping, the equivalent viscous damping, C MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaC4qaaaa@36C0@ , is defined as:(1)
    C = ALPHA * M MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaC4qaiabg2 da9iaabgeacaqGmbGaaeiuaiaabIeacaqGbbGaaiOkaiaah2eaaaa@3D3F@
    Where,
    ALPHA MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaeyqaiaabY eacaqGqbGaaeisaiaabgeaaaa@39E9@
    Defined on the RAYL continuation line on the material entry
    M MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaCytaaaa@36CA@
    Mass matrix
    Supported solutions for material-dependent Rayleigh damping on MCOHED:
    • Direct Frequency Response Analysis
    • Modal Frequency Response Analysis
    • Linear Direct Transient Analysis
    • Linear Modal Transient Analysis
    • Nonlinear Transient Analysis
  6. For additional information, refer to Cohesive Zone Modeling in the User Guide.