Three-Dimensional Cohesive Element Library

This section provides a reference to the three-dimensional cohesive elements available in Abaqus/Standard and Abaqus/Explicit.

This page discusses:

 

See Also
About Cohesive Elements
Choosing a Cohesive Element
*COHESIVE SECTION

Element Types

General Elements

COH3D6

6-node cohesive element

COH3D8

8-node cohesive element

Active Degrees of Freedom

1, 2, 3

Additional Solution Variables

None.

Pore Pressure Elements

COD3D6P(S)

9-node displacement and pore pressure cohesive element with the transition from Darcy flow to Poiseuille flow

COD3D8P(S)

12-node displacement and pore pressure cohesive element with the transition from Darcy flow to Poiseuille flow

COH3D6P(S)

9-node displacement and pore pressure cohesive element

COH3D8P(S)

12-node displacement and pore pressure cohesive element

Active Degrees of Freedom

1, 2, 3, 8 at nodes on the top and bottom faces

8 at nodes on the middle face

Additional Solution Variables

None.

Coupled Temperature-Displacement Elements

COH3D6T(S)

6-node displacement and temperature cohesive element

COH3D8T(S)

8-node displacement and temperature cohesive element

Active Degrees of Freedom

1, 2, 3, 11 at nodes on the top and bottom faces

Additional Solution Variables

None.

Coupled Temperature-Pore Pressure Elements

COD3D6PT(S)

9-node temperature and pore pressure cohesive element

COD3D8PT(S)

12-node temperature and pore pressure cohesive element

Active Degrees of Freedom

1, 2, 3, 8, 11 at nodes on the top, bottom, and middle faces (1, 2, and 3 on the middle face are constrained by corresponding values on the top and bottom faces)

Additional Solution Variables

None.

Nodal Coordinates Required

X,Y,Z

Element Property Definition

You can define the element's initial constitutive thickness. The default initial constitutive thickness of cohesive elements depends on the response of these elements. For continuum response, the default initial constitutive thickness is computed based on the nodal coordinates. For traction-separation response, the default initial constitutive thickness is assumed to be 1.0. For response based on a uniaxial stress state, there is no default; you must indicate your choice of the method for computing the initial constitutive thickness. See Specifying the Constitutive Thickness for details.

Abaqus computes the thickness direction automatically based on the midsurface of the element.

Element-Based Loading

Distributed Loads

Distributed loads are specified as described in Distributed Loads.

*dload
  1. Load ID (*DLOAD): BX
  2. FL−3

  3. Body force in global X-direction.

  1. Load ID (*DLOAD): BY
  2. FL−3

  3. Body force in global Y-direction.

  1. Load ID (*DLOAD): BZ
  2. FL−3

  3. Body force in global Z-direction.

  1. Load ID (*DLOAD): BXNU
  2. FL−3

  3. Nonuniform body force in global X-direction with magnitude supplied via user subroutine DLOAD in Abaqus/Standard and VDLOAD in Abaqus/Explicit.

  1. Load ID (*DLOAD): BYNU
  2. FL−3

  3. Nonuniform body force in global Y-direction with magnitude supplied via user subroutine DLOAD in Abaqus/Standard  and VDLOAD in Abaqus/Explicit.

  1. Load ID (*DLOAD): BZNU
  2. FL−3

  3. Nonuniform body force in global Z-direction with magnitude supplied via user subroutine DLOAD in Abaqus/Standard  and VDLOAD in Abaqus/Explicit.

  1. Load ID (*DLOAD): CENT(S)
  2. FL−4(ML−3T−2)

  3. Centrifugal load (magnitude is input as ρ⁢ω2, where ρ is the mass density per unit volume, ω is the angular velocity).

  1. Load ID (*DLOAD): CENTRIF(S)
  2. T−2

  3. Centrifugal load (magnitude is input as ω2, where ω is the angular velocity).

  1. Load ID (*DLOAD): CORIO(S)
  2. FL−4T (ML−3T−1)

  3. Coriolis force (magnitude is input as ρ⁢ω, where ρ is the mass density per unit volume, ω is the angular velocity).

  1. Load ID (*DLOAD): GRAV
  2. LT−2

  3. Gravity loading in a specified direction (magnitude is input as acceleration).

  1. Load ID (*DLOAD): Pn
  2. FL−2

  3. Pressure on face n.

  1. Load ID (*DLOAD): PnNU
  2. FL−2

  3. Nonuniform pressure on face n with magnitude supplied via user subroutine DLOAD in Abaqus/Standard  and VDLOAD in Abaqus/Explicit.

  1. Load ID (*DLOAD): ROTA(S)
  2. T−2

  3. Rotary acceleration load (magnitude is input as α, where α is the rotary acceleration).

  1. Load ID (*DLOAD): SBF(E)
  2. FL−5T2

  3. Stagnation body force in global X-, Y-, and Z-directions.

  1. Load ID (*DLOAD): SPn(E)
  2. FL−4T2

  3. Stagnation pressure on face n.

  1. Load ID (*DLOAD): VBF(E)
  2. FL−4T

  3. Viscous body force in global X-, Y-, and Z-directions.

  1. Load ID (*DLOAD): VPn(E)
  2. FL−3T

  3. Viscous pressure on face n, applying a pressure proportional to the velocity normal to the face and opposing the motion.

Distributed Heat Fluxes

Distributed heat fluxes are available for all elements with temperature degrees of freedom. They are specified as described in Thermal Loads.

*dflux
  1. Load ID (*DFLUX): BF
  2. JL−3T−1

  3. Heat body flux per unit volume.

  1. Load ID (*DFLUX): BFNU
  2. JL−3T−1

  3. Nonuniform heat body flux per unit volume with magnitude supplied via user subroutine DFLUX in Abaqus/Standard.

  1. Load ID (*DFLUX): MBFNU (S)
  2. JT−1

  3. Nonuniform moving or stationary concentrated heat fluxes with magnitudes supplied via user subroutine UMDFLUX.

  1. Load ID (*DFLUX): Sn
  2. JL−2T−1

  3. Heat surface flux per unit area into face n.

  1. Load ID (*DFLUX): SnNU
  2. JL−2T−1

  3. Nonuniform heat surface flux per unit area into face n with magnitude supplied via user subroutine DFLUX in Abaqus/Standard.

Film Conditions

Film conditions are available for all elements with temperature degrees of freedom. They are specified as described in Thermal Loads.

*film
  1. Load ID (*FILM): Fn
  2. JL−2T−1θ−1

  3. Film coefficient and sink temperature (units of θ) provided on face n.

  1. Load ID (*FILM): FnNU(S)
  2. JL−2T−1θ−1

  3. Nonuniform film coefficient and sink temperature (units of θ) provided on face n with magnitude supplied via user subroutine FILM.

  1. Load ID (*FILM): FFS (S)
  2. JL−2T−1θ−1

  3. Film coefficient and sink temperature (units of θ) provided on all free faces of an element.

  1. Load ID (*FILM): FFSNU (S)
  2. JL−2T−1θ−1

  3. Nonuniform film coefficient and sink temperature (units of θ ) provided on all free faces of an element with magnitude supplied via user subroutine FILM.

Radiation Types

Radiation conditions are available for all elements with temperature degrees of freedom. They are specified as described in Thermal Loads.

*radiate
  1. Load ID (*RADIATE): Rn
  2. Dimensionless

  3. Emissivity and sink temperature (units of θ) provided on face n.

  1. Load ID (*RADIATE): RFS
  2. Dimensionless

  3. Emissivity and sink temperature (units of θ) provided on free faces of an element.

Surface-Based Loading

Distributed Loads

Surface-based distributed loads are specified as described in Distributed Loads.

*dsload
  1. Load ID (*DSLOAD): P
  2. FL−2

  3. Pressure on the element surface.

  1. Load ID (*DSLOAD): PNU
  2. FL−2

  3. Nonuniform pressure on the element surface with magnitude supplied via user subroutine DLOAD in Abaqus/Standard  and VDLOAD in Abaqus/Explicit.

  1. Load ID (*DSLOAD): SP(E)
  2. FL−4T2

  3. Stagnation pressure on the element surface.

  1. Load ID (*DSLOAD): VP(E)
  2. FL−3T

  3. Viscous pressure applied on the element surface. The viscous pressure is proportional to the velocity normal to the element face and opposing the motion.

Element Output

Stress, strain, and other tensor components available for output depend on whether the cohesive elements are used to model adhesive joints, gaskets, or delamination problems. You indicate the intended usage of the cohesive elements by choosing an appropriate response type when defining the section properties of these elements. The available response types are discussed in Defining the Constitutive Response of Cohesive Elements Using a Continuum Approach and Defining the Constitutive Response of Cohesive Elements Using a Traction-Separation Description.

Cohesive Elements Using a Continuum Response

Stress and other tensors (including strain tensors) are available for elements with continuum response. Both the stress tensor and the strain tensor contain true values. For the constitutive calculations using a continuum response, only the direct through-thickness and the transverse shear strains are assumed to be nonzero. All the other strain components (i.e., the membrane strains) are assumed to be zero (see Modeling of an Adhesive Layer of Finite Thickness for details). All tensors have the same number of components. For example, the stress components are as follows:

S11

Direct membrane stress.

S22

Direct membrane stress.

S33

Direct through-thickness stress.

S12

In-plane membrane shear stress.

S13

Transverse shear stress.

S23

Transverse shear stress.

Cohesive Elements Using a Uniaxial Stress State

Stress and other tensors (including strain tensors) are available for cohesive elements with uniaxial stress response. Both the stress tensor and the strain tensor contain true values. For the constitutive calculations using a uniaxial stress response, only the direct through-thickness stress is assumed to be nonzero. All the other stress components (i.e., the membrane and transverse shear stresses) are assumed to be zero (see Modeling of Gaskets and/or Small Adhesive Patches for details). All tensors have the same number of components. For example, the stress components are as follows:

S33

Direct through-thickness stress.

Cohesive Elements Using a Traction-Separation Response

Stress and other tensors (including strain tensors) are available for elements with traction-separation response. Both the stress tensor and the strain tensor contain nominal values. The output variables E, LE, and NE all contain the nominal strain when the response of cohesive elements is defined in terms of traction versus separation. The output variable ER contains the nominal strain rate. All tensors have the same number of components. For example, the stress components are as follows:

S33

Direct through-thickness stress.

S13

Transverse shear stress.

S23

Transverse shear stress.

Node Ordering and Face Numbering on Elements



Table 1. Element faces for COH3D6 and COD3D6P
Face 1 1 – 2 – 3 face
Face 2 4 – 6 – 5 face
Face 3 1 – 4 – 5 – 2 face
Face 4 2 – 5 – 6 – 3 face
Face 5 3 – 6 – 4 – 1 face
Table 2. Element faces for COH3D8 and COD3D8P
Face 1 1 – 2 – 3 – 4 face
Face 2 5 – 8 – 7 – 6 face
Face 3 1 – 5 – 6 – 2 face
Face 4 2 – 6 – 7 – 3 face
Face 5 3 – 7 – 8 – 4 face
Face 6 4 – 8 – 5 – 1 face

Numbering of Integration Points for Output