18.5.8 Three-dimensional cohesive element library

Products: ABAQUS/Standard  ABAQUS/Explicit  ABAQUS/CAE  

References

Element types

General elements

COH3D66-node three-dimensional cohesive element
COH3D88-node three-dimensional cohesive element

Active degrees of freedom

1, 2, 3 (, , )

Additional solution variables

None.

Nodal coordinates required

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” in “Defining the cohesive element's initial geometry, Section 18.5.4, for details.

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

Input File Usage:           
*COHESIVE SECTION

ABAQUS/CAE Usage: 

Property module: Create Section: select Other as the section Category and Cohesive as the section Type


Element-based loading

Distributed loads

Distributed loads are specified as described in Distributed loads, Section 19.4.3.


Load ID (*DLOAD):  BX

ABAQUS/CAE Load/Interaction:  Body force

Units:  FL–3

Description:  Body force in global -direction.


Load ID (*DLOAD):  BY

ABAQUS/CAE Load/Interaction:  Body force

Units:  FL–3

Description:  Body force in global -direction.


Load ID (*DLOAD):  BZ

ABAQUS/CAE Load/Interaction:  Body force

Units:  FL–3

Description:  Body force in global -direction.


Load ID (*DLOAD):  BXNU

ABAQUS/CAE Load/Interaction:  Body force

Units:  FL–3

Description:  Nonuniform body force in global -direction with magnitude supplied via user subroutine DLOAD in ABAQUS/Standard (DLOAD, Section 25.2.5) and VDLOAD in ABAQUS/Explicit (VDLOAD, Section 25.3.1).


Load ID (*DLOAD):  BYNU

ABAQUS/CAE Load/Interaction:  Body force

Units:  FL–3

Description:  Nonuniform body force in global -direction with magnitude supplied via user subroutine DLOAD in ABAQUS/Standard (DLOAD, Section 25.2.5) and VDLOAD in ABAQUS/Explicit (VDLOAD, Section 25.3.1).


Load ID (*DLOAD):  BZNU

ABAQUS/CAE Load/Interaction:  Body force

Units:  FL–3

Description:  Nonuniform body force in global -direction with magnitude supplied via user subroutine DLOAD in ABAQUS/Standard (DLOAD, Section 25.2.5) and VDLOAD in ABAQUS/Explicit (VDLOAD, Section 25.3.1).


Load ID (*DLOAD):  CENT(S)

ABAQUS/CAE Load/Interaction:  Not supported

Units:  FL–4(ML–3T–2)

Description:  Centrifugal load (magnitude is input as , where is the mass density per unit volume, is the angular velocity).


Load ID (*DLOAD):  CENTRIF(S)

ABAQUS/CAE Load/Interaction:  Rotational body force

Units:  T–2

Description:  Centrifugal load (magnitude is input as , where is the angular velocity).


Load ID (*DLOAD):  CORIO(S)

ABAQUS/CAE Load/Interaction:  Not supported

Units:  FL–4T (ML–3T–1)

Description:  Coriolis force (magnitude is input as , where is the mass density per unit volume, is the angular velocity).


Load ID (*DLOAD):  GRAV

ABAQUS/CAE Load/Interaction:  Gravity

Units:  LT–2

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


Load ID (*DLOAD):  Pn

ABAQUS/CAE Load/Interaction:  Not supported

Units:  FL–2

Description:  Pressure on face n.


Load ID (*DLOAD):  PnNU

ABAQUS/CAE Load/Interaction:  Not supported

Units:  FL–2

Description:  Nonuniform pressure on face n with magnitude supplied via user subroutine DLOAD in ABAQUS/Standard (DLOAD, Section 25.2.5) and VDLOAD in ABAQUS/Explicit (VDLOAD, Section 25.3.1).


Load ID (*DLOAD):  ROTA(S)

ABAQUS/CAE Load/Interaction:  Rotational body force

Units:  T–2

Description:  Rotary acceleration load (magnitude is input as , where is the rotary acceleration).


Load ID (*DLOAD):  VPn(E)

ABAQUS/CAE Load/Interaction:  Not supported

Units:  FL–3T

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

Surface-based loading

Distributed loads

Surface-based distributed loads are specified as described in Distributed loads, Section 19.4.3.


Load ID (*DSLOAD):  P

ABAQUS/CAE Load/Interaction:  Pressure

Units:  FL–2

Description:  Pressure on the element surface.


Load ID (*DSLOAD):  PNU

ABAQUS/CAE Load/Interaction:  Pressure

Units:  FL–2

Description:  Nonuniform pressure on the element surface with magnitude supplied via user subroutine DLOAD in ABAQUS/Standard (DLOAD, Section 25.2.5) and VDLOAD in ABAQUS/Explicit (VDLOAD, Section 25.3.1).


Load ID (*DSLOAD):  VP(E)

ABAQUS/CAE Load/Interaction:  Not supported

Units:  FL–3T

Description:  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, Section 18.5.5, and Defining the constitutive response of cohesive elements using a traction-separation description, Section 18.5.6.

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” in “Defining the constitutive response of cohesive elements using a continuum approach, Section 18.5.5, 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” in “Defining the constitutive response of cohesive elements using a continuum approach, Section 18.5.5, 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. 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

Element faces for COH3D6

Face 11 – 2 – 3 face
Face 24 – 6 – 5 face
Face 31 – 4 – 5 – 2 face
Face 42 – 5 – 6 – 3 face
Face 53 – 6 – 4 – 1 face

Element faces for COH3D8

Face 11 – 2 – 3 – 4 face
Face 25 – 8 – 7 – 6 face
Face 31 – 5 – 6 – 2 face
Face 42 – 6 – 7 – 3 face
Face 53 – 7 – 8 – 4 face
Face 64 – 8 – 5 – 1 face

Numbering of integration points for output