Axisymmetric Surface Element Library

This section provides a reference to the axisymmetric surface elements available in Abaqus/Standard.

This page discusses:

See Also
Surface Elements
In Other Guides
*SURFACE SECTION
*REBAR LAYER

Products Abaqus/Standard Abaqus/CAE

Conventions

Coordinate 1 is r, coordinate 2 is z. At θ=0, the r-direction corresponds to the global X-direction and the z-direction corresponds to the global Y-direction. This is important when data must be given in global directions. Coordinate 1 should be greater than or equal to zero.

Degree of freedom 1 is ur, degree of freedom 2 is uz. Generalized axisymmetric elements with twist have an additional degree of freedom, 5, corresponding to the twist angle ϕ (in radians).

Abaqus/Standard does not automatically apply any boundary conditions to nodes located along the symmetry axis. You must apply radial or symmetry boundary conditions on these nodes if desired.

Point loads and moments should be given as the value integrated around the circumference; that is, the total value on the ring.

Element Types

Regular Axisymmetric Surface Elements

SFMAX1

2-node linear, without twist

SFMAX2

3-node quadratic, without twist

Active Degrees of Freedom

1, 2

Additional Solution Variables

None.

Generalized Axisymmetric Surface Elements

SFMGAX1

2-node linear, with twist

SFMGAX2

3-node quadratic, with twist

Active Degrees of Freedom

1, 2, 5

Additional Solution Variables

None.

Nodal Coordinates Required

R, Z

Element Property Definition

Input File Usage

Use the following option to define surface elements:

            
              SURFACE SECTION

If rebar are being defined, use the following option in conjunction with the SURFACE SECTION option:

            
              REBAR LAYER

Use the following option to define a mass density per unit area:

SURFACE SECTION, DENSITY=number

Abaqus/CAE Usage

Property module: Create Section: select Shell as the section Category and Surface as the section Type, Rebar Layers (optional)

You cannot define the mass per unit area for a surface section in Abaqus/CAE.

Element-Based Loading

Distributed Loads

Distributed loads are specified as described in Distributed Loads. Gravity and centrifugal loads apply only if the surface elements have rebar defined or if the elements have a defined density.

*dload
  1. Load ID (*DLOAD): BR
  2. Body force
  3. FL−2

  4. Body force in the radial (1 or r) direction.

  1. Load ID (*DLOAD): BZ
  2. Body force
  3. FL−2

  4. Body force in the axial (2 or z) direction.

  1. Load ID (*DLOAD): BRNU
  2. Body force
  3. FL−2

  4. Nonuniform body force in the radial direction with magnitude supplied via user subroutine DLOAD.

  1. Load ID (*DLOAD): BZNU
  2. Body force
  3. FL−2

  4. Nonuniform body force in the axial direction with magnitude supplied via user subroutine DLOAD.

  1. Load ID (*DLOAD): CENT
  2. Not supported
  3. FL−3 (ML−2T−2)

  4. Centrifugal load (magnitude is input as ρ⁢ω2, where ρ is the mass density per unit area, ω is the angular velocity). Since only axisymmetric deformation is allowed, the spin axis must be the z-axis.

  1. Load ID (*DLOAD): CENTRIF
  2. Rotational body force
  3. T−2

  4. Centrifugal load (magnitude is input as ω2, where ω is the angular velocity). Since only axisymmetric deformation is allowed, the spin axis must be the z-axis.

  1. Load ID (*DLOAD): GRAV
  2. Gravity
  3. LT−2

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

  1. Load ID (*DLOAD): HP
  2. Not supported
  3. FL−2

  4. Hydrostatic pressure applied to the element reference surface and linear in global Z. The pressure is positive in the direction of the positive element normal.

  1. Load ID (*DLOAD): P
  2. Pressure
  3. FL−2

  4. Pressure applied to the element reference surface. The pressure is positive in the direction of the positive element normal.

  1. Load ID (*DLOAD): PNU
  2. Not supported
  3. FL−2

  4. Nonuniform pressure applied to the element reference surface with magnitude supplied via user subroutine DLOAD. The pressure is positive in the direction of the positive element normal.

  1. Load ID (*DLOAD): TRSHR
  2. Surface traction
  3. FL−2

  4. Shear traction on the element reference surface.

  1. Load ID (*DLOAD): TRSHRNU (S)
  2. Not supported
  3. FL−2

  4. Nonuniform shear traction on the element reference surface with magnitude and direction supplied via user subroutine UTRACLOAD.

  1. Load ID (*DLOAD): TRVEC
  2. Surface traction
  3. FL−2

  4. General traction on the element reference surface.

  1. Load ID (*DLOAD): TRVECNU (S)
  2. Not supported
  3. FL−2

  4. Nonuniform general traction on the element reference surface with magnitude and direction supplied via user subroutine UTRACLOAD.

Foundations

Foundations are specified as described in Element Foundations.

*foundation
  1. Load ID (*FOUNDATION): F
  2. Elastic foundation
  3. FL−3

  4. Elastic foundation. For SFMGAX1 and SFMGAX2 elements the elastic foundations are applied to degrees of freedom ur and uz only.

Surface-Based Loading

Distributed Loads

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

*dsload
  1. Load ID (*DSLOAD): HP
  2. Pressure
  3. FL−2

  4. Hydrostatic pressure applied to the element reference surface and linear in global Z. The pressure is positive in the direction opposite to the surface normal.

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

  4. Pressure applied to the element reference surface. The pressure is positive in the direction opposite to the surface normal.

  1. Load ID (*DSLOAD): PNU
  2. Pressure
  3. FL−2

  4. Nonuniform pressure applied to the element reference surface with magnitude supplied via user subroutine DLOAD. The pressure is positive in the direction opposite to the surface normal.

  1. Load ID (*DSLOAD): TRSHR
  2. Surface traction
  3. FL−2

  4. Shear traction on the element reference surface.

  1. Load ID (*DSLOAD): TRSHRNU (S)
  2. Surface traction
  3. FL−2

  4. Nonuniform shear traction on the element reference surface with magnitude and direction supplied via user subroutine UTRACLOAD.

  1. Load ID (*DSLOAD): TRVEC
  2. Surface traction
  3. FL−2

  4. General traction on the element reference surface.

  1. Load ID (*DSLOAD): TRVECNU (S)
  2. Surface traction
  3. FL−2

  4. Nonuniform general traction on the element reference surface with magnitude and direction supplied via user subroutine UTRACLOAD.

Incident Wave Loading

Surface-based incident wave loading is also available for these elements. See Acoustic and Shock Loads.

Element Output

Output is currently available only when the surface element is used to carry rebar layers. See Defining Reinforcement for details.

Node Ordering on Elements



 

Numbering of Integration Points for Output