CHEXA

Bulk Data Entry Defines the connections of the HEXA solid element.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
CHEXA EID PID G1 G2 G3 G4 G5 G6  
  G7 G8 G9 G10 G11 G G13 G14  
  G15 G16 G17 G18 G19 G20      
  CORDM CID/

THETA

 PHI            

Example

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
CHEXA 71 4 3 4 5 6 7 8  
  9 10              

Definitions

Field Contents SI Unit Example
EID Unique element identification number.

No default (Integer > 0)

  
PID A PSOLID property entry identification number.
Integer
Specifies an identification number for this property.
<String>
Specifies a user-defined string label for this property. 7

Default = EID (Integer > 0 or <String>)

  
G# Grid point identification numbers of connection points.

Default = blank (Integer ≥ 0 or blank)

  
CORDM Flag indicating that the following field(s) reference data to determine the material coordinate system.  
CID Material coordinate system identification number.

Default = 0 (Integer ≥ -1)

  
THETA Angle of rotation of the elemental X-axis and Y-axis about the elemental Z-axis. The new coordinate system formed after this rotational transformation represents the material system (the PHI field can further transform the material system).
Note: For positive THETA, the elemental X-axis is rotated towards the elemental Y-axis. 5

Default = blank (Real)

  
PHI This angle is applied on the new coordinate system derived after transformation with THETA.
Angle of rotation of the elemental Z-axis and new X-axis about the new Y-axis. The new coordinate system formed after this rotational transformation represents the material system.
Note: For positive PHI, the new X-axis is rotated towards the elemental Z-axis. 5

Default = blank (Real)

  

Comments

  1. Grid points G1, ..., G4 must be given in consecutive order about one quadrilateral face. G5, ..., G8 must be on the opposite face with G5 opposite G1, G6 opposite G2, and so on.

    The edge points, G9 through G20, are optional, some or all of them may be blank. If any of the edge points are present, they all must be used. The second continuation must not be present for the 8-noded version of this element.

    It is recommended that the edge points be placed near the middle of the edge.


    Figure 1. CHEXA Definition
  2. If the user-defined node numbering on the bottom and top faces is reversed as compared to the sequence shown above, the nodes are renumbered to produce right-handed orientation of numbering. This is accomplished by swapping nodes G1 with G3, and G5 with G7. For 20-noded CHEXA, appropriate changes to mid-side node numbering are also performed. In such cases, the element coordinate system will be built on the renumbered node sequence.
  3. Stresses are output in the material coordinate system. The material coordinate system is defined on the referenced PSOLID entry. It may be defined as the basic coordinate system (CORDM = 0), a defined system (CORDM = Integer > 0), or the element coordinate system (CORDM = -1).
  4. The element coordinate system for the CHEXA element is defined as follows:
    Three intermediate vectors R, S, and T are chosen by the following rules:
    R
    Joins the centroids of the faces described by the grid points G4, G1, G5, G8 and the grid points G3, G2, G6, G7.
    S
    Joins the centroids of the faces described by the grid points G1, G2, G6, G5 and the grid points G4, G3, G7, G8.
    T
    Joins the centroids of the faces described by the grid points G1, G2, G3, G4 and the grid pints G5, G6, G7, G8.
    Figure 2. CHEXA Element Coordinate Systems

    The origin of the element coordinate system is at the intersection of these three vectors. If the vectors do not all intersect at one point, then the average location of the intersection points is used.

    The element z-axis corresponds to the T vector.

    The element y-axis is the cross product of the T and R vectors.

    The element x-axis is the cross product of the element y-axis and the element z-axis.

  5. Only one of CID or THETA/PHI can be defined for the CORDM continuation line. If THETA is input, PHI is optional. If PHI is input, THETA is mandatory. In Figure 3, initial x,y,z is the elemental coordinate system.


    Figure 3. CORDM Transformation for THETA and PHI Fields
  6. For more information, refer to Three-dimensional Solid Elements in the User Guide.
  7. String based labels allow for easier visual identification of properties, when being referenced by the elements cards. For more details, refer to String Label Based Input File in the Bulk Data Input File.
  8. This card is represented as a hexa8 or hex20 element in HyperMesh.