ANSYS File: Conventions
Description
Some differences between conventions used in ANSYS and Straus7 are described below.
Numbering of Elements
In ANSYS, all elements are numbered using a global numbering system (e.g., the number of the first plate element is likely to be the number of the last beam element plus 1).
In Straus7, beam, plate, brick and link elements are numbered individually using local numbering systems (i.e., the first plate element will always be plate 1, irrespective of the number of beams).
Where possible, the ANSYS element numbers are assigned as Straus7 ID attributes.
Beam Local Axis System
In ANSYS, the x direction is along the beam; the z direction at right angles to x in the plane of the reference node or reference vector; the y direction is at right angles to x and z.
In Straus7, the 3 direction is along the beam; the 2 direction is at right angles to 3 in the plane of the reference node; the 1 direction is at right angles to 2 and 3. The corresponding beam axis mappings are:
| Straus7 | ANSYS |
| +1 | +y |
| +2 | +z |
| +3 | +x |
See Beam Elements: Local and Principal Axes.
Plate Local Axis System
The local x-axis of the plate element in ANSYS is defined below:
| ANSYS Plate Type | Local x-axis |
|
PLANE2 |
Parallel to global Cartesian X-axis. |
|
PLANE13
|
Parallel to global Cartesian X-axis (KEYOPT(4) = 0). |
|
Parallel to the line N1-N2 (KEYOPT(4) = 1). |
|
|
SHELL28 |
Parallel to the line N1-N2. |
|
PLANE35 |
Parallel to global Cartesian X-axis. |
|
SHELL41 |
Parallel to the line N1-N2. |
|
PLANE42
|
Parallel to global Cartesian X-axis (KEYOPT(1) = 0). |
|
Parallel to the line N1-N2 (KEYOPT(1) = 1). |
|
|
SHELL43 |
Parallel to the line N1-N2. |
|
PLANE55 |
Parallel to global Cartesian X-axis. |
|
HYPER56
|
Parallel to global Cartesian X-axis (KEYOPT(4) = 0). |
|
Parallel to the line N1-N2 (KEYOPT(4) = 1). |
|
|
SHELL57 |
Parallel to the line N1-N2. |
|
SHELL63 |
Parallel to the line N1-N2. |
|
HYPER74 |
Parallel to global Cartesian X-axis. |
|
PLANE77 |
Parallel to global Cartesian X-axis. |
|
PLANE82 |
Parallel to global Cartesian X-axis. |
|
HYPER84 |
Parallel to global Cartesian X-axis. |
|
SHELL91 |
Parallel to the line N1-N2. |
|
SHELL93 |
Parallel to the line N1-N2. |
|
SHELL99 |
Parallel to the line N1-N2. |
|
VISCO106 |
Parallel to global Cartesian X-axis. |
|
VISCO108 |
Parallel to global Cartesian X-axis. |
|
SHELL131 |
Bisects the lines N2-N3 and N4-N1. |
|
SHELL132 |
Bisects the lines N2-N3 and N4-N1. |
|
SHELL143 |
Parallel to the line N1-N2. |
|
SHELL181 |
Bisects the lines N2-N3 and N4-N1. |
| SHELL281 | Bisects the lines N2-N3 and N4-N1. |
|
PLANE182 |
Parallel to global Cartesian X-axis. |
|
PLANE183 |
Parallel to global Cartesian X-axis. |
In Straus7, the local x-axis of plate elements are defined as:
| Straus7 Plate Type | Local x-axis |
|
Tri3 |
Passes through N1, and bisects the line N2-N3. |
|
Quad4 |
Bisects the lines N2-N3 and N4-N1. |
|
Tri6 |
Parallel to the line N1-N5. |
|
Quad8 |
Parallel to the line N8-N6. |
|
Quad9 |
Parallel to the line N8-N6. |
See Plate Elements: Local Axes.
Location of Beam Element Loads
ANSYS gives beam locations as actual values (if KEYOPT(10) = 0), or fractional values (if KEYOPT(10) = 1). In the case of distributed loads, ANSYS provides positions IOFFST and JOFFST relative to the first and second ends of the beam respectively.
Straus7 converts all locations to fractional values.
Point Loads on Axisymmetric Plate Elements
ANSYS interprets point force and moment values applied to the nodes of axisymmetric elements as the total load acting around the circumference.
Straus7 interprets point force and moment values applied to the nodes of axisymmetric elements as a load per unit radian acting around the circumference.
Direction of Plate Edge Normal Pressure
ANSYS defines a positive pressure as acting inwards.
Straus7 defines a positive pressure as acting outwards.
Units
ANSYS uses the /UNITS command to specify model units. The ANSYS model units are consistent in terms of mass, length and temperature.
Straus7 rescales all imported model data according to the existing Straus7 model units. Straus7 supports the following ANSYS unit labels for the /UNITS command:
- SI, kg-m-C
- CGS, g-cm-C
- MPA, T-mm-C
- BFT, sl-ft-F
- BIN, lbm-in-F
Undefined Units
If the units are not defined by the /UNITS command, or a valid units label is not selected, Straus7 gives the option to choose from a list of possible units for the import file.
See Also