Global and local coordinate systems

Coordinate System in ANSYS

Overall and local coordinate system (Mainly involved in Modeling)

The overall coordinate system is used to determine the coordinate system by integrating the entire building you have modeled. For example, if you create a building with a rectangular plane, the overall coordinate system generally defaults to the X axis in the horizontal direction, the Y axis in the vertical direction, and the Z axis in the vertical plane.
The local coordinate system is set with a single component. For example, the x-axis of the local coordinate system is usually the direction of the strong axis of the Section for a work-shaped steel column. For a work-shaped column, it is generally the direction perpendicular to the web; the Y axis is the weak axis direction of the cross section. For a work-style column, it is generally parallel to the Web. The Z axis is generally along the length direction of the member, the thickness direction of a board member is generally used. The specific definitions shall be subject to the instructions. The X axis of the local coordinate system of such a column may be different from the X axis of the overall coordinate system.
Therefore, the overall coordinate system is relative to the entire building, and the local coordinate system is for a component. When the program outputs data related to the whole, it is generally determined by the overall coordinate system, for example, the displacement of the two directions of the building. When a component is output, it is generally determined by a local coordinate system, such as the bending moment of the column bottom section.
Therefore, during Program Computing, you must find out when the results are given in the overall coordinate system and what is given in the local coordinate system. Otherwise, errors may occur. Check the software manual.

ANSYS is a large-scale general finite element analysis (FEA) software developed by ANSYS, and is the fastest growing Computer Aided Engineering (CAE) software in the world, with most computer aided design (CAD, computer aided design) software interface, realize data sharing and exchange, such as Creo, NASTRAN, alogor, I-DEAS, AutoCAD, etc. It is a large-scale general finite element analysis software integrating structure, fluid, electric field, magnetic field, and sound field analysis.


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Coordinate System and operation of ANSYS

1. Overall Coordinate System: used to determine the spatial location of geometric parameters such as nodes and key points.

The overall coordinate system is an absolute reference system used to determine the location of the space ry. There are three types of overall coordinate systems in ANSYS that you can choose from: Cartesian coordinate system, cylindrical coordinate system, and spherical coordinate system. All three coordinate systems belong to the right coordinate system and share a coordinate origin.

2. Local Coordinate System: User-Defined coordinate system. Users can perform modeling and other operations.

Because many models in analysis are complex, it is not enough to use the overall coordinate system. This is because we must create our own coordinate system, that is, the local coordinate system. The origin of the local coordinate system can be a certain offset from the origin of the general coordinate system, or different from the previously defined general coordinate system.

Like the general coordinate system, the local coordinate system can also include the Cartesian coordinate system, the ball coordinate system, and the cylindrical coordinate system. The local coordinate system can be a circle or an elliptical coordinate system, or a circular local coordinate system.

Click the at specificed loc menu item. The pick up a specific point dialog box is displayed. You can pick up any point in the graphic window as the custom coordinate origin, you can also enter a custom coordinate origin in the input text box.

Assume that any point in the graphic window is taken as the coordinate origin, the following dialog box is displayed.

 

All local and general coordinates can be used as the current coordinate system, but only one currently activated coordinate system can be used.

To activate the coordinate system, follow these steps:

1. After a local coordinate system is defined each time, it is automatically activated into the current coordinate system.

2 utility menu/workplane/change active CS to/specificed coord System

3. The List displays the list of all coordinate systems.

To view information about all the population and local coordinate systems, you can use the following method:

Cslist

Or utility menu/LIST/other/local coord System

 

3. Coordinate System: defines the direction of freedom and result data of each node.

The general and local coordinate systems are used to locate the ry, while the node coordinate system is used to define the direction of node degrees of freedom. Each node has its own coordinate system. In practical application, sometimes it is necessary to place loads or constraints on the nodes in different directions of the coordinate system. In this case, the node coordinate system must be rotated to the desired direction, then, load or constraint is applied to the coordinate system of the node.

Rotate the coordinate system of a node to the direction of the activated coordinate system.

Rotate the coordinate system of a node to the direction of the activated coordinate system. That is, the X axis of the node coordinate system is converted to the X or R axis parallel to the active coordinate system, and the Y axis of the node coordinate system is rotated to the Y axis or θ axis parallel to the active coordinate system. The Z axis of the node coordinate system is converted to the Z axis or the Z axis of the active coordinate system.

The method for operating the node coordinate system is as follows:

Main Menu/Preprocessor/modeling/create/nodes/rotate node CS/to active CS

Main Menu/Preprocessor/modeling/Move & Modify/rotate node CS/to active CS.

 

 

4-Unit coordinate system: determines the direction of the material characteristics spindle and unit result data.

The Unit coordinate system is usedDetermine the direction of material attributes(For example, the layout direction of the composite ).It is also very useful for post-processing, such as extracting the membrane force of the beam and shell units.. Orientation of the Unit coordinate system can be found in the unit type. The default direction of most cell coordinate systems follows the following rules.

The X axis of a line 1 unit usually points from the I node of the Unit to the J node.

The X axis of the 2-shell unit usually points the I node to the J node. The Z axis is over the I point and perpendicular to the shell surface. The positive direction is determined by the right hand direction of the units I, j, and K. the Y axis is perpendicular to the X axis and the Z axis.

3. the coordinate system of 2D and 3D entities is always parallel to the Cartesian coordinate system of the population.

 

The operating method of the Unit coordinate system is as follows:

Main Menu/Preprocessor/meshing/mesh attributes/default attribs/

Main Menu/Preprocessor/modeling/create/elements/ELEM attributes (Unit attribute)

 

5. Display Coordinate System: used to display and list geometric parameters.

Display Coordinate System: Used to list and display Geometric Parameters.

The display coordinate system can be used to list and display Geometric Parameters. Although users can use different coordinate systems to create their own models, by default, the Graphic Display and list display operations are not affected by the current coordinate system, but always show coordinates or results under the overall Cartesian coordinate system, whether the current coordinate system is a column coordinate or a ball coordinate, however, the calculation result or the geometric position of the model is still the result in the overall Cartesian coordinate system.

In addition, you can view a model from different angles by modifying the type of the display coordinate system. For example, when the display coordinate system is a circle of the Cartesian coordinate system, it is changed to a rectangle under the display coordinate system is a column coordinate.

To display the coordinate system, perform the following operations:

Utility menu/workplane/change display CS

The show coordinate system is very useful for displaying the coordinates of a column and a ball node in the list. Normally, do not activate this coordinate system for display, because the coordinate system on the screen is a Cartesian coordinate system.

 

6. Result coordinate system: in a general post-processing operation, the node or unit result is converted to a specific coordinate system.

In the process of solving the problem, the calculated data includes displacement (UX, Uy, rotx, etc.), magnetic potential vector (ax, ay, AZ), etc, these data are stored in the database and result files in the node coordinate system or Unit coordinate system. However, when displaying and listing data results, you usually need to rotate the results data to the active result Coordinate System for display, the default is the total Cartesian coordinate system.

You can rotate the result coordinate system to a coordinate system (such as the overall coordinate system or a local coordinate system), or to the coordinate system (such as the node and Unit coordinate system) used for solving the problem ). If user lists, displays, or operates on these result data, they are first rotated to the result coordinate system.

Main Menu/General postproc/options for output/

Utility menu/LIST/results/options

Global and local coordinate systems