FEA 2D - Calculation Dialog Box (AutoCAD Mechanical Toolset)

Loads and Supports

Inserts and edits the border conditions (supports and loads). Besides the symbol, the number of the loads, and fixed and movable supports are displayed.

Inserting Border Conditions

The sequence of the FEA routine for inserting border conditions depends on the type of border condition selected. In each case, you are prompted to select an insertion point, which has to lie on the contour (external or internal). The insertion process for forces and loads is finished when you press Enter. Then the FEA 2D calculations dialog box opens again.

You can choose these forces and loads:

Individual force:

Enter the value and direction of the force. The default direction is perpendicular to the contour. Determine the direction by entering an angle, or use the pointing device.

Fixed or movable support:

Enter the position and direction of the force. The direction for fixed supports does not affect the calculations for stress.

Forces (line) and fixed/movable supports (line):

Enter the starting and endpoints of the force. You must select a “side from endpoint”.

This refers to a point on the closed contour in the area between the specified two points where the forces or supports apply. If the line of forces surrounds the whole contour, specify the starting point and press ENTER.

Distributed forces (line) and fixed or movable supports (line) are always considered perpendicular to the contour.

The value of the distributed forces refers to force units per distance unit of the drawing (N/m or lbf/inch). If you want to enter a pressure value (for example in N/mm<²),you first have to calculate the force distribution based on the following formula:

Distributed force [N/mm] = p [N/mm²] * d [mm], where d is the thickness of the cross section. If you want to calculate stretching considerations, enter a negative value.

Note: The FEA routine draws only some symbols next to every entity. Before each calculation, the border conditions are written at every contour point in the mesh.

Editing Border Conditions

The options available for editing border conditions depend on the selected loads and forces (for example a distributed force cannot be edited with the Angle option).

Edit options:

Value: Changes the size of the forces or force lines.

Angle: Changes the direction of the specified force or support.

Move: Moves the border condition to another location.

Copy: Copies the border condition to another location.

Delete: Deletes a load or support.

Table

Opens a material dialog box that includes the values for E-module, elastic limits, Poisson ratio and brittleness belonging to the material.

E-Module

Displays the elasticity modulus belonging to the material.

Poisson

Displays the Poisson ratio.

Re

Displays the elastic limit.

Default

Determines the thickness of the cross section. Click the button on the left if an elastic deformation in Z direction is possible. Click the button on the right if the object is directly supported by fixed limits. (This means no deformation in Z direction is possible, that stress in Z direction occurs, and that stress can be calculated.)

Mesh

Creates a mesh for the enclosed contour. This routine uses a triangle element type with six nodes (linear-strain triangle). When there are very short lines near the border (for example force or supports close to a polyline corner), the routine refines the output around the midpoint (up to eight times).

Average mesh width

Specifies the base density of the mesh. This value is the average value of the triangle's sides measured in drawing units. The default value is dependent upon the contour area and is selected such that the first calculation lasts the shortest possible time.

>>> button (within the mesh section)

Displays the created mesh without exiting the FEA routine.

Refining

Shortens the sides of the mesh triangles. This can be done manually or automatically.

Results

Performs deformation calculations, based on the reactive forces. The results can be represented as:

Isolines and isoareas

Main stress lines

Deformed mesh

File

Creates the name and a path for an output file. If the option Make Output File Automatically is active, an output file with file name *.txt is generated after every calculation. The file contains all border conditions, deformed meshes, and stress for the respective forces and triangles.

at Point

Displays all results up to the selected point in the command line.

Node Numbering

Numbers each node in the output file.

Delete Results

Deletes all results of stress, deformations and node numbers.

Delete Solutions

Deletes all results, and the mesh and the copied contour. You can decide, in an inquiry box, whether the loads and forces are to remain in the drawing. The task is terminated and you can start a new task using the old contour.

Config

Opens a dialog box so that you can change or set the predefined layer groups, the colors and the symbol sizes for the FEA calculation routine.