FesaWin

COBUS FINITE ELEMENT SOFTWARE


 
 




USER MANUAL FESAWIN 1.2

 

[ Home | Manual | Screens | Download]

Tabel of Contents

1.0 Introduction

1.1 General
1.2 Description of Finite Element Analysis
1.3 Description of FesaWin
1.4 Technical Information
1.4.1 Elements
1.4.2 Stress Convention
1.4.3 Files
2.0 Controls
2.1 Mouse actions
2.2 Main Menu
2.2.1 File
2.2.2 Edit
2.2.3 Select
2.2.4 Add
2.2.5 Define
2.2.6 Setting
2.2.7 View
2.2.8 Analyse
2.2.9 Post-Process
2.2.10 Info
2.3 Command line
3.0 Creating and Analysing a model
3.1 Analysis setup
3.1.1 Units
3.1.2 Type of analyses
3.1.3 Declare workspace
3.2 Placing elements
3.2.1 Defining element groups
3.2.2 Single element placement
3.2.3 Patching and Meshing
3.3 Defining boundary condition
3.4 Analysing model
3.5 Post-processing
4.0 Element description
4.1 BARD Two Nodal Axial rod element
4.2 BEAM Two Nodal Beam Bending Element
4.3 TRIM Three Nodal Membrane Element
4.4 To be continued…


1.0 Introduction
 
1.1 General

This manual describes how to use FesaWin for Finite Element Analysis (FEA).
The Manual is divided in four chapters.

 Chapter 1, INTRODUCTION
This chapter will give the user a general description of FEA and FesaWin, and some technical information on the available elements and numerical method used.

Chapter 2, CONTROLS
To be able to work with the program, the user needs to know how to communicate with the program. Read this chapter or use it as quick reference.

Chapter 3, CREATING AND ANALYSING A MODEL
This chapter will tell you how to built a model and how to analyse and post-process it.

Chapter 4, Element description
Finally all the elements are discussed.
 
 

The different controls of the program are referred to as follows:

1.2 Description of Finite Element Analysis

The Finite Element method is an approximate numerical method in which an arbitrary shaped structure is divided up into small elements of various shapes, sizes and types which are assembled together to form an approximate mathematical model. In this method, a large number of equilibrium equations are formulated which are solved to obtain stress and displacement distributions.

In order to do this, the engineer has to prepare the mathematical model and data which consists of model co-ordinates, material properties, loading and constraint conditions and types of elements adopted.

1.3 Description of FesaWin

FesaWin is a Linear Static Finite Element stress analysis program, which includes modelling, analysing and post-processing.

In FesaWin a model is defined with the following components:

1) Elements
2) Nodes
3) Element property groups
4) Boundary condition
 

Results of an analysis are presented in terms of:

1) Stresses
2) Displacements
 

Note: The program cannot handle more then one loadcase for the time being.

The Graphical pre-processor enables the user to define a model by simple mouse clicks and/or by direct entering co-ordinates.

Modelling can start by dividing the structure into several four or three sided patches using graphical lines or circles. When this is ready the patches can be meshed with elements. These elements are assigned to a group. Each group of elements has one set of material and element properties. When this is done, the constraint condition should be applied by fixing some of the nodes of the model. Finally the loads are applied on the nodes and the model can be analysed.

Note: it is very important for the numerical solver of the equations that rigid body movements of the model are constraint. If not properly constraint the solver will stop and give you the following message: "The construction has a Mechanism".

When the analysis is ready, the results of the whole model or a selection of elements can be visualised by contour plots of the stresses and a deformed shape plot. Also a vector plot of the principal stresses can be generated.

Finally the numerical results can be written in a report.
 
 

1.4 Technical Information

1.4.1 Elements

The following elements are available:
 

BARD Two Nodal Axial truss element
BEAM Two Nodal Beam Bending Element
TRIM Three Nodal Membrane Element
QUA4D Four Nodal Membrane Element
QUARD Four Nodal Rectangular Membrane Element
PLA4D Four Nodal Plate bending Element
PLARD Four Nodal Rectangular Plate bending Element
QUARS Four Nodal Rectangular Stress based Membrane Element
QUATRI Four Nodal Membrane Element built from four TRIM elements

Chapter 4 presents the full description of the elements.
 

1.4.2 Stress Convention

Line Element stresses
Sx      Positive for tension
Sby    Positive when outer fibre in local z-direction is in tension
Sbz    Positive when outer fibre in local y-direction is in tension
Sxy    Hold
Stx     Hold

Finite Elements
Sx      Positive for tension
Sy      Positive for tension
Sbx    Positive when outer fibre in local z-direction is in tension
Sby    Positive when outer fibre in local z-direction is in tension
Sxy    Hold
Stz     Hold

1.4.3 Files

The following program files are used: 

Fesawin.exe     Finite Element analysis Pre and Post Processor
FesaWin.ico     Icon
Fesawin.hlp     User manual readable within Pre-Post Processor Ascii Format
Fesawin.doc     User manual Word 97 Format
Eltyp.dat       Element data file
Plat.elm        Plate element data file
Matsol.exe      Model Solver (Can also run without Fesawin)
Matsol.ico      Icon
License.dat     License agreement Code
Decmem.dat      Memory settings
Defaults.dat    Saved program setting
The following model files are used: 
Root.tek        Model file with nodal co-ordinates, element definition and view settings
Root.mlt        Group file containing all the group data
Root.gra        contains the graphic element definitions
Root.vpl        The constraint
Root.knk        The applied loads
The following analysis files are used: 
Root.dat        Geometrical data file
Root.mat        Upper triangle of unconstrained stiffness matrix
The following result files are used: 
Root.nsr        Nodal stress report
Root.nsa        Nodal stress average report
Root.lsr        Local element stress report of element centre
Root.gsr        Global element stress report of element centre
Root.rvp        Displacement report
*.rpt   Analysis report file
2.0 Controls
This chapter presents all the controls the user has over the program.

Figure 1 presents the look of the program interface. The interface is divided in a main menu, the views, four or one view, the command line, the status line, the snap button and the selection box. The three fields next to the selection box are used for the x, y and z co-ordinates of a selected point. Each view has scroll bars a zoom in <+> and zoom out <-> button, and an autoscale button <Auto> to fit the complete model into the view.

Figure 1: User Interface of Pre and Post-Processor.
The main program controls are:
Mouse actions
Main menu
Command line
The next sections describe these controls in detail.

2.1 Mouse actions

The mouse actions depend on the active mode of the program. At the status line, which is located at the left bottom of the main window, the mode and the object on which the mode works is displayed.

Select mode
During editing and adding objects it is important to realise what the active selections are. Some times when you want something to happen and it does not work, check the active selections, as this may be the source of your trouble.

What you select, is defined by the check marks on the selection menu.

How you select it, is defined by the SELECTION box at the bottom of the screen. The following combinations are possible:

  • Single: Nodes, elements, graph nodes, graph elements
  • Window: Nodes, Elements
  • Group: Elements
  • All: Nodes, Elements, graph nodes, graph elements
An item can be selected with <Left mouse Button>. Click <Right mouse Button> once to stop selecting and to switch over to the Move Mode. Note; only nodes can be moved.

To deselect click <Right mouse Button> several time.

Clicking on an item, which is already selected, will remove that item from the selection list.

Move mode
Selected nodes can be moved either by mouse action or by the "command line".

Move by mouse action.
A selection of nodes can be moved by defining a reference node and a node to move to. All selected nodes will be moved by the vector spanned by the reference node and move to node.

When Drag/Drop is enabled [edit, drag/drop], nodes can be moved by holding down the <left Mouse Button> at any time.

Move by Commands.
See section 2.3.
 
Add mode
Use the <Snap on/off> button at the bottom of the main window to control the snapping on nodes during adding. When snap is on and a mouse click is too far from a node, snapping will not occur.
 
 

2.2 Main Menu

This chapter describes the options of the main menu.

2.2.1 File

[New]
This option will delete the model from memory and present a new empty work field.

[Open]
This option will delete an existing model from memory and load a new model from disk into the memory of the program.

[Save]
This option will save the current model in memory on disk.

[Print]
The print option will send a plot of view 1 to the printer.

[Save Settings]
Program and view settings will be saved on disk in the file; defaults.dat .

[Get Settings]
To retrieve the saved settings

[Model Size]
This option presents a form that enables the user to define the maximum memory size that the program should reserve. These settings can be changed during a session. It is advised to check the declared sizes regularly as the program will crash when the model becomes bigger than the reserved memory allows. Use Main Menu: [INFO, Model Info] to review the memory use of your model.

Do not reserve too much space as this could reduce the speed of the program.

[Exit]
This will exit the Fesawin session.
 
 

2.2.2 Edit

[Undo]
The undo option is only available to undo moving of Finite Element nodes.

[Drag/Drop]
When this option is Checked, graphical nodes and FE Nodes can be dragged and dropped. It is advised to disable drag and drop to avoid corrupting the model.

[Cut]
This option will copy and delete the selected FE elements, nodes and graphical elements.

[Copy]
This option will copy the selected FE elements, nodes and graphical elements.

[Paste]
This option will past the copied elements and nodes and place them at the same locations as where they were copied. As the pasted elements and nodes are still selected they can be moved by mouse action or by entering move commands at the command line.

To deselect and accept the pasted elements and nodes press <right mouse button> several times. When "check node merge and element merge" is on, see [SETTINGS, OPTIONS…], each node and element from the selection will be checked and doubles will be deleted.

[Modify Selection]
This option can be used to modify or edit the properties of the selected items.

It is advised to select one type of item for modification. Depending on the active selection the following modification can be done:

Modify Finite Elements:
This option presents a form, which allows modification of the group name and/or element type of a selection of elements.

  1. First select the elements which should be modified.
  2. Do: [EDIT, MODIFY SELECTION…]
  3. Set the selection criteria element type and group name.
  4. Define the change action to be performed in the lower half of the form by choosing an option in the element type and or group name boxes.
  5. When ready press <APPLY> and the change will be performed.
Modify Finite element nodes:
This option presents a form, which allows modification of the node attributes (Boundary conditions) of a selection of nodes.
  1. First select the nodes that should be modified.
  2. Do: [EDIT, MODIFY SELECTION…]
Use the buttons on the first frame to select between Loads or Constrains.

The second frame controls which nodes of the selection should be modified. If all nodes of the selection should be modified then chose "Selection". If you want to modify or review one of the nodes of the selection, select the node from the pull down box.

Note: The numerical values of the boundary conditions are presented, when you select one individual node.

The third frame presents six fields to enter the values of the boundary conditions. For constrains the following rules apply:
  • No constrain : Empty input field
  • Fixed : Fill in a 0
  • Prescribed displacement : Fill in value of displacement
For loads the following rules apply:
  • No Load : Empty input field
  • Prescribed load : Fill in Value of load
 
When <APPLY> is pressed the boundary conditions of the selected nodes will be replaced by the entered values of the input fields.

Modify Graphic Elements.
This option presents a form, which allows modification of the graphic element properties of one graphical element. The fields on the form are described as follows:
"Element ID"
This field can not be modified and present the identification number of the selected graphical element.

"Element Type"
This field can not be modified and presents the type of the selected element, which could be:

  • Line
  • Arc
  • Circle
"Radius"
This field is only visible when element type is "Circle". This input field allows you to enter the radius of a circle segment. The beginning, end point and plane in which the circle lies will not change.

"Nodes"
This field controls the number of nodes on the graphical element. Minimum value is two, which are the beginning and end nodes. The intermediate nodes on a graphical element are not snapable and can not be moved individually.

"Spaces"
This field does basically the same as "Nodes", except that the input is number of spaces between the nodes, in stead of number of nodes. Minimum value is 1 (one). Relation with "Nodes" is: "Spaces" = "Nodes" – 1

"Distribution Factor"
This factor controls the distribution of the nodes over the graphical element. The factor is defined by the ratio between the first and last spacing between the nodes.
 
 

2.2.3 Select

When the selection method is "Single", pointing at the objects and clicking the <left mouse button> does the selection of the nodes and elements.

When the selection method is "Window", clicking once with <left mouse button> for the first corner of the window and another time for the opposite corner does the selection of the nodes and elements. Do not drag the window.

Use <right mouse button> several times to deselect.

[Nodes]
This option should be checked when you want to select Finite Element Nodes.

[Elements]
This option should be checked when you want to select Finite Elements.

[Constrains]
Disabled

[Loads]
Disabled

Loads and constrains can not be selected. To edit loads and constrains select the node and do [EDIT, MODIFY SELECTION,...]

[Graphic nodes]
This selection allows you to select the graphic nodes for editing. Only the nodes used to define the graphic element can be selected. Intermediate nodes can not be selected.

[Graphic Elements]
When checked graphical elements can be selected. To modify a graphical element double click with the <left mouse button>, and a form will appear which allows you to modify the graphic element. See Chapter 2.2.

2.2.4Add

[Ready]
This option will be enabled when the program is in the adding mode. Select this option to stop adding. At the bottom of the screen a button with caption "Ready" will appear when the program is in the adding mode. This button does the same as this menu option.

[Free Node]
This option enables the user to place free finite element nodes.

[Elements,…]
When selected, a form will appear which allows you to chose the element type you want to use and to which group these elements should be assigned.

The order in which the nodes of an elements are defined determine the local axis of that element. Clockwise definition of the nodes will create a local axis system with the Z-axis pointing away from the viewer. The X-axis is defined from node 1 to node 2.

[Mesh]
This option starts the mesh generation module.

The first form is used to select between 2-D meshes or 3-D meshes.

Note: 3-D solid meshes are not included in this version of FESAWIN.
The next form presents the 2-D mesh generator.

The generator uses graphical elements as edges to define the borders of the mesh. Before using the generator first define a closed area using graphical elements with three or four sides.

Activate mesh generator

- The first field defines the mesh type to be generated, the types are:

Quad
Four sided area which will be filled by four nodal elements, opposite sides should have equal number of nodes.
Triang
Three sided area which will be filled by three nodal elements,all sides should have equal number of nodes.
Line
Line which will be meshed with two nodal elements.
Transit
Four sided area which will be filled by four nodal elements. This option is disabled.
- The second field defines the element type to be used.

- The third field defines to which group these elements should be assigned.

The drawing in the second frame shows the order in which the edges should be defined.

The buttons on the third frame can be pressed to select the graphical components of the edges.
Each edge may consist of more than one graphical element. The order in which the graphics are selected is not important, but the edge should be continuously.

When all edges are selected, the mesh can be generated by pressing <Generate Mesh>. Press either <Accept> to accept the proposed mesh or <Reset> to reject. The generator is ready to generate a new mesh after <Reset> or <Accept>. The proposed mesh is only showed in view 1.

[Constrains] or [Loads]
This option presents a form to modify or review the boundary conditions.

Use the buttons on the first frame to select between Loads or Constrains.

The second frame controls which nodes of the selection should be modified. If all nodes of the selection should be modified then chose "Selection". If you want to modify or review one of the nodes of the selection, select the node from the pull down box.

Note: The numerical values of the boundary conditions are presented, when you select one individual node.

The third frame present six fields to enter the values of the boundary conditions. For constrains the following rules apply:

  • No constrain : Empty input field
  • Fixed : Fill in a 0
  • Prescribed displacement : Fill in value of displacement
For loads the following rules apply:
  • No Load : Empty input field
  • Prescribed load : Fill in Value of load
When <APPLY> is pressed the boundary conditions of the selected nodes will be replaced by the entered values of the input fields.
[Graphics, line]
This option activates the adding line mode. Use <left mouse button> or command line to define the nodes of the line. By clicking <Right mouse button> once a new line string can be started. Use <Right mouse button> twice to stop the adding line mode.

A line is defined by one begin and one end node.

[Graphics, Circle]
This option activates the adding circle mode. Use <left mouse button> or command line to define the nodes of the circle. By clicking <Right mouse button> once a new string can be started. Use <Right mouse button> twice to stop the adding circle mode.

A circle section is defined by three nodes that may not coincide. The three nodes span the plane in which the circle section is situated. The first node is the starting point, the second node is the end of the circle segment and the third node defines the radius and the plain. Use [Edit, Modify selection,…] to change the radius of the circle segment.

The third node can be selected and replaced by mouse action or command line.

2.2.5 Define

[Group]
This form is used to define the element group names and properties. To define a new group, just enter the new name in the group name field. Groups can not be deleted.

The element groups are also used as nodal stress average groups. This means that per element group the nodal stress averages are calculated and reported.

The following properties are to be defined:

2.2.6 Setting

[Colors]
This form allows the user to change the color settings of the program. To save the color settings for a next session, do [FILE, SAVE SETTINGS].

[Font]
This option allows the user to set the font properties of the node and element labels. To save the font settings for a next session, do [FILE, SAVE SETTINGS].

[Scrollbar]
To display the scrollbars check this option.

[Global Axis]
To display the global axis check this option.

The global axis are displayed in the left lower corner of each view. The axis are color marked as follows:

[Local Axis]
Check this option to display the elements local axis systems. The axis are color marked as follows: [Options]
This form allows the user to chose auto merging of nodes or elements. Also the auto renumber before saving option can be controlled.
 
 

2.2.7 View

[View Set]
This option shows a form, which controls the settings of the view.

-View type-
You can chose to display only one view or four views at the same time.
<Copy>, <Paste>
These functions can be used to copy and paste view settings from view to view.

-View angle-
This defines your view direction regarding the horizontal and vertical plane.
The buttons on this frame sets four pre-defined view angle settings.

-View point-
This defines the point at which you are looking at through your view. When <AutoScale> is used the middle of the model will be set as the viewpoint.

-View settings-
This defines the scaling factor and your distance relative to the view point.

The "Unit Vector Length" is a value which is used to size the graphics of the boundary conditions and the scale of the deformed shape plot relative to the view size. The view width and height is 10.

<Autoscale>
The autoscale routine sets the middle of your model as the view point and sets the scale to fit the model in the view.

Click on the little views on this form to select another view.

-Define Elements to view-,
Select one of the following options:

*    All Elements    :All elements will be shown in the view
*    Group           :Select one group of elements which should be shown in the view.
*    Selection       :Press <Select> and select the elements that should be shown in the
                      view, press <Right mouse button> to stop selecting.

It should be noted that Finite Element Nodes which are not connected to an element will not be visible and can not be selected when a selection of elements is shown. When <All Elements> are selected also all nodes will be shown.

When ready press <OK>.

[Redraw]
This options redraws all views.

[Nodes] , [Elements], …..
This options controls if the attributes or objects are drawn.
 
 

2.2.8 Analyse

[Options..]
This form controls the analysis.

-General-,
Chose between a 2-D or a 3-D analysis. If a 2-D analysis is chosen only the x and y co-ordinates are considered for analysis.

When "Clear memory before analysis" is checked, the memory used by the model is cleared to free RAM for the analysis. This is advisable when a very large model is to be analysed. When a small model is run uncheck this option as the clearing of the memory is not needed and will probably take more time than the analysis.

-Pre-processor-,
When "Renumber model nodes" is checked, the model will be renumber before saving and analysis. Since this action takes some time it can be switched off. But one should be aware that if this option is off and nodes have been added the node numbering could be far from optimal which will enlarge the bandwidth and consequently your matrix size and solving time drastically.

-Solver-,
"Compile Stiffness matrix" may be switched off when no changes of the model have occurred since the last run. Boundary conditions (Constrains and loads) are not applied to the saved stiffness matrix, so a rerun with different boundary conditions without compiling the stiffness matrix is allowed.

When "Solve Displacements" is checked the compiled stiffness matrix is read from file, the boundary conditions are applied and the displacements are solved and written to file.

-Post-Processor-,
The options on this frame controls which stresses are calculated using the latest displacements found in file.

[Analyse]
This menu entry will start MatSol, which is the FesaWin Finite Element analyser. MatSol can also be started outside FesaWin, which allows you to continue working on a model while another model is running. Do not work and run at the same model at the same time. And do not run more then one MatSol analysis at the same time as they may interfere with each other.

For large problems it is advised to run MatSol outside FesaWin as FesaWin will continue to use processor time when active.
 
 

2.2.9 Post-Process

[Loadcase] (Not Available)
This option will allow the user to select the loadcase for post-processing.

[Displacement]
When checked, the deformed shape of the active loadcase will be plotted. The displacement will be scaled relative to the view size using the "Unit Vector Length" value as maximum displacement. By changing this value the deformations can be altered for clarity, do [View, view set..].

[Nodal Stress Contour]
When checked, the nodal stress average contour of the active loadcase will be plotted. To select the type of stress component do: [Post-Process, Option..].

[Principal stress vector plot]
When checked, a 2-D vector representation of the principal stresses of the active loadcase will be plotted. The length of the vectors can be controlled by changing the "Unit Vector Length", do [View, view set..]. Note: This option only work well for 2-D models.

[Element Stress]
When checked, the line element stresses of the active loadcase will be color plotted. To select the type of stress component do: [Post-Process, Option..].

[Report..]
This entry will activate the report generator.

Check the reports you want to write into your report file and do "Write".

Chose a filename and save the report. The report is an unformatted ASCII file. To print the report, use another utility to do so.

To browse through the report select "View". Select the file with extension .rpt and the browser will be opened.

[Options..]
This form present the options for post processing.

-Stress Component Selection-
The following stress components are available:
Direct stresses at element center line or center plane.
    Sx
    Sy
    Sz
Shear stresses at element center line or center plane
    Sxy
    Sxz
    Syz
Bending stress around axis
    Sbx
    Sby
    Sbz
Torsion stresses around axis
    Stx
    Sty
    Stz

Combined stress (Von Mises)
    VM

<Local/Global>
This button allows the user to chose between a local coordinate system or global system.
It should be noted that for the calculation of local nodal stress averages it is required that two adjacent elements within the same element group should have the same local coordinate system. If not stresses of different directions are averaged which will give wrong results. If local coordinate systems within a group of elements are not uniform use global stresses. The combined stress component is direction independant and will therfore be correct and similar for both local or global.
 

-Define Elements to Post-Process-
Select one of the following options:

*    All Elements    :All elements will be shown in the view
*    Group           :Select one group of elements which should be shown in the view.
*    Selection       :Press <Select> and select the elements that should be shown in the
                      view, press <Right mouse button> to stop selecting.
 
 

-Stress Index Scale-
This options allows the user to control the range of stress values to be plotted.
Select <Auto> to plot the full range of stresses found in the databae of the selected elements

Select <Manual> to define a range of stresses to be plotted.
 

2.2.10 Info

[User manual..]
This option displays the user manual.

[About..]
General information about FesaWin can be found here.

[Model Info..]
This option presents the size of the model and the size of the declared space for the different model arrays. Perform a regular check and declare more space if needed. Warning; the program will crash if the model gets greater than declared for!

[License..]
This form presents your licence level and allows you to change your licence.
 
 

2.3 Command line

The command line, located at the bottom of the main window, can be used to direct enter the co-ordinates of a selection of nodes during adding or moving.

The commands should be typed in lower cases and are activated by pressing the <Enter> button left of the Command Line.

The pull down button at the right of the command line shows the previous commands, which can be selected for reuse.

The following commands are available.

Replace the red marked text by numerical values, type the commands into the command line and press <Enter> to activate.
The commends should be typed into the command
 

3.0 Creating and Analysing a model
 

This chapter describes how to create a Finite element model in FesaWin. It is assumed that the user is familiar with finite element analysis.

3.1 Analysis setup
 
 

3.1.1 Units

The program works dimensionless. This means that any consistence set of units can be used. The following units are advised:

Be consistence with the units otherwise the results are not correct.
 
 

3.1.2 Type of analyses

The following two types of analysis are available:

When a 2-D analysis is considered, the model should be placed in the x-y plane only. Select only one view window and set the view direction at X-Y.
Do: [view, viewset….] ,<Single>, <X-Y>, <OK>.
For a 3-D analysis the model may be built anywhere. It is recommended to select all four views and to look at your model through each view with an other perspective.
Do: [view, viewset….] ,<Multi>, set for each view the preferred view perspective by using <ISO>, <X-Y, <X-Z>, or <Y-Z>.

3.1.3 Declare workspace

Use the model size option on the main menu file menu to size the workspace in memory you need for your model. During modelling the workspace may be increased if required. But, if the workspace is to small for the model, errors may occur and the model in memory could be damaged. If this occurs, do not save the model but exit without saving, restart FesaWin, increase workspace, and retrieve the model from disk.

DO: [File, Model Size…], fill in the required size and press <OK>.

Do not make the total declared size to large as this may decrease the speed of the computer.
 
 

3.2 Placing elements

To build a finite element model, elements have to be placed and the element and material properties have to be defined.
 
 

3.2.1 Defining element groups

Elements are assigned to a named group. Before you place the elements it is advisable to define the group names first. The reasons to assign elements to certain groups are as follows:

  • Material properties and element properties like thickness and section properties can be set per group of elements
  • nodal stress averages are generated per group of elements,
  • groups of elements can easily be selected and modified,
  • element groups can be switched on or off for post-processing.
To define groups use [define…] of the main menu.
 
 

3.2.2 Single element placement

When the model is small, or for any other reason you want to place elements one by one, you should first place the nodes.

Use [add, Free Node] of the main menu to place new nodes.

When the element nodes are placed the actual finite elements can be placed by using [add, Element…] of the main menu.

Select the type of element you want to place and the group name for the element. To define the elements, press <Add> and select the nodes of the elements using <left mouse button>.

When finished press <right mouse button> to stop placing.

To check if elements are really placed and at the right location it is advised to switch element labelling on. This option will write the element rank number in the middle of the element. Use [view, element label, number] to switch this option on or off.
 
 

3.2.3 Patching and Meshing

When large quantities of elements are required it is more easy and faster to use the mesh generator.

The mesh generator can place line elements on a graphic line and membrane or plate elements on a surface defined by graphic elements.

Line Elements,
To place line elements like axial rods or beam elements work as follows:

  1. Draw the line string using straight lines or circle sections. Do: [Add, Graphics, line/circle]. To be sure that the end and beginning of each line segment is connected to each other, switch snapping on. Use the <Snap on> button at the bottom of the main window to do so.
  2. Define the number of finite elements to be placed on each graphic element by sub divide the graphic elements. First use [Select, Graphic Elements] to switch to graphic element selection. Double click a graphic and the "Edit Graphic Elements" form will appear. Set the number of spaces on this form equal to the number of elements you want on this graphic. When ready press <OK>.
  3. Now start the mesh generator, [Add, Mesh…], press <2_D Mesh>.
  4. Set the "Mesh Type" to "Line"
  5. Select the element type and group.
  6. Press <Edge 1> and select the graphic elements using <left mouse button>. When ready press <Right mouse Button>.
  7. Now press <Generate Mesh> and review the result as shown in view 1.
  8. When acceptable press <Accept> else press <Reset>.
  9. When ready press <Ready>
To place three or four nodal elements like membranes or plate elements work as follows:
  1. Define the surface to be meshed using straight lines or circle sections [Add, Graphics, line/circle]. To be sure that the end and beginning of each line segment is connected to each other, switch snapping on. Use <Snap on> at the bottom of the main menu to do so. To create a mesh with four nodal elements, the surface should be defined by four sides. To create a mesh with three nodal elements, the surface should be defined by three sides.
  2. Define the number of finite elements to be placed along each graphic element by sub divide the graphic elements. First use [Select, Graphic Elements] to switch to graphic element selection. Double click a graphic and the "Edit Graphic Elements" form will appear. Set the number of spaces on this form equal to the number of elements you want along this graphic. When ready press <OK>. Note that for a four nodal mesh, opposite sides of the surface should have equal sub division. For a three nodal mesh all three sides should have equal sub division.
  3. Now start the mesh generator, [Add, Mesh…], press <2_D Mesh>.
  4. Set the "Mesh Type" to "Quad" or "Triang"
  5. Select the element type and group.
  6. Press <Edge #> and select the graphic elements using <left mouse button>. When ready press <Right mouse Button>. Do this for each edge and mind the order of the edges.
  7. Now press <Generate Mesh> and review the result. See figure 3.1 and 3.2 for examples of a three and a four nodal mesh.
  8. When acceptable press <Accept> else press <Reset>.
  9. When ready press <Ready>
Figure 3.1 Three nodal Mesh (Click on picture to enlarge)



 

Figure 3.2 Four nodal mesh (Click on picture to enlarge)



3.3 Defining boundary condition

When the elements are placed the boundary conditions should be defined.

To define the loads work as follows:

  1. First use [Select, Nodes] to switch to finite element nodes selection.
  2. Select all nodes with equal loads
  3. Do: [Add, Loads..]
  4. Enter the values of the load components
  5. Press <Apply>
  6. Review the results in view 1
  7. Press <Ready>
To define the constraints work as follows:
  1. First use [Select, Nodes] to switch to finite element nodes selection.
  2. Select all nodes with equal constraints
  3. Do: [Add, Constraints..]
  4. Enter the values of the constraint components
  5. Press <Apply>
  6. Review the results in view 1
  7. Press <Ready>
3.4 Analysing model

When the model is ready, the analyses can be performed. Save your model first! When a very large model is to be run, it is advisable not to start the analysis from FesaWin, but use MatSol instead, as this will run faster. MatSol is a seperate executable which was included with FesaWin. Search in the directory of FesaWin and double click MatSol.exe to start.

First the options of the analysis have to be set. Within FesaWin do [Analysis, options..] or within MatSol press <Options>, and select the right options. If you are running a simple 2-D analysis set the analyses type to 2-D.

When this is done, press <Run> in MatSol or do [Analysis, Analysis] in FesaWin.
 
 

3.5 Post-processing

When the analyses was successful the results can be looked at graphically or numerical.

To look at the deformed shape of the model, use [Post-Process, Displacements]

To review the stresses in the construction use one of the stress plot options of Post-Process menu.

The stress plots can be controlled by using [Post-Process, Options]. Use this form to select which stress component and from which elements you want to see the stress plots.

Use [Post-Process, Report…] to create a numerical report of the input and output information of the model.
Use [File, Print...] to plot the contents of view 1.
 

4.0 Element description
 
 
4.1 BARD Two Nodal Axial rod element
Description,
This element is a simple axial truss, which can only take load in the direction of the element definition line.

Nodes : 2
Local Degrees of freedom : 1 per node

Group Properties,
E modulus
Poisson ratio
Area

Local stress Output,
LSX Stress in local X direction

Performance,
This is an analytical element, which means that the exact solution of the stress and strain relation is known and used.
 
 

4.2 BEAM Two Nodal Beam Bending Element
 
Description,
This element is a beam bending element, which can take load in all degrees of freedom.
 

Nodes : 2
Local Degrees of freedom : 6 per node

Group Properties,
E modulus
Poisson ratio
Area
Rot
Ixx
Wxx
Iyy
Wyy
Izz
Wzz
 

Local stress Output,
LSX Stress in local X direction
(bending stresses are not yet included in the stress output of this element)

Performance,
This is an analytical element, which means that the exact solution of the stress and strain relation is known and used.
 
 

4.3 TRIM Three Nodal Membrane Element
Description,
This element is a displacement based triangular membrane element with two degrees of freedom per node.

Nodes : 3
Local Degrees of freedom : 2 per node

Group Properties,
E modulus
Poisson ratio
Thickness

Local stress Output,
LSX Direct stress in local X direction
LSY Direct stress in local Y direction
LSXY Shear stress in local XY Plane

Performance,
This is not an analytical element, which means that an approximate solution of the stress and strain relation is used.
 
 

4.4 To be continued…