previous MODELING A CANTILEVERED BEAM’S VIBRATION USING 4 NODE SHELL ELEMENTS
a) Log on to the computer
b) Click START (lower left corner of the Windows Desktop), go to Programs, Select MSC (common), Select MSC Patran9.0.
TM = Top Menu. This refers to the horizontal menu options residing at the top of the screen after PATRAN has been initiated.
RM = Right Menu. This refers to the menus that pop up after an option has been chosen from the top menu. These menus reside on the far right side of the PATRAN desktop.
SM = Subordinate Menu. This referees to the menus that pop up from options selected in the right menu.
Click = Unless otherwise stated, this indicates a click with the left mouse button.
Boldface will indicate text that occurs in the PATRAN menus.
Italics text will indicate text that you must enter into text boxes in the PATRAN menus or text that you choose in a menu scroll box.
1. Our first step is to create a new database:
From the TM choose File In the resulting pull down menu choose New
A SM called New Database pops up
Turn on (checked) Modify Preferences
Under File Name enter fin.db
Click OK
2. Next set the analysis preference:
A New Model Preferences window will appear as a RM
Under Tolerance choose Based on Model Set Model Dimension to 0.2
Under Analysis Code choose MSC/NASTRAN
Choose Analysis Type = Thermal
click OK
3. The geometry of the beam will be determined next: Select Geometry from TM.
On RM, select Action= Create, Object= Curve, Method= XYZ
Note Curve ID List has a 1.
Refer. Coordinate Frame should be Coord 0
Set Vector Coordinates List to 0.2 0 0 (You will be drawing lines (vectors) with these xyz components.)
Origin Coordinates List = 0 0 0 Click APPLY. (A line from origin to point 0.2,0,0 should appear on screen.)
Make second curve: With same vector, set Origin Coordinates List to 0 0.01 0.
Click Apply. (A second curve appears on the screen.)
Now create a surface between the curves.
On the Geometry RM, choose Action= Create; Object= Surface; Method= Curve.
Set Option to 2 Curve.
Note there is a Starting Curve List and Ending Curve List.
Click in the Starting Curve List box. .Select the first curve by using the mouse.
Click the small box on curve 1 on the screen. Click in the Ending Curve List box. Then click on curve 2. Note a surface is created.
4. Create the finite elements. On the TM select Elements and get a RM.
Choose Action= Create; Object=Mesh; Type= Surface
Choose the size of the elements. Type in Global Edge Length: 0.01
Select Isomesh. Click in Surface List box. Select the Surface 1 with the cursor.
Click Apply. Note the model has 20 elements.
5. Create Boundary conditions
At TM, select Load/BC’s. Get RM.
Now create the convection characteristics for the bottom of the fin
Chose Action=create, Object=convection, type=element uniform
Name the convection BC. In New Set Name, type top-convec Select Target Element Type = 2D
Click Input Data. Get submenu. Type 30 for convection coefficient (w/m2c) for top surface convection. Type 25 for ambient temp. Click OK. Back in Load/ BC menu, click Select Application Region box
Select FEM as the Geometry Filter.
Click in Select 2D Elements or Edges box
Using mouse, click on all the elements. (Hold shift down for multiple selections.) Click Add.
The application region box should list the elements 1:20. Click OK Back in Load/BC menu click Apply.
Now create the convection characteristics for the bottom of the fin
Chose Action=create, Object=convection, type=element uniform
Name the convection BC. In New Set Name, type bot-convec Select Target Element Type = 2D
Click Input Data. Get submenu. Type 30 for convection coefficient (w/m2c) for bottom surface convection. Type 25 for ambient temp. Click OK.
Back in Load/ BC menu, click Select Application Region box
Select FEM as the Geometry Filter.
Click in Select 2D Elements or Edges box
Using mouse, click on all the elements. (Hold shift down for multiple selections.) Click Add.
The application region box should list the elements 1:20. Click OK
Back in Load/BC menu click Apply.
Now create the base temperature BC.
In Load/BC RM Action=create, Object=Temp, type=nodal
In New Set Name type Basetemp. Click on Input Data.
In submenu Input Data, type 200 in Temperature box. Click OK.
Back in Load/BC SM, click on Select Application Region.
In submenu, select FEM as Geometry Filter.
Click on Select Nodes.
Using mouse, select the nodes 1 and 22 at the extreme left of the model. Click Add. Click OK.
Back in Load/BC menu, click Apply. (The screen should show 200 at nodes 1 and 22.)
6. Create and select material
On TM select Materials.
In submenu, Action=create, Object=isotropic, method=manual input.
In Material Name box, type aluminum. Click Input Properties.
In submenu, Input Options, enter thermal conductivity as 177. (w/m2k).
Click OK. If SM does not disappear, Click Cancel.
Back in the RM , Click Apply
In TM, select Properties
In submenu Action=create, Object=2D, Type=shell.
In Property Set Name type shell_prop.
Click on Input Properties In submenu, click on Aluminum in the Material Property Sets box.
M: Aluminum appears in the Material Name box at the top of the form.
Set Thickness= 0.002 Click OK.
Back in Element Properties, click Select members.
Use mouse to select the entire model. (You can click and draw a box around the entire model to select it.) Click Add. Click Apply.
7. Load Boundary Conditions
In order to have both the convection on top and on the bottom as well as the and base temperature
BC on the model, all 3 boundary conditions must be combined into a single load case.
In TM, select Load Cases.
In SM, Action=Create, Load case name, type fin_case.
In Description, type: h=30 on fin with base= 200C. and ambient=25C.
Click on Assign/Prioritize BC under the Select Individual Loads/BC Click on conve_bot-convec and then on conve_top-convec and then on temp_basetemp
As you click on these each of the 3 is added to the Assigned Load/BC
At the bottom of the menu, click OK Back in the Load Case RM, click Apply
8. Analyze (solve) for temperature.
In TM select Analysis. In SM, Action= Analysis, Object = entire model, Method = Full Run, Job name = fin Click translation Parameters and set output to Op2 & Print
Click, OK Back in the Analysis RM, click Solution Type
Choose Steady State Analysis
Click OK
Back in the Analysis RM, choose Subcase Create
Under Available Subcases, select fin_case
Under Available Loadcases, select fin_case
Click Apply
Click Cancel
Back in the Analysis RM, click Subcase Select Under Subcases for Solution Sequence 153, select fin_case
Under Subcases Selected, click on Default (this removes default from the list)
Click OK Back in Analysis SM Click Apply
A RM will appear called Results
Set Action = Create
Object = Quick Plot
You can display different results, but the main focus will be on the temperatures.
11. Next you will end your MSC/PATRAN session by saving your database and exiting.
On the TM select File From the pull down menu select Save
On the TM select File From the pull down menu select Quit
I. THE PHYSICAL PROBLEM The problem you will model is a fin of aluminum alloy, 0.2 m long, 0.002 m thick and large width. This is the type of fin that might provide air-cooling on a motorcycle engine. For the finite element model, we consider a representative strip of the fin 0.01 m in depth (shown as the region between the dotted lines in the drawing). The 200-degree wall is representative of the hot temperature of the engine. Our goal is to find the temperature distribution down the fin. If the outside tip of the engine is too hot, it can be a safety concern. Heat is conducted down the fin (away from the heat source of the engine) and heat is also lost through convection from the top and bottom surfaces to the air. The ambient temperature of the air is known to be 25 C° and the convection coefficient (film coefficient) is known to be 30 (W/m2) . The fin itself is made of aluminum which has a conductivity of 177 (W/m2 K).
II. THINKING ABOUT THE MECHANICS The analytic solution for the temperatures for this problem is readily available. Any Heat Transfer text will provide equations for the temperature distribution of a fin considering conduction away from the heat source and convection from the top and bottom surfaces. These results can be used to give basic analytic comparison solutions for certain sections of the structure. Note that we assume no radiation occurs and that only the top and bottom surfaces have significant convection heat transfer (the convection from the edges of the fin is neglected). These assumptions are normal for a first level analysis where the temperatures are in the ranges used in this problem.
III. GEOMETRIC AND FINITE ELEMENT MODEL
As is the standard procedure for building MSC/Patran models, we will build the geometry first and then construct a finite element mesh on that geometry. The geometry will proceed from creation of curves to a surface for this simple model. Next, we will use 4 node 2-dimensional elements to model the fin. Next, the material and element properties will be entered. We will set the wall temperature and the convection characteristics for the top and bottom of the fin. Finally, the nodes must be equivalenced before the analysis is ready to run.
As is the standard procedure for building MSC/Patran models, we will build the geometry first and then construct a finite element mesh on that geometry. The geometry will proceed from creation of curves to a surface for this simple model. Next, we will use 4 node 2-dimensional elements to model the fin. Next, the material and element properties will be entered. We will set the wall temperature and the convection characteristics for the top and bottom of the fin. Finally, the nodes must be equivalenced before the analysis is ready to run.
IV. FINITE ELEMENT THEORY
The exact details of the formulation of the 4 node 2-d elements in MSC/Nastran is rather complicated. However, the basic formulation of the 2-d thermal element is not extremely difficult and will provide us with sufficient background information to begin to understand the general application areas and convergence of these elements. This basic formulation for the 2-d thermal, linear, quasistatic element can be found in most any Finite Element Analysis text (see for example Finite Elements for Stress Analysis, by R.D. Cook, John Wiley & Sons, 1995.).
The exact details of the formulation of the 4 node 2-d elements in MSC/Nastran is rather complicated. However, the basic formulation of the 2-d thermal element is not extremely difficult and will provide us with sufficient background information to begin to understand the general application areas and convergence of these elements. This basic formulation for the 2-d thermal, linear, quasistatic element can be found in most any Finite Element Analysis text (see for example Finite Elements for Stress Analysis, by R.D. Cook, John Wiley & Sons, 1995.).
V. INSTRUCTIONS FOR MODELING THE FIN USING MSC/PATRAN & MSC/NASTRAN
Preliminaries for using PATRAN include: a) Log on to the computer
b) Click START (lower left corner of the Windows Desktop), go to Programs, Select MSC (common), Select MSC Patran9.0.
The instructions below give details for modeling the thermal fin problem discussed above. The instructions are NOT as detailed as have been given in other problems as it is expected that you have begun to get a feel for how to do certain tasks in Patran.
In the instructions below, the following abbreviations and terms will be used: TM = Top Menu. This refers to the horizontal menu options residing at the top of the screen after PATRAN has been initiated.
RM = Right Menu. This refers to the menus that pop up after an option has been chosen from the top menu. These menus reside on the far right side of the PATRAN desktop.
SM = Subordinate Menu. This referees to the menus that pop up from options selected in the right menu.
Click = Unless otherwise stated, this indicates a click with the left mouse button.
Boldface will indicate text that occurs in the PATRAN menus.
Italics text will indicate text that you must enter into text boxes in the PATRAN menus or text that you choose in a menu scroll box.
1. Our first step is to create a new database:
From the TM choose File In the resulting pull down menu choose New
A SM called New Database pops up
Turn on (checked) Modify Preferences
Under File Name enter fin.db
Click OK
2. Next set the analysis preference:
A New Model Preferences window will appear as a RM
Under Tolerance choose Based on Model Set Model Dimension to 0.2
Under Analysis Code choose MSC/NASTRAN
Choose Analysis Type = Thermal
click OK
3. The geometry of the beam will be determined next: Select Geometry from TM.
On RM, select Action= Create, Object= Curve, Method= XYZ
Note Curve ID List has a 1.
Refer. Coordinate Frame should be Coord 0
Set Vector Coordinates List to 0.2 0 0 (You will be drawing lines (vectors) with these xyz components.)
Origin Coordinates List = 0 0 0 Click APPLY. (A line from origin to point 0.2,0,0 should appear on screen.)
Make second curve: With same vector, set Origin Coordinates List to 0 0.01 0.
Click Apply. (A second curve appears on the screen.)
Now create a surface between the curves.
On the Geometry RM, choose Action= Create; Object= Surface; Method= Curve.
Set Option to 2 Curve.
Note there is a Starting Curve List and Ending Curve List.
Click in the Starting Curve List box. .Select the first curve by using the mouse.
Click the small box on curve 1 on the screen. Click in the Ending Curve List box. Then click on curve 2. Note a surface is created.
4. Create the finite elements. On the TM select Elements and get a RM.
Choose Action= Create; Object=Mesh; Type= Surface
Choose the size of the elements. Type in Global Edge Length: 0.01
Select Isomesh. Click in Surface List box. Select the Surface 1 with the cursor.
Click Apply. Note the model has 20 elements.
5. Create Boundary conditions
At TM, select Load/BC’s. Get RM.
Now create the convection characteristics for the bottom of the fin
Chose Action=create, Object=convection, type=element uniform
Name the convection BC. In New Set Name, type top-convec Select Target Element Type = 2D
Click Input Data. Get submenu. Type 30 for convection coefficient (w/m2c) for top surface convection. Type 25 for ambient temp. Click OK. Back in Load/ BC menu, click Select Application Region box
Select FEM as the Geometry Filter.
Click in Select 2D Elements or Edges box
Using mouse, click on all the elements. (Hold shift down for multiple selections.) Click Add.
The application region box should list the elements 1:20. Click OK Back in Load/BC menu click Apply.
Now create the convection characteristics for the bottom of the fin
Chose Action=create, Object=convection, type=element uniform
Name the convection BC. In New Set Name, type bot-convec Select Target Element Type = 2D
Click Input Data. Get submenu. Type 30 for convection coefficient (w/m2c) for bottom surface convection. Type 25 for ambient temp. Click OK.
Back in Load/ BC menu, click Select Application Region box
Select FEM as the Geometry Filter.
Click in Select 2D Elements or Edges box
Using mouse, click on all the elements. (Hold shift down for multiple selections.) Click Add.
The application region box should list the elements 1:20. Click OK
Back in Load/BC menu click Apply.
Now create the base temperature BC.
In Load/BC RM Action=create, Object=Temp, type=nodal
In New Set Name type Basetemp. Click on Input Data.
In submenu Input Data, type 200 in Temperature box. Click OK.
Back in Load/BC SM, click on Select Application Region.
In submenu, select FEM as Geometry Filter.
Click on Select Nodes.
Using mouse, select the nodes 1 and 22 at the extreme left of the model. Click Add. Click OK.
Back in Load/BC menu, click Apply. (The screen should show 200 at nodes 1 and 22.)
6. Create and select material
On TM select Materials.
In submenu, Action=create, Object=isotropic, method=manual input.
In Material Name box, type aluminum. Click Input Properties.
In submenu, Input Options, enter thermal conductivity as 177. (w/m2k).
Click OK. If SM does not disappear, Click Cancel.
Back in the RM , Click Apply
In TM, select Properties
In submenu Action=create, Object=2D, Type=shell.
In Property Set Name type shell_prop.
Click on Input Properties In submenu, click on Aluminum in the Material Property Sets box.
M: Aluminum appears in the Material Name box at the top of the form.
Set Thickness= 0.002 Click OK.
Back in Element Properties, click Select members.
Use mouse to select the entire model. (You can click and draw a box around the entire model to select it.) Click Add. Click Apply.
7. Load Boundary Conditions
In order to have both the convection on top and on the bottom as well as the and base temperature
BC on the model, all 3 boundary conditions must be combined into a single load case.
In TM, select Load Cases.
In SM, Action=Create, Load case name, type fin_case.
In Description, type: h=30 on fin with base= 200C. and ambient=25C.
Click on Assign/Prioritize BC under the Select Individual Loads/BC Click on conve_bot-convec and then on conve_top-convec and then on temp_basetemp
As you click on these each of the 3 is added to the Assigned Load/BC
At the bottom of the menu, click OK Back in the Load Case RM, click Apply
8. Analyze (solve) for temperature.
In TM select Analysis. In SM, Action= Analysis, Object = entire model, Method = Full Run, Job name = fin Click translation Parameters and set output to Op2 & Print
Click, OK Back in the Analysis RM, click Solution Type
Choose Steady State Analysis
Click OK
Back in the Analysis RM, choose Subcase Create
Under Available Subcases, select fin_case
Under Available Loadcases, select fin_case
Click Apply
Click Cancel
Back in the Analysis RM, click Subcase Select Under Subcases for Solution Sequence 153, select fin_case
Under Subcases Selected, click on Default (this removes default from the list)
Click OK Back in Analysis SM Click Apply
9. To read in the results for post-processing
.In the RM=Analysis
Set Action = Read Output2; Object = Results Entities; Method = Translate
Click Select Results File
A SM appears called Select File Click the file fin.op2 (You may need to look in your home or root directory to find the file. If this file does not exist, then you have made a mistake in constructing your model. Go to Explorer (right-click on Start and choose Explore) and find the file fin.log and fin .f06. Open these files by double clicking on them and search for the word “error” or “fatal” to determine what your mistake is).
fin.op2 then appears in the File Name box
Click OK
(back in the Analysis menu)
Click Apply
10. Select the TM Results .In the RM=Analysis
Set Action = Read Output2; Object = Results Entities; Method = Translate
Click Select Results File
A SM appears called Select File Click the file fin.op2 (You may need to look in your home or root directory to find the file. If this file does not exist, then you have made a mistake in constructing your model. Go to Explorer (right-click on Start and choose Explore) and find the file fin.log and fin .f06. Open these files by double clicking on them and search for the word “error” or “fatal” to determine what your mistake is).
fin.op2 then appears in the File Name box
Click OK
(back in the Analysis menu)
Click Apply
A RM will appear called Results
Set Action = Create
Object = Quick Plot
You can display different results, but the main focus will be on the temperatures.
11. Next you will end your MSC/PATRAN session by saving your database and exiting.
On the TM select File From the pull down menu select Save
On the TM select File From the pull down menu select Quit
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