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A meshed 2D plate Temperature in a 2D plate

MENG 421 Assignment 5

Temperature and flux in a 2D plate









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Lecture notes -- Milestones, 1, 2, Tables, NGEN, Plane42, Plane55, Plane82,
Element 1, Elements 1-7, Element 1-49, Heat2d64.a,  

In Assignment 3 you created a bracket with the Ansys element Shell93, an 8-node structural shell. You used the 2D, 4-node Ansys element Plane42 for Assignment 4 to create an axisymmetric cylinder and then apply a mechanical load. For today's lesson, you will use a similar element, Ansys Plane55 with a thermal load. This element is a 2D, 4-node thermal solid. However, we will only use three nodes per element. You can use Plane55 in axisymmetric mode to create rods and pipes like you did with Plane42 for Assignment 4. Today you will program Ansys to find the temperature distribution in the plate subject to a temperature gradient on one edge of a 7x7 plate. The other three edges are insulated. If we let Ansys create the finite elements automatically, we get quadrilaterals like this Instead will define the elements with the NGEN and EGEN commands to learn more about them.

The left figure above shows a meshed plate with 64 nodes and 98 triangular elements. For the Ansys code that you will start with today, the left and bottom edges are thermally insulated while there is a temperature gradient on the top and right edges. The temperature is 50 F at the upper-left and lower right corners and increases linearly to 400 degrees at the upper-right corner. The Ansys code is found in the file heat2d64.a. Look at the MP command. We have been using MP,EX to define the elastic modulus. Now we use MP,KXX to define the thermal conductivity. Look at the D command we have been using to constrain movement in mechanical systems. For this problem we use it to set the temperature. For example

D, 8,TEMP, 50

sets the temperature of node 8 to 50 degrees. Today you will change the Ansys code to insulate the top, left, and bottom edges and define a temperature gradient on the left edge.

The lesson is in two parts. First you will use a short file Heat2da.a to create just the 2D array in stages by adding keyboard commands. Then you will change to the complete file Heat2d64.a to solve the problem. You did a similar thing in Assignment 4. For both files, you will make changes with editor before running Ansys. Append the output data from the complete second file to the end of the Ansys file. Print the Ansys source file and the two graphics showing the elements and the temperatures.


  1. Copying and editing the two Ansys files.

  2. Running the shorter heat2da.a with Ansys
    In this section you will run the short file with Ansys in batch mode to create the first element. Then you will type two Ansys EGEN commands and an E command to create more elements.

  3. Running the longer Heat2as8.a with Ansys
    In this section you will edit and run Heat2as8.a with Ansys. This will create the all the elements and calculate the temperatures and flux.

  4. Append temperature and heat data

  5. First printout
    Look at the elements again by clicking the Plot menu and picking Elements.
    Capture, edit, and print this figure continuing the elements. If not printing in color, change to grayscale, and negative.

  6. To see the thermal flux, pull down the Plot menu and pick Results, Contour Plot, Nodal Solution, DOF solution, Def shape only, Apply. This shows the temperature fields without the elements.

  7. Second printout
    To see the temperature and the elements together. click the Plot menu and pick Results, Contour Plot, Nodal Solution, DOF solution, Temperature and Def + undeformed, OK
    Capture this figure, edit and print it. If not printing in color, change to negative and grayscale.

  8. Try other combinations such as Results, Contour Plot, Elem Solution, Flux & Gradient, Def + undeformed, Thermal grad TGSUM to see the flux.

  9. Assignment
    Create a cover sheet that includes a discussion of the two types of 2D elements you have used so far. Also discuss batch mode vs. adding keyboard commands. Attach the two graphic screens you captured and turn in the package as specified at the lab.

  10. Before logging out check the size of your saved files.

Epilogue: In this lesson you began Ansys with batch mode to create one element. Then you gave two EGEN commands from the keyboard to create more elements. You altered another batch file to create a temperature gradient in a two-dimensional plate. Ansys then calculated the temperature throughout the plate. In Assignment 9 and 10 you will not use batch mode at all. You will create a two-dimensional plate and apply constraints and a load by using menus. Then Ansys can find the deflections and stresses. This is a very power feature of Ansys, but because there are so many features, it is easy to get lost.

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Files: Ansys, Matlab, Bash

Revised: March 19, 2004 -- Copyright 1997-2004 ARMiller