Lesson 4:
Thermal-Structural Analysis
Next a composite slab thermal-structural model is illustrated. This time we will also solve for the stressed in the materials resulting from differential expansion of two materials.
ANSYS Commands for the Composite Slab Thermal Stress Problem
Get a solution for the temperature field as explained in the previous handout. Chose ``PLANE55'' as your element for the temperature calculations. Make sure you enter all properties namely KXX, EXX, NUXY, and ALPX when you define material properties. Remember in the previous handout you defined only KXX. For this problem you require not only the thermal, but also the structural properties for the two materials. EXX is the Youngs Modulus, NUXY is the poisson's ratio, and ALPX is the coefficient of thermal expansion.
Postprocessing
This is where you get all the nice colored plots !!!
General Postproc \click (top of screen)
Plot results \click
Nodal plot \click (in the contour plot area)
OK \click
This should give you the temperature field with 500C on the top of the strip and 20C on the bottom of the strip.
Finish \click
DO NOT EXIT HERE. NOW WE NEED TO DO THE STRESS SOLUTION.
To get the stress solution you must return to PREP7 because we now need to select an element which can handle stresses. Remember ``PLANE55'' is a thermal element.
Preproc \click
ElemType \click
Switch Elem Type \click
This changes the element type from ``PLANE55'' to ``PLANE42''. You see ANSYS is pretty slick. It knows the correct type of 4 noded stress element which is required. Of course if you did not want to use what the program suggests you should go and chose an element as demonstrated in the earlier handout.
Finish \click
Solution \click \click
Now we need to constrain the left edge of our model since that is embedded in a wall and cannot move. This is done by applying zero displacements to the nodes on the left edge.
Select \click (blue menu top)
Entities \click
Nodes \click
OK \click
Box \click (green box at left)
Pick the left edge of rectangular box to mark the nodes on the left edge.
Apply \click (green box on left in the Loads section)
Displacement \click
On Nodes \click
All Dof \click
OK \click
Select \click
Everything \click
Now we need to input the temperatures calculated earlier because the differential thermal expansion is going to create the stress. Temperature \click (green box on left)
From Therm Analy \click
compslab.rth \click (files box)
OK \click
We also need to set the reference temperature for the thermal expansion calculations
Loads \click (green box on left)
Settings \click
Reference Temp \click
Enter reference temperature (say 20C) OK \click
Now solve the problem as in the previous cases.
Finish \click (green box on left)
This finishes the solution phase of the problem
Postprocessing
This is where you get all the nice colored plots !!!
General Postproc \click (top of screen)
Plot results \click
Deformed Shape \click (in the contour plot area)
Def + undeformed \click
OK \click
This will show the deformed composite strip and compare it to the undeformed shape.
Using the nodal plot method for temperature contours discussed earlier you can also get plots of various stress components.
Finish \click
File \click (blue menu top)
Exit \click
Save Everything \click
OK \click
THIS CONCLUDES THE COMPOSITE SLAB PROBLEM
Thermal-Structural Analysis
Next a composite slab thermal-structural model is illustrated. This time we will also solve for the stressed in the materials resulting from differential expansion of two materials.
ANSYS Commands for the Composite Slab Thermal Stress Problem
Get a solution for the temperature field as explained in the previous handout. Chose ``PLANE55'' as your element for the temperature calculations. Make sure you enter all properties namely KXX, EXX, NUXY, and ALPX when you define material properties. Remember in the previous handout you defined only KXX. For this problem you require not only the thermal, but also the structural properties for the two materials. EXX is the Youngs Modulus, NUXY is the poisson's ratio, and ALPX is the coefficient of thermal expansion.
Postprocessing
This is where you get all the nice colored plots !!!
General Postproc \click (top of screen)
Plot results \click
Nodal plot \click (in the contour plot area)
OK \click
This should give you the temperature field with 500C on the top of the strip and 20C on the bottom of the strip.
Finish \click
DO NOT EXIT HERE. NOW WE NEED TO DO THE STRESS SOLUTION.
To get the stress solution you must return to PREP7 because we now need to select an element which can handle stresses. Remember ``PLANE55'' is a thermal element.
Preproc \click
ElemType \click
Switch Elem Type \click
This changes the element type from ``PLANE55'' to ``PLANE42''. You see ANSYS is pretty slick. It knows the correct type of 4 noded stress element which is required. Of course if you did not want to use what the program suggests you should go and chose an element as demonstrated in the earlier handout.
Finish \click
Solution \click \click
Now we need to constrain the left edge of our model since that is embedded in a wall and cannot move. This is done by applying zero displacements to the nodes on the left edge.
Select \click (blue menu top)
Entities \click
Nodes \click
OK \click
Box \click (green box at left)
Pick the left edge of rectangular box to mark the nodes on the left edge.
Apply \click (green box on left in the Loads section)
Displacement \click
On Nodes \click
All Dof \click
OK \click
Select \click
Everything \click
Now we need to input the temperatures calculated earlier because the differential thermal expansion is going to create the stress. Temperature \click (green box on left)
From Therm Analy \click
compslab.rth \click (files box)
OK \click
We also need to set the reference temperature for the thermal expansion calculations
Loads \click (green box on left)
Settings \click
Reference Temp \click
Enter reference temperature (say 20C) OK \click
Now solve the problem as in the previous cases.
Finish \click (green box on left)
This finishes the solution phase of the problem
Postprocessing
This is where you get all the nice colored plots !!!
General Postproc \click (top of screen)
Plot results \click
Deformed Shape \click (in the contour plot area)
Def + undeformed \click
OK \click
This will show the deformed composite strip and compare it to the undeformed shape.
Using the nodal plot method for temperature contours discussed earlier you can also get plots of various stress components.
Finish \click
File \click (blue menu top)
Exit \click
Save Everything \click
OK \click
THIS CONCLUDES THE COMPOSITE SLAB PROBLEM
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