Reading the Result Contour Plots -- What do the colors mean?

Well, You have your results, Now what do they tell you?  One of the most important areas on an FEA contour plot is the upper left corner.  This will tell you what it is that you are looking at and what the contour scale is set to.  Not all red in a plot is bad.  And just because it is not showing as red does not mean that things are good either.  It all depends on the settings of the contours scale.  This is auser adjustable scale and can be set to any range to show what you want to see.  I typically set the scale so things in red are above a certain limit like the yield point of the material or any other value that I am watching for.  The following is a example on how this scale can be changed.

The piece used in the example below is designed using A36 Steel with a yield strength of 36,300psi.  The part measures 2”X1”X10” and the radii are 1”.  The bar is fixed at one end and a load of 25,000 lbs is applied to the other end.

Image 07

The above image shows the location and magnitude of any boundary conditions and applied loads.  Like with any other image from ANSYS, the information about what the image is showing is in the upper left corner.  The fixed support does not allow any movement in any direction.  The force acts in a normal direction from the plane of the face.  This direction stays constant during the analysis even if the face it is applied to distorts.

Image 0102

The above plot shows the von-Mises stress plot of the results.  The contour scale is at its default setting which will take the maximum and the minimum stresses and evenly divide the stress contours based on the number of colors that you want to use.  In this case, nine colors are used.  Blue usually represent the lowest stress and Red the highest.  But, this scale can be adjusted to show more of what we want to see.

We know the bar is made from A36 steel with a nominal yield strength of 36,300 psi.  What if we want to see what areas in this analysis have exceeded the yield strength of the material.  With the above contour scale it would be hard to do.  But, if the value at the red transition point is changed to 36,300 psi, anything showing red would then be known to be above the yield point of the material.

Image 02

In the above image the transition value between the red and the orange contour has been set to the yield stress of the steel at 36,300 psi.  The portion of the scale below this point gets readjusted to evenly distribute the rest of the contour bands over the stress range below 36,300 psi.  With this adjustment, you can clearly see the areas that have yielded.  You can do this for any range that you are interested in. 

Image 03

The  image above show stress level above the yield point only. Anything in in gray is below yield.  The colors can also be changed in the contour scale as was in this plot.  So always read this information before you try to interoperate what you are seeing.

Image 04

This image is not a stress plot.  If you look in the upper left corner is tells you that this is a plot of Plastic Strain.  This shows the von-Mises or equivalent  strain in the sections of the bar that have exceeded yield. 

So, reading the results is fairly straight forward as long as you know what you are looking at.  This information is always located somewhere in the image and is usually in the upper left corner.

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