Finding Reaction Force on a Body

Newton’s third law of motion says that all forces occur in pairs, so if one object exerts a force on another, the second object will respond with an equal and opposite reaction force. The general statement of Newton’s third law of motion is: “For every action, there is an equal and opposite reaction.” There are different reaction forces in Abaqus, such as Contact Forces, Gravitational Forces, Tension Forces, Air Resistance Forces, Electrical Forces, Magnetic Forces, etc. There are two types of contact forces as a result of action and reaction force between objects that have contact together. One of the contact forces is the Normal force. This force is the force that surfaces exert on each other to prevent them from passing through each other. The frictional force is another reaction force that acts parallel to the surface to prevent sliding against each other. To calculate these contact forces, you should define normal and frictional properties in the interaction module. In a finite element simulation user may need to find the effect of each reaction force in the result.

Generally, we have two choices to find the total “Reaction force” acting on the body or Abaqus reaction force (Abaqus RF):

1. Defining a reference point and using kinematic coupling

The body can be coupled to a point during the model setup stage. After the analysis, the Reaction force can be checked at this node, which gives you the total reaction force.

2. Using XY Data in post-processing

Another method of finding out the Total Reaction Force without going into the model setup stage would be to obtain the reaction forces at all the nodes on the body and then sum up the forces. In this lecture, we discuss the second method, which is simpler and more useful when your analysis has been completed, and you already have results and do not tend to submit a new job.

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Using XY Data in post-processing to find Reaction Force

1. In Visualization module, Click on the “Create XY Data” icon.
2. In the dialogue box which appears, toggle ODB field output:
3. Click on Continue…
4. In the XY Data from ODB Field Output Dialog box, choose
   Position: Unique Nodal
   
   
5. Then, scroll and click on the right-pointing triangle next to RF to open up.
6.  Select the component you are interested in say RF2 (Tick This)
   RF: RF2 will appear in the window below.
7. Click on the TAB: Element/Nodes
8. On the left, click on “Internal Sets”
9. On the right, the node sets automatically created by Abaqus will appear. For any part, Abaqus create a set, which has a name like “PART-1-1._PICKEDSET2”.
10. Select the part (automatically defined node-set) for the reactions you require.
11. Click on SAVE
12. In the Save XY Data dialog box, click on OK.
13. Click on “Create XY DATA” icon (the same one as before)
14. This time TOGGLE “Operate on XY DATA”:
15. Click on CONTINUE…
16. In the new dialog box on the right, will be listed various functions/operations.
    Scroll down and click on Sum((A, A….))
    This will appear in the top window.
17. On the left, all the reaction forces (RF3, say) for each of the nodes in the selected set will be listed…

Highlight all of these rows

(Method 1: by holding down the left mouse button and dragging it over all the lines. Method 2: easily select the first line, hold down the SHIFT key, scroll down to the last line, and click on it).
19. Click on the Add to Expression button
20. Click on the Plot Expression button.
This will plot the sum of the selected component of RFs for all the nodes in the selected node set.

I hope you have got enough information about Abaqus RF in this post, continue reading other posts available on our blog.

It would be useful to see Abaqus Documentation to understand how it would be hard to start an Abaqus simulation without any Abaqus tutorial.

If you want to start learning ABAQUS for the first time, it would be useful to watch the below demo of the “Abaqus for beginners” tutorial package and check the best training resources on the Abaqus tutorial.

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