Possible unit conversion mistake

General Questions
1

hi, I’ve found possible bug in units. 2.3.0
when calculating fixed end cantilever bending the reaction force was 100 times bigger than the FEA results. calculation results is 13.26 N FEA 0.1436 N.
beam length 6.3mm , 1.3mm, 5.5 mm. E=2100 MPa

2

It sounds more like a user mistake than a bug in units. How are you applying the load ? Can you share the model ?

Remember about this: Don't apply concentrated force load to surfaces

3

snap bend.pmx (1.4 MB)

4

The total reaction force in the simulation is:

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Using simplified hand calcs (not accounting for the variable cross-section), I get 5.16 N.

5

I’m trying to calculate the force for bending the snap at this point the value is 0.14 N while the hand calculation is about 14 N

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image788×649 116 KB

6

Don’t use the FORC field output for that. Instead, request history output of RF for the nodes where you want to measure the reaction force. It can be a reference point of the rigid body constraint or all nodes on the fixed face (then just set Totals to Only so that it gives you only the sum):

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7

understood.
I also can define it from the reference point 1 to get the same result.

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image1512×658 125 KB

8

So, is the reaction force correct?

9

yes, now the results makes sense. i also refined the mesh size and reached similar max stress,

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image975×694 129 KB

10

Since it is not a bug, I am moving this topic to General Questions.

1 Like