Difference Between FEA Result and Hand Calculation in Beam Bending?

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Discussion Overview

The discussion revolves around the discrepancies between hand calculations and Finite Element Analysis (FEA) results for beam bending, specifically focusing on deflection values obtained from both methods.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant presents hand calculation results showing a maximum deflection of -2.39mm, while Ansys reports an average deflection of 0.3mm and a maximum deflection of 0.8mm.
  • Another participant points out the need for clarification on axis orientation and the readability of the hand calculations before further assistance can be provided.
  • A participant acknowledges finding an error in their calculations but does not specify the nature of the error initially.
  • In a later response, the same participant reveals that they ignored a negative sign in their analytical calculation, which led to conflicting deflection values.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the initial discrepancies, but there is agreement on the identification of an error in the hand calculations. The discussion remains partially unresolved regarding the implications of the axis orientation and the overall accuracy of the calculations.

Contextual Notes

Limitations include the lack of clarity on axis orientation and the initial unreadability of the hand calculations, which may affect the evaluation of the results.

Kajan thana
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TL;DR
Hi Guys,
I am doing some lab work on bending cantilever beam and its deflections in both directions y and z directions. For the deflection on the Z-axis, the ANSYS value is positive and the analytical value is negative. I don't know whether I am doing the calculation wrong or is there a specific reason why the direction differs? I have also made sure that the orientation of the axis is the same for both works.
1617313395321.png
This is the analytical working out. I substituted the value of 306mm ( the maximum length of the beam) to find the maximum deflection along the Z-axis. Which came out to be -2.39mm. But according to Ansys the average deflection is 0.3mm and the maximum deflection is 0.8mm.

1617313468207.png
This is the Ansys Values.
 
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There are at least two problems with your question.
1) You have not told us how the axes are oriented (there is no universal orientation),
2) Your hand calc is too small to be read.
Please fix these for us, and then maybe there will be help.
 
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I managed to find the error. Thank you.
 
Kajan thana said:
I managed to find the error. Thank you.
Can you share please?
 
berkeman said:
Can you share please?
I ignored a negative sign in my analytical calculation, this is why I had two values in the opposite direction.
 
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