Static linear analysis - Calculate the angle of the tooth - Rotation result

[kostaspolakis]

I want to calculate the angle of the tooth that received the force. For that reason, added one beam to have the rotation result. My analysis has degrees for angle. As you can see the results are so small and unrealistic. Are there different ways to receive angle of the part?

[John_Holtz]

Hi @kostaspolakis . Welcome to the Inventor Nastran forum.

1. Why do you think the angle is too small? If you did a calculation, what displacement and rotation did you calculate?
2. Why do you think the angle is in degrees? There is no unit shown; my guess is rotation is in radians.

If you are still having problems, you should provide your model and calculation so that someone can review them. See What files to provide when the model is needed - Autodesk Community.

John

[kostaspolakis]

Even if its  radian, its not match with the reality. I just checked the analysis units and has degrees. I am not sure what angle type does appear.

[kostaspolakis]

I searched so much and i didnt take answers. What angle type does rotation reveal? How can i change that? How can i take the correct results?

[John_Holtz]

Hi @kostaspolakis 

This test model indicates the rotation results are in radians. Only the input is degrees.

Your gear tooth is rotating 0.01601 radians = 0.92 degrees. The question is back to you: why do you think a load on a tooth of a gear on a shaft should deflect much more than 1 degree? (I am guessing the constraint on the cut face is a symmetry constraint which would make the tooth and load symmetric about that face, and the constraint on the inside hole of the gear is a fully fixed constraint which would make the shaft rigid.)

• Where is your model?
• Where are the calculations or test data indicating the real gear tooth should deflect much more than 1 degree when held stationary on a rigid shaft?

I do not have the experience, but I would think a 1 degree rotation of a tooth would result in a large strain which would lead to fatigue in a short time (assuming the gear is rotating at a speed of many RPM like some gears do).

John

[kostaspolakis]

First of all, i want to measure the bending angle of the tooth. I made the main part of the part fixed (from the sides to the bottom). I searched and collected bending limit strain of the bottom of the tooth for my specific gear. At the von mises stress section of results, i manually scanned the bottom area of the tooth with the probes option. As i said before, the task is: Find the angle φ. I tried this beam trick because i didnt know other way to measure angle and the rotation result could not appear without this as an extra. I saw 1 degree and understood that something goes wrong because with my eyes can see that this angle is way more. I measured with an another program and it was 21 degrees. The problem is that i want official results because it will take part in my thesis. 

[John_Holtz · Accepted solution]

Set "Results > Options > Deformed Options > Deformation Scale > Actual" to a value of 1.

You are doing a linear analysis which is based on small displacement theory, meaning the calculated displacement is expected to be small. In most designs, the small displacement is so small that you would never see it unless you exaggerate the displacements. By default, Inventor Nastran magnifies the deformation by some factor so that the shape can be seen visually. This is what you are showing in your image "aaaaa.png" - a highly magnified view of 1 degree displacement. In general, you have to go by the numbers, not by the visual appearance.

I am confused. You originally said the result of 1 degree (0.016 radians) was too small.

• Were you saying 1 degree was too small because the deformed shape made it look like 21 degrees?
• Do you agree that the answer of 1 degree is the correct answer based on the input in the analysis?

John

[kostaspolakis]

Mmm i was thinking 1 degree is a small deformation from the shape of the part. I didnt know about this magnification view. I must search more about this angle deformation. I really appreciate your help. Thank you very much.