# How to apply Moment along an edge such that its normal to the surface along the edge

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• Last Post 05 August 2018
Devaiah posted this 04 August 2018

I have a cylindrical shell, I need to apply a moment(UDL) along the edge on one of its edges such that it is normal to the surface along the edge of the cylinder.

Requesting for some info on the above--

Thank you.

Attached Files

SandeepMedikonda posted this 04 August 2018

Hi Devaiah,

Right click on your analysis settings and insert a moment as shown:

Change the Define by to Components and enter a value for the moment, which would be 'Z' in your case.

Regards,

Sandeep

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peteroznewman posted this 04 August 2018

Hi Devaiah,

Sandeep says to use components, which is useful, but he describes a moment that would twist the tube along its axis.

Your sketch looks to me like you want to apply a moment to the edge in a way that would turn the tube inside out, or begin to roll it down its length. I don't know of a simple way to do that. It is simple to define a cylindrical coordinate system and apply a radial force to stretch the opening of the tube radially.

An inelegant and imprecise method is to slice the tube up and apply individual moments to the edge segments using components. I made 4 slices to get 8 edge segments and applied a moment to two of them.

I hope someone will reply with a more elegant way to to that.

Regards,

Peter

ANSYS 19.1 archive attached.

Attached Files

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Devaiah posted this 04 August 2018

Hi Mr Sandeep,

Thank you for the answer at the earliest.

But the problem as I mentioned above is that the moment should act normal to the surface at each and every point along the edge.

By using components, it satisfies the normal condition at only one of the points along that edge as shown above.

I'm trying to verify an analytical result using FEA as shown below.

Here as the author mentions, both the shear force and a bending moment is applied along that edge and is normal to each and every point along the edge.

Any info in the above would be great.

Thanks a lot.

Regards,

Devaiah

Devaiah posted this 04 August 2018

Hi Peter,

Firstly thanks a lot for the quick reply.

Wow that's actually very close to how I want the moments to be applied.

Let me slice it up and compare the generated results with the analytical solution and comeback to you.

Thanks and Regards,

Devaiah

peteroznewman posted this 04 August 2018

Hi Devaiah,

I recommend an axisymmetric model in ANSYS. That means a radial slice is modeled, but the full 3D equations and all components,including hoop stress, are computed. I believe you can apply a moment to that edge in an axisymmetric model.

Regards,

Peter

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Devaiah posted this 04 August 2018

Thanks for the additional info as well Peter.

I'll try that out as well and comeback with the results.

Regards,

Devaiah

peteroznewman posted this 04 August 2018

Here is the axisymmetric model. I had to create a surface, but then I could apply a moment to the edge.

If you revolve this result around the axis, that is the 3D solution.

The point the author is making in the book is that these moments (and shear forces that you didn't mention) die out quickly and can be neglected compared with the other terms in the analytical derivation.

Regards,

Peter

ANSYS 19.1 archive attached.

Attached Files

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Devaiah posted this 04 August 2018

Hey Peter,

Thanks a lot.

I'd been stuck with this for more than a week now.

Really grateful to you.

Regards,

Devaiah

Devaiah posted this 05 August 2018

Hi Peter,

I observed the file that you had attached. The element chosen is a plane element.

I had to use a shell element for the above analysis.

Any other means by which I can use a shell181 element as well as conform with the moment along the edge?

Thanks and Regards,

Devaiah

peteroznewman posted this 05 August 2018

Hi Devaiah,

The only way I know is the imprecise method of slicing the tube into segments and applying the different orientations of moment to those individual segments.

The textbook also mentions shear force Q, which is illustrated as a radial force. That can be done with a single Cylindrical coordinate system and a single force applied to the circular edge.

Regards,

Peter

Devaiah posted this 05 August 2018

Thank you Peter.

Let me try that out.

Regards,

Devaiah