How to create a thin shell membrane from the surface of solid elements?

Dominic_21343

REF:  I'm using HyperMesh Desktop 2019.1

I've read through several posts, but unfortunately cannot find an answer. I checked youtube, but also no luck. Sorry, but I have no idea how to create this membrane, and didn't get more details after my follow-up to an earlier question.

Target:  Our customer requires that we use a thin shell membrane on the surface of our solid element models. My understanding is that a solid element will average the stress results, so you won't know the true peak stress of the surface. So, this thin shell membrane (0.01 thick) is supposed to confirm more accurately what is the actual peak stress on the surface of the part.

Past attempt:  I tried another method of using a control card on the solid elements = GLOBAL_OUTPUT_REQUEST, selecting STRESS, and Location = GAUSS, but GAUSS shows same stresses as the normal method I did before. There is a difference between ADVANCED AVERAGING & MAXIMUM in HyperView (maximum being higher, obviously), but normal & GAUSS shows the same stress for each option.

Please help me to know how to create this thin shell membrane properly from the surface of solid elements that I created. My goal is to see if the membrane method gives a different stress result or not. Here is a pic of the solid elements model that I am working with.

Thank you very much for any help you can provide.

Michele Macchioni

Dominic,

suggest you to use the faces option from tools

you will be prompted to select components or elements, thus select your solids.

HM will create an ^faces component: please rename it for instance as "membrane" (the ^ symbol triggers HM to not export that collector).

You are basically there as you can then create a very thin PSHELL in OptiStruct and assign it to these faces (keep proper material consistency if you have different ones).

you could as well blank the out of plane bending stiffness of the pshell like below

to get pure membrane effect.

I believe though this is not a big effect as long as your shell layer thickness is very small.

Hope this helps.

Thanks

Michele

Michele Macchioni

Dominic,

suggest you to use the faces option from tools

you will be prompted to select components or elements, thus select your solids.

HM will create an ^faces component: please rename it for instance as "membrane" (the ^ symbol triggers HM to not export that collector).

You are basically there as you can then create a very thin PSHELL in OptiStruct and assign it to these faces (keep proper material consistency if you have different ones).

you could as well blank the out of plane bending stiffness of the pshell like below

to get pure membrane effect.

I believe though this is not a big effect as long as your shell layer thickness is very small.

Hope this helps.

Thanks

Michele

Dominic_21343

Michele Macchioni said:

Dominic,

suggest you to use the faces option from tools

you will be prompted to select components or elements, thus select your solids.

HM will create an ^faces component: please rename it for instance as "membrane" (the ^ symbol triggers HM to not export that collector).

You are basically there as you can then create a very thin PSHELL in OptiStruct and assign it to these faces (keep proper material consistency if you have different ones).

you could as well blank the out of plane bending stiffness of the pshell like below

to get pure membrane effect.

I believe though this is not a big effect as long as your shell layer thickness is very small.

Hope this helps.

Thanks

Michele

Hello Michele,

Thanks for your quick response. I was just watching a youtube video similar about this Tools --> Faces function, but that video seemed to be making a new solid part from the solid elements. So, thank you for tips how to make it as shell membrane elements on the solid elements surface.

I was having troubles get the details how to make the membrane on another post, but do I understand that I should also add a control card about PARAM, SHL2MEM, 0.01 (where 0.01 is the thickness of the membrane that I just made)?

Thank you for any help to clarify this control card option?

- Dominic

Michele Macchioni

Dominic_21343 said:

Hello Michele,

Thanks for your quick response. I was just watching a youtube video similar about this Tools --> Faces function, but that video seemed to be making a new solid part from the solid elements. So, thank you for tips how to make it as shell membrane elements on the solid elements surface.

I was having troubles get the details how to make the membrane on another post, but do I understand that I should also add a control card about PARAM, SHL2MEM, 0.01 (where 0.01 is the thickness of the membrane that I just made)?

Thank you for any help to clarify this control card option?

- Dominic

Dominic, 

I believe that you can skip the use of the 

if you are implicitly setting the MID option to zero.

I don't have any result at hand but can tell you from my experience in the simulation field that if you already use very small value for T you get already what you want without investing much time on deck rework.

My suggestion is:

- Run a simulation with PSHELL and small T

- Run another simulation with PSHELL and PARAM,SHL2MEM 

and verify the delta among the results. I am not expecting big or let's say significative difference on what you are really looking for.

Thanks

Michele

Dominic_21343

Michele Macchioni said:

Dominic, 

I believe that you can skip the use of the 

if you are implicitly setting the MID option to zero.

I don't have any result at hand but can tell you from my experience in the simulation field that if you already use very small value for T you get already what you want without investing much time on deck rework.

My suggestion is:

- Run a simulation with PSHELL and small T

- Run another simulation with PSHELL and PARAM,SHL2MEM 

and verify the delta among the results. I am not expecting big or let's say significative difference on what you are really looking for.

Thanks

Michele

Thank you very much! Have a good day!