Surface Creation
Altair EmployeeHi all,
I am fairly new to Hypermesh (Optistruct) and have been practicing the software as part of final year in my degree. I am currently working on analyzing the maximum stress and its location on a UAV Horizontal tail. Now, I created the assembly in CATIA and exported (igs file) the file into Optistruct. Now, in order to analyse the structural integrity of the component, the force applied is essentially the lift acting on the top surface. As you can see, the problem I have is that I do not have a surface on my tail-only the internal structure has been modeled for this analysis, and in reality the skin of the tail is just a thin plastic sheet-hence the material of the skin could be neglected. So, I created the surfaces using spline/filler command and filled the gap between the ribs-for this simulation I have applied the forces on this created surface. However, the problem arises when, my simulation does not run, and it stated that I have not assigned any properties to the surfaces that I have created. Ideally, I would like to use that use that surface only to apply the forces onto and not create an actual skin-hence, distributing the load along the entire tail (ribs and main spar). Is there a way to carry this out, at the moment, the results I am achieving do not make much sense- as no stress is occurring on the internal structure itself.
One of the reason why I believe the stress does not have act on the internal structure could be due to the interaction between the mesh on the surface and the internal structure itself. I did notice that, when I created the surfaces using spline filler, it would not accurately follow the desired geometry-hence leaving a slight gap. Could this be a root cause for no stress on the internal structure?
Let me know what you guys think, any assistance and guidance will be appreciated. I have also attached a word document with some images of what I am trying to explain, hope they help.
Thanks and Regards,
Ramon
Answers
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Hi,
As mentioned above that you want to apply force on newly created surface to transfer load. So assign appropriate thickness to that shell element & make sure that all elements should be connected properly.If possible share out file of the run or input .fem deck.
Regards
Rahul R
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Hi Rahul,
Thanks for the response. That is exactly what I previously did. I assigned the thickness and material for the 'skin'. The trouble I am having is that, the surface (acting as skin) in between the ribs is used for applying the forces or pressure acting on the tail during flight (rather than an actual skin). However, when I ran the analysis, the aerodynamic load was not being transferred from the skin to the internal structure (ideally most of the stress should be on the main wing spar). I believe, this maybe due to my meshing, I have meshed the internal structure and the top surface using 2D automesh.
Having said that, 2 problem arise from this, first being, how do I make a surface that I have created into a solid? This will then allow me to mesh the internal structure and the skin using 3D tetramesh. I believe, this may solve my problem and I will be able to obtain some sensible results. The 2nd problem is that, if I mesh the surface via 2D and the internal structure as 3D (which seems most sensible to me due the geometry of my component), how do I connect the 2 different types of meshes together so I can get results where the stress occurs on the internal structure?
Overall, I think I am stuck on 2 main areas:
1. Making a surface to solid (to mesh the skin as 3D)
2. Combine the 2D and 3D mesh into 1 for load transfer. (this is applicable if I leave the skin as 2D mesh).
Apologizes if the above comments seem long, but, it's my first time using Hypermesh, hence I'm running into problems that I need help solving.
Let me know if you want me to attach any files which may help to explain myself a little better.
P.S. I found a tutorial that connects 2 different meshes together, however, I did not understand exactly what was being done. Can you suggest me a better approach? The tutorial I used is within Optistruct 13.0 tutorials: OS-1050: Connection of Dissimilar meshes using CWELD Elements.
Thanks and Regards,
Ramon
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