File .Iges/Igs versus .Step

marco

Hello,
I don't understand the difference between the .Iges/.Igs file and .step file in Mecway.
Using .Iges file I can't generate a solid mesh without create before a shell mesh.
Using .step file Mecway creates automatically a solid mesh (I tried with the "Cadworkflow" tutorial).
I create .iges/.igs file with Autocad but I can't create .step file. If Mecway can't create directly a solid mesh with .Iges file, is there a method to convert .iges file to .step file?

Thanks for tips,
Regards
Marco

Andrea

IGES is a surface format and contains no solid information. In some FEA is possible to build volume from igs closed surfaces. I think that is a feature of the software that Mecway hasn't.

On Salome platform sometimes there are issue importing igs because to build volume is necessary to change the tolerance on importing igs

marco

Thanks Andrea for the answer.
I am trying to model and calculate in Mecway structural steel joint creating solid elements (with Autocad). Have you any advice of a software to create .step file?
Maybe drawing parametric objects for plates and bolts.

Thanks,
Marco

Sergio

You can try any 3D cad as Freecad, Salome (yes, simple geometry can be generated there), Onshape, Fusion 360, Solidworks, Solidege, NX, CATIA...all will generate a STEP file.

Regards

Andrea

If you want to model joints on FEA environment you have to build different bodies. Is better to use step file.
I don't use autocad for this pourpose but I think that isn't the best solution.
As Sergio wrote there are many CAD software. If you are student you can open an Autodesk account and you can use, without resctrictions, Inventor (or Fusion)

Regards

Sergio

I have seen Tekla for creating those structures and joints, it has some kind of library for them.

DaveStupple

Also, Solid Edge offer an (I think) fully functional version for students, that you are not supposed to use for commercial work.

marco

Thanks for your answer.
I am a structural engineer (civil) and I am trying to calculate structural nodes with FEA software to manage not-standard nodes (generally indications for standard nodes are in National Codes).
Software like Tekla are "closed software". There isn't the possibility to model nodes with complex geometry. Moreover are expensive softwares.
I will try with Freecad. I have seen the on-line documentation and the software can create parametric objects.
I would create a parametric node, export the geometry in FEA software and calculate it.
If some part of the node (plate thickness, bolts, welds) aren't verified, I can change easily the geometry and recalcute it.
At the moment my problem is to create the geometry, after this I think that I have to consider the constraints between objects and loads application (generally derived from a 3D beam model).

Regards,
Marco

Andrea

About steel structures and to design or to investigate bolted joints I don't model the screw and nut but I consider the screw as a beam. To link the beam to the plate is possible to use rigid body elements and to simulate pre-tension is possible to apply variation of temperature to the beam element (screw).
After that is possible to verify the bolt with the code (for example Eurocode 3 part 8).
If you are going to simulate with complete bolt as a body, obviously, don't consider the thred

Regards

Sergio

Look for the CalculiX 09 channel in Youtube, he has made some video of this kind of unions using bolts. With CCX you can use also the PRELOAD card to apply directly the bolt preloading.

By the way Andrea, how do you apply the temperature preload to a bolt? I have made some kind of analysis using that aproach in the past (with a solid bolt), but applying enough preload/temperature to reach 75% of bolt´s yield stress (after several tries), but there is some more technical procedure to reach a defined bolt preload?

Regards

Andrea

This proredure is the oldest, I think. Is based only over thermal expansion linear equation. No trial and error method is necessary with beam elements but only calcolous of DeltaT

Sergio

Yeah, were ten years ago or more. I use solid element as I neeed to compute the slippage and separation under the bolt head at ultimate loading of aluminium brackets. We divide the shaft of the bolt, normally the non threaded portion and apply only thermal properties to that volumen, and make two or three runs to determine the delta temperature to reach the desired stress on the bolt. Now is easier with the PRELOAD feature available in Abaqus, CalculiX and other codes.