Learning Forum

[Alessandro Giuliani]

Hi,

I have to verify a frame that consists of long tubulars. In order to reduce the model's size I want to use the advantages of symmetry region.

In the first load step 21 remote masses and Standard Earth Gravity are applied. In the second one I've applied a positive acceleration along "X" direction ( horizontal plane of the structure - see the pictures ). The question is the following : Is this acceleration considered equal and opposite on to the simmetrical part of the model? My doubt is to get acceleration's deletion in the full model.

Thanks in advance

 

 

[peteroznewman]

Hi Alessandro,

An acceleration load in the X direction is not a symmetric load when you split the model in the YZ plane at the center.  You need a full model.  An acceleration in the Y or Z directions is a symmetric load.

To reduce the model size, convert the solid geometry to line bodies with beam properties assigned. This can be done in SpaceClaim or DesignModeler. 

[Alessandro Giuliani]

Hi Peter, Thanks for your answer. Ok, I'll try to convert the solid to line bodies but I have to make you a question before : the frame isn't welded. All bodies are assembled by means of bolt connections. So, can I explain this situation in Workbench with a line bodies model or should I consider the model as fully welded? The purpose of the work is to verify all elements, joints and screws (I hope my English is understandable). Thank you very much

[peteroznewman]

Hi Alessandro,

One approach to reduce the model size is to have a solid model only for a short length around each bolted joint. For the long spans of the beams, use beam elements. Bonded contact allows you to switch from a beam model to a solid model a short distance away from the bolt. But don't make the transition too close to the bolt.

You could build this up in phases, where in the initial phase, you don't model any bolts. Use a Fixed Joint to connect one hole to another hole where the bolt will be. You can extract forces and moments going through the Fixed Joint.  For the few joints that have the highest forces or moments, delete the Fixed Joint and add in a representation of the bolt, add a Bolt Pretension load and some Frictional contact between the parts being clamped. In this way you spend your time and resources (nodes and elements) in areas of high stress while saving your time and resources where the forces and moments are small and so the stress will be low.