Thread Analysis on SolidWorks 1

[marcuscouceiro]

Dear Gentlemen,

A friend of mine asked to perform a few calculations in order to find out if the threads of a Nut and Screw could sustain the amount of traction force applied.

So, I performed the calculation to find out the area of the threads in contact and, using a factor of 2, I have found out the maximum force that the threads could hold.

After that I have tried to use SolidWorks to validade my calculations but, although I can model a lot of things on Solid, I do not have the practice to perform simulations.

Could any of you guys have a look on the calculations and tell me if they are reasonable? If any of you have the proficience with Simulation on SolidWorks, could you share some tips?

Any comments will be very welcomed.

Thank you all for your ideas,

Marcus

 

[marcuscouceiro]

The calculations were missing.

Here they are.

Kind regards,

 

[EngAddict]

I have done a few thread simulations in Solidworks. You are best to model a slice and use symmetry, since the mesh size will need to be quite small.

What you will find is that about 27% of the load is taken by the first thread, not averaged over the full number of engaged threads. There is a method in ASME VIII Div.3 for calculating this load. Some people use a simplified method where they subtract one engaged thread and average the load over the remaining. IMO this can be unconservative in most high loading situations.

Typically find the load in the first thread then check for contact and shear stress. The same code will give you allowable limits if you are using it for pressure equipment. For your case you should refer to a relevant structural code.

I have found that the non-uniform loading is quite accurate for elastic thread loading. If you want to account for local yielding in the threads to redistribute the load then you will need to run a non-linear analysis. You may also get reasonable results in the static analysis by turning on large displacements. Sine the deformation will be small your results should be reasonably accurate. It will make for a good comparison to the elastic analysis.

Basically though I don't know if you need to check the 'threads', don't you really only need the tensile and shear capacity of the bolt? This is easily calculated with the core area for shear and the stress area for tension. For shear in the shank you just need the shank area. At work I would just compare my load to the published capacity for the relevant bolt, takes about two seconds. Checking the threads is only really necessary in special cases, like highly loaded acme threads and the like.