# FEM/FEA Torque Wrench

## Main Question or Discussion Point

Hope this is the right place for this?

I have a torque wrench, and need to calculate several parameters.

I need to calculate

- Stress
- Displacement

and

- Force required to reflect the torque rang (2NM - 30NM)

I have ansys (fea) and mathcad (fem) at my disposal to do these calculations, i am just not 100% sure on where to start?

I have done a free-body diagram, and decided that there should be 3.D.O.F, but not sure if there should only be 2?

BUT

My main problem is, how do i model a torque wrench in Ansys? I have the geomotry all sorted (i think) but i dont know how one should constrain, or even what set-up should be used? I was thinking of static structure?

Help and a push in the right direction would be most helpful, and i would be most greatful.

## Answers and Replies

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There are different kinds of torque wrenches, so one answer doesn't fit all. Let's assume you're doing the inexpensive beam wrench you might buy at Sears for example.
http://www.sears.com/shc/s/p_10153_12605_00944642000P?vName=Tools&cName=MechanicsTools&sName=Torque Wrenches&psid=FROOGLE01&sid=IDx20070921x00003a
You can make a very quick, fairly accurate calculation using simple beam equations by hand. If you want to do a full-blown FEA on this, I'd suggest modelling it in something like Pro-E and running ANSYS. The simplifications you need to make are to fully constrain the drive end (probably 1/2") and apply a simple perpendicular force to the handle somewhere beyond the dial. The critical parameter in your design will be the deflection.

Last edited by a moderator:
Thanks for that, will give it a go.

I am going to use ANSYS, and i think i can model the geometry in workbench so to eliminate pro/e as its a pain.