Alright I am driving myself crazy. Trying to ensure I am not going to break either wrench tooth off.
I have constrained it but I don't necessarily know if I believe solidworks (potentially due to a constraint error?) I figured the teeth would show signs of displacement at least a small amount?
I have attached my files
I think the probe helped clear it up. hard to distinguish in that blue color. All I knew is the displacement was between 5.674e-02 and 3.937e-32... sort of a large gap. looks like teeth are around 2.479e-04 to 6.757e-06. Thanks
I don't think I can accept that the end of the handle displaces 5/16" though
If stress is below yield, its usable.
Or design it to break before over torquing the nut.
Looks to me like you have contact sets set to "Bonded". If you have that setting the wrench opening will act as if it's welded to the nut and you would not expect to see much stress or movement at the, I assume, fixed bolt.
FWIW I did not look at the files this is just what popped into my head.
correct on them being bonded. I will delete that and see if I can put different constraints on it somehow. keeps giving a large displacement error when not bonded
Try bond one side only.
Make sure that the components settings are something like no penetration. I'm no expert on simulation but I thought I read something about making a small gap between parts. In other words if you start the simulation with surfaces already touching it may not work correctly for no penetration. I'm nearly certain that is the case for certain simulations, motion analysis but completely uncertain if it's the one you're using...like I said, no simulation expert.
It may also be the fact that you ARE getting large displacement. If that is the case, less force, change material or go to the large displacement, spring mode or whatever it's called....see no expert :-)
I was not able to download yours so did a quick one of my own. Complete nonsense but more as to what I would expect to see. Your high stress points are going to be at the contact points where the wrench and nut hit. the handle is the last of your worries. Compared to real world, how many heads of nuts have you rounded off versus broken handles...for me its a gagillion rounded nuts and I can't think of a single open ended box wrench that I've broken.
EDIT: I forgot to mention what I did here. I left a small gap between the two parts. fixed the nut. Created a hinge point for the wrench and supported one side of the wrench with a rolling fixture. Added the force on the handle and this is what I got.
interesting way to fix the assembly. I will try that and see what I come up with tomorrow.
At first I did have a small gap in between the two but I didn't fix it correctly, or at least not like that.
I'm sure there are better ways to fix it but I think doing it that way would give you what you're looking for unless you actually are trying to find out if/how it will slip off the nut.
1-9RU0CPS wrote:
Trying to ensure I am not going to break either wrench tooth off.
Linear static stress does not indicate when a part will fracture - only if it has gone from elastic deformation into plastic deformation.
The Nut is not needed to analyze the Wrench.
The Nut is not needed to analyze the Wrench.
This is absolutely true. The only caveat to this is that if you don't use the nut you end up somewhat assuming how the two parts will interact. Most of the time this interaction is obvious, some times not so much.
Strictly speaking the presence of the nut depends on what you what to know. For certain things it is absolutely essential to included the nut. For others not so much.
To clarify, and I should have stated it like this is in the beginning.
This wrench will be made from aluminum for its purpose so my worry is the "teeth" breaking or the handle bending. I just cant seem to constrain the darn thing to simulate it being used on a nut. Like you posted in your screen shot you have those stress concentrations at two points not necessarily the whole flat surface. That's why im trying to use an assembly with the wrench and nut. Of the simulations I have done and failed doing its showing the end of the handle displacing almost 1" and I just don't believe that to be true. I do know that it is my error more than likely though.
FYI it will be used on an M48 nut which is 75mm across and the wrench is 1" thick by 42" long.
Like you posted in your screen shot you have those stress concentrations at two points not necessarily the whole flat surface.
You're not going to have stress on the whole flat surface, it will be much more like what is shown. If you could have the stress across the whole flat surface then the corners of the nut would never round off.
Of the simulations I have done and failed doing its showing the end of the handle displacing almost 1" and I just don't believe that to be true.
As I stated earlier the likely hood of the handle breaking is next to zero. In my simulation the entire handle was blue with no signs of stress. This would be pretty real world I would think. You have a lever 42" long that you're pushing on the flat of a nut that is what, 1"-1.5" long? That's and 28-42:1 leverage. For every lb of force you put on the handle you would have 28lbs-42lbs of force at the point of contact with the nut. This is why you can tighten a nut or bolt and also why the nuts round off and the handles typically don't break.
If you welded the nut side of the wrench to a plate, sure you could bend or break the handle. But that force is going to WAY higher then the force it will take to round the nut or even break the box end of the wrench assuming you don't have a completely tiny spindle handle.
correct, I am agreeing with you. i know that the nut only contacts in two smaller spots and that the likelihood of the handle breaking is next to zero.
I just want solidworks to show it correctly and i have not been able to constrain it like you managed too.
Here are the files I used. As I said, not sure if this gives anything close to an accurate simulation but it at least looks like what I would expect.
Thanks Matt, that cleared up the constraint issue.
I will just rock on for now and mess with it more later. Still not quite understanding how/why solidworks says that the end of the wrench is deflecting 3/4" but that's a different problem for another day. The only thing that changes this value is changing the reference geometry rad value.
What about FOS, professor?
What about it?
FOS is really a misnomer in my opinion.
Only a measure of transition from elastic deformation into plastic deformation.
The wrench might permanently deform quite a bit (FOS <1) before it fractures.
It is not a measure of fracture in linear static stress analysis (unless the material is very brittle).
As I mentioned, I would not think the way I did it is exactly "Real world". As I said not an expert and I'm not even 100% what the radian offset constraint does. I just knew I wanted the wrench to go around the nut :-)
In real life transition from elastic to plastic deformation happens instantly.
If FOS < 1 the plastic deformation already occurs and the structure is no longer safe.
The standard procedure to calculate the structure capability in engineering is to calculate the distribution of FOS. The min. FOS must be greater than 1.2 to 3 (margin of safety MoS depends of particular industry.)
Do you have a better criterion to calculate the actual structural capacity?
I haven't opened any of the files, so maybe I'm off base here, but think about the motion ratio. If the box end of the wrench needs to move .01" to come into contact with the nut that could easily be 10:1 or more at the end of the handle. The 3/4" of movement may only represent a small bit of deflection.
You could run the simulation in 1 in-oz of torque, and see how much movement you get as a reference.
Not sure "precisely" the behavior you are looking to see, but I'm imagining something like this would be suitable?
Some changes I've made to your study:
Global No Penetration Contact with 0.1 friction
Soft Springs to Stabilize model
Intel Direct Sparse solver
Small Displacement (click "no" to solver message that pops up during after its solved)
Nut can deform but I've fixed one of its faces
Exaggeration scale=5
Use probe to see how much the "teeth" moved.
Increase scale to see how it deform.