# Stress and strain help!!! watch

1. Question 13 folks, been at it for a while and I can't get it. To me it seems like something is missing from the question?

Edit: the workings I've done is me trying to work backwards from the answers given
2. (Original post by Dav1dJG)

Question 13 folks, been at it for a while and I can't get it. To me it seems like something is missing from the question?

Edit: the workings I've done is me trying to work backwards from the answers given
Smack
3. (Original post by Dav1dJG)
Smack
I'm on it.
4. Is there some sort of rule of thumb regarding sheet metal that I am missing? It seems quite hard to do this without knowing the pressing force, unless we are to attempt to solve it iteratively.
5. (Original post by Smack)
Is there some sort of rule of thumb regarding sheet metal that I am missing? It seems quite hard to do this without knowing the pressing force, unless we are to attempt to solve it iteratively.
Nope. Apparently everything is there.
I emailed my lecturer for tips last night. All he said was that the shear and compressive stresses both have to be in terms of Force and substituted into the other equations.
Which confused me even more hahaha.
6. (Original post by Dav1dJG)
Nope. Apparently everything is there.
I emailed my lecturer for tips last night. All he said was that the shear and compressive stresses both have to be in terms of Force and substituted into the other equations.
Which confused me even more hahaha.
Does it have to be solved by hand, i.e. manipulating the equations and performing algebra?
7. (Original post by Smack)
Does it have to be solved by hand, i.e. manipulating the equations and performing algebra?
I think that's what is required. As I said though, I've tried working backwards from the answer n still got nowhere.
64mm diameter and 128.7kN respectively
8. (Original post by Dav1dJG)
I think that's what is required. As I said though, I've tried working backwards from the answer n still got nowhere.
64mm diameter and 128.7kN respectively
I just solved it iteratively using Excel and arrived at those answers. Can't help with the algebra though I'm afraid.
9. (Original post by Smack)
I just solved it iteratively using Excel and arrived at those answers. Can't help with the algebra though I'm afraid.

That's cool man cheers for trying. I've got dynamics first thing tomorrow, that lecturer teaches statics aswell though so I'll get his help to solve it, take a photo n post back! I've got this statics exam tomorrow. Hopefully nothing this bad! Frameworks and beam bending moment diagrams are a cakewalk compared to that lol
10. What exam board is it??
11. (Original post by Dav1dJG)
...
I just ran through my (non-iterative) calculations and managed to arrive at 64mm and 128.7kN for the solution.

The essential steps for the maximum diameter are:

1) Work out the shear force at yield by making use of the shear yield stress and the relevant reference area.

2) Equilibrate the shear force with the compressive yield stress of the punch.

For the minimum force, you should again equilibrate the shear force at the point of yielding due to shear, making sure to use the correct relevant reference area.

The steps use only very basic algebra, so it should be quite easy if you follow the above steps.

Good luck!

Edit: Forgot to mention that you should definitely make a plane stress assumption for the steel sheet. That should make life a lot easier!

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