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malcolm
& Clementine the Cat
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Stress = force / area. ("/" is divided by)
Is that what you were looking for? There are lots of other formulae that work out the load when a steel section of a certain shape will snap (max tensile stress) or bend permamently (yield stress) or to work out how far it will deform under load. Let us know what you are trying to work out.
Is that what you were looking for? There are lots of other formulae that work out the load when a steel section of a certain shape will snap (max tensile stress) or bend permamently (yield stress) or to work out how far it will deform under load. Let us know what you are trying to work out.
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Someone here, (Storm monkey?) has some fancy sortware for doing that, looks complicated.
I prefer to use the 'put in the biggest piece that can possibly fit' method
Give us an idea of what you need to work out, then with a mixture of maths and experience, we should be able to solve your problem
I prefer to use the 'put in the biggest piece that can possibly fit' method
Give us an idea of what you need to work out, then with a mixture of maths and experience, we should be able to solve your problem
I prefer to use the 'put in the biggest piece that can possibly fit' method
Haha! I agree, that is by far the best method. Nothing wrong with a good bit of over-engineering!
As Malcolm says, there is no simple formula for stress. Apart from there being several types of stress (bending, shear) you must also consider how the thing you're considering is loaded, what cross-section it has, how it is supported etc etc.
There are pieces of software but the ones I'm thinking of (finite element analysis!) are pretty damn complex.
Best to follow Hitch's plan and make a guess-timate. Unfortunately there's no substitute for experience on that front.
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Haha! I agree, that is by far the best method. Nothing wrong with a good bit of over-engineering!
As Malcolm says, there is no simple formula for stress. Apart from there being several types of stress (bending, shear) you must also consider how the thing you're considering is loaded, what cross-section it has, how it is supported etc etc.
There are pieces of software but the ones I'm thinking of (finite element analysis!) are pretty damn complex.
Best to follow Hitch's plan and make a guess-timate. Unfortunately there's no substitute for experience on that front.
The TWI have some software that works out the timescale of faluire on welded fitments, the price?? around 40K
Paul.
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Evening all, been looking in for a while, thought I'd join in.
Superbeam is the one that I use, you can pay for a full working version, or for occasional use you can use the evaluation version which has printing disabled and just manually copy the calculation result from it. I always get my structures double checked by a chartered engineer, they will have professional indemnity insurance if things go wrong.
Superbeam is the one that I use, you can pay for a full working version, or for occasional use you can use the evaluation version which has printing disabled and just manually copy the calculation result from it. I always get my structures double checked by a chartered engineer, they will have professional indemnity insurance if things go wrong.
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Tractor Dave
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Hi!! just thought i'd add this site: http://www.efunda.com/formulae/solid_mechanics/mat_mechanics/calc_principal_stress.cfm
it does simple calculations and gives the maths behind it (not sure of the accuracy)! Just done an exam in it, pitty i can't remember anything!! lol If that doesn't work then the von misses stress is a pritty good one to use!
it does simple calculations and gives the maths behind it (not sure of the accuracy)! Just done an exam in it, pitty i can't remember anything!! lol If that doesn't work then the von misses stress is a pritty good one to use!
Tractor Dave
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well the above site should help if your working out the stress in all direction, although the units will probably have to be changed!
But if you just want to know the max shear stress of the bolt then:
Max shear stress = Torque (Nm)/Polar second moment of area X radius
Radius = 0.01m, Polar second moment of area = (pi) X dia (m)to the power of 4 all divided by 32. So as long as you know the torque thats being applied, its easy to work out! The units for Max shear stress are N/m squared.
Hope that helps........ I can't believe i actually remembered that!! lol
But if you just want to know the max shear stress of the bolt then:
Max shear stress = Torque (Nm)/Polar second moment of area X radius
Radius = 0.01m, Polar second moment of area = (pi) X dia (m)to the power of 4 all divided by 32. So as long as you know the torque thats being applied, its easy to work out! The units for Max shear stress are N/m squared.
Hope that helps........ I can't believe i actually remembered that!! lol
Haha! I think my talk of FEA might have been a bit OTT!
As Si says, the answer is really in the bolt grade. Common bolt grades are 8.8 and 12.9. You must multiply the first number by 10^8 to find the ultimate tensile stress. The second number is the yield stress expressed as a percentage of the the UTS. i.e to find the yield stress multiply the first number by the second number divided by 10.
Yield stress is where the bolt starts to deform plastically. i.e it won't return to it's original shape. UTS is where it breaks. The units of these are both N/mm^2. To find the force you may apply (in Newtons) multiply by the cross sectional area of the bolt. Then to find the weight you may apply in kilos, divide the force by 10.
Easy as pie!!! (or should that be pi?) Sorry. I'll get me coat
Oh, and all of that mumbo jumbo applies to tensile loading. There's loads more for different situations.
EDIT: Dave's posted while I was making tea!!! As you can see we've already found two different stresses!
Tractor Dave
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is it brand new or been used before? 
Tractor Dave
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THE may stand for the grade of steel or the hardening/tempering process it's gone through, but i can't be sure of that. Well at least you haven't got to take into account work hardening or fatigue!
