Engineering coursework help

Repta

Repta

Repta

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Im strugling with some pretty simple structures calculations. Just dont know the formula needed. I need to work out:

Yield strength
Ultimate strength
Ductility Index at max load
True stress and strain at max load

I have load and displacement results and the area and length of aluminium and steel rods. Does anyone know the formulas needed?

Thanks
 
ejr22 said:
The formula is.....
...Pay attention in class.
Click to expand...

I did but i dont have access to my notes at the minute and those are the only ones i cant remember. I did google it but so many different formula appear makes it pretty difficult to get the right one
 
Mechanical engineering?
Stress is force/cross sectional area
Strain is elongation/original length
Plot the stress strain graph then spot for yield strength and the other things I have no idea about :p.
 
The Craig said:
Mechanical engineering?
Stress is force/cross sectional area
Strain is elongation/original length
Plot the stress strain graph then spot for yield strength and the other things I have no idea about :p.
Click to expand...

Aeronauctical. Got the graphs and was going to just get the info from them but for some reason the cw spec ask for the formulas for calculating each to be written down, which has me stumped
 
Got a Masters in this and have forgotten :(

- Ultimate you mean UTS?
- Yield strength is the point at which a material will not return to its original length/size (becomes inelastic). Found by looking at a stress strain plot.

Erm back to basics, you know the formulae for stress and strain I guess ? edit: given above anyway.
 
have you even tried google ? im sure even wikipedia has the formulas for those

source : did similar coursework the other week
 
With google and some searching you will find the right formulae. If you know the basics then you should be fine.

1st year I presume ?
 
-Ad- said:
With google and some searching you will find the right formulae. If you know the basics then you should be fine.

1st year I presume ?
Click to expand...

Yea 1st year, can work most of it out from graph. Just a bit stumped that im asked to give formula for things like yield strength. Prob just a mistake in the coursework spec. Just going to use the graph as it what everywhere seems to be saying
 
Thanks for the help pretty much done now

Justin said:
This reminds me of all the boring stuff I was taught when I did aerospace engineering.
Click to expand...

Im just hoping it gets a bit more interesting dont think ill ever find something more boring than fluid mechanics or stupid drawing lectures :/
 
Where about are you doing your degree? I only did this last year, and I can barely remember it:(. My heads to full of Castigliano's method, and bending moments and other fun stuff.
 
jr1104 said:
Where about are you doing your degree? I only did this last year, and I can barely remember it:(. My heads to full of Castigliano's method, and bending moments and other fun stuff.
Click to expand...

Loughborough, unfortuently i finding the course really boring so making things a lot more difficult
 
Repta said:
Loughborough, unfortuently i finding the course really boring so making things a lot more difficult
Click to expand...

I found it a bit the same in my first year, since it was lots of rather uninteresting stuff. I'm not sure how your course is laid out, but now that I'm in my second year I find it a lot more interesting. I'm doing lots of interesting stuff now, like stealth and radar, and the design module is basically working in a group to conceive, design and model a UAV.
 
Repta said:
Im strugling with some pretty simple structures calculations. Just dont know the formula needed. I need to work out:

Yield strength
Ultimate strength
Ductility Index at max load
True stress and strain at max load

I have load and displacement results and the area and length of aluminium and steel rods. Does anyone know the formulas needed?

Thanks
Click to expand...

Engineering Stress or Normal Stress?

Read the force off the graph and divide by the area... for 1 and 2.

N/mm^2 for 1 and 2.

extension over original length for strain?

I was doing this a week or so ago, really need to get ontop of my notes!
 
jr1104 said:
I found it a bit the same in my first year, since it was lots of rather uninteresting stuff. I'm not sure how your course is laid out, but now that I'm in my second year I find it a lot more interesting. I'm doing lots of interesting stuff now, like stealth and radar, and the design module is basically working in a group to conceive, design and model a UAV.
Click to expand...

Everyone ive talked to has said it gets a lot better in second year and it seems to get better next term as well a bit. More design and workshop and a bit less theory. Guess ill find out soon.

Concorde Rules said:
Engineering Stress or Normal Stress?

Read the force off the graph and divide by the area... for 1 and 2.

N/mm^2 for 1 and 2.

extension over original length for strain?

I was doing this a week or so ago, really need to get ontop of my notes!
Click to expand...

Thanks got it sorted now
 
Repta said:
Everyone ive talked to has said it gets a lot better in second year and it seems to get better next term as well a bit. More design and workshop and a bit less theory. Guess ill find out soon.
Click to expand...

It is worth waiting for, the work does get harder, but it's more focused and interesting. Good luck with it.
 
Thankfully I dont do structures anymore, but here's the link to an older version of our 1st/2nd year structures data book, bound to be something useful in there somewhere.

If you've got the stress/strain plot (assume this is the graph you've mentioned) then iirc:

The yield stress can be read from the point where the plot reaches the elastic limit and is no longer linear. (hookes law no longer applies).

The UTS can be read as the final stress just before failiure (top of the plasticity curve, this assuming there is no unloading/work-hardening etc)

I've never heard of the ductility index but would guess it is a ratio of how much strain the specimen exhibits within the plastic region, again readable from the graph.
 
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