youngs modulus, stress strain?

hello_there_jim

how do you get the stress and strain! is the length and diameter of the piece given, if not how do i work it out?

PurpleFistMixer

where:
E is the Young's modulus (modulus of elasticity)
F is the force applied to the object;
A0 is the original cross-sectional area through which the force is applied;
ΔL is the amount by which the length of the object changes;
L0 is the original length of the object.

Yes, I did just take that straight off wikipedia. : p

hello_there_jim

please, can ya tell me simle terms, i know its stress over strain but how do you get the stress and strain???

hello_there_jim

how do ya get the csa, i think i got it if i know this then!

Frolick

Stress is equal to the load or force (in kN) over the sectional area( eg. a bar thats 15mm wide and 8mm deep multiply them to get the sectional area)

Strain is extension over orginal lenght, orginal lenght is grand and extension is New lenght minus the orginal lenght

Gileadi

In english, strain is a dimensionless term (like a percentage) that describes the change in length to the original length. Stress is the force applied to the object, divided by the area that it acts over.

fabbydabby

Yep, you can think of stress like pressure... it's quite similar and help you remember it! Stress and Pressure are both force per unit area.

hello_there_jim

are we given the size of the bar?

hello_there_jim

(ii) Youngs Modulus: Select point on elastic region of diagram eg. (32,0.4)

Diameter = 10mm, Gauge length = 60mm.
Youngs Modulus =

Strain
Stress Stress =

CSA
Load =

78.55
32 = 0.407kN /mm²
Strain =

OrigLgth
Extension =
60

0.4 = 0.0067



how did they get the CSA here?

Frolick

You should be,or enough info to get it, or they might be really nice and ask you to plot a stress/strain graph (answers already give)

Frolick

Gauge lenght by the diameter (cone formula) It think

hello_there_jim

Frolick wrote: »

You should be,or enough info to get it, or they might be really nice and ask you to plot a stress/strain graph (answers already give)

in the examinations website, thers an answer to an exam question and you had to draw the graph and then work out tensile strength and youngs modulus! how do you read it off the graph?

Frolick

Stress/strain graph?

hello_there_jim

yes!

Frolick

Right thake any corresponding point on the graph (usually the secong or third) and put stress over strain to get young's and for tensile strenght, i'm looking for that in my book and can;t find it lol

EDIT
Quote from book "Tensile strenght is the maximum force or load, in newtons or kilonewtons, applied to a specimen before it breaks or factures, divided by its orginal cross-sectional area. it can be read from the graph

hello_there_jim

HOW DO YOU GET THE CSA?

Frolick

Link me to the question

hello_there_jim

its the 2006 engineering exam questiin, on examinations.ie

Frolick

Gauge lenght is 60mm right? Radius is 30, put in pieRsquared to get CSA

bernardo mac

Keats can be a bitch alright Frolick but he was a tough yet sensitive,sickly guy who could escape on a high through language,nature and his imagination.He became hip in his day and lived his short life to the full in an artistic sense.His poetry recreates intense moments of delight;he longs to remain in those periods of release from pain.He is keenly aware of human suffering[was a surgeon] and feels the pain of others.His anaesthetic is nature,poetry,his imagination but is only a temporary respite.HE is full of uncertainties,longings,a desire to escape yet remain in this [for him]world of rich beauty and tragedy.He was/is a bright star...immortal?

PurpleFistMixer

bernardo mac wrote: »

Keats can be a bitch alright Frolick but he was a tough yet sensitive,sickly guy who could escape on a high through language,nature and his imagination.He became hip in his day and lived his short life to the full in an artistic sense.His poetry recreates intense moments of delight;he longs to remain in those periods of release from pain.He is keenly aware of human suffering[was a surgeon] and feels the pain of others.His anaesthetic is nature,poetry,his imagination but is only a temporary respite.HE is full of uncertainties,longings,a desire to escape yet remain in this [for him]world of rich beauty and tragedy.He was/is a bright star...immortal?

Um... which thread was this supposed to be in?

KittyeeTrix

You could post the question over on the Science (physics and chemistry) forum if ye stuck
Those guys over there always full of good info:)