Youngs Modulus Calculation


by ar202
Tags: calculation, modulus, youngs
ar202
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#1
Apr30-13, 06:20 PM
P: 45
I've got a beam of Length 500mm under third point loading.

width = 100mm depth=100mm

Force at rupture is 6.627kN

change in length =0.000019m = 0.019mm

can someone help me with the Youngs modulus please

i'm getting 6.87 GPa... which seems a bit low for concrete? Although possible as i cast it myself!
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PhanthomJay
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May1-13, 03:14 PM
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I am not sure how you are arriving at this figure, but regardless, if you are looking at rupture load deflection, you are not going to get Youngs modulus, you will get a rupture modulus.
Concrete does not behave elastically except for reasonably low levels of stress and strain. When you approach rupture load, the stress strain relation is far from linear, and curves and flattens out considerably.

If you want Youngs modulus, you need to use smaller values of load in varying increments, and calculate it by using the deflection formula for a simply supported beam under mid point load. At higher values of load, you get a secant modulus, which is different.
ar202
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#3
May1-13, 04:06 PM
P: 45
Quote Quote by PhanthomJay View Post
I am not sure how you are arriving at this figure, but regardless, if you are looking at rupture load deflection, you are not going to get Youngs modulus, you will get a rupture modulus.
Concrete does not behave elastically except for reasonably low levels of stress and strain. When you approach rupture load, the stress strain relation is far from linear, and curves and flattens out considerably.

If you want Youngs modulus, you need to use smaller values of load in varying increments, and calculate it by using the deflection formula for a simply supported beam under mid point load. At higher values of load, you get a secant modulus, which is different.
The smalles load value i have is 0.33kN and a deflection of 0.011mm which still gives me a pretty low value of E... 9GPa i think.

ar202
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#4
May1-13, 04:42 PM
P: 45

Youngs Modulus Calculation


Quote Quote by PhanthomJay View Post
I am not sure how you are arriving at this figure, but regardless, if you are looking at rupture load deflection, you are not going to get Youngs modulus, you will get a rupture modulus.
Concrete does not behave elastically except for reasonably low levels of stress and strain. When you approach rupture load, the stress strain relation is far from linear, and curves and flattens out considerably.

If you want Youngs modulus, you need to use smaller values of load in varying increments, and calculate it by using the deflection formula for a simply supported beam under mid point load. At higher values of load, you get a secant modulus, which is different.
ps thank you for your reply, i've run it through various values and its jumping from 9 to 30GPa. so i think ill take the 30 and run!


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