stress-strain calculations 1

[bsmet95]

See the attached file.

I have conducted a pull test with loadings as per the attached file. P, M, L, and area of the sample are known, and Strain was obtained in the testing.

Axial stress is obtained by using P/A. Is there any way I can calculate the bending stress due to M?

Thanks.

 

[Mece79]

Stress(due to bending) = (M*y)/I

y is distance away from neutral axis
I area moment of inertia of cross section

Euler-Bernoulli bending theory

 

[FeX32]

In general, the relation is sigma_bending= M*c/I

c is the distance from the centerline to the furthest longi. edge.
I is the are moment of inertia.

If its a 'pure' moment it can be replaced by a couple.

Although, I am not exactly sure this is what you want.



Fe

 

[FeX32]

i guess we were all writing at the same time.

Fe

 

[bsmet95]

Thanks, but I guess I didn't make myself clear.

Is there a way, using the measured strain only, to estimate the bending stress? This is part of a product development project, and I want to compare the estimated stress against my initial calculated stress.

 

[rb1957]

stress = P/A + My/I
stress/strain = E

do the math ...

 

[bsmet95]

Thanks, rb1957;

stress/strain = E is what I needed.

 

[Qshake]

It should be noted that you may not be able to reproduce your bending stress results compared to your calculations due to the influence of shear deformations, particularly for short specimens. If L is rather short and the cross-section dimensions are proportionaly large, shear deformations can be significant. On the other hand, if L is rather long and the cross section dimensions smaller, then the shear deformations become negligible.



Regards,
Qshake

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