3 point bend test

[SH2]

Does anyone know how to estimate the vertical deflection of a polymer test specimen (based on 2% strain) in a 3 point bend setup?
Thanks in advance.

 

[CoryPad]

What is your definition of strain?

You can calculate the elastic deflection using the equation:

[δ] = [F l³]/[48 E I]

where

[δ] = beam deflection
F = applied force
l = beam length
E = elastic modulus
I = second area moment

You can calculate the onset of plastic strain in the outer fiber with the equation:

[σ] = [F l t]/[8 I]

where

[σ] = yield stress
F = applied force
l = beam length
t = beam thickness
I = second area moment

You can estimate the deflection at 2% strain by increasing the values a little over those for plastic strain onset.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.