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ASTM F 382

ASTM F 382

ASTM F 382

This standard is for the static bending properties of metallic bone plates. My question is how the equation for Bending stiffness was derived. The equation they give is the following:

Bending Stiffness = (5/324)*B^3 * Bending rigidity

Where: B = distance between roller supports and Bending rigidity is the max slope of the bending moment - deflection curve.

They state that the Bending Stiffness is the average value of EI for the plate. However, when I look at the equation for 4-point bending which is as follows.

DeltaX = {(P*a)/24EI}*(3B^2 - 4a^2)

a = distance from support to loading (P)

Solving for EI and assuming ((P/2)*a)/deltax = bending rigidity
one gets;

EI = Bending rigidity * (3B^2 - 4a^2)/24

This is no where near the equation that they have established for the standard.

Would someone please enlighten me on the origin of this equation.


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