biomech
Bioengineer
- Jan 11, 2002
- 4
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.
Thanks.
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.
Thanks.
