Bending stiffness of Tube rod assembly
Bending stiffness of Tube rod assembly
(OP)
A polymer tube 2.5mm diameter with a Youngs Modulus = 2 GPa that contains a metal rod diameter
0.75mm with a Young's modulus of 107 GPa. I need to know the overall bending stiffness of the
assembly.
If both materials were touching it would be simple i.e.
k = EI , where I = 2nd moment of area. and just add the two stifness values.
However, i need to know how to calculate the stiffness for the above conditions i.e. material not
touching.






RE: Bending stiffness of Tube rod assembly
RE: Bending stiffness of Tube rod assembly
y = F1 * l^3 / 48*E1*I1 = F2 * l^3 / 48*E2*I2.
F1/F2 = E1I1/E2I2, F1 = F2(E1I1/E2I2),
Ft = F2(E1I1/E2I2) + F2 = F2(E1I1/E2I2 + 1)
Now, given the Ft, E1, I1, E2, and I2, we can find the deflection y.
You can then use the calculated value for y to back calculate the effective stiffness of the assembly.
Look this over and post.
Thanks
GEFought
jfought@invacare.com