Trying to verify yield stress calculations for bending a pipe

[Tommy Boy]

Hi All,

I wanted to calcuate the maximum force I can place on a given iron pipe 2 ft away from a fixed end before it yields to plastic deformation and takes on a permanent set. I have enclosed 3 equations.

The first equation shows how to calculate the moment of inertia of a pipe.

Ip=pie*(Dout^4-Dinner^4)/64

Dout = outer diameter
Dinner=inner diameter

The second formula shows deflection I would get for a given load.

Deflection=F*L^3/3*E*Ip

F=Force
L=Lenght of pipe
E=Modulus of Elasticity of Iron
Ip=Moment of Inertia of pipe


The third formula I am trying to use to calculate the maximum stress for a given force over a given length of pipe.


Yield Stress Max for given load=((F*L)*h/2)/Ip

F=Force
L=Lenght of pipe
h=height of pipe or outside diameter of pipe
Ip=Moment of Inertia of pipe

I am hoping that this 3rd formula is correct and that as long as the calculated value is less than the yield stress of a given pipe material i wouldn't deform the pipe.

Any thoughts would be helpful.

Thanks,
Tom

[Kelly_Bramble]

Yes, I think...


See:

Moment of Inertia

http://www.engineersedge.com/materia...gyration-3.htm

Cantilever, single load at end

http://www.engineersedge.com/beam_be...m_bending9.htm

Cantilever, uniform load

and

http://www.engineersedge.com/beam_be...m_bending8.htm

[quote]Yield Stress Max for given load=((F*L)*h/2)/Ip[\quote]

I would just call this applied stress, as yield is a condition where the applied stress exceeds the yield stress and deformaton occurs.

To get the yield stress of the material you need to find a stress-strain curve or the material specifications of the pipe.

stress-strain.gif

[RWOLFEJR]

Hi All,

I wanted to calcuate the maximum force I can place on a given iron pipe.................


................Any thoughts would be helpful.

Thanks,
Tom

Hi Tom,

Remember that results from any formula regarding strength of materials are theoretical. So along came the safety factor...