# Archived Pinching a pipe

1. Aug 4, 2014

### physics337

1. The problem statement, all variables and given/known data

A cannula (hollow tube) is gripped by a force (1/3 of the cannula length). What is the deformation of the cannula due to the force.

E=2.9x10^7 psi, Cannula Length L = 0.75 inches, gripped length = 0.25inches, Force =1 pound, outside diameter=0.02inches, inside diameter= 0.012inches

3. The attempt at a solution

Find the Moment of Inertia I; I= ∏((d_o)^4-(d_i)^4))/64 =6.8x10^-9
Deformation = FL/EI; = ((1)(.25))/((2.9x10^7)(6.8x10^-9))= 1.26 inches

2. Feb 5, 2016

### haruspex

Likely this post got no responses originally because the set-up is not clearly specified and the poster hasn't asked a question.
It says the pipe is pinched, so is this a bilateral squeezing applied over some length of the pipe? If so, the deformation clearly cannot be more than the intenal radius of the pipe.
The calculation is more as though this is a bending moment, and the answer is a deflection.
Either way, the significance of the length of the whole pipe is mysterious.