Calculate Deformation of Pinching a Pipe

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SUMMARY

The discussion focuses on calculating the deformation of a cannula subjected to a gripping force. Given parameters include Young's modulus (E) of 2.9x107 psi, a cannula length of 0.75 inches, a gripped length of 0.25 inches, and a force of 1 pound. The moment of inertia (I) is calculated as 6.8x10-9 using the formula I = ∏((do)4 - (di)4)/64. The resulting deformation is computed as 1.26 inches, although the setup of the problem raises questions about the nature of the force applied and the relevance of the entire pipe length.

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Homework Statement



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



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
 
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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.
 

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