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Deflection in a cylindrical tube. (please help!!!)

Question asked by Frank Ardavin on Aug 30, 2012
Latest reply on Aug 31, 2012 by Frank Ardavin

Good afternoon,


Im working with deflections at this moment, im trying to get the same numbers in SolidWorks simulation as I get them by formulae.


This is what im doing in SW.


Def 1.png


I'm appliying a gravity load.

Holding the tube by both circular sections in the ends of the tube,


O.D. is 2In

I.D. is 1.81In

Lenght is 6.25In


The material applied is forged Stainless Steel with the next properties:


Modulus of elasticity: 29007547.53 PSI

Mass density: 0.289018 Lb/in^3


Im getting a mass of 1.027 lbs which is right calculated in both SW and by formula.


So by running this test in Solid works I seem to be getting:


3.245052937 E-07


The Theory procedure is the next:


Delta= [5*M(L^3)]/(384*E*i)




Delta= Deflection due to a uniform Load (inches).

M= Uniform Load (Lbs.) (in this case Mass).         -->          1.027 Lbs

L= Total Lenght.(inches)                                      -->          6.25 In

E= Modulus of elasticity in tension (PSI)               -->          29 E6

i= Moment of inertia of cross section. (in^4)           -->          [pi*(O.D.^4 - I.D. ^4)]/64  or for this case 0.258551543 in^4


So by calculating this with formula I get a deflection factor of 4.35 E-07.


So this 2 numbers are not equal, and I wanted to know what am I doing wrong in SolidWorks?


I appologize for my english and the grammatical errors I might have made, any suggestions will be greatly appreciated.


Thank you!!!