Pressure and Strain: Calculation of Max Allowable Pressure

[electr]

Homework Statement

A cylindrical vessel 2m internal diameter and 4m long has a wall thickness of 6mm. Strain gauges are installed on the vessel to measure hoop strain (see FIG 6).

1)What is the maximum allowable pressure if a factor of safety of 4 is to be used?
2 )What pressure would a strain of 40 με indicate?

Homework Equations

σ= pr/t for question 1
and for question 2
εο= σο - uσz/E
σο = P X r /t and σz = P x r /2t

εο =0.00004
r = 1 m
t = 0.006 M
E = 290 GN

The Attempt at a Solution

for the 1 part i found it 0.75 Mpa

for part 2 i work it

εo = σo - σz /E

so
P = (290000/ 1/0.006 - 0.3 x 1/2 x 0.006) x 0.00004 = 0.0008367398 Mpa

is any of the above correct?if not i would like your advice,thank you in advance

 

[Chestermiller]

This looks like a duplicate of a previous thread. Is it, and, if so, why have you not just continued the previous thread? Also, there are algebra problems with your final equation.

 

[electr]

i didnt know i had to continue from the previous thread,i should go there then and post my questions?i can't understand the algebra problem,just put the numbers in the equation,is this not right?tha part 2 is the one that i had difficulties,didnt know how to solve without the poison ratio,...any advice?