# Stress and Strain (Finding the thickness of truss members)

1. Jun 13, 2012

### D0m

Hi guys i have a exam coming up soon and stress is starting to kick in. Im good with stress and strain, but im just confused on this question and don't understand what i need to be doing. I've tried every formula and i just cant seem to get question 5 out. The answears for this question is underneath the question.

Please have a look at it and tell me what you think, it will also be much appriciated if can write down a solution for them. The question is in the attachment.

Thanks, Dom

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2. Jun 14, 2012

### PhanthomJay

What is the formula for determining axial stress in a member?

3. Jun 14, 2012

### D0m

stress= P/A

4. Jun 15, 2012

### PhanthomJay

Yes.
The controlling case for stress and axial load is the compression case, since the load is the greatest and the allowable stress is the smallest. So you know P and and you know the allowable stress. Solve for the required cross sectional area of the hollow tube, A, and from that you can determine the required wall thickness from the given data of the tube's diameter.

5. Jun 16, 2012

### D0m

I understand what you mean but i just dont know how to get started

6. Jun 16, 2012

### PhanthomJay

A = P/s. Solve for A. Watch units. What do you get for the area ? Show your work.