# Homework Help: Stress Concentration

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1. May 10, 2017

### gv3

1. The problem statement, all variables and given/known data
The stress distribution along the section of a bar is shown below. From this distribution, find the approximate axial force P in kip.

2. Relevant equations
δavg=P/A
A= (.6+.6)(.5)
δavg=30ksi

3. The attempt at a solution
P=(30ksi)(.6in2)=18kip

It says this answer is wrong but i don't see where i am going wrong here? .8in is the diameter of the whole so it is not considered when finding the area.

2. May 10, 2017

### Staff: Mentor

3. May 11, 2017

### gv3

Not sure. ive still been unable to get the answer. I dont see any other way to approach this. My professor approached it the same way when he did a similar problem.

4. May 11, 2017

### Nidum

This might be a silly . The average stress is actually a bit less than 30 ksi so your answer for force P is a little high . As near as can be judged from such a small diagram the average stress is actually about 28.7 ksi giving a value of force P of about 17.2 kip .

So maybe 17 kip is the 'correct' answer ?

5. May 11, 2017

### gv3

The next question asked for the max stress/average stress and used 30ksi as he average stress which gave me the right answer. Im hesitant to try because i only have 2 attempts left.

6. May 16, 2017

### Mapes

Have you been given an empirical equation such as the one in Table 6-1-2 here? In this case, by plugging in the numbers, the stress concentration factor would be 2.23, and the nominal stress would therefore be 16.12. But this is just an empirical fit, of course.