# Bending Moment question

1. Jun 15, 2010

### mzha109

1. The problem statement, all variables and given/known data
The problem can be found here:

Sorry the picture is so small. I guess you can download it and then zoom in or something. The main question I'm interested in 2b. Calculating the moment.

position of neutral axis: 37.14mm
Second moment of area: 2.83 x 10^(-6)

2. Relevant equations
The flexure formula.

3. The attempt at a solution
My answers for maximum compression : 58.4MPa and maximum tension: 34.5MPa. They're off by about 4Mpa respectively.

2. Jun 16, 2010

### PhanthomJay

3. Jun 16, 2010

### mzha109

Stress tensile=30.93 MPa, Stress compressive=-61.99 MPa.

I can't figure out why I'm wrong.

4. Jun 16, 2010

### PhanthomJay

Me neither,so maybe they're wrong?

5. Jun 16, 2010

### mzha109

I hope not. It was an exam question. I'd imagine they'd be more careful.

6. Jun 17, 2010

### pongo38

Your answers are correct for bending alone, but there is an additional 3.6 MPa for the axial compression. In other words apply the combined stress formula N/A +- M/Z

7. Jun 17, 2010

### PhanthomJay

Nice catch, thanks, we completely overlooked that.

8. Jun 17, 2010

### mzha109

Oh of course I can't believe I forgot that. Thankyou so much.