Desining a aluminium rod

Philip Wong

Hi guys,
I'm studying my first semester in engineering, I was giving the first assignment in my material science class which I'm not so sure on how to get started on.

The assignment was to ask us to design a aluminum rod which has the following specification:
1) Withstand an applied force of 200kN
2) Maximum allowable stress on the rod is limited to 170Mpa with a strain of 0.0025mm.mm^-1
3) Rod must be at least 3.8m long but deform elastically no more than 6mm when force is applied

I was thinking of a "I" shape rod, but am not sure were I on the right track or what should I include (e.g. width, depth, and shape) to sufficiently uphold the conditions.

Secondly can someone please tell me how do I convert load-guage length to engineering stress and strain?


Thanks,
Phil

Jobrag

How is the force to be applied, along the length of the rod, or at 90 degrees?

Philip Wong

the question is just say "An aluminium rod is to withstand an applied force of 200 kN".
I guess its at orthogonal

Chestermiller

If the load is applied perpendicular to the rod (orthogonal), then you need to know the boundary conditions on the ends, and solve the problem as a beam bending problem. It sounds like, in this problem statement, a tensile load is applied on the ends. Try out some different shapes and see what you get. Start with a circular cross section for simplicity. Why? If you can't solve that, you are not going to be able to do more complicated cross sections.