Illustrated is a rectangular steel bar with simple supports at the ends and loaded by a force F at the middle; the bar is to act as a spring. The ratio of the width to the thickness is to be about b = 10h, and the desired spring scale is 1800 lbf/in.
(a) Find a set of cross-section dimensions, using preferred fractional sizes from Table A€“17.
(b) What deflection would cause a permanent set in the spring if this is estimated to occur at a normal stress of 60kpsi?

3 ft Section A-A