Begin with a 1-in-square thin-wall steel tube, wall thickness t = 0.05 in, length 40 in, then introduce corner radii of inside radii ri, with allowable shear stress τall of 11 500 psi, shear modulus of 11.5(106) psi; now form a table. Use a column of inside corner radii in the range 0 ≤ ri ≤ 0.45 in. Useful columns include median line radius rm , periphery of the median line Lm , area enclosed by median curve, torque T, and the angular twist θ. The cross section will vary from square to circular round. A computer program will reduce the calculation effort. Study the table. What have you learned?

1 in l in