Homework 5

 Example 1: A solid shaft is designed to carry a maximum torque of 286 Nm. Find the shaft diameter if the shaft is made of steel EN3, with a required safety factor of 5. D = 30 mm Given:             T = 422 Nm = 286 000 N mm              Material EN3 (tu = 270 N/mm2)              SF = 5 Req:              D = ? Solution:                 tall  = tu / SF                          …………..…….(1)                  tall  = (T r) /  [(p/32) D4] = (T D/2) /[(p/32) D4]                  tall  = 16 T / (p D3)                             ………..(2) From eqn. (1):                  tall  = 270/5 = 54 N/mm2 From eqn. (2):                   54 = (16 x 286 000) / (p D3)                   D3 = (16 x 286 000) / (p x 54) = 26 973.815 mm3                   D = 29.99 mm = 30 mm (Ans) 1) If the above shaft is made hollow with the same outer diameter and with a thickness of 2 mm. Find: A) The shaft torque capacity. (124.77 Nm) B) The reduction of the shaft weight, if the shaft length is 1 m. (4.14 kg)

.