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As the hollow steel shaft shown rotates at 180 rpm, astroboscopic measurement in

ID: 1815772 • Letter: A

Question

As the hollow steel shaft shown rotates at 180 rpm, astroboscopic measurement indicates that the angle of twist of theshaft is 3 degree. Knowing that G = 77.2 GPa, determine (a) thepower being transmitted, (b) the maximum shearing stress in theshaft. From the Fig.3.68 we know L=5 m Outer diameter is 60 mm. As the hollow steel shaft shown rotates at 180 rpm, astroboscopic measurement indicates that the angle of twist of theshaft is 3 degree. Knowing that G = 77.2 GPa, determine (a) thepower being transmitted, (b) the maximum shearing stress in theshaft. From the Fig.3.68 we know L=5 m Outer diameter is 60 mm. Inner diameter is 25 mm.

Explanation / Answer

N = 180 rpm = 2N/60 = 2*180/60 = 18.85 rad/sec = 3 degrees = 3 * /180 = 0.05236 rad L = 5m J = (0.064-0.0254)/2 J = 1.9744 *10-5 m4 we know that T/J = G/L T = 77.2*109*0.05236*1.9744*10-5/5 T = 15.962 kN.m (a) Power,P= T P = 15962*18.85 P = 300 kW (b) max =T*r/J max = 15962*0.03/1.9744*10-5 max = 24.2 MPa