Maryland institute handbook . r the loadis removed if the elastic limit was not exceeded. The resultant stress in a shaft under torsional strainis in the nature of a shear at each side of a plane cuttingacross it at any point. The shearing stress in a round shaft varies from 0 atthe center to a maximum at the circumference. If ^r = the safe torsional moment of resistance of ashaft; then RT should equal or RT=; butRT must equal the permissible working stress «S of thematerial in pounds per square inch multiplied by Zt, thesection modulus for torsion; a constant determined bythe shape o
Maryland institute handbook . r the loadis removed if the elastic limit was not exceeded. The resultant stress in a shaft under torsional strainis in the nature of a shear at each side of a plane cuttingacross it at any point. The shearing stress in a round shaft varies from 0 atthe center to a maximum at the circumference. If ^r = the safe torsional moment of resistance of ashaft; then RT should equal or RT=; butRT must equal the permissible working stress «S of thematerial in pounds per square inch multiplied by Zt, thesection modulus for torsion; a constant determined bythe shape of the cross-section of the shaft. Now, as RT = SxZt so also mustWXL = SXZt The permissible unit working stress S may be takenas 9,000 lbs. per square inch for steel. The section modulus for torsion or the constant Zt for a Circle = 3-^3 = *16 2a3Square = —- = a3 approx. (See Fig. B) Example. Required the diameter of a solid shaft—provided with a lever arm 15 long, from the end of which 90 Shear and Torsion *—d.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectmechanics, bookyear19
