torsiestrength

Torsiestrength is the capacity of a material or component to resist torsion, twisting about its longitudinal axis, when subjected to an applied torque. It encompasses the maximum torque that can be sustained before yielding or failure and the related twist stiffness of the member.

In linear-elastic design, torsion is described by the shear stress tau at the outer surface, given by tau = T R / J, where T is the applied torque, R is the outer radius, and J is the polar moment of area of the cross-section. The angle of twist per unit length is given by phi/L = T / (G J), with G the shear modulus; the total twist for length L is phi = T L / (G J).

For a solid circular shaft of diameter d, J = pi d^4 / 32 and R = d/2, leading to tau_out = 16 T / (pi d^3) and, for a shear yield strength tau_y, the maximum allowable torque T_max = tau_y J / R. For a hollow circular shaft with outer radius Ro and inner radius Ri, J = (pi/2)(Ro^4 - Ri^4) and T_max = tau_y J / Ro.

Torsiestrength is influenced by cross-section geometry, material properties, surface finish, and temperature, and it informs design in drive shafts, propeller shafts, torsion springs, and rotor components, as well as fatigue analyses under cyclic loading. See also torsion, shear modulus, polar moment of area, and torsional fatigue.

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