Consider a bar to be rigidly attached at one end and twisted at the other end by a torque or twisting moment T equivalent to F × d, which is applied perpendicular to the axis of the bar, as shown in the figure. Such a bar is said to be in torsion. Assumptions in Torsional equation 1. The material of the shaft is homogeneous and isotropic throughout length of shaft. 2. The shaft is circular in cross-section remains circular even after loading. 3. A plane section of the shaft normal to its axis before loading remains plane even after the torque has been applied. 4. The twist along the length of the shaft is uniform. 5. The distance between any two normal cross-sections remains same even after application of torque. 6. The maximum shear stress induced in the shaft due to application of torque does not exceed its elastic limit value. Derivation of Torsion Formula Hear R is the outer radius of the shaft. t is the maximum shear stress at the
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