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Note that the highest shear stress occurs on the surface of the shaft, where the radius is maximum. High stresses at the surface may be compounded by stress concentrations such as rough spots. Thus, shafts for use in high torsion are polished to a fine surface finish to reduce the maximum stress in the shaft and increase their service life.
Combining these two features with the length of the shaft, , one is able to calculate a shaft's angular deflection, , due to the applied torque, : = As shown, the larger the material's shear modulus and polar second moment of area (i.e. larger cross-sectional area), the greater resistance to torsional deflection.
The torsion constant or torsion coefficient is a geometrical property of a bar's cross-section. It is involved in the relationship between angle of twist and applied torque along the axis of the bar, for a homogeneous linear elastic bar. The torsion constant, together with material properties and length, describes a bar's torsional stiffness.
This type of stress may be called (simple) normal stress or uniaxial stress; specifically, (uniaxial, simple, etc.) tensile stress. [13] If the load is compression on the bar, rather than stretching it, the analysis is the same except that the force F and the stress σ {\displaystyle \sigma } change sign, and the stress is called compressive ...
Similarly, the torsional stiffness of a straight section is = where is the rigidity modulus of the material, is the torsion constant for the section. Note that the torsional stiffness has dimensions [force] * [length] / [angle], so that its SI units are N*m/rad.
As an example, the stress state of a steel beam in compression differs from the stress state of a steel axle under torsion, even if both specimens are of the same material. In view of the stress tensor, which fully describes the stress state, this difference manifests in six degrees of freedom , because the stress tensor has six independent ...
The book covers various subjects, including bearing and shear stress, experimental stress analysis, stress concentrations, material behavior, and stress and strain measurement. It also features expanded tables and cases, improved notations and figures within the tables, consistent table and equation numbering, and verification of correction ...
The following stresses are induced in the shafts. Shear stresses due to the transmission of torque (due to torsional load). Bending stresses (tensile or compressive) due to the forces acting upon the machine elements like gears and pulleys as well as the self weight of the shaft. Stresses due to combined torsional and bending loads.