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The shear stress at a point within a shaft is: = 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 ...
The formula to calculate average shear stress τ or force per unit area is: [1] =, where F is the force applied and A is the cross-sectional area.. The area involved corresponds to the material face parallel to the applied force vector, i.e., with surface normal vector perpendicular to the force.
Here is yield stress of the material in pure shear. As shown later in this article, at the onset of yielding, the magnitude of the shear yield stress in pure shear is √3 times lower than the tensile yield stress in the case of simple tension. Thus, we have: =
T is the applied torque L is the beam length G is the modulus of rigidity (shear modulus) of the material J is the torsional constant. Inverting the previous relation, we can define two quantities; the torsional rigidity, = with SI units N⋅m 2 /rad. And the torsional stiffness,
The applied stress to overcome the resistance of a perfect lattice to shear is the theoretical yield strength, τ max. The stress displacement curve of a plane of atoms varies sinusoidally as stress peaks when an atom is forced over the atom below and then falls as the atom slides into the next lattice point. [18]
This is only the average stress, actual stress distribution is not uniform. In real world applications, this equation only gives an approximation and the maximum shear stress would be higher. Stress is not often equally distributed across a part so the shear strength would need to be higher to account for the estimate. [2]
Torsional stresses: = where is the torsional shear stress, is the applied torque, is the distance from the central axis, and is the polar second moment of area. Note: In a circular shaft, the shear stress is maximal at the surface of the shaft.
The stress due to shear force is maximum along the neutral axis of the beam (when the width of the beam, t, is constant along the cross section of the beam; otherwise an integral involving the first moment and the beam's width needs to be evaluated for the particular cross section), and the maximum tensile stress is at either the top or bottom ...