Torsional Beam Spring

Torsional beam spring design absorbs the load energy by its twisting action through an angle zero. Fig. 4.32 is an example of its behavior is that of a shaft in torsion so that it is considered to have failed when the strength of the material in shear is exceeded.

For a torsional load the shear strength used in design should be the value obtained from the industry literature (material suppliers, etc.) or one half the ultimate tensile strength, whichever is less. Maximum shear

Example of a shaft under torque

stress on a shaft in torsion is given by the following equation using the designations from Fig. 4.32:

where T= applied torque in in-lb, c= the distance from the center of the shaft to the location on the outer surface of shaft where the maximum shear stress occurs, in. and J= the polar moment of inertia, in.4.

Using mechanical engineering handbook information the angular rotation of the shaft is caused by torque that is developed by:

where L = length of shaft, in., 6= shear modulus, psi = El2 (1 + v), E = tensile modulus of elasticity, psi, and v = Poisson's ratio.

The energy absorbed by a torsional spring deflected through angle d equals:

where Mg = the torque required for deflection 0at the free end of the spring, in-lb.

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