Forced flexural oscillation

Amplitude of the force applied to a material specimen to cause a forced flexural oscillation. 

Note A related quantity is the flexural stress which is somewhat arbitrarily defined as the amplitude of the stress in the convex, outer surface of a material specimen in forced flexural oscillation. 

Deflection of a specimen subject to a forced flexural oscillation at the point of application of the flexural force. 

Note 5 Under a forced flexural oscillation the resonance frequency... 

Note 2 For a material specimen which behaves as Voigt-Kelvin solid under forced flexural oscillations with added mass at the point of application of the applied oscillatory force, Av is proportional to the loss modulus (E")... 

There are three modes of free and forced oscillatory deformations which are commonly used experimentally, torsional oscillations, uniaxial extensional oscUlations and flexural oscillations. 

Note 4 Unlike the strain in forced uniaxial extensional oscillations, those in forced flexural deformations are not homogeneous. In the latter modes of deformation, the strains vary from point-to-point in the specimen. Hence, the equation defining the displacement y in terms of the amplitude of applied force (/q) caimot be converted into one defining strain in terms of amplitude of stress. 

Note 8 Notes 3 and 6 show that the application of the defined sinusoidal flexural forces (i), (ii) and (iii) (note 1) to a Voigt-Kelvin solid of negligible mass, with or without added mass at the points of application of the forces, results in out-of-plane sinusoidal flexural oscillations of the same frequency. 

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