Torsional Oscillations

Torsional Oscillations

 

oscillations of structural elements and parts of machines, manifested in periodically varying torsional strain.

An example of torsional oscillations is the harmonic motion of a torsion pendulum in the form of an elastic rod fastened at one end and with a massive disk at the other. The torsional oscillations of a pendulum are used in various physics instruments, for example, to determine the elastic modulus of shear, the coefficient of internal friction of solids, and the coefficient of viscosity of liquids. In structures of machines and mechanisms, torsional oscillations are usually an undesirable feature. This is especially true for the crankshaft of piston internal-combustion engines. For example, when the frequency of the variable torque arising during the operation of the engine coincides with one of the natural torsional oscillations of the engine shaft, large resonance torsional oscillations of the shaft may arise, which may lead to breakage of the shaft. Under certain flight conditions, the action of aerodynamic forces sometimes leads to self-excited flexural torsional oscillations of the wings of aircraft (flutter), which may lead to destruction of the wing.

References in periodicals archive ?
And the quasisteady hypothesis (QSH) was applied to describe the nonlinear aerodynamic forces, whereafter Nigol and Buchan [6, 7] proposed a galloping torsional mechanism based on a two-DOF torsion-oscillator model coupled by vertical and torsional oscillations. They proved that torsional oscillation sometimes plays a crucial role to excite the galloping phenomenon, especially for the bundled conductors.
For the positively sloped gradient, torsional oscillations were damped.
The sensors are designed to accurately measure torque even if the ratio of peak to average torque is high, such as when starting, stopping, or reversing high inertia loads, during torsional oscillations, and in diesel and single-cylinder engine drivelines.
Through their functions which compensate coaxial errors in the radial, axial and angular plans, and also damping torsional oscillations, elastic couplings determine the mechanical system efficiency improvements, as well as simplification of transmition maintenance.
The optical sensors were mounted on the two opposite sides of the coupling rubber elements, at the engine-side and brake-side, respectively, in order to track the torsional oscillations affecting the rubber elements.
Such conditions occur when starting, stopping, or reversing high-inertia loads, during torsional oscillations, and in diesel and single cylinder engine/compressor drivelines.
Claire Jacobs [1] studied the transient effects considering the small amplitude torsional oscillations of disks.
where c[phi]-the coefficient of torsional stiffness of the element, N m ra[d.sup.-1]; [[omega].sub.[phi]]-the angular frequency of the natural torsional oscillations, [s.sup.-1].
where [c.sub.[phi]]--the coefficient of torsional stiffness of the element, N x m/rad; [[omega].sub.[phi]]--the angular frequency of the natural torsional oscillations, [s.sub.-1].
Claire Jacob [4] has studied the transient effects considering the small amplitude torsional oscillations of disks.
In this case it is the GR/ES coupling's softness which is important to cope with the torsional oscillations from the diesel engine acting on a high inertia load.
Subsurface flow patterns include features like torsional oscillations, jetlike disturbances that start near the poles and move toward the equator during each solar cycle.