Inertia Member Research Articles

Dynamics of a dual-mass resonant vibration screen in a first approximation

The decision on creation of a new energy-efficient vibration screen using combination parametrical resonance is presented. The decision makes it possible to expand functional and operational opportunities of vibration machines. Dynamic and mathematical models of a dual-mass resonant vibration screen are presented. Differential equations of the machine motion are given. The principle of work of a resonant vibration screen is described. The trajectory of motion of the center of mass of the system of pendulums of the inertia member of the parametrical drive during their running in on racetracks is given. A method of reducing the data on a dual-mass system to a single-mass one is presented. At the same time an additional condition on the stiffness of elastic members of the oscillatory system is introduced. The value of the coercive force under steady-state resonant oscillations is identified. Ratios between the masses of actuating devices, damping coefficients and linear displacements of the actuating device are obtained. The parametric resonance coupled with the phenomenon of self-synchronization makes it possible to realize self-controlled and self-supported proper motion of the machine. Real samples of dual-mass oscillatory systems with one and two parametrical vibration generators are presented. On the basis of the results obtained for prototypes of a dual-mass system the conclusion about the stability of the resonant operating mode is drawn. The results of this work can be used to produce new highly efficient resonant vibration machines.

INTERNAL FRICTION BEHAVIOR OF THE STANDARD ANELASTIC SOLIDS IN LOW FREQUENCY INTERNAL FRICTION MEASUREMENT

Internal friction behavior of the standard anelastic solid has been described by τσ (the relaxation time at constant stress) and τε (the relaxation time at constant strain) of a three-parameter mechanical model. The effect of the inertia member in a vibration system on the internal friction values measured is not avoidable in a forced vibration experiment. When the measured internal friction values of a material are larger and the measuring frequency and resonant frequency of the vibration system are comparable to each other, the effect of the inertia member of the vibration system cannot be neglected.

Vibration damped hand-held rivet bucking tool

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Rubber torsional vibration damper with cooling means

A vibration damper for rotating members consists of a hub member joined to an inertia member by a plurality of elastic elements. Cooling fins on the inertia member and between the elastic element provide for dissipation of heat from the inertia member and the elastic elements. The cooling fins are parallel to the side surfaces of the insertia member. In an alternate embodiment, the cooling fins are angled to the side surfaces of the inertia member to augment the cooling effect of integral fins therein. In further alternate embodiments the hub member is bifurcated and the cooling fins and elastic member are oriented at angles to the axis of rotation of the hub.

Torsional damper for maximum energy absorption with equilibrated polydimethylsiloxanes as damping fluids

Shear viscosity and effective shear modulus, quantities related to the complex viscosity, have been measured as functions of frequency for five polydimethylsiloxanes commonly used as damper fluids. Maximum energy dissipation is obtained by realizing a damper whose damping constant times the shear viscosity divided by the product of effective shear modulus and moment of inertia of the inertia member equals one. Experiments show that in this tuning the dissipated energy when polydimethylsiloxanes are used as damping fluids can be as much as a factor of two higher than the maximum dissipated energy when using Newtonian fluid.

Torsional vibration damper having two part hub

A torsional vibration damper and method and apparatus for its manufacture. The outer inertia member carries a radially inwardly extending web, the web sandwiched by a pair of elastomer members. A two-piece hub sandwiches the elastomer members, the two hub pieces being held together as by swaging or by rivets. Tooling for the swaging mode of assembly is shown such that the elastomer members are deformed from an original to a final configuration, and the swaging then accomplished with a single continuous movement. The swaging assembly apparatus for the device includes Belleville springs, the apparatus limiting the maximum force applied to that portion of the hub members controlling the assembled elastomer thickness. The damper configuration facilitates low specific energy dissipation and large elastomer-to-metal interface area to thus tend to lower shear stress in the elastomer. In addition, should the elastomer fail in use, the damper inertia mass is mechanically constrained to remain with the hub assembly. The two hub pieces cause radial extrusion of the elastomer, the extruded portions contacting the inertia member, the latter guiding and defining the extrusions.

Measurement of Snoek Damping in Sheet Specimens

The standard Kê pendulum was modified to accommodate sheet specimens. Redesign of the specimen clamps, support rods, and inertia member made it possible to handle sheet specimens 125 mm in gauge length and 6 mm in width. Because deformation was found to distort the Snoek peak, specimens were prepared by spark machining or milling rather than by shearing. The close similarity of the background damping level and the Snoek peak height and shape for sheet and corresponding wire specimens, as well as the low amplitude dependence observed in the sheet specimens, demonstrated the acceptability of the pendulum modifications and specimen shape.

Apparatus for Direct Determination and Continuous Recording of Internal Friction at Constant Amplitude

An apparatus is described in which internal friction at constant amplitude is continuously determined in terms of directly measured electrical and mechanical parameters of the system without recourse to a secondary method of calibration. The specimen, in the form of a wire, serves as the torsion member in a torsion pendulum which is maintained in sustained oscillations by an electromechanical system employing positive feedback. Attached to the inertia member of the torsion pendulum are two coaxial coils which are located in the field of a permanent magnet. The emf generated in one of the coils (pickup coil) by the motion in the field is amplified, converted into a square wave and fed back into the other coil (the driver) through a gain control circuit. The power fed back into the driver coil is controlled by a servoloop in such a way as to maintain the amplitude of oscillation constant. The internal friction is proportional to the setting of the gain control unit in the driver circuit and is displayed continuously on a strip chart recorder. Internal friction values measured on this device agree to within better than 2% with those measured from the logarithmic decrement.

Automatic Torsion Pendulum for the Continuous Recording of Internal Friction at Constant Amplitude and Very Low Frequencies

A torsion pendulum of the inverted type is maintained in oscillation at constant amplitude by means of an electric device. The mechanical oscillation gives rise to a frequency modulation which is detected in an original demodulator. The signal is amplified and used to supply two driving coils acting on small permanent magnets mounted on the inertia member. The amplifier is controlled by an error signal coming from the comparison of the amplifier input signal and a reference. An example of record showing internal-friction peaks in neutron irradiated iron is shown.

Apparatus for Continuous Recording of Internal Friction

An internal friction apparatus based upon the principle of the torsion pendulum is described. Attached to the inertia member of the pendulum are two coaxial coils which are located in the field of a permanent magnet. Oscillations of the pendulum induce an emf in one coil (the pick-up coil). The signal is amplified and converted into a square wave of constant amplitude which is used to energize the other coil (the driver coil). Interaction between the driver coil and the magnetic field maintains the system in oscillation, the amplitude being proportional to Q. The output of the pickup coil is measured on a strip chart recorder. After a straightforward calibration procedure, the Q of the system is quantitatively related to the output. The device has been used from 4°K to 150°C.