Pneumatic Vibration Research Articles

An Experimental Investigation into the Semi-Active and Active Control of Longitudinal Vibrations in a Large Tie-Rod Structure

An experimental study into the use of one semi-active and two active control devices employed to attenuate the transmission of longitudinal vibrations on a large tie-rod structure is described. A tie-rod structure similar to that found in marine machinery installations was assembled in the laboratory. This type of structure was chosen because it is difficilt to apply standard passive techniques due to the static stiffness requirement. A tunable pneumatic vibration absorber was used as the semi-active device, and an inertial electrodynamic exciter and a magnetostrictive actuator were used as the active devices. The way in which these devices couple into and modify the dynamic behaviour of the tie-rod structure is discussed, and experimental results are presented showing the effectiveness of the control measures in attenuating longitudinal vibrations. Significant reductions in transmitted vibrations were achieved by all the devices and the merits of each method are discussed.

Pneumatic tool and vibration isolator mounts therefore

A pneumatic tool is disclosed which includes vibration mounts to reduce the vibration transferred to the user. The vibration mounts include a plurality of support members and at least one resilient vibration isolator connecting the support member in a spaced relationship. A compressed air conduit passes through the support member openings and includes at least one seal disposed between said support members and the air conduit.

Non-linearity compensation in a pneumatic vibration generator with a dual chamber for the variable component

This paper describes a process for complete compensation of non-linearity in a pneumatic vibration exciter with a dual chamber for the variable component. It is proved that the exciter designed accordingly generates a monoharmonic signal and the process of non-linearity compensation occurs by itself, without the necessity of additional controlling procedures.

Reconditioning crankshafts of car engines by air‐plasma spraying

At present, there are a large number of methods available for reconditioning worn crankshafts of car engines in car repair plants. The authors believe that the most efficient methods are those which enable the surface of crankshafts to be built up without melting the base. One of these methods is air-plasma spraying. The use of plasma torches with magnetic arc stabilisation and the application of powder feeders with built-in pneumatic vibrators (Authors cert No. 1799230, USSR) has made it possible to increase greatly the service properties of plasma coatings. The service life of shafts is increased mainly by ensuring a high strength of bonding the coating with a parent metal, which should be uniform over the entire surface of sprayed pins and should equal 30-40 MPa. One of the factors reducing the strength of crankshafts is the stress concentration formed at the fillet and edges of holes in pins of oil channels. This leads to failure of components of the crank of journals in these areas. When reconditioning crankshafts by spraying, it is recommended to displace the fillet into the journal to reduce the stress concentration and prevent damage of the coating in these zones (Fig. 1). In the presence of an unloading groove in the journal, the stresses in the fillet zone are distributed more uniformly. The tests show that the depth of the fillet should be (0.01—0.015) df, but for single-row carburettor engines

Active control of pneumatic vibration isolation table using two degrees of freedom controller

A vibration isolation table must have functions of both the vibrationabsorption and the fast and accurate positioning. The concept of a two degreesof freedom control may be considered to be effective to reconcile such twofunctions. In this study, a design approach is proposed to realize this typeof control system for a pneumatic vibration isolation table, which uses thecomplementary sensitivity function as an index to adjust the parameters ofcontroller. Comparing the control performance with that obtained from an usualPI controller, it can be assured that the proposed controller is useful forthe active control of a pneumatic vibration isolation table.

A two color multichord infrared interferometer for RFX

A multichord interferometer designed for the Reversed Field experiment (RFX) (R=2 m, a=0.5 m, I=2 MA) is presented. The high density expected and the rather limited diagnostic access to the plasma motivated the choice of a two-color CO2/CO laser (10.6/5.4 μm) interferometer. Due to the time-varying magnetic fields ≥0.1 T around the torus entailed by the operation of the machine, the system has been mounted on a 3 ton graphite C-shaped optical table supported by a stainless steel structure on pneumatic vibration isolators. This led to long term stability of alignment and a very low level of mechanical vibrations. The interferometer can be moved in and out of the torus with ease by a carriage-rail system for maintenance both of the diagnostic and of the machine. The design foresees eight vertical chords spanning the arms of the C-shaped table and includes more additional measurements using a horizontal port and mirrors mounted inside the vacuum chamber. The expected accuracy in line density units is ≤1×1018 m−2, and the overall concept is that of a reliable system for high density and large size magnetic confinement plasmas.

Does vibration cause poststenotic dilatation in vivo and influence atherogenesis in cholesterol-fed rabbits?

Arterial post-stenotic dilatation (PSD) is a fusiform swelling immediately down-stream to a stenosis. It is characterized by the presence of turbulent blood flow and wall vibration which has been claimed by others to be causal by producing structural weakening. We tested the hypothesis that vibration causes PSD in vivo by attaching electromagnetic and pneumatic vibrators to the aortic wall in chronic rabbits. We also observed whether mechanical vibration of the aorta in vivo influenced the distribution of oil-red-O lesions during one percent dietary cholesterol feeding. Low mass vibration gauges were developed to measure the vibration. Electromechanical vibrators having a ceramic magnet slug within a coil supplied with 50 Hz were glued to the aorta of chronic rabbits and the vibration maintained for an average of 8 weeks. Despite greater amounts of energy imparted to the wall there was no dilatation or difference in oil-red-O staining from the controls. Five weeks vibration at 100 Hz and an amplitude equal to the normal diameter pulse also produced no dilatation. We conclude that vibration does not cause PSD in vivo and suggest that its cause is likely to involve the vascular muscle stimulated by the effect of turbulent flow on the endothelium.

Determining the parameters of the working cycle of a pneumatic vibration source with reverse-rotary motion of the unbalanced mass

Determining the parameters of the working cycle of a pneumatic vibration source with reverse-rotary motion of the unbalanced mass

Speaking tracheostomy tube

This invention relates to tracheostomy tubes and particularly to a tracheostomy tube construction and a system incorporating a talking tracheostomy tube. A pneumatic vibrator is provided for generating sonic vibrations. A tracheostomy tube includes a main airway and secondary airway. The secondary airway extends generally along the main airway for a substantial portion of its length. Furthermore there is an entryway to the secondary airway outside the entrance of the tracheostomy tube into a tracheostomy. And an exit from the secondary airway adjacent its end remote from the entryway. A source of compressed air is coupled to the pneumatic vibrator and the pneumatic vibrator coupled to the entryway to supply air containing sonic vibrations to permit the wearer of the tracheostomy tube to articulate audibly comprehensible speech.

A dynamic model of pneumatic vibration source of an impact-rotary action

A dynamic model of pneumatic vibration source of an impact-rotary action

Experimental study on the vibrational transport of bulk solids

The sliding regime in vibrational transport was investigated on a laboratory-scale vibrating conveyor driven by a pneumatic ball vibrator. It was found in the literature dealing with the theoretical basis that the Blekhman and Dzhanelydze diagram is suitable for presenting visually the systematic sliding regimes and for identifying the operating conditions which occur in practice, depending on the parameters of the vibrating device (α — inclination angle, β — azimuth angle of excitation) and on the friction coefficient (f o) of the material transported. Experiments were carried out using different sorts of model materials and the delivery speed values were measured and compared with the formula derived from theory. The accuracy of this formula is found to be good in practice. Nevertheless, an improvement of the calculation seems to be necessary in order to take into account some other parameters of the materials and technology that can influence the transport. According to the results of the dynamic and transport test of the conveyor driven by pneumatic ball vibrator, the delivery (mass flow) can be controlled easily in the range below resonance, and continuous operation of plant equipment used in the processing of granular materials (drying, granulation, cooling, etc.) can be based on this principle.

A kinetic-static study of a pneumatic reversal-rotary vibrator

A kinetic-static study of a pneumatic reversal-rotary vibrator

A study on vibration screw thread tightening by means of pneumatic control.

In the previous report, the vibration screw tightening method using a D. C. motor was discussed. In the results it was clear that the vibration tightening torque coefficient decreased more than the ordinary tightening torque coefficient, and the amount of scatter of the vibration tightening torque coefficient also decreased and then the screw thread tightened by the vibrational method was hard to loosen. In this report the pneumatic method using an air motor is studied. It is a more compact and controllable device in comparison with the vibration tightening which uses the D. C. motor. Also, the low frequency torsional vibration from 0 to 4 Hz is added to the tightening tool. The basic characteristics of the screw tightening method by means of the pneumatic control vibration is compared with the results of the ordinary screw tightening method (i.e. a constant velocity tightening method using the air motor).

A dynamic model of a resonance pneumatic vibration exciter

A dynamic model of a resonance pneumatic vibration exciter

A Study on Vibration of the Pneumatic Seal Structure of the Air Cushion Craft

A fundamental study on vibration characteristics of the air cushion craft was performed taking dynamic behavior of the pneumatic seal structure into consideration.A linearized mathematical model of the air cushion craft dynamics was derived. The effect of each parameter on the dynamic stability was obtained analytically and experimentally from the view point of negative resistance excitation system.The conclusions are as follows : 1) The dynamic stability of pneumatic seal structural vibration depends on the air transmission line characteristics and the seal configuration. The effects of these parameters on the stability criteria of the system are numerically examined.2) In the model test, the self excited vibration caused by the instability of the pneumatic seal system was observed in some range of the inlet area of fan and feedhole area in the air chamber.3) The calculated fundamental natural frequency for air cushion craft model agreed very well with model test results. The stable region varied in accordance with feedhole area in the model test, and a similar tendencies were also observed in the numerical analysis.A further study is necessary to discuss the difference between model test results and numerical analysis results.

On a Controlling Method of Amplitude and Frequency of Self-excited Vibration in an Externally Pressurized, Recessed-type Gas Bearing

A self-excited vibration induced in an externally pressurized, recessed-type gas bearing is applicable to a pneumatic vibrator. An orifice and a chamber connected to a recess produce a self-excited vibration describing a limit cycle, the amplitude and frequency of which vary with the area of the orifice and the volume of the chamber. In this paper, it is proposed, utilizing such a phenomenon, to provide the recess with an orifice of variable area and a chamber of variable volume as a powerful method to control the amplitude and frequency of the vibration, in addition to the conventional method of changing the supply pressure and the load, and the controlling ability of the proposed method is discussed theoretically and experimentally.

Dynamic model of a pneumatic vibration inducer with reverse rotary action

Dynamic model of a pneumatic vibration inducer with reverse rotary action

Pneumatic vibration isolator and suspension system

A self-positioning shock and vibration isolating suspension system is disclosed which incorporates one or more pneumatic mounts for supporting a load on a base. Each pneumatic mount comprises a hollow elastomer body with a diaphragm at each end, means for connecting one diaphragm to a base and the other to the load, means for pressurizing the elastomer body with a fluid so that the diaphragms and the fluid acting thereon form a pneumatic spring having a spring stiffness less than that of the hollow body, and means for varying the fluid pressure within the elastomer body in accordance with changes in the magnitude of the load.

Design of a pneumatically isolated servo‐controlled floor system for a dedicated computer wafer manufacturing facility

The equipment used to fabricate microelectronic computer wafers have stringent environmental vibration limits; but pneumatic isolators, incorporated into a complete vibration isolation system, can meet those stringent demands. This paper first reviews basic vibration isolation theory and then describes a facility that uses pneumatic vibration isolation in its dedicated computer wafer manufacturing area.

Asymptotic solution of the problem of oscillations of the plate of a pneumatic vibrator

Asymptotic solution of the problem of oscillations of the plate of a pneumatic vibrator