Home HomeAnatoly T. Sukhodolsky, General Physics Institute (Russia)
The opto-hydraulic laser (actuator) to direct transform the energy of solar radiation into mechanical vibrations is described. The device consists of a chamber with active liquid and optical fiber to deliver energy of light inside. As power supplier was used solar concentrator of diameter 300 mm. The vibration generation occurs owing to oscillation a single bubble emerged on the end of fiber in liquid. The model of self-organization of heat cycle by non- linear motion of the bubble is presented to describe main strokes of transformation of radiant energy into energy of mechanical vibrations.
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TOPErnst Schonthal, The Modal Shop (PCB Piezotronics Inc) (U.S.A.)
The primary calibration of acoustic and vibration transducers are well standardized and confirmed by round robin inter laboratory test. Secondary calibrartion is also very common with traceability to primary calibration. Examples of a set-up for microphone secondary calibration are discussed regarding accuracy - frequency response testing etc. Field check using reference sources and other methods like Phantom-Calibration is discussed regarding advantages and short comings.
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Thomas Kell, Technical University of Munich (Germany)
P. Fritz, Technical University of Munich (Germany)
F. Pfeiffer, Technical University of Munich (Germany)
The aim of the research described in the paper was the evaluation of a complete mechanical model of a roller chain drive and the development of a sophisticated measurement technique to verify the model and to understand the physically processes. The main topic of the paper will be the measurement technique and the verification of the model. Roller chain drives are typically applied in combustion engines. Especially at lower rotational speeds the drive is a major noise source of the engine. The time dependent rotational speed of the crankshaft, the variable torque of the cam-shaft, the polygonal effect due to the discrete nature of a chain and the impact between a chain link and the guide or pulley excite the vibrations of the system and influences the noise and the wear of the drive. To examine these vibrations a test bench has been built. The measuring of the transversal vibrations of a strand was an unsolved problem because of the hot and oily environment and the geometry of a chain link. This could be fixed by improving an eddy-current based measuring system. In addition a method has been evolved to measure the Iongitudinal forces of a chain link. A comparison between the measuring results and the simulation results will be shown.
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Stephane Gabard, Laboratoire d'Etudes Aerodynamiques (France)
J. Peube, Laboratoire d'Etudes Aerodynamiques (France)
Christophe Picard, Laboratoire d'Etudes Aerodynamiques (France)
The reliability of a real time unsteady pressure measurement system is of great interest in many domains of industry and research. Experimental constraints often implies the presence of a pneumatic line between the pressure tap and the transducer, which causes and amplitude and a phase distorsion of the pressure signal to be measured. Corrections of this resonance phenomenon obtained by analogical (active filters) or numerical (inverse transfer function) methods, prevent any simultaneous temporal study of velocity and pressure. A mechanical method of correction consisting in reducing the tube section on a certain length (restrictor) is also generally used, but without any a priori optimization of its geometry. This paper presents a modelization of the transfer function of the pneumatic line: the analytical study displays the respective influences of the different geometrical elements of the pneumatic line. Nevertheless, the complexity of the transfer function doesn't allow the a priori determination of an optimum geometry of the pneumatic line. Our study provides a methodology to optimize the geometry of the restrictor, using a non-dissipative model of the flow in the tube, associated with a quasi-steady flow assumption in the restrictor.
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Gary A. Fleming, NASA Langley Research Center (U.S.A.)
Jonathan D. Blotter, Idaho State University (U.S.A.)
Electro-Optic Holography (EOH) is a laser based, full field diagnostic technique used to measure micron sized deflections in statically displaced or vibrating structures. When applied to dynamically excited objects, EOH yields the time averaged displacement profile of the object surface. To obtain the structural power flow from EOH measurements, the structural phase must be extracted. This paper provides an overview of the EOH technique and describes a novel method successfully used to obtain the vibrational phase from EOH measurements. Experimental results from a sinusoidally driven cantilever beam are presented in support of this new method.
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Ken L. Telschow, Lockheed Martin Idaho Technologies Inc (U.S.A.)
V.A. Deason, Lockheed Martin Idaho Technologies Inc (U.S.A.)
Advances in optics over the last two decades have led to the development of optical processing mechanisms in photorefractive materials that provide unique capabilities for intelligent sensing applications. These capabilities include adaptability to environmental effects, image correlation, and optical computing. This paper describes the utilization of photorefractivity for performing noncontacting optical vibration detection that is most useful for small peak amplitudes less than the optical wavelength / 4*pi. Multi-wave mixing with synchronous detection allows measurement of both the vibration amplitude and phase of a vibrating surface directly as a function of the excitation frequency. Narrow bandwidth detection with flat frequency response can be achieved at frequencies above the photorefractive response (~100 Hz). A minimum detectable displacement amplitude of a few picometers has been demonstrated for a point measurement, with the possibility of further improvement. Full-field imaging of vibrating surfaces is performed in a manner that employs the adaptive properties of the photorefractive effect for real-time processing. The result is an output image intensity directly proportional to the vibration amplitude for small amplitudes, making this approach complimentary to other electronic speckle interferometry methods. An all optical vibration measurement technique is demonstrated by employing laser thermoelastic heating for excitation. Measurements of a vibrating stainless steel plate are presented showing the capabilities of the photorefractive approach for vibrational spectral analysis.
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D. Vaucher de la Croix, METRAVIB RDS (France)
D Webster, Pacific Noise and Vibration (Australia)
Bernard Garnier, METRAVIB RDS (France)
F. Molliex, METRAVIB RDS (France)
Aiming at a better understanding of noise measurements processing, the acoustical imaging software package "MALICE" permits a complete mapping of any tested unit. Indeed this analysis tool is connected to the appropriate measurement system and performs specific processing finally delivering a fine representation of the acoustic sources distribution (including a unique focusing capability).
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D. Vaucher de la Croix, METRAVIB RDS (France)
Bernard Garnier, METRAVIB RDS (France)
D Webster, Pacific Noise and Vibration (Australia)
F. Molliex, METRAVIB RDS (France)
Acoustic imaging techniques based on nearfield phased pressure or intensity mapping are now well known and provide a very explicit view of the localization of the predominant noise sources (hot spots)on any kind of surface (machinery casing, car body, engine block, vessel hull, etc.). Nevertheless, the constraint of sampling accurately and regularly the acoustic volume around the investigated object requires a very high order of sophistication; in most of the practical situations, it is not even physically feasible because of the presence of obstacles like pipes, ducts, surrounding equipment, insufficient clearance, for example. Normally, the imaging processing can be made only when a regular grid (generally a large rectangle per side of the object) sampled at perfectly constant intervals has been acquired under experimental conditions. METRAVIB RDS has developed the new SALSA toolbox to overcome this difficulty by introducing a much more flexible approach: I- the measurement is made from an hand-carried small array of microphones looking exactly like a ping-pong bat, - any accessible place is measured and the coordinates of two corners of the bat are memorized as they were for each measurement, - a 2-D or 3-D specific interpolation algorithm is then used to numerically remesh the measurements surface, and "extension" formulae are used to fill at best (i.e. as neutral as possible for the final processing) the eventual blanks. The final imaging process(of which the back propagation formalism is an essential element to neutralize the nearfield interferences and to image the noise sources precisely where they are) is made on the resulting fictive surface. Examples of applications will be provided such as the diagnosis of acoustic leakage of car door sound-proofing and gaskets in real industrial conditions. The application potential is by nature unlimited.
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Bernard Garnier, METRAVIB RDS (France)
F. Molliex, METRAVIB RDS (France)
D. Vaucher de la Croix, METRAVIB RDS (France)
D Webster, Pacific Noise and Vibration (Australia)
Using acoustic sensors for detecting, localizing and classifying noise sources of any kind - and in particular related to potentially adverse activities - is an already well established technique and applied in underwater activities. It now appears also as significant multiplier for airborne automatic detection and localizalion of warning sounds such as: blasts, gunshots or shouts in public buildings such as stadiums, big transportation infrastructures, greatand crowded events~VIP protection, etc, low altitude aircraft, helicopters, unmanned vehicles, etc. as a temporary or permanent protection of sensitive plants (energy production, telecommunications, military plants, etc.), desert borders, etc, snipers and other terrorist fire-arm actions against police forces, international peace corps, etc. artillery localization and aggressor identification in cease-fire international verification, etc. The peculiarities of low altitude sound propagation in air, the numerous echoes in urban and suburban environments, the high leveI of ambient noise, the variability of atmospheric conditions, make airborne acoustic detection and localization very challenging and specific compared to the Underwater sonar know-how. METRAVIB RDS and its Australian Subsidiary PNV have established an impressive record of experience and applications over the past four years providing to this presentation a real time flavour. The key features of airborne acoustic detection and Iocalization of transient sounds will be presented together wilh their practical technological embedded. Typical performance and intrinsic potential and limits of this technique will also be explored.
sv970290.pdf (Scanned) TOPAlois Heiss, Bavarian Ministry of Environmental Protection (Germany)
In case of necessary assessment of already existing noise sources like industrial plants, the separation of the interesting sound component from the residual environmental noise is a well known common task. A method is presented which uses an appropriate noise evaluation index Lx (percentile) for this purpose, for instance L50. As LX index values from measurement, like those of any other kind of evaluation index, have limited accuracy due to the ubiquitous stochastic level fluctuations, this uncertainty should be explicitly taken into account within the assessment procedure. For this reason a software suitable for laptop PC has been developed for real time measurement of the Lx confidence limits. By these datas, transferred into a further appropriate processing software, it is possible to present the final results of the sound separation, their related confidence limits and the resolution limit of the separation method. This new technique of quality control is demonstrated in the version for application to the noise assessment of continuously working plants like power stations etc., a some more sophisticated type of case than that of meresly switching on or off the interesting single sound source. An example of a field measurement and its result is presented.
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Jørgen Bække, Bruel and Kjaer A/S (Denmark)
Helge Larsen, Bruel and Kjaer A/S (Denmark)
Birger Kriegbaum, Bruel and Kjaer A/S (Denmark)
Bernard Ginn, Bruel and Kjaer A/S (Denmark)
For many years the measurement community has desired transducers with built in (integral) identification to ease the task of installation of instrumentation. This paper describes how a commercially available component has been adapted to fulfil this requirement. For the hardware to be considered as suitable, a certain number of requirements have to be fulfilled by the memory and the interface components employed e.g. ability to operate over two-wire, co-axial cable without disturbing the desired signal. Relative to the transducer itself, the integrated identification hardware must be small and lightweight, be low cost and have low power consumption. There should also be the possibility of two way communication over more than 100 m cable length. The two-wire interface demands are set by the standard coaxial-interface used for accelerometers with built-in constant current line drive (e.g. DeltaTron) amplifiers. Once the requirement for a co-axial interface has been fulfilled, its implementation in other transducers, where separate wires are available, poses no additional problems. Various well known solutions were examined and rejected, mainly because the necessary adjustment required for two-wire operation caused conflicts due to increased complexity, size and price. The suggested hardware solution is based on a Dallas Semiconductor component which communicates via a unique, two-wire interface called MicroLANTM.One of these components is an E2PROM, and with a little additional hardware this device fulfils requirements of the user. Examples of implementation are given: a single microphone and DeltaTron preamplifier unit in conjunction with a signal conditioning unit used to interrogate the transducer; a multichannel microphone array (over 100 channels) used with an IDA (Intelligent Data Acquisition) system where integrated transducer identification is used to reduced the configuration time considerably.
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