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Page 608 of 977 Results 6071 - 6080 of 9762

Y. Wen, M. Henry
CHARACTERISING CAVITATION NOISE BY WAVELET PACKET REPRESENTATION

Cavitation noise is comprised of burst waveforms resulting from the collapse of cavitating bubbles. Any burst is the mixture of impulses from individual bubbles collapsing in close proximity. A single bubble collapse contributes either to the duration or to the amplitude or to both in the actual mixed burst. Generally, as the severity of cavitation rises, both the amplitude and the duration of impulses in the bursts increase. In any practical system, the vibroacoustic signal of cavitation is blurred by unwanted noise. As the vibroacoustic burst of cavitation is time-frequency concentrated, the orthogonal wavelet packet bases are used to represent cavitation noise. The cavitation bursts are represented as the linear combination of the chosen wavelet packet bases. The wavelet packet coefficients describe cavitation in different frequency components and can discriminate individual bursts in raw data. Furthermore, the wavelet packet decomposition divides the signal into different frequency subbands. Thus the blurred noise can be treated as independently random variables in subbands and is suppressed by thresholding the coefficients.

Gr. S. Tymchik, Ò. R. Êlotchko
A LASER ANALYZER FOR DIAGNOSTICS CNC-MACHINE TOOL

The work states the progressive method and a laser intelligent analyzer of emergencies control of the technological equipment and processing materials. A laser analyzer of the acoustooptical interactions the optical and electrical on based. The multiparametrical spectrums’ analyse of the dynamical signals from the technological equipment allows to register of the current changes condition of the cutting tool and process in whole. This series of the optoelectronical analyzers with the CNC-machine tools are coordinated and its carries out automatic control of the breakage, the cutting tool wear, the moment of cutting tool jamming in the workpiece. This intelligent analyzers, functional algorithms and mathematical control models for the turning, milling and drilling technological automatic processing are created. The application of this laser control system allows to increase the productivity and the effiency of the automation precision processing materials.

W. Toczek, R. Zielonko
A MEASURING SYSTEM FOR FAULT DETECTION VIA OSCILLATION

A method and the test and measuring system for fault detection (FD) in electronic analog circuits, based on the modified oscillation-test approach, are presented. For FD purpose the circuit under test (CUT) is forced to oscillation, which parameters are monitored. Existing faults cause deviations of measured parameters, or result in the loss of oscillation. The novelty of presented approach are technique of converting higher-order circuits to oscillators by feedback structure assignment and the solution of test and measuring system with the automatic digital amplitude control. Microprocessor based system enables not only measurements of the oscillation frequency but also examination of variations in the amplitude step response parameters: rise time and steady-state error, that indicate faulty behaviour of the CUT. The increased quantity of diagnostic information results in the improved fault coverage in comparison with the method exploiting only frequency measurements.

M. Tabaszewski, C. Cempel
SIMPLE MODEL FOR FORECASTING IN TECHNICAL DIAGNOSTICS

The aim of this paper is to present possibility of application of some symptom models for prediction of machine condition. The models were obtained from energy processor (EP) which can describe general energy flaw and processing in machines.

N. Sönmez, M. Özgürler, C. Yaman
COMPARISON OF CUTTING CERAMICS WITH HARD METAL CUTTING TOOLS

Cutting ceramic tools are used especially at high cutting speeds in the machining process. The highly brittle type of structure and the tendency for cleavage (crack formation) are the infavorable properties of these materials, which keep their hardness at high temperatures. The hard metals are produced by sintering of the carbides such as whisker WC, TiC and TaC with the presence of Co as a binder. The high wearing resistance and high thermal strength characteristics of these materials are due to their high hardness values and due to the use of Co respectively. The main purpose of studies done in this field is generally to produce cutting tools bearing high hardness, strength and toughness properties at high temperatures of 1000 oC - 1100 oC. The cutting ceramics and hard metals are used in this study. The strength characteristics and behaviors and the related life times are studied depending on the cutting speeds. The comparison of the results and the feasibility for the economical purposes are investigated.

L. Swêdrowski
VIRTUAL INSTRUMENTS FOR ELECTRICAL MOTOR’S DIAGNOSTICS

The best results of electrical motor’s diagnoses are obtained using the methods based on spectral analysis of vibration signals or on analysis of supplying currents (in the case of electrical driving systems). The most numerous group of driving system breakdowns is connected with the damages of roll bearings. In this case very effective diagnosing can be obtained using envelope signal processing (ESP) technique. The research stand elaborated in the Faculty of Electrical and Control Engineering (TUG) enables to make research with ESP diagnostic method used for rolling elements bearings as well as supplying current analysis. The diagnostic system is based on virtual instruments using LabVIEW of National Instruments The stand is equipped in numerous motors with determined defects as well as the motors of the same type being in good condition, computer, specialized software built on the base of LabVIEW package. The results of measurement, as panels of virtual instruments, created in LabVIEW, are shown in the paper.

V. Sukackas, V. Giedraitiene, R. Ramanauskas
NONDESTRUCTIVE TESTING OF THE PIPE INNER CAVITY

A new method of the state of pipe inner cavity testing is described. It is based on the exciting of Lamb waves in the wall and analysis of the amplitude - frequency characteristic or transient response.

L. Jackowska–Strumillo, T. Jackowski, Wlodzimierz Kapczynski
COMPUTERISED SYSTEM FOR SPINNING PROCESS MONITORING

The paper presents a computerised multichannel system for monitoring of spinning processes in textile industry. The system operates ‘on-line’, directly on the rotor spinning machine without interrupting its work. Continuous measurements of three important spinning process parameters are taken, i.e., coefficient of mass variation of sliver, coefficient of mass variation of yarn, and yarn tension. Measurement data is stored in the computer so making further ‘off-line’ analysis and conversion possible. The modelled feed stream of fibres is used to generate the Multifrequency Binary Signal (MBS) as the input interrogating signal for the spinning process. The presented system offers a novel approach to dynamic measurements of yarn and sliver properties that can be useful in developing new spinning machines and technologies. System configuration and experimental results of the proposed process monitoring scheme are also presented in the paper.

A. Robotycki, R. Zielonko
PIECEWISE LINEAR CIRCUIT DIAGNOSIS BASED ON COMPONENT CONNECTION MODEL

The paper presents the method of fault location of the piecewise linear type analog circuits based on the verification approach and the component connection model. For verification of the fault hypothesis the residual square sum criterion is applied. In the first part of the paper the diagnostic equations describing the model and the algorithm of the method are presented. Theoretical considerations have been illustrated on the example of single and double fault diagnosis of the three-stage transistor amplifier.

A. Prateepasen, Y. H. J. Au, B. E. Jones
CALIBRATION OF AE FOR TOOL WEAR MONITORING

A calibration procedure using an air-jet as the artificial AE source was applied to single-point tool wear monitoring. The calibration procedure involves setting up an air-jet at a fixed stand-off distance from the top rake of the tool tip, applying in sequence a set of increasing pressures and measuring the corresponding AE. The root-mean-square value of the AE (AErms) obtained is linearly proportional to the pressure applied. This paper presents the results of machining tests and air-jet pressure test, both of which confirm that the tool system is linear with respect to AE propagation. Thus, irrespective of the layout of the sensor and AE source in a tool structure, AE can be expressed in terms of the common currency of ‘pressure’ using the calibration curve produced for that layout. Tool wear stages can then be defined in terms of ‘pressure’ levels.

Page 608 of 977 Results 6071 - 6080 of 9762