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Jianbo Zhang, Paul Regtien, Maarten Korsten
MONITORING OF DRY SLIDING WEAR USING FRACTAL ANALYSIS

Reliable online monitoring of wear remains a challenge to tribology research as well as to the industry. This paper presents a new method for monitoring of dry sliding wear using digital imaging and fractal analysis. Fractal values, namely fractal dimension and intercept, computed from the power spectrum of the images of a wearing surface, are adopted as indicators of the dynamic wear process. Experimental results show that progressive changes of fractal values might reveal the wear status of the surface.

Xavier Escaler, Carme Valero, Eduard Egusquiza
DIAGNOSTIC OF CAVITATION IN HYDRAULIC MACHINERY

An experimental investigation has been carried out to diagnose cavitation in actual hydraulic turbines from the analysis of structural vibrations and hydrodynamic pressures. The frequency content and the amplitude modulation of the signals have been studied in real Kaplan, Francis and Pump-turbine prototypes for detecting some types of cavitation like the leading edge cavitation and the draft tube swirl. The first type is erosive and the second one limits the stability of operation. The results found in the selected machines are presented. General conclusions have been obtained about the most adequate sensor, measuring location, signal processing and analysis for each type of cavitation.

Sohair Fakhry
PREVENTIVE, PREDICTIVE MAINTENANCE BY USING VISUAL DIAGNOSTIC METHODS

Preventive maintenance of equipment can easily be ignored by assuming that every thing is fine as long as the equipment is operating. Ignoring original equipment manufacturer (OEM) recommended maintenance schedules can create problems that are not apparent from just looking at the system.

Václav Matz, Marcel Kreidl, Radislav Šmíd
DETECTION AND VISUALIZATION OF FLAWS IN ULTRASONIC DEFECTOSCOPY

In ultrasonic defectoscopy it is very difficult to detect flaws in materials with coarse-grain structure. Measured ultrasonic signal contains echoes from flaw and echoes from grains included in material. These echoes characterized noise have to be cancelled. A common source of noise is electronic circuitry, which is used for processing of the ultrasonic signal, and scattering at the inhomogeneities in the structure of a grainy material. For reduction of noise efficient methods for suppression of noise have to be used. In this case the most efficient method for noise reduction is method based on discrete wavelet transform. This method gives the best results for filtering of ultrasonic signal in A-scan. In this work method based on neural networks for flaw detection in B-scan is used. Proposed methods are efficient used for separation of flaw from undesirable echoes. For visualization of flaw volume construction was created. The 3D volume visualization characterizes volumetric depiction of measured material. By using 3D volume visualization of ultrasonic signal it is possible to determine character and place of flaws in ultrasonic defectoscopy.

Gottfried Meltzer, Phong Dien Nguyen
AN INFORMATIV FORMAT FOR VISUAL PRESENTATION OF RESULTS IN GEAR DIAGNOSTICS

A visual observation of displayed measuring signals is an usual tool for an exact diagnosis of anomalities, which are detected by condition monitoring before. Interesting characteristics, which should be clearly recognized by diagnostics, are the kind of anomality causing fault, its extent and its situation. In the case of tooth gear diagnostics such kinds of faults as flank fatigue, flank wear, brooken tooth edges and cracked tooth roots are most frequent. Besides of them the number of affected stage, the damaged wheel and the number of faulted tooth are objects of fault localisation. On the others side the visualization of measured vibration signal is more difficult when the rotational speed of gear is insteady.
For making this activity more easy, some powerful algorithms are combined as follows:

  • synchronuous averaging of measured signal
  • calculation of residual signals (instead of overall signals)
  • time-frequency-distribution (continuous MORLET wavelet is preferred)
  • tuning of time resolution versus frequency resolution by choose of appropriate MORLET parameter
  • presentation in a polar coordinate system with rotational angle and order of rotational frequency as booth coordinates.
There is shown by examples, that all targets of gear diagnostics can be reached by visual presentation, using the recommended tools. As an additional advantages the high sensitivity of the mentioned algorithms is evident, which supports an early detection of faults.
A simple software, based on MATLAB®, will be finally explained .
Dieter Barschdorff, Cord Bauch
DIAGNOSTICS OF THE HUMAN CIRCULATORY SYSTEM: APPLICATION OF HIGH RESOLUTION BEAT-TO-BEAT BLOOD PRESSURE MEASUREMENT TO STRESS AND TRAFFIC SITUATIONS

When a person is exposed to physical and psychological challenge, the heart beat is increased, blood vessels are dilated, the blood pressure increases and the skin resistance decreases. While heart rate and skin resistance can easily be measured, continuous blood pressure measurement was not possible in stress situations because of the poor time resolution of oscillometric or Riva-Rocci/Korotkow based instruments. We apply a novel high resolution blood pressure measurement technique based upon the pulse transit time dependency on the systolic pressure and making use of individualized mathematical models. The method can be used without interfering with the persons cognitive perceptions. Thus we can present the first continuous blood pressure measurements during stress tests utilizing the Vienna Test System and the driving simulator "Nightdriver".

Dieter Barschdorff, Cord Bauch
DIAGNOSTICS OF THE HUMAN CIRCULATORY SYSTEM: HIGH RESOLUTION BEAT-TO-BEAT MEASUREMENT OF SYSTOLIC BLOOD PRESSURE USING PERSONALIZED MODELS

Blood pressure and heart rate monitoring allow evaluating the cardiovascular efficiency and point out how the circulatory system responds to stress and exercise. Especially the blood pressure indicates the ability of a person to withstand emotional and physical stress. For blood pressure measurement oscillometric or Riva-Rocci/Korotkow based instruments are used as standard devices. Their severe drawback is the low time resolution preventing the registration of dynamic cardiovascular changes. We present a new high resolution continuous blood pressure measure technique based on individualized mathematical models. The method can be applied without interfering with the subjects cognitive perceptions. Beside calibration tests we present the first continuous measurements during stress and traffic situations. Characteristic pros and cons of the new method, the accuracy and new diagnostic possibilities are discussed.

István Szatmári, Ákos Zarándy
HIGH-SPEED LABEL INSPECTION SYSTEM FOR TEXTILE INDUSTRY

In this paper, the current development of a high-speed, visual inspection unit for use in the quality assurance of narrow fabric and label weaving will be presented. The aim of the project is to provide full visual defect recognition for the textile industry. Dirt spots and patches, weaving faults, missing or torn fibers, and certain errors of the label patterns are detected. A special experimental setup was prepared for evaluating the algorithm performance. Current phase achieves a very high quality level with low false alarm rate at inspection speed of 4 m/s.

Jirí Vass, Cristina Cristalli
BEARING FAULT DETECTION FOR ON-LINE QUALITY CONTROL OF ELECTRIC MOTORS

This paper is concerned with analysis and classification of vibration signals from universal electric motors. The goal is to reveal manufacturing defects caused by assembly machines composing the motors on a production line. Such machines may under certain conditions use inappropriate force, and hence cause a mechanical shock, resulting in a damage of the motor bearings. The proposed system comprises a preprocessor based on continuous wavelet transform in order to reduce the noise masking the characteristic frequencies of bearing faults. The noise reduction is based on the adaptive Morlet wavelet and soft-thresholding of wavelet coefficients. Individual blocks of the preprocessor are presented and important practical issues are considered, such as segmentation and proper selection of wavelet scales. Identification of defective motors is performed by a simple and effective technique based on autocorrelation function, utilizing prior information on vibration frequency features. Finally, two error measures are designed in order to evaluate influence of a simulated noise level on efficiency of the fault diagnosis system. Achieved results appear to be promising and applicable in automatic quality control.

R. Schmitt, T. Pfeifer, P. Hafner, B. Dietrich
MACHINE VISION AND ULTRASONIC SUPPORTED MEASURING AND MONITORING CONCEPT FOR ECONOMICAL QUALITY ENHANCEMENT IN SMALL BATCH PRODUCTION

In order to handle production processes and product quality in small batch production, flexible measuring and inspection systems, which can be automated, are required. The integration of such systems into machine tools represents a profitable approach. The general advantages of inline measuring systems are described in this contribution. Subsequently the article demonstrates two exemplary applications in the areas of geometry inspection and material testing. Therefore an image-processing-based machine vision system and an changeable ultrasonic sensor are employed.

Page 478 of 977 Results 4771 - 4780 of 9762