Nicola Paone

The laser doppler vibrometer as an instrument for nonintrusive diagnostic of works of art: Application to fresco paintings

Abstract The purpose of this paper is to present the application of the Laser Doppler Vibrometer as a nonintrusive measurement instrument to detect shape and location of damage in fresco paintings. The paper discusses performance of the measurement instrument and outlines a measurement procedure capable of nonintrusive diagnostic of the state of conservation of works of art, based on frequency response analysis of wall surface vibration induced by acoustic excitation. The procedure for the measurement of wall surface vibration is described. A 2D map of surface vibration amplitude is produced by scanning the measurement point across the surface. This pseudo-image is then processed by image analysis techniques to determine the position and the shape of damaged areas. Experiments are performed on an artificial fresco with induced damage and on a real painting inside a church.

Non-invasive measurements of damage of frescoes paintings and icon by Laser Scanning Vibrometer: experimental results on artificial samples and real works of art.

Abstract Frescoes and icons show analogies in terms of defects, both present layer-to-layer detachments and delaminations and surface cracks; the aim of this work is to develop a diagnostic system for the measurement of the defects’ position and size. After initial measurement set-ups based on accelerometers and impact hammers a novel system based on laser vibrometers and acoustic stimulation of structures to allow full remote and contactless investigation of detachments and delaminations has been developed. This paper presents a measurement procedure based on two subsequent scans of the work of art: the first scan aims at finding the defects’ positions, the second one characterizes their resonant response. A new kind of exciter, namely piezo actuators, has been introduced in the measurement chain and its effectiveness in finding defects in icons will be demonstrated. In situ measurements on real frescoes have been performed in Senigallia (near Ancona) and Orvieto to assess the proposed technique and a sample of the obtained results will be presented.

Fault detection for quality control of household appliances by non-invasive laser Doppler technique and likelihood classifier

This paper addresses the problem of developing an on-line diagnostic system for mechanical quality control of household appliances. The selection of a suitable measurement technique for feature extraction is discussed; the choice of a laser Doppler vibrometer technique and a laboratory measurement station for washing machines is presented. Vibration velocity and displacement are measured over a grid of points on the machine surface and data are stored in a database suitable for processing, both with good appliances and with defect ones with known defects. Features from the vibration velocity spectrum are used as the input to a likelihood classifier, which is shown to achieve very good classification scores.

Carotid artery pulse wave measured by a laser vibrometer

Early diagnosis of occlusive arterial diseases demands a device which sensitivity is able to resolve small differences between normal and abnormal pressure and flow pulse patterns. The present paper reports the use of a laser doppler vibrometer (LDV) in preliminary test for registration the pressure pulse. The measurements were performed in the right carotid artery of four volunteers to observe presumed typical pressure pulse patterns. LDV was used in single point mode to obtain the pressure waves in two distinct physiological situations: breathing and in apnea.

New applications of Scanning Laser Doppler Vibrometry (SLDV) to non-destructive diagnostics of artworks: mosaics, ceramics, inlaid wood and easel painting

Abstract There exist many analytical methodologies and techniques to individuate the physical and chemical characteristics of artworks, but at present, their structural diagnostics mainly rely on the expertise of the restorer and the typical diagnostic process is accomplished mainly through manual and visual inspection of the object surface 〚1〛 . The basic idea behind the proposed technique is to substitute human senses with measurement instruments: surfaces are very slightly vibrated by mechanical actuators, while a laser Doppler vibrometer scans the objects measuring surface velocity and producing velocity amplitude and phase two-dimensional (2D) or 3D maps. Where a defect occurs velocity is higher than neighbouring areas, so defects can be easily spotted. Laser vibrometers also identify structural resonance frequencies thus leading to a complete characterisation of defects. This work will present the most recent results coming out of the application of scanning laser Doppler vibrometry (SLDV) to different types of artworks: mosaics, ceramics, inlaid wood and easel painting. Real artworks and samples realised on purpose have been studied using the proposed technique and different measuring issues resulting from each artwork category will be described.

Towards the integration of process and quality control using multi-agent technology

The paper introduces a vision on the design of distributed manufacturing control systems using the multi-agent principles to enhance the integration of the production and quality control processes. It is highlighted how agent technology may enforce interaction of manufacturing execution system and distributed control system, enhancing the exploitation of the available information at the quality control and process control levels. A specific focus is made on a suitable engineering methodology for the design and realization of such concept. Innovation is also presented at the level of adaptive process control and self-optimizing quality control, with examples related to a home appliance production line.

On field validation of non-invasive laser scanning vibrometer measurement of damaged frescoes: experiments on large walls artificially aged

Abstract Past experiences demonstrated that the study of surface vibrations could be used to locate defect positions and sizes in frescoes. At present a non-invasive diagnostic system is under development and the aim of this work is to present the results obtained on large painted walls. After initial measurement set-ups based on accelerometers and impact hammers, a novel system based on laser vibrometers and acoustic stimulation was assembled. Full remote and contactless investigation of typical defects of frescoes, detachments, cracks and delaminations is thus possible with a very high accuracy. For the present investigation we employed a commercial scanning laser doppler vibrometer (SLDV) system, a horn loudspeaker and bass reflex enclosure to fully cover the audio frequency range. This paper will present experimental results gathered from large samples made by LRMH and compare them with those extracted by traditional investigation techniques.

A New Method for the Experimental Assessment of Finger Haemodynamic Effects Induced by a Hydraulic Breaker in Operative Conditions

A New Method for the Experimental Assessment of Finger Haemodynamic Effects Induced by a Hydraulic Breaker in Operative Conditions: Matteo Valentino, et al. Clinic of Occupational Medicine, University of Ancona, Italy—The haemodynamic effects, in terms of grip force and hand‐transmitted accelerations, produced on the fingers of 10 healthy subjects by operation of a hydraulic breaker held with a low or a high grip were investigated with a new experimental set‐up. A novel apparatus consisting of a capacitive sensor matrix and a laser Doppler vibrometer was used to measure the two parameters during breaker operation. Finger blood flow in basal conditions and after each test was evaluated in the four long fingers of both hands with a photoplethysmograph and superficial skin thermometry. The amplitude of the accelerations transmitted to the hand surface was greater during the test with the low grip. Photoplethysmographic and thermometric values were significantly lower than basal values after either test. The amplitude of photoplethysmographic values during the tests was significantly lower with the low than with the high grip in 6 subjects, in both index fingers, and in the right middle finger. The authors show that the level of grip force used for holding the breaker causes transmission of vibrations of wider amplitude, resulting in greater reduction in finger blood flow. In line with the literature, stimulus magnitude, frequency and duration affected finger blood flow, especially in the index finger.

PHOTOELASTICITY FOR THE INVESTIGATION OF INTERNAL STRESS IN BGO SCINTILLATING CRYSTALS

Abstract Quality control of scintillating crystals production requires the on-line monitoring of the state of internal stress levels. The determination of the photoelastic constant in crystals is fundamental in this measurement, rendered necessary by the crystal fragility, a limiting factor in the construction of calorimeters (radiation detectors consisting in large arrays of crystals). In this work high-density BGO (Bismuth Germanate Bi3Ge4O12) crystals for calorimeters have been studied by means of photoelasticity. A test bench, based on a circular polariscope, an image acquisition system, a data processing unit and a suitable mechanical loading unit have been developed and applied to crystal sample testing. The results provide new data on photoelasticity of BGO and outline the basic features for the construction of an apparatus for on-line inspection of crystal quality.

Design and experimental characterization of a nonintrusive measurement system of rotating blade vibration

A measurement system for nonintrusive monitoring of rotating blade vibration in turbomachines based on fiber optic sensors is presented. The design of the whole system is discussed; the development of special purpose sensors, their interfacing to the data acquisition system, and the signal processing are outlined.The processing algorithms are tested by software simulation for several possible blade vibrations. Experimental tests performed on different bladed rotors are presented. Results are compared to simultaneous strain gage measurements.