Naslov
Optical method of caustics - fulfilled experimental application to the contact

Autori
Semenski, Damir

Vrsta, podvrsta i kategorija rada
Radovi u zbornicima skupova, cjeloviti rad (in extenso), znanstveni

Izvornik
Proceedings of XVII IMEKO World Congress Metrology in the 3rd Millenium / Ilić, D. ; Boršić, M. ; Butorac, J - Zagreb : Hrvatsko mjeriteljsko društvo, 2003, 1952-1955

Skup
XVII IMEKO World Congress Metrology in the 3rd Millenium

Mjesto i datum
Dubrovnik, Hrvatska, 22.06.2003. - 27.06.2003

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
experimentalna mehanika; optička metoda kaustike; kontaktna sila
(experimental mechanics; optical method of caustics; contact force)

Sažetak
The great number of numerical and experimental techniques in damage and fracture mechanics is employed for determining the stress intensity factors (SIF) of the cracks in deformed structures. Experimental optical method of caustics is established for the application to mechanically isotropic materials, through the process of SIF&#8217 ; ; ; s evaluation reduced to the epicycloidal dark spot measuring. The reflection method of caustics is advantageously improved for the application to nontransparent mechanically anisotropic materials such as fiber-reinforced composites. The analysis of the contact between two elastic bodies introduces the procedure of force determination by the method of caustics. As in contact problems the amount of the applied force as well as its inclination (e.g. in the case of friction normal and tangential component of the force) can be identified and measured from the optical effect (dark spot) on the screen. The theoretical basis and complete procedure of force determination is developed and simulated for typical cases of loading conditions. Singular caustic curves are of the same shape for the same angle of force inclination, while its size is in direct connection to force intensity. The measuring procedure was established when the experimental optical effects taken and processed in laboratory conditions were compared to the simulated ones for different force inclination and for different types of body contact. Measuring equipment consisted of a high energy point light source, a system of lenses, a b/w CCD camera with AD converter and a computer, set up for transparent optical arrangement. Images were digitized and automatically analyzed by previously preprogrammed system filters for effective dark spot extraction and quantification. Experiments were performed under the static loading conditions by increasing the load intensity for different types of photoelastic material araldite B of thickness ranging between 3mm and 6mm. Experimentally determined force and simultaneously measured intensity and the angle of applied force are compared showing the maximum difference of 3%. Objectives of the research in future are the development of more sophisticated procedures that will enable the evaluation of the contact force and the extension of application of the method of caustics to mechanically anisotropic materials. The expectations are that the shape of caustic curves will be different for different mechanical structure, while the size of caustics will be proportional to the force intensity. The analysis is presumed to be established by the evaluation of the experimental optical effects performing the simulation of each situation separately.

Izvorni jezik
Engleski

Znanstvena područja
Strojarstvo

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