Diagnostics of Structures by the Methods of Electron Shearography and Speckle-Interferometry
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DIAGNOSTICS OF STRUCTURES BY THE METHODS OF ELECTRON SHEAROGRAPHY AND SPECKLE-INTERFEROMETRY L. M. Lobanov1 and V. A. Pivtorak1, 2
UDC 620.179.1
A procedure aimed at nondestructive quality testing and determination of the residual stresses in welded structures is developed on the basis of the methods of electron shearography and speckle-interferometry. We create compact shearographic and speckle interferometric measuring systems capable of the investigation of welded structures under the conditions of their manufacturing and operation and present the results of diagnostics of the quality and stress states of the elements of welded panels made of VT-20 high-strength titanium alloy and the technology used for the evaluation of the diameter of weld-spot nugget. Keywords: electron speckle-interferometry, shearography, nondestructive testing, residual stresses, computer processing.
The development of leading branches of the modern industry and the use of new materials are closely connected with the solution of the problems of enhancement of the reliability and durability of structures. These problems are especially urgent in connection with the fact that a great number of structures, buildings, and equipment have already exhausted the designed terms of their operation. For the solution of these problems, it is necessary to use the efficient methods of nondestructive quality testing and engineering diagnostics capable of the operative accumulation of up-to-date reliable information about the engineering state and service life of objects operating for long periods of time. It is worth noting that the methods of laser interferometry allowing one to perform the diagnostics of structures made of various structural materials are now extensively developed. These methods include optical holography, electron speckle-interferometry, shearography, and speckle-correlation. Electron shearography is a coherent optical method used for the investigation of structures and capable of the contactless examination of the surfaces of objects with the help of simple optical devices without damaging these surfaces. This method is used for the investigation of various materials and structures and enables one to measure the deformation of the object under loading. This explains the insensitivity of electron shearography to rigid displacements of the object under the influence of the medium and determines its universality and efficiency [1, 2]. As an important advantage of electron shearography (used as a method for the nondestructive testing of the quality of objects), we can mention the fact that, unlike the traditional methods which only detect the presence or the absence of defects, it allows one to determine concentration of stresses caused by the defect and the structural specific features of the object. For the nondestructive testing of the quality of structures, we used a compact shearographic installation including a semiconductor laser, a CCD-camera, and a shearomodule. 1 2
Paton Institute of Electric Welding, Ukrainian Academy of Sci
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