THE CONSTRUCTIVE METHOD FOR CALCULATING OF FRAUNHOFER'S DIFFRACTION PICTURES AND IMAGES OF 3D-OBJECT REFLECTIVE VOLUMETRIC EDGE

In analytical form, the peculiarities of forming Fraunhofer diffraction patterns and images of faces of a volumetric asymmetric edge of an object with an absolutely reflective internal surface in relation to dimensional inspection were investigated. Formulas were obtained for calculating fields in diffraction-limited systems depending on the magnitude of the bevel of the object c , the phase shift j of the wave reflected from the inner surface of the object, and the angular aperture of the coherent optical system for forming and filtering images. It has been established that for metal 3D-objects (j = p), the value of the field in the image of the back face at a point, corresponding to the position of its border is negligible with the depth of focus of the system much less than the thickness of the object. It is shown that when bevels of an object, much less than the size of the Fresnel zone d ~ ( l - wavelength of light, d - thickness of the object) and more than the depth of focus, the displacement of the intensity profile in the image of the front face is proportional and depends on the angle j. With large bevels, when and, the displacement of the front face boundary is inversely proportional to the value. These displacements can lead to systematic errors in measuring the position of the boundaries of the faces of a 3D-object and should be taken into account in precision dimensional inspection.

APPLICATION OF DIFFRACTIVE OPTICAL ELEMENTS FOR OPTICAL-ELECTRONIC DIMENSIONAL INSPECTION SYSTEMS

The work is devoted to the application of diffractive optical elements in systems using the structured illumination method to the geometric parameters inspection of industrial articles. The objects of inspection in these systems are: weapon barrels, fuel pellets, fuel elements, spacer grids, ceramic ring insulators. The used diffractive optical elements are computer-synthesized holograms that focus laser radiation into geometric shapes, the configuration of which is optimally combined with the inspected objects shape.

Precision analysis model and experimentation of vision reconstruction with two cameras and 3D orientation reference

Active vision reconstruction is widely used in industrial manufacturing and three-dimensional inspection. The reconstruction accuracy is an important problem to be investigated for the inspection process. The paper conducts an analysis study of the reconstruction error for the vision reconstruction with a planar laser, two cameras and a 3D orientation board. The variation principles of the spatial coordinates caused by the variations of the extrinsic parameters of the cameras, intrinsic parameters of the internal camera, and image coordinate points of the internal camera, are modeled and analyzed in this paper. The analysis is also proved by the verification experiments, which provides the application potential for other active-vision-based reconstructions.

ACOUSTIC EMISSION TESTING OF FIBERGLASS PIPES AND FITTINGS

Experimental studies was carried out. The purpose was to develop a method to test fiberglass pipelines in operating mode. The acoustic emission method was chosen as the main method of nondestructive testing, and visual and dimensional inspection was chosen as an additional method. Acoustic parameters and acoustic emission properties of fiberglass pipes were determined. It was found that acoustic emission sensors can be installed at distances of up to 9-18 m from each other. A series of loading tests was carried out to refine the methodology. Every loading case was performed until leakage registration. In most cases, leakage occurred near the fillet at pressures of 2.2…3.0 from the working pressure, which indicates a large margin of safety for fiberglass pipes. It is confirmed that the acoustic emission method allows early defect detection. Based on the acoustic emission data, 4 main stages of fiberglass pipes degradation were identified. Visual and dimensional inspection was informative only at stages III – IV. Stage IV in most cases corresponds to the leakage. Even early stage of depressurization was registered as continuous acoustic emission. Signals with amplitudes exceeding 60…80 dB were registered at all loading stages. The location map became informative after filtering events by acoustic emission parameters. A methodology for the testing of fiberglass pipes and fittings in operating mode was developed. It contains, in contrast to the currently valid standards, specific numerical values of various quantities related to both the preparation and carrying out of acoustic emission testing and the classification of the identified sources of acoustic emission according to the degree of danger and allows to evaluate the residual life of fiberglass pipelines. The most informative parameter was the activity of acoustic emission; therefore, it is recommended to carry out loading without holding the pressure. It is planned to carry out additional experiments to clarify the mechanisms of fracture acting at each of the 4 identified stages of degradation.

Welding procedure research of titanium heat exchangers

In order to manufacture Gr.1 titanium heat exchangers, the welding property and weld structure of titanium tube-to-tubesheet are analyzed. The procedure of Pulse GTAW is used and the visual inspection, dimensional inspection, chemical composition, mechanical properties and metallographic structures are tested and analyzed. The results show that the weld joint can get ideal structure and good chemical composition, mechanical properties and corrosion resistance. The successful welding qualification has accumulated valuable experience for manufacture of titanium heat exchangers.

VOLUMETRIC EFFECTS FOR IMAGE FORMATION OF 3D ASYMMETRIC EDGE

The peculiarities for formation of the image of volumetric asymmetric absolutely absorbing edge (the main fragment of constant thickness thick plates) in a diffraction-limited projection system are investigated in analytical form applied to 3D-objects dimensional inspection. Structures and profiles of image intensities for front and back object sides are studied respectively at small and big apertures of the 3D-object optical system for various ratios of object bevel c , the Fresnel zone size d ~ ( l - the light wavelength, d - object thickness) and an angular aperture of the optical system. It is shown that in case when the bevel с << d , the shift of intensity profile of the 3D-edge image, proportional to Fresnel's zone and bevel size, takes place. Formulas for the image profile of the back side are obtained and investigated in case of strong volumetric effects, when the focus-row depth of the system is much less than the object thickness. The obtained results are in good agreement with results of computer simulations.