Fatigue crack in rails and cyclic-loaded train parts is a contributory factor in multiple railroad accidents. We address the problem of crack detection and measurement at early stages, when total failure has not yet occurred. We propose to combine acoustic emission (AE) testing for prediction of crack growth with digital image correlation (DIC) for its accurate quantitative characterization. In this study, we imitated fatigue crack appearance and growth in samples of railway rail and two train parts by cyclic loading, and applied these two techniques for inspection. Experimental results clearly indicate the efficiency of AE in the early detection of fatigue cracks, and excellent DIC capabilities in terms of geometrical measurements. Combination of these techniques reveals a promising basis for real-time and non-destructive monitoring of rails and train parts.
Fiducial markers are used in vision systems to determine the position of objects in space, reconstruct movement and create augmented reality. Despite the abundance of work on analysis of the accuracy of the estimation of the fiducial markers spatial position, this question remains open. In this paper, we propose the computer modeling of images with ArUco markers for this purpose. The paper presents a modeling algorithm, which was implemented in the form of software based on the OpenCV library. Algorithm is based on projection of three-dimensional points of the marker corners into two-dimensional points using the camera parameters and rendering the marker image in the new two-dimensional coordinates on the modeled image with the use of the perspective transformation obtained from these points. A number of dependencies were obtained by which it is possible to evaluate the error in determining the position depending on markers size. Including the probability of detecting a marker depending on its area on an image.
Optical methods for deformations diagnostic and surface shape measurement are widely used in scientific research and industry. Most of these methods are based on triangulating a set of two-dimensional points in the images appropriate to the same three-dimensional points of the object in space. Various algorithms to search such points are applied. The possibility of using cross-correlation processing of digital images to search these points is considered in the work. Algorithms based on the correlation function calculation are widely employed in such a popular flow diagnostic method as PIV. The cameras of a stereo system for surface shape measurement can be widely spaced, and the tilt angles relative to the surface can differ significantly. This leads to the fact that the images taken from the cameras cannot be directly processed by the correlation function because it is not invariant to rotation. To solve this problem, fiducial markers are used to find an initial estimate of displacement of the images relative to each other. This approach makes it possible to successfully apply correlation processing for stereo system images with a large stereo base.
The future robotic and human lunar landing missions to the Moon has many factors which turn them into difficult technology and science tasks. One of these factors is the influence of the dust. Upper layers of the regolith are an insulator. The regolith exposed to permanent bombardment by micrometeorites and acquire a charge due to solar wind fluxes and solar UV radiation. These factors create a charge distribution on the surface of the Moon: positive on the illuminated side and negative on the night side. On the day side of the Moon near the surface layer exists possibility of formation an electric field. Charged dust particles of micron and submicron sizes can take off and levitate over the surface. The aim of the work is to get visualization of the dynamic of dust particles under a charged surface with simultaneously estimating its parameters as accurately as possible. The experimental setup based on vacuum chamber for physical modelling of dusty plasma levitation is described. For visualization of the dust particles trajectory a stereo system of two cameras with a laser as source of illumination is used. Image processing techniques for estimating the particle trajectory in three dimensional coordinates and examples of processing results are presented.
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