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[en] The challenge is here to inspect a set of two or three parallel and immersed plates using leaky Lamb waves. The first plate(s) acts like a screen to be going through. The Energy Based Model (EBM) that has been validated in previous work is used here to study the forward propagation and the backward propagation after reflection on a defect. We found that it is possible to inspect a set of three parallel plates 7.8 mm thick and a set of two parallel plates 20 mm thick with pulse/echo configuration. Moreover, EBM predictions are in good agreement with in water experimentation results. (authors)
[en] Remote visual inspection (RVI) is critical for the inspection of the interior condition of pipelines particularly in the nuclear and oil and gas industries. Conventional RVI equipment produces a video which is analysed online by a trained inspector employing expert knowledge. Due to the potentially disorientating nature of the footage, this is a time intensive and difficult activity. In this paper a new probe for such visual inspections is presented. The device employs a catadioptric lens coupled with feature based structure from motion to create a 3D model of the interior surface of a pipeline. Reliance upon the availability of image features is mitigated through orientation and distance estimates from an inertial measurement unit and encoder respectively. Such a model affords a global view of the data thus permitting a greater appreciation of the nature and extent of defects. Furthermore, the technique estimates the 3D position and orientation of the probe thus providing information to direct remedial action. Results are presented for both synthetic and real pipe sections. The former enables the accuracy of the generated model to be assessed while the latter demonstrates the efficacy of the technique in a practice
[en] For techniques that use propagating electromagnetic (EM) waves, there are three modes for wave transmission from the source to the receiver: direct, reflected and lateral (or surface) waves. A useful characteristic of lateral waves is that they propagate along the boundary between two different materials with the interaction being confined to the boundary region. In this work, the use of lateral waves for remote and noncontacting sensing is considered with an emphasis on characterization of metallic surfaces
[en] Mechanical rebar couplers are preferable in the advanced building construction and structural design of anti-seismic elements. The paper presents destructive inspection techniques used to investigate stress fields (tensile and compressive) and deformation curves for mechanical rebar splicing. The properties of mechanical rebar splicing are investigated by the non-destructive testing digital radiography. The behavior of real connections (column-to-column, beam-to-column) is studied under static and dynamic loads. Investigation results allow the elaboration of recommendations on their application in the universal prefabricated anti-seismic structural system developed at Tomsk State University of Architecture and Building, Tomsk, Russia
[en] This paper presents an overview of alternative methods of production of enhanced performance Al-based alloys components for critical areas. In particular, a new rheocasting system, suitable for the manufacturing of high performance industrial components has been considered. The aforementioned method allows obtaining component quickly and results a more convenient process, from economical point of view than other innovative processes. Two series of components have been produced with A356 and A357 alloys, then have been heat treated using T5 and T6 treatments. On polished transverse sections of samples the microstructure of the alloy has been observed. Their soundness has been previously certified by non destructive tests. Samples for tensile and three point bending tests have been machined directly from the produced components. On the fractured samples, fracture surface analysis has been performed in order to analyze and evaluate the influence of the process and of the alloy on the fracture behaviour.
[en] The automated defect classification algorithm based on artificial neural network with multilayer backpropagation structure was utilized. The selected features of flaws were used as input data. In order to train the neural network it is necessary to prepare learning data which is representative database of defects. Database preparation requires the following steps: image acquisition and pre-processing, image enhancement, defect detection and feature extraction. The real digital radiographs of welded parts of a ship were used for this purpose.
[en] By now the subsonic mode of collision is studied in detail. In the supersonic mode, when shock waves arrive to the contact point, jet formation is impossible. It is assumed that perturbation growth at metal interfaces is also impossible. It is obtained in our experiments that perturbations are formed in the mode of supersonic jetless oblique collision at the metals interface. Numerical calculations with use of the two-dimensional Lagrange technique showed presence of an area with large gradient of velocity and high intensity of strains near the contact point
[en] Despite the strongly dispersive nature of guided wave propagation in isotropic planar waveguides, it is shown that material non-linearity can result in the generation of propagating harmonics at points in the guided wave spectrum where the dispersion curves of all three orthogonal modes intersect. Experimental measurements of linear and harmonic guided wave propagation in rolled aluminum sheets have been explained in terms of the existence of a low symmetry microstructural texture in the materials
[en] We have used Process Compensated Resonant Testing (PCRT) for studying structural integrity and functional performance of ceramic balls used in various auxiliary power units (APUs), propulsion engines, and defense and space missiles. The results show that PCRT is successful in sorting acceptable parts from parts with defects such as micro-structural changes, C-cracks, and scuffs. However, PCRT suffers from limitations, generally not determining the type, size or location of the anomaly. The pursuit of improvements to PCRT is an on-going process.