Flaw Detection in Highly Scattering Materials Using a Simple Ultrasonic Sensor Employing Adaptive Template Matching

Ultrasonic sensors have been extensively used in the nondestructive testing of materials for flaw detection. For polycrystalline materials, however, due to the scattering nature of the material, which results in strong grain noise and attenuation of the ultrasonic signal, accurate detection of flaws is particularly difficult. In this paper, a novel flaw-detection method using a simple ultrasonic sensor is proposed by exploiting time-frequency features of an ultrasonic signal. Since grain scattering mostly happens in the Rayleigh scattering region, it is possible to separate grain-scattered noise from flaw echoes in the frequency domain employing their spectral difference. We start with the spectral modeling of grain noise and flaw echo, and how the two spectra evolve with time is established. Then, a time-adaptive spectrum model for flaw echo is proposed, which serves as a template for the flaw-detection procedure. Next, a specially designed similarity measure is proposed, based on which the similarity between the template spectrum and the spectrum of the signal at each time point is evaluated sequentially, producing a series of matching coefficients termed moving window spectrum similarity (MWSS). The time-delay information of flaws is directly indicated by the peaks of MWSSs. Finally, the performance of the proposed method is validated by both simulated and experimental signals, showing satisfactory accuracy and efficiency.

Flaw detection of ship equipment parts

The need for non-destructive testing is regulated by the rules of the Russian River Register, which can determine the choice of the method of non-destructive testing and the procedure for its implementation. Non-destructive testing methods used in naval mechanical engineering are: visual and measuring control, ultrasonic control, radiographic control, capillary control, magnetic control, eddy current control. Each of the methods, due to the difference in the implemented physical principles, has its own advantages and disadvantages, which impose restrictions on the flaw detection of parts. The analysis of the sculpted defects of ship equipment and machines, depending on the manufacturing method and operating conditions, was carried out. The limitations on the use of non-destructive testing methods are shown. Examples of non-flaw detective parts are given, the control of which is difficult, as well as flaw detective parts that can be controlled with a guaranteed condition for detecting defects. The advantage of the method of magnetic memory of metal is indicated, relative to other methods of non-destructive testing. Using the example of a piston pin of a marine diesel engine NVD 36, a comparative analysis of the applicability of ultrasonic testing methods, the magnetic memory method and the penetrating solutions method for detecting fatigue cracks was performed. The results of the control show that the applied methods confidently identify fatigue cracks in the controlled parts, machines and mechanisms of ship equipment.

RESEARCH OF CONCRETE OF REINFORCED CONCRETE SLEEPERS, WHICH DECIDED DAMAGE DURING OPERATION

Purpose. On the railways of Ukraine in some areas there is an intensive premature exit sleepers due to the formation of defects that can affect the safety of trains and cause significant material losses due to a single replacement of a significant number of sleepers. The purpose of the study is to establish the causes of damage reinforced concrete sleepers on a characteristic section of the railway with their intense premature exit. Methodology. The condition of reinforced concrete sleepers of SB3 type under unlined substrate fastenings on 324-332 km of the pair track of the Odnorobivka-Bukine section of the Southern Railway was studied, where since 2007 their intensive output was observed due to defects. Findings. It is established that for 15 years of operation, as 236.3 million tons were put into operation, about 2.8 % of sleepers were replaced due to defects (44 pieces per 1 km of track). Typical defects (damages), due to which the sleepers were removed from the track, were mainly 13.2 and 13.2 according to the classification of CP-0150 – cracks and fractures of sleepers, including ones with crushing concrete. These defects were preceded by the formation of a network of thin cracks on the visible surfaces of sleepers. 3 sleepers with an initial compressive strength of 68…77 MPa produced by the Korosten Reinforced Concrete Sleeper Plant and the Gnivan Special Reinforced Concrete Plant, removed from the track due to characteristic defects, were selected and investigated. Samples were selected from the sleepers, with the help of which there was determined the final strength of concrete and microscopic examinations, including luminescence flaw detection method, were performed. It was found that the network of cracks in sleepers is spatial, mostly developed mostly beneath their top edge, the least developed above the bottom edge, and causes a decrease in compressive strength of concrete by 47…72 %. It is noted that the destruction of concrete during loading occurred behind these cracks. On the inner surfaces of the cracks there are individual grains of aggregates, which have signs of active silica content, that together with the nature of the cracks may indicate that the cause of their formation is corrosion of concrete from the interaction of cement alkali with reactive aggregates. On the surfaces of the cracks in the lower part of the sleepers leaching products were found, apparently leached by electro migration, which may indicate that corrosion processes were promoted by leakage currents on electrified DC tracks. Originality Thus, in the study area, the main cause of defects, which caused the replacement of the sleepers – was the corrosion of concrete due to the interaction of cement alkali with reactive aggregates, promoted by leakage currents, as well as a small diagram of sleepers and the use of unlined anchor intermediate rail fasteners. Practical value. The results of the study allow to establish the causes of cracks and other damage in reinforced concrete sleepers during operation and, in turn, reduce the losses of fasteners manufacturers and sleepers from defects and complaints, optimize the total cost of track repairs and subsequent track maintenance due to rational purpose of track construction, reduction of damage and replacement of sleepers during track operation.

Flaw detection of tubural refractory products by the method of thermal testing

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Experience in the application of the non-destructive method of acoustic emission in the production of titanium billets and products of transport engineering

The article discusses the issue of using the non-destructive method of acoustic emission at the stage of blank production. So, due to the violation of the heat treatment modes, various defects are formed in the starting material, which affects the operational properties of the finished products. To eliminate this problem, the stages of production of titanium blanks and products of transport engineering were studied, such as: heat and mechanical treatment, ultrasonic quality control, determination of the level of mechanical properties and control of the structure. In the course of the research, a method of acoustic emission control was developed and tested. The experiment on setting the locations of defects was carried out on ingots of VT22 titanium alloy during cooling. The reliability of the developed method is confirmed by the existing method of ultrasonic flaw detection. It has been established that this method can be effectively used to control workpieces and machined workpieces for the manufacture of particularly critical mirrors for searching for inhomogeneous inclusions and increasing the efficiency of the technological process by eliminating machining of VT1-0 titanium surfaces with inhomogeneous inclusions. In addition, this method can be used to search for defects commensurate with the grain size of the ingot, as well as significantly smaller sizes.

Results of flaw detection of parts of the «shaft - pinion bushing» connection of agricultural machinery reducers

The article has devoted to solving an urgent problem related to the fault detection of the main parts of gearboxes. A study of the dimensions of new and worn parts, forming the connection «shaft - pinion bushing» Ø4ON7/k6 in the gearboxes of agricultural machines had carried out. It was found that the defect in size is 12.45 %, and the defect in shaft size is 8.69 %. It had found that the greatest wear of the holes when reaching 0.082 mm, about 19 % of the gears must be replaced due to the excess of the inner diameter, the shafts wear up to 0.12 mm and about 23 % of the shafts have rejected. It has shown that a transitional fit is assigned in the new joint, as evidenced by the presence of both clearances and interferences, and interferences predominate. The defect to the left of the span of a fit is 0.91 % and to the right is 0.47 %. This indicates that all new holes and shafts can be allowed for assembly, including those provided by defect, but as a result, there will be practically no defect in the joints. When joints have formed from worn parts, above 25 % of rejects at the maximum clearance, therefore, flaw detection and complete control in this case are necessary.

Phase-Sensitive Optical Coherence Microscopy of Integrated Nanophotonics Devices

We report on the development of a new approach for studying the internal structure of polymer integrated nanophotonics devices using phase-sensitive optical coherence microscopy. Visualization and flaw detection of devices and their internal structure was carried out using the example of coupling gratings and prisms for a miniature Otto configuration with a characteristic gap height of 50-300 nm.