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.

Модернизация эхометода ультразвуковой дефектоскопии

The modernization of the echo method of ultrasonic flaw detection is considered, which differs in that in addition to the array of transducers in contact with the working (front) surface of the object, one or more receiving transducers on the lateral surface of the object are additionally used. This method of arranging the antenna arrays can significantly improve the resolving power, and in the case of using an antenna array on the lateral surface of the object, obtain additional information for imaging the internal structure of the object. In order to obtain the potential resolution, an ultra-wideband sounding signal with a Gaussian envelope is used in combination with an original signal processing algorithm, including summation, one-way limiting and multiplication of the received signals. Some practical recommendations are given in the work. Potential resolution in various directions has been assessed.

Определение координат отражателей в плоскости, перпендикулярной сварному соединению по эхосигналам, измеренным преобразователями по схеме TOFD

The TOFD method, which is widely used in ultrasonic flaw detection, makes it possible to distinguish a crack from a volume reflector by the phase of the echo signals and to determine its height with high accuracy. However, the TOFD method without scanning the piezoelectric transducers across the weld joint does not allow to determine the displacement of the reflector from the center of the welded joint, which is very important when evaluating the results of the control. The scanning devices used for this purpose have a complex design, their price is higher than that of one-dimensional scanning devices, and, most importantly, the control time increases significantly. If the echo signals reflected from the bottom of the object of control are used, taking into account the change in the wave type, then a combined image of the reflector can be obtained from a set of partial images recovered by the digital focusing antenna (DFA) method. If we use the echo signals measured in the combined mode for each piezoelectric converter, we can estimate the displacement of the reflector across the welded joint with an accuracy of ±1.5 mm. Numerical and model experiments have confirmed the efficiency of the proposed approach.

Определение типа отражателя по амплитудам бликов изображений, восстановленных по разным акустическим схемам

In ultrasonic flaw detection, methods for recording and analyzing echo signals have been developed to determine the type of reflector and its size. The method of digital antenna focusing (DFA) allows you to restore the image of the entire boundary of the discontinuity, using echo signals reflected from the bottom of the control object, taking into account the transformation of the wave type. However, this approach is not always applicable in practice, since the shape of the bottom of the object of control may be unknown. Using the features of the behavior of the reflection coefficient for different types of waves, it is possible to make a conclusion about the type of reflector from the images only on the direct beam. Numerical and model experiments confirmed the efficiency of the proposed approach.

Sensitivity and Amplitude Measured Characteristics of the Defect. Review of Changes in Rail Flaw Detection over a Quarter Century

The review focuses on sensitivity in ultrasonic flaw detection in rails and related accompanying issues. The set of topics considered includes changes in definitions of terms, used measures and methods of sensitivity adjustment that have occurred over the past 25 years. Amplitude characteristics of detected defect are considered in detail. The article is supplemented with practical examples of sensitivity settings, as well as measurements of signal amplitudes and defect detection coefficient for various cases.

IDENTIFICATION AND RELIABILITY OF CONTROL IN ULTRASONIC FLAW DETECTION AND DEFECTOMETRY

The effectiveness of methods and means of ultrasonic non-destructive control (ultrasonic control) is evaluated by the probability of detecting defects and the reliability of the results of the control. In this work, we reserch the behavior of PoD(a) – the defect detection function, which describes the dependence of the probability of detection of defects on their height, and estimates the reliability of control by means of ROC analysis of the control data. An analysis of the PoD curves obtained by ultrasonic testing with ultrasonic flaw detection and ultrasonic flaw detection instruments demonstrates significantly greater reliability of the use of defectometry techniques and devices. ROC curves constructed using ultrasonic defectometry data make it possible to evaluate the reliability of control of defects of various heights. Analysis of ROC curves provides additional information for optimizing ultrasonic control techniques. The studies were carried out on the data array of ultrasonic testing of welded joints with real cracks.

Determination of hydrogen-induced damage by an acoustic method

The 13HFA corrosion- and cold-resistant steel is studied by an ultrasonic method after hydrogen absorption for 96, 192, and 288 hours. Within the framework of classical flaw detection, it was found that the formation of macrodefects occurs only at 288 hours of hydrogen absorption. In the study of the material by the spectral-acoustic method, it was found that, during hydrogen absorption for 96 and 192 hours, the signal spectrum changes. This indicates the formation of microdefects. It is shown that the determination of the damage by the conventional ultrasonic flaw detection method and the use of the spectral-acoustic method for the evaluation of fracture at the microlevel give more complete information on the state of the investigated alloys.