Nondestructive testing: trends and Outlook
K. E. Duissenov – President of oyul KADThe most obvious trend in the development of NC is the intellectualization of modern NC methods, which is the result of intensive computerization, extensive use of built-in processors, the development of a large number of working programs, algorithms for test and functional diagnosis. Visualization of the collected information in two - and three-dimensional images with the possibility of its subsequent processing has become the norm. However, the introduction of more informative technologies, such as amplitude-phase frequency processing of a multidimensional signal, reconstructive tomography, tomosynthesis, ultrasound holography require more productive means of calculation for comfortable operation in close to real time. There is no doubt that the intellectualization of NC tools will increase in accordance with the development of computing capabilities. All NDT methods in one or another degree over time, much wiser. We are already witnessing the beginning of this process. At the same time, the growth of intelligence will be accompanied by increasing automation of control procedures. The development of technical vision, robotics will allow you to perform control of objects with complex geometry at a higher level, which will make the control objective and minimize the human factor: "21 century robots work hard, not people." The transition to expert diagnostic systems for the control of large industrial facilities will be carried out systematically, allowing to determine and minimize the risks of operation. Clearly traced the development of NC systems for the study of micro-objects in connection with the rapid development of microelectronics, nanotechnology. So in the near future will be the development of microtomography, x-ray microscopy, microtomography, microendoscopy and other methods of microtropia. This is a consequence of the need to develop new materials and the need to undertake numerous studies at the micro level. Already today, the instructions and guidance documents prescribe the use of various methods of NC mutually complementary to each other to confirm the results of the control, or the exclusion of white spots from the data on the state of the object of control. The analysis of existing methods for assessing the residual life and risk of operation shows the feasibility of further improvement of methods for more accurate detection of defects in products at an early stage of operation. Evaluation of residual life using such techniques is characterized by the use of a large number of multifactor dependencies. Therefore, complex approaches will become relevant when the analysis of the object state will be performed on the basis of the results of several methods. In turn, this will require the following tasks: the development of new dynamic models that take into account complex multi-factor phase and structural changes of the technical product; the creation of techniques for obtaining the most informative features of the product in order to further diagnose and evaluate the probability of failure of the object. The construction of such techniques and algorithms is impossible without the use of combining different methods of NC. Finding bundles of interacting NC methods becomes a priority in a comprehensive approach to solving the problem of extending the service life of technical facilities The development of inter-state integration processes (globalism) will form common requirements and criteria in the assessment of personnel, means and methods of NC. In other words, all elements of the NC will be subject to unification. In part, we are witnessing this process now, for example, personnel in the field of NC are certified by only a few standards. The place of national standards is increasingly occupied by international – ISO. Therefore, over time, a unified approach will be developed to the selection (appointment) of types, methods and means of control, as well as to the definition of General requirements for methodical documentation on non-destructive testing. In the near future, the transition from flaw detection to flaw detection will be carried out, at least it will be possible. In many ways, this transition has already been prepared and even in some places we can observe it. For example, in ultrasonic testing the TOFD method, in regular Peugeot, allows to measure the size of the crack with an error of 1-2 mm, and in special cases this value can be reduced several times. The possibilities of various computational methods (SAFT, ultrasonic tomography, wave front reconstruction methods) allow to determine the sizes of discontinuities with acceptable error for the computational methods of fracture mechanics. In radiation control with the advent of industrial tomographs available exact form of discontinuity with an error much smaller than that required for strength calculation. Therefore, in the near future it will be possible to quantify the reliability of the element containing discontinuity. Based on the current state of the theoretical foundations of electromagnetic non-destructive testing, it can be assumed that there will be equipment that implements methods for multi-parameter control of the characteristics of products and materials, which can simultaneously determine the magnetic permeability, specific electrical conductivity, strength and yield strength, mechanical stress, hardness, the presence of dominant impurities, as well as perform reliable disassembly of materials by their brands. Prospects for the development of the capillary control method are primarily associated with its automation. Automation of control of products of different types, including large ones, is possible with the use of adaptive robotic manipulators, i.e. having the ability to adapt to changing conditions. Such robots are already successfully used in painting works, which are largely similar to capillary control operations. In this case, the inspection of the surface of the products and the decision on the presence of defects will also be automated based on the theory of pattern recognition. Automation of capillary control processes is appropriate in mass, in-line high-tech industries, for example, the production of turbine blades. In the conditions of non-mass production, operational control in the near future capillary control technology will remain without significant changes, perhaps with the exception of some aspects related to the materials used. Traditionally, an important area of development of capillary control is the search for new materials and technologies of their application, which aims to increase the sensitivity and performance of control. Promising application as a penetrant ferromagnetic liquids. In the liquid base (for example, kerosene) ferromagnetic particles of very small size are suspended (2..10 µm), stabilized surfactant, whereby the liquid behaves as a single-phase system. The penetration of such a liquid into the defects is intensified by the magnetic field, and the detection of indications is possible by magnetic sensors, which facilitates the automation of control. A very promising direction of improving capillary control is the use of electronic paramagnetic resonance. Relatively recently obtained substances such as stable nitroxyl radicals. They have loosely coupled electrons that can resonate in an electromagnetic field at a frequency of tens of gigahertz to megahertz, and the spectral lines are determined with a high degree of accuracy. Nitroxyl radicals are stable, low-toxic, able to dissolve in most liquid substances. This makes it possible to introduce them into liquid penetrants. The indication is based on the registration of the absorption spectrum in the exciting electromagnetic field of the radio spectroscope. The sensitivity of these devices is very high. Thus, the question of objective and highly sensitive means of indication in capillary flaw detection can be solved. Prospects for the development of the thermal method. It is obvious that a conventional thermal imager will gradually turn into a professional device, so to speak, into a thermal imaging flaw detector or even a flaw detector. For this purpose, specialized physical and mathematical models of the process of thermal non-destructive testing will be introduced into the thermal imager, as a software, allowing to simulate the control technology for various types of objects and materials encountered in practice: - products in the form of flat multilayer plates (for example, from polymeric composite materials, metals, etc.), modeling flat products, cylindrical, conical, etc. - products of complex shape, for example, cellular structures, - passive fuel objects (e.g. buildings, chimneys, etc.), taking into account their thermal inertia and the influence of external climatic factors. On the basis of the existing theoretical developments, it will be possible to determine the characteristics of the detected defects - the depth of occurrence, disclosure, types of internal defects and material characteristics of the controlled objects by solving the inverse problem of non-stationary thermal conductivity in a multilayer medium with inhomogeneities. Thermal imagers will be equipped with a set of standard software and hardware for automated non-destructive testing and diagnostics of the technical condition of a large class of materials, products and structures of engineering and construction industry: - active thermal nondestructive testing of multilayer products made of polymeric materials in the form of plates and honeycombs (plates with an edge), passive thermal nondestructive testing of passive fuel objects (building structures and residential buildings), active thermal non-destructive testing of sheet and bar sections in terms of the technological cycle of rolling mill providing for the identification of informative parameter control, automated process settings, auto, nonstandard detection of discontinuities, determination of the geometric and thermophysical characteristics of discontinuities of materials, products and structures, the definition of the areas and the coordinates of the discontinuity, accumulation, storage and analysis of inspection results. If we try to formulate the above easier, in fact, a specialist in thermal control will receive not just a tool for observing the thermal picture, but a tool for analyzing the properties of objects based on the quantitative measurement of the thermal fields of this object. In my previous report, I described the current state of radiation techniques. It is enough to predict the growing popularity of digital radiography. Even today, this technology is economically justified in mass production. Digital radiography, while retaining all the advantages of traditional, can be relatively easily automated. I mentioned earlier the advantages of digital radiography over traditional radiography, I will not repeat, saving our time. I will only say that the further technical perfection of digital radiography, with its obvious advantages, will replace the film for several years. The process of displacement will occur even in non-mass production, for example, in operation. In General, this will happen as quickly as digital photography supplanted film. I am sure that no one here uses a film camera, and this technology was at the peak of its popularity only 20-25 years ago. And finally, the actual universal tomography of industrial products for non-destructive testing of internal structure, development of technologies and certification of critical parts and assemblies. The uniqueness of x-ray tomographs is quite obvious, there is no alternative to it for the control of complex critical products of aerospace, automotive, defense engineering, etc. The development and introduction of industrial tomography scanners is not adequate to the progress of digital technology due to the penetrating power of brake radiation, which did not allow to perform control on real industrial metal products of more or less significant thickness. Recently, there has been progress in this direction, there are already scanners capable of working with metal products with a total thickness of 100-150 mm. In the coming years, this limit will be significantly exceeded, which will allow to control a very large range of metal products. Due to the continuous increase in the volume of data of two-dimensional and three-dimensional results of tomographic control, the transition from interactive decoding of digital tomograms by an experienced operator to automatic diagnosis with the formation of the final Protocol of quantitative assessment of compliance of tomographic results of control and requirements of design documentation for the product is inevitable. Automation of a full cycle of quantitative tomographic diagnostics is most justified for specialized industrial tomographs of a narrow class of products, increases productivity and reduces dependence on the "human" factor in the interpretation of control results. Prospects of ultrasonic testing are associated with automation (robotization) of production, development and implementation of methods for accurate determination of geometric dimensions of defects. We will observe the improvement of complex systems of operational control, which will integrate several methods of ultrasonic testing. Obviously, this will be facilitated by the further development of antenna arrays. So from rather simple systems with one-dimensional antenna arrays there will be a transition to two-dimensional. At the same time, the reliability of such control will be brought to values close to one. At the same time, control systems will have greater operational reliability and structural simplicity. It should be expected that the operational control systems will become smaller in size and weight, lose cables, as all data will be transmitted wirelessly. In fact, such systems will have one or two two two-dimensional matrices, on the basis of which it is possible to organize simultaneously all existing schemes of narrow and many others, which are practically not available to the traditional narrow. Moreover, I want to note that with all these working schemes, the scanning speed will not be fundamentally different from traditional control systems, i.e. systems using converters with fixed input angles. Since the reliability of the control of such systems will be much higher than the existing manual control by echo method, over time, such systems replace manual control. Taking into account the absence of cables and comparable dimensions and weight, it will be easier to work with such equipment. Of course, such changes will not occur immediately or within 10 years, probably, it will take a little more time, but the introduction of individual elements and the growth of quantitative capabilities we will observe constantly. At the moment we observe some discrepancy between the increased capabilities of ultrasonic systems and the existing regulatory framework, which is developed under the traditional manual control and its modest capabilities. On the one hand, this conservatism is justified, the new equipment must be tested by practice and prove its worth. Indeed, one-dimensional antenna arrays without positioning do not give a qualitative superiority over traditional technology, but several times or even an order of magnitude more expensive. The high price of flaw detectors with antenna arrays hinders a wide transition to this technology, but not only the price. Fundamental changes in the regulatory documentation will occur when modern systems will have a noticeable or obvious qualitative superiority in the reliability of control. Only in this case the transition will be massive. I believe that this transition will be reflected in the standards as a transition from equivalent and conditional sizes of discontinuities to their exact geometric dimensions, i.e. the transition from flaw detection to flaw detection. We are already close enough to this event, we can say on the threshold of the era of defectometry. Let's note one more very important prospect of ultrasonic inspection. It is known that very much limiting the operational capabilities of ultrasound is acoustic contact, or rather the complexity associated with its maintenance. For good contact, the surface of the test object must be prepared to the level of roughness Rz 40 microns (or RA 6,3), which in itself is a complex and time-consuming operation, and in operating conditions is often not achievable. All this significantly complicates the use of ultrasound and reduces its value. For decades the direction providing contactless excitation of ultrasonic waves on the basis of electromagnetic-acoustic excitation (EMA) has been developing. Recently, as follows from the materials of some publications, it was possible to ensure the sensitivity of the EMA in a way not worse than that of "wet" ultrasonic flaw detectors. If, indeed, such a technical solution is found, the operational capabilities of ultrasonic testing will be difficult to overestimate. To dream about the possibilities of "contactless" ultrasound I provide to everyone. In conclusion, we note the further development of methods of ultrasonic testing of long objects, which is based on the use of specific types of elastic waves in a solid body: surface waves, waves in plates, rods, pipes, etc. This is a relatively new, rather complex and popular industry direction in ultrasonic testing, so here we should expect the discovery of new laws and opportunities for the identification and evaluation of discontinuities.
Overview of the current state of nondestructive testing
K. E. Duissenov – President of oyul KADDevelopment of NC methods is one of the most priority directions of scientific and technological progress. This is due to the fact that NC methods allow not only to control, but also to control the quality of products, predicting its properties, parameters, in case of failure of products. Due to the complexity of modern industrial products and the use of the latest structural materials with a complex internal structure, as well as with increasing requirements for the reliability of new equipment, the volume of control operations in the industry increases sharply. Currently, quality control is the most mass technological operation in production, since no part can be made without measuring its technological parameters. The development of scientific and technological progress in the areas of industrial production requires greater use and improvement of non-destructive testing methods to maintain high operational reliability and minimize risks. Currently, the number of NC methods has exceeded 100. All methods are constantly developing quantitatively and qualitatively. Development of NC methods corresponds to the development and demands of the industry. As well as the sea is reflected in the drop, the whole world industry is reflected in the current state of the NK. Of course, in a relatively small report it is impossible to give a detailed state of all the methods of NC, but you can try to note the most significant achievements and current trends in the types of NC. The technology using x-ray film is based on the chemical effect of ionization. The detection result is determined by the difference of blackening of different parts of the film under the influence of x-rays, depending on the density and thickness of the object under control (OK). Until recently, this technology was the main in the conduct of x-ray studies in various fields of application. However, there are a number of reasons for the need to develop other methods of x-ray image registration: - low quantum efficiency of the film; limited dynamic range, which prevents the work with the object of control having a different density, and makes it difficult to choose the optimal exposure; - increasing costs for the process of photochemical treatment of x-ray film, the desire to abandon environmentally harmful procedures; - the difficulty of the content of the film archive. On the other hand, this contributed to: − development of the component base of the electronic industry, allowing the development of modern types of x-ray detectors; − development of computing power of modern computers, allowing to implement complex algorithms for processing data arrays of radiation images in the shortest time; The current state of nondestructive x-ray inspection (NDT) is characterized by the intensive development of digital systems (CS), which allow obtaining a radiation image (RI) of the object of control (QA) in the form of a digital signal. The data array obtained from this digital signal can be processed using various algorithms and then displayed to the control operator in the form of a halftone image on the graphic display screen. For this direction was fixed the term digital radiography. If we lower the level of rigor in the presentation, which is acceptable for a General overview report, we can say that between film and digital radiography the same analogy as between film and digital photography. Digital radiography allows much better and faster detection of defects in the object of study. The process of determining defects and calculating their parameters in this case allows for automation, which leads to improved performance. Displaying information in digital format makes it possible to save space in the room, because now huge shelves with film archives are not needed – everything you need is recorded in a computer database in the form of files. Example of a flat panel x-ray detector PerkinElmer XRD 1611 xP, which replaces the traditional film. The advantages of digital radiography include:
- high quality x-ray image, the possibility of its digital processing and identification of important details,
- possibility to reduce the radiation dose,
- simplicity and speed of image acquisition, which becomes available for analysis immediately after exposure,
- storage of information in digitized form makes it possible to create easily accessible and mobile x-ray archives, transmit information at any distance on a computer network,
- environmental safety compared to traditional: eliminates the need for reagents and "toxic" process of development,
- faster results provide an opportunity to increase productivity, because there is no need to re-install x-ray equipment and its adjustment in cases where the images were unsuccessful,
- high quality images with the possibility of their backup eliminates the need for repeated procedures with additional radiation of the patient.
- With all the above advantages, digital radiography has one significant drawback – the high initial cost of equipment compared to analog x-ray equipment.
- higher detection of defects - it is possible to generate different input angles with a single antenna array, which allows you to get the best reflection of discontinuity regardless of its orientation, which is impossible for a conventional ultrasonic transducer with a fixed input angle
- by means of fast electronic scanning it is possible to increase the speed of control the
- ability to focus allows you to increase the resolution of the
- easier and more accurate than traditional ultrasound determination of the position and size of defects
- visualization of control results.
- Inspection of pipes of different diameters
- Possibility to control pipelines without decommissioning
- Ability to scan at high temperatures (using high temperature transducers— over 250 degrees Celsius)
- Large length of the diagnosed area (up to 250 m each way from the antenna)
- Visibility of scan results (all data is displayed on the computer screen as an informative graph)
- High scanning speed
- Possibility of operation without removing the pipeline insulation