Acoustic emission of pipelines

представляет собой возникновение и распространение упругих колебаний в процессе деформации исследуемой конструкции. Acoustic emission of pipelines is the emergence and propagation of elastic vibrations during deformation of the structure under study. Quantitatively, it acts as an indicator of the integrity of the material under different loads. может применяться для установления дефектов на начальном этапе разрушения конструкции. Acoustic emission monitoring can be used to identify defects at the initial stage of structural failure. The main method of diagnostics is passive data collection and their subsequent processing.

general characteristics

используется для обнаружения и установления координат, мониторинга источников деформации на поверхностях либо в объеме стенок, сварных соединений и элементов конструкций. Acoustic emission is used to detect and establish coordinates, monitor deformation sources on surfaces or in the volume of walls, welded joints and structural elements. Diagnosis is performed only when a stress state is created. It initiates the operation of oscillation sources in the object. возникает при воздействии давлением, силой, температурным полем и так далее. Acoustic emission occurs when exposed to pressure, force, temperature field and so on. The choice of a particular load is determined by the design features, the conditions in which it is used, the specifics of the tests.

Acoustic emission method

To determine the reliability index of a structure, it is checked its parameters and properties, in which its integrity and suitability for use and operation should not be violated. Traditional methods (ultrasonic, vortex, radiation and others, popular in practice) allow us to identify geometric inhomogeneities by emitting a certain energy into the structure of the object. предполагает иной подход. Acoustic emission suggests a different approach. First of all, the material itself acts as the source of the signal, and not the external object, since it is a passive way of checking, and not active, as indicated above. позволяет обнаружить не статические неоднородности, а перемещение дефекта. In addition, acoustic emission can detect non-static inhomogeneities, and the displacement of a defect. Accordingly, with its help it is possible to reveal developing and, therefore, the most dangerous destruction. This method allows you to quickly detect the growth of small cracks, leaks of liquid or gas, faults and other processes that cause the occurrence and propagation of vibrations.

Nuances

Theoretically and practically, any defect is capable of producing its own signal. . It can travel quite a long distance (several tens of meters) until it is detected by an acoustic emission sensor . Moreover, destruction can be detected not only remotely. Defects are also established by calculating the difference in the arrival time of the waves to the pick-up sensors located at different sites. The growth of cracks, delamination, fracture of inclusion, friction, corrosion, leakage of liquid / gas are examples of processes that produce oscillations that can be detected and effectively investigated.

Features

The main advantages of the method over traditional methods of nondestructive testing are:

1. Integrity. , неподвижно установленный на поверхности конструкции, можно проверить ее всю целиком. It consists in that, using one acoustic emission transducer , fixedly mounted on the surface of the structure, it is possible to test the whole of it. This property is especially important when studying hard-to-reach or inaccessible areas.
2. No need for thorough preparation of the surface of the object under study. From this it follows that the control process itself, as well as its results, will not depend on the state of the design and the quality of its processing. If there is an insulation coating, then it must be removed only at the installation sites of the trapping devices.
3. Identification and registration of only developing destruction. This makes it possible to classify defects not by their size or other indirect indicators (position, form, orientation), but by the level of their danger (the degree of influence on the strength of the object).
4. High performance. It is many times higher than the corresponding indicators for traditional (radiographic, ultrasound, magnetic, eddy current, etc.) control methods.
5. Distance. Checking the strength of the object can be performed at a considerable distance from the operator. This feature makes it possible to apply the method when controlling the state of large, especially dangerous, extended structures without decommissioning and personnel.

Another advantage is the ability to monitor different technical processes and assess the state of the design in the current time mode. This allows you to prevent an emergency destruction of the object. It should also be noted that in the method of acoustic emission, optimum quality and cost parameters are combined.

Additionally

Control with the use of acoustic emission provides a huge amount of information, allows with minimal costs, promptly regulates and prolongs the cycle of operation of critical industrial installations. The results of the performed checks are used in forecasting emergency failures. This method of control can be used in the study of various properties of materials, structures, substances. Today, without its use, it is impossible to create, as well as reliably operate a multitude of responsible facilities in the industry.

Minuses

There are some drawbacks to the method of acoustic emission. The main disadvantage is the complexity of deciphering the indicators obtained during verification. This drawback significantly limits the wide application of the method in practice. The complexity is due to the fact that the wave processes in the acoustic emission are superimposed so-called parasitic indicators of repeatedly reflected noise, waves from the operation of equipment, the loading object, and the environment. The use of protection systems and various filters allows only a partial reduction of the impact. In addition, the uniqueness of the equipment used in the control is considered a disadvantage. In industry, it is not produced in bulk. This also does not allow the method to be extended beyond the field of experimental use.

Applications

As it was said above, at the present time the method of acoustic emission is used by various enterprises engaged in various economic spheres. The main ones are:

1. Chemical and oil and gas industry.
2. Metallurgy and pipe-rolling production.
3. Thermal and nuclear power.
4. Railway transport.
5. Aerospace complex.

The method is widely used by enterprises working with lifting, bridge structures, concrete and reinforced concrete structures.

Conclusion

Acoustic emission method is considered today one of the most effective ways of performing non-destructive testing and assessing the state and properties of materials. It is based on the detection of elastic waves generated when a sudden deformation of a structure under load occurs. The resulting oscillations depart from their source and are sent directly to the sensor, where they are transformed into electrical signals. Special instruments are used to measure them. After that, the processed information is displayed. Based on this, a subsequent assessment of the state and behavior of the structure of the objects under investigation is carried out.