Scientists from the School of Non-Destructive Testing and Safety of TPU have created a stationary system for thermoacoustic control of defects in polymer composite materials for the aviation and space industries.
«The advantage of the thermoacoustic method is that it can be used to detect defects that cannot be detected by classical ultrasonic or thermal control methods using optical stimulation. These include, for example, very small cracks that reach the surface, as well as cracks that are located on the reverse side relative to the controlled surface. Previously, the thermoacoustic method was successfully tested by us in cooperation with industrial partners to detect cracks in gas turbine engine blades.
The stationary thermoacoustic control system for detecting defects in composites is similar in principle to a 3D printer, but instead of a printing head, it has an infrared camera and an ultrasonic stimulation device. Their movement, as well as the movement of the table on which the control object is held, is carried out using a motorized system. The movement system is controlled by buttons on the system panel, and the control procedure is carried out using a remote computer. The control system and software were completely developed by the team of the School of Non-Destructive Testing and Safety, which included researchers, engineers, graduate students and students.
A special feature of the system is the use of the thermoacoustic control method. It is based on observing changes in the temperature parameters of the control object, into which acoustic signals are introduced, and is at the intersection of ultrasonic and thermal methods. The essence of the method is that powerful high-frequency oscillations are introduced into the product. They propagate in the body of the object and, upon contact with a defect, the mechanical energy of the oscillations is converted into thermal energy. In areas where there are cracks or delaminations, friction and local heating occur. Under the influence of ultrasonic stimulation, a thermal imager registers changes in the temperature of the control object, the defective areas of which appear as "hot spots".
Another feature of the development is that it allows assessing the condition of both cylindrical and flat products, as well as products of complex geometric shapes, including large objects.
The work was carried out by order of STC Etalon LLC, and in the future, the system developed by the Polytechnic University will be transferred by the customer to NPO Energomash JSC as part of a large non-destructive testing complex.
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