Destructions Diagnostics of Aviation Engines Elements

by Holographic Interferometry Method

R.Kh.Makaeva, A.M.Tsaryova

Kazan State Technical University of A.N.Tupolev’s name

K.Marx, 10, Kazan, 420111, Russia

 

The obligatory application of various diagnostics methods and non-destructive control on stages of the production, exploitation and repair of is one of the effective supplying ways of the high reliability and longevity increasing of the modern aviation gas-turbine engines. The methods of the non-destructive control subdivide on acoustic, magnetic, electromagnetic, optic, radiation and others, depending on the physical phenomena determined in a basis. Each method is used for detection of the certain kind defects.

At mechanical tests of objects is applied the holographic interferometry. This method provides the simultaneous reception of the evident information about moving points on all researching surface of the three-dimensional diffusely scattering objects of the complex geometrical form. Moreover this method is contactless and has high sensitivity, caused by the process of the light interference.

For researches of the objects deformation in statics and dynamics the different methods of the holographic interferograms recording are used.

For example, pictures of deformations at static mechanical and temperature tests, and also at loading by internal pressure receive by double exposure method. Two various states of object - two appropriate wave fields are registered on one hologram. Fields of both waves are reconstructed simultaneously at illumination of the received hologram. One wave corresponds to the image of the non-loaded object recorded at the first exposition. Another wave - image of the loaded object recorded at the second exposition. The interference picture is formed in result of the imposing of two images. The curvature and quantity of the strips show the change character of the object state between two expositions. The presence in object of the crack (superficial or close to the surface) causes the break of the interference lines in the area of defect.

For example the cylinder with internal defects was investigated. Zones of anomalies of a picture of strips coincide with the locations of defects on holographic interferograms, received at test of the cylinder by internal pressure. The unsolder zone of the cooling channels in heat exchanger was found by double exposure holographic method.

The holographic record by the time-average method is used at oscillatory processes. During vibration one holographic exposition is carried out. The hologram registers the set of the images appropriate to averaged position of object during the fluctuations. As the vibrating object the most part of time is in extreme amplitude positions, these two fields of object are registered on the hologram. They create interference picture on the restored image. The interference strips connect the points of equal amplitudes. The bright light strips correspond to nodal lines on the vibrating surface of the object. The restored hologram reproduces the forms of fluctuations.

This method is applied at researches of own frequencies and object fluctuation forms. For example the fluctuations of turbine and compressor blades, disks with the complete set of the blades are investigated by the time-average method. As the authors mark, to receive the similar information by any other method would be extremely inconveniently.

In this work the diagnostics of the generator inflow impeller of the aviation gas-turbine engine destruction will be carried out over pictures of the fluctuation forms, which received by the holographic interferometry method. This detail is one of the intense construction elements of the aviation gas-turbine engine while in service. At concurrence of the vibrating loading frequency and own impeller frequency there are resonant fluctuations that can result in initiations of the fatigue cracks, their further development and destruction.