Laser strike: Associate Professor of MAI - about a new technology for increasing the strength of aircraft parts

— Maksim Alexandrovich, as far as I know, Russian aircraft are highly reliable.

The resource of domestic airplanes and helicopters according to the glider reaches 60-80 years.

Why was it necessary to create a new technology for strengthening

- Yes, you are right, if we are talking about the resource of the supporting structure of an aircraft, then it is measured in tens of years.

And, for example, the resource of aircraft engines is much less and is measured in thousands of hours, during which constant monitoring of their condition and, if necessary, repair or replacement of parts are required.

As applied to aviation, the technology developed at the MAI will significantly increase what is called fatigue strength in engineering.

In our opinion, the technology of laser impact or laser impact hardening is most suitable for parts subjected to extreme mechanical stress during operation.

In particular, laser impact hardening will extend the life of such an important element of any gas turbine engine as a blade.

The reliability of these products is always given special attention, since they do the main work of compressing air in the compressor and converting thermal energy into mechanical energy in the turbine.

Thanks to the blades, a jet thrust is created that is sufficient to lift the aircraft into the air, and the higher the quality of the blades, the higher the efficiency, resource and reliability of the power unit.

The manufacture of blades is a very time-consuming and high-tech process.

It is no coincidence that only four countries (Russia, the USA, Great Britain and France) have the ability to produce aircraft engines on their own.

• Industrial laser machine

• © press service of Shvabe holding

Increasing the resource and reliability of the blades is one of the main tasks that we are trying to solve.

Why is it so important?

On modern passenger aircraft, the engines are located on the wing.

Foreign objects often get into the path of the power unit: from sand to birds.

As a result, damage in the form of nicks is formed on the edges of the blades, which can later lead to the formation of cracks and even the destruction of the blades in flight.

— What is the essence of laser hardening technology and its uniqueness?

— To obtain the effect of hardening in the metal, we use a solid-state nanosecond laser with a high power density (about 10 GW/cm²).

This type of laser began to improve thanks to experiments in the field of thermonuclear fusion.

After a special preparation of the workpiece, the radiation of a solid-state nanosecond laser initiates a microexplosion on its surface, the shock wave from which is transmitted to the metal.

This phenomenon was first described back in the Soviet years by employees of the Physical Institute.

P.N.

Lebedev Institute of the Russian Academy of Sciences Gurgen Askaryan and Evgeny Morozov, as well as Lev Mirkin from Moscow State University.

However, the practical application of these phenomena in technology was found only in the early 1990s.

The shock wave from the microexplosion leads to the formation of a local zone of plastic deformation on the surface.

In simple terms, a small dent forms in the part.

The metal inside the dent becomes as if compressed.

Sequential surface treatment and the formation of a plurality of such zones leads to the formation of a layer of compressed metal.

If a defect occurs on the surface of the part in the form of an incipient crack, then the rate of its growth deep into the metal will be significantly reduced due to the "compression" of the crack with a layer of modified metal.

As a result, the part becomes much stronger.

—

— Shot-impact methods have been used for a long time in domestic and foreign production.

It is a well-established and widely used hardening technology.

Its essence lies in the impact on the surface of a part of metal or ceramic balls, which are accelerated by air, an impeller (rotating parts of various mechanisms) or in some other way, which leads to deformation of the metal surface.

The disadvantage of shot-impact methods is the low (compared to laser impact) depth and compression of the metal layer, approximately 2–6 times less.

— What result have you come to now?

— In the spring of last year, we began to cooperate with JSC UEC-Aviadvigatel in the development of a technological process for laser shock treatment of gas turbine engine blades.

As part of this work, the first Russian experimental installation for processing parts was created.

• Maxim Lyakhovetsky (second from right) with the engineers of the department 205 "Technology for the production of aircraft engines"

• © MAI press service

- Recently, parts made of composite materials, including blades, have been increasingly used in aviation.

Do such engine elements need laser impact technology?

— Composites are a separate world, where their own laws apply and special production technologies are used.

A typical composite part is intertwined fibers held together by a binder (substance. -

).

If the adhesion (in this context, the bond between the fibers and the binder) is poor, then the strength and reliability of the part will be low.

To test the strength of a composite, so-called destructive testing is often used.

For example, recently it was carried out with a caisson - the power element of the MS-21 composite wing.

With composites based on laser impact technology, it is impossible to strengthen the part, but it is possible to develop an adhesion control process that will allow quality to be assessed using laser impact.

I think that this technology, due to its accuracy, may well find a niche in the production of composite parts.

— For what other parts of an aircraft engine, besides blades, will laser impact technology be relevant?

“In an aircraft engine, laser impact technology can increase the fatigue strength of the disk into which the blades are mounted and the shaft to which the disk itself is attached.

The technology is of great importance for hardening splined and gear joints that provide torque transmission.

All these parts are subject to large alternating loads (sharp drops in mechanical loads. -

), which means they are sensitive to the development of fatigue cracks.

Thus, there is a fairly large range of aircraft engine parts that require hardening using laser impact technology.

- How much is it planned to increase the strength of parts?

“Now we are at the stage of testing and just trying to understand the exact figures for the increase in fatigue strength in order to evaluate the effectiveness of the developed regimes.

The customer expects the technology to show improvements of at least 20% over traditional methods.

According to some information, it is possible to achieve an improvement of up to 100% relative to regular technological processes.

— But how important is it in principle to significantly increase the strength of parts in practice?

After all, many components are sometimes easier to replace with new ones ...

- Firstly, situations are different, and, unfortunately, cases of destruction of parts in flight are not uncommon.

Therefore, it is important to increase the reliability of the elements of such critical equipment.

Secondly, there are a large number of products related to power equipment (gas turbine plants, gas compressors, oilfield equipment, etc.) that work in places where it is not so easy to get to, and even more so to carry out high-quality repairs.

That is, in this case, the reliability of the units is also of decisive importance.

• Industrial machine using laser energy

• © rostec.ru

— Is it possible to say that your technology is universal and can potentially be used more widely?

- In fact, it can be used to increase the strength of any metal products operating under conditions of alternating loads.

In addition to aviation, laser impact technology can be in demand to improve the strength characteristics of power plants, sea-based power units, nuclear power plant equipment, spacecraft units and assemblies, gas production and oilfield equipment, etc.

On the other hand, for industries where there are no serious problems with the replacement of components and maintenance, laser impact hardening technology may be redundant.

— Can we say that this technology is generally quite expensive?

Is it realistic to implement it on an industrial scale?

— I will not hide that the technology of laser impact is much more expensive than the shot-impact method.

The positive effect for the consumer is achieved mainly due to a significant increase in the service life of the equipment, which becomes more unpretentious and resistant to environmental factors.

Bringing laser strike technology to industrial use is our key task.

Now, for this purpose, we are carrying out relevant R&D (research work) and R&D (experimental design work).

The current main task is to create a domestic laser system that could work stably and reliably under production conditions.

We have a complete vision of how to adapt it for industrial use.

To do this, we use broad cooperation and try to integrate all the best technical solutions and practices.