Strength and Reliability 

CIAM's research school of investigating engine strength and reliability is widely known in Russia and abroad. Its particular features include a combination of fundamental studies and aircraft engine industry practices; integrated solutions of applied design and structural strength refinement problems; close relationship of the Institute's research and engineering teams with design bureaus, manufacturing factories, and aircraft operators.

Special attention in CIAM is paid to studies of the design strength (strength that can be implemented in the design in expected operating conditions), development of deformation and destruction models for new materials (monocrystalline and granulated disc nickel super alloys, intermetallides, various composite types, etc.)

The establishment and development of the research areas of the strength and reliability school are associated with the names of remarkable researchers like I. Neiman, R. Kinasoshvili, I. Birger, V. Akimov, S. Serensen, V. Natanzon, K. Zhitomirsky, A. Kolomiytsev, V. Darevsky, and many other talented engineers and researchers. CIAM's research school has made a valuable contribution to solving the problems of ensuring strength and reliability of reciprocating aircraft engines, gas turbine engines, helicopter rotor drive systems, and stationary fuel cell power systems.

Calculations and experimental studies of:

• Static strength and cycle life of gas turbine engine parts and components with regard to design and process factors, deformation specifics, damage and destruction accumulation in expected operating conditions (including anisotropy of material properties, plastic behavior, creepage, defect presence, etc.);

• Dynamics of the engine as a whole, rotor/body systems, gas turbine engine parts and components; including vibration damping studies, investigations of devices for reducing loads acting on structural engine components and its mounts to the aircraft at a fan blade breakage;

• Resistance of structural engine components to bird strikes, ice, and foreign matter ingestion;

• Engine case ability to contain damage caused by rotor fragments in the case of a rotor failure.

The most important problem of new engine designing is the developing of rationale for the selection of structural materials with optimal strength, process and operating performance for main gas turbine engine parts; and implementing leading-edge technologies allowing to achieve the target engine performance while also enhancing the engine reliability and service life.

At the same time, the implementation of new design solutions, new materials and technological processes requires in-depth comprehensive studies not only in the field of mechanical properties of materials, but also the strength of full-scale parts at high temperatures and under static, cyclic, and vibration loads.

One of the defining areas of aircraft engine enhancement is the utilization of composite materials (composites) in all components of various purpose aircraft engines. Global experience demonstrates that aircraft engines are becoming more and more "metal-free".

Composite materials are made of semi-finished products and at the same time as the structure, i.e., a composite with the performance necessary for the final product and the final product are formed simultaneously during the manufacture process. For this reason, the matters of design (in the traditional sense), rational reinforcement, and process development are the three sides of the same problem, as far as the composite structure manufacturing process is concerned, and cannot be viewed separately, which is possible when dealing with metal structures.

This particular feature of composites, as well as the anisotropy of their properties and non-homogeneity of their structure are factors that compel engineers to search for new approaches when working with composites. In comparison with traditional "metallic" technologies, composites require 25 times as many tests for determining their properties, which, in turn, demands the use of custom methods and special equipment.

In CIAM, studies in this area are conducted in the Department of Structural Strength of Composite and Ceramic Parts and Components of Aircraft Engines, which was established in 1967. The work conducted in the department covers an extremely wide variety of matters, from fundamental studies of non-homogeneous continuum mechanics to providing direct assistance to designers and manufacturers in development of composite and ceramic components including components made of intermetallides, glass- and carbon-fiber reinforced plastics, carbon fiber reinforced aluminum composite, boron fiber reinforced aluminum composite, carbon-carbon composite, glass-ceramics; reaction-bonded, sintered, hot-pressed, discontinuous fiber reinforced ceramic materials, etc.

During more than 45 years of aircraft engine fan and compressor testing in environmental chambers, CIAM engineers and industry experts have obtained a vast amount of experimental data based on blade flutter studies.

These experimental data have now been generalized in CIAM using mathematical statistics methods in a multi-dimensional space of dimensionless diagnostic factors. The system of these factors has been formed based on physical flutter models and optimized using information criteria.

The flutter prediction software based on experimental data generalization now contains over 200 flutter cases and is regularly updated whenever new experimental data become available.

An analysis of the results studies flutter done for Russian and foreign companies for the last 20 years demonstrate that the CIAM's software solves the flutter prediction problem with a maximum error by 10%.

Gear mechanisms used in aircraft engines and helicopters play an extremely important role in gas turbine industry development. The most important parts in next generation high bypass aircraft engines are high-speed gearboxes. Reliable operation of the gearbox and entire engine depends directly on gear mechanism reliability. The most relevant problems of ensuring gearbox reliability are avoiding vibrations that cause changes in gear tooth stiffness; using modified gear mechanisms to enhance gearbox reliability; reducing noise; moving to on-condition operation of equipment; and a number of other problems.

CIAM has unique experience in the design of gears, pinions, and drive system components. To enable timely development of new generation engines, closer cooperation in the design of aircraft drives and helicopter rotor drive systems should be maintained between CIAM and companies operating in the industry. Also important is the matter of commissioning of advanced equipment for gearbox and rotor drive system monitoring and diagnostics developed by CIAM.

Work Areas

• Strength calculations of gears and pinions of aircraft engine drives and helicopter rotor drive systems;

• Static and dynamic strength calculations of gears, pinions, helicopter main rotor shafts, gearbox structural components, as well the entire rotor drive system assembly;

• Research support of aircraft drive system design, including the provision of recommendations and requirements for ensuring design reliability;

• Development of kinematic diagrams of advanced helicopter rotor drives systems;

• Establishing a foundation for development of kinematic diagrams for future helicopters, including adjustable rotor drive systems of high-speed helicopters;

• Analyzing and selecting configurations of planetary transmissions of turbofan engine gearboxes and helicopter rotor drive systems;

• Mathematical modeling of the entire working cycle of aircraft transmissions and rotor drive systems;

• Dynamic modeling of oscillations of aircraft transmissions and rotor drive system components;

• Modeling of mesh heating processes and calculation of the required tooth cooling parameters;

• Establishing a foundation for the design of highly efficient dry friction dampers for conical gears of helicopter gearboxes;

• - Seeking and identifying diagnostic symptoms of aircraft drive component conditions using composite error and vibration signals;

• Development of algorithms and methods for evaluating parameters of vibration and composite error signals, i.e. the set of diagnostic symptoms that can be used to determine the condition of multi-shaft mechanisms (aircraft drives and drive components);

• Studies of vibration of helicopter gearboxes and engine accessory gearboxes during bench testing and operation;

• Vibration measurements and subsequent processing of signals recorded and providing equipment vibration condition reports. These efforts are carried out as part of service life, redelivery, and acceptance testing of gearboxes and accessory gearboxes of engines and helicopters. The efforts are also carried out during operation by engineers visiting helicopter (aircraft) bases;

• Development of expert software for processing of signals and performing calculations of diagnostic symptoms of helicopter rotor drive and engine accessory gearbox equipment;

• Software products are designed for organizations and companies involved in the refinement, testing, operation, and maintenance of aircraft and helicopters. The software can also be adapted for industries that employ gear systems, such as transport, the power industry, ship building industry, chemical industry; in machine and machine tool building, oil and gas production, etc.;

• R&D in development of on-board helicopter diagnostics systems.