Automation of aircraft components with geometrical stress concentrators fatigue endurance calculations

Dynamics, strength of machines, instruments and equipment


Polonik E. N.*, Surenskiy E. A.**, Fedotov A. A.***

Irkut Corporation, 68, Leningradskiy prospect, Moscow, 125315, Russia



The paper contains the description of the computer program SNCalculator meant for fatigue endurance of aircraft components with geometric stress concentrators computation. SNCalculator is integrated into finite elements computation bundled software Femap. It allows significantly increase the degree of computations automation. As an initial data, the program uses material constants, stress history mask, parameters of calculation theories and mechanical stress level. Stress data is automatically loaded from Femap model after accomplishing its static analysis. Libraries allow re-use of materials and stress history mask. SNCalculator posesses post-processing features, such as results saving, export of the results to Excel spreadsheet, export of the results to Femap FEM, stress cyclogram viewer.

Fatigue endurance calculations algorithm is based on three most widely spread in aviation industry techniques: quality of design analysis (developed by Loim V.B.), similarity theory analysis (developed by Kogaev V.P.) and fatigue rating theory analysis (developed by Strigius V.E.). The first two methods employ conception of effective stress concentration coefficient. The first method implements «quality» as a parameter, which is identified by experimental data and study of analogous structures data. Effective stress concentration coefficient is calculated for the second method by Kogaev’s theory of similarity. The third method uses fatigue rating, which is defined as maximal normal stress of zero-to-tension cycle for which fatigue life is equal 105 cycles with 50% probability and reliability level equal 0.5.

The paper describes the main steps of the abovementioned methods and presents schematic algorithm of fatigue life calculation realized by SNCalculator.


fatigue life, stress concentration, airframe, automation


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