An Experimental Study of the Effect of “Small” Amplitude Loads on the Fatigue Lives of Steel Specimens

Aeronautical and Space-Rocket Engineering


Аuthors

Bessonov P. S.1*, Medvedsky A. L.1**, Svirskiy Y. A.1***, Shulga A. A.2****

1. Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI), 1, Zhukovsky str., Zhukovsky, Moscow Region, 140180, Russia
2. PJSC Yakovlev , 68, Leningradskiy prospect, Moscow, 125315, Russia

*e-mail: pavel-7-avia@mail.ru
**e-mail: aleksandr.medvedskiy@tsagi.ru
***e-mail: yury.svirsky@tsagi.ru
****e-mail: sozencz@mail.ru

Abstract

Aircraft is being subjected to loads of various nature and value during operation. Maneuvers and flight modes changes cause significant by value and relatively slowly (< 1 Hz) changing loads. Alongside with that the engine vibrations and noise, as well as aerodynamic phenomena such as flow separation lead to the occurrence of a large number of loads of “small” amplitudes and high mean values. The fatigue damaging computing with the widely accepted hypothesis of linear summation of fatigue damage, combined with the consideration of loading asymmetry, may contribute significantly to the total value of fatigue damaging. Correct estimations obtaining requires application of the “small” cycles considering method.
One of the passenger aircraft structural elements most susceptible to the “small” loads effect is the jet engine attachment to the aircraft wing, namely the pylon beam. Many components of the pylon beam are typically steel-made, in which context this material represents great interest in the present study.
The article provides a brief overview of regulatory documents and sources of open publications with recommendations for considering the “small” loads, and presents the results of fatigue tests on the 21 samples of a steel-made strip with an orifice, conducted under long-term programs of super multi-cycle loading with the total duration of over one year. The “small” cycles impact determining was being performed by comparing the results of the tensile tests by the two groups of the loading programs, i.e. with the “small” loads and without them. The amplitude of the “small” cycles was of 1/15 and 1/30 of the main cycle amplitude, and their number ranged from 225 to 2866 per loading block.
The article demonstrates that the “small” loads addition to the loading program did not lead to the statistically significant changes in the samples endurance. Meanwhile, the computed ratios of the endurances of the considered loading programs were 1.4 and 2.0. Thus, the difference exceeded 40%, demonstrating the need for the development of the techniques for the “small” loads considering. It is noted that inferences reliability increasing requires testing a larger number of samples.

Keywords:

super multi-cycle fatigue, “small” loads, “small” cycles, cyclic durability, fatigue tests, elementary metal samples, material endurance limit

References

  1. Palmgren A. Die Lebensdauer von Kugellagern. Zeitschrift des Vereines Deutscher Ingenieure. 1924(68):339-341.
  2. Miner MA. Cumulative Damage in Fatigue. Journal of Applied Mechanics. 1945;12(3):159-164.
  3. Agamirov LV, Raikher VL. Fatigue durability and damage to aircraft structures. Moscow: MEI; 2018. 134 p. (In Russ.).
  4. Oding IA. Permissible stresses in mechanical engineering and cyclic strength of metals. Moscow: Mashgiz, 1962. 260 p. (In Russ.).
  5. Bessolova OA, Raikher VL, Ustinov AS. Calculation of fatigue damage under cyclic and random loading with a non-zero average value. Uchenye zapiski TsAGI. 1989;XX(3):72-80. (In Russ.).
  6. Shulga AA, Barysheva DV. Influence of low-amplitude oscillation discarding in fatigue damage analysis. Materialy Mezhdunarodnoi molodezhnoi nauchnoi konferentsii "XXVI Tupolevskie chteniya (shkola molodykh uchenykh)" (November 09-10, 2023; Kazan). Kazan: IP Sagiev AR; 2023. p. 220-227. (In Russ.).
  7. Makhutov NA, Gadenin MM. Study of the generalized curves of the static and cyclic deformation, damage and fracture. Industrial laboratory. Diagnostics of materials. 2023;89(5):46-55. (In Russ.). DOI: 10.26896/1028-6861-2023-89-5-46-55
  8. Zavoychinskaya EB, Kablin AR. On high- and very high cycle fatigue of metals and alloys. Zhurnal tekhnicheskoi fiziki. 2023;93(12):1736-1739. (In Russ.). DOI: 10.61011/JTF.2023.12.56807.f241-23
  9. Nikitin AD, Nikitin IS. Experimental study of the very-high-cycle fatigue for titanium alloys. Naukoemkie tekhnologii. 2015;16(7):51-58. (In Russ.).
  10. Burago NG, Nikitin IS, Yushkovskiy PA, et al. Very-high-cycle fatigue at high-frequency oscillations of GTE compressor disc. Proceedings in Cybernetics. 2015(2):33-40. (In Russ.).
  11. Burago NG, Nikitin IS, Yakushev VL. Investigation of ultra-high-cycle fatigue during high-frequency vibrations of aircraft structural elements. Materialy XI Vserossiiskogo s"ezda po fundamental'nym problemam teoreticheskoi i prikladnoi mekhaniki (August 20-24, 2015; Kazan). Kazan: KFU; 2015. p. 621-622. (In Russ.). 
  12. Burago NG, Nikitin AD, Nikitin IS, et al. Criterion of fracture under supermultiple fatigue with determination of the critical plane. Materialy X Vserossiiskoi konferentsii po mekhanike deformiruemogo tverdogo tela (September 18-22, 2017; Samara). Samara: SamGTU; 2017. Vol. 1. p. 95-98. (In Russ.). DOI: 10.13140/RG.2.2.31161.26727
  13. Nikitin IS, Nikitin AD, Stratula BA. Damage development under very-high-cycle fatigue regime. PNRPU Mechanics Bulletin. 2020(4):120-129. (In Russ.). DOI: 10.15593/perm.mech/2020.4.11
  14. Nikitin IS, Burago NG, Nikitin AD. Damage and fatigue fracture of structural elements in various cyclic loading modes. Journal of Applied Mathematics and Mechanics. 2022;86(2):276-290. DOI: 10.31857/S0032823522020084
  15. Nikitin IS, Nikitin AD, Stratula BA. Fatigue failure and durability assessment of aircraft structural elements under combined cyclic loading. Materialy XIV Mezhdunarodnoi konferentsii po prikladnoi matematike i mekhanike v aerokosmicheskoi otrasli (AMMAI’2022; September 04-13, 2022; Alushta). Moscow: MAI; 2022. p. 215-217. (In Russ.).
  16. Strength calculation and testing. Representation of random loading of machine elements and structures and statistical evaluation of results. State Standard 25.101-83. Moscow: Mezhgosudarstvennyi standart; 1983. 21 p. (In Russ.).
  17. ASTM E1049-85. Standart Practices for Cycle Counting in Fatigue Analysis. ASTM International. 2023.
  18. Haibach E. Betriebsfestigkeit: Verfahren und Daten zur Bauteilberechnung. Berlin, German: Springer, 2006. 773 p.
  19. Barysheva DV, Gordon SV, Kim NV. et al. Development of a computational and experimental approach to the analysis of the durability of aircraft structures exposed to increased acoustic loads. Materialy Vserossiiskogo aeroakusticheskogo foruma (September 20-25, 2021; Gelendzhik). Zhukovskii: TsAGI; 2021. p. 217-219. (In Russ.).
  20. Bessonov PS. Program for determining the fatigue life of metal structures under accidental vibration and acoustic loading. Svidetel'stvo o gosudarstvennoi registratsii programmy dlya EVM RU 2021619411, 09.06.2021. (In Russ.).
  21. Niesłony A, Böhm M, Łagoda T, et al. The Use of Spectral Method for Fatigue Life Assessment for Non-Gaussian Random Loads. Acta Mechanica et Automatica. 2016;10(2):100-103. DOI: 10.1515/ama-2016-0016
  22. Irvine T, Larsen C. Modified Spectral Fatigue Methods for S-N Curves with MIL-HDBK-5J Coefficients. 14th European Conference on Spacecraft Structures, Materials and Environmental Testing (ECSSMET; September 27-30, 2016; Toulouse, France). Paris: ESA; 2016.
  23. Shul'ga AA, Barysheva DV, Medvedskii AL. Assessment of the contribution of the high-frequency component of the load to the fatigue damage of metal structures. Materialy II Nauchno-prakticheskoi konferentsii aspirantov (September 27, 2023; Zhukovskii). Zhukovskii: TsAGI; 2023. p. 39-46. (In Russ.).
  24. Shul'ga AA, Nikitin EA, Medvedskii AL. Assessment of the contribution of the high-frequency component of the load to the fatigue damage of aircraft structures by a single-stage method. Materialy IX Vserossiiskoi nauchno-tekhnicheskoi konferentsii "Problemy i perspektivy razvitiya aviatsii, nazemnogo transporta i energetiki" (October 03 04, 2024; Kazan). Kazan: KAI; 2024. p. 46-48. (In Russ.).
  25. Shul'ga AA, Nikitin EA, Medvedskii AL. Comparative analysis of spectral methods for calculating fatigue damage of structural elements of aviation equipment. Materialy III Nauchno-prakticheskoi konferentsii aspirantov (December 03, 2024; Zhukovsky). Zhukovsky: TsAGI; 2024. p. 110-118. (In Russ.).
  26. Mršnik M, Slavič J, Boltežar M. Vibration fatigue using modal decomposition. Mechanical Systems and Signal Processing. 2018;98(2):548-556. DOI: 10.1016/j.ymssp.2017.03.052
  27. Slavič J, Boltežar M, Mršnik M, et al. Vibration Fatigue by Spectral Methods: from Structural Dynamics to Fatigue Damage. Theory and Experiments. Vibration fatigue by spectral methods. Amsterdam: Elsevier, 2020. 230 p.
  28. Zorman A, Slavič J, Boltežar M. Vibration fatigue by spectral methods—A review with open-source support. Mechanical Systems and Signal Processing. 2023;190(2):110-149. DOI: 10.1016/j.ymssp.2023.110149
  29. Bokhoeva LA, Kurokhtin VY, Perevalov AV, et al. Helicopter structural elements and components fatigue resistance tests. Aerospace MAI Journal. 2017;24(1):7-16. (In Russ.).
  30. Standards of airworthiness of NLG 25 transport category aircraft. Moscow: Federal'noe Agentstvo vozdushnogo transporta; 2022. 355 p. (In Russ.).
  31. Emelin A. Testing statistical hypotheses. (In Russ.). URL: http://www.mathprofi.ru/proverka_statisticheskih_gipotez.html
  32. Emelin A. Statistical hypotheses. (In Russ.). URL: http://www.mathprofi.ru/statisticheskie_gipotezy.html#gs

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