Calculation-and-experimental estimation of the role of the frequency ratio in changing the endurance at two-frequency deformation modes

The cycle configuration at two-frequency loading regimes depends on the number of parameters including the absolute values of the frequencies and amplitudes of the low-frequency and high-frequency loads added during this mode, the ratio of their frequencies and amplitudes, as well as the phase shift between these harmonic components, the latter having a significant effect only with a small ratio of frequencies. Presence of such two-frequency regimes or service loading conditions for parts of machines and structures schematized by them can significantly reduce their endurance. Using the results of experimental studies of changes in the endurance of a two-frequency loading of specimens of cyclically stable, cyclically softened and cyclically hardened steels under rigid conditions we have shown that decrease in the endurance under the aforementioned conditions depends on the ratio of frequencies and amplitudes of operation low-frequency low-cycle and high-frequency vibration stresses, and, moreover, the higher the level of the ratios of amplitudes and frequencies of those stacked harmonic processes of loading the greater the effect. It is shown that estimation of such a decrease in the endurance compared to a single frequency loading equal in the total stress (strains) amplitudes can be carried out using an exponential expression coupling those endurances through a parameter (reduction factor) containing the ratio of frequencies and amplitudes of operation cyclic loads and characteristic of the material. The reduction is illustrated by a set of calculation-experimental curves on the corresponding diagrams for each of the considered types of materials and compared with the experimental data.

1. Kogaev V. P., Makhutov N. A., Gusenkov A. P. Calculations of machines and structures parts on strength and life-time. — Moscow: Mashinostroenie, 1985. — 224 p. [in Russian].

2. Makhutov N. A. Strength and safety: fundamental and applied researches. — Novosibirsk: Nauka, 2008. — 528 p. [in Russian].

3. Safety of Russia. Legal, social-economic and scientifically-engineering aspects. Management of service resource for highly risks objects. — Moscow: MGOF «Znanie», 2013. — 576 p. [in Russian].

4. Gadenin M. M. The multiple parameter analysis of safe service conditions and protectability of machines and structures by criteria of strength, resource and survivability / Probl. Bezopasn. Chrezvych. Situats. 2012. N 6. P. 22 – 36 [in Russian].

5. Strength and resource of water-moderated power reactors. The series «Researches of stresses and strength of nuclear reactors». — Moscow: Nauka, 1988. — 312 p. [in Russian].

6. Dynamics and strength of water-moderated power reactors. The series «Researches of stresses and strength of nuclear reactors». — Moscow: Nauka, 2004. – 440 p. [in Russian].

7. Strength and resource of liquid-fuel rocket engines. The series «Researches of rocket engines stresses and strength». — Moscow: Nauka, 2011. — 525 p. [in Russian].

8. Gadenin M. M., Romanov A. N. The arrangement for reproduction of a two-frequency loading mode on monofrequent fatigue test machines / Zavod. Lab. 1974. Vol. 40. N 4. P. 463 – 465 [in Russian].

9. Gadenin M. M. The method of cyclic tests automation on basis of URS 50/50 electrohydraulic test machine and IVK-2 measuring-computer complex / Zavod. Lab. 1985. Vol. 51. N 12. P. 61 – 65 [in Russian].

10. Gadenin M. M. Peculiarities of strains evolution and damages accumulation at two-frequency low-cycle loading and heightened temperatures / Mashinovedenie. 1976. N 1. P. 69 – 77 [in Russian].

11. Gadenin M. M. Resistance change to low-cycle deformation and fracture for two-frequency process of a loading / Abstracts of the XIII scientific conference «Problems of reliability and durability of structural elements in the engineering and construction industry». — Sverdlovsk: Sverdlovskii oblastnoi Sovet NTO, 1978. P. 5 – 6 [in Russian].

12. Gadenin M. M. Damage and life-time research of the structures in conditions of sin gle- and two-frequency loading modes using strain and energy approaches / Zavod. Lab. Diagn. Mater. 2017. Vol. 83. N 6. P. 44 – 52 [in Russian].

13. Locati L. Colloqufum on fatigue. Stockholm 1955. — Berlin – Gottingen – Heidelberg: Springer-Verlag, 1956. S. 160.

14. Gadenin M. M. Study of the effect of strain amplitude ratio at two-frequency cyclic loading / Zavod. Lab. Diagn. Mater. 2018. Vol. 84. N 12. P. 50 – 56 [in Russian].

15. Makhutov N. A., Gadenin M. M. Fatigue Resistance at Variation of Temperature-Time Factors / International Journal of Fracture. 2008. N 1 – 2(150). P. 105 – 127.

16. Safety of Russia. Legal, social-economic and scientifically-engineering aspects. Fundamental researches of engineering safety problems. — Moscow: MGOF «Znanie», 2013. — 576 p. [in Russian].

17. Gadenin M. M. Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states / Zavod. Lab. Diagn. Mater. 2012. Vol. 78. N 2. P. 58 – 63 [in Russian].

18. Makhutov N. A., Gadenin M. M. Resource estimation at combination of extreme low-cycle and vibrating impacts / Proc. of the 4th All-Russia Sci. and Techn. Conf. «Dynamics and strength of structures of air- and hydroelastic systems. Numerical methods». Moscow, November 14 – 15, 2017. — Moscow: Institut mashinovedeniya im. A. A. Blagonravova RAN, 2017. P. 40 – 41 [in Russian].