PSI - Issue 13

B.A. Stratula et al. / Procedia Structural Integrity 13 (2018) 1402–1407 Author name / StructuralIntegrity Procedi 00 (2018) 000 – 000

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(a)

(b) Fig.2. VHCF experimental data for alloy ВТ3 -1: (a) tension-compression; (b) torsion

By using experimental data shown in Fig. 2-a the following parameters of generalized VHCF criterion are found 1100 B MPa   , 1 400 MPa    , 1 365 MPa    , 0.1 215 MPa   , 0.24    The obtained values of the parameters were used for the evaluation of the durability of the specimens in the VHCF reversal torsion tests. The comparison showed the proximity of the calculated and experimental results (Fig. 2-b). This confirms the possibility of using the generalized criterion for multiaxial fatigue failure in the VHCF mode and indicates the suitability of the proposed scheme for determining parameters for an approximate evaluation of the durability of structural elements. An analytical solution is obtained for the problem of determining the orientation of the critical plane for a multiaxial stress state in in-phase and anti-phase cyclic loading for the classical range of the LCF-HCF (the left branch of the bimodal fatigue curve). The generalization of the multiaxial fatigue fracture criterion to the case of very-high cycle fatigue is proposed. The procedure is proposed for determining the parameters of this generalized criterion from the results of uniaxial experiments for two coefficients of cycle asymmetry, and the critical plane of development of fatigue damages for a multiaxial stress state is determined. Bourago N.G., Zhuravlev A.B., Nikitin I.S., 2011. Models of multiaxial fatigue fracture and service life estimation of structural elements. Mechanics of Solids. Vol. 46, No. 6, pp. 828-838. Papadopoulos I.V., 2001. Long life fatigue under multiaxial loading. Int. J. of Fatigue. V.23, pp. 839-849. Carpinteri A., Spagnoli A., Vantadori S., 2011. Multiaxial assessment using a simplified critical plane-based criterion. Int. J. of Fatigue. V. 33, pp. 969 – 976. Findley W., 1959. A theory for the effect of mean stress on fatigue of metals under combined torsion and axial load or bending. J. of Eng. for Indust. pp. 301 – 306. Shanyavsky A.A., 2007. Modeling of Metal Fatigue fracture. Ufa, «Monografia». 498 p. Bathias C., Paris P.C., 2005. Gigacycle Fatigue in Mechanical Practice. New York, Dekker. Bathias C., 2006. Piezoelectric fatigue testing machines and devises. Int. J. of Fatigue. V. 26, pp. 1438−1445. Nikitin A., Palin-Luc T., Shanyavskiy A., Bathias C., 2012. Fatigue behavior of titanium alloy Ti-6Al-4Mo in bifurcation area at 20 kHz. Proceeding of ECF-19 conference, Kazan. Russia. Nikitin A., Bathias C., Palin-Luc T., 2015. A new piezoelectric fatigue testing machine in pure torsion for ultrasonic gigacycle fatigue tests: application to forged and extruded titanium alloys. Fatigue Fract. Eng. Mater. Struct. V. 38, pp. 1294 – 1304. References 3. Conclusions