PSI - Issue 18

Plekhov O. et al. / Procedia Structural Integrity 18 (2019) 711–718 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 4a shows crack growth rate obtained by equation (12) in semi-log scale. It can be noted that the increase of the applied load magnitude leads to the rise in the fatigue crack growth rate. The chosen force magnitudes span three orders of magnitudes of the fatigue crack rate and give us values for ( ) l a functions. The Fig. 4b shows continuous decreasing curve without pronounced endurance limit. 4. Conclusion The problem of the energy balance is one of the most important problems in the description of the irreversible deformation of metals. To solve this problem we proposed the thermodynamic potentials of media with defects and to develop a thermodynamic model of plastic deformation. The key point of the model is definition of defect-induced strain, which can be considered as a new thermodynamic variable. The application of the model allowed us to describe the energy storage in Armco iron under homogeneous plastic deformation. A good agreement between experimental and numerical results in the range of homogeneous plastic deformation was found. It has been shown that the initial stage of the plastic deformation is accompanied by increasing of storage energy rate. On the final stage of the quasistatic plastic deformation exhibits the decreasing of energy storage rate. This can be connected with a predominance of dissipative processes. The possibility of energy balance calculation gives us opportunity to evaluate fatigue crack growth rate on the base of the energy law and propose an algorithm for fatigue life assessment. The application of the algorithm is illustrated by the numerical simulation of the fatigue life of Ti-1Al-1Mn compact tension specimen. Results of the residual life simulation according to the proposed algorithm show continuous decreasing trend of the obtained curve and can be considered as first-order approximation of a fatigue life estimation of the CT-specimen. Acknowledgements The work was supported by the Russian Science Foundation (grant No. 19-77-30008). References Ivanova, V.S., Terentiev, V.F., 1975. Nature of fatigue of metals. Metalurgia, Moscow, pp. 456. Bever, M.B., Holt, D.L., Tichener, A.L., 1973. The stored energy of cold work. Progress in Materials Science 17, 5 – 173. Chrysochoos, A., Louche, H., 2000. An infrared image processing to analyse the calorific effects accompanying strain localization. International Journal of Engineering Science 38, 1759 – 1788. Meneghetti, G., Ricotta, M., 2016. Evaluating the heat energy dissipated in a small volume surrounding the tip of a fatigue crack. International Journal of Fatigue 92 (2), 605-615. Risitano, A., Risitano, G., 2013. Cumulative damage evaluation in multiple cycle fatigue tests taking into account energy parameters. International Journal of Fatigue 48, 214-222. Rosakis, P., Rosakis, A.J., Ravichandran, G., Hodowany, J., 2000. A thermodynamic internal variable model for the partitional of plastic work into heat and stored energy in metals. J. Mech. Phys. Solids 48, 581-607. Oliferuk, W., Maj, M., Raniecki B., 2004. Experimental analysis of energy storage rate components during tensile deformation of polycrystals. Mater. Sci. Eng. 374, 77-81. Ranganathan, N., Chalon, F., Meo, S., 2008. Some aspects of the energy based approach to fatigue crack propagation. International Journal of Fatigue 30 (10 – 11), 1921-1929. Benzerga, A.A., Brechet, Y., Needleman, A., Van der Giessen, E., 2005. The stored energy of cold work: predictions from discrete dislocation plasticity. Acta Materiala 53, 4765-4779. Aravas, N., Kim, K-S., Leckie, F.A., 1990. On the calculation of the stored energy of cold work. Journal of engineering materials and technology 112 (4), 465-470. Szczepinski, W., 2001. The stored energy in metals and the concept of residual microstresses in plasticity. Archives of mechanics 53, 615-629. Oliferuk, W., Maj, M., 2009. Stress-strain curve and stored energy during uniaxial deformation of polycrystals. European Journal of Mechanics A/Solids 28, 266-272. Chaboche, J-L., 1993. Cyclic viscoplastic constitutive equations. Journal of Applied Mechanics 60, 813-828. Vshivkov, А., Iziumova, A., Bar, U., Plekhov, O., 2016. Experimental study of heat dissipation at the crack tip during fatigue crack propagation. Fracture and Structural Integrity 35, 131-137.