PSI - Issue 20

S.V. Suknev / Procedia Structural Integrity 20 (2019) 30–36 S.V. Suknev / Structural Integrity Procedia 00 (2019) 000 – 000

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5. Conclusion The scope of application of existing nonlocal fracture criteria, distinguished for an additional material constant of the dimension of length, which characterizes its microstructure, is limited by the case of either brittle or quasi-brittle fracture with a small FPZ. To expand the scope of application of the criteria for cases of quasi-brittle fracture with a developed FPZ, it is proposed to abandon the hypothesis of the size of the FPZ as a material constant associated only with its microstructure. The characteristic length parameter underlying the nonlocal criteria should be considered as a material constant only in one particular case, which is brittle fracture. For quasi-brittle materials, this parameter is represented by the sum of two terms. The first of them characterizes the microstructure of the material itself and is a constant, and the second one reflects the formation of the zone of inelastic deformations and depends on the plastic properties of the material, geometry of the sample, and its loading conditions (boundary conditions). The proposed approach is used to develop new (modified) average stress and point stress criteria. The applicability of the criteria developed is verified on the problems of the fracture of plane samples with a circular hole in uniaxial tension and compression. It is shown that the proposed criteria well describe the experimental data on the fracture of quasi-brittle materials containing a stress riser. Acknowledgements The research was supported by the Russian Foundation for Basic Research under grant number 18-05-00323. References Fuentes, J.D., Cicero, S., Procopio I., 2017. Some default values to estimate the critical distance and their effect on structural integrity assessments. Theoretical and Applied Fracture Mechanics 90, 204 – 212. Justo, J., Castro, J., Cicero, S., Sánchez -Carro, M.A., Husillos, R., 2017. Notch effect on the fracture of several rocks: Application of the Theory of Critical Distances. Theoretical and Applied Fracture Mechanics 90, 251 – 258. Li, W., Susmel, L., Askes, H., Liao, F., Zhou, T., 2016. Assessing the integrity of steel structural components with stress raisers using the Theory of Critical Distances. Engineering Failure Analysis 70, 73 – 89. Negru, R., Marsavina, L., Voiconi, T., Linul, E., Filipescu, H., Belgiu, G., 2015. Application of TCD for brittle fracture of notched PUR materials. Theoretical and Applied Fracture Mechanics 80, 87 – 95. Neuber, H., 1937. Kerbspannungslehre, Grundlagen für eine genaue Spannungsrechnung, Springer-Verlag, Berlin. Novozhilov, V.V., 1969. On a necessary and sufficient criterion for brittle strength. Journal of Applied Mathematics and Mechanics 33, 201 – 210. Peterson, R.E., 1959. Notch sensitivity, in “Metal Fatigue” . In: McGraw Hill, New York, 293 – 306. Pipes, R.B., Wetherhold, R.C., Gillespie, J.W. (Jr.), 1979. Notched strength of composite materials. Journal of Composite Materials 13, 148 – 160. Suknev, S., 2018. Nonlocal criteria for brittle and quasi-brittle fracture of geomaterials and rocks. E3S Web of Conferences 56, 02003. Suknev, S.V., 2008. Formation of tensile fractures in the stress concentration zone in gypsum. Journal of Mining Science 44, 43 – 50. Tan, S.C., 1987. Laminated composites containing an elliptical opening. II. Experiment and model modification. Journal of Composite Materials 21, 949 – 968. Taylor, D., 2007. The Theory of Critical Distances: ANew Perspective in Fracture Mechanics, Elsevier, Oxford. Timoshenko, S.P., Goodier, J.N., 1970. Theory of Elasticity, 3rd edition, McGraw-Hill, New York. Vargiu, F., Sweeney, D., Firrao, D., Matteis, P., Taylor D., 2017. Implementation of the Theory of Critical Distances using mesh control. Theoretical and Applied Fracture Mechanics 92, 113 – 121. Wieghardt, K., 1907. Über das Spalten und Zerreisen elastischer Körper. Zeitschrift für Mathematik und Physik 55, 60 – 103.