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Discrete approach to thermoelastic failure.

Dmit.D. Moiseenko( moisey-AT-rocketmail-DOT-com.gif )
Institute of Strength Physics and Material Science, Russian Academy of Science, Siberian Branch, Tomsk, Russia.

Most of experimental and numerical results show that material, during all stages of its loading, undergoes various structure transformations. These transformations connected with heat liberation and absorption. Along with band formation and damages generation [1-3], in heterogeneous material, for instance, consisting of soft matrix and hard inclusions, difference of material properties causes forming of high thermal gradients near interface zones. On the other hand, heat absorption or emission in local area leads to its deformation and forms complex stress fields in the specimen. Powerful heat flows can intensify damages generation and, as a result, to accelerate material failure. It is very significant for industrial applications relating to intensive heat propagation, particularly, in the case of dynamic loading. In the present study set of numerical experiments were undertaken. Taking into account close connection between thermodynamic and mechanical effects in such phenomena, two kinds of approaches were used for more thorough investigation. Namely, discrete method based on Cellular Automata approach and continual net method (coordinate split). At present, there are promising approaches describing fracture behavior, taking into account the random nature of local failure[4-5] On the base of previous investigations [6], model of "quantum-like" transition (QLT) of thermal energy was developed and tested on bistable CA approach. On the assumption of good results of this method, it was augmented by account of thermal expansion and stress-strain dependencies in each local area (i.e. in each single cellular automaton). In addition to the initial model, where heat "jumps" in automaton providing neighbors for energy emission or absorption, presented approach takes into account cracks generation and propagation along interfaces between areas with different properties. Localization of deformation preceding the fracture was studied as well. Comparison of the results obtained with experimental study shows good accordance, so it allows evolving this approach and using it in various industrial applications. References 1. V.E. Panin, Surface layers of solid as a mesoscopic structural level of deformation, Phys. Mesomech., 4, No. 3, p. 5. 2. E.Soppa, S. Schmauder, G. Fischer. Numerical and experimental investigations of the influence of particle alignment on shear band formation in Al/SiC // Proceedings of the 19th Riso International Symposium on Materials Science: "Modelling of Structure and Mechanics of Materials from Microscale to Product", 1998, p. 499 3. S.G. Psakhie, D.D. Moiseyenko, A.Yu. Smolin, et. al. The features of fracture of heterogeneous materials and frame structures. Potentialities of MCA design // Computational materials science, 1999, v.16, p. 333 4. L.L. Mishnaevsky Jr., S. Schmauder. Damage evolution and localization in heterogeneous materials under dynamical loading: stochastic mdelling // Computational mechanics, 1997, v.20, p. 89 5. L.L. Mishnaevsky Jr. Determination for the time-to-fracture of solids // International journal of fracture, 1996, v.79, p. 341 6. D.D. Moiseyenko, L.L. Mishnaevsky Jr., S. Schmauder. Discrete approach of heat flows applied to thermoelastic modeling // Proceedings of the 2nd All-Russian conference for young scientists: " Physical Mesomechanics of Materials", 1999, p. 81 (in Russian)