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10th anniversary of the Journal “Physical Mesomechanics”
From Editor / Physical Mesomechanics 11 3–4 (2008) 101–104
10th anniversary of the Journal Physical Mesomechanics Up to the mid-20th century problems of plastic deformation and fracture of solids have been studied exclusively on the basis of phenomenological approaches of continuum mechanics. They are effective for a wide range of engineering tasks at the macroscale level. Microscale physical approaches were required to understand mechanisms of plastic deformation and fracture. Physicists make a breakthrough into the microworld of a deformed solid in the 50ies of the 20th century when electron microscopy was employed to study the fine crystal structure. For the next half century the physics of plasticity and strength enjoyed a rapid developed due to the intensive investigation of generation, motion, and self-organization of dislocations as the major type of strain-induced defects. The modern theory of crystal dislocations allows a qualitative description of many behavior mechanisms of solids under different loading conditions. It seemed at first that macroscopic characteristics of a deformed solid could be calculated when overcoming purely mathematical difficulties of describing the intricate behavior of dislocation ensembles at the microlevel. Up to now, however, the stressstrain curve has not been calculated using only microscopic notions of dislocation theory. All attempts to directly pass from the microscopic approaches of physics to the macroscopic approaches of mechanics have failed. It became evident to the early 80ies of the last century that the deformed solid is a multilevel system and cannot be described by one-level approaches of dislocation theory (microscale level) or continuum mechanics (macroscale level). There was a need for a new paradigm based on the self-consistent description of deformation mechanisms in the entire hierarchy of structural scale levels of heterogeneous solids. A new approach was first formulated in paper [1] as the conception of structural levels of deformation of solids. Later this conception was developed in detail in a number of reviews and monographs [28, etc.] that laid the groundwork for a fundamentally new methodology for describing plastic deformation and fracture of solids. The new methodology assumed first as hotly debatable has enjoyed a convincing experimental and theoretical justification for the last quarter century. It underlies the generation and intendoi:10.1016/j.physme.2008.07.009
sive development of a new science, namely, physical mesomechanics. The first six International Conferences on physical mesomechanics have been hosted by the Institute of Strength Physics and Materials Science SB RAS (in Tomsk and near Baikal lake). At the International Conference Mesofracture96 in Tomsk it was decided to hold these conferences in different countries and to publish the International Journal Physical Mesomechanics. The first issue of the new journal was published in 1998 in Russian and English and represented to the scientific community at the International Conference Mesomechanics98 in Tel Aviv, Israel. Since 1998 several conceptually new principles have been theoretically and experimentally validated in physical mesomechanics, which change radically the conventional methodology for description of plastic deformation and fracture of solids. Though deformation and fracture of solids are described by different methods in physics (based on the theory of lattice defects) and continuum mechanics (phenomenological description), their methodologies are qualitatively similar. They are based on force models of shear deformation under average applied stresses. Stress and strain tensors are symmetric, scalar dislocation density alone is taken into account, deformation is described as the superposition of the translational motion of lattice defects. This approach aims at describing the yield stress and strain hardening of the material during its plastic flow and fracture. The welldeveloped theory of dislocations gives no consideration to their cores and calculates elastic fields of interacting dislocations within the initial crystal lattice. In fact, this amounts to solid mechanics at the microscale level. The physics of dislocations should describe primarily the generation of dislocation cores as local structural transformations in the crystal lattice and formation of dissipative substructures associated with 3D carriers of plastic flow. However, these questions are not studied in dislocation theory. The introduction of disclinations into consideration makes it possible to account for the material fragmentation at the mesoscale level with the methodology of force models in the field of average applied stresses to be retained.
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From Editor / Physical Mesomechanics 11 3–4 (2008) 101–104
Actually, all types of crystal defects should be considered as local metastable structures formed in differentscale zones of stress concentrators. Therefore, the physics of plastic deformation should be studied using synergetic laws for the behavior of highly-nonequilibrium heterogeneous systems that are subjected to local structural transformations and equilibrate due to step-by-step local structural transformation in fields of internal stress gradients. A crystal under deformation changes continuously its initial crystal structure, which results in dissipative substructures at different mesoscale levels. It is important that deformation under specified boundary conditions occurs by the shear + rotation scheme [18]. Therefore, dissipative substructures are of functional character, which is manifested in the formation of 3D carriers of plastic flow in the mechanical vortex field. Structural transformations in the deformed crystal develop selfconsistently in the hierarchy of multiple scale levels and should be described by field theories of defects in a loaded solid. The field theories should describe sources of straininduced defects, plastic deformation development by the shear + rotation scheme, formation of vortex dissipative structures, and self-consistency of plastic shears in the hierarchy of all structural levels of deformation. These issues lie at the interface of solid state physics and solid mechanics. They have become the subject of investigation in physical mesomechanics. Special attention in physical mesomechanics as a new paradigm should be given to the semantics of the terms structural levels of deformation and scale levels of deformation. The term scale levels proposes a distinct classification of sizes in the hierarchy of scales: nano, micro, meso, and macro. This classification defines scales of the internal structure, yet being essentially ambiguous due to its dependence on the object of investigation. In the deformed crystal the mesoscale is conventionally assumed to be dozen and hundred micrometers while in geotectonics it equals hundred and thousand kilometers. The methodology of physical mesomechanics refers all structural levels of deformation to mesoscopic scales independently of their sizes. In physical mesomechanics the term mesoscopic has the meaning intermediate between the solid as a continuum and its specific crystal lattice. In recent year, nanostructures and nanomaterials are the subject of considerable discussion in the literature. In the conventional scale hierarchy they should be considered at the nanoscale level. According to the physical mesomechanics classification they belong to the mesoscale level since being nonequilibrium mesosubstructures in the initial equilibrium crystal. It should be underlined that dislocation theory operates with defects in the equilibrium crystal lattice. Their motion is described under the action of average applied stresses and classified as the microscale level of deformation. Meanwhile, dislocation scores as fragments of the altered structure are generated only in local zones of stress microcon-
centrators and plastic shears are particularly localized. In fact, the first mesoscopic substructural level of deformation is formed within the microscale level. Its evolution in the vortex field of internal stresses ends with the formation of a disoriented cellular dislocation substructure where each cell is a new mesoscopic carrier of deformation by the shear + rotation pattern. In other words, mesoscopic structural levels of deformation, that play an important functional role unusual for the initial crystal structure, are formed already at the microscale. Localized deformation mesobands formed in the deformed specimen at high strains and propagating in noncrystallographic directions induce the specimen fragmentation at the higher scale level meso II. This corresponds to the shear stability loss of the entire internal structure of the specimen while its global shear stability as a whole is retained. At this stage of plastic flow a new mesoscopic structural level of deformation and its new carriers are formed. Mesovolumes at the structural level meso II move self-consistently with all lower mesoscopic structural levels of deformation. Such a multilevel self-consistent process is in principle impossible to describe by the conventional methodology of dislocation theory that operates with defect motion in the invariable structure of the initial solid. Much less can be done by continuum mechanics that considers neither the internal structure of the initial solid nor its continuous evolution under plastic deformation. A new paradigm of physical mesomechanics suggests a qualitatively new approach to describing fracture of a loaded solid. In the classical physics and mechanics of fracture the problem of crack generation is still unsettled. The theory of crack propagation assumes critical stress concentration at the crack tip and the degree of damage in the front of the crack tip as basic parameters. Physical mesomechanics considers fracture as the final deformation stage related to the global shear stability loss of the loaded solid as a whole. Rotational modes of deformation are of principle importance in fracture. They govern crack formation as continuity violation of the material in uncompensated rotations of 3D mesostructural elements of deformation. Translational propagation of the crack causes local rotations of mesovolumes in its path, which determine critical stress concentrators at the crack tip required for its propagation. Besides, interatomic bond rupture during crack propagation is due to local structural-phase transition [911]. According to the vivid expression of Prof. G. Sih, the atomic mechanism of crack propagation should be described using notions of nanochemistry [9]. It is a radically new idea in the physical mesomechanics of fracture, which reflects the multilevel approach to describing fracture of solids. The multilevel approach leads authors [10] to the conclusion that under ductile fracture of a solid wave-like selforganization of two parallel (as a dipole) or conjugate localized deformation macrobands that govern opposite-sign
From Editor / Physical Mesomechanics 11 3–4 (2008) ( 101–104 ) y
rotations of the material develops in the neck. Uncompensated rotations at lower mesoscale levels govern the crack formation as the accommodative rotational mode of deformation in the neck. Thus, the multilevel description of plastic deformation and fracture of solids should be based on three principles: 1. Identification of plastic flow mechanisms at different structural scale levels of deformation, which change cardinally the initial internal structure of a solid and induce the formation of dissipative substructures as mesoscopic carriers of plastic deformation. 2. Determination of the relation between the external action, change in the initial internal structure, formation of the hierarchy of mesoscopic self-consistent structural levels of deformation, and their induced mechanical fields. 3. The synergetic approach to describing a deformed solid as a nonequilibrium multilevel medium that loses its shear stability at bifurcation points at different structural scale levels and fails at the global shear stability loss at the macroscale level. These principles underlie physical mesomechanics as a new paradigm at the interface of solid state physics and solid mechanics. Mention briefly greatest achievements in physical mesomechanics for the last decade. 1. The multilevel approach to the description of plastic deformation and fracture of solids became generally recognized in both solid mechanics and solid state physics. 2. Deformation mechanisms have been intensively investigated experimentally at different scale levels. Of use are new generation devices combining high resolution and scanning of large surface areas of a deformed solid (atomicforce and scanning-tunneling microscopy, scanning and transmission electron microscopy, laser profilometry, optical television measuring systems, speckle interferometry, thermal imagers, probe analysis by Quanta 200 3D devices, etc). This makes it possible not only to reveal and describe quantitatively new deformation mechanisms [1121, etc.] but also to establish the scale invariance of their reduced parameters [2228, etc.] 3. Different-scale deformation and fracture mechanisms were described theoretically using 3D models. Nano- and microscale levels are simulated mainly by molecular dynamics methods as well as by the excitable cellular automata method. Mesoscale levels between micro- and macroscales are described by the movable cellular automata method and by methods of mechanics of structured media. Important steps were taken to develop hybrid models uniting methods of the continuous and discrete mechanics of a deformed solid. Mechanisms of scale-invariant block fracture of solids were found. 4. It was revealed that all internal interfaces are functionally important for the generation of strain-induced defects of different scale levels and their wave-like propagation as a particularly relaxation process [7, 8, 11, 29, 30]. The ef-
There is plenty of room at the bottom: An invitation to enter a new field of physics. Nobel Prize Laureate R.P. Feynman
fect of chessboard-like distribution of normal and tangential stresses at the interface of dissimilar media in fields of various external actions (mechanical, thermal, electromagnetic or other) is experimentally found and theoretically justified [31, 32]. The chessboard-like mesoeffect for the interface appears at the conjugation of various media of organic and inorganic nature [33]. It governs nonlinear wave processes of mass-transfer in various heterogeneous media. Transfer flows through interfaces are based on structural phase transitions of nanostructured states in local zones of hydrostatic tension in the chessboard-like structure at and near interfaces. 5. Much promise for the multilevel description of a deformed solid is provided by physical mesomechanics that concludes that all mechanisms of plastic deformation and fracture of solids as local structural transformations in different-scale zones of stress concentrators are common in nature [11]. According to [11], all types of strain-induced defects are generated in local zones of hydrostatic tension near stress concentrators, where the local nonequilibrium thermodynamic Gibbs potential should be taken into account. The atomic structure of all cores of strain-induced defects can be described in terms of nanoclusters of different atomic configuration. At the stable crystal lattice nonequilibrium atomic nanoclusters propagate as solitons in the form of dislocation cores. In a highly nonequilibrium crystal they propagate collectively as nonlinear waves of localized plastic deformation that manifest themselves as meso- and macrobands of localized shear. This approach
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From Editor / Physical Mesomechanics 11 3–4 (2008) 101–104
makes possible a generalized multilevel model for any materials and loading conditions using fundamental notions of the theory of nonequilibrium structural-phase transitions. The multilevel approach for a deformed solid considers the self-consistent interaction of the following subsystems: electron subsystem, surface layers, all internal interfaces, crystal structure of the base and constituent phases of the material, and lattice defects. The 21st century is referred to as a century of nanostructured materials and nanotechnologies. Their related tasks will be solved using the physical mesomechanics methodology that is based on the multilevel approach and operates with nanoclusters of different atomic configuration in local fields of stress concentrators at different structural scale levels. Physical mesomechanics provides the basis for the successful development of new computer technologies of multilevel simulation and design of new generation materials. The journal editorial board decided to dedicate the anniversary issue to invited papers of known scientists that actively develop physical mesomechnaics. The submitted papers exceed considerably the size of one issue and will be published in two anniversary issues. They will include methodological works and those on concrete problems of physical mesomechanics based on the multilevel approach. References [1] V.E. Panin, Yu.V. Grinyaev, T.F. Elsukova, and A.G. Ivanchin, Structural levels of deformation in solids, Russ. Phys. J., 25, No. 6 (1982) 479. [2] V.E. Panin, V.A. Likhachev, and Yu.V. Grinyaev, Structural Levels of Deformation in Solids, Nauka, Novosibirsk, 1985 (in Russian). [3] V.E. Panin (Ed.), Structural Levels of Plastic Deformation and Fracture, Nauka, Novosibirsk, 1990 (in Russian). [4] V.E. Panin (Ed.), Physical Mesomechanics and Computer-Aided Design of Materials, Nauka, Novosibirsk, V. 1, 2 (1995) (in Russian). [5] V.E. Panin (Ed.), Physical Mesomechanics of Heterogeneous Media and Computer-Aided Design of Materials, Cambridge Interscience Publishing, Cambridge, 1998. [6] V.E. Panin, Overview on mesomechanics of plastic deformation and fracture of solids, Theor. Appl. Fract. Mech., 30, No. 1 (1998) 1. [7] V.E. Panin, Synergetic principles of physical mesomechanics, Phys. Mesomech, 3, No. 6 (2000) 5. [8] V.E. Panin and Yu.V. Grinyaev, Physical mesomechanics: a new paradigm at the interface of solid state physics and solid mechanics, Phys. Mesomech., 6, No. 4 (2003) 7 [9] G.C. Sih, Crack tip system for environment assisted failure of nuclear reactor alloys: Multiscaling from atomic to macro via mesos, J. Press. Syst., No. 3 (2005) 1. [10] V.E. Panin, Yu.V. Grinyaev, and A.V. Panin, Field theory of multilevel plastic flow in the neck of a deformed solid, Fiz. Mezomekh., 10, No. 5 (2007) 5 (in Russian). [11] V.E. Panin and V.E. Egorushkin, Nonequilibrium thermodynamics of a deformed solid as a multiscale system. Corpuscular-wave dualism of plastic shear, Phys. Mesomech., 11, No. 34 (2008) 109. [12] A.N. Tyumentsev, A.D. Korotaev, and Yu.P. Pinzhin, Highly defective structural states, fields of local internal stresses and cooperative mesoscopic mechanisms of crystal deformation and reorientation in nanostructured metal materials, Phys. Mesomech., 7, Nos. 34 (2004) 31.
[13] A.N. Tyumentsev, I.Yu. Litovchenko, N.V. Shevchenko, S.L. Girsova, and A.D. Korotaev, Crystal-lattice distortions upon the formation of localized-deformation bands via combined forward-plus-reverse martensitic transformations, Phys. Met. Metallogr., 101, No. 3 (2006) 296. [14] A.V. Panin, Nonlinear waves of localized plastic flow in nanostructured surface layers of solids and thin films, Phys. Mesomech., 8, Nos. 34 (2005) 5. [15] E.E. Deryugin, V.E. Panin, S. Schmauder, and I.V. Storozhenko, Effects of deformation localization in Al-based composites with Al2O3 inclusions, Phys. Mesomech., 4, No. 3 (2001) 35. [16] P.V. Kuznetsov and V.E. Panin, Direct observation of flows of defects and of nm-range localization of deformation on duralumin surface with the aid of scanning tunnel and atom force microscopes, Phys. Mesomech., 3, No. 2 (2000) 85. [17] V.E. Panin, T.F. Elsukova, V.E. Egorushkin, O.Yu. Vaulina, and Yu.I. Pochivalov, Nonlinear wave effects of curvature solitons in surface layers of high-purity aluminum polycrystals under severe plastic deformation. I. Experiment, Phys. Mesomech., 11, Nos. 12 (2008) 63. [18] L.S. Derevyagina, V.E. Panin, and A.I. Gordienko, Self-organization of plastic shears in localized deformation macrobands in the neck of high-strength polycrystals, its role in material fracture under uniaxial tension, Phys, Mesomech., 11, Nos. 12 (2008) 51. [19] S.G. Psakhie, G.P. Ostermeyer, A.I. Dmitriev, E.V. Shilko, A.Yu. Smolin, and S.Yu. Korostelev, Method of movable cellular automata as a new trend of discrete computational mechanics. I. Theoretical description, Phys. Mesomech., 3, No. 2 (2000) 5. [20] S.G. Psakhie, K.P. Zolnikov, and D.S. Kryzhevich, Elementary atomistic mechanism of crystal plasticity, Phys. Lett. A, 367 (2007) 250. [21] I.F. Golovnev, E.I. Golovneva, and V.M. Fomin, Molecular dynamics calculation of thermodynamic properties of nanostructures, Phys, Mesomech., 11, Nos. 12 (2008) 19. [22] V.L. Popov and E. Kröner, On the role of scaling in the theory of elastoplasticity, Phys. Mesomech., 1, No. 1 (1998) 103. [23] A. Godfrey and D.A. Hughes, Scaling of the spacing of deformation induced dislocation boundaries, Acta Mater., 48 (2000) 1897. [24] J.P. Sethna, V.R. Coffman, and E. Dember, Scaling in plasticityinduced cell-boundary microstructure: Fragmentation and rotational diffusion, Phys. Rev. B, 67 (2003) 184. [25] Yu.G. Gordienko, E.E. Zasimchuk, and T.V. Turchak, Scaling of structural parameters and mechanical properties of metals and alloys, Phys. Mesomech., 10, Nos. 34 (2007) 129. [26] O.B. Naimark, Yu.V. Bayandin, V.A. Leontiev, and S.L. Permyakov, On thermodynamics of structural-scaling transitions in solids under plastic deformation, Phys. Mesomech., 8, Nos. 56 (2005) 21. [27] V.E. Panin, A.V. Panin, V.P. Sergeev, and A.R. Shugurov, Scaling effects in structural-phase self-organization at the thin film substrate interface, Phys. Mesomech., 10, Nos. 34, (2007) 117. [28] P.V. Makarov, Evolutionary nature of destruction of solids and media, Phys. Mesomech., 10, Nos. 34, (2007) 134. [29] V.E. Panin, V.M. Fomin, and V.M. Titov, Physical principles of mesomechanics of surface layers and internal interfaces in a solid under deformation, Phys. Mesomech., 6, No. 3 (2003) 5. [30] Surface Layers and Internal Interfaces in Heterogeneous Materials, Ed. by V.E. Panin, Izd-vo SO RAN, Novosibirsk, 2006 (in Russian). [31] V.E. Panin, A.V. Panin, D.D. Moiseenko, Physical mesomechanics of a deformed solid as a multilevel system. II. Chessboard-like mesoeffect of the interface in heterogeneous media in external fields, Phys. Mesomech., 10, Nos. 12 (2007) 5. [32] V.E. Panin, A.V. Panin, D.D. Moiseenko, T.F. Elsukova, O.Yu. Kuzina, and P.V. Maksimov, The chess-board effect in the stressstrain distribution at interfaces of a loaded solid, Phys. Dokl., 51, No. 8 (2006) 408. [33] L.E. Panin and V.E. Panin, Chessboard effect and mass transfer in interfacial media of organic and inorganic nature, Phys. Mesomech., 11, Nos. 12 (2008) 5. Editor of the anniversary issues Academician V.E. Panin
10th anniversary of the Journal Physical Mesomechanics Up to the mid-20th century problems of plastic deformation and fracture of solids have been studied exclusively on the basis of phenomenological approaches of continuum mechanics. They are effective for a wide range of engineering tasks at the macroscale level. Microscale physical approaches were required to understand mechanisms of plastic deformation and fracture. Physicists make a breakthrough into the microworld of a deformed solid in the 50ies of the 20th century when electron microscopy was employed to study the fine crystal structure. For the next half century the physics of plasticity and strength enjoyed a rapid developed due to the intensive investigation of generation, motion, and self-organization of dislocations as the major type of strain-induced defects. The modern theory of crystal dislocations allows a qualitative description of many behavior mechanisms of solids under different loading conditions. It seemed at first that macroscopic characteristics of a deformed solid could be calculated when overcoming purely mathematical difficulties of describing the intricate behavior of dislocation ensembles at the microlevel. Up to now, however, the stressstrain curve has not been calculated using only microscopic notions of dislocation theory. All attempts to directly pass from the microscopic approaches of physics to the macroscopic approaches of mechanics have failed. It became evident to the early 80ies of the last century that the deformed solid is a multilevel system and cannot be described by one-level approaches of dislocation theory (microscale level) or continuum mechanics (macroscale level). There was a need for a new paradigm based on the self-consistent description of deformation mechanisms in the entire hierarchy of structural scale levels of heterogeneous solids. A new approach was first formulated in paper [1] as the conception of structural levels of deformation of solids. Later this conception was developed in detail in a number of reviews and monographs [28, etc.] that laid the groundwork for a fundamentally new methodology for describing plastic deformation and fracture of solids. The new methodology assumed first as hotly debatable has enjoyed a convincing experimental and theoretical justification for the last quarter century. It underlies the generation and intendoi:10.1016/j.physme.2008.07.009
sive development of a new science, namely, physical mesomechanics. The first six International Conferences on physical mesomechanics have been hosted by the Institute of Strength Physics and Materials Science SB RAS (in Tomsk and near Baikal lake). At the International Conference Mesofracture96 in Tomsk it was decided to hold these conferences in different countries and to publish the International Journal Physical Mesomechanics. The first issue of the new journal was published in 1998 in Russian and English and represented to the scientific community at the International Conference Mesomechanics98 in Tel Aviv, Israel. Since 1998 several conceptually new principles have been theoretically and experimentally validated in physical mesomechanics, which change radically the conventional methodology for description of plastic deformation and fracture of solids. Though deformation and fracture of solids are described by different methods in physics (based on the theory of lattice defects) and continuum mechanics (phenomenological description), their methodologies are qualitatively similar. They are based on force models of shear deformation under average applied stresses. Stress and strain tensors are symmetric, scalar dislocation density alone is taken into account, deformation is described as the superposition of the translational motion of lattice defects. This approach aims at describing the yield stress and strain hardening of the material during its plastic flow and fracture. The welldeveloped theory of dislocations gives no consideration to their cores and calculates elastic fields of interacting dislocations within the initial crystal lattice. In fact, this amounts to solid mechanics at the microscale level. The physics of dislocations should describe primarily the generation of dislocation cores as local structural transformations in the crystal lattice and formation of dissipative substructures associated with 3D carriers of plastic flow. However, these questions are not studied in dislocation theory. The introduction of disclinations into consideration makes it possible to account for the material fragmentation at the mesoscale level with the methodology of force models in the field of average applied stresses to be retained.
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From Editor / Physical Mesomechanics 11 3–4 (2008) 101–104
Actually, all types of crystal defects should be considered as local metastable structures formed in differentscale zones of stress concentrators. Therefore, the physics of plastic deformation should be studied using synergetic laws for the behavior of highly-nonequilibrium heterogeneous systems that are subjected to local structural transformations and equilibrate due to step-by-step local structural transformation in fields of internal stress gradients. A crystal under deformation changes continuously its initial crystal structure, which results in dissipative substructures at different mesoscale levels. It is important that deformation under specified boundary conditions occurs by the shear + rotation scheme [18]. Therefore, dissipative substructures are of functional character, which is manifested in the formation of 3D carriers of plastic flow in the mechanical vortex field. Structural transformations in the deformed crystal develop selfconsistently in the hierarchy of multiple scale levels and should be described by field theories of defects in a loaded solid. The field theories should describe sources of straininduced defects, plastic deformation development by the shear + rotation scheme, formation of vortex dissipative structures, and self-consistency of plastic shears in the hierarchy of all structural levels of deformation. These issues lie at the interface of solid state physics and solid mechanics. They have become the subject of investigation in physical mesomechanics. Special attention in physical mesomechanics as a new paradigm should be given to the semantics of the terms structural levels of deformation and scale levels of deformation. The term scale levels proposes a distinct classification of sizes in the hierarchy of scales: nano, micro, meso, and macro. This classification defines scales of the internal structure, yet being essentially ambiguous due to its dependence on the object of investigation. In the deformed crystal the mesoscale is conventionally assumed to be dozen and hundred micrometers while in geotectonics it equals hundred and thousand kilometers. The methodology of physical mesomechanics refers all structural levels of deformation to mesoscopic scales independently of their sizes. In physical mesomechanics the term mesoscopic has the meaning intermediate between the solid as a continuum and its specific crystal lattice. In recent year, nanostructures and nanomaterials are the subject of considerable discussion in the literature. In the conventional scale hierarchy they should be considered at the nanoscale level. According to the physical mesomechanics classification they belong to the mesoscale level since being nonequilibrium mesosubstructures in the initial equilibrium crystal. It should be underlined that dislocation theory operates with defects in the equilibrium crystal lattice. Their motion is described under the action of average applied stresses and classified as the microscale level of deformation. Meanwhile, dislocation scores as fragments of the altered structure are generated only in local zones of stress microcon-
centrators and plastic shears are particularly localized. In fact, the first mesoscopic substructural level of deformation is formed within the microscale level. Its evolution in the vortex field of internal stresses ends with the formation of a disoriented cellular dislocation substructure where each cell is a new mesoscopic carrier of deformation by the shear + rotation pattern. In other words, mesoscopic structural levels of deformation, that play an important functional role unusual for the initial crystal structure, are formed already at the microscale. Localized deformation mesobands formed in the deformed specimen at high strains and propagating in noncrystallographic directions induce the specimen fragmentation at the higher scale level meso II. This corresponds to the shear stability loss of the entire internal structure of the specimen while its global shear stability as a whole is retained. At this stage of plastic flow a new mesoscopic structural level of deformation and its new carriers are formed. Mesovolumes at the structural level meso II move self-consistently with all lower mesoscopic structural levels of deformation. Such a multilevel self-consistent process is in principle impossible to describe by the conventional methodology of dislocation theory that operates with defect motion in the invariable structure of the initial solid. Much less can be done by continuum mechanics that considers neither the internal structure of the initial solid nor its continuous evolution under plastic deformation. A new paradigm of physical mesomechanics suggests a qualitatively new approach to describing fracture of a loaded solid. In the classical physics and mechanics of fracture the problem of crack generation is still unsettled. The theory of crack propagation assumes critical stress concentration at the crack tip and the degree of damage in the front of the crack tip as basic parameters. Physical mesomechanics considers fracture as the final deformation stage related to the global shear stability loss of the loaded solid as a whole. Rotational modes of deformation are of principle importance in fracture. They govern crack formation as continuity violation of the material in uncompensated rotations of 3D mesostructural elements of deformation. Translational propagation of the crack causes local rotations of mesovolumes in its path, which determine critical stress concentrators at the crack tip required for its propagation. Besides, interatomic bond rupture during crack propagation is due to local structural-phase transition [911]. According to the vivid expression of Prof. G. Sih, the atomic mechanism of crack propagation should be described using notions of nanochemistry [9]. It is a radically new idea in the physical mesomechanics of fracture, which reflects the multilevel approach to describing fracture of solids. The multilevel approach leads authors [10] to the conclusion that under ductile fracture of a solid wave-like selforganization of two parallel (as a dipole) or conjugate localized deformation macrobands that govern opposite-sign
From Editor / Physical Mesomechanics 11 3–4 (2008) ( 101–104 ) y
rotations of the material develops in the neck. Uncompensated rotations at lower mesoscale levels govern the crack formation as the accommodative rotational mode of deformation in the neck. Thus, the multilevel description of plastic deformation and fracture of solids should be based on three principles: 1. Identification of plastic flow mechanisms at different structural scale levels of deformation, which change cardinally the initial internal structure of a solid and induce the formation of dissipative substructures as mesoscopic carriers of plastic deformation. 2. Determination of the relation between the external action, change in the initial internal structure, formation of the hierarchy of mesoscopic self-consistent structural levels of deformation, and their induced mechanical fields. 3. The synergetic approach to describing a deformed solid as a nonequilibrium multilevel medium that loses its shear stability at bifurcation points at different structural scale levels and fails at the global shear stability loss at the macroscale level. These principles underlie physical mesomechanics as a new paradigm at the interface of solid state physics and solid mechanics. Mention briefly greatest achievements in physical mesomechanics for the last decade. 1. The multilevel approach to the description of plastic deformation and fracture of solids became generally recognized in both solid mechanics and solid state physics. 2. Deformation mechanisms have been intensively investigated experimentally at different scale levels. Of use are new generation devices combining high resolution and scanning of large surface areas of a deformed solid (atomicforce and scanning-tunneling microscopy, scanning and transmission electron microscopy, laser profilometry, optical television measuring systems, speckle interferometry, thermal imagers, probe analysis by Quanta 200 3D devices, etc). This makes it possible not only to reveal and describe quantitatively new deformation mechanisms [1121, etc.] but also to establish the scale invariance of their reduced parameters [2228, etc.] 3. Different-scale deformation and fracture mechanisms were described theoretically using 3D models. Nano- and microscale levels are simulated mainly by molecular dynamics methods as well as by the excitable cellular automata method. Mesoscale levels between micro- and macroscales are described by the movable cellular automata method and by methods of mechanics of structured media. Important steps were taken to develop hybrid models uniting methods of the continuous and discrete mechanics of a deformed solid. Mechanisms of scale-invariant block fracture of solids were found. 4. It was revealed that all internal interfaces are functionally important for the generation of strain-induced defects of different scale levels and their wave-like propagation as a particularly relaxation process [7, 8, 11, 29, 30]. The ef-
There is plenty of room at the bottom: An invitation to enter a new field of physics. Nobel Prize Laureate R.P. Feynman
fect of chessboard-like distribution of normal and tangential stresses at the interface of dissimilar media in fields of various external actions (mechanical, thermal, electromagnetic or other) is experimentally found and theoretically justified [31, 32]. The chessboard-like mesoeffect for the interface appears at the conjugation of various media of organic and inorganic nature [33]. It governs nonlinear wave processes of mass-transfer in various heterogeneous media. Transfer flows through interfaces are based on structural phase transitions of nanostructured states in local zones of hydrostatic tension in the chessboard-like structure at and near interfaces. 5. Much promise for the multilevel description of a deformed solid is provided by physical mesomechanics that concludes that all mechanisms of plastic deformation and fracture of solids as local structural transformations in different-scale zones of stress concentrators are common in nature [11]. According to [11], all types of strain-induced defects are generated in local zones of hydrostatic tension near stress concentrators, where the local nonequilibrium thermodynamic Gibbs potential should be taken into account. The atomic structure of all cores of strain-induced defects can be described in terms of nanoclusters of different atomic configuration. At the stable crystal lattice nonequilibrium atomic nanoclusters propagate as solitons in the form of dislocation cores. In a highly nonequilibrium crystal they propagate collectively as nonlinear waves of localized plastic deformation that manifest themselves as meso- and macrobands of localized shear. This approach
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From Editor / Physical Mesomechanics 11 3–4 (2008) 101–104
makes possible a generalized multilevel model for any materials and loading conditions using fundamental notions of the theory of nonequilibrium structural-phase transitions. The multilevel approach for a deformed solid considers the self-consistent interaction of the following subsystems: electron subsystem, surface layers, all internal interfaces, crystal structure of the base and constituent phases of the material, and lattice defects. The 21st century is referred to as a century of nanostructured materials and nanotechnologies. Their related tasks will be solved using the physical mesomechanics methodology that is based on the multilevel approach and operates with nanoclusters of different atomic configuration in local fields of stress concentrators at different structural scale levels. Physical mesomechanics provides the basis for the successful development of new computer technologies of multilevel simulation and design of new generation materials. The journal editorial board decided to dedicate the anniversary issue to invited papers of known scientists that actively develop physical mesomechnaics. The submitted papers exceed considerably the size of one issue and will be published in two anniversary issues. They will include methodological works and those on concrete problems of physical mesomechanics based on the multilevel approach. References [1] V.E. Panin, Yu.V. Grinyaev, T.F. Elsukova, and A.G. Ivanchin, Structural levels of deformation in solids, Russ. Phys. J., 25, No. 6 (1982) 479. [2] V.E. Panin, V.A. Likhachev, and Yu.V. Grinyaev, Structural Levels of Deformation in Solids, Nauka, Novosibirsk, 1985 (in Russian). [3] V.E. Panin (Ed.), Structural Levels of Plastic Deformation and Fracture, Nauka, Novosibirsk, 1990 (in Russian). [4] V.E. Panin (Ed.), Physical Mesomechanics and Computer-Aided Design of Materials, Nauka, Novosibirsk, V. 1, 2 (1995) (in Russian). [5] V.E. Panin (Ed.), Physical Mesomechanics of Heterogeneous Media and Computer-Aided Design of Materials, Cambridge Interscience Publishing, Cambridge, 1998. [6] V.E. Panin, Overview on mesomechanics of plastic deformation and fracture of solids, Theor. Appl. Fract. Mech., 30, No. 1 (1998) 1. [7] V.E. Panin, Synergetic principles of physical mesomechanics, Phys. Mesomech, 3, No. 6 (2000) 5. [8] V.E. Panin and Yu.V. Grinyaev, Physical mesomechanics: a new paradigm at the interface of solid state physics and solid mechanics, Phys. Mesomech., 6, No. 4 (2003) 7 [9] G.C. Sih, Crack tip system for environment assisted failure of nuclear reactor alloys: Multiscaling from atomic to macro via mesos, J. Press. Syst., No. 3 (2005) 1. [10] V.E. Panin, Yu.V. Grinyaev, and A.V. Panin, Field theory of multilevel plastic flow in the neck of a deformed solid, Fiz. Mezomekh., 10, No. 5 (2007) 5 (in Russian). [11] V.E. Panin and V.E. Egorushkin, Nonequilibrium thermodynamics of a deformed solid as a multiscale system. Corpuscular-wave dualism of plastic shear, Phys. Mesomech., 11, No. 34 (2008) 109. [12] A.N. Tyumentsev, A.D. Korotaev, and Yu.P. Pinzhin, Highly defective structural states, fields of local internal stresses and cooperative mesoscopic mechanisms of crystal deformation and reorientation in nanostructured metal materials, Phys. Mesomech., 7, Nos. 34 (2004) 31.
[13] A.N. Tyumentsev, I.Yu. Litovchenko, N.V. Shevchenko, S.L. Girsova, and A.D. Korotaev, Crystal-lattice distortions upon the formation of localized-deformation bands via combined forward-plus-reverse martensitic transformations, Phys. Met. Metallogr., 101, No. 3 (2006) 296. [14] A.V. Panin, Nonlinear waves of localized plastic flow in nanostructured surface layers of solids and thin films, Phys. Mesomech., 8, Nos. 34 (2005) 5. [15] E.E. Deryugin, V.E. Panin, S. Schmauder, and I.V. Storozhenko, Effects of deformation localization in Al-based composites with Al2O3 inclusions, Phys. Mesomech., 4, No. 3 (2001) 35. [16] P.V. Kuznetsov and V.E. Panin, Direct observation of flows of defects and of nm-range localization of deformation on duralumin surface with the aid of scanning tunnel and atom force microscopes, Phys. Mesomech., 3, No. 2 (2000) 85. [17] V.E. Panin, T.F. Elsukova, V.E. Egorushkin, O.Yu. Vaulina, and Yu.I. Pochivalov, Nonlinear wave effects of curvature solitons in surface layers of high-purity aluminum polycrystals under severe plastic deformation. I. Experiment, Phys. Mesomech., 11, Nos. 12 (2008) 63. [18] L.S. Derevyagina, V.E. Panin, and A.I. Gordienko, Self-organization of plastic shears in localized deformation macrobands in the neck of high-strength polycrystals, its role in material fracture under uniaxial tension, Phys, Mesomech., 11, Nos. 12 (2008) 51. [19] S.G. Psakhie, G.P. Ostermeyer, A.I. Dmitriev, E.V. Shilko, A.Yu. Smolin, and S.Yu. Korostelev, Method of movable cellular automata as a new trend of discrete computational mechanics. I. Theoretical description, Phys. Mesomech., 3, No. 2 (2000) 5. [20] S.G. Psakhie, K.P. Zolnikov, and D.S. Kryzhevich, Elementary atomistic mechanism of crystal plasticity, Phys. Lett. A, 367 (2007) 250. [21] I.F. Golovnev, E.I. Golovneva, and V.M. Fomin, Molecular dynamics calculation of thermodynamic properties of nanostructures, Phys, Mesomech., 11, Nos. 12 (2008) 19. [22] V.L. Popov and E. Kröner, On the role of scaling in the theory of elastoplasticity, Phys. Mesomech., 1, No. 1 (1998) 103. [23] A. Godfrey and D.A. Hughes, Scaling of the spacing of deformation induced dislocation boundaries, Acta Mater., 48 (2000) 1897. [24] J.P. Sethna, V.R. Coffman, and E. Dember, Scaling in plasticityinduced cell-boundary microstructure: Fragmentation and rotational diffusion, Phys. Rev. B, 67 (2003) 184. [25] Yu.G. Gordienko, E.E. Zasimchuk, and T.V. Turchak, Scaling of structural parameters and mechanical properties of metals and alloys, Phys. Mesomech., 10, Nos. 34 (2007) 129. [26] O.B. Naimark, Yu.V. Bayandin, V.A. Leontiev, and S.L. Permyakov, On thermodynamics of structural-scaling transitions in solids under plastic deformation, Phys. Mesomech., 8, Nos. 56 (2005) 21. [27] V.E. Panin, A.V. Panin, V.P. Sergeev, and A.R. Shugurov, Scaling effects in structural-phase self-organization at the thin film substrate interface, Phys. Mesomech., 10, Nos. 34, (2007) 117. [28] P.V. Makarov, Evolutionary nature of destruction of solids and media, Phys. Mesomech., 10, Nos. 34, (2007) 134. [29] V.E. Panin, V.M. Fomin, and V.M. Titov, Physical principles of mesomechanics of surface layers and internal interfaces in a solid under deformation, Phys. Mesomech., 6, No. 3 (2003) 5. [30] Surface Layers and Internal Interfaces in Heterogeneous Materials, Ed. by V.E. Panin, Izd-vo SO RAN, Novosibirsk, 2006 (in Russian). [31] V.E. Panin, A.V. Panin, D.D. Moiseenko, Physical mesomechanics of a deformed solid as a multilevel system. II. Chessboard-like mesoeffect of the interface in heterogeneous media in external fields, Phys. Mesomech., 10, Nos. 12 (2007) 5. [32] V.E. Panin, A.V. Panin, D.D. Moiseenko, T.F. Elsukova, O.Yu. Kuzina, and P.V. Maksimov, The chess-board effect in the stressstrain distribution at interfaces of a loaded solid, Phys. Dokl., 51, No. 8 (2006) 408. [33] L.E. Panin and V.E. Panin, Chessboard effect and mass transfer in interfacial media of organic and inorganic nature, Phys. Mesomech., 11, Nos. 12 (2008) 5. Editor of the anniversary issues Academician V.E. Panin