This is the title of the proceedings of the Second International Conference "Fracture Mechanics of Materials and Strength of Structures" which was held on ...
Materials Science, Vol. 36, No. 2, 2000
IN SCIENTIFIC CIRCLES
FRACTURE MECHANICS OF MATERIALS AND STRENGTH OF STRUCTURES S. Kovchyk, H. Nykyforchyn, M. Savruk, and S. Yarema This is the title of the proceedings of the Second International Conference "Fracture Mechanics of Materials and Strength of Structures" which was held on September 14-16, 1999 in L'viv at the Karpenko Physicomechanical Institute of the Ukrainian Academy of Sciences. Three volumes of the proceedings of the Conference edited by V. V. Panasyuk were published by the "Kamenyar" Publishing House (L'viv). The first volume entitled "Mechanics and Mechanisms of Fracture Processes of Materials" (352 pp.) consists of new works of leading native and foreign scientists devoted to the investigation of regularities of initiation and growth of cracks depending on loading, medium, temperature, structure of metal, and technological parameters of welding. The works are grouped in separate sections. In the first section "Surveys," V. V. Panasyuk analyzes the present state of fracture mechanics and highlights the prospects of its further development. L. M. Lobanov, L. I. Mikhodui, and O. L. Mikhodui demonstrate the modem possibilities of optimization of the technology of welding. V.I. Pokhmurs'kyi and M. S. Khoma show the efficiency of electrochemical investigations for the establishment of mechanisms of corrosion fatigue fracture and their prospects for the prediction of service life. O. M. Romaniv analyzes the specificity of approaches of the structural mechanics of fatigue fracture. The reports presented in the section "Experimental Investigations in the Framework of Fracture Mechanics of Materials and Methods for Estimation of Strength" show the possibilities of the force, deformation, and energy approaches within fracture mechanics and consider ways to ensure the correct determination of the characteristics of crack resistance with regard for the scale effect, type of specimens, and loading schemes, to improve the known methods, and to develop new procedures of fracture micromechanics for the estimation of structural strength of materials, which take into account the dynamics of loading and the mechanism of fracture. The section "Micro- and Macromechanisms of Fracture" is devoted to the structural factor of fracture under conditions of creep and presents the approaches taking into account the specific features of fracture of fibrous composite materials, tungsten-cobalt structural alloys, the influence of fluctuations of stresses of chaotically distributed dislocations on macroscopic breaking stresses, and the mechanical approaches to description of the evolution of damages. Moreover, it illustrates the possibilities of the use of the results of measurement of the lifetime of positrons for determination of the mechanisms of interaction of a metal with the environment, clarifies the possibility of the purposeful structurization of structural materials, considers a mechanism of fracture of plasma-arc coatings based on iron, and estimates the influence of a preliminary plastic deformation on the specificity of fatigue fracture of aluminum alloys. The section "Fracture and Strength of Structural Materials" consists of works devoted to investigation of a wide spectrum of the mechanical properties of many structural materials under the action of cyclic and static loadhags by tension, bending, and compression, namely: titanium and aluminum alloys, cast irons, tungsten-cobalt hard KarpenkoPhysicomechanicalInstitute, Ukrainian Academyof Sciences, L'viv. Translatedfrom Fizyko-KhimichnaMekhanikaMaterialiv, Vol. 36, No. 2, pp. 130-132, March-April, 2000. 1068-820X/00/3602-0309 $25.00
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alloys, steels for low-temperature applications, castings of blades of gas turbines, heat-resistant steels, welded joints, and even wood as a natural structural material. The section " T h e Influence of the Environment on the Characteristics of Crack Resistance of Materials" directs our attention to the influence of the working medium on the serviceability of materials. The works in this section are mainly connected with technological processes. They demonstrate the possibility of the use of the approaches of the physicochemical fracture mechanics of materials to facilitate the breaking of rocks and to take into account the negative joint influence of hydrogen and thermal changes accompanying many technological processes and open ways toward increasing the resistance of heat-resistant nickel alloys to high-temperature corrosion. Simulation of working conditions with the use of electrolytic hydrogenation received considerable attention. On the basis of the model of a growth of pores along grain boundaries under conditions of hydrogen corrosion, Nelson curves are calculated. Various methods for determination of the threshold of corrosion-static crack resistance are compared. The possibility of using the analysis of signals of acoustic emission for the investigation of glass fibrous materials and for the study of the susceptibility of spring steels to hydrogen degradation is demonstrated. A method of continuous control over the chemical composition of the medium in circulating water systems is described. Prospects of the estimation of the state of a metal after high-temperature hydrogen degradation on the basis of the threshold cyclic resistance are shown. The diagrams of hydrogen resistance of structural alloys under static and cyclic loadings in hydrogen of high pressure are constructed. Special attention is focused on the geometry of corrosion cracks and on the necessity to take it into account for the determination of crack corrosion resistance of structural materials. The second volume "Analytic Methods in Fracture Mechanics of Materials" (346 pp.) consists of works concerning mainly the development of mathematical methods of analysis of stress-strain states of cracked bodies. The section "Surveys" consists of surveys concerning the analysis and synthesis of deformational criteria in the fracture mechanics of materials (0. E. Andreikiv), numerical methods for the solution of three-dimensional problems of the theory of cracks (H. S. Kit), the use of modern approaches of fracture mechanics for the prediction of the risk of formation of hot and cold cracks in the process of welding (V. I. Makhnenko), and the results of study of fracture at fast and superfast loadings (N. F. Morozov and Yu. V. Petrov). The section "Criteria of Fracture and Calculated Models" consists of the results of investigation of the fracture of linear and physically nonlinear materials under static and cyclic loadings, the influence of corrosion and hydrogen-containing media on fracture, accumulation of damages in multicomponent viscoelastic materials, and several mathematical models of growth of a fatigue crack of transverse shear and a tensile crack under loading with varying amplitudes, a structural model of short-term damage of materials, a probabilistic model of fracture of materials under conditions of creep, and mechanical models of the initial stage of the development of brittle and plastic fracture. This section includes also the problems of the mechanics of surface fracture of solids in the process of rolling and slip, determination of residual durability of plates with a reinforced hole, and fracture of shell elements under conditions of an inhomogeneous stressed state. The section "Methods for Determination of Physicomechanical Fields of Media and Structural Elements" presents reports on the distribution of residual welding stresses in steel plates with circular welds, reinforcement of structural elements due to the formation of residual stresses by local intensive heating, nondestructive optical control over residual stresses in inhomogeneous bodies, reinforcement of a strip with original stresses with elastic straps, and the influence of the preliminary plastic deformation on the stressed state of structurally inhomogeneous materials with tunnel inclusions. The main relations for determination of the interaction of a deformed metal with the corrosion medium are given, and the electrode potential and corrosion currents over the surfaces of stress concentrators are determined. A singularity of stresses at the tip of a circular notch in a nonlinear material, the elastic equilibrium of the space weakened by two coplanar wedge-shaped notches, and the concentration of stresses in the vicinity of strip inclusions in a piecewise homogeneous anisotropic medium are investigated.
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The section "Problems of the Mathematical Theory of Cracks" is devoted to the elastic and limiting equilibria of cracked solids and includes an analysis of static problems on isotropic and anisotropic plates with holes and cracks, a space with close parallel cracks under antiplane deformation, a cracked plate reinforced with stringers in the case where discontinuities appear in the stringers, plates with slots and cracks with regard for the contact of their lips under transverse bending, a half plane with cracks subjected to the action of a plane die, and a longitudinal crack in an isotropic box-like and anisotropic cylindrical shells. Problems of fracture mechanics in the case of pulse and impact cyclic loadings are investigated. Diffraction of a torsional wave on a spherical crack is analyzed. The third volume "Diagnostics, Prediction, and Increase in Durability of Structural Elements" (286 pp.) consists of the following sections: The section "Surveys" consists of works devoted to the driving force behind technological progress on the eve of the XXIst century, new structural materials, and new problems of the mechanics of media (W. Kasprzak). New approaches to the estimation of the service life of the components of atomic power stations at the stages of design, testing, and operation are proposed by M. A. Makhutov and M. M. Hadenin. Z.T. Nazarchuk and V. M. Zybov analyze methods and means of electromagnetic nondestructive control (the physica ! aspect, numerical realization, and measuring aspect) for the prediction of the'state of objects. Organizational measures and measuring systems for the diagnostics of welded structures, the safety of the environment (B. E. Paton and A. Ya. Nedoseka), and the prediction of fatigue durability of materials (V. T. Troshchenko) are proposed. The section "Nondestructive Testing Methods and Diagnostics of the State of Structures" consists of works devoted to the development of nondestructive testing methods, means, and diagnostics of the state of structures; namely, the method of holographic interferometry for the diagnostics of defects and investigation of the deformation of the elements of structures with notches, radio wave control in aviation, control over the state Of materials on the basis of the measurement of coercive force, and the method of acoustic emission. The section "Analysis of Strength and Durability of Machine-Building Structural Elements" presents the results of development and use of the methods of fracture mechanics for the investigation of growth of fatigue cracks and the prediction of residual durability of welded joints, the analysis of durability of structural elements of power equipment with regard for the action of the corrosion medium, and the estimation of factors which promote an increase in the corrosion resistance of welded joints in the process of electrohydropulse treatment. New methods for the prediction of durability of structural elements of power equipment and thick-walled tubes at the stage of development of surface cracks with regard for the action of high temperatures are proposed. The section "Strength and Durability Analysis of Elements of Building Structures" is devoted to an analysis of the durability of the components of concrete structures and the development of approaches to the estimation of resistance of concrete to multicycle thermal-humid action on the basis of the parameters of fracture mechanics. A computational scheme for the analysis of strength and crack resistance of reinforced concrete elements is proposed. The results of calculation are compared with the experimental data on deformation processes in the bent elements of lightweight and ordinary concretes. The influence of nonequicomponent all-a.round compression on the fracture of rocks and durability of concretes under repeated variable loading is investigated. The conditions for the appearance of stresses and strains in concrete and reinforced concrete structures are analyzed. Modem monitoring methods for the prevention of fracture of structures erected on sagged grounds are proposed. This book can be ordered at the address: Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, Editorial Office of the Journal "Physicochemical Mechanics of Materials," 5, Naukova Str., L'viv, 79601, Ukraine. For more information, please, caU 63-73-74.
