Load-Carrying Ability and Erosion Resistance of Carbon Composites in a Convective Heat Flow

This paper presents results of studying the regularities in the variation of the load-carrying ability and erosion resistance of carbon/carbon composites with both pure carbon and borosiliconized matrices under conditions of unilateral heating with a flow of air plasma. A comparative assessment of the characteristics under study for several types of carbon composites is given. The degree of influence of borosiliconizing carbon/carbon composites on their performance in operation in convective flows has been determined.     

Radiation-Induced Embrittlement of WWÉR-440 Reactor Pressure Vessel Steel under Loading

The results of evaluating the reference temperature T ₀ are presented and Master Curve is constructed from the experimental data for steel 15Cr2MoVA (base metal of WWÉR-440 reactor pressure vessel) in three states: unirradiated, irradiated, and irradiated under stress. It is shown that mechanical load, which simulates the coolant pressure, accelerates radiation embrittlement, whose contribution is comparable to that of neutron irradiation.     

Analysis of the Results of Mechanical Testing of Metals by Constructing the Diagrams of Structural States

For polycrystalline metals and alloys with bcc (Mo, Fe, and Fe–Si) and fcc (Ni and Cu) crystal lattices, it is shown that the application of the method of reconstruction of parabolic stress–strain diagrams on S –eⁿcoordinates, where S and e are the actual stress and strain, respectively, and n is the strain-hardening index, makes it possible to represent the results of mechanical testing in the form of a diagram of structural states plotted in the form of the dependences of actual stresses and strains on temperature. This diagram practically completely describes the changes in the strength and plastic characteristics of the materials and their structural states in the process of plastic deformation. We study specific features of the construction of these diagrams depending on the composition of the alloy, its structural state, the energy of stacking faults, etc. On the basis of the analysis of the character of correlations between the critical values of strains and stresses and the mechanisms of plastic deformation within broad ranges of temperature and structural states, we discuss the possibilities of scientific and practical application of the diagrams of actual stresses and strains vs temperature.     

Physical Substantiation of the True-Strainndash;Temperature Diagram for Polycrystalline bcc Metals

We consider one of the possible versions of physical substantiation of the form of the true-strainndash;temperature diagram for polycrystalline bcc metals from the initial stages of plastic deformation to fracture within the temperature range from completely brittle fracture to the formation of a new grain structure as a result of dynamic recrystallization. We propose a model explaining the character of the temperature dependences of the critical strains corresponding to the transition from one type of dislocation structure to another under continuous loading. For the MChVP molybdenum alloy used as an example, we perform a comparative analysis of the theoretical and experimental temperature dependences of critical strains and demonstrate their good agreement. We also analyze the influence of factors determining the shape and location of the curves of critical strains in the true-strainndash;temperature diagram.     

Determination of Reference Temperature T0 for Steel JRQ in an Unirradiated State and Construction of a Master Curve

This paper considers the results of testing reactor steel JRQ involving determination of the fracture toughness and the reference temperature T₀, construction of a Master Curve, and evaluation of the boundaries of regions with different failure probability. The tests were conducted on small specimens (1/2T) made from blocks of steel JRQ supplied by the IAEA within the framework of the Round Robin program.     

Test Bench for Full-Scale Cycling of Prosthesis: Artificial Lower Limb

A test bench is described for full-scale testing of prosthesis (human lower limb) under cyclic loading conditions. An engineering and social problems are substantiated that include evaluation of the bench test efficiency and determination of the artificial limb service life with the view of increasing its reliability and the level of social-and-labor rehabilitation. The bench specifications realized in full-scale testing are presented.     

Alternative Fracture Criterion in Terms of the Energy-Based Theory of Strength

Within the framework of the energy-based strength criterion, the transition from the stress space to the stress-intensity-factor space is performed in a such way so that the fracture criterion obtained contains all characteristics of the material crack resistance , as well as dimensions and of the local fracture zone at the crack-tip vicinity under different modes of the crack-face loading. We propose an alternative approximation of the fracture criterion, which is exact in terms of the model under consideration. The theoretical results are compared with some known experiments. An example of the calculation of a structural element with a macrocrack is given.     

Vibrations of a Circular Linear-Viscoelastic Three-Layered Plate

This paper deals with free and forced vibrations of a circular three-layered viscoelastic plate asymmetric in thickness. The hypotheses of a polygonal normal line have been applied to describe the stack kinematics. The filler is light. An analytical solution has been obtained by the method of averaging in dynamic viscoelastic problems using the hypothesis of similarity of relaxation kernels for the materials of each layer.     

True Stress vs Temperature Diagram of Structural States for Polycrystalline bcc Metals

For the first time, a new type of a diagram of structural states is constructed for polycrystalline bcc metals. This true-stress-vs-temperature diagram is a regular collection of temperature dependences of critical stresses corresponding to successive changes in the type of dislocation structure from the onset of plastic deformation to fracture within the temperature range from completely brittle fracture to the formation of a new grain structure. On the basis of analysis of true-stress-vs-temperature diagrams for metals and alloys (Mo, Fe, and Fe–3%Si) with the help of the thermal activation analysis of the temperature dependences of critical stresses, we establish the regularities and distinctive features of the formation and behavior of the temperature–force boundaries and domains of existence of certain structural states and identify the mechanisms of plastic deformation within the limits of each of these domains.