Elasticity characteristics of molybdenum within the temperature range 400–1400 K

We present the results of high-precision investigations of the elasticity characteristics of MChVP commercially pure polycrystalline molybdenum within the temperature range 400–1400 K. The measurements were carried out by using the ultrasonic echo-pulse method. The frequency of the sounding signal was equal to 10 MHz. We establish correlations between the moduli of elasticity in tension and in shear and study the distinctive features of the break in the dependences of the elasticity characteristics of molybdenum near T=900 K. We propose to consider this temperature as one of the physical constants of molybdenum. Institute of Problems of Strength, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 3, pp. 126–129, May–June, 1999.     

Influence of the parameters of temperature cycles on the cyclic fracture toughness of 5Kh3V3MFAS steel

We performed experimental investigations of the crack resistance of tool steel under conditions of nonisothermal loading and established the effect of the time of holding at the maximum temperature of thermal cycles on the critical size of a fatigue crack and cyclic fracture toughness. Institute for Problems of Strength, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 4, pp. 34–38, July–August, 1998.     

A method for the evaluation of the stress intensity factors in a wedge-shaped body with a mode I crack in the form of a circular sector

For the evaluation of the stress intensity factor, we propose a simple method of weight functions based on the Green method. This method generalizes the method suggested in [I. V. Orynyak, M. V. Borodii, and A. Ya. Krasovskii, Probl. Prochn., No. 4, 58–63 (1994)] to the case of corner cracks whose angle differs from 90°. Institute for Problems of Strength, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 1, pp. 107 – 113, January – February, 1998.     

Experimental equipment for evaluation of the strength characteristics of ceramics materials

We describe the design and operating characteristics of a complex of experimental equipment developed at the Special Design and Technological Office of the Institute of Problems of Strength of the National Academy of Sciences of Ukraine for determination of the characteristics of strength, elasticity, and crack resistance of ceramics and other brittle nonmetallic materials and investigation of fracture processes in these materials within the temperature range of 20–1450°C. The equipment developed enables one to decrease the measurement errors significantly and increase both the efficiency of the tests and the amount of accumulated data. Institute of Problems of Strength, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 5, pp. 117–126, September–October, 1999.     

Improvement in the resolving power of impedance thermo- and tomography of biological tissues

We analyzed the possibility for measuring the temperature of the internal structures of a body by using low-frequency currents. We show ways for solving the problem of the limited resolving power of the impedance thermo- and tomography method and present the results of the experiments conducted. National Technical University, Kiev, Ukraine. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 3, pp. 467–471, May–June, 1996.     

On the connection between the adhesive strength and temperature drops in heat-protective coatings

We propose a procedure and results of experimental determination of the dependence of adhesive strength of a ZrO₂ plasma-sprayed heat-protective coating with NiCr sublayer on the value of the stationary temperature drop in it. The dependences of the adhesive strength on the temperature of the surface of adhesive contact are compared for homogeneous and inhomogeneous temperature fields. The results obtained enable us to substantiate the choice of temperature drop in heat-protective coatings with regard for the adhesion safety factor. Institute for Problems of Strength, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 4, pp. 126–130, July–August, 1998.     

Refining the high-temperature strength characteristics of composite materials under bending

On the basis of the complete equation of bending, we establish the refined mechanical characteristics of a carbon-filled plastic under bending as functions of temperature by taking into account the effect of rotation of reactions in the supports. We also show that friction in the supports affects the fracture process in specimen subjected to bending. Institute for Problems of Strength, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 1, pp. 139–141, January–February, 1999.     

Weight function for a circular crack in the temperature problem of the theory of elasticity

A method for the construction of the weight function for a circular crack in an elastic body is proposed for problems of thermoelasticity. The case of an infinite body is studied in more detail. We deduce equations for the stress intensity factors in the cases where either temperature or the heat flow is specified on the crack surface and present some examples of their application. Kiev International University of Civil Aviation, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 6, pp. 91–98, November–December, 1998.     

Determination of the characteristics of distribution of the fatigue limits of materials on the basis of the energy approach

We propose a method for the determination of the mean value of the fatigue limit of a material and its mean-square deviation according to the results of standard fatigue tests. The interpretation of these results from the viewpoint of energy enables us to establish the relationship between the individual durability of specimens and their potential ability to withstand fatigue fracture in the form of individual fatigue limits. Institute for Problems of Strength, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 4, pp. 28–33, July–August, 1998.     

Devices for monitoring the thermal state of the object “enclosure”

The design of heat flow and temperature metering equipment used at the Chernobyl Atomic Power Station for heat and temperature diagnosis of the state of the damaged reactor is described. Deceased. Institute for Problems of Energy Conservation, Academy of Sciences of Ukraine, Kiev. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 2, pp. 255–260, March–April, 1996.     

Influence of the dynamic behavior of materials on the penetration of long rods at elevated velocities. Discussion

We present a brief survey of the influence of the dynamic behavior of materials on the stationary penetration of long rods into thick plates at elevated velocities. Our attention is mainly focused on the analysis of the influence of the resistance of the material to plastic flow, strain rate, temperature effects, compressibility, and the boundaries of interacting bodies on the process of penetration. We also formulate basic directions of subsequent investigations. Institute for Problems of Strength, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 4, pp. 39–51, July–August, 1998.     

Elastic characteristics of iron-glass materials at low temperatures

We present the results of an investigation of the influence of low temperatures on the elastic characteristics of iron-glass materials with 3, 5, 12, or 20 wt.% of glass at 77–300 K and show that Young’s modulus exponentially decreases as the glass content of the material increases. We suggest a relation for the evaluation of the Young’s modulus of a composite at various temperatures according to its value at room temperature. Institute for Problems of Strength, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 1, pp. 42 – 46, January – February, 1998.     

Solution of problems on the stress state of an elastic medium with an inhomogeneous orthotropic cylindrical inclusion

A numerical-and-analytical approach to the investigation of the stress state of an elastic medium with an inhomogeneous cylindrical inclusion is proposed. The stress state is presented as a superposition of two state—the main state written in the analytical form and the disturbed one determined using analytical procedures and a numerical method. The stress state in the vicinity of the hollow cylindrical inclusion is analyzed. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 4, pp. 48–58, July–August, 1999.     

Determination of the energy of electroplastic deformation of metals

On the basis of the well-known mechanism of electroplastic deformation, we suggest a method for determination of the fraction of energy of pulses of the electric current directly spent on the work of plastic deformation. The experimental data presented in the work confirm the validity of the proposed approach. The present work was partially financially supported by the International Science Foundation and the Ukrainian Government (Grant UBW 200). Institute for Problems of Strength, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 4, pp. 38–43, July–August, 1997.     

Some features and potentialities of the generalized analysis of creep-rupture data for metallic materials

The method of basic diagrams was used to analyze over 200 creep-rupture diagrams obtained in long-term experiments (100,000 h or more). The analysis of known experimental data and the prediction of creep rupture based on the departure of some portions of experimental diagrams from the corresponding protions of basic ones offers strong possibilities for increasing the accuracy and reliability of predictions. Deceased Institute of Problems of Strength, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 3, pp. 24–36, May–June, 2000     

On the procedure of evaluating the damping ability of the materials of specimens subjected to torsional and bending vibrations

We describe a method for the design and numerical analysis of compact mechanical vibrating systems with generators of vibrations on their inertial weights and establish the conditions of damping of unwanted vibrations in these systems aimed at guaranteeing the absence of favorable conditions for the introduction of systematic errors to experimental results. The designed and manufactured vibrating systems are dynamically balanced, and predicted values of the frequencies of their natural vibrations satisfactorily agree with the experimental data. Institute for Problems of Strength, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 4, pp. 145–152, July–August, 1997.     

Experimental investigation of heat transfer and simulation of reaction tube furnaces

Results of an investigation of heat transfer in reaction tubes of furnaces for the pyrolysis and conversion of hydrocarbons are presented. Mathematical models of a furnace are developed, and generalized relationships between the diameter of the reaction coil, its length, the pyrogas temperature, and the time of contact are obtained. Optimum dimensions of reaction tubes and coils are determined. Institute of Bioorganic Chemistry and Petroleum Chemistry, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 6, pp. 1009–1013, November–December, 1996.     

Nonstationary heating of particles by a plasma with an exponentially changing temperature

Using a computational method, we investigate the change in the temperature of alumina particles in the process of heating by a hydrogen, steam, air or argon plasma whose temperature decreases exponentially. It is found that on changing from argon to hydrogen the duration of heating to the melting temperature decreases by two orders of magnitude, whereas the difference between the temperatures of the surface and center of a particle increases from 17 to 1700 K. V. I. Vernadskii Institute of General and Inorganic Chemistry, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 5, pp. 787–789, September-October, 1997. Original article submitted October 14, 1994;     

Thermal model of local ultrasound heating of biological tissue

Possibilities of creation of controlled temperature fields in deep-seated biological tissue with the use of an endocavity ultrasound applicator with surface cooling are considered. Mathematical models are proposed and calculated that make it possible to construct acoustic and thermal fields in biotissues depending on the thermophysical and ultrasound characteristics of the medium being irradiated and to reveal situations and effects that are important for solving problems of practical medicine in the field of local ultrasound hyperthermia and thermotherapy of tissue. Kiev Polythechnical Institute, Kiev, Ukraine. Institute of Experimental Pathology, Oncology, and Radiobiology, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 5, pp. 779–784, September–October, 1996.     

Statement of the problem of optimization and control of tissue temeprature distribution in local hyperthermia of malignant tumors

We consider a model of thermal processes in treatment by local hyperthermia. The model is based on the classical nonlinear biothermal equation. We formulated a problem of optimization consisting of maximization of the mortality function of tumor cells and finding a control for which the temperature distribution in the tumor maximizes the therapeutic effect, while the injury function of healthy tissue is small. Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev; Institute of Experimental Pathology, Oncology, and Radiology, National Academy of Sciences of Ukraine Kiev; Academic Scientific Complex “A. V. Luikov Heat and Mass Transfer Institute of the Academy of Sciences of Belarus,” Minsk; National Technical University, Kiev. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 4, pp. 641–646, July–August, 1996.