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We perform the experimental investigation of the fretting fatigue of a 15kp steel-45 steel couple in the case where both the size of the counterbody and the level of contact stresses are variable. The proposed second-order polynomial model of regression analysis fairly exactly approximates the experimental data. On the basis of this model, we predict the effect of contact stresses and scale factor on the service life of the couple under conditions of fretting fatigue. It is shown that the service life decreases as the contact pressure increases up to a certain fixed level and that this effect becomes more pronounced for high amplitudes of stresses. The scale factor effect can be described as the decrease in the service life of a fretting couple with smaller sizes of the counterbody for high amplitudes of stresses. In order to explain the indicated prediction, we study the corresponding mechanism of interaction between the specimen, counterbody, and fretting products.

A probabilistic model was developed for coalescence of cracks randomly dispersed on the surface and having uniform orientation and statistically nonuniform length. The model makes it possible to calculate the probability of coalescence of any pair of closely located cracks with allowance for the interaction of the strain fields. The model has been modified for the case of coalescence of cracks having the biggest length in the sample. The initial parameters for determining the probability of coalescence are: mathematical expectation of the length of cracks, their surface density, the magnitude of the damaged area of the material (size-scale factor), and the level of the acting stress. The model obtained can be used to predict the life of a component from the criterion of formation of critical cracks by coalescence of dispersed defects.

A nonlinear criterion of the static strength of products made of structurally heterogeneous materials, whose mechanical properties depend strongly on the reduced volume and stressed state mode, is proposed and substantiated on the basis of the generalized Pisarenko–Lebedev criterion. Based on the proposed criterion, we estimated the strength of cemented carbide components of cylindrical and recessed anvil high-pressure apparatus for the synthesis of diamonds and other superhard materials after their assembly and under operating conditions with working pressure and thermal loading. For the above loading conditions, we determined the values of reduced volume and mechanical characteristics of the cemented carbide VK6, which enter into the Pisarenko–Lebedev criterion. We study the dependence of the strength of geometrically similar components of high-pressure apparatus on their working volume.

The author proposes a method of evaluating the effect of the transverse dimensions of specimens on long-term strength. The method is based on taking into account different roles of surface and internal layers of the metal in real tests. The concept of the damaged layer, formed on all side surfaces of the tested specimens as a result of corrosion, is introduced. The thickness of this layer is calculated from the condition according to which the long-term strength curve, determined for the unfractured central part of the cross section, does not depend on the geometry and dimensions of the specimens. It is shown that to calculate this parameter it is sufficient to have two long-term strength curves corresponding to test series of specimens of two thicknesses. A statistical method of determining all characteristics of the material has been proposed. The method is suitable for describing the available experimental data. It has been shown that the integral quantitative characteristics of the scatter of the experimental and theoretical values of the fracture time as a result of using the proposed method for a number of materials decrease by a factor of 10 or more.

Problems of obtaining estimates of the mechanical strength distribution parameters of semiconductor wafer material and selecting the optimal testing method providing their stability with respect to the scale factor are examined. The results of an experimental estimation of the mechanical strength distribution parameters of various grades of silicon after rough and finish machining of wafer surfaces are presented.

We worked out a physical and a finite-element model of a crankpin to investigate the state of stress and the fatigue limit of crankshafts. With a view to the condition of similarity between reality and model in the elastic range, and also to possible damage cumulation at critical places caused by cyclic limit loads in bending, we investigated the influence of the scale factor on the stage of stress and on the fatigue limit of crankshafts. It was established that the conditions of similarity of the bending stresses in limit moments satisfy a broad range of dimensionalities of crankshafts of present-day internal combustion engines with a degree of accuracy sufficient for engineering practice.

On the basis of the energy criterion of fracture a method of calculation of the relationship of the strength of quasibrittle rods in uniaxial tension and bending of rectangular and round cross section to their geometric dimensions was developed. With use of the analytical relationships obtained and known experimental data it is shown that with an increase in loading rate of the bodies being deformed the influence of the surface layer simulated by a physical surface on the strength of glass specimens first drops to a minimum value and then steadily increases.

Investigations were carried out into the effect of the scale factor on special features of intermittent yielding of structural alloys under rigid static loading at the boiling point of liquid helium (4.2 K). The results show that an increase of the deformed volume of the metal is accompanied by reduction of the specific surface,which impairs the conditions of heat removal from the gauge part of the specimen. This in turn changes the nature of intermittent yielding of the material. It is important to take into account the effect of the form and dimensions of specimens as well as the structural elements on special features of their deformation at low temperatures (4.2 K).

1. The long-term thermal-fatigue strength of hard materials (brittle and semibrittle) of different structural classes together with their level of brittleness and macroductility, obtained with a view to time effects, the scale factor, the physicochemical effects of the contacting medium, are also determined by the characteristics of structural inhomogeneity. 2. The time effects of long-term thermal-fatigue strength of hard materials are associated with the development of processes of thermal loss of strength in them at the maximum temperature of the thermal cycling and of retarded fracture at the mean temperature of the thermal cycles. 3. An analysis of the results of bench tests with actual structural elements made of brittle materials and subjected to thermal cycling in a medium of sodium for up to 9000 h with the aid of the newly worked-out relationship of thermal fatigue showed that they correspond to the calculated thermal fatigue strength with a safety factor equal to 2–3.

1. The average strength in bending for specimens of glass ceramic STM-1 of the homogeneously defective modification with dimensions 120×25×10 and 60×7×7 mm is almost the same, which is indicated by limited application of the weakest link concept to homogeneously defective glass ceramic. 2. Strength in bending of compound defective glass ceramic markedly depends on the specimen dimensions. In particular, the average strength of glass ceramic AS-418 with dimensions 60×7×7 mm exceeds the average strength of specimens with dimensions 120×25×10 mm by 13.6% with fine surface grinding, by 19.8% with carborundum grinding, and by 32.2% of the strength of specimens with dimensions 120×50×10 in the case of fine surface grinding. The average strength of specimens of the compound defective modification for glass ceramic STM-1 with dimensions 60×7×7 mm exceeds by 24.4% the average strength of specimens with dimensions 120×25×10 mm with carborundum grinding. 3. Localization of the most critical defects in an area not coinciding with the overall area of loaded specimens, in particular at chamfers, decreases the dependence of strength on specimen dimensions.

1. Relationship of the bend strength of technical devitrified glasses to the scale factor has a maximum, the presence of which is explained by the total action of surface and volume defects of the material. 2. With an increase in the volumes of samples from 2025 to 43,200 mm3 (the first branch of the scale effect curve) there is a reduction in the average values of strength, reaching 22 and 26% for STL-10 and A-1 devitrified glasses, respectively. In this area the relationship of strength to sample dimensions is described sufficiently well by the equations of the statistical theories of brittle strength of V. Weibull and V. V. Bolotin and the error in the use of these equations does not exceed 5%. 3. The possibility of joining the experimental data of strength tests in a single general combination was determined and on the basis of regression analysis a linear relationship (in logarithmic coordinates) was established between the bend strength of technical devitrified glasses and the minimum size of the mirror zone of the fracture of different size samples.

1. The energy absorption by a ship damaged as a result of a collision can be found by static experiment, and the effect of the collision velocity on energy absorption can be corrected in accordance with the increase of the material constant due to the enhanced strain rate. 2. There exist two fracture mechanisms during collision: one called piercing fracture mode, the other called crushing fracture mode. 3. During crushing fracture mode the energy absorption is large until fracture of the side skin but then decreases catastrophically. 4. During piercing fracture mode energy absorption continues to increase, roughly in proportion to the, square of the penetration depth, even after fracture of the side skin. 5. From the viewpoint of energy absorption during collision, a structure preventing fracture of the piercing mode is more suitable in the case of large critical values of the penetration depth than a structure preventing fracture of the crushing mode. One can change the mode of fracture by varying the dimensions of the deck plates and the side skin and of the stiffeners used in the structure. 6. In the presence of a scale factor γ the load and energy absorption in the penetration depth function are proportional to γ2 and γ3, respectively.

1. In the uniaxial static elongation of geometrically similar samples, the strength characteristics (σB and σ0.2) and the relative elongation (e) are practically independent of sample diameter. The relative contraction (ψ) increasing with falling diameter, this effect being particularly sharp below 4 mm. 2. In estimating the mechanical properties of materials tested in two states (annealed and coldworked), the diameter has the greater effect on the relative contraction for the cold-worked metal, i. e., the scale effect appears more strongly for a less well-developed process of plastic deformation, such as occurs in high-strength samples. 3. In the shock (impact) extension of geometrically similar samples by loads of equal mass, over the range of small elastic-plastic deformations the relative elongations are no longer constant when the specific absorbed impact energy remains so (A/V=const); however, in the case of a well-developed process of plastic deformation the general law of similarity remains intact. 4. An estimate of the ductility of high-strength materials based on the relative contraction of samples of small diameter (under 4 mm) tends to be too high (by 20 to 40%) and cannot serve as a criterion for justifying any particular technical operation carried out with a view to improving the mechanical properties of metals.

1. The technology of preparing specimens for investigating creep of titanium alloys at ordinary temperatures may substantially effect the creep parameters. 2. To remove possible errors in testing, the specimens must be finally brought to the desired dimensions by hand. It is possible to do this by machine, but in so doing the feeding rate of the cutting tool must be minimal. 3. The shape and size of a specimen has practically no effect on the creep characteristics of titanium alloys at ordinary temperatures. Experiments on specimens of standard shape and size furnish reliable data on the creep of these alloys.

1. Specimen size has a material effect on the durability of components of Kh18N9T steel during hightemperature creep with both axial loading and complex stress patterns. 2. The scale factor becomes especially pronounced as the test time increases, i.e., as the effective stress decreases. 3. The state of the superficial layer, in which failure processes begin, has the strongest influence on long-term strength, as is observed in specimens with large surface to volume ratios.