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1.
G. S. Neshpor V. P. Gusev G. D. Kudryavtseva M. I. Zhukova A. D. Petrov 《Strength of Materials》1989,21(8):998-1004
| 1. | In a plate of alloy 1163T the mean rates of fatigue crack growth increase from 3.2 to 8.6 mm/kc with when the thickness of the specimens increases from 3 to 15 mm, and the characteristics of static crack resistance attain their maximum when the thickness of the specimens is t* (KIc/0.2)2 10 mm. |
| 2. | With increasing thickness of the specimens, the pitch of the fatigue grooves and the proportion of elements of static failure increase in the fatigue fracture. In a static fracture there is failure by shear, intragranular pitting and ductile grain boundary failure, and with increasing thickness of the specimens the proportion of grain boundary (low-energy) failure increases. |
| 3. | The transition from plane strain to plane state of stress is effected in the region of increase of crack length equal to the thickness of the specimen. |
2.
| 1. | The mechanical properties of niobium and its alloys depenet to a considerable extent on their content of interstitial impurities at both low and high temperatures; this opens up the possibility of alloying with such impurities finished components of niobium and its alloys in order to obtain the best combination of strength and ductility in each particular case. |
| 2. | The results of long-term strength tests on alloy 5VMTsU at 1100°C in vacum of 10–5 and 10–8 mm Hg have shown that the strength of this alloy on a basis of 800 h falls by 49% in a vacuum of 10–8 mm Hg. |
3.
B. A. Kolachev 《Materials Science》1992,28(5):395-398
| 1. | A general method of improving the composition of the HSA by complex alloying has been proposed. |
| 2. | Systems of alloying the HSA on the basis of intermetallic compounds TiFe, TiCo, TiCr2, TiMn2 have been described and characterized. |
| 3. | It is shown that not all possibilities of complex alloying have been exhausted to improve the properties of the HSA based on titanium. |
4.
J. Davidov 《Materials Science》1993,28(1):62-67
| 1. | With respect to low-cycle fatigue behaviour the increasing of iron quantity from 0.12% to 0.38% results in a decrease of cyclic ductility of AlSi7Mg alloy but this decrease is not very significant. |
| 2. | The alloy with 0.12% Fe shows better low-cycle fatigue resistance then other materials investigated due to its relatively higher cyclic ductility. |
| 3. | The structure with 0.29% Fe shows the best fatigue crack growth resistance which is due to the best combination of its mechanical properties and relatively ductile type of fracture. |
| 4. | With regard to the low-cycle fatigue behaviour and fatigue crack growth resistance investigations carried out in this work have shown AlSi7Mg alloy with 0.29% Fe seems to be the most appropriate material for manufacturing counterpressure cast car wheels of the particular design investigated because the decrease of cyclic ductility for this structure is not very significant. |
5.
S. I. Yakovenko A. P. Guk V. I. Lakh V. N. Kryzhanovskii 《Strength of Materials》1988,20(12):1682-1684
| 1. | The temperature-time relationship of the allowable mechanical loads of a thermal transducer protection tube was established. |
| 2. | For a preliminary evaluation of the strength of a thermal transducer in relation to service time it is necessary to use the temperature relationship of the modulus of elasticity or of the stress-rupture strength of the materials used. |
| 3. | Failure of the protection tube of a thermal transducer in long high-temperature loading occurs as the result of development of pores primarily at grain boundaries. |
6.
| 1. | Multiple regression analysis was used to determine a strong correlation between the composition and physicomechanical characteristics of the high-manganese steel alloyed with boron and vanadium. |
| 2. | The correlation of abrasive and impact-abrasive wear resistance with each mechanical characteristic is very weak and in certain cases does not exist at all. |
| 3. | A correlation was found between each type of wear and the remaining characteristics. Abrasive resistance can be increased only by increasing hardness and impact-abrasive wear resistance can be increased by increasing hardness and bending strength. Impact toughness has no effect on wear resistance in both types of wear. |
7.
| 1. | The specific energy of plastic deformation characterizes quasibrittle failure of metal structures operating under extreme conditions in the cold climate, and makes it possible to compute the limiting stresses and strains at different stress raisers. |
| 2. | The strength of components and elements of metal structures with stress raisers in elastoplastic deformation can be evaluated on the basis of the energy loss in the zone of strain localization. |
| 3. | The values of the threshold strain for 20 steel, calculated during mechanical tests with determination of the specific energy of deformation and failure, are in the range of exhaustion of ductility determined by x-ray diffraction analysis. |
8.
N. M. Grinberg V. A. Serdyuk A. M. Gavrilyako V. A. Zolot'ko E. L. Miloslavskaya L. E. Gorelkova 《Strength of Materials》1989,21(7):859-865
| 1. | In the AMg6 aluminum alloy the fatigue crack growth rate at 293 K decreases as compared with the same value in air and parameters Kth and K* increase in vacuum. |
| 2. | With a temperature drop from 293 to 140 K the fatigue crack growth rate decreases especially at low Kmax values, while the Kth and K* values increase. |
| 3. | Each region of the kinetic diagram of fatigue fracture is characterized by a definite micromechanism of fatigue fracture which for the investigated alloy does not change in vacuum even at temperatures falling to 140 K. |
| 4. | On the basis of the dependence of groove pitches on Kmax for the AMg6 alloy in region II of the kinetic diagram of fatigue failure, coordinates K* and A of the transition point which divides this region into sections IIa and IIb were determined. Ordinate A=SIIa does not depend on the medium and temperature and is for this alloy (1.8–2.0)·10–7 m. |
| 5. | Since K* is an important practical characteristic of cyclic crack resistance, the experimental method of its determination must be based on recording the transitional character of one of the physical processes taking place in this point. |
9.
| 1. | The structures of the nodal sections of the dished ends designed in accordance with the compensation principle and design restrictions of the standards are charcterized by the permissable level of the maximum working stresses. |
| 2. | In varying the fraction of the reinforcing metal of the nozzle section situated in the wall of the dished end from 50 to 80% the level of the maximum stresses in the section changes only slightly. |
| 3. | The structures containing 70–80% of reinforcing metal in the wall of the nozzle are more rational from the viewpoint of reducing the metal requirement and have sufficient strength at the same time. |
| 4. | The permissible value of the ratio d/D specified by the standards can be increased from 0.3 to 0.5 without reducing the strength of the nozzle section. |
10.
V. T. Troshchenko V. V. Pokrovskii P. V. Yasnii V. G. Kaplunenko V. V. Burdakov V. P. Leonov Yu. A. Nikonov 《Strength of Materials》1988,20(9):1138-1145
| 1. | On the basis of the experimental investigation of the effect of the test temperature (153–293°K) on the rate of FCG in steels IP-1, IP-2, and IP-3 with a coefficient of load cycle asymmetry R=–2, –1, 0, and 0.5 it was established that lowering of the test temperature has an ambiguous effect on the rate of fatigue crack growth in the mentioned steels. In most cases the rate of FCG is practically insensitive to the test temperature although we can see a general tendency of the coefficient m of the Paris equation increasing with the test temperature being lowered from 293 to 153°K. |
| 2. | A change of the coefficient of load cycle asymmetry in the range –2–0 does not have a substantial effect on the rate of FCG, and in the range 0–0.5 it reduces this rate (in coordinates d/dN-Kmax) at 213 and 293°K, particularly substantially at 213°K. |
| 3. | For the investigated chrome-nickel-molybdenum steels in the temperature range 293-153°K a single dependence was established; it describes the decrease of the coefficient m with rising level of fracture toughness under static loading. |
| 4. | With the test temperature rising from 113 to 153°K, the characteristics of fracture toughness of all the investigated steels increase monotonically under static and cyclic loading, and also in the case of stopping of the crack. |
| 5. | Cyclic loading reduces substantially (to one half) the fracture toughness of steels IP-1 and IP-2 in the temperature range 113–153°K and does not change the values of K1 fc compared with KIc for steel IP-3. |
| 6. | In steels IP-1, IP-2 at temperatures of 113–153°K the fracture toughness under cyclic loading corresponding to final fracture of the specimen practically coincides with the fracture toughness at the instant of stopping of the crack. |
| 7. | In the temperature range 100–183°K of the three investigated steels steel IP-1 has the highest resistance to brittle failure under static loading and at the instant of stopping of the crack, steel IP-2 has the lowest resistance. |
11.
| 1. | The kinetics of growth of the diffusion zone, formed in the dynamic powder mixture, differs from the kinetics of growth in the stationary mixture by the value of the parabolic growth constant. The difference in the diffusion constants is reflected in the structure and the phase composition of the borosiliconized layer. |
| 2. | The special feature of formation of the phases of the diffusion layers in the dynamic borosiliconizing mixture is the formation of higher silicide phases and also phases of a more complicated composition. |
| 3. | With all conditions being equal, the rate of saturation in the dynamic mixture in borosiliconizing is 1.5–2.0 times higher in comparison with saturation in the stationary mixture. |
12.
T. B. Buzovkina A. N. Sofronkov L. I. Korolenko S. A. Lyaskovskii I. A. Kuznetsova 《Materials Science》1993,28(4):354-358
| 1. | Unstable peroxides are formed when sea water reacts with a nonpassivating steel surface, which results in passivation. |
| 2. | The pH shifts as far as 13 in sea water in a real static crack in 15KhN5 steel, which is accentuated as the stress level increases, the crack lengthens, and the tip is approached. |
| 3. | The alkalinization in sea water above steel turnings is much less than in a crack but the pH dynamics are the same. |
| 4. | Metabolites from aerobic fouling organisms (bicarbonates and oxygen) retard the decomposition of hydrogen peroxide at the surface, which raises the pH and Eh; the metabolites from aerobic bacteria (hydrosulfides) reduce the hydrogen peroxide concentration, which reduces the pH and Eh. |
| 5. | The hydrogen release overvoltage is reduced on peroxide films on steel surfaces of 15KhN5 type, and the cathodic reaction of depolarizer reduction is retarded. |
13.
I. M. Rozenshtein 《Materials Science》1992,28(5):421-424
| 1. | The critical temperature of arrest of brittle cracks can be interpreted as a partial case on the critical temperature of brittleness in crack initiation. |
| 2. | A method of determining the correlation between the CTABC and the critical brittleness temperature at crack initiation was determined. |
14.
A. Ya. Krasovskii I. V. Orynyak A. V. Naumov V. N. Krasiko 《Strength of Materials》1989,21(6):697-702
| 1. | A computational model is proposed, and a general solution is obtained for equations describing the process of the impact testing of specimens in concentrated bending in the presence of supports, where the effect of the striker and support on the specimen is represented as the reaction of springs with flexibilities and , respectively. |
| 2. | The general solution for each of the force parameters assumes the form of the sum of two harmonic functions and a function that is linearly time-dependent. For large time values, therefore, the vibratory processes become negligibly small; this makes it possible to use the quasistatic approach, whose accuracy is proportional to the time to failure, to determine KId. |
| 3. | Experimental confirmation of the solutions obtained suggests that disregard of the flexibilities of the specimen halves in the computational model (shoulders of specimen) leads to a reduction in the computed vibration amplitude and period as compared with the experimental. The difference between the theoretical and experimental results increases as the ratio L/Lo increases and the ratio a/W decreases. |
15.
A. E. Andreikiv N. V. Lysak V. R. Skal'skii I. L. Parasyuk O. N. Sergienko 《Materials Science》1993,28(4):378-382
| 1. | Cracking occurs in tubular specimens of U8 steel hydrogenated to high hydrogen concentrations mainly because the gaseous hydrogen affects the steel. |
| 2. | Slow failure occurs by the formation and growth of defects of crack type, which cause the large-amplitude discrete AE signals alternating with continuous AE ones of relatively low amplitude. |
| 3. | Cracking is accentuated by increased pressure during the hydrogenation at a given temperature and by reduction in the cooling time. |
| 4. | High tensile steels saturated with hydrogen are liable to slow failure by the formation and growth of defects of crack type. The main periods in the failure are as follows: a) preparatory period, with plastic strain and corrosion due to the high temperatures and to the residual-stress and strain concentrations on cooling; b) the incubation period, when microcracks are formed at grain boundaries and nonmetallic inclusions; and c) subcritical growth period, where microcracks merge into macrocracks, which grow. |
| 5. | The cracks grow in steps equal to the sizes of the grains or a few grains, and the AE is due to intercrystallite cracking in the zone of stable crack growth in U8 steel. |
16.
S. M. Lyalikov 《Strength of Materials》1989,21(5):687-690
| 1. | It has been established that SPD reduces inelastic strain per cycle for the stress levels studied with any number of loading cycles. |
| 2. | As a result of mechanical strengthening the fatigue limit and endurance of steel 14Kh17N2 specimens increased to a greater extent than for steel 20. |
17.
| 1. | In the presence of longitudinal cracks of varied length (40–160 mm) and varied amount of elastic energy of the compressed air model (1400–9400 kgf·m) the failure of models on thin-walled shells 0.5 mm thick, when loaded by an internal pressure, has a ductile character, independently of the fitting of transverse tires located at different distances from the crack tip (from 20 to 105 mm). |
| 2. | As the initial length of crack increases, its subcritical growth in thin-walled shells increases linearly. |
| 3. | As the crack length increases, the failure stress (gross) is substantially reduced (from 22 to 9 kgf/mm2). At the same time the character of failure is altered: a straight-line propagation of the crack along the generator of the cylinder is replaced by a curvilinear propagation that approximates the failure direction to the circumferential direction. |
| 4. | With a reduction by a factor of two the amount of elastic energy contained by the compressed air model has almost no effect on the strength and geometrical features of the fracture. A dominant effect on the character of fracture is exerted, apparently, by the magnitude of the failure pressure which alters the relationship of the velocities of propagation of the crack and the waves of elastic unloading. |
| 5. | The limitations on the applicability of the existing calculation methods of the fracture mechanics, for the estimation of the resistance to a ductile failure of thin-walled cylindrical shells, is revealed, and appropriate corrections are proposed. |
| 6. | The effectiveness of the use of transverse tires to stop a started ductile failure of shells loaded by an internal pressure, depends on the distance between the tire and the vertex of the initial crack. This distance leads to a transition from the stoppage of the moving crack to its direction being altered. |
18.
| 1. | An algorithm was developed which employs a finite-elements method to solve problems characterized by large dimensions. The algorithm makes it possible to determine the stress-strain state of GTE rotors and to evaluate their load-carrying capacity. |
| 2. | The proposed method of formulating boundary conditions from the results of calculations performed for the assembled rotor makes it possible to determine the stress-strain state of the individual elements with allowance for their interaction. |
| 3. | The results of calculations for the assembled rotor can be used to reliably determine the clearances in the seals. |
| 4. | To reduce the bending strains in cantilevered disks, it is recommended not only that sloping disks be used, but also that the body of the disks be offset relative to the rim. |
19.
| 1. | We obtained a modified singular solution of the problem of fracture mechanics for a body with a normal dilatational crack in steady creep when the behavior of the material is described by a determining equation that takes the effect of the kind of state of stress into account. |
| 2. | We dealt with the simplest function of the effect of the angle of the kind of state of stress as a result, it was established that the numerical values of the reduced functions and and also In, m depend solely on the one parameter m. An analysis of the generalized dependence in the form (4) showed that the general structure of the solution (1) does not undergo any changes either, and the corresponding reduced functions and In depend on the numerical values of the constants of Eq. (4) which are found for the actual material. |
20.
| 1. | Steel strengthened by phase work-hardening is distinguished by a ratio of fatigue limit to tensile strength (–1/u=0.55–0.60) significantly greater than that of dispersion hardening steel. |
| 2. | The surface treatment method (grinding, turning, surface plastic deformation to a definite intensity) does not have a significant effect on the fatigue strength of N26T steel strengthened by phase work-hardening. |
| 3. | Combined strengthening of phase work-hardenable steel by surface plastic deformation, which causes the formation of 15–25% phase on the surface, and subsequent aging at 350–400°C is an effective means of increasing life. The use of this method makes it possible to increase the fatigue limit by 20% for uniform cross section samples and by 200% for those with a notch. |
| 4. | The increase in the fatigue limit with the use of combined strengthening (surface plastic deformation and aging) is related to the increase in the strength of the surface layers as a result of the increase in the dislocation density and fixing of them by the particles of Ni3Ti precipitated in aging and also to the decrease in peak microstresses. |