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1.
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. |
2.
| 1. | The microstructure of the steel has a strong effect on the resistance to low-cycle fracture. The highest fracture resistance in cyclic loading is shown by the steel with the austenitic structure, that of the steel with the ferritic-pearlitic structure is slightly lower, whereas the lowest resistance was recorded for the steel of the transition grade (ferritic-martensitic). This is explained by special features of deformation of their microstructural components and different properties of the crystal lattice. |
| 2. | In low-cycle loading, the austenitic steel shows susceptibility to hardening, the steel of the ferritic-pearlitic grade is stable, and the steel with the sorbitic and ferritic-martensitic microstructure softens. |
| 3. | The low-cycle deformation resistance of the steels of different structural grades depends on the strength properties in static loading: the resistance is always higher In the material with a higher ultimate strength, i.e., in the steel with a martensitic microstructure. |
| 4. | The microstructure of the steel has the maximum effect in the near-threshold region of the fatigue failure diagram. |
3.
O. N. Romaniv A. N. Tkach T. Ya. Yus'kiv V. I. Ovchinnikov V. A. Sharkov 《Materials Science》1990,26(3):274-281
The presence of the graphite inclusions in the structure of the cast iron greatly affects the cyclic cracking resistance as a result of an increase of the dissipation of energy during crack growth and its closure. The dissipative processes lead to branching, blunting, and deviation of the crack from the plane of action of the highest normal stresses. This inhibits crack propagation. The effect of these processes is maximum at low crack growth rates and decreases with increase in AK. At FCG in cast irons failure takes place both in the graphite particles and at the matrix-graphite interface boundaries with the graphite inclusions displaced to the fracture surface. Being the highest elements of the relief of the fracture surface, the graphite particles increase its roughness and determine the mechanism and level of the CC. The described special features of the behavior of graphite in the cast irons during FCG indicate the following:
Translated from Fiziko-Khimicheskaya Mekhanika Materialov, No. 3, pp. 33–40, May–June, 1990. 相似文献
| – | at low crack propagation rates (below 10 -9 m/cycle) the CCT of the cast irons is, irrespective of the form of the graphite inclusions, higher than in the steels with similar structures; |
| – | at rates higher than i0 -s m/cycle, the CCT of the cast irons with matrix of the same structure depends not only on the form of graphite but also on the crack growth rate; |
| – | the specific features of FCG in the cast irons with plate-shaped inclusions of graphite (high AKth and curvature KDFF) causes that GCI cannot be used for machine components operating under cyclic loading conditions; |
| – | the structure of the metallic matrix in the cast irons with vermicular graphite particles does not effect the CCT; |
| – | in cast irons with nodular graphite, the CCT at low rates of FCG increases with an increase of the size of globules and strength of the matrix; |
| – | in the cast irons with the nodular and vermicular graphite with the same structure of the matrix, the CCT depends on the strength of the matrix and its capacity to relax local stresses; |
| – | the cast irons with nodular and vermicular graphite inclusions are capable of competing with the structural steels in respect of their CCT. |
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.
| 1. | Single relationships linking the minimum level of static crack resistance KIc with the conditional yield point and reduced test temperature Ttest-Td 50 are constructed on the basis of experimental results of the testing of steels of different strength and structural state. |
| 2. | The curves obtained make it possible to propose a simple method for calculating the minimum guaranteed level of static crack resistance KIc of structural steel on the basis of standard mechanical characteristics of strength (0.2) and cold resistance (Td 50), which can be used in selecting and working steels and also in optimizing regimes for their smelting and heat treatment. |
| 3. | The proposed method, which is used to calculate temperature dependencies of the static crack resistance of steels cast from experimental melts, has made it possible to select the optimal composition of a cold-resistant cast steel for the undercarriage of heavyduty quarry excavators. |
6.
| 1. | High-temperature thermomechanical treatment and microalloying with 0.1% La raise the fatigue and corrosion-fatigue strength of steel 1Kh17N2. |
| 2. | The rise in the fatigue strength is due to an increase in the resistance to crack growth resulting from changes in the structure and substructure brought about in the steel by the high-temperature treatment and microalloying with the rare earth metal. |
| 3. | High-temperature thermomechanical treatment of steel 1Kh17N2 and its alloying with 0.1% La raise the corrosion resistance of the steel and reduce its tendency to intercrystalline corrosion. |
| 4. | The increase in the corrosion resistance of steel 1KM7N2 after the high-temperature treatment and microalloying with the rare earth metal is caused by the structural changes produced in the steel by the treatment and the microalloying. |
7.
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. |
8.
| 1. | A method was developed for transforming quasilinear equations of viscoelasticity constructed on the basis of the strain summation principle. |
| 2. | It was shown that a simplified variant of the equations containing two creep kernels can be used to describe experimental data. |
| 3. | The structure of the relations that were obtained shows that, as in the linear theory of viscoelasticity, equations having resolvent creep operators are the simplest to transform. |
9.
M. V. Bol'shakov V. N. Palash V. N. Yus'kiv M. M. Nerodenko E. A. Asnis 《Strength of Materials》1988,20(2):172-176
| 1. | The method of determining the static cracking resistance using, as the criterion, the values of the J-integral is more suitable for testing small specimens of niobium alloys with a high ductility margin. |
| 2. | The static cracking resistance characteristics of the welded joints in 5VMTs alloy with solid-solution hardening are considerably higher than those other welded joints in NTsU heterophase alloy. |
| 3. | When the welding speed is increased from 2.8 to 16.6 mm/sec, with a corresponding reduction of the heat input from 1480 to 760 J/cm, the cracking resistance of both the weld metal and HAZ of the examined alloys increases. |
| 4. | Subsequent heat treatment for 1 h at 1473°K increases the cracking resistance of the welded joints. |
10.
| 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. |
11.
N. M. Aptekar' S. L. Babchenko G. M. Vorob'ev G. V. Yashnaya O. D. Smiyan 《Materials Science》1976,11(6):650-652
| 1. | Selective absorption of hydrogen (at active centers) takes place on the working surface of railway crossing points made of steel G13L. |
| 2. | High hydrogen concentrations are found in the metal adjacent to exfoliation; these concentrations reach a maximum in layers situated at a distance of 0.5–1 mm from the exfoliation surface. |
| 3. | In an exfoliation zone the hydrogen concentrations are considerably greater than the initial values. |
| 4. | Splashes of hydrogen concentrations are observed in regions of the surface layers of the crossings in which flakes are not actually visible; the state of the metal can then be described as the preflaking stage. |
12.
| 1. | On the basis of an analysis of the equations describing the kinetics of creep crack growth, a new generalizing kinetic equation is suggested; it makes it possible to estimate the effect of the stresses in the cross section, of the SIF, and of the temperature on this process. |
| 2. | It was shown that in dependence on the state of the steel and with the aid of a new kinetic equation it is possible to establish the optimal variant of taking the geometric factor into account in describing the crack growth rate. |
| 3. | It is suggested to compare the creep crack resistance of creep resistant steels according to their resistance to impermissible (impermissible from the point of view of operating conditions) crack growth rate, determined on specimens without initial bending stresses. |
13.
| 1. | Sheets of the Zr- 1% Nb alloy were used for the first time to show by experiments the crystallographic reorientation of the grains at the tip of the moving crack. |
| 2. | The effects detected by x ray diffraction examination in the vicinity of the fracture of the specimens with the notch, were compared with the effects recorded in the volume of similar smooth specimens subjected to tensile loading. According to the estimates, in the layer up to 20m thick, adjacent to the fracture surface, the average strain of the material in tensile loading is 15–20% for the RD specimen and 3–5% for the TD specimen. |
| 3. | Anisotropy of the cracking resistance and development of the zone of plastic deformation at the tip of the moving crack are determined by the activating mechanism of plastic deformation of alpha zirconium whose special feature is the strong dependence on the crystallographic orientation of the grains. |
14.
I. D. Abushenkov A. I. Alekseev V. Ya. Il'ichev N. I. Mokryi A. I. Telegon V. K. Chernetskii 《Strength of Materials》1988,20(5):698-702
| 1. | Equipment was developed and the test procedure proposed for fracture toughness testing compact specimens of structural materials in off-center loading at low temperatures down to 4.2°K. |
| 2. | The strain gauges and dynamometer operating-directly in the cryogenic liquids were produced and calibrated at various temperatures. These devices can be used to record the (P–V) and (P–f) diagrams during testing. |
| 3. | Preliminary tests were carried out on the specimens of 03Kh18N16G4A and 03Kh18N6G4 steels at 300, 77, and 4.2°K. The cracking resistance of the tested specimens at 4.2°K was evaluated on the basis of the values of KIc whereas the parameters KQ and K C * were used for evaluation at 77 and 300°K. |
| 4. | The results show that 03Kh18N16G4A steel at 4.2°K has the optimum high values of both the yield stress (1600 MPa) and fracture toughness (104 MPa·m1/2). Having relatively high values of 0, 2 (1400 MPa), 03Kh18N6G4 steel has at 4.2°K unacceptably low freacture toughness parameters indicating that the steel fails by brittle fracture in these conditions. |
15.
| 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. |
16.
O. G. Zotov Yu. N. Koval' S. Yu. Kondrat'ev B. A. Chaikovskii G. Ya. Yaroslavskii 《Strength of Materials》1989,21(3):401-406
| 1. | The damping capacity and the structure of the -alloys of the Cu–Al–Zn system after quenching in air are determined by the general degree of alloying expressed by the electron concentration and by the ratio of the alloying elements. |
| 2. | The alloys with the electron concentration e/a<1.45–1.48 show=" diffusion=" breakdown=" and=" the=" level=" of=" damping=" capacity=" increases=" with=" the=" increase=" of=" electron=" concentration=" as=" a=" result=" of=" the=" increase=" of=" the=" amount=" of=" martensite=" in=" the=" structure.="> |
| 3. | In the alloys with the electron concentration e/a>1.45–1.48 the damping capacity is determined by the ratio of the two types of martensite present in the structure, 2H and M18R. The amount of M18R martensite increases with the increase of the zinc content and reduces the damping capacity and, conversely, the increase of the aluminum content increases the amount of 2H martensite and also increases the damping capacity. |
17.
A. V. Prokopenko Yu. K. Petrenya V. N. Ezhov I. A. Makovetskaya M. M. Ivakhov 《Strength of Materials》1989,21(1):39-43
| 1. | At high temperatures the fracture surface changes from being brittle and along crystallographic planes to quasiductile both in polycrystalline, and in monocrystalline alloys. This increases the fatigue crack growth rate. |
| 2. | As the temperature is increased from 1073 to 1273 K, the rate of high-temperature corrosion increases, especially in polycrystalline material. |
| 3. | The fatigue crack growth rate is higher in polycrystalline alloys than in monocrystalline alloys with a <111> orientation, and is lower in monocrystalline alloys with a <001> orientation, i.e., they have an intermediate rate in comparison to specific orientations of the grain. |
| 4. | The advantages of using monocrystalline alloys in increasing the fatigue crack growth resistance are only realized when the orientations of its most resistant planes are advantageously aligned along the direction of highest tensile stress both during brittle shear fracture at 293 K and, during quasiductile fracture at 1073-1273 K. |
18.
| 1. | On the basis of the experimental investigation of the regularities governing creep of steels 15Kh2MFA and 08Kh18N9 under conditions of a state of plane stress we suggested an equation which makes it possible to determine the minimal creep rate intensity of material in a state of plane stress. As basic data we used the results of creep tests obtained, e.g., under conditions of uniaxial tension and torsion at equal stress intensity levels and at constant test temperature. |
| 2. | We suggested a criterion of creep of material in the case of a state of plane stress, experimentally substantiated on steels 15Kh2MFA and 08Kh18N9. |
| 3. | We furnished a quantitative evaluation of the effect of the type of state of stress on the relative minimal creep rate intensity. |
19.
| 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. |
20.
A. Ya. Krasovskii V. A. Makovei G. N. Nadezhdin V. L. Svechnikov G. V. Stepanov 《Strength of Materials》1988,20(2):137-142
| 1. | The velocity dependence of dynamic fracture toughness can be evaluated by the method of quantitative stereoscopic fractography within a broad range of loading rates. |
| 2. | For steel 40Kh the ascending branch of the velocity dependence of KId is determined by fragmentation of the structure causing ramification of the crack which, in the final analysis, increases fracture toughness. The reduced size of the microcrack in fragmentation is directly connected with the weakening of the dependence of crack resistance on the loading rate [19], which in our experiments corresponds to the range of impact speeds of 300–600 m/sec. |
| 3. | Removal of microsegregations from the boundaries forming upon fragmentation of blocks in the structure (by means of diffusion) increases the surface energy of such boundaries, impedes the formation of microcracks on them, and consequently increases fracture toughness. |