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1.
1.  Plastic deformation in polycrystalline copper develops unevenly in the microregions in both the linear and the plane stress state (including plane stress under conditions of complex loading). A higher level of microinhomogeneity in deformation was observed in the plane stress state.
2.  The immobilization and duplication of microcenters of increased and reduced deformation in simple loading is a general property of polycrystalline materials and is in independent of the nature of the material and the type of stress state.
3.  The development of deformations in individual microsectors in conditions of complex loading (axial tension—uniform biaxial tension—transverse tension) differs substantially from that in simple loading. The difference lies in the varying degrees of localization of deformation of fixed microsectors.
4.  In a plane stress state, especially under conditions of complex loading, deformation is due to the action of a larger number of slip systems than in a linear stress state; this must indicate more complex deformation conditions in the individual microvolumes.
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2.
1.  Polycarbonate specimens enable direct observation of the stress-strain pattern during the loading process.
2.  It has been shown that under plane strain and plane stress conditions the crack starts at the boundary of the elastic-plastic deformation zone at the moment when the normal stress component reaches the critical value.
3.  Under plane strain conditions the value cr is determined by the yield point and the radius of the notch n. Under plane stress conditions the strip of plastic deformation functions, as a stress concentrator. Fracture occurs when the normal stress component at the boundary reaches the critical value.
4.  During the intervals when the specimen is not loaded the plastically deformed zones act as concentrators of residual stress. When load is again applied there is interaction between the residual stresses and the externally induced stresses.
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3.
a)  The study describes the basic fracture micromechanisms of porous materials with dominantly ferritic matrix structures.
b)  Quantitative fractography is used to describe the basic mechanisms of crack propagation in the porous body corresponding to the non-monotonous temperature dependence of fracture toughness values.
c)  Behavior of fracture toughness values and relevant fracture micromechanisms indicate that the state of plane deformation in microvolumes in front of the crack tip cannot be reached at higher porosities and temperatures. This piece of information corresponds to the knowledge of independence of fracture toughness values of porous materials on the specimen thickness, as is presented in the literature [5].
Published in Fiziko-Khimicheskaya Mekhanika Materialov, No. 2, pp. 41–44, March–April, 1992.  相似文献   

4.
1.  The flexibility of the contact-zone/block system is determined experimentally from impact tests. In the case when high loading rates are used and massive specimens are tested, plastic deformations develop in the contact zone; this leads to effective values on the low side.
2.  The duration and total amplitude of the resultant KI-t and P-t curves for supportfree tests are determined primarily by the flexibility of the specimen, while their character (the number of peaks, and their amplitude) is determined by the ratios of the flexibilities of specimen and block.
3.  A method of calculating KI for a support-free impact loading is theoretically substantiated and experimentally confirmed.
4.  During the impact testing of specimens on supports, separation of the specimen from the supports occurs at the initial time, i.e., these tests are actually support-free at the initial time. The moment of repeated contact between the specimen and the supports of the impact-testing machine corresponds approximately to time required for the force to reach the local minium.
Institute of Strength Problems, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Problemy Prochnosti, No. 5, pp. 25–29, May, 1989.  相似文献   

5.
1.  As a result of introduction of the system, the possibility of loss of information on the vibration condition of an engine has been eliminated, especiallyin short time appearance of vibrations in failure situations when the vibrations increase very rapidly.
2.  The measuring accuracy has been increased.
3.  Recording of the parameters of vibrations in combination with other parameters characterizing the operation of the engine is provided.
4.  The process of interpreting and treating the test results has been accelerated.
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6.
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.
Translated from Fiziko-Khimicheskaya Mekhanika Materialov, No. 2, pp. 7–13, March–April, 1992.  相似文献   

7.
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.
Electric Temperature Measurement Special Design Office, Lvov. Translated from Problemy Prochnosti, No. 12, pp. 111–113, December, 1988.  相似文献   

8.
1.  We proposed a method which can be used to examine the kinetics of failure and cracking resistance of the materials taking into account the type of thermal effect.
2.  The results show that the variation of the temperature conditions during macrocrack propagation has a controlling effect on force and energy characteristics of failure and on the change of the failure micromechanisms. This effect differs for different types of materials.
3.  Electron fractographic examination showed that the level and nature of damage in the material obtained in the previous stage of thermal loading greatly affects the relationships governing the propagation of the macrocrack after a temperature change.
4.  It is shown that it is important to take into account the history of thermal loading (direction and temperature variation amplitude) in determining the cracking resistance of materials and structures.
Institute of Strength Problems, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Problemy Prochnosti, No. 2, pp. 12–16, February, 1989.  相似文献   

9.
Comparing the fracture toughness temperature curves evaluated at static and rapid loading on larger (SENB, 1CT) specimens with the fracture toughness curve determined on precracked Charpy specimens at impact loading, the following conclusions can be drawn:
–  both rapid and impact loadings cause the shift of fracture toughness temperature curve to higher temperatures in accordance with the concept of critical tensile stress criterion;
–  the transition temperature region with brittle (cleavage) initiated fracture after some ductile crack growth is, at rapid loading, shifted to higher temperature as well;
–  at the impact loading of small PC specimens the whole transition region is reduced to one transition temperature only and therefore sharp increase from the lower shelf fracture toughness region to the upper one occurred. This ductile to cleavage initiation transition temperature is, in spite of the impact loading, lower than that of the larger 1CT specimens loaded at a much smaller loading rate;
–  for cleavage initiated fracture of low alloy steel only lower shelf fracture toughness values can be measured by employing the PC specimens and the impact loading.
Published in Fiziko-Khimiches-kaya Mekhanika Materialov, No. 3, pp. 54–60, May–June, 1992.  相似文献   

10.
1.  We derived an equation which can be used to determine the endurance in cyclic loading on the basis of the crack initiation criterion in elastoplastic deformation of the material and the triaxial stress state.
2.  Rapid fatigue damage cumulation can take place in the material only if the size of the reversible elastoplastic zone is larger than the grain diameter.
3.  The assumption on the homogeneity of SSS in the structural element makes it possible to describe most adequately the relationship between the strain and fatigue damage of the material.
4.  We derived an analytical expression linking the threshold value of the stress intensity factor \GDKth with the mechanical properties and grain diameter of the material.
5.  A model of fatigue crack propagation which is based on the approximate analytical solution of the cyclic elastoplastic problem of the SSS in the vicinity of the crack tip was developed. The model takes into account the special features of deformation of the material in the conditions of the triaxial stress state and also uses the assumption on the homogeneity of SSS in the structural element. The main advantages of the model are as follows: it can be used to determine the crack growth rate in cases in which the variation of the range of the stress intensity factor in the structural members takes place at the variable loading asymmetry;  相似文献   

11.
1.  Conditions have been established providing existence and uniqueness for solutions to general boundary-value problems in strain plasticity theory, which incorporates the stress deviator form. An iterative process has been proposed for solving nonlinear boundary-value problems, and optimal convergence-rate bounds have been defined. Conditions have been formulated under which simple loading occurs.
2.  The results are applicable to formally similar problems in creep involving ageing theory with the incorporation of the stress deviator form.
Translated from Problemy Prochnosti, No. 9, pp. 97–107, September, 1988.  相似文献   

12.
Abstract and Key Results
▪  Subsidiary managers are faced with complex managerial roles involving both the interests of the multinational corporation (MNC) and the subsidiary. We suggest complex roles are best fulfilled when managers develop dual organizational identification towards both entities.
▪  Based on a conceptualization of dual organizational identification in terms of relative magnitude, we test the effect of dual identification on subsidiary manager roles and role conflict.
▪  Results indicate that high identification with both entities is associated with high role fulfillment and that similarity in organizational identities directly affects role conflict.
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13.
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.
Translated from Fiziko-Khimicheskaya Mekhanika Materialov, No. 5, pp. 7–11, September–October, 1992.  相似文献   

14.
1.  Within the range 500–10,000 Hz the cyclic loading frequency has practically no effect on the fatigue resistance of the IMV-2 alloy, while for the AMg6N alloy at an increase of loading frequency to 10 kHz the fatigue limit of smooth specimens increases monotonically.
2.  The effective stress intensity coefficients and the coefficients of the welding effect do not change during transition to higher loading frequencies which permits them to be determined from the results of high-frequency tests on the required loading bases.
3.  On each of the investigated loading frequencies the scatter of fatigue life values of broken welded specimens and of specimens with stress concentrators is greater than that of smooth specimens of the initial material. This must be taken into account in calculating and predicting the cyclic fatigue life of structural elements and machine components.
Institute of Strength Problems, Academy of Sciences of the Ukrainian SSR, Kiev. Miass. Translated from Problemy Prochnosti, No. 7, pp. 23–28, July, 1988.  相似文献   

15.
•  This paper shows that the role of managerial incentives is highlighted by a relatively complex relationship between technological competence and international diversification. By studying a sample of Standard & Poor’s 500 member firms, we explore the relationships between technological competence, managerial pay, and international diversification.
•  Results indicated a curvilinear relationship (an inverted U-shape) between technological competence and international diversification.
•  In line with agency theory, contingent pay (stock options and bonuses) was positively related to international diversification.
•  Beyond these direct effects, both contingent and non-contingent pay (cash compensation) moderated the relationship between technological competence and international diversification.
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16.
1.  The strength of an unnotched specimen after both natural and artificial aging is higher in biaxial tension than in axial and for both structural conditions is 1.12t of the material.
2.  The sensitivity of the material to these stress raisers in axial tension is revealed more strongly for D16T1 alloy and is 0.9t of the material while in biaxial tension for both structural conditions is greater than t of the material (1.04–l1.16t).
3.  In axial and biaxial (2/1=0.5) tension of sheet in the plastic area the rivet body does not participate in deformation of the material all the way to failure of it (Fig. 2).
4.  It was established that in both methods of loading the presence of a rivet both without and with interference leads to redistribution of the deformed condition, and the lower the plasticity of the material, the more sharply it occurs. For example, for D16T1 alloy the curve of the deformed condition on the edge of the rivet has the minimum value (Fig. 1), and for D16T alloy the maximum.
Vladimir Polytechnic Institute. Translated from Problemy Prochnosti, No. 3, pp. 110–112, March, 1989.  相似文献   

17.
1.  Deformations of cylinder liners and blocks of small Diesel engines reduce the life of the engines and have an adverse effect on other technical and economic indicators. Reduction of nonuniformity of deformation of cylinders in assembly by 15–20% increases the life of parts of the cylinder and piston group by more than 20%.
2.  The newly devised method of theoretical and experimental investigation of the state of stress and strain of cylinder liners in different cases of their loading in the process of assembly showed good agreement of the results with the data of statistical analysis of the deformation, and the method can therefore be recommended for the stress analysis of engines with other standard sizes and technological processes of their assembly.
3.  The forces arising in the assembly of small Diesel engines in the mating parts lead to nonuniform deformations of these parts. For instance, pressure of the rubber gaskets causes the working surface of the cylinder to assume barrel shape, and nonuniform structural rigidity of the bearing surfaces of the cylinder block is the cause of ovality of the cylinder bores.
4.  The introduction of design and technological methods of reducing deformation helped improve the technical and economic indicators of Diesel engines (in particular, the life of cylinder liners was extended by more than 20%).
Dagestan Polytechnic Institute, Makhachkala. Translated from Problemy Prochnosti, No. 6, pp. 110–114, June, 1988.  相似文献   

18.
1.  With thermal cycling loading for coated specimens microracks occur in brittle coating layers, and conditions for their formation depend not only on coating composition, but also on the composition of the metal being protected, and operating conditions (time, temperature).
2.  Propagation of thermal fatigue microcracks into the basic metal is determined not only by the difference in linear thermal expansion coefficients, elasticity moduli of the coating and basic metal, but it also depends on the thickness of the coating, cycle parameters, aggressivity of the corrosive medium, relative position of the cracks formed, and the level of heterogenetiv for the coating itself.
3.  In order to provide reliable protection for turbine blades from corrosion, coating selection should be carried out with reference to actual operating conditions and the grade taking account of chemical composition) of the basic material.
4.  Numerical evaluation of the features of surface microcrack growth from coatings into the basic metal with thermal cycling loading should be carried out on the basis of threshold aggressivity of the corrosive medium.
I. I. Polzynov Central Institute of Boiler Turbines, Leningrad. Translated from Problemy Prochnosti, No. 12, pp. 30–35, December, 1988.  相似文献   

19.
1.  Singular elements with a notch of an arbitrary angle were constructed to determine the stress fields near through notches.
2.  To increase the accuracy of the solution, we constructed transitional singular elements which increase the size of the region re in which singularity is modeled and decrease the incompatibility between the regular and notched singular elements.
3.  A procedure was developed for determining the stress field near notches under dynamic loadings.
4.  The stress intensity factor near small-angle notches differs negligibly from the stress intensity factor near cracks of the same length under static and dynamic loadings.
5.  The finite elements that were constructed make it possible to reliably solve linear fracture mechanics problems by the finite elements method with the use of very coarse idealizations.
The above approach was realized in the program system POLIFEM for the ES series computer (by MOFAP Gosstroya SSSR).  相似文献   

20.
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.
Zhitomir Branch of the Kiev Polytechnic Institute. Translated from Problemy Prochnosti, No. 5, pp. 88–92, May, 1988.  相似文献   

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