共查询到20条相似文献，搜索用时 342 毫秒
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.
|
相似文献
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.
|
相似文献
3.
| 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.
|
Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 28, No. 1, pp. 33–37, January–February, 1992. 相似文献
4.
| 1. |
The order of the calculated and experimental stresses and the character of their variation at the sections of the unit are in satisfactory agreement. This is applicable to both toroidal and poloidal forces. The experiment confirmed that the section 2-2 of the unit is maximally loaded.
| | 2. |
The maximum divergences between the calculated and experimental data are observed at the section of the unit adjoining the cylinder (2-2) where the aforementioned differences between the model and the actual unit has the strongest effect. The divergences decrease if the supports of the unit on the cylinder flanges are not taken into account in the calculations (these results are drawn in Fig. 5 with dashed lines).
| | 3. |
In accordance with the experiment data, the presence of a gap along the lines 1–2 and 3–4 raises the maximum stress in the model by 30...40% as compared to the same in a variant without the gap (35% according to calculations [2]).
| | 4. |
The divergences between the calculated and experimental values of the displacements of the characteristic points of the unit do not exceed 20%.
|
In this manner, the results of the modeling investigations confirm the utility of the calculated model used in designing the TFSC unit of the T-15 installation. 相似文献
5.
| 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
6.
| 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
7.
| 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.
|
相似文献
8.
Conclusions The conclusions are summarized as follows:
| – |
• The operation of a new three-salt-carbon chemical heat pump was experimentally verified.
|
| – |
• A heat output of 1.5 kW was tested with a temperature lift near 100°C with a COP equal to 1.44 without heat recovery.
|
| – |
• With heat-pipe heat recovery the COP of this system can be increased to 1.62.
|
| – |
• The efficiency of this heat pump can be increased if for the bottom cycle a condenser and a capillary pumped evaporator
are used.
|
| – |
• To increase the cycle efficiency it is necessary to improve the design of the adsorber, increase the number of salts with
different temperature lifts, and use a convective mode for sorbent-bed heating.
|
| – |
• A four-salt heat pump could potentially be used to increase the COP of the system further, provided other parasitic losses
can be reduced.
|
Finally the advantage of no moving parts makes this cooler/heater attractive for space and domestic applications.
Academic Scientific Complex “A. V. Luikov Institute of Heat and Mass Transfer of the National Academy of Sciences of Belarus,”
Minsk. Published in Inzhenerno-Fizicheskii Zhurnal, Vol. 72, No. 3, pp. 595–600, May–June, 1999. 相似文献
9.
Abstract and Key Results
| ▪ |
In this paper I test the theory that internal capital markets are a motivation for both corporate diversification and vertical
integration. I use a sample of 1560 firms from 39 countries.
|
| ▪ |
Using this data I also test theories about vertical integration and capital market development. I also test agency cost and
taxation theories of diversification and vertical integration.
|
| ▪ |
I find a significant and negative relationship between corporate diversification and capital market development
|
| ▪ |
I find a significant and positive relationship between vertical integration and capital market development.
|
相似文献
10.
| 1. |
Cladding of high-strength steel with type 08KhN2GMTA deposited metal aids in increasing the resistance to failure of plate metal under repeated static biaxial bending in a 3% sodium chloride solution.
| | 2. |
With an amplitude of operating stresses of 70% of the yield strength of the high-strength steel the cladding layer at first experiences plastic deformation, which leads to the formation of residual stresses and a change in the degree of asymmetry of the subsequent load cycles of the external layers in a favorable direction.
| | 3. |
The appearance in the cladding layer of residual compressive stresses and the decrease on the sample surface of the maximum tensile stresses aids in increasing the resistance to the origin and initial growth of a corrosion-fatigue crack.
|
相似文献
11.
| 1. |
The use of the method developed for determining the main deformations of microvolumes makes it possible to investigate peculiarities of metal deformation in microareas and the actual level of micrononuniform deformation, taking into consideration the form of stressed condition
| | 2. |
A definite character of distribution of the main deformations across microareas, reflecting not only the influence of the form of stressed condition of the macrovolume of a sample, but also the peculiarities of interaction of individual microvolumes which are found in stress deformed conditions differing from the stress deformed condition of the individual body, corresponds to each form of stressed condition. For complex loading a change in the form of distributions of deformations in changing from one form of loading to another is characteristic.
| | 3. |
In the plane stressed condition under conditions of simple and complex loading there is intense slip formation accompanied by activation of a larger number of slip systems than in uniaxial loading, which is an indication of the more complex deformation conditions of individual microvolumes.
| | 4. |
Differences in the distribution of main deformations across microareas, nonuniformity of the stress deformed conditions of microvolumes, and peculiarities of the character of slip formation undoubtedly play a major role in the formation of mechanical properties in the given forms of stressed condition and methods of complex loading.
|
相似文献
12.
| 1. |
In dependence on the strain-hardenability of material determined by the type of crystal lattice, the test temperature, by alloying and work-hardening, loss of stability may cause either strict localization of deformation in the neck or smooth transition from uniform deformation to concentrated deformation in static tension of a smooth cylindrical specimen.
| | 2. |
In compression, torsion, bending, tension in a state of plane stress and other kinds of tests, the margin of strength of the part and its technological and design strength are determined chiefly by the magnitude of the ratio of yield strength to true tensile strength (and not ultimate tensile strength), and also by the magnitude of relative contraction, i.e., by parameters characterizing the capacity of material to the nucleation and development of flaws in it under plastic deformation.
| | 3. |
Uniform deformation and the magnitude of the ratio 0.2/u play an important role in ensuring the load-bearing capacity of a structure, in particular, when cylindrical parts are subjected to tensile loads. In that case loss of stability of uniform deformation leads to reduced strength of the part, and essentially it is the onset of failure.
|
Leningrad. Translated from Problemy Prochnosti, No. 4, pp. 49–53, April, 1989. 相似文献
13.
| 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
14.
| 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
15.
| 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.
|
相似文献
16.
| 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.
|
相似文献
17.
| 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.
|
相似文献
18.
| •
|
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.
|
相似文献
19.
Abstract and Key Results
| •
|
This study discusses the underlying reasons for the variant nature of the relationship between multinationality and firm performance
in the context of service firms.
|
| •
|
To date, this line of research has mostly used evidence from manufacturing firms, despite the ever-increasing contribution
of service firms to national and global economies.
|
| •
|
We conduct an exploratory study using case analyses of large European retail banks. We argue that the nature of the multinationality-performance
relationship for services is moderated by industry characteristics, market-based factors and firm-specific factors.
|
| •
|
We conclude that the shape of the curve depicting the multinationality-performance relationship of retail banks experiences
substantial variations on a single case level.
|
| •
|
Our exploratory study of retail banks shows that the multinationality-performance relationship varies significantly depending
on banks’ strategic decisions regarding branch network configurations, product portfolios, branding strategies, organizational
architecture (HQ-subsidiary relationship), and social networks. Any generalization of the relationship is difficult and prone
to error.
|
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
|
|
