共查询到20条相似文献，搜索用时 437 毫秒
1.
| 1. |
The optimum design theory was used to derive equations for optimizing the stress-strain state in the thick-walled pipe with the elasticity modulus varying along the radius and loaded with the internal pressure.
| | 2. |
A numerical method of determining the law of the optimum distribution of the elasticity modulus along the radius of the thick-walled pipe was proposed.
| | 3. |
The results show that by corresponding changes of the elasticity modulus in the given range along the pipe thickness it is possible to reduce the maximum annular stresses on the internal surface of the pipe. This stress reduction in a ratio expressed in per cent is approximately equal to the variation range of the elasticity modulus.
| | 4. |
The minimum annular strains were recorded in the homogeneous pipe produced from the material with the maximum possible elasticity modulus.
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Izhevsk Institute of Mechanics. Translated from Problemy Prochnosti, No. 2, pp. 88–91, February, 1988. 相似文献
2.
| 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
3.
| 1. |
Singular elements with a notch of an arbitrary angle were constructed to determine the stress fields near through notches.
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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.
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The above approach was realized in the program system POLIFEM for the ES series computer (by MOFAP Gosstroya SSSR). 相似文献
4.
| 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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5.
| 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.
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Institute of Strength Problems, Academy of Sciences of the Ukrainian SSR, Kiev, Leningrad. Translated from Problemy Prochnosti, No. 1, pp. 44–47, January, 1988. 相似文献
6.
| 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%.
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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
7.
| 1. |
The variance approach to calculating the deflection rate of the crept sheet is more universal from the mathematical viewpoint than the previously used methods since it makes it possible to reject the assumptions on the reduction of the problem to unidimensional (disregarding the side edges of the billet) and on the coincidence of the tensor of the bending moments with the tensor for the elastic sheet, which distort the real situation.
| | 2. |
The calculated results greatly increase the accuracy of the existing theoretical pattern of the deflection of the rectangular sheet. Specifically, the results show that at low values of the exponent in the creep dependence the deflection rate in the center of the sheet stabilizes at a considerably higher ratio of the long to the short side than at the value =1 which corresponds to the elastic and linearly crept sheets.
| | 3. |
Taking into account the assumption of the homogeneity of the material of the sheet, it is recommended to use the method in combination with the calculation models which take into account the heterogeneity of the material and the thickness of the sheet.
| | 4. |
The proposed method can be used for the quantitative calculations of the deflection of the sheets with both the creep and plasticity properties with the exponential hardening law.
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The results of these calculations are used in selecting the design parameters (spacing) of the guiding roller system for continuous casting installations for steel billets designed at Uralmash Production Organization. 相似文献
8.
Conclusions The conclusions are summarized as follows:
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• The operation of a new three-salt-carbon chemical heat pump was experimentally verified.
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• 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.
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• With heat-pipe heat recovery the COP of this system can be increased to 1.62.
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• The efficiency of this heat pump can be increased if for the bottom cycle a condenser and a capillary pumped evaporator
are used.
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• 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.
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• A four-salt heat pump could potentially be used to increase the COP of the system further, provided other parasitic losses
can be reduced.
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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.
| 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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10.
Abstract and Key Results
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This study discusses the underlying reasons for the variant nature of the relationship between multinationality and firm performance
in the context of service firms.
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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.
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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.
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We conclude that the shape of the curve depicting the multinationality-performance relationship of retail banks experiences
substantial variations on a single case level.
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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.
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11.
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This paper examines cross-border mergers and acquisitions undertaken by U.S. companies to determine whether geographic distance
directly affects these firms’ governance decisions.
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We find that U.S. firms tend to acquire higher stakes in geographically proximate targets than in remote ones. |
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The paper also investigates the moderating effect of geographic distance on cultural distance and political risk. We find
that as these two hazards increase, acquirers prefer shared ownership for proximate deals, and full ownership for acquisitions
of geographically distant targets. These findings indicate that the previously-reported effects of cultural distance and political
risk on FDI are not absolute, but they are moderated by geographic distance.
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12.
| 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.
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13.
| 1. |
It was found that the moire-band method that the stress-strain state in the working part of biaxially compressed samples of glasses and pyroceramics, whose ends are cemented into the grooves of rigid metal bearing races, has satisfactory uniformity throughout the entire stage of loading, whereas the principal stresses coincide in direction with the loads applied to the contour.
| | 2. |
The average compressive stresses in a biaxially compressed sample plate whose ends are cemented into the grooves of metal races, loaded over at least 95.5% of the lateral surface, may be calculated by dividing the applied load by the area of the contact surfaces between the sample and races.
| | 3. |
The accuracy of experimental deformation diagrams, plotted from the results of interpreting moire-band patterns obtained in systems of parallel lines with 0.02-mm spacing, is higher by a factor of 1.5–2 than that of such diagrams plotted from tensometric data.
| | 4. |
When brittle glass- and pyroceramic-type materials are compressed by smooth metal punches, high contact stresses appear, and stress concentrators are formed which cause premature fracture of the samples and understated results.
| | 5. |
Owing to the possibility of maintaining the initial end conditions up to high working stresses on compression of glass and pyroceramic samples whose ends are cemented into the grooves of metal races, samples for testing other brittle, high-strength materials, e.g., high-alumina ceramics, porcelain, etc., are promising.
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14.
Abstract and Key Results
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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.
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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.
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I find a significant and negative relationship between corporate diversification and capital market development
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I find a significant and positive relationship between vertical integration and capital market development.
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15.
| 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.
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相似文献
16.
Abstract and Key Results
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We explore the differences in international strategy between multinational enterprises (MNEs) in services and manufacturing,
especially in terms of their international diversification, as measured by their sales and asset dispersion.
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Our longitudinal data show that the largest MNEs in services have a much stronger home-region orientation than manufacturing
MNEs. Large MNEs in the services sector average 83.9 percent of their sales in their home region, which is significantly higher
than large manufacturing firms at 65.6 percent.
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We explore the possible reasons for the relative lack of globalization of services firms. The two main reasons are: the difficulty of adapting separately upstream activities and downstream activities in high distance host environments, and the difficulty of selecting activity locations as a function of supply side criteria.
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We offer a refinement of regional strategy theory applicable to services MNEs. |
相似文献
17.
| 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.
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Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 28, No. 1, pp. 33–37, January–February, 1992. 相似文献
18.
| 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.
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Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 28, No. 4, pp. 35–40, July–August, 1992. 相似文献
19.
| 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.
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相似文献
20.
| 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.
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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.
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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 the load and energy absorption in the penetration depth function are proportional to 2 and 3, respectively.
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