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1.
| 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. |
2.
S. B. Kasatkin 《Strength of Materials》1976,8(11):1346-1350
| 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. |
3.
A. Lamure S. Mezghani M. F. Harmand C. Lacabanne 《Journal of materials science. Materials in medicine》1996,7(3):175-179
Thermally stimulated current spectroscopy has been applied to the investigation of molecular mobility in human calcified tissue. A comparative study of extracts and residues at various stages of demineralization is presented. Results show that:
Biomaterials for orthopaedic prostheses require the same morphology in order to phenomenologically reproduce the same dynamic behaviour. 相似文献
| – | the matrix (collagen) is in a glassy state at physiological temperature; |
| – | the filler (apatite) increases the static modulus; |
| – | the interfaces/interphase (non-collagenous proteins and particularly proteoglycans) ensure cohesion and ductability for the composite. |
4.
M. Arita 《Strength of Materials》1976,8(11):1274-1280
| 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. |
| 4. | 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. |
| 5. | 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. |
5.
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. |
6.
| 1. | The fracture of heat-resistant alloys and tool steels under the influence of thermal cycling may be quasistatic, fatigue, or mixed in character. |
| 2. | Quasistatic fracture as a result of thermal cycling takes place with the specimen working portion remaining constant (hard loading mode); it is caused by the accumulation of strains of opposite signs in local material volumes. |
| 3. | The accumulation of residual strains in local specimen volumes for thermoplastic strain materials is due to the mismatch of plastic strain fields along the specimens during the heating and cooling cycles. |
| 4. | Under thermal cycling conditions (as in isothermal low-cycle fatigue) the static damage is measured in terms of the accumulated plastic strain (of a given sign), while the fatigue damage is measured in terms of the magnitude of the plastic strain per cycle. Quasistatic fracture takes place in regions of the maximum accumulated plastic strain which is equal to zero in the zone of fatigue fracture. |
7.
M. N. Georgiev N. Ya. Mezhova E. M. Morozov V. A. Reikhart 《Strength of Materials》1988,20(9):1133-1138
| 1. | It was establised that crack resistance limit Ic determined in full-profile nonheat-treated rails with cross fatigue cracks of area 10...30% of the rail head cross-sectional area is practically constant. The breaking stress c in all the cases is lower than the elastic limit c of the materials, in view of which, its crack resistance limit can be considered as a critical coefficient of the stress intensity for a plane deformed state, i.e., IcKIc. |
| 2. | For the non-heat-treated rails P65 with cross fatigue cracks (defect-21) KIc=37.5 MPa m. |
| 3. | The KIc values determined in full-profile non-heat-treated rails with cross fatigue cracks of area 10...30% of the rail head cross-sectional area practically does not differ from the results obtained as per GOST 25.506-85 in specimens taken from the same rails. |
| 4. | The KIc values for the non-heat-treated rails P65 with cross fatigue cracks decrease on the average by 40% for a test temperature drop from –253 to –333°K. |
8.
| 1. | The described general method of designing structural elements (a type of thin nonsloping shell of revolution) under cyclic loading, which has been approved for the case of a spherical notched shell, is effective, and can also be employed for other types and shapes of thin-wall designs of constant or variable thickness. |
| 2. | Stabilization of the stress state during cyclic loading is heavily dependent on the applied-loading rate and occurs (according to the results of the design and experiments under consideration) during the 2–10th loading cycle for a load range of 10q25 kg/cm2. |
| 3. | As the loading in the shell increases, the stress concentration diminishes from a value k=3.5, which corresponds to the elastic state, to 1.3 at which point the strain concentration reaches a maximum value with q=15 kg/cm2 for the material in question, and then decreases; this is associated with the transition of the shell into the plastic state. These results can be used to evaluate the low-cycle strength of standard structural elements, and to determine the factors of safety and the bearing capacity under cyclic loading. |
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:
Published in Fiziko-Khimiches-kaya Mekhanika Materialov, No. 3, pp. 54–60, May–June, 1992. 相似文献
| – | 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. |
10.
| 1. | The dependence of the growth rate of a fatigue crack on the stress intensity coefficient at the tip of the crack is described by an exponential function of the da/dN=CKn type for all zones of a welded joint. For a given applied stress and realizable values of K the index n in this function has a constant value, differing for each particular zone. |
| 2. | The instantaneous and average crack velocities reach their maximum values in the heat-affected zone and their lowest values in the seam metal. The crack growth rate in the parent metal is close to that in the heat-affected zone. |
| 3. | The fatigue life of a weld subjected to cyclic (fatigue) loading may to a first approximation be estimated by the n and C values of the parent metal. |
11.
Abstract and Key Results
相似文献
| • | This paper introduces innovation, competition and regulatory change as dominant themes in international business. |
| • | These themes represent focussed trajectories for future research despite diversity in their causes, processes and consequences and the interactions between them which reflect the increasingly complex environment in which managers operate. |
| • | This diversity and the significant interactions between the three areas pose a challenge to scholars, with current research both shedding light on particular aspects and on the interactions between the elements in applied settings as demonstrated by the contributions to this focused issue. |
12.
V. T. Troshchenko S. P. Sinyavskii S. S. Gorodetskii A. P. Gopkalo A. K. Rusanovskii 《Strength of Materials》1976,8(7):747-753
| 1. | The strength characteristics of the piston alloys under consideration, measured under conditions of isothermal and thermal fatigue approaching those encountered in actual practice, are considerably lower than the static strength characteristics. This indicates the importance of allowing for the factors in question when calculating the strength of interual-combustion-engine pistons. |
| 2. | Of the alloy studied in the present investigation, the lowest thermal-fatigue strength characteristics corresponding to approximately normal working conditions are those of aluminum alloy AL25. For temperature cycles of 55330°C the breaking stress on a base of 2·104 cycles of heat exchangers falls to 1 kgf/mm2, as compared with the isothermal fatigue limit (6.1 kgf/mm2) and the static tensile strength (12 kgf/mm2) at the same temperature. |
| 3. | Under conditions of combined loading, the fatigue life of alloy AL25 falls more rapidly than would follow from the linear hypothesis of damage summation, allowing for both mechanical and thermal fatigue. A vital factor in this case is the damage associated with interaction between the fatigue and thermal fatigue processes due to multiple-factor effects. |
| 4. | Criteria for the failure of piston materials under multiple-factor conditions call for urgent and more extensive investigation. |
13.
L. N. Molchanov 《Strength of Materials》1976,8(6):651-655
| 1. | In choosing a type of steel for conditions involving repeated impacts, it is essential to allow for the reliable working reserve of the structure or the constituent elements subjected to this loading. |
| 2. | The external form of the fractures enables us to determine the character of the breaking load. For static and single impact loading there are three zones of plastic yield situated on the three sides of the cross section (a part from the notch side). Under conditions of repeated impact loading, a fatigue crack necessarily arises, together with only two zones of plastic yield (on the vertical sides of the cross section). The area of the zones of plastic yield is much smaller than in the first two cases of loading and depends on the value of Aim. |
| 3. | By considering the form of the fracture surface we may judge the number of loading cycles. For a small number of cycles and a high impact energy, the final fracture zone occuples a large area, the cross section has an undulating structure, and the zones of plastic yield are considerable. For low impact energies the area occupied by the fatigue crack is greater, the final fracture less undulating, the zones of plastic yield smallish, the front of the fatigue crack directed with its convexity upward, and the relaxation lines more sparsely evident. The fractures confirm that for large impact energies the fracture bears a quasistatic character and for small energies, a fatigue character. |
| 4. | After 5·104 cycles and static completion of the fracture by bending all the samples had macro-or microfatigue cracks, so that the breaking load and the work required to complete the fracture by bending diminished. |
14.
This article presents a failure analysis of 37.5 mW gas turbine third stage buckets made of Udimet 500 superalloy. The buckets
experienced repetitive integral tip shroud fractures assisted by a low temperature (type II) hot corrosion. A detailed analysis
was carried out on elements thought to have influenced the failure process:
The most probable cause of the bucket damage was the combination of increased stresses due to corrosion-induced thinning of
the tip shroud and unfavorable microstructures in the tip shroud region. 相似文献
| a) | the stress increase from the loss of a load bearing cross-sectional area of the bucket tip shroud by the conversion of metal to the corrosion product (scale), |
| b) | influence of the tip shroud microstructure (e.g., a presence of equiaxed and columnar grains, their distribution and orientation), |
| c) | evidence of the transgranular initiation, and |
| d) | intergranular creep mechanism propagation. |
15.
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. |
16.
L. Vasil’ev D. Nikanpour A. Antukh K. Snelson L. Vasil’ev A. Lebru 《Journal of Engineering Physics and Thermophysics》1999,72(3):572-577
Conclusions The conclusions are summarized as follows:
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
| – | • 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. |
17.
Christos Pitelis 《Management International Review》2007,47(2):207-219
| – | We apply insights from Edith Penrose’s work to extant theory of the multinational enterprise (MNE) as enveloped by John Dunning’s Ownership, Location, Internalization (OLI) Paradigm. |
| – | We suggest that Penrose’s knowledge/learning-based approach has important implications on the nature of, and the interactions between, O, L and I, and it helps endogenize and integrate the three elements of Dunning’s triad in the context of a dynamic, and strategic perspective of the MNE. |
| – | More importantly, a learning-based perspective adds a cognitive dimension to the MNE and OLI. |
| – | This supports a forward looking, synchronic decision making view, that may lead to apparently sub-optimal decisions, taken in view of anticipated changes, along-side strategic behaviour, aiming to effect such change, once decisions have been reached. |
| – | A Penrosean-inspired knowledge/learning-based perspective helps render the OLI more dynamic, strategic and forward looking. |
18.
| • | Both scholars and practitioners have paid much attention to the impact of retaining top-performing knowledge workers on organizational effectiveness. |
| • | This study hypothesizes and analyzes how a bundle of high-commitment human resource practices (HCHRPs) influence affective organizational commitment, a strong predictor of employee turnover, of top performers versus ordinary employees. |
| • | This study suggests that HCHRPs may enable organizations to retain not only ordinary employees but also top performers through their positive impact on employees’ organizational commitment. |
| • | Using a sample of middle level managerial and R&D workers in 11 subsidiaries of a multinational conglomerate located in East Asia, this study showed that a bundle of high commitment human resource practices was positively related to the affective organizational commitment of top performers more than that of lower performers. |
19.
Laszlo Tihanyi Robert E. Hoskisson Richard A. Johnson William P. Wan 《Management International Review》2009,49(4):409-431
| • | 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. |
20.
A. Ya. Krasovskii I. V. Orynyak A. V. Naumov V. N. Krasiko 《Strength of Materials》1989,21(5):585-590
| 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. |