Development of the Composition and Modes of Spraying Antifriction Coating Reinforced with Quasicrystals for the Manufacture of Sliding Bearings
Silchenko Olga Borisovna,
Siluyanova Marina Vladimirovna
Issue:
Volume 4, Issue 6, December 2019
Pages:
79-82
Received:
21 March 2019
Accepted:
26 June 2019
Published:
27 November 2019
Abstract: The paper presents the compositions of coatings from composite materials reinforced with quasicrystals. The composition and mode of application of cold gas-dynamic deposition of antifriction coating based on composite materials reinforced with quasicrystals for the manufacture of sliding bearings have been determined and determined. Quasicrystals of the Al-Cu-Fe system, metal composite coatings based on copper reinforced with quasicrystal line particles were used for research. In the course of the work, the compositions of quasicrystal-reinforced coatings were developed, the optimal composition and modes of applying the coating by cold gas-dynamic spraying were determined. According to the optimal mode, samples were made and their mechanical and tribological properties were investigated.
Abstract: The paper presents the compositions of coatings from composite materials reinforced with quasicrystals. The composition and mode of application of cold gas-dynamic deposition of antifriction coating based on composite materials reinforced with quasicrystals for the manufacture of sliding bearings have been determined and determined. Quasicrystals o...
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Predictions and Magnetic Characterization of M-type Hexaferrites Doped with Two Cations in the Fe3+ Site
Pedro Antonio Mariño-Castellanos,
Valery Alexevich Lapshinsky,
Carlos Pupo,
Arles Vega-García,
Eduardo Fernández-Cruz,
Braddy Ivan Jimenez-Morales
Issue:
Volume 4, Issue 6, December 2019
Pages:
83-90
Received:
29 September 2019
Accepted:
5 November 2019
Published:
2 December 2019
Abstract: A theoretical and experimental study of magnetic properties of M-type barium hexaferrites, doped with two cations in the Fe3+ sites: (Co3+, Al3+), (Co2+, Ti4+) and (Co2+, Sn4+) is reported. The theoretical predictions were made using the generalization of a model on the distribution of dopants in the crystallographic sites under study. This approach allows a better interpretation of the kinetics of obtaining the samples from the structural and magnetic characterization. In the reported model, the maximum limit refers to theoretical optimum parameters. With these concepts, were established quantitative relationships between dopant amount per crystallographic site and magnetic properties predicted of these systems. The comparison between the experimental values and the predicted magnitudes showed that, in general, the samples were obtained with parameters obtained close to the theoretical ones for traditional ceramic methods. Such an approach is rarely taken into account in the reported bibliography.
Abstract: A theoretical and experimental study of magnetic properties of M-type barium hexaferrites, doped with two cations in the Fe3+ sites: (Co3+, Al3+), (Co2+, Ti4+) and (Co2+, Sn4+) is reported. The theoretical predictions were made using the generalization of a model on the distribution of dopants in the crystallographic sites under study. This approac...
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Application of Strong Sealing High-performance Water-based Drilling Fluid in the Horizontal Well of the Missan Oilfield
Lei Zhiyong,
Chen Qiang,
Guo Tao,
Zhang Yong
Issue:
Volume 4, Issue 6, December 2019
Pages:
91-96
Received:
8 October 2019
Accepted:
15 November 2019
Published:
6 December 2019
Abstract: In the Missan oilfield, because of its reservoir being "easy leakage in the up and low zones, and wellbore being collapse in the middle zone" with narrow density window, borehole instability, lost circulation, borehole collapse, sticking and other downhole complicated conditions were easily induced. A strong sealing and high performance water-based drilling fluid was mainly used to solve the problems of borehole instabilities in mud shale and muddy limestone in the horizontal wells of Missan Oilfield, for solving the problem of sidewall instability, aphysical/chemical plugging was used for strengthening the plugging of drilling fluid, improving the loading ability in formation, reducing the risk of lost circulation. The principle of "activity" regulation, permeable pressure were used to improve the semi-permeable membrane characteristics of mudstone and shale, reduce the activity of drilling fluid, inhibit the expansion ability of mudstone hydration and expansion in formation, on the basis of the static drilling fluid, permeable pressure was added to the wellbore for further improvement of borehole stability. The system in use reflects the stable rheological properties, it can be very good for plugging micro fractures, greatly improving the load ability in formation, the delaying time of borehole stability, guaranteeing the borehole stability in drilling, it provides support for the smooth drilling of the first horizontal well and consequent horizontal well drilling in Missan Oilfield.
Abstract: In the Missan oilfield, because of its reservoir being "easy leakage in the up and low zones, and wellbore being collapse in the middle zone" with narrow density window, borehole instability, lost circulation, borehole collapse, sticking and other downhole complicated conditions were easily induced. A strong sealing and high performance water-based...
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Influence of Variation in Moisture Content to Soil Bearing Capacity in Nairobi Area and Its Environs
Hannah Nyambara Ngugi,
Stanley Shitote,
Nathaniel Ambassah,
Victoria Okumu,
John Thuo
Issue:
Volume 4, Issue 6, December 2019
Pages:
97-109
Received:
10 October 2019
Accepted:
12 November 2019
Published:
18 December 2019
Abstract: The increasing human population in cities and urban areas continues to raise the demand for housing and other infrastructure in developing nations. Stability of structures is critical for sustainable development to ensure longer useful life of structures and reduction in the rate at which natural resources for construction purposes are extracted from the environment. Foundation of buildings infrastructure plays a key role of transferring the loading from the structure to the soil underneath. In foundation design, the ultimate bearing capacity of soil under normal circumstances assumes that the water table is located well below the foundation. Variation in soil moisture content during construction and during the structure’s lifespan affect the soil bearing capacity. Information on the extent to which variation in soil moisture content affect the soil bearing capacity was lacking. This paper presents findings of a research that sought to establish the extent to which variation in soil moisture content affects the soil bearing capacity. Seven soil samples collected from Nairobi area and its environs were subjected to 30%, 50% and 75% moisture content variation. The soil bearing capacity was tested using Direct Shear method and Undrained Triaxial method in accordance to British Standard 1377 of 1990 Part 7 and Part 8 respectively. Test results determined that the insitu moisture content for the collected 7 soil samples from Nairobi area and its environs varied from 21.9% to 55.4% implying the diverse characteristics of soil samples and sites studied. Increasing the soil moisture content from 30% to 50% and to 75% all other factors held constant contributed to reduction in soil bearing capacity as illustrated by a linear equation y = -170.89x + 565.64 using direct shear method. y is the resultant soil bearing capacity (kN/mm2) while x is the soil moisture content in percentage. This shows that variation in soil moisture content contributes to a significant reduction in soil bearing capacity by a factor of -170.89x. To mitigate the negative effect of reduction in soil bearing capacity as a result of changes in soil moisture content, a factor of safety should be applied at design stage by adjusting the allowable soil bearing capacity to take cognisance of the contribution by changes in soil moisture content. This is critical to ensure that all structures are designed to withstand variation in moisture content at the foundation throughout their lifespan and avoid potential structural failure.
Abstract: The increasing human population in cities and urban areas continues to raise the demand for housing and other infrastructure in developing nations. Stability of structures is critical for sustainable development to ensure longer useful life of structures and reduction in the rate at which natural resources for construction purposes are extracted fr...
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