Effect of Two-Stage Cooling on the Microstructure and Tribological Properties of Steel–Copper Bimetals

In this paper, the solid–liquid composite method is used to prepare the steel–copper bimetal sample through two-stage cooling process (forced air cooling and oil cooling). The relationship between the different microstructures and friction properties of the bimetal copper layer is clarified. The results show that: the friction and wear parameters are 250 N, the speed is 1500 r/min (3.86 m/s), the friction coefficient fluctuates in the range of 0.06–0.1, and the lowest point is 0.06 at 700 °C. The microstructure of the copper layer was α-Cu, δ, Cu3P, and Pb phases, and Pb was free between α-Cu dendrites. When the solidification temperature is 900 °C, the secondary dendrite of α-Cu develops. With the decrease temperature, the growth of primary and secondary dendrites gradually tends to balance at 700 °C. During the wear process, Pb forms a self-lubricating film uniformly distributed on the surface of α-Cu, and the Cu3P and δ phases are distributed in the wear mark to increase α-Cu wear resistance.

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Research on Tribological Properties and Viscoelasticity of EPDM Rubber in the Main Drive Sealing System of Shield Machine

Journal of Tribology ◽

10.1115/1.4051977 ◽

2021 ◽

pp. 1-9

Author(s):

Qi Sun ◽

Shijie Wang ◽

Xiaoren Lv

Keyword(s):

Carbon Black ◽

Tribological Properties ◽

Friction And Wear ◽

Adhesive Wear ◽

Carbon Black Content ◽

Stick Slip ◽

Wear Process ◽

New Compounds ◽

Shield Machine ◽

The Relationship

Abstract The tribological properties and wear mechanisms of EPDM with different carbon black contents under dry friction conditions are studied on an UMT Tribolab friction and wear tester. The variation of carbon black content in EPDM does not lead to the formation of new compounds. However, it significantly improves the shore hardness and tribological properties of EPDM. In addition, significant stick-slip phenomenon occurs during the wear process of EPDM with different carbon black content. During the wear process of EPDM, there are both adhesive wear and abrasive wear, and adhesive wear is the main wear form. Therefore, the results reveal the relationship between carbon black content and tribological properties of EPDM, which can contribute to improve the tribological properties of EPDM.

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Correlation between Defects and Technical Wear of Materials Used in Traditional Construction

Materials ◽

10.3390/ma14102482 ◽

2021 ◽

Vol 14 (10) ◽

pp. 2482

Author(s):

Jarosław Konior ◽

Mariusz Rejment

Keyword(s):

Residential Buildings ◽

Descriptive Analysis ◽

Technical Condition ◽

Water Penetration ◽

Major Drawback ◽

Wear Process ◽

Materials Used ◽

Traditional Construction ◽

The Relationship ◽

Measurable Property

The degree of technical wear of old buildings, which are made of basic materials (cement, concrete, steel, timber, plaster, brick) using traditional technology, is expressed by the size and intensity of damage to their elements. The topic of the research concerns old residential buildings from the turn of the 19th and 20th centuries, which are located in the downtown district of Wroclaw, Poland. The descriptive analysis and the analysis of the definitions of defects that occur in the elements of residential buildings, which were performed as random analyzes, do not allow defects to be considered as measurable variables at a level of visual investigation. The major drawback of the method that is used by experts when assessing the technical condition of civil engineering buildings is that it does not numerically express the magnitude (strength) of the defects. Therefore, an attempt was made to numerically express the relationship (if such a relationship exists) between the occurred defects of buildings and the extent of their technical wear process. When calculating the strength of this relationship, the method of determining the point biserial correlation coefficient for the measurable property and the dichotomous property was used. It was found that the direction of the relation is right-hand for all the tested building elements, but the strength of the correlation between the detected defects and technical wear shows a considerable span and depends on the conditions of the apartment house’s maintenance. As a rule, damage caused by water penetration and moisture penetration always shows correlations of at least moderate strength.

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Air circulation in a gastrointestinal light source box and endoscope in the era of SARS-CoV-2 and airborne transmission of microorganisms

Endoscopy International Open ◽

10.1055/a-1336-3280 ◽

2021 ◽

Vol 09 (03) ◽

pp. E482-E486

Author(s):

Stanislas Chaussade ◽

Einas Abou Ali ◽

Rachel Hallit ◽

Arthur Belle ◽

Maximilien Barret ◽

...

Keyword(s):

Light Source ◽

Cooling System ◽

Air Cooling ◽

Airborne Transmission ◽

Plastic Tube ◽

Care Workers ◽

Air Cooling System ◽

Forced Air ◽

Air Circulation ◽

Closed Environment

Abstract Background and study aims The role that air circulation through a gastrointestinal endoscopy system plays in airborne transmission of microorganisms has never been investigated. The aim of this study was to explore the potential risk of transmission and potential improvements in the system. Methods We investigated and described air circulation into gastrointestinal endoscopes from Fujifilm, Olympus, and Pentax. Results The light source box contains a lamp, either Xenon or LED. The temperature of the light is high and is regulated by a forced-air cooling system to maintain a stable temperature in the middle of the box. The air used by the forced-air cooling system is sucked from the closed environment of the patient through an aeration port, located close to the light source and evacuated out of the box by one or two ventilators. No filter exists to avoid dispersion of particles outside the processor box. The light source box also contains an insufflation air pump. The air is sucked from the light source box through one or two holes in the air pump and pushed from the air pump into the air pipe of the endoscope through a plastic tube. Because the air pump does not have a dedicated HEPA filter, transmission of microorganisms cannot be excluded. Conclusions Changes are necessary to prevent airborne transmission. Exclusive use of an external CO2 pump and wrapping the endoscope platform with a plastic film will limit scatter of microorganisms. In the era of pandemic virus with airborne transmission, improvements in gastrointestinal ventilation systems are necessary to avoid contamination of patients and health care workers.

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Influence of Inter‐layer Forced Air Cooling on Microstructure and Mechanical Properties of Wire Arc Additively Manufactured 304L Austenitic Stainless Steel

steel research international ◽

10.1002/srin.202100175 ◽

2021 ◽

Author(s):

Lavinia Tonelli ◽

Ramona Sola ◽

Vittoria Laghi ◽

Michele Palermo ◽

Tomaso Trombetti ◽

...

Keyword(s):

Mechanical Properties ◽

Stainless Steel ◽

Austenitic Stainless Steel ◽

Air Cooling ◽

Microstructure And Mechanical Properties ◽

Forced Air

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Two-Stage Evaporative Inlet Air Gas Turbine Cooling

Energies ◽

10.3390/en14051382 ◽

2021 ◽

Vol 14 (5) ◽

pp. 1382

Author(s):

Obida Zeitoun

Keyword(s):

Gas Turbine ◽

Gas Turbines ◽

Evaporative Cooling ◽

Air Cooling ◽

Vapor Compression ◽

Two Stage ◽

Turbine Cooling ◽

Riyadh City ◽

Vapor Compression Refrigeration ◽

Gas Turbine Cooling

Gas turbine inlet air-cooling (TIAC) is an established technology for augmenting gas turbine output and efficiency, especially in hot regions. TIAC using evaporative cooling is suitable for hot, dry regions; however, the cooling is limited by the ambient wet-bulb temperature. This study investigates two-stage evaporative TIAC under the harsh weather of Riyadh city. The two-stage evaporative TIAC system consists of indirect and direct evaporative stages. In the indirect stage, air is precooled using water cooled in a cooling tower. In the direct stage, adiabatic saturation cools the air. This investigation was conducted for the GE 7001EA gas turbine model. Thermoflex software was used to simulate the GE 7001EA gas turbine using different TIAC systems including evaporative, two-stage evaporative, hybrid absorption refrigeration evaporative and hybrid vapor-compression refrigeration evaporative cooling systems. Comparisons of different performance parameters of gas turbines were conducted. The added annual profit and payback period were estimated for different TIAC systems.

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