This work focused on the surface expansion of the contact surface and its influence on the interface adhesion phenomena in wedge indentation of an aluminum specimen. Direct in-situ observations ...coupled with high-speed imaging and particle image velocimetry techniques were performed to characterize and quantify the surface expansion behavior at the contact surface. A series of experiments showed that the surface expansion distribution at the contact surface plays a pivotal role in determining the adhesion force. The quantitative relationship between the distributions of the surface expansion and adhesion force was discussed by using single-groove indenters.
•Studied the influence of surface expansion amount and ratio on adhesion force.•Observed the material surface expansion behavior by particle image velocimetry.•Examined the surface expansion distribution–adhesion force relationship.•The surface expansion and adhesion force distributions are highly consistent.
•A 3D scanner is a non-contact, non-destructive digital device that uses a light/laser source to accurately capture the shape of a physical object into computer-aided design (CAD) data.•It generates ...a point cloud or a set of data points in a coordinate system that accurately depicts a physical object's size and shape.•Using different methods, 3D scanning can collect information about an item, about an object's highness, breadth, and depth.•This paper discusses 3D Scanning, its processes, and its adoption for reverse engineering and industry 4.0 culture.•Finally, this paper covers essential features, traits, and applications of 3D scanning for the industry 4.0 environment.
A 3D scanner is a non-contact, non-destructive digital device that uses a light line/laser to accurately capture the shape of a physical object into Computer-Aided Design (CAD) data. It generates a point cloud or a set of data points in a coordinate system that accurately depicts a physical object's size and shape. The urge of human beings to build and recreate 3D objects is an essential requirement in the context of Industry 4.0. In Industry 4.0, 3D scanners are helpful for designing, assessing the minor features of any product, capturing freeform, and providing precise point clouds for complicated geometry and curved surfaces. Today advanced technologies are being introduced in industries, and 3D scanning technology is one of the latest emerging technologies. The situation has progressed significantly, and the ever-emerging world of 3D technology still disrupts a variety of sectors. This paper discusses 3D Scanning, its working process, and its adoption for reverse engineering and Industry 4.0 culture. Finally, this paper covers essential features, traits, and applications of 3D Scanning for Industry 4.0. Using different methods, 3D Scanning can collect information about an item, about an object's highness, breadth, and depth. 3D scanners are available on the market from high-end possibilities. They have different resolutions, and now they provide details of the scan to superimpose colour on an object, but the industry wants them to be developed for other quality attributes.
The objective of this study was to identify occupational exposure in the work process of nursing professionals, with radiopharmaceuticals marked with 68 Ga in a nuclear medicine service in ...municipality in the south of Brazil. Nursing professionals who work exclusively in the positron emission tomography/computed tomography participated in the study. The professionals were identified with the pseudonyms alpha and beta. Data collection took place through observation and prescribed documents in national and international regulatory standards, which were defined in four consecutive moments: observation of professionals during the procedure with the radionuclide 68 Ga, application of scripts related to the observed process, occupational dosimetry, and verification of the dose rate in the period from May to August 2019. Exposure increased by 20% with noted decreases in distance between the sources and radiosensitive structures (i.e., the eye lens and thyroid gland), increased exposure time, and improper use of available shielding. After evaluating the routine of nursing professionals and considering the high-energy parameters of 68 Ga, time, distance, shielding, and the high dose rate, it is suggested that the work process should be reevaluated and standardized, paying attention to critical points, as well as not having only the dosimetric reading as an evaluation parameter.
The rotor profiles of the claw vacuum pump mainly determine its working performance. The composition curves of the existing three-claw rotor profiles are complicated, and the compressed gas remaining ...in the carryover is recompressed, resulting in a remarkable increase of power consumption. For solving those problems, a sinusoidal curve was used to smoothly connect the addendum and dedendum arcs, and a novel three-claw claw rotor and its parametric equations were obtained. A novel discharge port was designed to avoid the secondary-compression of the gas in the carryover. The working process and the internal flow field of the new three-claw vacuum pump (TCVP) were revealed through numerical simulations. The mass flow rate at the proposed discharge port was also analyzed. Study results show that the proposed claw rotor has considerable advantages of simple profile, high internal volume ratio and small relative carryover. The designed discharge port realizes complete gas discharge without secondary-compression of the gas in the carryover. It is revealed that part of gas in the chamber formed by the separation of the compression chambers can flow back to the suction chamber in the compression process.
•Novel three-claw claw rotors for claw vacuum pump were proposed.•A novel discharge port for the new three-claw vacuum pump was designed.•Effects of geometrical parameters on the proposed vacuum pump were analyzed.•The working process and internal gas flows of the proposed pump were simulated.
Abstract
As the most widely used engine type in daily industrial production, diesel engine plays an important role in industrial and agricultural production. In recent years, with the rapid ...development of industrial technology, the working mode of diesel engine has also undergone tremendous changes, gradually changing to environment-friendly. In recent years, it has attracted the attention of researchers. This paper will introduce the generation principle of emissions from two aspects: 1. The working process of diesel engine. 2. Fuel proportion. Then, the main direction is to find solutions to reduce particulate emissions. One possible method is to use metal fuel additives to promote the regeneration of DPF (diesel particulate trap), while a possible solution is to use additives to reduce the activation energy. Another method is to improve the combustion of diesel engine through metal catalyst, which helps to reduce fuel consumption and inhibit the generation of harmful soot. This paper will focus on the analysis and search for suitable additive materials. The conclusion is that the additives containing organometallic materials are the most effective additives at present.
With the development of railway industry in China and the arrival of the computer age, there is a large talent gap in the direction of railway transportation in China. In order to increase the ...teaching quality of railway transportation major in higher vocational colleges and the skill level of students, it is very useful to apply the computer working process in the education of railway transportation major. This study discusses the teaching situation of traditional railway transportation mainly in higher vocational colleges, the necessity of computer working process in railway transportation, and the teaching mode and skill level of higher vocational railway transportation specialty based on computer working process. it provides a method for the new teaching mode of railway transportation.
Ductile fracture is a key factor to the workability of metallic materials undergoing hot deformation. The ductility of materials at elevated temperature is closely related to dynamic ...recrystallization (DRX). To systematically investigate the DRX based ductile fracture, hot tensile experiments, microscopic observations and modeling of fracture behavior were conducted for 316LN steel. Based on the experimental results, a monotonic increasing relationship between ductility and the percentage of DRX (Xdrx) was figured out and identified to be attributed to the DRX influenced void evolution. With the softening effect caused by DRX, the local stress concentration, which serves as the driving force of void nucleation, void growth as well as void coalescence of the material, is highly relieved and the behaviors of voids thus change. To describe the DRX based void evolution and predict ductile fracture in hot working process, an extended damage model was established by introducing Xdrx into the void-based GTN-Thomason ductile fracture model, which is termed as the extended GTN-Thomason model in this research. In modeling of the ductile fracture considering DRX, the void nucleation strain, which represents the strain with the highest nucleation rate, and the critical void size ratio, which articulates the onset of void coalescence were figured out to increase with Xdrx. In addition, the strain rate sensitivity and the temperature dependency are involved in representing the kinetics of DRX and the flow stress applied in the model. The developed model was then implemented into finite element (FE) simulation and its related parameters were calibrated via a hybrid experiment and simulation method. Finally, the specific validation experiments were designed and conducted and the predicted fractures agree well with experimental results. This research thus offers an in-depth understanding of the DRX based ductile fracture and further facilitates and supports the design of hot working process by avoiding ductile fracture occurrence.
•The temperature and strain rate dependent ductility is attributed to DRX.•DRX affects ductile fracture behavior via influencing void evolution.•The GTN-Thomason model was extended to hot working with the consideration of DRX.•Validation experiments were conducted to corroborate the extended model.
•A dynamic characteristics test rig based on the p-V diagrams on both sides of an oil-injection single screw compressor is established.•A new sensor arrangement method is proposed to synchronously ...collect the p-V diagrams of working chambers on both sides.•The working characteristics with variable oil flowrates, rotation speeds and back pressure are also obtained.•The change mechanism of micro parameters is investigated deeply based on the p-V diagram, such as pressurization effect during suction process.•An asymmetrical working process is found and investigated in detail, and the recommended response strategy is given to overcome its influence.
Single screw compressor is theoretically the optimal selection of compression machinery in mechanical vapor recompression (MVR), low temperature heat-pump system and sea water desalination fields because of simple structure, good force balance, big pressure ratio and wet compression. However, there is less thorough design criteria to guide design of key components in single screw compressor due to the lack of mechanism research. Therefore, it is necessary to investigate the working characteristics of the single screw compressor in detail. In this paper, a dynamic characteristics test rig based on the p-V diagrams on both sides of an oil-injection single screw compressor is established. According to the internal working characteristics based on performance experiment and p-V diagrams, the variations of key performance parameters under different rotation speeds, back pressure and oil injection flowrates are analyzed in detail. Meanwhile, the change mechanism of internal working characteristics are investigated deeply based on the p-V diagram, such as pressurization effect during suction process. In addition, an asymmetrical phenomenon of single screw compressor is found and analyzed in detail. The results provide the design and optimizing direction for single screw compressor.
The article presents the results of computer modeling and experimental research of the effect of butanol content in the fuel on the specific power, fuel-economic and environmental performance of 4ЧН ...11/12.5 (4ChN 11/12.5) diesel engine at various cycle fuel supplies and exhaust gas recirculation rates. The research has been carried out at crankshaft speeds of 1,000, 1,200, 1,400, 1,600, 1,800, 2,000 and 2,200 rpm with 25, 50, 75 and 100 % load. Fuels with butanol content of 5, 10, 15, 20, 25, and 30 % by volume have been investigated. The computer model of the diesel working process has been developed that takes into account the physical and chemical properties of the fuel, the characteristics of the fuel flow in the nozzle tip and the development of fuel sprays in the combustion chamber. Based on the results of computer modeling, dependencies have been determined that make it possible to assess the effect of the percentage of butanol in mixed fuel on the mean indicator pressure, specific fuel consumption, indicator efficiency, emissions of nitrogen oxides and dynamic indicators of the combustion process when choosing the composition of mixed butanol-containing fuel. Based on the conducted research, the following composition of mixed fuel has been selected: 85 % diesel fuel and 15 % butanol. Comparative tests of the diesel engine have been carried out when working on the external speed characteristic on diesel fuel and its mixture with 15 % butanol. It is obtained that when using mixed fuel, the character of the power change remains unchanged, the exhaust smoke decreases, nitrogen oxides emissions decrease at crankshaft speeds of 1,400, 1,600, 1,800, and 2,200 rpm, and the effective engine efficiency remains practically unchanged.
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