DESIGN METHODOLOGY AND CHARACTERISTICS ANALYSIS OF HIGH-ORDER MULTI-SEGMENT DEFORMED ECCENTRIC NON-CIRCULAR GEAR

A novel gear mechanism named high-order multi-segment deformed eccentric non-circular gear was proposed for achieving the unification of non-circular gears with typical-form pitch curve and non-circular gears with free-form pitch curve. The transmission mechanism of the high-order multi-segment deformed eccentric non-circular gear was analyzed, and the unified mathematical expression of eccentric gears was established. The non-circular gears with free-form pitch curve could be constructed based on the proposed high-order multi-segment deformed eccentric non-circular gear by changing the parameters. Moreover, the transmission characteristics were discussed, such as the transmission ratio relationship, convexity distinguished conditions, curvature radius of pitch curve. The visual design and simulation software and generation software of tooth profile for non-circular gears are compiled based on MATLAB, and was verified with the example. This novelty gear was applied to the drive mechanism of the metering pump. The mathematical model of non-circular gear-crank slider mechanism is established and the 3D model and virtual prototype experiment of the mechanism are accomplished. The application showed that the high-order multi-segment deformed eccentric non-circular gears were feasible in practice

Development of Sustainable Methodologies in Product Design, Manufacturing and Education

The influence of sustainability in product design and manufacturing processes can be considered from two different points of view: the design of sustainable products and the sustainable manufacturing of those products. Of course, a basic assumption for the aforementioned elements to be realized is the appropriate training and education for sustainability of the young designers and engineers. In this research, sustainability has been applied to many fields, including design, manufacturing and education acting as an umbrella which covers all the three elements and has as the main target to promote sustainability. In today’s world, in which a considerable number of contrasting signs reveal that our society is currently contributing to the planet’s collapse, a new kind of engineer is needed, an engineer who is fully aware of what is going on in society and who has the skills to deal with aspects of sustainability. According to the literature review on the state-of-the-art associated to the subject, in the current research were developed tools and methodologies for the promotion of sustainability aspects that are related to product design, manufacturing and education. Product DesignThe research work was based on a framework, which was built according to the direct communication between users and designers. There is a need for a cultural transformation, which can be focused on consumers and promote the needed behavioural change. Moreover there is a need for a cultural transformation on the role of designers and engineers to the product design process, with an aim to address sustainability as well as emerging priorities from societal to environmental challenges. New tools and methodologies were generated, in order to promote sustainability to the users/citizens bringing them inside to the product design process, giving them the opportunity to be a vital part of it. ManufacturingSustainable manufacturing faces new challenges for developing predictive models and optimization techniques in order to produce more products. The first part of the current is related to the drilling process and cutting tool technology. The creation of mathematical models focused on maximization of productivity and cost reduction by identifying crucial parameters and processes influencing manufacturing effectiveness. The second part of the current research is associated to the development of models used by CAD/ CAM that allow a rapid improvement and an efficient design and manufacture.EducationThe third aspect of the research is associated with the education related to sustainability. The engineering students should develop sustainability competences such as critical thinking, systemic thinking, obtaining values consistent with the sustainability paradigm, except of just taking a course on sustainability, focus on the technological role of sustainability. Focus on that the current research was based on sustainable characteristics such as a) remote control freeware applications, b) share of valuable resources, c) distance learning methodology and d) active participation of the students.<br /

Comparative study of flank cams manufactured by WEDM and willing processes

Cam-follower mechanisms are usually employed in different machines, like combustion engines, sewing machines, machine tools, etc. In the present paper, the option to manufacture cams utilizing wire electrical discharge machining (WEDM) has been considered. For this, surface roughness and shape error of cam profiles manufactured by the processes of milling and wire electrical discharge machining (WEDM) are presented. The methodology used covers dfferent stages: design, prototyping, manufacturing, and measurement of the cams. As a reference, a cam-follower mechanism from a motorcycle internal combustion engine has been used. A reverse engineering process has been performed to determine the geometrical parameters of the mechanism, which are used for the synthesis of the profile of the cam and its subsequent design. The manufacturing process of the cams has been assisted by CAD-CAM (Computer Assisted Drawing-Computer Assisted Manufacturing) software. Using fused filament fabrication (FFF), a physical prototype of the cam has been manufactured, in order to validate the goodness of the design. Finally, the roughness and shape parameters have been measured on the contour surface of the cams. The arithmetical mean roughness Ra value of the milled cam was 0.269 µm, below the requirement of 0.4 µm, and shape error was 18 µm, below 50 µm. Shape error of the WEDM cam of 48 µm meets the requirements for cams. However, the Ra value of 1.212 µm, exceeded the limit. For this reason, a finish operation is recommended in this case. Some advantages of WEDM cams over milled cams are that diferent conductive materials can be employed, more complex shapes can be obtained, and that, in rough operations, the amount of material to be removed in subsequent operations is considerably reduced.Postprint (published version

An extensive analysis of frequency and transient responses in S and C-shaped gears

Gears are crucial mechanical components and considerably used in consumer and industrial machinery. Gears can be grouped into five types namely spur, helical, rack and pinion, worm and bevel. Spur gear has been selected as a case model in this study mainly because it is one of the basic types of gear which can be easily constructed and fabricated. Spur gear tooth is designed using S and C-shaped transition curves. These curves are constructed using the G2 parametric Said-Ball cubic curve and clothoid templates. The result demonstrates that the C-shaped gear model which consists of the natural frequency of0.7408 Hz and low onaverage and standard deviation of 1.00E-3 mm and 8.072E-3 mm offers the most affordable displacement when compared with S-shaped and existing gear model

Comparison of Load Carrying Capacity of Three and Four Lobed Polygonal Shaft and Hub Connection for Constant Grinding Diameter

Polygonal shafts are a major competitor to spline and keyed shafts for power transmission due to features as self-centering, lack of stress concentration area, and ease of assembly and disassembly. Past studies on polygonal profiles have focused on a single profile and comparisons based on nominal sizes of three and four lobe profiles. This research explores the loading strength of the standardized three and four lobe polygonal shafts and hubs manufactured from the same stock size, subjected to pure torsional and torsional bending load from a spur gear of 20° pressure angle at various fits. In absence of analytical solution, Finite element method has been used after verifying the results experimentally, theoretically, and DIN standard. From the finite element analysis, the hub was found to experience greater stress than the shaft in all cases. The clearance fit was found to be the most critical connection and interference fit to be the most suitable for larger power transmission. The P4C connection had greater stress, especially in the hub, than the P3G connection. The difference between the P4C shaft and the P3G shaft was 4.05% in the interference fit and 60.6% in the clearance fit, suggesting P4C clearance fit to be less favorable for larger power transmission. Owing to its small normal axial stress, the P4C clearance fit has its use in low power transmission where sliding fit is a requirement. The reason for greater stress in P4C shaft and hub connection is due to the large pressure angle at the point of contact, which leads to a smaller contact area and greater contact pressure. The contact pressure was found to be triangular shaped in clearance and transition fit and with a large crest, followed by a trough and a small crest in interference fit for torsional bending load

Mechanistic Modeling of the Liquid Film Shape and Heat Transfer Coefficient in Annular-Regime Microchannel Flow Boiling

A methodology is proposed for predictive modeling of the liquid-gas interface shape and saturated flow boiling heat transfer coefficient in two-phase microchannel flows within the annular regime. The mechanistic model accounts for the effects of surface tension and interface curvature, gravity, and shear stress in determining the liquid film shape; one-dimensional conduction is assumed to occur across the variable-thickness film to calculate wall heat transfer coefficients locally along the channel length. Model performance is benchmarked against 251 experimentally measured heat transfer coefficient values taken from the literature for annular-regime flow boiling in microchannels of a rectangular crosssection. These data are successfully predicted with a mean absolute error of 21.7%, and 72.1% of the points lie within an error band of ±30%. The match to data is poorest at lower vapor qualities corresponding to the onset of the annular regime, for which the heat transfer coefficient is underpredicted; an experimental investigation is performed to better understand the disparity under these operating conditions. Liquid film shapes are measured during adiabatic annular flow through microchannels of square cross-section for a range of channel hydraulic diameters (160 mm, 510 mm, 1020 mm) and operating conditions, so as to control the void fraction and Weber number of the flow. Using air and water as the working gas and liquid, respectively, trends in film behavior are identified and compared against model predictions. The experimental findings reveal the non-negligible impact of capillary pumping on the interface morphology at the onset of the annular regime

Aeronautical engineering: A continuing bibliography with indexes (supplement 269)

This bibliography lists 539 reports, articles, and other documents introduced into the NASA scientific and technical information system in August, 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Aeronautical engineering: A continuing bibliography with indexes (supplement 271)

This bibliography lists 666 reports, articles, and other documents introduced into the NASA scientific and technical information system in October, 1991. Subject coverage includes design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics