Influence of the Manufacturing Process on the Local Properties of Bronze-Bonded Grinding Tools

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Abdelhamid Bouabid ◽  
Berend Denkena ◽  
Bernd Breidenstein ◽  
Alexander Krödel

Abstract The process behavior of a grinding tool is defined by the sum of interactions between the active abrasive grains and the workpiece. These interactions depend on the workpiece material, the manipulated parameters of the grinding process, and the tool properties. The tool properties are defined within the tool manufacturing process. In this context, the effects of the abrasive, the bond, and the sinter process on the global properties such as hardness, porosity, and fracture strength of the grinding layer are content of several research works. In contrast to this, the effects on the local properties, which define the grain/bond interface and therefore the process behavior at microscopic scale, have not yet been identified. This paper deals with identifying the influence of the sintering process on the local properties of the grinding layer. This is achieved by investigating the densification as well as the bond microstructure depending on the sintering parameters and on the specification of the initial mixture. As a use case, the bronze bond is considered. The results show that the input parameters have a significant impact on the homogeneity of the grinding layer. Due to the diffusion processes during sintering, there are densification gradients as well as tin concentration gradients in the grinding layer. The local tin concentration gradients imply different local mechanical and thermal properties. For this reason, each abrasive grain has unique interface properties.

2021 ◽  
Vol 5 (1) ◽  
pp. 4
Author(s):  
Maximilian Schrank ◽  
Jens Brimmers ◽  
Thomas Bergs

Continuous generating gear grinding with vitrified grinding worms is an established process for the hard finishing of gears for high-performance transmissions. Due to the increasing requirements for gears in terms of power density, the required surface roughness is continuously decreasing. In order to meet the required tooth flank roughness, common manufacturing processes are polish grinding with elastic bonded grinding tools and fine grinding with vitrified grinding tools. The process behavior and potential of the different bonds for producing super fine surfaces in generating gear grinding have not been sufficiently scientifically investigated yet. Therefore, the objective of this report is to evaluate these potentials. Part of the investigations are the generating gear grinding process with elastic bonded, as well as vitrified grinding worms with comparable grit sizes. The potential of the different tool specifications is empirically investigated independent of the grain size, focusing on the influence of the bond. One result of the investigations was that the tooth flank roughness could be reduced to nearly the same values with the polish and the fine grinding tool. Furthermore, a dependence of the roughness on the selected grinding parameters could not be determined. However, it was found out that the profile line after polish grinding is significantly dependent on the process strategy used.


2016 ◽  
Vol 106 (06) ◽  
pp. 407-411
Author(s):  
E. Prof. Uhlmann ◽  
J. Thalau

Der Schleifbelag hochharter CBN (kubisches Bornitrid)-Schleifscheiben in keramischer Bindung enthält neben der Primärkörnung in der Regel eine Sekundärkörnung, die aus einem konventionellen Schleifmittel besteht. Im 3-Stoffsystem, das dem Stand der Technik entspricht, wird die Sekundärkörnung als Bindungsbestandteil betrachtet, der vorrangig die Härte des Belages beeinflusst. Computertomografische Analysen und Untersuchungen von Schleifscheibentopografien zeigen jedoch, dass die Sekundärkörnung sowohl einen Einfluss auf das Gefüge als auch auf die Gestalt des Schneidenraums der Schleifscheibe hat. Technologische Untersuchungen zum Quer-Umfangs-Außen-Rundschleifen mit Schleifwerkzeugen, die sich in der Sekundärkorngröße unterscheiden, bestätigen diese Beobachtungen und zeigen einen Einfluss der Sekundärkörnung sowohl auf die Prozesskennwerte als auch auf das Arbeitsergebnis.   The grinding layer of vitrified-bonded superabrasive grinding wheels contains, in addition to its primary cBN-grains, in many cases secondary conventional abrasive grains. The ternary system considers secondary grains according to the state of the art as part of the bonding, which primarily affect the bond hardness. However, computer tomographic measurements and the analysis of grinding wheel topographies indicate that the secondary grains affect both the inner structure of the grinding wheel as well as the characteristic of the grinding wheel topography which directly influences the interaction of grinding tool and workpiece. Technological investigations on external cylindrical grinding across the circumference using grinding wheels with different secondary grain sizes confirm those observations and show a direct influence of the secondary grains on the grinding process behavior as well as on the grinding results.


Open Physics ◽  
2005 ◽  
Vol 3 (1) ◽  
Author(s):  
Adrian Cernescu ◽  
Tudor Luchian

AbstractPhysical consequences of ionic diffusion processes play a major role on the outcome of electrophysiology experiments due to both their contribution to the ionic transmembrane transport and phenomena taking place at the measuring instruments interface. As most of the time heterogenities in biological media with respect to ionic diffusion constants are disregarded, we intended to look upon the general case of ionic diffusion at the interface of two liquids on which gradients of these diffusion constants no longer can be neglected. We developed a theoretical model for the diffusion potential which emerges at an aqueous interface under gradients of concentration and diffusion constants. The experimental validation of our model was achieved through potential difference measurements of the diffusion potential between two solutions containing sodium chloride (NaCl) and glycerine solutions of various concentrations. Within the studied domain of the electrical charge mobility ratio, we noticed that experimental results are in agreement with the theoretically inferred diffusion potential values. This demonstrates that the resulting relationship for the diffusion potential inferred from our model could be applied for other cases, as well. When the ionic solutions contains an indefinite quantity of glycerine or an unknown substance able to modify diffusion constants of sodium and chloride, it was shown that through measurements of the diffusion potential one can infer the unknown concentration of glycerine and the modified ionic mobility ratio. This, in turn, builds up the foundation for a novel yet simple and efficient analitycal sensing device for quantitative determination in the field.


Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2231
Author(s):  
Ivan Beckman ◽  
Christine Lozano ◽  
Elton Freeman ◽  
Guillermo Riveros

The purpose of this review is to survey, categorize, and compare the mechanical and thermal characteristics of fibers in order to assist designers with the selection of fibers for inclusion as reinforcing materials in the additive manufacturing process. The vast “family of fibers” is described with a Venn diagram to highlight natural, synthetic, organic, ceramic, and mineral categories. This review explores the history and practical uses of particular fiber types and explains fiber production methods in general terms. The focus is on short-cut fibers including staple fibers, chopped strands, and whiskers added to polymeric matrix resins to influence the bulk properties of the resulting printed materials. This review discusses common measurements for specific strength and tenacity in the textile and construction industries, including denier and tex, and discusses the proposed “yuri” measurement unit. Individual fibers are selected from subcategories and compared in terms of their mechanical and thermal properties, i.e., density, tensile strength, tensile stiffness, flexural rigidity, moisture regain, decomposition temperature, thermal expansion, and thermal conductivity. This review concludes with an example of the successful 3D printing of a large boat at the University of Maine and describes considerations for the selection of specific individual fibers used in the additive manufacturing process.


2019 ◽  
Vol 5 (1) ◽  
pp. 489-491
Author(s):  
Olga Sahmel ◽  
Stefan Siewert ◽  
Klaus-Peter Schmitz ◽  
Daniela Arbeiter ◽  
Niels Grabow ◽  
...  

AbstractIn various biomedical applications extrusion represents a common manufacturing process for polymeric semi-finished products. Extrusion allows the processing of a wide range of biomaterials, as well as different cross-sectional geometries. The present work focuses on the development of an extrusion process for polymer micro-tubes used for medical devices manufacturing, e.g. microstents for minimally invasive glaucoma therapy. Semi-finished products were manufactured by means of extrusion and dip-coating. Morphology was investigated using biaxial laser measurement and scanning electron microscopy (SEM). For the analysis of mechanical and thermal properties of the specimens uniaxial tensile testing and differential scanning calorimetry (DSC) were performed. While dip-coated micro-tubes reveal a smooth and homogeneous surface, SEM micrographs of extruded micro-tubes exhibit some longitudinal grooves. Mechanical properties of extruded and dip-coated micro-tubes are comparable, so that the presented extrusion process can be regarded suitable for the manufacturing of polymer microtubes in a sub-millimeter scale. A future improvement of nozzle design will allow for a smooth surface of extruded semi-finished products.


2006 ◽  
Vol 45 ◽  
pp. 1751-1758 ◽  
Author(s):  
V.V. Vikulin

As required by the purpose and operating conditions of the articles, Si3N4-based ceramic materials must have a combination of properties ensuring their serviceability, while their manufacturing process must afford the manufacture of complex-shaped products. The paper deals with the technology of making complex-shaped articles from reaction-bonded, densified silicon nitride in the system Si3N4, Si3N4-BN, Si3N4-Al2TiO5, Si3N4–Si by thermoplastic slip casting of a fine high-purity silicon powder comprising additives or sintering aids with subsequent nitridation at temperatures up to 1500°C or additional sintering up to 1750-1800°C. In the process of making reaction-bonded silicon nitride, consideration is given to the exothermal effect of reaction, to the influence of additives on the properties of ceramics and the manufacturing process. Methods of oxidation protection of porous Si3N4-based ceramics and adaptation of these methods to protection of porous SiC- or SiC-C – based ceramics are discussed. Upon densification of reaction-bonded silicon nitride at temperatures up to 1750- 1800°C, consideration is also given to the effects of diffusion processes of the additives, used as sintering aids, on ceramics microstructure. The mechanisms of dissolution – recrystallization of α- and β-Si3N4 in the course of forming the self-reinforced ceramic structure are discussed. The peculiarities of making Si3N4-Si – based material having unusual properties including the mechanism of forming, oxidation resistance, electrical conductivity and high impact resistance are covered. The paper presents the results of testing of the ceramic components and units of gasturbine engines, bearings and attachments of the spacecraft Buran, and it also gives test data with reference to the ceramic parts tested at temperatures above 2000°C.


2016 ◽  
Vol 1136 ◽  
pp. 71-77
Author(s):  
Bahman Azarhoushang ◽  
Rolf Rinderknecht ◽  
Alireza Vesali ◽  
Juergen Struss

The loading of the grinding wheel and adhesion of the workpiece material to the cutting edges of the grinding tool are among the main reasons which limit the process efficiency when grinding ductile materials. The micro topography of the grinding tool changes drastically as a result of loading. Higher grinding forces and temperatures, poorer surface quality and process accuracy are the consequences of the adhesion of the workpiece material to the grinding tool surface. A novel and promising technique to reduce the possibility of loading and adhesion in the grinding process is the infiltrating of the grinding tool. This study describes the results of infiltration of vitrified bonded conventional grinding wheels with graphite in the surface grinding process. The effects of infiltration have been studied for the first time on various grinding wheels with different grain materials, grit sizes, porosity and hardness. Two different types of steel which are very popular in the automobile industry, 100Cr6 and 16MnCr5, were chosen as the workpiece material by the surface grinding experiments. The selected cutting parameters cover a wide range of the practical surface grinding processes which are utilized generally in the industry. It has been experimentally shown that the type of infiltration plays an important role in reducing the loading of the wheel. Better surface quality and longer dressing intervals are the main results of the infiltration of the grinding tools.


2015 ◽  
Vol 809-810 ◽  
pp. 81-86
Author(s):  
Alexander Mikhailov ◽  
Anatoly Baykov ◽  
Ilya Navka

Formation of the ground surface is the result of the interaction of the cutting elements of the diamond tool with the material being processed, so the nature of the working surface geometry of the grinding wheel (WSW) has principal value on processed surface quality. One of the main parameters that characterize the geometry of the WSW is the law of the grain distribution vertex in height. However, statistical models do not reflect the real picture of the tool interaction with the material being processed in the modelling process of grinding tool on the elastic ligament used for final operations. In the process of contact with the material being processed each diamond grain is moved with an adjacent block ligament, changing the position of the cutting vertex relative to both the midrange cords level and the other grains vertexes. As a result the nature of the grain vertexes distribution changes and the conditions of interaction with the material being processed change too. Studies have shown that the density distribution in height of diamond grains elastic grinding tool vertexes in a static state can be described by different distribution laws. For practical use in the calculation of the processed surface roughness and processing capacity is sufficient to approximate the distribution in height only the most protruding grains. In the area of contact with the processed material the distribution density of the grains elastic tool in height significantly differs from the static characteristics and is defined by the elasticity degree of the grinding tool ligament and machinability index of the workpiece material. The obtained results can serve as initial data for the calculation of the processed surface roughness.


Author(s):  
А.В. Сергеевичев

Среди факторов, влияющих на износ и затупление шлифовального инструмента, одну из основных ролей играет температура. От температуры зависят адгезионные и диффузионные процессы, происходящие при резании древесины, которые, в свою очередь, влияют на скорость и величину затупления шлифовальных шкурок. Вопросом определения температурного поля в зоне контакта шлифовального инструмента с обрабатываемым материалом занимались многие исследователи, которые использовали для решения поставленных задач метод источников теплоты. Сущность его состоит в том, что исследуемый процесс распространения теплоты заменяется эквивалентным суммированием тепловых процессов от элементарных точечных источников. Рассматривая шлифование как разновидность скоростного резания, можно считать, что совокупность очагов повышенной температуры зоны контакта шлифовальной ленты с деталью представляет собой единичный источник теплоты, который действует, непрерывно перемещаясь по поверхности детали с постоянной скоростью. Форма и размеры теплового источника характеризуются поверхностью контакта ленты и детали. Анализ нагрева и охлаждения шлифовальной ленты во время ее работы показывает, что на теплосодержание ленты большое влияние оказывает длина контакта ленты с древесиной, давление прижима, скорость движения ленты, ее длина, конструктивные особенности станка. В большинстве случаев шлифовальная лента работает в благоприятных условиях, т. е. успевает охладиться до температуры окружающей среды за время одного оборота. При работе изношенной шкуркой для поддержания производительности шлифования на заданном уровне необходимо прикладывать большее давление прижима, что приводит к увеличению теплообразования в зоне резания до такой степени, что лента не успевает охладиться за время обращения. Происходит резкое повышение температуры в зоне шлифования и, как следствие, прижог поверхности обрабатываемой детали. Among the factors influencing a wear and a blunting of the grinding tool, one of the main roles is played by temperature. The adhesion and diffusion processes occurring when cutting wood which, in turn, influence the speed and size of a blunting of abrasive papers depend on temperature. Many researchers who used a method of sources of warmth for the solution of objectives dealt with an issue of definition of a temperature profile in a zone of contact of the grinding tool with the processed material. Its substance consists that the studied process of distribution of warmth is replaced with the equivalent toting of thermal processes from the partial point sources. Considering grinding as a kind of high-speed cutting, it is possible to consider that set of the centers of elevated temperature of a zone of contact of an abrasive belt with a detail represents a simple source of warmth which works, continuously moving on a detail surface with constant speed. The form and the sizes of a thermal source are characterized by the surface of contact of a tape and a detail. The analysis of heating and cooling of an abrasive belt during its work shows that on heat content of a tape the great influence is exerted by length of contact of a tape with wood, the clip pressure, traveling speed of a tape, its length, design features of the machine. In most cases the abrasive belt works in the favorable conditions, that is manages to be cooled to environment temperature during one turn. During the work as a worn-out skin for maintaining of efficiency of grinding at the given level it is necessary to put the larger pressure of a clip that leads to increase in a heat generation in a cutting zone to such an extent that the tape does not manage to be cooled during the address. There is a sharp temperature increase in a grinding zone, and, as a result, burn of the surfaces of the processed detail.


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