The diploma thesis deals with the topic of machinability of materials. The theoretical part describes the aspects according to which machinability can be evaluated. The material side of the thesis is focused on various types of difficult-to-machine materials. The cobalt alloy UmCo50 belongs to the group of difficult-to-machine materials and it is the subject of the experimental part. UmCo50 is an alloy for high temperature use. The primary aim of the thesis was to monitor the wear of the selected cutting tool when turning this alloy. Other aspects of the selected machining process were also monitored, such as force effects or the quality of the machined surface. Despite the fact that machinability of tested materials cannot be expressed in terms of the absolute value of a quantity, it is necessary to compare the various aspects of the machining processes by reference materials. However, certain conditions of this comparison must be met. Based on this, a comparison of tested and reference material was performed.

The thesis is focused on composite materials with a view to their classifi-cation, identification, usage, current trends in production and development and possibilities of effective machining. As a part of this thesis, there is an evaluation of experimentally measured values during technological testing of milling of a fibre reinforced composite with a polyester matrix reinforced by fiberglass. The technological testing was performed with a view to measure certain values, i.e. impact on machined material, working conditions for a tool and its abrasion equal to the values of components of cutting force. From the values obtained from the testing, a general analysis of cutting force when milling was created containing overall technical and economical evaluation.

This diploma thesis consists of two parts. The theoretical part describes sintered carbides, their properties and manufacturing tools. Some selected problems of milling and its physical nature is discussed also. It also deals with the types and methods of tool wear testing. The aim is to compare the experimental properties of monolithic end milling cutters (short four cutting edges, uncoated carbides) of various grain sizes in two basic ways of milling - down-feed method and up-feed method. The measured values are evaluated by analysis in time series of the cutting forces and power.

To make a simulation of cutting force during milling process with cilindrical cutter is the aim of this diploma thesis. Preliminary part is devoted to technology of milling, milling cutters and cutting materials. The next section is aimed at kinematics of the cutting process, a theoretical analysis of power proportion, the possibility of measurement of force actions. General information about the programming software, a theoretical simulation model, graphical environment of created application, are the other points of this diploma thesis. The work also includes evaluation of the experimentally measured values and compared with values obtained from the created application.

A general analysis of machining problems, analysis of cutting forces for turning, milling, drilling. Evaluation of experimentally measured values of surface structure and theoretical values of cutting forces in turning cylindrical parts. Economical processes for the comparable results of the final state of the surface.

The first part of work provides definition of basic parameters of threads, type of threads. Further work includes description of tools, material of tools and cutting forces. The final part of work deals with analysis course of cutting forces, analysis course wear and analysis surface structure of threads.

In the manufacturing industry, the mechanics of metal-cutting is well-understood and used to improve cutting processes. The mechanics of wood-cutting are still in its early stages and further research is required. Although there is a lack of knowledge regarding cutting mechanics for wood, today's cutting speeds in modern sawmills are as high as 100 m/s and the production rate and quality are high, to the cost of unnecessary wood-based waste. To be able to reduce waste it is necessary to understand the process of wood machining in detail. A Kistler 9129AA dynamometer was commissioned in a custom rotation machine and compared to an already existing sensor. It was shown that there were significant deviations between the measurement results of the evaluated sensor system and the Kistler 9129AA dynamometer. In this specific setup, the Kistler dynamometer was not able to deliver the same results as the existing sensor system. Therefore, the eligibility of the Kistler 9129AA dynamometer to measure cutting forces in wood could not be concluded.

Yes / This paper presents the development of a new chatter model using measured cutting forces instead of a mathematical model with empirical nature that describes them. The utilisation of measured cutting forces enables the prediction of real-time chatter conditions and stable machining. The chatter model is validated using fast Fourier transform (FFT) analyses for detection of chatter. The key contribution of the developed chatter model is that it can be incorporated in digital twins for process monitoring and control in order to achieve greater material removal rates and improved surface quality in future industrial applications involving machining processes. / Research Development Fund Publication Prize Award winner, Sep 2020.

L’introduction massive des alliages de titane pour les pièces de structures aéronautiques a soulevé de nouvelles problématiques d’usinage. Du fait que les matériaux réfractaires présentent de faibles propriétés thermiques leur mise en forme par usinage à sec est difficile. L’objectif industriel est d’améliorer la productivité de l’usinage des alliages de titane afin d’en réduire les coûts. Des travaux concernant la coupe du Ti6Al4V α+β, du Ti54M et du Ti6Al4V traité β ont été réalisés pour mettre en évidence les différences d’usinabilité entre ces trois matériaux. Ces travaux mettent en avant une forte influence du comportement orthotrope et de l’hétérogénéité de la microstructure lamellaire, ainsi que de la taille des grains du Ti6Al4V traité β sur la mise en forme par coupe. L’étude sur l’usure des outils par diffusion montre que le principal élément de diffusion est le titane et que par conséquent aucune différence n’est observée entre les trois matériaux. Pour confirmer que la diffusion est le mode d’usure principal, des essais de perçage instrumentés avec un système de mesure de température sans fil ont été effectués. Les températures à l’arrière de l’arête de coupe atteignent des températures supérieures à 500°C pour de faibles vitesses de coupe. A cette température le phénomène de diffusion est thermiquement activé et confirme les hypothèses évoquées précédemment. Enfin, pour avoir une compréhension des différences d’usinabilité mises en évidence lors des travaux expérimentaux, une recherche sur le comportement des matériaux (Johnson-Cook) et la mise en place d’une simulation numérique ont été réalisées. Les simulations réalisées à l’aide des lois de comportement identifiées précédemment modélisent précisément l’usinage du Ti6Al4V α+β et du Ti54M. L’hétérogénéité du Ti6Al4V traité β ne permet pas une bonne modélisation de la formation du copeau. Une modélisation polycristalline serait plus adaptée. / The massive introduction of titanium alloys onto the aeronautical structures parts has raised new problems in the machining process. Because of their low thermal properties (refractory materials), they are considered as difficult to cut material. The industrial aim is therefore to improve the productivity of the titanium alloy’s machining and to reduce their costs. Some research on Ti6Al4V α + β, Ti54M and β-treated Ti6Al4V cutting was carried out to point out machinability’s differences between these three materials. This work highlights a strong influence of the orthotropic behavior and the heterogeneity of the lamellar microstructure as well as the grain size of the β-treated Ti6Al4V on cutting. The study on the tool wear diffusion shows that the main diffusion element is titanium and therefore no difference is observed between those three materials. To check that diffusion is the main wear mode, instrumented drilling tests with a wireless temperature measurement device were performed. Temperatures behind the cutting edge reach temperatures above 500 °C for low cutting speeds. At this temperature the phenomenon of diffusion is thermally activated. Finally, in order to have an understanding of the machinability consistencies, a research on the materials’ behavior (Johnson-Cook) and the implementation of a numerical simulation were realized. The simulations carried out, using the previously identified behavior’s laws, model precisely the machining of the Ti6Al4V α+β and Ti54M. The heterogeneity of the β-treated Ti6Al4V does not allow a good modeling of the chip formation. Polycrystalline modeling would be more appropriate.

The surface integrity of a machined component that meets the demands of a specific application requirement is defined by several characteristics. The residual stress profile into the component is often considered as the critical characteristics as it carries a direct effect on the fatigue life of a machined component. A significant amount of effort has been dedicated by researchers to predict post process stress in a workpiece using analytical, experimental, and numerical modeling methods. Nonetheless, no methodology is available that can express the cutting process parameters and tool geometry parameters as functions of machined residual stress profile to allow process planning in achieving desired residual stress profile. This research seeks to fill that void by developing a novel approach to enable the extraction of cutting process and tool geometry parameters from a desired or required residual stress profile. More specifically, the model consists in determining the depth of cut, the tool edge radius and the cutting forces needed to obtain a prescribed residual stress profile for an orthogonal machining operation. The model is based on the inverse solution of a physics-based modeling approach of the orthogonal machining operation and the inverse solution of the residual stress prediction from Hertzian stresses. Experimental and modeling data are used to validate the developed model. The work constitutes a novel approach in engineering residual stress in a machined component.