This master’s thesis is concerned with subject matter hard machining with defined geometry edge tools. Aim master’s thesis is analysis and parameters evaluation machined surface at hard machining. This master’s thesis contain a characteristic of hard materials, used technology for cutting operation, but also tools and cutting conditions suitable for hard machining. In the conclusion are parameters evaluation machined surface the workpiece.

The aim of this thesis is to describe the replacement of wire cutting laser cutting for cutting inserts made of hard material. Description of current situation in the company Vydona, tender and choice of laser and the need for post-laser workshop. The next section deals with the cutting of a particular sample. The last part of the technical economic assessment are calculated hourly rates of machines and the time and cost loads of different cutting inserts.

This Master's thesis deals with the issue of high-speed turning of the 100Cr6 material. The aim is to identify and experimentally validate an innovative production process for a particular component. The thesis includes theoretical basis of high-speed machining, analysis of the current state of the manufacturing process, innovation design and experimental verification. At the end of the thesis, parameters of the machined surfaces of specimens are evaluated.

Cost-effective machining of hardened steel (>60 HRC) components such as a large wind turbine bearing poses a significant challenge. This thesis investigates a new laser tempering based hybrid turning approach to machine hardened AISI 52100 steel parts more efficiently and cost effectively. The approach consists of a two step process involving laser tempering of the hardened workpiece surface followed by conventional machining at higher material removal rates using lower cost ceramic tooling to efficiently cut the laser tempered material. The specific objectives of this work are to: (a) study the characteristics of laser tempering of hyper-eutectoid 52100 hardened steel, (b) model the laser tempering process to determine the resulting hardness, and (c) conduct machining experiments to evaluate the performance of the laser tempering based hybrid turning process in terms of forces, tools wear and surface finish. First, the microstructure alterations and phase content in the surface and subsurface layers are analyzed using metallography and x-ray diffraction (XRD) respectively. Laser tempering produces distinct regions consisting of - a tempered white layer and a dark layer- in the heat affected subsurface region of the workpiece. The depth of the tempered region is dependent on the laser scanning conditions. Larger overlap of laser scans and smaller scan speeds produce a thicker tempered region. Furthermore, the tempered region is composed of ferrite and martensite and weak traces of retained austenite (~ 1 %). Second, a laser tempering model consisting of a three dimensional analytical model to predict the temperature field generated by laser scanning of 52100 hardened steel and a phase change based hardness model to predict the hardness of the tempered region are developed. The thermal model is used to evaluate the temperature field induced in the subsurface region due to the thermal cycles produced by the laser scanning step. The computed temperature histories are then fed to the phase change model to predict the surface and subsurface hardness. The laser tempering model is used to select the laser scanning conditions that yield the desired hardness reduction at the maximum depth. This model is verified through laser scanning experiments wherein the hardness changes are compared with model predictions. The model is shown to yield predictions that are within 20 % of the measured hardness of the tempered region. Using the laser scanning parameters determined from the laser tempering model, cutting experiments using Cubic Boron Nitride (CBN) tools and low cost alumina ceramic tools are conducted to compare the performance of laser tempering based hybrid turning with the conventional hard turning process. The machining experiments demonstrate the possibility of higher material removal rates, lower cutting forces, improved tool wear behavior, and consequently improved tool life in the laser tempering based process. In addition, the laser tempered based hybrid turning process produce is shown to yield lower peak-to-valley surface roughness height than the conventional hard turning process. Furthermore, it is found that lower cost ceramic tools can be used in place of CBN tools without compromising the material removal rate.

Orientador: Prof. Dr. Marco Antonio Bueno Filho / Dissertação (mestrado) - Universidade Federal do ABC, Programa De Pós-Graduação em Ensino, História, Filosofia das Ciências e Matemática, 2017. / Este estudo teve como objetivo identificar os conteúdos conceituais e os processos cognitivos gerais mobilizados durante a resolução de tarefas que envolvem a interface entre os campos de conceitos da Cinética Química e da Estrutura e Reatividade por estudantes de graduação sob a luz da Teoria dos Campos Conceituais. Em face disso, buscou-se responder: i. A interação entre estudantes e entre estudantes e professor, enquanto estratégia de ensino para a discussão de transformações enzimáticas, pode mobilizar e entrelaçar conceitualmente o Campo Conceitual Estrutural (CCE) ao do Campo da Cinética Química (CCC)? ii. Em caso afirmativo, quais invariantes operatórios são importantes na interface entre o Campo Conceitual Estrutural (CCE) e o Campo Conceitual da Cinética Química (CCC)? iii. Considerando que as resoluções de tarefas em Bioquímica podem envolver estes campos, qual é a dinâmica ou a contribuição destes campos nos esquemas de ação dos estudantes? Para responder essas questões, um minicurso extracurricular com foi oferecido com tarefas experimentais investigativas onde os estudantes participantes deveriam relacionar conhecimentos conceituais do Campo Estrutural ao Campo da Cinética Química. As explicações sobre estas tarefas foram registradas em vídeo. Estes registros foram analisados com o auxílio do software Transana® com vistas a categorização de acordo com Mullins (2008) e por Justi e Gilbert (1999a; 1999b). Os dados também foram submetidos à análise de correlação entre os conceitos e entre conceitos e as operações do pensamento utilizando-se o coeficiente de Jaccard/Tanimoto (TAN et al., 2006). Os resultados mostraram que os estudantes possuem dificuldade para estabelecer relações conceituais pertinentes e que estas relações quando existentes são caracterizadas pelo estabelecimento de relações de dependência, pela elaboração de hipóteses e pela percepção da simultaneidade de conceitos relativos aos Campos Conceituais da Cinética Química e da Estrutura e Reatividade como principais operações de pensamento. É importante salientar a constatação de esquemas individuais e coletivos, assim como se ressalta, também, a importância da mediação constante do professor no momento do aprendizado e no manejo dos conceitos durante a resolução de tarefas em sala de aula. / This study is devoted to identify the conceptual contents and general cognitive processes mobilized during the resolution of tasks that involve the interface between the fields of concepts of Chemical Kinetics and Structure and Reactivity by undergraduate students under the light of Conceptual Field Theory. In this context, it was sought to answer: i. Can the interplay among students and between students and teachers, as a teaching strategy for discussing enzymatic transformations, conceptually mobilize and interweave the Structural Conceptual Field (CCE) to that of the Field of Chemical Kinetics (CCC)?. ii. If so, which operative invariants are important at the interface between the Structural Conceptual Field (CCE) and the Conceptual Field of Chemical Kinetics (CCC)? iii. Considering that task resolutions in Biochemistry may involve these fields, what are the dynamics or contributions of these fields in the student action schemes? In order to explore these questions, an extracurricular mini-course containing experimental research tasks was offered in which the participating students should relate conceptual knowledge of the Structural Field to the Field of Chemical Kinetics. Explanations of these tasks were recorded on video. These records were analyzed with the help of Transana® software for categorization according to Mullins (2008) and by Justi and Gilbert (1999a; 1999b). The data were also submitted to the correlation analysis throughout concepts and also between concepts and thought operations using the Jaccard / Tanimoto coefficient (TAN et al., 2006). The results showed that students have difficulty in establishing pertinent conceptual relations and that the establishment of dependency relations characterizes these relations when they exist, by the elaboration of hypotheses and by the perception of the simultaneity of concepts related to Conceptual Fields of Chemical Kinetics and Structure and Reactivity as main operations of thought. It is important to emphasize the observation of individual and collective schemes, as well as emphasizing the importance of constant teacher arbitration in the moment of learning and in the concepts¿ handling during the resolution of tasks in the classroom.