Micro cutting is becoming increasingly important since miniature and micro components/products have become more and more demanded in precision engineering applications and consumer goods in a daily life. Meanwhile, it has not been thoroughly investigated yet. Scientific understanding of the fundamentals in micro cutting mechanics and physics is vital for micro manufacturing of micro or miniature components and products. Consequently, the scientific investigation on micro cutting mechanics is critically needed, particularly on its key fundamental aspects on which a systematic approach and key enabling technologies are developed for micro manufacturing. Therefore, three key fundamental aspects of micro cutting mechanics have been identified for this PhD project and a comprehensive systematic research has been performed through both theoretical and experiment-based investigations. The three aspects of micro cutting mechanics mainly include dynamic stiffness investigation, innovative micro cutting force modelling, and the study on micro cutting heat, temperature and their partitioned distribution. All experiment-based investigations are undertaken on a diamond turning machine test rig supported with a fast tool servo (FTS) using different reconfigured experimental setups. The finite element (FE)-based analysis is conducted to further support the in-depth analysis on the micro cutting phenomena especially the modelling and simulation of micro cutting force and temperature. Accordingly, both micro cutting force modelling and micro cutting temperature are investigated using modelling and simulation supported by well-designed experimental cutting trials and validations. The investigation on dynamic stiffness in the micro cutting system is focused on its effects on the micro cutting process and its control strategies. The burrs formation and machining accuracy are explored in relation with control of the dynamic stiffness. Furthermore, the control algorithm for dynamic stiffness is developed accordingly in order to minimise burrs formation and stabilize the micro cutting accuracy. The micro cutting force modelling is performed based on specific cutting force, i.e. modelling the cutting force at the unit cutting length or area as coined as the amplitude aspect of the proposed cutting force modelling. The cutting force against a dynamically varied cutting time interval is proposed as the spatial aspect of the cutting force formulation. The amplitude aspect can provide the insight into the micro cutting phenomena particularly in relation with the chip formation and size-effects. The spatial aspect, using a on the wavelet transform (WT) technique and standard deviation analysis can render the dynamic behaviour of the micro cutting force, particularly representing the dynamic effects of the cutting process and its correlation with tool wear. The micro cutting temperature is investigated to formulate the scientific understanding of cutting temperature, heat and their partitioned distribution particularly at the tool-workpiece-chip interface zone in ultraprecision and micro cutting using a diamond cutting tool. The contribution to knowledge at this aspect is to represent the partitioned cutting heat in the micro cutting process and their different behaviours compared to the conventional metal cutting. The scientific approach to modelling micro cutting application (MMCA), i.e. based on modelling-simulation combined with experimental validation, is further evaluated and validated to illustrate the overall benefits of this research investigation through micro cutting of single crystal silicon (for ultraprecision machining of large-sized infrared devices). This approach is established in light of combining all the three aspects of the above investigation on micro cutting mechanics. The research results show the approach can lead to industrial scale advantages for ultraprecision and micro cutting but driven by the scientific understanding of micro manufacturing technology. The systematic investigation on dynamic stiffness control, micro cutting force modelling, micro cutting heat and temperature and their integrated approach can contribute well to the future micro cutting applications.

At micrometer length scales of material removal, size effect is observed in mechanical micro-cutting where the energy per unit volume i.e. specific cutting energy increases nonlinearly as the uncut chip thickness is reduced from several hundred microns to a few microns (or less). There is no consensus in the literature on the cutting mechanism that causes this size effect. Noticeable discrepancy is also observed in the surface roughness produced at small feeds in micro-turning between the theoretical and the measured roughness. To date, there has been little effort made to develop a detailed process model for micro-cutting to accurately predict the size effect in specific cutting energy, and to develop a fundamental understanding of surface generation at the low feeds typical of micro-cutting processes. The main objective of this thesis is therefore to develop a predictive process model of micro-cutting of ductile metals that is capable of accurately predicting the size effect in specific cutting energy based on strain gradient based material strengthening considerations. In addition, this thesis attempts to explain the discrepancy between the theoretical and measured surface roughness at small feeds in micro-turning via a model that accounts for the size effect due to material strengthening. A coupled thermo-mechanical finite element model formulation incorporating strain gradient plasticity is developed to simulate orthogonal micro-cutting process. The thermo-mechanical model is experimentally validated in orthogonal micro-cutting of a strain rate insensitive aluminum alloy Al5083-H116. The model is then used to analyze the contributions of two major material strengthening factors to the size effect in specific cutting energy: strain gradient and temperature. The effects of cutting edge radius on the specific cutting energy and its role relative to the material length scale arising from strain gradient plasticity are also examined. A surface roughness model for micro-turning that incorporates the effects of kinematic roughness, cutting edge roughness and surface roughening due to plastic side flow is developed and shown to explain the observed discrepancy between the theoretical and measured surface roughness in micro-cutting. In addition, the model is found to accurately capture the increase in surface roughness at very low feeds.

The scaling of specific cutting energy is studied when micro-cutting ductile metals. A unified framework for understanding the scaling in specific cutting energy is first presented by viewing the cutting force as a combination of constant, increasing, and decreasing force components, the independent variable being the uncut chip thickness. Then, an attempt is made to isolate the constant force component by performing high rake angle orthogonal cutting experiments on OFHC Copper. The data shows a trend towards a constant cutting force component as the rake angle is increased. In order to understand the source of this constant force component the chip-root is investigated. By quickly stopping the spindle at low cutting speeds, the chip is frozen and the chip-workpiece interface is examined in a scanning electron microscope. Evidence of ductile tearing ahead of the cutting tool is seen at low and high rake angles. At higher cutting speeds a quick-stop device is used to obtain chip-roots. These experiments also clearly indicate evidence of ductile fracture ahead of the cutting tool in both OFHC Copper and Al-2024 T3. To model the cutting process with ductile fracture leading to material separation the finite element method is used. The model is implemented in a commercial finite element software using the explicit formulation. Material separation is modeled via element failure. The model is then validated using the measured cutting and thrust forces and used to study the energy consumed in cutting. As the thickness of layer removed is reduced the energy consumed in material separation becomes important. Simulations also show that the stress state ahead of the tool is favorable for ductile fracture to occur. Ductile fracture in three locations in an interface zone at the chip root is seen while cutting with edge radius tool. A hypothesis is advanced wherein an element gets wrapped around the tool edge and is stretched in two directions leading to fracture. The numerical model is then used to study the difference in stress state and energy consumption between a sharp tool and a tool with a non-zero edge radius.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Seedling production of canjerana has been limited by difficulty in germination, caused by recalcitrant behavior of their seeds. The objective of this study was to develop micropropagation to auxiliate preserving and multiplication of superior genotypes, to study the plantlet production by micro-cutting and mini-cutting, and to evaluate the genetic diversity of canjerana. In micropropagation, seeds of canjerana were disinfected with 0, 2.5, 5.0, 7.5 and 10% of NaOCl solution to produce aseptic seedlings, which were cultivated on MS and WPM media. Nodal segments were treated with 0 and 2.5 μM of BAP, KIN and TDZ and with 0, 1, 3, 6, 9 and 12 μM of BAP, which were cultivated on WPM media. Micro-cuttings, were cultivated on MS and WPM media with either 0 or 5.0 μM of IBA and NAA. The rooted micro-cuttings were acclimatizated in a humid chamber in a greenhouse. The highest percentage of decontaminated seeds was produced using a solution of 7.5% of NaOCl and immersion times of 10, 20 and 30 minutes. The same concentrations of BAP, KIN and TDZ and increasing concentrations of BAP in the WPM media did not increase shoot number and length. Neither the base medium nor the auxin had a significant effect on the survival of micro-cuttings after 60 days of cultivation, but the addition of 5.0 μM of NAA did increase the percentage of rooting and survival during the acclimatization. Both nodal segments and microstumps of canjerana have a low rate of multiplication. Shoots produced from microstumps may be rooted in WPM or MS medium added with 5.0 μM of NAA. These complete plantlets can be mantained in vitro or acclimatized as a source of stock plants for the microclonal hedge. For production of canjerana plantlets by mini-cutting, different concentrations of indolbutyric acid (IBA) and substrate combinations were evaluated. Mini-cuttings were treated with 2000 mg L-1 of IBA and planted in commercial substrate; coarse sand; carbonized rice husks; and a combination of the three. Apical and nodal minicuttings were treated with 0, 1000, 2000 and 3000 mg L-1 of IBA and planted in a combination of commercial substrate, coarse sand and carbonized rice husks. The productivity of microstumps and mini-cutting rooting were evaluated in three clones of canjerana. The combination of commercial substrate, coarse sand and carbonized rice husks maximized mini-cuttings rooting. Nodal mini-cuttings had higher rooting capability than apical ones. The application of 3000 mg L-1 of IBA improved rooting differentiation and growth of canjerana mini-cuttings. Canjerana clones differ in rooting capability and survival rates. The genetic diversity of canjerana, within and among progenies of three stock plants, was assessed with previously defined species-specific SSR markers. The allele frequency was calculated for each band and the heterozygosity and the polymorphic information content were calculated for each SSR pair of primers, progeny and for the combination of the 32 canjerana genotypes. The results showed high level of genetic diversity, both within and among progenies, making possible that genotypes from different stock plants grouped together. Based upon these results, high level of genetic diversity can be maintained in clones from progenies of selected stock plants. / A produção seminal de mudas de canjerana tem sido limitada pela dificuldade de germinação, ocasionada pelo comportamento recalcitrante das sementes. O objetivo deste trabalho foi desenvolver a micropropagação para auxiliar a conservação e multiplicação de genótipos superiores, estudar a microestaquia e miniestaquia para a produção massal de mudas, e avaliar a diversidade genética da canjerana. Na micropropagação, sementes de canjerana foram desinfetadas com 0; 2,5; 5,0; 7,5 e 10,0% de hipoclorito de sódio para a produção de plantas assépticas e cultivadas em meios MS e WPM. Segmentos nodais das plântulas foram inoculados em meio WPM acrescido de 0 ou 2,5 μM de BAP, KIN ou TDZ, bem como acrescido de 0; 1; 3; 6; 9 e 12 μM de BAP. Microestacas foram cultivados nos meios MS e WPM acrescido de 0 ou 5,0 μM de AIB e ANA. As microestacas enraizadas foram aclimatizadas em câmara úmida e em casa de vegetação. O maior percentual de sementes descontaminadas foi produzido usando uma solução de 7,5% de NaOCl por 10, 20 e 30 minutos. Tanto BAP, KIN e TDZ em iguais concentrações quanto o aumento das concentrações de BAP no meio WPM não aumentaram o número e nem comprimento das brotações. O meio de cultura e a auxina não afetaram a sobrevivência de microestacas, mas a adição de 5,0 μM de ANA aumentou a porcentagem de enraizamento e sobrevivência durante a aclimatização. Segmentos nodais e microcepas tiveram baixa taxa de multiplicação. Microestacas enraizaram em meio WPM ou MS acrescido de 5,0 μM de ANA. As mudas produzidas podem ser mantidas in vitro ou aclimatizadas para serem utilizadas como plantas matrizes do microjardim clonal. Para a produção de mudas de canjerana por miniestaquia foram avaliadas as concentrações de AIB e diferentes substratos. Miniestacas foram tratadas com 2000 mg L-1 de AIB e plantadas em substrato comercial; areia grossa; casca de arroz carbonizada; e a combinação em iguais proporções de substrado comercial, areia grossa e casca de arroz carbonizada. Miniestacas apicais e nodais foram tratados com 0; 1000; 2000 e 3000 mg L-1 de AIB e plantadas em uma combinação de substrato comercial, areia grossa e casca de arroz carbonizada. Além disso, a produtividade de minicepas e o enraizamento de miniestacas foram avaliados em três clones de canjerana. A combinação de substrato comercial, areia grossa e casca de arroz carbonizada maximizaram o enraizamento das miniestacas. Miniestacas nodais tiveram maior capacidade de enraizamento do que as apicais. A aplicação de 3000 mg L-1 de AIB aumentou o enraizamento e o crescimento de miniestacas de canjerana. Clones de canjerana diferem na porcentagem de enraizamento e na sobrevivência das miniestacas. A diversidade genética entre e dentro de progênies de três matrizes de canjerana foi avaliada por microsatélites. A frequência alélica foi calculada para cada banda e a heterozigose e o conteúdo de informação polimórfica foram obtidos para cada par de primers, cada progênie e para a combinação dos 32 genótipos de canjerana. Os resultados indicam a existência de alta variabilidade genética, tanto entre quanto dentro das progênies avaliadas, possibilitando a formação de grupos com genótipos oriundos de diferentes progênies. Assim, alta variabilidade genética pode ser mantida a partir de clones de progênies de matrizes selecionadas.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The aim of this study was to evaluate the in vitro productivity of micro-stumps, in vitro and ex vitro rooting and acclimatization of micropropagated plantlets, and to assess the genetic diversity of Apuleia leiocarpa (Vogel) J. F. Macbride (apuleia) with RAPD markers. Micro-stumps originated from drastic pruning of aseptic seedlings were grown in WPM culture medium supplemented with 0; 2.2; 4.4; 6.6 and 8.8 μM of 6-benzylaminopurine (BAP) and sub-cultured in WPM medium without cytokinin. Apuleia micro-stumps were also grown in WPM, MS or ½ MS, with or without 1.5 g L-1 of activated charcoal. Three shoot collections were done at 30, 60 and 90 days of cultivation. Nodal segments and micro-cuttings were maintained in WPM culture medium with 0; 4.9; 9.8; 14.7 and 19.6 μM of indole butyric acid (IBA). For acclimatization, rotted nodal segments and micro-cuttings were planted in equal proportions of commercial substrate + vermiculite + coarse sand, and commercial substrate + vermiculite. For ex vitro rooting, nodal segments and micro-cuttings were treated or not with 4920 μM of IBA for 10 seconds and cultivated in equal proportions of commercial substrate + vermiculite + coarse sand, commercial substrate + vermiculite, and commercial substrate + coarse sand. For genetic analysis, DNA was extracted from leaf samples of 88 plants of apuleia. Eighteen RAPD primers were tested. The amplified fragments were separated in agarose gel of 1.2% (v/v), containing 3 μL of ethidium bromide. The fragments were marked as absence or presence, generating a binary matrix. Total polymorphism and the relative contribution of each primer for the polymorphism were calculated. The polymorphism information content (PIC) was calculated for each fragment and primer. Cluster analysis was based upon Jaccard similarity and UPGMA method. The conservation of the apuleia micro-stumps in WPM or ½ MS media supplemented with 8.8 μM of BAP and sub-cultured in culture medium without citokynin increases number and length of shoots. Maintaining micro-stumps in culture medium supplemented with activated charcoal increases micro-cuttings production, but in its absence results in callus formation and indirect organogenesis of shoots. Nodal segments were more competent than micro-cuttings for rooting in culture medium without IBA. Substrate composition does not affect survival and growth during acclimatization of in vitro produced plantlets. Nodal segments treated with 4920 μM of IBA and cultivated in commercial substrate + vermiculite + coarse sand show the best responses for ex vitro rooting. Both in vitro conservation of apuleia micro-stumps and ex vitro rooting are promising strategies for plantlet production. The RAPD is a feasible technique for genetic analysis, and it identifies high genetic variability in apuleia. / Os objetivos deste trabalho foram avaliar a produtividade de microcepas mantidas in vitro, o enraizamento e a aclimatização de plantas micropropagadas, assim como avaliar a diversidade genética em Apuleia leiocarpa (Vogel) J. F. Macbride (grápia) com uso de marcadores RAPD. Microcepas oriundas da poda drástica de plantas assépticas foram cultivadas em meio de cultura WPM acrescido de 0, 2,2, 4,4, 6,6 e 8,8 μM de 6-benzilaminopurina (BAP) e subcultivadas em meio de cultura WPM sem citocinina. Microcepas também foram cultivadas em meio de cultura WPM, MS ou ½ MS, acrescido ou não de 1,5 g L-1 de carvão ativado e submetidas a três coletas de brotos aos 30, 60 e 90 dias de cultivo. No enraizamento in vitro, segmentos nodais e microestacas foram mantidos em meio de cultura WPM com 0, 4,9, 9,8, 14,7 e 19,6 μM de ácido indolbutírico (AIB). Na aclimatização das plantas foram testadas as composições de substrato comercial + vermiculita + areia grossa e substrato comercial + vermiculita, em iguais proporções. Para o enraizamento ex vitro, segmentos nodais e microestacas foram tratados ou não com 4920 μM de AIB por 10 segundos e cultivados em iguais proporções de substrato comercial + vermiculita + areia grossa, substrato comercial + vermiculita e substrato comercial + areia grossa. Para as análises RAPD, o DNA foi extraído de amostras foliares de 88 plantas. Foram avaliados 18 iniciadores, sendo a visualização dos fragmentos realizada em gel de agarose preparado a 1,2% (p/v), contendo 3 μL de brometo de etídio e submetido a eletroforese. Os fragmentos foram pontuados com ausência ou presença gerando uma matriz binária. Foi calculada a contribuição relativa de cada iniciador para o polimorfismo bem como o polimorfismo total. Também foi calculado o conteúdo de informação para o polimorfismo (PIC) para cada fragmento e por iniciador. A análise de agrupamento foi realizada com base na similaridade de Jaccard e no método UPGMA. A manutenção das microcepas de grápia em meio de cultura WPM ou ½ MS suplementado com 8,8 μM de BAP, seguido do subcultivo em meio de cultura sem citocinina aumenta o número e comprimento das brotações. O cultivo de microcepas em meio de cultura com carvão ativado aumenta a produção de microestacas por microcepas, enquanto a ausência de carvão ativado favorece a formação de calos e brotos por organogênese indireta. Quanto ao enraizamento in vitro, os segmentos nodais apresentaram maior resposta do que microestacas, sendo necessária a suplementação do meio de cultura com AIB. A composição do substrato não afetou a sobrevivência e o crescimento das plantas produzidas in vitro durante a aclimatização. As melhores respostas de enraizamento ex vitro foram obtidas com segmentos nodais, assim como com explantes tratados com 4920 μM de AIB e cultivados em substrato comercial + vermiculita + areia grossa. Tanto a manutenção in vitro de microcepas quanto o enraizamento ex vitro são técnicas promissoras para a produção de plantas de grápia. O marcador RAPD é eficiente para a análise genética e detectou alta variabilidade genética na grápia.

The thesis is focused on the research on micro-milling with the aim to specify the latest findings and trends in milling and micro-milling. The introduction consists of the specification of micro-milling and its comparison with conventional milling. The main goal of the thesis is to interpret modern trends in micro-milling technology, such as machine modernization, advanced machining strategies and the latest CAD/CAM software. The second part deals with the influence of cutting parameters on the overall workpiece quality. The final part is devoted to the application and use of micro-milling technology.