abstract: Micromachining has seen application growth in a variety of industries requiring a miniaturization of the machining process. Machining at the micro level generates different cutter/workpiece interactions, generating more localized temperature spikes in the part/sample, as suggested by multiple studies. Temper-etch inspection is a non-destructive test used to identify `grind burns' or localized over-heating in steel components. This research investigated the application of temper-etch inspection to micromachined steel. The tests were performed on AISI 4340 steel samples. Finding, indications of localized over-heating was the primary focus of the experiment. In addition, change in condition between the original and post-machining hardness in the machined slot bottom was investigated. The results revealed that, under the conditions of the experiment, no indications of localized over-heating were present. However, there was a change in hardness at the bottom of the machined slot compared to the rest of the sample. Further research is needed to test the applicability of temper-etch inspection to micromilled steel and to identify the source of the change in hardness. / Dissertation/Thesis / M.S.Tech Technology 2010

Orientador: Alessandro Roger Rodrigues / Resumo: A microusinagem é um dos processos de fabricação capaz de produzir produtos ou geometrias de precisão e complexidade com detalhes menores que 1 mm. Contudo, para um melhor desempenho do processo de usinagem associado à qualidade do produto, entender a interação peça-ferramenta é fundamental. Esta pesquisa determinou a influência do tipo de corte e do avanço da ferramenta no desgaste da fresa (ferramenta), na energia específica de corte (processo) e na rugosidade (peça), ao empregar a operação de microfresamento de topo no aço COS AR60 de grãos ultrafinos. Os ensaios foram realizados em um centro de usinagem Romi D600 com a adaptação de um cabeçote de alta rotação (60 krpm) sem aplicação de fluido de corte. Microfresas de topo reto (Ø 800 µm) com substrato de metal duro e revestidas com TiAlN foram aplicadas nos testes. A profundidade de usinagem e a velocidade de corte foram mantidas constantes em 160 µm e 60 m/min, respectivamente. Foram variados o avanço por dente (3 e 10 µm/z) e o tipo de corte (simétrico em cheio e em face e assimétrico concordante e discordante). Análise de Variância (ANOVA) com intervalo de confiança de 95% foi aplicada a cada uma das três réplicas. Os resultados indicaram que os níveis de desgaste e a redução do diâmetro da microfresa são influenciados pelo avanço da ferramenta e tipo de corte. As maiores reduções no diâmetro (≈11%) foram devido ao impacto periódico da aresta de corte na peça e não pelo efeito de sulcamento (≈4%). Além disso, para o pe... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Micro-machining is one of the processes feasible for generating geometries or parts with precision and complexity regarding dimensions smaller than 1 mm. However, the achievement of enhanced machining performance and product quality requires a prior understanding on the tool-workpiece interface. This research detemined the influence of cutting type and cutting feed on wear (tool), specific cutting force (process) and surface roughness (workpiece) when cutting the ultrafine-grained steel COS AR60 under end milling strategy. Machining tests were performed in a CNC machining centre Romi D600 provided with a high-speed spindle (60kpm) without cutting fluid application. TiAlN coated carbide endmill (Ø 800 μm) was used for straight cut with 60 m/min cutting speed, 160 μm depth of cut and feed per tooth of 3 and 10 μm. Analysis of Variance (ANOVA) with confidence interval of 95% was applied to the three runs of each cutting sets. The results have shown that tool wear levels and tool effective diameter are influenced by tool feed and cutting type. Hence, intermittent impact of tool’s cutting edges into the workpiece (≈11%) during cutting revealed to be the major cause of tool wear when compared to cutting mechanism dominated by ploughing (≈4%). Regarding experimental sets with cutting length of 98,018 m there was a predominance of tool edge chipping over abrasion and adhesion when performing face cutting with ploughing at 4.2%. On the other hand, if ploughing increases to 14.3% the m... (Complete abstract click electronic access below) / Mestre

Submitted by Flávio Henrique Manarelli (flaviomanarelli@gmail.com) on 2018-11-01T23:57:49Z No. of bitstreams: 1 Dissertação_Flávio Henrique Manarelli.pdf: 2986064 bytes, checksum: edc4536a4c2ec5e96e1c49c52019885f (MD5) / Approved for entry into archive by Cristina Alexandra de Godoy null (cristina@adm.feis.unesp.br) on 2018-11-08T19:00:53Z (GMT) No. of bitstreams: 1 manarelli_fh_me_ilha.pdf: 2986064 bytes, checksum: edc4536a4c2ec5e96e1c49c52019885f (MD5) / Made available in DSpace on 2018-11-08T19:00:54Z (GMT). No. of bitstreams: 1 manarelli_fh_me_ilha.pdf: 2986064 bytes, checksum: edc4536a4c2ec5e96e1c49c52019885f (MD5) Previous issue date: 2018-09-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A microusinagem é um dos processos de fabricação capaz de produzir produtos ou geometrias de precisão e complexidade com detalhes menores que 1 mm. Contudo, para um melhor desempenho do processo de usinagem associado à qualidade do produto, entender a interação peça-ferramenta é fundamental. Esta pesquisa determinou a influência do tipo de corte e do avanço da ferramenta no desgaste da fresa (ferramenta), na energia específica de corte (processo) e na rugosidade (peça), ao empregar a operação de microfresamento de topo no aço COS AR60 de grãos ultrafinos. Os ensaios foram realizados em um centro de usinagem Romi D600 com a adaptação de um cabeçote de alta rotação (60 krpm) sem aplicação de fluido de corte. Microfresas de topo reto (Ø 800 µm) com substrato de metal duro e revestidas com TiAlN foram aplicadas nos testes. A profundidade de usinagem e a velocidade de corte foram mantidas constantes em 160 µm e 60 m/min, respectivamente. Foram variados o avanço por dente (3 e 10 µm/z) e o tipo de corte (simétrico em cheio e em face e assimétrico concordante e discordante). Análise de Variância (ANOVA) com intervalo de confiança de 95% foi aplicada a cada uma das três réplicas. Os resultados indicaram que os níveis de desgaste e a redução do diâmetro da microfresa são influenciados pelo avanço da ferramenta e tipo de corte. As maiores reduções no diâmetro (≈11%) foram devido ao impacto periódico da aresta de corte na peça e não pelo efeito de sulcamento (≈4%). Além disso, para o percurso de corte adotado de 98,018 m, com 4,2% da usinagem em sulcamento ou inexistente no corte em face, houve predominância de avarias por lascamento e, para o mesmo percurso, porém, com aproximadamente 14,3% do corte em sulcamento, os fenômenos predominantes no desgaste foram abrasão e adesão. O efeito do sulcamento fez com que os fatores tipo de corte e avanço, bem como suas respectivas interações, fossem significativos sobre a energia específica de corte. Os cortes em cheio e corte concordante com avanço de 3 µm/dente proporcionaram condições mais favoráveis para o microfresamento frontal, com melhor acabamento da peça e menores níveis de desgaste da ferramenta de corte. / Micro-machining is one of the processes feasible for generating geometries or parts with precision and complexity regarding dimensions smaller than 1 mm. However, the achievement of enhanced machining performance and product quality requires a prior understanding on the tool-workpiece interface. This research detemined the influence of cutting type and cutting feed on wear (tool), specific cutting force (process) and surface roughness (workpiece) when cutting the ultrafine-grained steel COS AR60 under end milling strategy. Machining tests were performed in a CNC machining centre Romi D600 provided with a high-speed spindle (60kpm) without cutting fluid application. TiAlN coated carbide endmill (Ø 800 μm) was used for straight cut with 60 m/min cutting speed, 160 μm depth of cut and feed per tooth of 3 and 10 μm. Analysis of Variance (ANOVA) with confidence interval of 95% was applied to the three runs of each cutting sets. The results have shown that tool wear levels and tool effective diameter are influenced by tool feed and cutting type. Hence, intermittent impact of tool’s cutting edges into the workpiece (≈11%) during cutting revealed to be the major cause of tool wear when compared to cutting mechanism dominated by ploughing (≈4%). Regarding experimental sets with cutting length of 98,018 m there was a predominance of tool edge chipping over abrasion and adhesion when performing face cutting with ploughing at 4.2%. On the other hand, if ploughing increases to 14.3% the main wear mechanism observed were abrasion and adhesion. Therefore, there was a significant interaction between specific cutting force and the input parameters of feed per tooth and cutting type. As a result, down-milling and channel-milling at the tool feed of 3 μm/tooth leaded to a valuable cutting performance with better workpiece surface roughness and tool wear at low levels.

Une des limitations du fonctionnement des grandes chaines lasers de puissance telle que le Laser MegaJoule, est la problématique de l’endommagement laser des composants optiques. Différents phénomènes physiques qui dépendent à la fois des propriétés des matériaux, de leurs conditions de fabrication/ préparation et des paramètres d’irradiation laser peuvent conduire à un amorçage de dommages sur la surface ou dans le volume, qui vont croître lors d’irradiations successives. Ce phénomène limite la montée en puissance, affecte la durée de vie des composants optiques et le coût de maintenance des chaînes laser. Il peut également être à l’origine de graves problèmes de sécurité. Pour remédier à cette croissance des dommages et augmenter la durée de vie des composants en silice, un procédé laser dit de «stabilisation » est étudié dans le cadre de cette thèse, l’objectif étant de traiter les dommages pour arrêter leur croissance sous tirs répétés afin de recycler les optiques endommagées. Ce processus consiste en une fusion, suivie d’une évaporation locale, par dépôt d’énergie localisé par un faisceau laser CO2, de la zone fracturée de silice. Nous nous sommes intéressés particulièrement à la stabilisation de dommages laser sur silice par un procédé de micro-usinage par laser CO2 dans le but de traiter des dommages de dimensions millimétriques. Cette technique est basée sur une micro-ablation rapide de la silice durant laquelle le faisceau laser est balayé à la surface du composant afin de former un cratère de forme ajustable (typiquement conique) englobant le site endommagé. Un banc d’expérimentations a ainsi été mis en place à l’Institut Fresnel pour développer et étudier ce procédé. Différents travaux numériques et expérimentaux ont également été menés pour valider et optimiser la technique. Nos travaux ont montré l’efficacité de ce procédé de micro-usinage par laser CO2 pour arrêter la croissance de dommages de plusieurs centaines de microns de largeur et de profondeur. Pour parvenir à cet objectif nous nous sommes appuyés sur la modélisation des phénomènes physiques mis en jeu lors des expériences de stabilisation en utilisant le logiciel de simulation multi-physique COMSOL. D’une part, le modèle thermique, développé au cours de cette thèse, permet de calculer la distribution de température dans le matériau pendant le tir laser avec ou sans mouvement du faisceau. Combinées à une approche thermodynamique, ces simulations thermiques permettent de décrire les transformations de la silice lors de l’irradiation afin de prédire la morphologie des cratères formés dans le verre. D’autre part, la partie mécanique du modèle permet de simuler la position et la valeur des contraintes résiduelles, générées dans le matériau autour du cratère CO2, lors de l’élévation de température suivie du refroidissement rapide. D’autres expériences concernant le traitement de fractures liées au polissage, ou des défauts de fabrication de réseaux de silice sont également traités dans ce manuscrit. / One limitation of the operation of large power lasers chains such as Laser MegaJoule, is the issue of laser damage of optical components. Different physical phenomena which depend on both the properties of materials, their conditions of manufacture / preparation and laser irradiation parameters can lead to damage initiation on the surface or in the volume, which will grow under successive irradiation. This effect limits the output power, affects the lifetime of the optical components and the maintenance cost of the laser. It can also cause serious safety problems. To address this issue and increase the lifetime of fused silica components, a laser process called "stabilization" is studied in this thesis, the aim being to treat the damage sites to stop their growth under repeated pulses for recycling damaged optics. This process consists of melting, followed by local evaporation by localized energy deposition by a CO2 laser beam of the damage site. We focused particularly on the stabilization of silica components by a micromachining process using a CO2 laser in order to treat millimeter size damages. This technique is based on fast micro-ablation of the silica during which the laser beam is scanned on the component surface to form an adjustable form of crater (typically conical) including the damaged site. A bench of experiments has been set up at the Fresnel Institute to develop and study this process. Various numerical and experimental works were also conducted to validate and optimize the technique. Our work has shown the efficiency of this micro-machining process by CO2 laser to stop the growth of damage to several hundred microns wide and deep. To achieve this goal we relied on modeling of physical phenomena involved in stabilization experiments using the COMSOL Multiphysics simulation software. First, the thermal model developed in this thesis is used to calculate the temperature distribution in the material during laser irradiation with or without movement of the beam. Combined with a thermodynamic approach, these thermal simulations can describe the transformation of silica during irradiation and predict the morphology of craters formed in the glass. Secondly, the mechanical part of the model can simulate the position and value of residual stress generated in the material around the crater after the temperature rise followed by rapid cooling. Other experiments on the treatment of fractures related to polishing on silica surfaces, or manufacturing defects on silica gratings are covered in this manuscript.

There is a growing demand for miniature, high-precision components and devices with micro-scale features for applications in biomedical systems, aerospace structures, and energy storage/conversion systems. Mechanical micromachining has become a leading approach to address this demand. In micromachining, a micro-scale cutting tool, such as a micro-endmill with a diameter as small as 10 um, is rotated by an ultra-high-speed (UHS) spindle (speeds greater than 60,000 rpm, reaching up to 500,000 rpm) to mechanically remove the material from a workpiece. Although micromachining resembles the traditional computer numerically controlled (CNC) machining processes, the micron-scale cutting tools, ultra-high-speed (UHS) spindles, and considerably tighter tolerance requirements bring unique challenges to micromachining.

Le micro-usinage de matériaux transparents est aujourd’hui un sujet d’intérêt mondial en recherche appliquée. L’emploi de lasers femtoseconde permet la micro-fabrication de composants optiques et de verres intelligents, ou la réalisation de cellules photovoltaïques. Dans ce contexte, cette thèse expérimentale se concentre sur l’absorption laser résolue en temps et en espace à la surface de matériaux diélectriques irradiés (silice fondue et saphir). Des impulsions femtoseconde (30 − 450 fs) dans l’infrarouge sont utilisées pour étudier l’efficacité de couplage de l’énergie laser pour l’ablation de matériaux dans un régime d’intensité intermédiaire (1-100 TW/cm²) lors de deux expériences. Un schéma pompe-sonde détermine la dynamique du plasma électrontrou à l’échelle femtoseconde et une expérience de déplétion laser mesure l’énergie absorbée. Une étude morphologique du matériau est réalisée, évaluant les seuils d’endommagement et d’ablation ainsi que les morphologies d’ablation. Nous établissons ensuite un bilan d’énergie de l’absorption laser responsable de l’enlèvement de matière. Les densités d’énergie typiques atteintes sont évaluées expérimentalement et confrontées à une modélisation avec propagation. Un excès de dépôt d’énergie par rapport à l’énergie de liaison du matériau au repos est mis en évidence, suggérant qu’un important chauffage du gaz d’électrons libres a lieu. Nous réalisons enfin une interprétation des données avec un regard technologique. Des guides à la réalisation de microsystèmes en régime d’ablation laser femtoseconde sont proposés, et démontrent l’intérêt d’impulsions sous 100 fs pour un procédé photonique. / This thesis concerns femtosecond laser absorption in dielectrics in the context of micromachining processes of glass materials. Prospected applications of this technology are optical component micro-fabrication, smart glass manufacturing, or photovoltaic cell patterning. In this context, we focus on the characterization in time and space of the absorption mechanisms occurring at the surface of irradiated dielectric materials (fused silica and sapphire). Using near-IR ultrashort pulses (30 − 450 fs) laser energy coupling efficiency for material ablation is studied at mid-intensities (1-100 TW/cm²) through two experiments. A pump-probe scheme determines the electron-hole plasma dynamics at femtosecond timescale and a laser depletion experiment measures the material absorption. A morphological study of the samples is performed, evaluating the damage and ablation thresholds as well as ablation morphologies. We then establish an energy balance of laser absorption responsible of matter removal. Typical energy densities reached are estimated through experiments and confronted to a propagative model. It is shown that the amount of absorbed energy is far above the bonding energy of the material at rest, suggesting that the major part of the absorbed energy is spent to heat the free electron gas. Finally, we propose a technological analysis of the experimental data. The interest of sub-100 fs laser pulses for photonic processes is evidenced, however at the cost of additional complexity. It provides guidelines for efficient direct laser ablation, making the results relevant for femtosecond processes.

This thesis investigates laser micromachining using a high pulse repetition frequency (high-PRF) femtosecond fibre laser. Three different types of industrial-grade metals, Stainless steel, Copper, and Aluminium are investigated. The impact of the processing parameters on material removal is studied. Finally the feasibility of the technology in three dimensional micro structuring is explored. The thesis contributes to clarify the main interaction mechanisms occurring in high-PRF femtosecond laser processing. Heat accumulation and particle shielding are identified as main material removal influencing mechanisms. As a result of heat accumulation, lowered ablation thresholds are detected for Aluminium (0.16 J/cm² at 1.02 MHz versus 0.33 J/cm² at 20 kHz) and Stainless steel (0.088 J/cm² at 1.02 MHz versus 0.11 J/cm² at 20 kHz). For the high heat conductive Copper heat accumulation is largely ruled out. Particle shielding is investigated by ultra high speed camera imaging. It is shown that the ablation plumes enlarge at the higher pulse repetition rates. A parameter study investigates material ablation. From this study, appropriate machining parameters are derived with regard to both high ablation rate and removal efficiency, and small roughness: Aluminium: 5 μm pulse spacing / 5 μJ pulse energy, Copper: 7.5 μm pulse spacing / 7 μJ pulse energy, Stainless steel: 5 μm pulse spacing / 3 μJ pulse energy. In addition experimentally and theoretically determined volume ablation rates are compared. For this, a material removal calculation model is designed. Good agreements between theoretical and experimental values are obtained by taking into account effective penetration instead of optical penetration for energy transport. A surface temperature calculation model is designed, providing useful insights into heat accumulation. Heat accumulation observed for Aluminium and Stainless Steel is confirmed by surface temperature rise, calculated based on the remaining energy. Improvement of the model by enhanced energy coupling yields surface temperatures above the melting temperature. This is conclusive to experimental observations. Finally the feasibility of the high-PRF femtosecond laser technology in micromachining is demonstrated by micro mould fabrication. Utilising these moulds, micro-fluidic plastic demonstrators are fabricated by micro-injection moulding.

This report covers the investigation of the next generation of sensors to be used in the sensor based tube system known as SentusysTM. One essential feature of the next generation of sensors is high-temperature endurance. The sensors (strain gauges and thermocouples) have been produced by means of thermal spraying techniques, short-pulse laser ablation and laser cladding. It has been found that the sensors seem to work in general, however, much research and development remain.

Microfluidics is a field of research that enables the manipulation of fluids in the submillimetre length scale. The technology allows the development of lab-on-a-chip devices, which are miniaturized systems for chemical and biological analysis. Currently, the conventional manufacturing methods for these systems require multiple time-consuming steps. Therefore, focus has shifted towards laser micromachining as an alternative method. Direct laser writing would circumvent many of the steps required for the conventional methods, drastically reducing the process time. In this Master thesis project, it was shown that microfluidic chips can be manufactured using a Nd:YVO4 (532 nm) nanosecond laser system. The process was optimized for silicon and borosilicate glass substrates. Acoustic focusing of polystyrene beads was demonstrated for a system etched in silicon. The optimized process used a power of 50%, a frequency of 10 kHz, a scan speed of 60 mm/s with triple lines as fill type and it had an etch rate of 4.3 μm/pass. Processed wafers were cleaned in buffered HF and bonded using anodic bonding as well as adhesive bonding. Processing of glass proved unpredictable, resulting in cracks and chippings. However, in- and outlets were successfully etched through thin glass wafers. It was found that crucial factors for the process were to control the focus, positioning of structures, structure orientation and the pulse separation for a uniform distribution of pulses. Based on the results, it is estimated that the manufacturing process could be done in two to three days using the laser micromachining process.

Les travaux de cette thèse portent sur le développement (modélisation, conception, réalisation et tests) d’une surface intelligente (smart surface) composée d’un réseau d'actionneurs numériques MEMS, capables de mouvoir des charges posées dessus. Pour la réalisation de ces smart-surfaces, deux voies ont été explorées : un actionnement par voie électromagnétique, constituée d’aimants fixes et mobiles, et un actionnement utilisant des éléments bistables couplés à des alliages à mémoire de forme. Dans le premier cas, la simulation de l’interaction magnétique entre un micro-actionneur et le champ créé par des pistes conductrices placées à proximité a été réalisée. Un réseau de 5x5 micro-actionneurs électromagnétiques quadristables a été ensuite conçu, réalisé et caractérisé. Ce démonstrateur est fonctionnel en convoyage d’objets légers en translation et en rotation. Dans le second cas, la conception et la réalisation d’un actionneur MEMS élémentaire ont été menées : des modèles analytiques ont été confrontés aux résultats obtenus par éléments finis, et enfin comparés aux résultats expérimentaux. Ces travaux ciblent la problématique de la commande des systèmes mécatroniques, à actionneurs multiples, aux échelles méso ou microscopique. La connectique associée est un problème récurrent dans les systèmes fortement miniaturisés, les structures présentées ici présentent un fort potentiel de réduction des connexions filaires, voire leur élimination complète. / The work of this doctoral thesis involves in developing a smart surface (including modelling, design, fabrication and tests), composed of an array of MEMS digital actuators, capable of moving objects placed on it. In order to produce these smart surfaces, two actuation types were explored: electromagnetic actuation on fixed and mobile magnets and optothermal actuation of shape memory alloys on bistable elements. In the first case, simulation of the magnetic interaction between a micro-actuator and the magnetic field generated by nearby current wires was performed. Then, an array of 5x5 quadristable electromagnetic micro-actuators was designed, produced and characterized. This demo prototype is functional for small-weight object conveyance by translation and rotation. In the second case, design and fabrication of an elementary MEMS actuator were carried out: analytical models were confronted with the results from Finite Element Analysis, and at last compared to experimental ones. This work targets at the issue of controlling multiple-actuator mechatronics systems, at meso- or micrometric scale. Since the associated connectors are a recurring problem in highly miniaturized systems, the structures presented herein demonstrate important potential of cabling reduction, even towards complete wireless configurations.