Orientador: Paulo Roberto de Aguiar / Banca: Rosemar Batista da Silva / Banca: Eduardo Carlos Bianchi / Resumo: O processo de retificação é considerado um dos últimos na cadeia de produção de peças de precisão. O aumento excessivo da temperatura na zona de corte pode causar a queima superficial ou modificações estruturais do material que está sendo usinado. Assim, o presente trabalho tem por objetivo desenvolver um método de detecção da queima da peça no processo de retificação plana, baseado na análise do espectro do sinal de emissão acústica (EA) puro e com a aplicação de filtros digitais, e posterior implementação por hardware. Ensaios experimentais foram realizados numa máquina retificadora plana, onde um banco de ensaios foi desenvolvido empregando dois tipos de rebolos: óxido de alumínio e CBN com ligante resinoide; dois tipos de materiais: aço ABNT 1045 e VC131. Para a caracterização da superfície das peças quanto aos níveis de queima, inspeção visual e medidas de rugosidade e microdureza forma realizadas após os ensaios. Notou-se no espectro do sinal de EA faixas de frequências com amplitudes mais significativas entre 15kHz a 1MHz e, portanto, quinze bandas de frequência foram selecionadas para estudo. Filtros digitais do tipo Buterworth passa-faixa, ordem 6, foram aplicados nos sinais puros de EA e, posteriormente, o valor EA RMS e o parâmetro DPO foram obtidos com e sem a aplicação dos filtros. Os resultados obtidos da comparação dos valores RMS de EA e do parâmetro DPO demonstram que o uso de filtros digitais, em determinadas frequências, produziu um sistema de detecção da queima mais eficiente. Além disso, foi desenvolvido um hardware microcontrolado e um software que coletam os sinais de EA (RMS) e potência elétrica do motor de acionamento do rebolo por intermédio de um controlador digital de sinais (dsPIC). Em seguida, esses sinais foram processados por meio de... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The result of the grinding process depends on the conditions of the grinding wheel surface. With use, the ginding wheel pores are impregnated with the chip, resulting in loss of ability to cut and thus incresing the temperature in the region of contact between the surface of the grinding wheel and the workpiece. This increase in temperature when excessive can cause burning surface or changes in the structure of the material. Thus, this paper aims to propose a method for detecting burning in the grinding process based on the anlysis of the spectrum of the raw acoustic emission (AE) signal and application of digital filters, followed by hardware implementation. Experimental tests were performance using aluminum oxide grinding wheel and the CBN superabrasivee resinoid in a grinding machine, where a test bench was developed. Data were collected using ABNT 1045 and VC 131 steels. It was noted in the spectra of the AE signal frequency bands with significant magnitudes between 15 kHz to 1MHz, and therefore, fifteen frequency bands were selected for this study. Buterworth type digital filters, bandpass, 6th order, were applied to the raw. AE signal, and RMS AE values and DPO parameter were obtained with and without filtering. The results showed a more efficient burn detectionj system when using digital filtering at certain frequency bands. Additionally, a microcontroller hardware and software were developed, which collected the AE signals (RMS) and electric power the from the induction motor drive of the wheel via a digital signal controller (dsPIC). Then, these signals were processed by a burn detection algorithm, generating a control signal... (Complete abstract click electronic access below) / Mestre

Orientador: Paulo Roberto de Aguiar / Banca: Wisley Falco Sales / Banca: Eduardo Carlos Bianchi / Resumo: No processo de retificação com rebolo convencional, a operação de dressagem é preocupante, pois é geradora de tempo improdutivo, consumindo capacidade de máquinas e mão-de-obra normalmente especializada, além de consumo de energia elétrica, de rebolo e do próprio dressador. As indústrias brasileiras que trabalham com retificação, não controlam de maneira criteriosa os parâmetros de dressagem dos rebolos, uma vez que seriam necessários projetor de perfis, controle de rotação do rebolo e do passo de dressagem. Assim, este trabalho teve como objetivo monitorar a dressagem na retificação, propondo um conceito alternativo para esta operação, onde técnicas de monitoramento e processamento de sinais foram utilizadas sobre o sinal puro de emissão acústica captado durante a dressagem. Para isso, foi... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In grinding process with aluminum oxide grindign wheel the dressing operation brings preocupation since it is a time-unproductive source, consuming machining capability and usually specialized operator work as well as electrical energy consumption and the wear of the grinding wheel and dresser itself. The Brazilian industries that employ grinding processes do not control the dressing parameters efficiently due to the need of profile measurement equipament, control of grinding wheel speed and dressing passes control. Thus, this work aims to monitor the dressing operation and present and alternative concept for such operation, where digital signal processing and signal monitoring techniques were employed in the raw acoustic emission signal collected during the dressing operation. Dedicated software... (Complete abstract click electronic access below) / Mestre

Certains procédés d'électrolyse industriels, comme ceux de production de fluor et d'aluminium, génèrent du gaz sur des électrodes peu mouillées par l'électrolyte. Dans ces procédés, la convection est en grande partie induite par le mouvement des bulles. Le temps de résidence du gaz n'étant pas maitrisé, la modélisation de ces électrolyses se heurte à de nombreux défis. Ce travail propose un état des connaissances nécessaires à la modélisation de ce type de cellules. Après avoir mis au point une méthode permettant de réaliser des électrodes fortement hydrophobes, nous avons étudié le dégagement gazeux que celles-ci produisent. Nous avons observé que les bulles qui s'y forment croissent par coalescence et ce phénomène affecte la vitesse de croissance et la taille au détachement. Par la suite, nous avons démontré qu'en localisant le dépôt hydrophobe il est possible d'obtenir une population de bulles dont le nombre, la taille et la position sont maitrisés. Nous avons constaté que l'émission acoustique est un outil efficace pour mesurer, sans observation visuelle, la taille et la vitesse d'ascension des bulles produites par électrolyse. La fréquence la plus énergétique du spectre des salves d'émission acoustique des cellules d'électrolyse produisant du gaz permet, quand la fraction volumique de gaz est faible, de mesurer la taille de toutes les bulles dans la cellule. Quand les bulles sont nombreuses et denses, cette même fréquence est liée aux dimensions de la cellule, à la densité de courant, à la taille des bulles et à la fraction volumique en gaz dans le panache. Nous avons proposé une explication à cette observation basée sur l'hypothèse d'un couplage acoustique des bulles. En l'absence d'agitation vigoureuse, l'activité acoustique d'une cellule d'électrolyse produisant des bulles traduit l'importance du transport de matière aux électrodes. La mesure de la répartition de la densité de courant par la méthode des électrodes segmentées dans une cellule en convection libre a été réalisée. Cette étude a été menée dans le but de tester un outil de simulation numérique des cellules d'électrolyse produisant du gaz. L'effet de la mouillabilité de l'électrode sur la répartition du courant a été évalué. / Molten salts electrochemical processes, like fluorine and aluminium production processes produce bubbles on electrodes slightly wetted by an electrolyte. In those cells, the electrolyte convection is mainly induced by the motion of bubbles. Then, the residence time of gas is not under control and the modelling of such electrolysis still faces many challenges. This work begins with a collection of the information required to model gas-producing cells. We developed an electrochemical composite coating technique to achieve the production of highly hydrophobic electrodes. Then we studied the gas evolution obtained with these electrodes, we observed that coalescences determines the bubbles growth rate and sizes at detachment. When the hydrophobic deposit is local, it is possible to obtain a bubble population whose number, size and position are controlled. We found that the acoustic emission is an effective tool to measure the size and rising speed of bubbles produced by electrolysis without having to observe them visually. When the volume fraction of gas is low, the most energetic frequency of the spectrum of acoustic emission bursts allows measuring the size of all bubbles in the cell. When bubbles are numerous, the most energetic frequency of the acoustic emission spectrum is related to the dimensions of the cell, current density, sizes of the bubbles and gas volume fraction in the plume. We have proposed an explanation for this observation based on the assumption of an acoustic coupling of the bubbles. When bubbles are produced, the acoustic activity of an electrolysis cell is correlated with the mass transport at electrodes. We propose a set of measurements of the distribution of current density at the electrodes in a cell with electrolyte free convection. These measurements have been carried out to benchmark a numerical simulation tool. The effect of the wettability of the electrode on the current distribution was evaluated.

Atualmente, a maior parte das indústria de manufatura utiliza seus operadores de máquinas para fazer a verificação dimensional das peças usinada. Esses operadores geralmente escolhem algumas amostras aleatoriamente, num determinado período de tempo, para fazer a inspeção manual, ou utilizam dispositivos de medição automáticos no lote todo. Esses procedimentos podem implicar em perda de tempo, ou grandes investimentos, o que eleva os custos do produto final. Este trabalho propõe uma nova metodologia para a medição de peças em processo de retificação, utilizando uma máquina retificadora com funções inteligentes. As tecnologias de um encoder incremental óptico rotacional e de um chip contador são utilizadas para fazer o monitoramento da posição do cabeçote porta rebolo. Utilizando um sistema de cooordenadas baseado no Comando Numérico (CN) da máquina, associado a inspeção por Emissão Acústica (EA) pode-se monitorar a posição do rebolo do ponto de início ciclo de retificação até o início do contato com a peça. Os erros associados a deformação térmica da máquina e o desgaste do rebolo são levados em consideração e compensados. Desta maneira, é possível medir a dimensão e a excentricidade das peças geradas pela operação imediatamente anterior, com uma precisão suficiente. Este sistema pode ajudar na redução do nível de refugo e do tempo total de e produção, criando um diferencial para o aumento da confiabilidade do processo e da automação. / Most of the industries today use their machine operators to make the Workpiece dimensional verification. For this task they generally chose samples, doing manual inspection, or use automatic measuring devices in a whole lot. These procedures can implies in loss of time, a high investment, what may raise the costs of the final product. This work proposes a new methodology for in-process workpiece gagging, using a grinding machine associated with intelligent functions. The technology of an incremental rotational optical encoder and an external counter chip are used to perform the wheel head position monitoring. Using a NC (Numerical Control) coordinate system associated with AE (Acoustic Emission) inspection it was possible to get the position of the grinding wheel from the start of the grinding cycle until the first contact with the workpiece. The errors associated with the grinding machine deformation and wheel wear are considered and compensated. Thus, it is possible to measure the dimension and the run out of the workpiece, generated by a previous operation, with enough precision. This system may help to reduce the scrap leveI and the overall production time, creating a differential for process reliability and automation.

Uma das dificuldades do processo de retificação center-less é o estabelecimento de padrões confiáveis que determine com pequena margem de erro problemas no processo. Este trabalho visa desenvolver um sistema de monitoramento capaz de identificar falhas ocorridas durante a dressagem e o processo de retificação center-less acima dos centros de hastes de válvulas. Para tanto, inicialmente, foi feito um estudo teórico e prático acerca do processo de retificação center-less com o objetivo de conhecer seus elementos básicos, características, principais problemas e fatores que influenciam o processo. Em função da grande aplicação da emissão acústica em operações de retificação, foi desenvolvida uma nova metodologia, onde foi possível criar um mapa digital, baseado em informações acústicas detalhadas do processo, usando para isto uma constante de tempo muito pequena. Os resultados mostraram a potencialidade do sistema de mapeamento em detectar e diagnosticar problemas ocorridos durante processos de retificação e dressagem. Assim, pode-se atuar sobre o processo de tal forma a corrigir estas anomalias. / One of the difficulties of the center-less grinding process is to establish reliable patterns to determine, with a small error, problems in the process. This work aims to develop an monitoring system able to identify flaws happening during the dressing and the center-less grinding process above the center of values stems. Initially a theoretical and practical study was conduct on the center-less grinding process with the objective of discussing its basic elements, characteristics, main problems and factors that influence the process. Due to the great application of acoustic emission in grinding operations a new methodology was developed, where it was possible to create a digital map, based on detailed acoustic information on the process using for this a very short time constant. The results showed the potentiality of this mapping system to detect and to diagnose problems during grinding and dressing. Therefore, it is possible to correct anomalies when plunge center-less grinding process.

A viabilização do conceito de manufatura enxuta depende da redução da necessidade de intervenções do operador no processo. Na usinagem dos metais, uma das principais situações onde está a intervenção se faz necessária é a determinação da condição de fim de vida das ferramentas de corte, a qual é muitas vezes subjetiva e não pode ser prescrita com segurança. Sendo a emissão acústica (EA) um sinal gerado pelos principais fenômenos envolvidos na usinagem, um sistema de monitoramento de desgaste de ferramentas baseado neste tipo de sinal foi avaliado em operação de torneamento de eixo de saída de transmissão mecânica caracterizado por geometria complexa. Verificou-se que há uma relação entre a trajetória da ferramenta e a \"assinatura\" do processo (tensão RMS plotada contra o tempo). Além disso, há uma forte correlação destes mais a adesão de material da peça à ferramenta determinaram pequena diferença de amplitude do sinal entre os estágios iniciais e finais de vida das ferramentas. Além disso, a influência do sistema de fixação na EA mostrou-se diversas vezes maior que a influência do desgaste. Portanto, um sistema de monitoramento de desgaste baseado apenas em emissão acústica não seria adequado para a situação estudada. / The Lean Manufacturing concept depends on the reduction of the necessity of interventions in the process by the operators. ln metal machining, one situation where these interventions are necessary is the determination of tool life, which is subjective. Besides that, the toollife prediction is not reliable. Acoustic emission signals are generated by many activities involved in machining. Therefore an acoustic emission based tool wear monitoring system was evaluated in a turning operation of a mechanical transmission main shaft characterised by complex geometry. lt was found that there is a relationship between the tool track and the AE \"signature\" of the process (RMS voltage plotted versus time). Furthermore, there is a strong correlation between crater and flank tool wear and the AE signal, but the combination of them plus adhesion phenomena determine low amplitudes between initial and final stages of the tool life. Besides that, the influence of the fixture system was found to be several times higher than the influence of the wear. Therefore, a tool wear monitoring system based on acoustic emission only would not be adequate for this application.

Orientador: Emerson Luiz de Biaggi / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Artes / Made available in DSpace on 2018-08-23T20:57:48Z (GMT). No. of bitstreams: 1 Alves_CristianoSiqueira_D.pdf: 141564682 bytes, checksum: 37e4bef5d9c30e880d0887af29f59e4e (MD5) Previous issue date: 2013 / Resumo: O processo de emissão do som na clarineta revela-se de substancial importância à performance sendo, paradoxalmente, parcialmente negligenciado enquanto perspectiva de geração e transmissão de conhecimento explícito. O aspecto "oculto" de inúmeros procedimentos físico-musculares, ocorridos no interior do trato vocal, contribui para a complexidade evidenciada na abordagem da questão, sendo esta fortemente apoiada, por conseguinte, em bases tácitas. O presente trabalho propõe um Plano de Instrução, desenvolvido e validado com a colaboração de um grupo de pesquisa constituído para este fim, voltado à perspectiva de incremento de procedimentos de feedback (sobretudo motor e auditivo), da propriocepção e do domínio de emissão do som na clarineta. A principal ferramenta utilizada no plano de instrução vem a ser a "Teoria dos 'Ns'", por meio da qual objetiva-se a otimização do controle sobre os distintos níveis de pressão do lábio inferior. Tal controle, atuando em direta consonância com procedimentos de manipulação do trato vocal e aliado ao domínio sobre o fluxo de ar, demonstrou efetiva funcionalidade na tarefa de promover as condições propícias à maximização de fenômenos ressonantais no trato vocal. Entendeu-se ser a capacidade de obtenção e sustentação de um estado otimizado de relaxamento labial, portanto, um dos mais representativos meios de incremento da emissão do som na clarineta. Mensurou-se também o impacto do referido domínio de emissão sobre a performance como um todo. A pesquisa-ação configurou-se como a metodologia de pesquisa utilizada na elaboração e aplicação do plano de instrução, que estabeleceu, ainda, importantes bases de correlação entre elementos posturais e o manuseio das estruturas do trato vocal, bem como aplicabilidades no campo didático / Abstract: The process of sound production on the clarinet reveals substantial importance to performance and, paradoxically, is partially overlooked as a generation and transmission of explicit knowledge perspective. The "hidden" aspect of numerous physical muscle procedures, occurred within the vocal tract, contributes to the complexity evident in addressing the issue, which is strongly supported, therefore, on tacit bases. This work proposes an Instruction Plan, developed and validated in collaboration with a research group constituted for this purpose, concerning the increment of feedback procedures (especially motor and auditory), proprioception and mastery of sound production in the clarinet. The main tool used in instruction plan was the "'Ns' Theory", by means of which the goal is to optimize the control of the different lower lip pressure levels. This control, acting in direct line with procedures for handling the vocal tract and associated to the air flow domain, demonstrated effective functionality in the task of promoting the conditions for maximizing resonance effects in the vocal tract. It was understood that the ability to obtain and sustain an optimal state of relaxation lip, therefore, is one of the most significant means of increasing the sound production in the clarinet. It was also measured the impact of this domain on the performance as a whole. Action research was used as the research methodology for the development and implementation of the instruction plan, which also established important bases of correlation between postural elements and handling of the structures of the vocal tract as well as applicability in the field of teaching / Doutorado / Praticas Interpretativas / Doutor em Música

This research project aimed to develop a condition monitoring system for the final production quality of pharmaceutical tablets and detection capping and lamination during powder compression process using the acoustic emission (AE) method. Pharmaceutical tablet manufacturers obliged by regulatory bodies to test the tablet's physical properties such as hardness, dissolution and disintegration before the tablets are released to the market. Most of the existing methods and techniques for testing and monitoring these tablet's properties are performed at the tablet post-compression stage. Furthermore, these tests are destructive in nature. Early experimental investigations revealed that the AE energy that is generated during powder compression is directly proportional to the peak force that is required to crush the tablet, i. e. crushing strength. Further laboratory and industrial experimental investigation have been conducted to study the relationship between the AE signals and the compression conditions. Traditional AE signal features such as energy, count, peak amplitude, average signal level, event duration and rise time were recorded. AE data analysis with the aid of advanced classification algorithm, fuzzy C-mean clustering showed that the AE energy is a very useful parameter in tablet condition monitoring. It was found that the AE energy that is generated during powder compression is sensitive to the process and is directly proportional to the compression speed, particle size, homogeneity of mixture and the amount of material present. Also this AE signal is dependent upon the type of material used as the tablet filler. Acoustic emission has been shown to be a useful technique for characterising some of the complex physical changes which occur during tabletting. Capping and lamination are serious problems that are encountered during tabletting. A capped or laminated tablet is one which no longer retains its mechanical integrity and exhibit low strength characteristics. Capping and lamination can be caused by a number of factors such as excessive pressure, insufficient binder in the granules and poor material flowabilities. However, capping and lamination can also occur randomly and they are also dependent upon the material used in tabletting. It was possible to identify a capped or laminated tablet by monitoring the AE energy level during continuous on-line monitoring of tabletting. Capped tablets indicated by low level of AE energy. The proposed condition monitoring system aimed to set the AE energy threshold that could discriminate between capped and non-capped tablets. This was based upon statistical distributions of the AE energy values for both the capped and non-capped tablets. The system aims to minimise the rate of false alarms (indication of capping when in reality capping has not occurred) and the rate of missed detection (an indication of non capping, when in reality capping has occurred). A novel approach that employs both the AE method and the receiver operating characteristic (ROC) curve was proposed for the on-line detection of capping and lamination during tabletting. The proposed system employs AE energy as the discriminating parameter to detect between capped and non-capped tablets. The ROC curve was constructed from the area under the two distributions of both capped and non-capped tablet. This curve shows a trade-off between the probabilities of true detection rate and false alarm rate for capped and non-capped tablet. A two-graph receiver operating characteristic (ROC) curve was presented as a modification of the original ROC curve to enable an operator to directly select the desired energy threshold for tablet monitoring. This plot shows the ROC co-ordinate as a function of the threshold value over the entire threshold (AE energy) range for all test outcomes. An alternative way of deciding a threshold based on the slope of the ROC curve was also developed. The slope of the ROC curve represents the optimal operating point on the curve. It depends upon the penalties cost of capping and the prevalence of capping. Sets of guidelines have been outlined for decision making i.e. threshold setting. These guidelines take into account both the prevalence of capping in manufacturing and the cost associated with various outcomes of tablet formation. The proposed condition monitoring system also relates AE monitoring to non-AE measurement as it enable an operator predicting tablet hardness and disintegration form the AE energy, a relationship which was established in this research.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第15338号 / 工博第3217号 / 新制||工||1484(附属図書館) / 27816 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 石田 毅, 教授 松岡 俊文, 教授 三ケ田 均 / 学位規則第4条第1項該当

It is widely acknowledged that bearing failures are the primary reason for breakdowns in rotating machinery. These failures are extremely costly, particularly in terms of lost production. Roller bearings are widely used in industrial machinery and need to be maintained in good condition to ensure the continuing efficiency, effectiveness, and profitability of the production process. The research presented here is an investigation of the use of acoustic emission (AE) to monitor bearing conditions at low speeds. Many machines, particularly large, expensive machines operate at speeds below 100 rpm, and such machines are important to the industry. However, the overwhelming proportion of studies have investigated the use of AE techniques for condition monitoring of higher-speed machines (typically several hundred rpm, or even higher). Few researchers have investigated the application of these techniques to low-speed machines (<100 rpm), This PhD addressed this omission and has established which, of the available, AE techniques are suitable for the detection of incipient faults and measurement of fault growth in low-speed bearings. The first objective of this research program was to assess the applicability of AE techniques to monitor low-speed bearings. It was found that the measured statistical parameters successfully monitored bearing conditions at low speeds (10-100 rpm). The second objective was to identify which commonly used statistical parameters derived from the AE signal (RMS, kurtosis, amplitude and counts) could identify the onset of a fault in either race. It was found that the change in AE amplitude and AE RMS could identify the presence of a small fault seeded into either the inner or the outer races. However, the severe attenuation of the signal from the inner race meant that, while AE amplitude and RMS could readily identify the incipient fault, kurtosis and the AE counts could not. Thus, more attention needs to be given to analysing the signal from the inner race. The third objective was to identify a measure that would assess the degree of severity of the fault. However, once the defect was established, it was found that of the parameters used only AE RMS was sensitive to defect size. The fourth objective was to assess whether the AE signal is able to detect defects located at either the centre or edge of the outer race of a bearing rotating at low speeds. It is found that all the measured AE parameters had higher values when the defect was seeded in the middle of the outer race, possibly due to the shorter path traversed by the signal between source and sensor which gave a lower attenuation than when the defect was on the edge of the outer race. Moreover, AE can detect the defect at both locations, which confirmed the applicability of the AE to monitor the defects at any location on the outer race.