This work is concerned with the development of a new quantitative kinetic model for the analysis of hydrocarbon fuel droplet heating and evaporation, suitable for practical engineering applications. The work mainly focuses on the following two areas. Firstly, a new molecular dynamics (MD) algorithm for the simulation of complex hydrocarbon molecules, with emphasis on the evaporation/condensation process of liquid n-dodecane (C12H26), which is used as an approximation for Diesel fuel, has been developed. The analysis of n-dodecane molecules has been reduced to the analysis of simplified molecules, consisting of pseudoatoms, each representing the methyl (CH3) or methylene (CH2) groups. This analysis allows us to understand the underlying physics of the evaporation/condensation process of n-dodecane molecules and to estimate the values of its evaporation/condensation coefficients for a wide range of temperatures related to Diesel engines. Nobody, to the best of our knowledge, has considered MD simulation of molecules at this level of complexity. Secondly, a new numerical algorithm for the solution of the Boltzmann equation, taking into account inelastic collisions between complex molecules, has been developed. In this algorithm, additional dimensions referring to inelastic collisions have been taken into account alongside three dimensions describing the translational motion of molecules as a whole. The conservation of the total energy before and after collisions has been considered. A discrete number of combinations of the values of energy corresponding to translational and internal motions of molecules after collisions have been allowed and the probabilities of the realisation of these combinations have been assumed to be equal. This kinetic model, with the values of the evaporation coefficient estimated based on MD simulations, has been applied to the modelling of the heating and evaporation processes of n-dodecane droplets in Diesel engine-like conditions. In the previously developed kinetic models, applied to this modelling, all collisions were assumed to be elastic and the evaporation coefficient was assumed equal to 1. It is shown that the effects of inelastic collisions lead to stronger increase in the predicted droplet evaporation time relative to the hydrodynamic model, compared with the similar increase predicted by the kinetic model considering only elastic collisions. The effects of a non-unity evaporation coefficient are shown to be weak at gas temperatures around or less than 1,000 K but noticeable for gas temperatures 1,500 K. The application of the rigorous kinetic model, taking into account the effects of inelastic collisions and a non-unity evaporation coefficient, and the model considering the temperature gradient inside droplets is recommended when accurate predictions of the values of droplet surface temperature and evaporation time in Diesel engine-like conditions are essential.

Nowadays, the European automotive market is dominated by Diesel engines. Despite their high efficiency, these produce significant levels of pollutants. Among the various pollutants released, nitrogen oxides and soot are the main issues. Their formation is linked to the combustion process and attempts to reduce one often lead to an increase of the other. Laser diagnostics are among the best tools for experimental, non-intrusive studies inside combustion chambers for a better understanding of the complex combustion processes. Depending on the optical diagnostic, numerous combustion characteristics and processes can be investigated. The work presented here intends initially to develop a quantitative laser technique for characterising soot and, secondly, to further the knowledge on soot formation in Diesel engines by the application of this technique in an optical combustion chamber. Some of the main characteristics describing soot formation are the soot volume fraction, number density and particle sizes. Soot volume fraction is the major one as it is representative of the volume of soot produced. Planar characterisation of soot volume fraction, number density and particle size were achieved for the first time by simultaneous recording laser-induced incandescence (LII), laser scattering and two-colour time-resolved (2C-TiRe) LII signals. Qualitative planar distributions of particle diameter and soot volume fraction were derived from the image ratio of scattering and incandescence signals. 2C- TiRe LII technique allowed the simultaneous recording of the temporal LII signal for two different wavelengths in order to obtain quantitative values of the laser-heated particles temperature, soot volume fraction and particle size for a local or global part of the flame. These were used to recalibrate relative size and soot volume distributions. An initial development of the technique was performed on a laminar diffusion flame (Santoro burner) to validate its viability and performance. Equivalent temperature, soot volume fraction and particle diameter were determined throughout the flame. The results were found to be in good agreement with the ones published in the literature. The diagnostic was subsequently applied to an optical Diesel rapid compression machine, and further refinements were undertaken to cope with the higher soot concentration and lower LII signal. Tests were conducted for in-cylinder pressures ranging from 4 to 10 MPa, and injection pressures up to 160 MPa. A fixed injection timing and injected fuel quantity were used. Effects of in-cylinder pressure, fuel injection pressure and cetane number on soot formation and characteristics were observed. High injection pressure, cetane number and in-cylinder pressure caused a reduction of soot particle size and volume fraction but an increase of the soot particle density.

Vetronics in modern day military vehicles have evolved to include network enabled capability (NEC) allowing the use of electronics architectures to integrate different sub-systems. Integrated vehicle electronics (vetronics) offer improved performance, efficiency and new capabilities at the sub-system, system and system-of-systems level. However, this integration is associated with magnified risk and compromise from cyber-attacks. Potential cyber-attacks could be from an external source where a node is accessed by a malicious intruder using NEC, or internal to the vehicle such as a passive attack waiting to be triggered by an event. The aim of this work is to provide an understanding of applying survivable systems principles of preventive and reactive mechanisms, and proposes a vetronics survivability framework for the vehicle’s integrated vetronics in order to mitigate internal and external threats.

A responsividade aglutina princípios calcados em produtividade, flexibilidade e uso intensivo de tecnologia, capacitando empresas de manufatura a lidar com incertezas e operar de forma rentável no mercado globalizado. A manufatura busca na responsividade meios para sobreviver e crescer num ambiente de contínua mudança e incerteza, norteado pela concorrência global, exigências crescentes dos consumidores e avanço da tecnologia. O ciclo de expansão da indústria ainda tem fôlego para crescimento. O setor automotivo tem participação considerável na economia e gera efeito em cadeia na atividade industrial mundial. A indústria automotiva historicamente é uma precursora na reformulação de estratégias e no aprimoramento da eficácia operacional, através da adoção de tecnologias cada vez mais flexíveis e adaptáveis às oscilações do mercado competitivo. Este setor é um dos mais importantes do Rio Grande do Sul e do Brasil e sua dinâmica impõe condições responsivas às empresas. Ao assumirmos que a responsividade é o fator chave para alcançar e manter a vantagem competitiva no ambiente de manufatura, verificar como ela é utilizada, principalmente em empresas do setor automotivo, torna-se uma importante questão a ser tratada. O objetivo da pesquisa é analisar o conjunto de dimensões que representam a responsividade nas empresas de manufatura do setor automotivo. A pesquisa é qualitativa descritiva e aplicou o método de estudo de caso, através de uma investigação de casos múltiplos, realizada em quatro empresas com representatividade na cadeia automotiva do Rio Grande do Sul. A pesquisa utilizou como fontes de evidências: entrevistas, observações diretas e análise de documentos. Nas entrevistas, por se tratarem de perguntas abertas, foi utilizada a técnica de análise de conteúdo. As observações diretas, assim como a análise de documentos, ajudaram a complementar as informações obtidas nas entrevistas. Para interpretação do material obtido, foi utilizada a técnica de triangulação de dados. Inicialmente, cada empresa foi analisada individualmente, e depois houve a comparação dos casos para verificar similaridades ou diferenças para posterior produção de resultados mais confiáveis e generalizáveis. Através dos casos estudados constata-se que, apesar das diferenças de porte, nicho de atuação, valores e qualificação, entre outros, as empresas de manufatura do setor automotivo se valem de princípios comuns que resultam em ações e práticas responsivas. / The responsiveness merges principles based on productivity, flexibility and intensive use of technology, enabling manufacturing companies to deal with uncertainties and operate profitable in the global market. The manufacturing identifies in responsiveness ways to survive and grow in an environment of continuous change and uncertainty, guided by global competition, increasing on consumer demands and technology dissemination. The industry expansion cycle has yet impetus for growth. The automotive sector has considerable involvement in the economy and generates a chain effect on the global industrial activity. Historically, the automotive industry is a pioneer in strategies reformulation and operational efficiency improvement, through adoption of technologies more flexible and adaptable to fluctuations in competitive market. This sector is one of the most important for the Brazilian state, Rio Grande do Sul, and its dynamics imposes responsive conditions to the companies. We believe that the responsiveness is the key factor to achieve and maintain a competitive advantage in the manufacturing environment, therefore identify how it is used, mainly in automotive sector companies, is an important issue to be addressed. The objective of the present research is to analyze the set of dimensions that represent the responsiveness in manufacturing companies in the automotive industry. The qualitative descriptive research had used the “case study method” through a multiple-case study investigation, applied to four important companies of the Rio Grande do Sul automotive supply chain. This research used as evidence sources: semi-structured interviews, direct observation and documentation analysis. Open questions were applied in the interviews and the “content analysis technique” to support the interpretation. The direct observations, as well as the document analysis, helped to supplement information obtained in interviews. The data triangulation technique was used for material interpretation. Initially, each company was examined individually, and then the cases comparison to check similarities or differences to obtain more reliable and generalized results. Despite differences in organization size, performance niche, values and skills and others, the studies proved that manufacturing companies in the automotive sector have use common principles which result in responsive actions and practices.

The purpose of this research was to generate the knowledge for formulating low-Cu and Cu-free brake friction materials without using and releasing hazardous materials that are listed on Washington State and California State Senate Bills. Model brake material samples were manufactured and tested in the Friction Assessment and Screening Test (FAST) and the full scale automotive brake dynamometer (Dyno) using a SAE J2430 test procedure. The SAE recommended a J2430 test procedure which provided the necessary data for the Brake Effectiveness Evaluation Procedure (BEEP) by the Brake Manufacturers' Council. The newly developed low-Cu and Cu-free brake friction materials were formulated by modifying a typical Non Asbestos Organic (NAO) (T-Baseline) formulation and a typical Semi-Metallic (M-Baseline) formulation. The NAO Cu-free brake friction materials contain geopolymer and natural hemp fibers as a partial replacement of phenolic resin and synthetic Kevlar fibers, respectively. Friction performance and wear data from a series of FAST tests were used to train an artificial neural network, which was used to optimize the NAO Cu-free formulations. Then, the optimized low-Cu and Cu-free brake friction materials were tested on the Dyno. Dyno test results showed that all NAO Cu-free brake friction materials have passed the Brake Effectiveness Evaluation Procedure (BEEP), did not exhibit thermal fade when temperature was increased and were slightly sensitive to speed. The NAO Cu-free brake friction materials exhibits slightly lower average friction level when compared to the baseline materials (T-Baseline). The Cu-free brake friction materials, as well as the rotors, exhibit higher wear than the detected wear on the T-Baseline material. The semi-metallic low-Cu and Cu-free brake friction materials have also passed the BEEP. Dyno test results indicated that the semi-metallic low-Cu and Cu-free friction materials did not exhibit thermal fade and were slightly sensitive to speed. The semi-metallic low-Cu and Cu-free materials exhibited lower friction level and higher wear on the pads when compared to the M-Baseline material. The semi-metallic Cu-free material outperformed the M-Baseline material in term of rotor wear. Analyses using scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) microanalysis on the tested materials show that the friction surface of the T-baseline material was covered with fully developed and stable friction layer (third body) consisting mostly of Fe-oxides, different forms of carbon and compounds of materials originally present in the bulk material. The NAO Cu-free materials (T30-15 and T30-16) did not develop a sufficient friction layer. The friction layer seemed to be responsible for the detected lower wear in the T-Baseline compared to the NAO Cu-free materials (T30-15 and T30-16), and it acted as a solid lubricant on the interface between the rubbing pad and the cast iron rotor lowering the adhesive forces. The friction and wear of the T-Baseline material was controlled by adhesive mechanisms. The NAO Cu-free materials (T30-15 and T30-16) with content of geopolymer replacing phenolic resin matrix exhibited extensive abrasive wear in addition to adhesive mechanisms. The capacity to form a friction layer on the surface plays a considerable role when lowering the wear of NAO brake friction materials. The friction layer was formed by compaction and interaction of brake wear particles, and its stability and character depend on the chemistry of the bulk materials in contact as well as the temperature, pressure and sliding speed during a friction process. SEM and EDX analyses also showed that the semi-metallic pads have developed friction layer on the friction surfaces. The difference was that the M-Baseline material had well developed friction layer, but the Low-Cu (M4) and Cu-free (M5) materials, had many smaller patches of friction layer disturbed on the surfaces.

In recent decades, significant requirements of changes in composition of brake friction materials in order for faster and more reliable transportation as well as their environmental friendly characterizations attracted attentions. However, the relation between performance and formulation/composition is not clear since friction processes are accompanied by many complex problems such as instability in the coefficient of friction, noise, vibration and wear. Creep-groan is a low frequency vibration which could originate in different part of the system (vehicle). The resulting resonant vibration in the passenger compartment causes discomfort and often leads to complaints of customers and related increase of warranty costs covered by manufacturers. In spite of relatively large amount of publications addressing the creep-groan phenomena, there is not an universal solution addressing the engineering aspects of brake/vehicle design. In addition, Relevance of wear occurring in brake materials increased particularly with relation to the released chemicals and corresponding health and environmental hazards. It is well known that humidity can considerably modify the adhesion of rubbing counterfaces by creating menisci and increasing the contact area. The chemistry, morphology and phase composition of the friction layers (third body) generated on the friction surfaces could play a determining role when amounts of adsorbed water on brake surfaces is concerned. The friction layer is typically a complex mix of numerous materials and, as a rule, contains the agglomerated or sintered nanoparticles. Hence, quantum effects could further modify the adsorption of water. This work addresses the impact of humidity on wear and creep groan of two commercial brake material types: the so called i) "non-asbestos organic" (NAO) and the ii) "semi-metallic" (SM) brake materials rubbed against pearlitic gray cast iron rotors typically used in the passenger vehicles. The friction and wear tests were performed with the Universal Mechanical Tester (UMT) manufactured by Bruker and the wear surfaces/mechanisms were studied by using of scanning electron microscopy, energy dispersive X-ray microanalysis, and optical topography methods. The applied wear testing conditions were designed as a series of particularly designed drag tests and were performed at several different relative humidity levels ranging between 50% and 80%. The major findings confirmed the considerable effect of humidity on wear of brake materials. Both pad types wore noticeably less at increased humidity. This was ascribed to a better capacity to form a protective friction layer. The complex wear mechanisms including abrasive, adhesive, fatigue, and corrosion wear were observed on both material types, irrespectively of humidity levels, and they dependent on the chemistry and phase composition of the friction layer. Humidity also influenced the level of friction.

A utilização de ferramentas estruturadas na gestão da manutenção proporciona eficácia, segurança e qualidade nos processos produtivos, tornando os equipamentos mais disponíveis a um menor custo de manutenibilidade, aumentando a produtividade e, consequentemente, tornando as organizações mais competitivas. Nesta ótica, a MCC (Manutenção Centrada em Confiabilidade) tem sido amplamente utilizada no cenário automobilístico, setor este reconhecido por sua competitividade. Esta dissertação descreve a implementação da MCC em uma indústria do setor automobilístico, evidenciando as razões de aplicação da ferramenta no processo em questão, bem como ganhos em segurança, qualidade, produtividade, redução de custos e confiabilidade dos equipamentos. Para tanto, os passos metodológicos estão estruturados na seguinte ordem: (i) Seleção e capacitação de uma equipe multidisciplinar, (ii) Seleção do sistema/processo e coleta de informações, (iii) Análise de confiabilidade dos equipamentos críticos, (iv) Análise das funções e falhas funcionais, (v) Aplicação da FMEA (Análise de modos e efeitos de falha) e (vi) Determinação dos novos planos de manutenção. A implantação da MCC permitiu visualizar e aplicar melhorias em dois equipamentos responsáveis por 23% das falhas do processo registradas no período Pré-MCC. Os resultados deste estudo proporcionaram uma maior confiabilidade nos equipamentos através das ações direcionadas pelas análises estruturadas da FMEA, além de evidenciar uma evolução nos indicadores de desempenho dos equipamentos estudados. A aplicação da MCC levou ainda a uma significativa redução nos custos decorrentes de linha parada no valor estimado de US$ 428.102,94, referente ao período Pós-MCC (março a agosto de 2015). / The use of advanced tools for maintenance management increases processes efficacy, safety and quality, and increasing productivity and competitiveness. In that sense, the Reliability Centered Maintenance (RCM) has been widely used in the automotive scenario, which is recognized for its competitiveness. This thesis describes the implementation of the MCC in an automotive industry, highlighting the application of such tool in terms of safety, quality, productivity increasing, and cost reduction. The methodological steps rely on the following steps: (i) Selection and training of a multidisciplinary team, (ii) selection of the system / process and information gathering, (iii) Reliability analysis of critical equipments, (iv) Analysis the functions and malfunctions, (v) Application of FMEA (Failure Mode and Effect Analysis) and (vi) Determination of the new maintenance plans. The RCM implementation improved the performance of two equipments responsible for 23% of process failures recorded in the pre-MCC period. The results of this study also increased the equipment reliability through the actions directed by the FMEA, and depicted an evolution in the performance indicators of the studied equipment. The RCM application also led to a significant reduction in costs due to down machinery (US$ 428,102.94) for the period post-RCM (March-August 2015).

No description available.

Made available in DSpace on 2014-06-11T19:35:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-02-26Bitstream added on 2014-06-13T19:05:50Z : No. of bitstreams: 1 rocha_hm_dr_guara.pdf: 978455 bytes, checksum: b5f0c588360528590d2e12d3fea840f2 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este estudo buscou identificar os fatores críticos de sucesso dos processos de desenvolvimento de produtos na indústria automotiva situada na região Sulfluminense. Os referenciais teóricos utilizados são os fatores críticos de sucesso de Rockart. Partindo da literatura existente sobre o assunto e das deduções obtidas por prognósticos, foram identificados oito fatores críticos de sucesso. Estes foram avaliados por meio de pesquisa, na forma de entrevistas e questionários (método Delphi) em duas montadoras instaladas na citada região. Utilizando o método hipotético-dedutivo, os resultados foram testados estatisticamente e pelo método da lógica paraconsistente. Sete fatores foram considerados críticos para os processos de desenvolvimento de produtos: gerenciamento de custos e orçamentos; gerenciamento do tempo e prazos; posicionamento estratégico definido para o produto; atendimento das necessidades dos clientes; alinhamento organizacional; características do time de desenvolvimento; e processos de trabalho estabelecidos pelas organizações para o desenvolvimento de seus novos produtos. / This research purported to identify the critical success factors for the product development process used by the automotive industry in southern Rio de Janeiro state, Brazil. The theoretical referential used in this research was Rockart’s critical success factors. Having the existing literature about the subject and prognostic deductions as start points for this study, eight critical success factors have been identified and evaluated through research – interviews and questionnaires applied in two automaker plants in the Southern State of Rio de Janeiro, Brazil. Through the hypotheticaldeductive method, results have been statistical tested and also submitted to the paraconsistent logic evaluation. Seven success factors have been considered critical: management of costs and budgets, deadlines and time management, product strategic positioning, customer needs fulfillment, organizational alignment, characteristics of the development team, and work processes established by the organizations for new product development.

Este estudo propõe um método de avaliação de desempenho de práticas típicas da produção enxuta em indústrias de manufatura. As práticas utilizadas no método proposto são práticas enxutas operacionais (por exemplo, gerenciamento visual e troca rápida de ferramentas), diferentemente de estudos anteriores que focavam principalmente em práticas enxutas gerenciais. O método foi desenvolvido e testado em um estudo de caso realizado em uma empresa fabricante de juntas homocinéticas. Essa empresa vem adotando a produção enxuta (PE) como estratégia de produção em nível corporativo desde 2002. O método é composto de oito etapas: (a) uma avaliação da sua aplicabilidade, a qual implica em verificar se os objetivos das estratégias de manufatura podem ser atingidos através da produção enxuta; (b) uma avaliação preliminar do quanto a cultura organizacional é consistente com os princípios da produção enxuta – essa avaliação é feita através da aplicação de um checklist baseado em requisitos estabelecidos pelas Normas SAE J4000 e J4001; (c) entrevistas com gerentes para verificar suas percepções sobre os pontos fortes e fracos na implementação da produção enxuta – nesse estudo de caso, sete gerentes foram entrevistados: (d) aplicação de um checklist para avaliar o desempenho de um grupo de práticas enxutas, baseado na percepção de gerentes – nesse estudo de caso, sete gerentes preencheram o checklist e a média de desempenho de cada prática enxuta foi calculada; (e) o desenvolvimento de um ranking para avaliar a importância de práticas enxutas, baseadas na percepção de alguns gerentes envolvidos na etapa anterior; (f) seleção de indicadores de desempenho que possam quantificar indiretamente o desempenho de práticas enxutas, considerando os indicadores utilizados na empresa e indicadores utilizados em estudos anteriores; (g) coleta de dados referentes aos indicadores selecionados na etapa anterior ; (h) seminário para discutir os resultados coletados em todas as etapas anteriores. Os passos (g) e (h) não foram aplicados nesse estudo de caso. De forma geral, os resultados demonstraram que práticas enxutas fortemente associadas com a estabilidade básica, tais como a padronização, apresentaram desempenho fraco. / This study presents a method for assessing the performance of typical lean production practices in manufacturing industry. The practices encompassed by the proposed method are related to operational lean practices (e.g. visual management and single minute exchange of dies and tools), differently from previous similar studies that focused mostly on managerial lean practices. The method was developed and tested in a case study undertaken in a manufacturer of automobile axiles. This company has been adopting lean production as its manufacturing strategy since 2002. The method involves eight stages: (a) an assessment of its applicability, which implies checking whether the manufacturing strategy targets might be achieved through lean production; (b) a preliminary assessment of the extent to which the organizational culture is consistent with lean production principles – this assessment is made through the application of a check-list based on the requirements established by SAE J4000 and J4001 standards; (c) interviews with managers to identify their perceptions on strenghts and weaknesses of lean production implementation – in the case study, seven managers were interviewed; (d) application of a check-list to assess the performance of a set of lean practices based on managers perceptions – in the case study, seven managers filled out the check-list and an average degree of performance for each lean practice was then calculated; (e) the development of a ranking to assess the importance of lean practices, based on the perceptions of some of the same managers involved in the previous stages; (f) selection of performance indicators that could indirectly quantify the performance of lean practices, considering both the existing indicators in the company and existing indicators proposed in previous studies; (g) data gathering concerning results of the selected indicators; (h) a seminar to discuss the data collected during all the previous stages. Stages (g) and (h) were not carried out in the case study. Overall, the results pointed out that lean practices that are closely associated with basic stability, such as standardization, performed poorly.