<p>Disertacija je posvećena problemima<br />o&scaron;tećenja cevi pirolitičkih peći u fabrici etilena,<br />kao i metodima procene preostalog ţivotnog<br />veka cevi peći, uop&scaron;tava teorijska i praktična<br />istraţivanja koja su sprovedena za vreme<br />trajanja doktorskih studija.<br />Peć za pirolizu benzina je uzeta kao tipičan<br />primer za proučavanje preostalog ţivotnog veka<br />na osnovu prikupljenih podataka o cevima peći,<br />kao &scaron;to su: redukcija debljine zida, povećanje<br />spoljnjeg prečnika, tvrdoća i metalografska<br />istraţivanja, itd., a eksperimentalni rezultati su<br />dobiveni iz pripremljenih isečaka cevi peći.<br />Razmatra se veliki kompleks pitanja povezan<br />sa problemom tačnosti procene ţivotnog veka.<br />Iako otkaz cevi peći nije veliki bezbednosni<br />problem, procena preostalog ţivotnog veka cevi<br />je značajna zbog u&scaron;tede tro&scaron;kova koji proizilaze<br />iz optimizacije procesnih parametara ili<br />redukcije frekvence ispitivanja i prevazilaţenja<br />neplaniranih zastoja.</p> / <p>The dissertation is devoted to<br />problems of pyrolysis furnace tubes<br />damage in ethylene plant, and methods of<br />assessment of the furnace tube remaining<br />life, generalizes the theoretical and<br />practical research that is conducted during<br />the doctoral studies.<br />Furnace for the gasoline pyrolysisis<br />taken as a typical example for the study of<br />the remaining life based on data collected<br />on the furnace tube, such as the reduction<br />of wall thickness, increasing the outer<br />diameter, hardness and metallographic<br />testing, etc.., and experimental results<br />were obtained from prepared furnace tube<br />slices.<br />Discusses the major issues associated<br />with the complex problem of the accuracy<br />of life expectancy. Although furnace tube<br />failure isn&rsquo;t a major security problem, the<br />tube remaining life estimation is important<br />because of cost savings resulting from the<br />optimization of process parameters or<br />reducing the frequency of tests and<br />overcome unplanned downtime.</p>

In this thesis we look at one of the aging mechanisms that may have affected current aged Nuclear Power Plants (NPPs). Irradiation as an age-related degradation mechanism is studied for Reinforced Concrete (RC) in NPPs. This problem can be important for aged reactor buildings, radwaste buildings, spent nuclear fuel, research reactors, or accelerators that experience high levels of radiation close to existing thresholds. Mechanical properties of concrete are the most important parameters affected by radiation in NPPs. Compressive strength of concrete is reduced between 80 and 35 \% for radiation fluences between $2\times 10^{19}$ and $2\times 10^{21} n/cm^2$. Tensile strength reduction is more significant than compressive strength. It is reduced between 20 and 80 \% for a radiation fluence equal to $5\times 10^{19}$. We chose three radiation levels $2\times 10^{19}$, $2\times 10^{20}$, $2\times 10^{20}$ based on experimental results as the critical levels of radiation that RC structures in NPPs may be exposed to. Structures susceptible to the problem are mostly RC walls; so the RC panel is chosen as an appropriate representative scale element for the analysis. The effect of radiation on mechanical properties of concrete is considered to analyze degraded scale elements. Material properties, geometry, and loading scenarios of scale elements are selected to be close to actual quantities in existing nuclear power plant. Elements are analyzed under six types of loading combination of shear and axial loading conditions. A nonlinear finite element program, Membrane-2000, based on the Modified Compression Field Theory (MCFT) is used to solve scale elements numerically. Element behaviors are studied considering the factors influence ultimate strength capacity, failure mode, and structural ductility index of members. The results show that ultimate shear capacity of the elements subjected to combinations of shear and tension loading are reduced significantly for highly reinforced elements ($1.35<\rho<1.88$) in $2\times 10^{21} n/cm^2$ radiation. RC panels under shear-biaxial and uniaxial compression also show significant strength capacity reduction in radiation levels $2\times 10^{20} n/cm^2$ and $2\times 10^{21} n/cm^2$, respectively. Failure modes of the elements change from yielding of steel to shear failure by increasing level of degradation for the elements with reinforcement ratio between 0.9 and 1.88. Ductility of the RC panels is reduced significantly in the critical levels of radiation. Ductility of the elements became less than the allowable ductility value by increasing level of radiation.

Vorbeugende QM-Techniken operationalisieren die Funktionen des Qualitätsmanagements (QM) mit dem Ziel einer abgesicherten Produktentstehung. Sie leisten einen wesentlichen Beitrag zur Erhöhung der Produktqualität. Jedoch zeigen Untersuchungen, dass deren Einsatz häufig sehr große Probleme bereitet. Die vorliegende Arbeit untersucht vordergründig die FMEA, QFD und DRBFM. Neben der Beschreibung ihrer Anwendungsbereiche, werden die Vorteile und Schwächen gegenübergestellt. Es gilt, die Schwächen mit Hilfe einer neu entwickelten Methode zu umgehen bzw. zu eliminieren. Die Entwicklung zentraler Schwerpunkte zur Erreichung von Null-Fehlerqualität liefert die Basis für die Erstellung einer Checkliste in Form eines Fragenkataloges. Ziel soll es sein, durch die Systematik des Fragenkataloges und Wahl des Antwortformates Fehlerursachen zu vermeiden.

In this thesis we look at one of the aging mechanisms that may have affected current aged Nuclear Power Plants (NPPs). Irradiation as an age-related degradation mechanism is studied for Reinforced Concrete (RC) in NPPs. This problem can be important for aged reactor buildings, radwaste buildings, spent nuclear fuel, research reactors, or accelerators that experience high levels of radiation close to existing thresholds. Mechanical properties of concrete are the most important parameters affected by radiation in NPPs. Compressive strength of concrete is reduced between 80 and 35 \% for radiation fluences between $2\times 10^{19}$ and $2\times 10^{21} n/cm^2$. Tensile strength reduction is more significant than compressive strength. It is reduced between 20 and 80 \% for a radiation fluence equal to $5\times 10^{19}$. We chose three radiation levels $2\times 10^{19}$, $2\times 10^{20}$, $2\times 10^{20}$ based on experimental results as the critical levels of radiation that RC structures in NPPs may be exposed to. Structures susceptible to the problem are mostly RC walls; so the RC panel is chosen as an appropriate representative scale element for the analysis. The effect of radiation on mechanical properties of concrete is considered to analyze degraded scale elements. Material properties, geometry, and loading scenarios of scale elements are selected to be close to actual quantities in existing nuclear power plant. Elements are analyzed under six types of loading combination of shear and axial loading conditions. A nonlinear finite element program, Membrane-2000, based on the Modified Compression Field Theory (MCFT) is used to solve scale elements numerically. Element behaviors are studied considering the factors influence ultimate strength capacity, failure mode, and structural ductility index of members. The results show that ultimate shear capacity of the elements subjected to combinations of shear and tension loading are reduced significantly for highly reinforced elements ($1.35<\rho<1.88$) in $2\times 10^{21} n/cm^2$ radiation. RC panels under shear-biaxial and uniaxial compression also show significant strength capacity reduction in radiation levels $2\times 10^{20} n/cm^2$ and $2\times 10^{21} n/cm^2$, respectively. Failure modes of the elements change from yielding of steel to shear failure by increasing level of degradation for the elements with reinforcement ratio between 0.9 and 1.88. Ductility of the RC panels is reduced significantly in the critical levels of radiation. Ductility of the elements became less than the allowable ductility value by increasing level of radiation.

Organizations are expected by their shareholders to continually deliver above industry returns on capital invested and to remain competitive in the industry of choice through productivity, safety and quality. The maintenance function is a key area in which competitiveness through efficiencies and world–class performance can be attained by focusing on the prevention and reduction of long and costly equipment repair times. The question is: how can the mean time to repair of equipment already installed in the plant be reduced? To answer the above question correctly and comprehensively, the research explored mixed methods in finding answers. Quantitative methodology using a survey was used for data collection. Observations and interviews were held with maintenance personnel to uncover information that couldn’t have been obtained by means of a survey. The survey was limited to equipment performance measures, human factors, environmental factors, planning, spare parts, maintainability, procedures and training. To test consistency and accuracy of representation of the total population under study, a reliability test was done by using Cronbach’s alpha coefficient. To determine whether there are any differences between groups, an ANOVA test was used. Cohen’s d–value was used to determine practically significant differences between one set of data with another and correlation analysis was used to determine the relationships between the variables. The approach designed and delivered by this research flowed from the existing body of knowledge, case studies and survey findings. The approach adopts some of the elements of the failure mode and effects analysis (FMEA) procedure and differs from other work that has been done by others by taking into account the competency and experience of maintenance personnel and assigning to them factors which are used to compute anew MTTR of the equipment. The cost of implementing the recommended corrective actions for realising the new MTTR is determined and evaluated against an improved equipment availability that will be achieved as a result of the recommended corrective actions assuming that the failure rate of the equipment remains constant. This evaluation step imbedded within the approach is valuable for the maintenance function and management for decision making in ensuring that resources at the organization’s disposal are used productively. Validation and test results of the approach showed that the MTTR of equipment installed in the plant can be reduced. The results also indicated that through the use of the designed approach a regular pattern of repair or replacement times can be followed well in advance and that it is practical, user friendly and it also delivers on its objective of offering a structure for analysis and decision making aimed at reducing the MTTR. Included with this dissertation is feedback information that can be included in a maintenance job card feedback section to capture information about factors that can be improved to lower the MTTR as part of a continuous improvement process. Included also is a spare part development and management procedure that can be used by the maintenance function. Recommendations on training of maintenance personnel on the maintainability of equipment, the FMEA procedure and maintenance procedures are highlighted. Information that flowed from this approach will be valuable for continuous plant performance improvement and during the design, installation and operation stages of a blast furnace. / Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2012.

Organizations are expected by their shareholders to continually deliver above industry returns on capital invested and to remain competitive in the industry of choice through productivity, safety and quality. The maintenance function is a key area in which competitiveness through efficiencies and world–class performance can be attained by focusing on the prevention and reduction of long and costly equipment repair times. The question is: how can the mean time to repair of equipment already installed in the plant be reduced? To answer the above question correctly and comprehensively, the research explored mixed methods in finding answers. Quantitative methodology using a survey was used for data collection. Observations and interviews were held with maintenance personnel to uncover information that couldn’t have been obtained by means of a survey. The survey was limited to equipment performance measures, human factors, environmental factors, planning, spare parts, maintainability, procedures and training. To test consistency and accuracy of representation of the total population under study, a reliability test was done by using Cronbach’s alpha coefficient. To determine whether there are any differences between groups, an ANOVA test was used. Cohen’s d–value was used to determine practically significant differences between one set of data with another and correlation analysis was used to determine the relationships between the variables. The approach designed and delivered by this research flowed from the existing body of knowledge, case studies and survey findings. The approach adopts some of the elements of the failure mode and effects analysis (FMEA) procedure and differs from other work that has been done by others by taking into account the competency and experience of maintenance personnel and assigning to them factors which are used to compute anew MTTR of the equipment. The cost of implementing the recommended corrective actions for realising the new MTTR is determined and evaluated against an improved equipment availability that will be achieved as a result of the recommended corrective actions assuming that the failure rate of the equipment remains constant. This evaluation step imbedded within the approach is valuable for the maintenance function and management for decision making in ensuring that resources at the organization’s disposal are used productively. Validation and test results of the approach showed that the MTTR of equipment installed in the plant can be reduced. The results also indicated that through the use of the designed approach a regular pattern of repair or replacement times can be followed well in advance and that it is practical, user friendly and it also delivers on its objective of offering a structure for analysis and decision making aimed at reducing the MTTR. Included with this dissertation is feedback information that can be included in a maintenance job card feedback section to capture information about factors that can be improved to lower the MTTR as part of a continuous improvement process. Included also is a spare part development and management procedure that can be used by the maintenance function. Recommendations on training of maintenance personnel on the maintainability of equipment, the FMEA procedure and maintenance procedures are highlighted. Information that flowed from this approach will be valuable for continuous plant performance improvement and during the design, installation and operation stages of a blast furnace. / Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2012.

Submitted by Claudia Rocha (claudia.rocha@udesc.br) on 2017-12-11T15:50:46Z No. of bitstreams: 1 PGEF17MA072.pdf: 1540009 bytes, checksum: 0a6a0c91bcb17bc18be105a058020b75 (MD5) / Made available in DSpace on 2017-12-11T15:50:46Z (GMT). No. of bitstreams: 1 PGEF17MA072.pdf: 1540009 bytes, checksum: 0a6a0c91bcb17bc18be105a058020b75 (MD5) Previous issue date: 2017-02-20 / Some organizations in the Brazilian forestry industry do not follow the development pace of other industries, or the adoption rate of management and quality methodologies and tools. As result, the low quality and high instability of processes create a lot of waste in the sector. This is intensified when it happens during the harvesting, one of the activities that most contributes to the production costs of a forestry business. This study aimed to evaluate the predictability of timber harvesting process based on critical points identified in the thinning and harvest operations. For this, research was divided in three stages. The first one was mapping the harvesting process and the elaboration of fluxograms. The second stage was the identification, through interviews, and assessment of critical points using the Failure Mode and Effect Analysis (FMEA) and Pareto chart. The third stage was the evaluation of the process using Statistical Process Control (SPC) through attributes and variable in the main failures. In the interviews conducted with workers, seven critical points were identified: damage to the remaining trees, sorting, stump height, dirt in load, knot on the second log, tree left in the field and safety. The evaluation with Pareto chart showed that 80% of the failures identified during harvest are attributed to three causes: damage to the remaining trees, sorting and stump height. The FMEA analysis showed that the failure with highest risk index was knots on the second log, followed by safety. For evaluation with the SPC, damage to remaining trees, sorting and stump height were selected. In general, control charts showed that the forest harvest process was considered unstable and unpredictable, even though it is within the limits defined by the company / No setor florestal brasileiro, algumas organizações não acompanham o ritmo do desenvolvimento de outros setores e da adoção de ferramentas e metodologias de gestão da qualidade. Em função deste atraso, a baixa qualidade e alta instabilidade dos processos, geram grandes desperdícios nas organizações. O fato se agrava quando ocorre na operação de colheita da madeira, uma das atividades que mais contribui nos custos de produção da empresa florestal. Este trabalho objetivou avaliar o processo de colheita florestal de uma empresa quanto a sua previsibilidade com base nos pontos críticos identificados nas operações de desbaste e corte raso. Para isso, a pesquisa foi dividida em três etapas, a primeira foi o mapeamento do processo de colheita e elaboração de fluxogramas. A segunda etapa foi a identificação, por meio de entrevistas, e avaliação dos pontos críticos utilizando a metodologia Failure Mode and Effect Analysis – FMEA e gráfico de Pareto. A terceira fase foi a avaliação do processo empregando o Controle Estatístico do Processo (CEP) por atributos e variáveis nas principais falhas. Nas entrevistas realizadas com os colaboradores, sete pontos críticos foram apontados: danos às árvores remanescentes, sortimento, altura de toco, sujeira na carga, nó na 2ª tora, árvores deixadas no talhão e segurança. Na avaliação com o gráfico de Pareto, observou-se que cerca de 80% dos problemas identificados na colheita da empresa são atribuídos às três primeiras causas supracitadas. A análise com o FMEA indicou que a falha com maior índice de risco foi o nó na 2ª tora, seguido da segurança. Para a avaliação com o CEP, selecionou-se os pontos críticos: danos às árvores remanescentes, sortimento e altura de toco. De maneira geral, os gráficos de controle indicaram que o processo da colheita florestal, apesar de estar dentro dos limites especificados pela empresa, foi considerado instável e não previsível

The main objective of this master thesis is to design implementation of FMEA analysis in logistics technology Just-in-Sequence at company Robert Bosch in České Budějovice. The operational objective is to define process and product produced by technology Just-in-Sequence. Analyze newly developed technology Just-in-Sequence and compare its advantages over the original method.

The literature indicates that mortar strength has little influence on concrete masonry strength, suggesting that the fresh state properties of the mortar are more relevant than the properties of the hardened mortar, and this point of view is reflected on standards and codes. However, the failure mode of the masonry can be dramatically influenced by the properties of the hardened bedding mortar especially when using a mortar with low compressive strength. In such case, mortar crushing can be the masonry failure mode. This study evaluated the influence of bedding mortar on the failure modes of axially loaded masonry through three distinct approaches. The first approach was a visual analysis that used pictures from a high-definition camera to determine the rupture sequence of masonry prisms. The analysis used pictures from tests of four different prism assemblages. The prisms were two and three blocks high with stack-bond and running-bond configurations and constructed with three types of blocks: concrete blocks and hollow and solid walls ceramic blocks. Two mortar types with different strengths were used to assemble the prisms. The visual analysis indicated that mortar crushing happens and completely changes the masonry failure mode. The second approach evaluated the stress-strain behavior of small thickness axially loaded mortar samples with the objective of capturing changes in the mechanical properties of the mortar. The properties of interest were the Poisson’s ratio, volumetric strain, and strain increments. The evaluation demonstrated that crack propagation near failure results in changes on the mechanical properties of the mortar and that those changes can be used as a measure of the degradation of the mortar. The third approach was the development of a finite element model to represent the axially loaded mortar samples. The model used a phased analysis, which allowed the elastic modulus and Poisson’s ratio of the material to be changed during the loading sequence. The nonlinear model was able to capture the strain changes on the confined mortar. / É comum no meio técnico a ideia de que a resistência da argamassa de assentamento tem pouca influência sobre a resistência da alvenaria, devendo-se valorizar mais o desempenho da argamassa no estado fresco do que no endurecido. Essa forma de pensamento reflete-se, ainda, em alguns textos normativos que regem o projeto de edificações em alvenaria estrutural. No entanto, quando analisado também o modo de ruptura da alvenaria, percebe-se que as propriedades da argamassa no estado endurecido podem alterar completamente a dinâmica de propagação de dano na alvenaria, em especial quando a argamassa de assentamento é de baixa resistência e sujeita a sofrer o esmagamento quando carregada. Este estudo buscou avaliar como a argamassa de assentamento influencia o modo de ruptura da alvenaria estrutural através de três diferentes abordagens. A primeira foi a análise visual, através de sequências quadro a quadro, da ruptura de prismas comprimidos axialmente. Foram avaliadas diferentes geometrias de prismas, com duas ou três fiadas de altura, com ou sem juntas verticais; três tipos de blocos, cerâmicos de paredes vazadas, cerâmicos de paredes maciças e blocos de concreto; e argamassas de alta e baixa resistência. Observou-se nessa abordagem que a argamassa de assentamento pode sofrer esmagamento e alterar o modo de ruptura da alvenaria. A segunda abordagem adotada foi a de avaliar o comportamento tensão-deformação de corpos-de-prova de argamassa com pequena altura sujeitos à compressão confinada, buscando identificar alterações em propriedades como coeficiente de Poisson, variação volumétrica específica e incrementos de deformação. A análise desses resultados demonstrou que a propagação de trincas no material próximo a ruptura altera as propriedades mecânicas e pode ser usada como uma medida do avanço da degradação. Por fim, a terceira abordagem buscou viabilizar um modelo numérico em elementos finitos capaz de considerar a propagação de trinca através da variação do módulo de elasticidade e coeficiente de Poisson. O modelo incremental por fases foi capaz de reproduzir de maneira satisfatória o comportamento de corpos-de-prova de argamassa comprimidos.

A influência de variáveis metodológicas no valor da resistência de união e no padrão de fratura, por ensaio de microcisalhamento, foi verificada em dentina planificada de molares humanos e estudada em quatro diferentes experimentos, nos quais dois sistemas adesivos foram utilizados (Adper Single Bond 2 e XP Bond) e uma resina composta (Filtek Z250). Foram eles: Experimento 1- momento de fotoativação do adesivo: antes ou após o posicionamento das cânulas sobre o substrato dentinário; Experimento 2- tempo de armazenagem: 10min, 24 horas, 48 horas e 7 dias em água destilada a 37oC; Experimento 3- área de secção transversal dos corpos de prova: 0,44mm2, 0,82mm2, 1,98mm2 e 4,44mm2; Experimento 4- momento de fotoativação da resina / remoção da cânula para o ensaio. Os dados obtidos de resistência de união, em MPa, foram tratados por métodos de ANOVA. Os corpos de prova resultantes de todos os experimentos foram observados em microscopia eletrônica de varredura e analisados de forma qualitativa quanto ao modo de fratura. Houve diferença significativa no Experimento 1, sendo que os valores médios de resistência de união foram mais altos quando os adesivos foram fotoativados antes de posicionar as cânulas. Não houve diferença estatisticamente significante para as variáveis tempo de armazenagem e sistema adesivo (Experimento 2), e nem para as variáveis área de secção transversal e sistema adesivo estudadas (Experimento 3). Para o Experimento 4, houve diferença estatisticamente significante para a condição experimental resina fotoativada e remoção da cânula quando previamente realizada à adesão ao substrato e entre os adesivos. Em todos os experimentos o modo de fratura foi predominantemente adesivo/misto. Concluiu-se que algumas variáveis do método são fundamentais para sua padronização, pois com base nos resultados deste estudo elas influenciam os valores médios da resistência de união. / The effect of methodological variables on the microshear bond strength and fracture pattern was assessed in flat human molars dentin in four different experiments using two adhesive systems (Adper Single Bond 2 and XP Bond) and a composite resin (Filtek Z250). The experiments were: 1. Adhesive light activation moment prior or after mold positioning on dentin; 2. Storage period 10 min, 24h, 48h or 7 days in distilled water at 37oC; 3. Mold transversal section area 0.44mm2, 0.82mm2, 1.98mm2 and 4.44mm2; 4. Resin light activation moment with or without mold removal prior to testing. Mean data values (MPa) were subjected to ANOVAs methods. All fractured specimens were qualitatively analyzed in SEM to verify the fracture mode. Regarding Experiment 1 a significative difference was shown for the main factor Adhesive Light Activation Moment; higher bond strength values were achieved with adhesive system ligth activated before mold positioning. No significant differences were found for storage period or section area analyzed on Experiments 2 and 3, respectively. The main factor Resin Light Activation Moment presented differences when the resin composite was previously light activated and mold was removed prior to bonding the resin with the adhesive systems. In all experiments, mode of failure was predominantly adhesive/mixed. The conclusion is that some variables of the method are essential for its standardization, given that they influence the bond strength values.