Thesis (M.S.)--West Virginia University, 1998. / Title from document title page. "December 1998." Document formatted into pages; contains xviii, 153 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 101-105).

Thesis (Ph.D)--Aerospace Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Schrage, Daniel; Committee Member: Loewy, Robert; Committee Member: O'Neill, Gary; Committee Member: Saleh, Joseph; Committee Member: Volovoi, Vitali. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Made available in DSpace on 2014-06-11T19:27:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-06-29Bitstream added on 2014-06-13T19:55:26Z : No. of bitstreams: 1 salani_mr_me_guara.pdf: 1597712 bytes, checksum: 2c6c1a1cfcfebdcea313db2c2ce1efe2 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Com os novos desafios impostos pelas condições cada vez mais severas dos poços de petróleo offshore a necessidade de materiais mais modernos e com melhores propriedades mecânicas tem sido um desafio constante. Neste trabalho foi realizada a caracterização mecânica de tubos fabricados a partir de chapas de aço laminadas a quente, seguido de resfriamento acelerado. Os valores reportados são resultados de testes de laboratório aplicados em corpos de prova retirados do metal de base, de solda e da zona termicamente afetada. A utilização destes aços na fabricação de tubos soldados por processo arco-submerso em dois passes, utilizando arcos múltiplos, tem apresentado resultados de tenacidades confiáveis e superiores aos obtidos a partir de chapas laminadas pelo processo de laminação controlada sem resfriamento acelerado, principalmente em espessuras de 16 mm e superiores. Os requisitos do teste de tenacidade especificados pela norma DNV-OS –F101 aplicados em tubos fabricados de acordo com a norma API 5L, são considerados críticos. A criticidade é função dos valores mínimos a serem obtidos e também da freqüência estabelecida para ser aplicada em cada corrida de aço utilizada na produção de cada item de fabricação. Com isso nota-se uma enorme vantagem do uso dos aços com o processo de resfriamento acelerado, visto que os mesmos tiveram uma melhor homogeneidade nos resultados de limite de escoamento, com um ganho significativo no alongamento e apenas uma pequena redução no limite de resistência. O fato de usarem menores teores de carbono, também favoreceu muito a tenacidade no metal de base e ao longo da ZTA, tendo diferenças extremamente significativas de ganho no teste de impacto e CTOD / The main of this work is the mechanical properties characterization of pipes made from steel plates produced using hot rolling with accelerated cooling. The values reported are laboratory tests results, applied on samples taken from the base metal, weld and heat affected zone. The use of these steel plates in the manufacture of pipes by submerged arc welding process using multiple arcs has shown toughness and elongation results superior to those obtained by using hot rolled steel plates without accelerated cooling, particularly in thicknesses of 16 mm and higher. The toughness test requirements specified by DNV-OS-F101 applied for pipes manufactured aiming offshore application are considered critical. The criticality is function of the minimum values required set the sampling frequency to be applied in every steel heat used in the production of each product. Because of this the use of accelerated cooling process shows a significant advantage, since it provides a better homogeneity in yield strength results, with a significant gain in elongation and only a small reduction in tensile strength. The use of smaller amounts of carbon also greatly fostered toughness in base metal and along HAZ, with significant improvement in the impact test and CTOD. Results due to these enhanced properties the use of steels with accelerated cooling technology is essential in order to face technological challenges imposed by new requirements of submarines pipelines

Cardiovascular diseases which include high blood pressure, coronary heart diseases, heart failure, stroke and peripheral arterial diseases (PAD) affect one out of three American adults or 105 million people. By 2030, the prevalence of cardiovascular disease is estimated to rise 10 percent to more than 40 percent of American adults, or 116 million people. Approximately 8 million people in the United States have PAD, including 12-20% of individuals older than age 60. The main reason of PAD is obstruction of blood flow through lower extremities causing Atherosclerosis. The major artery affected in the lower extremities due to PAD is superficial femoral artery (SFA). Huge numbers of clinical procedures like superficial femoral artery stenting, balloon angioplasty, and percutaneous transluminal intervention are done to treat the disease. Thorough in vitro (biological phenomena made to occur outside the human body) testing of this kind should reduce the risk of in vivo (biological phenomena occurring inside the human body) stent failure and thus lead to increased survivability for patients suffering with cardiovascular diseases and PAD. It has been recognized that a metal subjected to a repetitive or fluctuating stress will fail at a stress much lower than that required to cause failure on a single application of load. As per literature review, typically SFA stents survive no more than 12-18 months until the first fracture is detected in MRI. There was a need of a customized designed device such that it would simulate realistic blood pressure conditions and test the capacity the SFA stents. Commercially, the stents are tested under accelerated cyclic loading conditions at different frequencies for longer cycle periods. In order to demonstrate how stents perform once deployed into an artery, a testing device was required which will simulate arterial blood pressure variations and compressive loads over artery as close as possible to human body. The stent tester documented in this report is capable of subjecting a stent to appropriate physiological loading by deploying it in a simulated vessel and subjecting it to external compression. Loading of this kind was performed at frequencies at 60 Hz and, as such, simulating one million heartbeats of artery pulsation. The primary purpose of this thesis was to successfully design stent tester which cycles artificial fluid simulating blood pressure in arteries and superimposing cyclic compression of stent deployed in an artificial artery. The goal was to obtain a test machine that allows for a cost effective testing of cardiovascular and peripheral stents. Another goal was to externally compress the arterial wall subjected to compressive load with the help of an air controlled mechanical piston attached with load cell assembly. The load cell measures the amount of load applied over the silicone tubing. The design of the device contains two peristaltic pumps which alternate pressure every second by pumping distilled water via plastic tubing. The stent was crimped with the guide wire catheter and deployed in the silicone artery (diameter 11mm O.D) from Dynatek labs. Wall and bridge stents (Medtronic, Schneider Inc.) 10 x 39 mm were used for testing with and without external load. Industrial pressure transducer S-10 (Wika Instruments Corporation) ranging from 0-5 PSI (0-259mmHg) is used to monitor the pressure in the artificial artery. The pressure transducer is connected to the data logger (Omega om320) which serially communicates with computer. The silicon mock test artery was 20cm long so that stents used in various arterial interventions can be tested. The silicon artery has primary advantages over rubber latex artery which are clarity and close resemblance to human artery and durable (ideal for long term durability tests). Preliminary results from literature review show that stent materials, based on its mechanical properties survive for more than one million heartbeats. To demonstrate the capacity of current design a nitinol stent was tested under physiological conditions at 60Hz frequency. A load of 980 grams for 2001 - 5000 heartbeats, 1.98 kg for 5001 - 10000 heartbeats, 4.25 kg for 10001 - 25000 heartbeats and 6.54 kg for 25001 - 50000 heartbeats was applied over the artificial artery. The mechanical piston with load cell assembly was allowed to externally compress the artificial artery. Partial functionality of device was demonstrated by running it for one million heartbeats and 48000 compressive cycles. The device was successfully designed and has the capacity to cycle artificial fluid simulating blood pressure changes in arteries and have demonstrated the ability to test any type of stents. The device was designed efficient which was simulated in an acceptable pressure range as compared to human blood pressure and allow for compression of stent in a cyclic testing pattern. The system was maintained to as close as between diastolic value of 76mmHg to diastolic 122mmHg pressure range. The device was run for about one million heartbeats and it was observed that the NiTi stent successfully survived. The stent was observed visually with a magnifying glass for any cracks or failure at intervals of 500, 1000, 2000, 5000, 10000, 25000, 50000 and one million heartbeats respectively. After running the device for one week at a frequency of 60Hz, no fractures on the stent were visually observed. However, the stent was deformed from the center. Data analysis showed that the mean diastolic and systolic pressure measurements for intervals with no load were found to be statistically significant i.e. in acceptable range. However, the device design lacks stability due to various reasons like device operates in an open looped system, has bubbles in the artificial artery which might be producing varying pressure values and variation in applying load. The device was partly unable to simulate arterial blood pressure changes under no loading conditions. Efforts are being made to improve the design of the device to make it realistic simulation of variation in arterial blood pressure for long term durable testing of the stents.

Tidal Energy is one of the growing renewable energy technologies that is aimed at tackling global energy challenges. The Horizontal Axis Tidal Turbine (HATT) is an in-stream Tidal Energy Converter (TEC) which extracts kinetic energy from tidal flows. These tidal turbines face many reliability challenges due to their complexity, harsh operating environment and low accessibility. One of the component contributing significantly to the reliability of a TEC is the bearing supporting the rotating shaft within the nacelle. The reliability assessment of this component is essential during the design process and before their eventual deployments. This work is describes shaft bearing reliability assessment procedures. In recent years, the Offshore Renewable Energy (ORE) Catapult’s National Renewable Energy Centre has developed a dedicated multi axis test facility for full scale testing of tidal turbine nacelles and components (i.e. Nautilus). This work presents a methodology for testing tidal turbine shaft bearings in a representative manner in the full scale nacelle test rig, Nautilus. Two aspects are considered, namely the damage assessment and the damage replication in an accelerated manner. The damage assessment process considers the global loading on the shaft bearing and a Rigid Dynamics (RD) model has been applied to identify the local bearing loads. Local loads are converted to stress enabling the identification of stress-life relationship and bearing damage. The damage replication process is aimed to evaluate the 20 year damage and the Acceleration by Phase-shift (AbP) method has been developed to accelerate the cumulative damage. The AbP method enables the assessment of performance characteristics of shaft bearings in a laboratory environment, reducing failure rates, validate performance in a cost effective manner by reduced testing times. Within this work, novel processes for shaft bearing reliability assessments and demonstration are suggested and it concludes with the presentation of a recommended test plan for carrying out accelerated tests on a full scale bearing.

Submitted by Alexandre Pinho dos Santos Souza null (alexandre.pinho510@gmail.com) on 2016-10-20T18:04:06Z No. of bitstreams: 1 Thesis_Final_Cut.pdf: 1024756 bytes, checksum: 359153fd460f589a2a0359f05ca87b3d (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-10-26T18:50:11Z (GMT) No. of bitstreams: 1 souza_aps_dr_ilha.pdf: 1024756 bytes, checksum: 359153fd460f589a2a0359f05ca87b3d (MD5) / Made available in DSpace on 2016-10-26T18:50:11Z (GMT). No. of bitstreams: 1 souza_aps_dr_ilha.pdf: 1024756 bytes, checksum: 359153fd460f589a2a0359f05ca87b3d (MD5) Previous issue date: 2016-08-31 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Dentro da cosmologia, o modelo ΛCDM é considerado, pela comunidade científica, como aquele que melhor descreve o universo. Todavia, tal modelo sofre de alguns males que ainda precisam ser sanados. Entre eles se destacam o problema da constante cosmológica e o problema da coincidência cósmica. Atribui-se, neste modelo, a expansão acelerada do universo a um ente de origem desconhecida, chamado de energia escura. Parte da solução destes problemas está intimamente ligado em saber a natureza da energia escura. Por outro lado, devido a propriedades intrínsecas do espinor ELKO, faz-se possível atribuir ao mesmo o papel de energia escura. Deste modo, constrói-se aplicações cosmológicas do ELKO que possibilitem a resolução completa ou parcial dos problemas mencionados. Estas aplicações consistem basicamente na análise do sistemas de equações de Friedmann oriundas da anexação do Lagrangeano do ELKO na ação de Einstein-Hilbert. Dentro desse sistema se insere a mão o possível decaimento do ELKO em outros elementos que constituem o universo. Com este se alivia o problema da coincidência cósmica, enquanto que se confirma que o ELKO pode figurar como energia escura por meio dos resultados do sistema geral. Ao fim do trabalho se observa uma outra aplicação do ELKO, desta vez no cenário cosmológico de Einstein-Cartan. Neste se mostra que o modelo cosmológico que contém o ELKO como energia escura, e na presença de termo de torção, é análogo ao modelo cosmológico Λ(t). / In cosmology the ΛCDM model is the most accepted way to describe the universe. However, this model suffers some problems that have to be solved. Namely there are two of them which are attached in this thesis. They are the cosmic coincidence and the cosmological constant problem. Due this model it is possible to relate the universe’s accelerated expansion to dark energy. Part of solving these problems pass through knowing the origin of dark energy. It is known that the spinor ELKO has some fundamental properties that able scientists to connect them to dark universe elements, e.g. dark energy. So, some applications of ELKO in cosmology have been made in order to explore this possibility and to solve those fundamental problems. These application are based on analyzing ELKO in dynamical systems formed by Friedmann’s equations, where these equations comes from putting ELKO’s Lagranian in the Einstein-Hilbert action. In this system it is inserted a term of decaying. With such term it is possible to alleviate cosmic coincidence problem. On the other hand it is also possible to justify ELKO as dark energy as wished at the beginning. Last but not least, another application of ELKO in cosmology has been investigated. For such case is was shown that, with some considerations and approximations, ELKO in cosmology allied with Einstein-Cartan formalism can mimic Λ(t) cosmology results.

Um problema na indústria coureira é a deterioração de peles e couros devido ao desenvolvimento de microrganismos no processamento do couro. As peles e os couros contêm nutrientes adequados para o crescimento de microrganismos, como carboidratos, gorduras e proteínas, além das condições ambientais, alta umidade, temperatura de armazenagem e pH favoráveis. Alguns gêneros de bactérias e fungos sintetizam importantes substâncias deste substrato, causando modificações prejudiciais na superfície do couro e nas propriedades físico-mecânicas, deixando manchas pigmentadas de difícil remoção, afetando a qualidade do produto final e causando perda de valor comercial. Desta forma, surge a necessidade de desenvolver estratégias de controle dos microrganismos de modo a reduzir ou eliminar este problema. Para tanto, recorre-se comumente à utilização de microbicidas. No passado, a ação esperada dos agentes antimicrobianos era principalmente de fornecer uma proteção eficaz, mas em anos mais recentes, a preocupação com a sua toxicidade e com potenciais riscos ecológicos tornou-se também importante. Nos dias atuais uma grande preocupação mundial é o cuidado com a preservação do meio ambiente. Devido a isto, várias pesquisas estão voltadas para o desenvolvimento de novas tecnologias limpas e renováveis como também a otimização de processos. Tendo em vista a melhoria de processos no que diz respeito ao uso de microbicidas adicionados em peles e couros, para prevenir a contaminação dos mesmos por microrganismos, esta dissertação centrou-se na avaliação do desempenho de microbicidas comerciais convencionalmente utilizados na indústria do couro sendo eles 2-(tiocianometiltio) benzotiazole (TCMTB), isotiazolina, dispersão oleosa de 2-n-octil-4-isotiazolin-3-ona + carbendazim (OIT+BMC/óleo), dispersão aquosa de 2-n-octil-4-isotiazolin-3-ona + carbendazim (OIT+BMC/água), 2-n-octil-4-isotiazolin-3-ona (OIT) e para-cloro-meta-cresol (PCMC) contra as espécies de bactérias Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa e Streptomyces sp. e as espécies de fungos Aspergillus niger, Aspergillus flavus, Penicillium herguei e Penicillium chrysogenum. Os microbicidas foram aplicados nas etapas de remolho, píquel, curtimento de couro com cromo e curtimento/engraxe com tanino vegetal. Os efeitos antimicrobianos dos microbicidas foram avaliados através de ensaios microbiológicos acelerados de plaqueamento e de acondicionamento em câmara tropical e testes de biodeterioração no solo, seguidos de análises visual, Microscopia eletrônica de varredura e ensaio de tração. Também foi testada a sorção e wash-out dos microbicidas em couros wet-blue. Outro teste feito nos próprios microbicidas foi o de concentração inibitória mínima (MIC). Os resultados demonstraram baixa capacidade antibacteriana e antifúngica dos microbicidas selecionados quando aplicados no processo de remolho contra o ataque das bactérias Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Streptomyces sp. e no processo de engraxe para o couro curtido com tanino vegetal contra o ataque dos fungos Aspergillus niger, Aspergillus flavus. Dois dos microbicidas estudados, TCMTB e OIT+BMC/água aplicados no couro wet-blue, revelaram elevada capacidade antifúngica contra os quatro diferentes fungos testados. Dos microbicidas submetidos ao teste de absortividade e wash-out, o microbicida à base de TCMTB apresentou alta e rápida absortividade pelo couro wet-blue, além de possuir resistência à lavagem. / A problem in the leather industry is the deterioration of leather skins due to the development of microorganisms, in the processing of leather. The skin and leather containing nutrients suitable for the growth of microorganisms such as carbohydrates, fats and proteins , as well as environmental conditions, high humidity, storage temperature and pH favorable. Some genera of bacteria and fungi synthesize important ingredients of this substrate, causing harmful changes in the surface of the leather and the physical and mechanical properties, leaving pigmented spots are difficult to remove, affecting the quality of the final product and loss of commercial value. Thus, there arises the need to develop strategies for control of microorganisms in order to reduce or eliminate this problem, therefore, appeal commonly the use of microbicides. In the past, the expected action of antimicrobial agents was mainly to provide effective protection, but in more recent years, concerns about the toxicity and potential ecological risks has also become important. Nowadays a major global concern is the careful preservation of the environment, due to this many researches are focused on the development of new clean and renewable technologies as well as process optimization. In view of the improvement of processes in respect to the use of microbicides added to hides and skins to prevent contamination thereof by microorganisms , this work has focused on the evaluation of the performance of commercial microbicides conventionally used in the leather industry, 2-metiltiocianato benzothiazole (TCMTB) isothiazoline, oily dispersion of 2-n-octil-4-isotiazolin-3-ona + carbendazim (OIT+BMC/oil), water dispersion of 2-n-octil-4-isotiazolin-3-ona + carbendazim (OIT+BMC/water), 2-n-octil-4-isotiazolin-3-ona (OIT) and para-chloro-meta-cresol (PCMC), against the bacterial species Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosas and Streptomyces sp. e species of fungi Aspergillus niger, Aspergillus flavus, and Penicillium herguei Penicillium chrysogenum, compared with the control. Microbicides were applied in steps of soaking, pickling, chrome tanning and grease/tanning with vegetable tannin. The antimicrobial effects of microbicides made for these applications were evaluated by accelerated plating microbiological testing and tropical chamber rain and biodegradation tests on the ground, followed by analysis (visual , SEM and tensile test) . Also was tested the absorptivity and wash-out of microbicides in wet-blue leather. Another test done on their own microbicides was the minimal inhibitory concentration (MIC). The results showed low capacity antibacterial and antifungal activities of selected microbicides when applied in the process of soaking the attack of the bacteria Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Streptomyces. sp. e in the process of grease for leather vegetable tannin against fungal attack Aspergillus niger, Aspergillus flavus. Two of microbicides studied TCMTB and OIT + BMC/water applied in wet-blue leather, high capacity antifungal against revealed four different fungi tested. For microbicides tested for absorbency and wash-out the microbicide based TCMTB showed high and rapid absorbency by wet-blue leather also has resistance to washing.

abstract: Accelerated life testing (ALT) is the process of subjecting a product to stress conditions (temperatures, voltage, pressure etc.) in excess of its normal operating levels to accelerate failures. Product failure typically results from multiple stresses acting on it simultaneously. Multi-stress factor ALTs are challenging as they increase the number of experiments due to the stress factor-level combinations resulting from the increased number of factors. Chapter 2 provides an approach for designing ALT plans with multiple stresses utilizing Latin hypercube designs that reduces the simulation cost without loss of statistical efficiency. A comparison to full grid and large-sample approximation methods illustrates the approach computational cost gain and flexibility in determining optimal stress settings with less assumptions and more intuitive unit allocations. Implicit in the design criteria of current ALT designs is the assumption that the form of the acceleration model is correct. This is unrealistic assumption in many real-world problems. Chapter 3 provides an approach for ALT optimum design for model discrimination. We utilize the Hellinger distance measure between predictive distributions. The optimal ALT plan at three stress levels was determined and its performance was compared to good compromise plan, best traditional plan and well-known 4:2:1 compromise test plans. In the case of linear versus quadratic ALT models, the proposed method increased the test plan's ability to distinguish among competing models and provided better guidance as to which model is appropriate for the experiment. Chapter 4 extends the approach of Chapter 3 to ALT sequential model discrimination. An initial experiment is conducted to provide maximum possible information with respect to model discrimination. The follow-on experiment is planned by leveraging the most current information to allow for Bayesian model comparison through posterior model probability ratios. Results showed that performance of plan is adversely impacted by the amount of censoring in the data, in the case of linear vs. quadratic model form at three levels of constant stress, sequential testing can improve model recovery rate by approximately 8% when data is complete, but no apparent advantage in adopting sequential testing was found in the case of right-censored data when censoring is in excess of a certain amount. / Dissertation/Thesis / Doctoral Dissertation Industrial Engineering 2014

O objetivo deste estudo é desenvolver um método para avaliar a confiabilidade de sistemas eletrônicos complexos. A análise proposta baseia-se na aplicação de ensaios de confiabilidade e de normas técnicas, bem como modelos matemáticos para estimação da vida operacional. Os ensaios de confiabilidade executados nesse estudo simulam condições operacionais mais severas que as usualmente enfrentadas pelo sistema, a fim de reduzir o tempo de execução dos ensaios. Ao longo destes, foram coletados os tempos até a falha de diversas amostras do sistema, os quais são submetidas a diferentes condições de operação. O planejamento das variáveis que aceleram os principais modos de falha de componentes eletrônicos e os perfis de solicitação empregados também são discutidos, sendo consideradas as mais importantes a temperatura e a umidade. Através da aplicação de modelos matemáticos para predição da vida nas condições normais de operação, dadas as ocorrências de falhas nas condições aceleradas, a confiabilidade e o tempo médio até a falha são determinados para a central telefônica estudada, tomada como exemplo na aplicação do método. Adicionalmente aos ensaios são desenvolvidas estimativas da confiabilidade da central telefônica através da norma militar US MIL-HDBK-217 F (1991). Os resultados destas estimativas são utilizados para comparação e confirmação dos resultados obtidos através dos ensaios. Destaca-se que os métodos descritos neste texto não são restritos a aplicação em centrais telefônicas analógicas, mas podem ser empregados a uma grande família de equipamentos eletrônicos de complexidade tecnológica semelhante. / This research aims to develop a method to evaluate the reliability of complex electronic systems. The analysis proposed is based on application of reliability laboratory tests, technical standards and mathematical models to estimate the system operational life. Reliability tests proposed simulate harder operational conditions than those usually faced by the system, aiming to reduce the time of execution. During the tests, time to failure of several samples are collected. Those samples are submitted to different environmental conditions. Selection of variables that accelerate the main failure modes of electronic components and the load profiles used are also analyzed, considering humidity and temperature the most important variables for failure acceleration. The proposed model is used to estimate the reliability and the mean time to failure of an analog PABX, those values being generated by the application of mathematical models for life prediction in the usage operation condition, given the accelerated reliability estimate. Additionally to the tests, a reliability estimation of the PABX central is done using US MIL-HDBK-217 F (1991). Results are used to compare and to validate the reliability value evaluated through the accelerated tests. It is important to emphasize that the application of the methods described in this present text is not restricted to analog PABX systems, being applied to a wide range of electronic equipments with similar technological complexity.

Um problema na indústria coureira é a deterioração de peles e couros devido ao desenvolvimento de microrganismos no processamento do couro. As peles e os couros contêm nutrientes adequados para o crescimento de microrganismos, como carboidratos, gorduras e proteínas, além das condições ambientais, alta umidade, temperatura de armazenagem e pH favoráveis. Alguns gêneros de bactérias e fungos sintetizam importantes substâncias deste substrato, causando modificações prejudiciais na superfície do couro e nas propriedades físico-mecânicas, deixando manchas pigmentadas de difícil remoção, afetando a qualidade do produto final e causando perda de valor comercial. Desta forma, surge a necessidade de desenvolver estratégias de controle dos microrganismos de modo a reduzir ou eliminar este problema. Para tanto, recorre-se comumente à utilização de microbicidas. No passado, a ação esperada dos agentes antimicrobianos era principalmente de fornecer uma proteção eficaz, mas em anos mais recentes, a preocupação com a sua toxicidade e com potenciais riscos ecológicos tornou-se também importante. Nos dias atuais uma grande preocupação mundial é o cuidado com a preservação do meio ambiente. Devido a isto, várias pesquisas estão voltadas para o desenvolvimento de novas tecnologias limpas e renováveis como também a otimização de processos. Tendo em vista a melhoria de processos no que diz respeito ao uso de microbicidas adicionados em peles e couros, para prevenir a contaminação dos mesmos por microrganismos, esta dissertação centrou-se na avaliação do desempenho de microbicidas comerciais convencionalmente utilizados na indústria do couro sendo eles 2-(tiocianometiltio) benzotiazole (TCMTB), isotiazolina, dispersão oleosa de 2-n-octil-4-isotiazolin-3-ona + carbendazim (OIT+BMC/óleo), dispersão aquosa de 2-n-octil-4-isotiazolin-3-ona + carbendazim (OIT+BMC/água), 2-n-octil-4-isotiazolin-3-ona (OIT) e para-cloro-meta-cresol (PCMC) contra as espécies de bactérias Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa e Streptomyces sp. e as espécies de fungos Aspergillus niger, Aspergillus flavus, Penicillium herguei e Penicillium chrysogenum. Os microbicidas foram aplicados nas etapas de remolho, píquel, curtimento de couro com cromo e curtimento/engraxe com tanino vegetal. Os efeitos antimicrobianos dos microbicidas foram avaliados através de ensaios microbiológicos acelerados de plaqueamento e de acondicionamento em câmara tropical e testes de biodeterioração no solo, seguidos de análises visual, Microscopia eletrônica de varredura e ensaio de tração. Também foi testada a sorção e wash-out dos microbicidas em couros wet-blue. Outro teste feito nos próprios microbicidas foi o de concentração inibitória mínima (MIC). Os resultados demonstraram baixa capacidade antibacteriana e antifúngica dos microbicidas selecionados quando aplicados no processo de remolho contra o ataque das bactérias Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Streptomyces sp. e no processo de engraxe para o couro curtido com tanino vegetal contra o ataque dos fungos Aspergillus niger, Aspergillus flavus. Dois dos microbicidas estudados, TCMTB e OIT+BMC/água aplicados no couro wet-blue, revelaram elevada capacidade antifúngica contra os quatro diferentes fungos testados. Dos microbicidas submetidos ao teste de absortividade e wash-out, o microbicida à base de TCMTB apresentou alta e rápida absortividade pelo couro wet-blue, além de possuir resistência à lavagem. / A problem in the leather industry is the deterioration of leather skins due to the development of microorganisms, in the processing of leather. The skin and leather containing nutrients suitable for the growth of microorganisms such as carbohydrates, fats and proteins , as well as environmental conditions, high humidity, storage temperature and pH favorable. Some genera of bacteria and fungi synthesize important ingredients of this substrate, causing harmful changes in the surface of the leather and the physical and mechanical properties, leaving pigmented spots are difficult to remove, affecting the quality of the final product and loss of commercial value. Thus, there arises the need to develop strategies for control of microorganisms in order to reduce or eliminate this problem, therefore, appeal commonly the use of microbicides. In the past, the expected action of antimicrobial agents was mainly to provide effective protection, but in more recent years, concerns about the toxicity and potential ecological risks has also become important. Nowadays a major global concern is the careful preservation of the environment, due to this many researches are focused on the development of new clean and renewable technologies as well as process optimization. In view of the improvement of processes in respect to the use of microbicides added to hides and skins to prevent contamination thereof by microorganisms , this work has focused on the evaluation of the performance of commercial microbicides conventionally used in the leather industry, 2-metiltiocianato benzothiazole (TCMTB) isothiazoline, oily dispersion of 2-n-octil-4-isotiazolin-3-ona + carbendazim (OIT+BMC/oil), water dispersion of 2-n-octil-4-isotiazolin-3-ona + carbendazim (OIT+BMC/water), 2-n-octil-4-isotiazolin-3-ona (OIT) and para-chloro-meta-cresol (PCMC), against the bacterial species Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosas and Streptomyces sp. e species of fungi Aspergillus niger, Aspergillus flavus, and Penicillium herguei Penicillium chrysogenum, compared with the control. Microbicides were applied in steps of soaking, pickling, chrome tanning and grease/tanning with vegetable tannin. The antimicrobial effects of microbicides made for these applications were evaluated by accelerated plating microbiological testing and tropical chamber rain and biodegradation tests on the ground, followed by analysis (visual , SEM and tensile test) . Also was tested the absorptivity and wash-out of microbicides in wet-blue leather. Another test done on their own microbicides was the minimal inhibitory concentration (MIC). The results showed low capacity antibacterial and antifungal activities of selected microbicides when applied in the process of soaking the attack of the bacteria Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Streptomyces. sp. e in the process of grease for leather vegetable tannin against fungal attack Aspergillus niger, Aspergillus flavus. Two of microbicides studied TCMTB and OIT + BMC/water applied in wet-blue leather, high capacity antifungal against revealed four different fungi tested. For microbicides tested for absorbency and wash-out the microbicide based TCMTB showed high and rapid absorbency by wet-blue leather also has resistance to washing.