Orientador: Juliany Gomes Quitzan / Resumo: Devido à alta incidência de cirurgias gastrointestinais nas diferentes espécies, incluindo o homem, diversas técnicas e materiais são continuamente desenvolvidos visando otimizar os procedimentos e diminuir as principais complicações observadas, dentre elas deiscência, extravasamento de conteúdo, aderências, peritonite e sepse. O fio farpado é uma recente opção de sutura, que beneficia especialmente as modalidades cirúrgicas laparoscópicas ou videoassistidas, pois a dispensabilidade de nós facilita a sutura e diminui o tempo cirúrgico. Ainda, as farpas ao redor do fio permitem melhor adesão ao tecido e distribuição uniforme da tensão. Com o objetivo de comparar três tipos suturas realizadas com o fios absorvíveis monofilamentares, farpado ou liso, em relação ao tempo de sutura, escore de aderência, resistência ao teste de ruptura e avaliação histológica, foram executadas enterorrafias em jejuno de 12 suínos (sutura farpada, sutura contínua e isolada simples). Os animais foram randomizados em três grupos (n=4), referindo-se aos dias pós-operatórios para coleta das amostras (G3, G10 e G21). Houve diferença entre as médias dos tempos de execução, quando comparadas as suturas farpada (274,33±70,48) e contínua (350,41±87,25), em relação à isolada (469,00±109,72). Comparando-se os três padrões, nos diferentes momentos, os escores de aderência e as pressões aferidas no teste de ruptura não apresentaram diferença significativa, assim como a análise histopatológica, onde não foi obser... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Due to the high incidence of gastrointestinal surgeries in many species including humans, several techniques and materials have been continuously investigated to improving the procedures towards to avoid the most common complications, including dehiscence, leakage of contents, adhesions, peritonitis and sepsis. Barbed suture has recently come under focus for laparoscopic or video-assisted procedures, once it is a knotless suture and makes the suturing time shorter. In addition, the barbs around the suture promotes better adhesion to the tissue and uniform distribution of the tension. To compare three types of sutures performed with monofilament conventional or barbed suture, both absorbable, in relation to suture time, adhesion score, burst pressure and histology, jejunal sutures were performed in 12 pigs (barbed suture, continuous suture and simple interrupted). The groups (n = 4) were randomized, referring to the postoperative days for final evaluation (G3, G10 and G21). There was a difference on suturing time, when compared barbed (274.33 ± 70.48) and continuous (350.41 ± 87.25) to the interrupted pattern (469.00 ± 109.72). Among the 3 techniques at G3, 10 or 21, adherence scores and bursting pressure were not significantly different as well as histology evaluation, since no difference could be detected, in the grade of inflammation, fibrosis, tissue alignment, necrosis and neovascularization, at the suturing sites. No complications due to suture failures were observed. Ba... (Complete abstract click electronic access below) / Mestre

The aim of this study was to investigate the effects of resin and fiber on the abrasion, impact and internal pressure resistances of fiber reinforced plastic composite pipes produced by continuous filament winding method. For this study, pipe samples were produced with different combinations of resin type, fiber type, fiber amount and fiber length. All the samples were tested in accordance with the related ISO (International Organization for Standardization), DIN (German Standardization Institution) and BSI (British Standards Institution) standards. Three types of resins were used as ortophthalic, isophthalic and vinylester / two types of fibers were used as E-glass and ECR-glass and one type of GLASSFLAKES was used as C-glass. It was observed that the type of resin did not have any significant effect on burst pressure. However, the vinylester resin had a considerable positive effect on the abrasion and impact resistances. Moreover, it was observed that the type of fiber did not have any significant effect on impact and internal pressure resistances, but the use of C-glass GLASSFLAKES resulted in a positive effect on the abrasion resistance. Additionally, it was found that the increase in the amount of glass fiber resulted in increase of burst pressure, impact and abrasion resistances. Finally, it was observed that the length of glass fiber did not have any significant effect on abrasion resistance, but the decrease in fiber length resulted in a higher internal pressure and impact resistances.

The aim of this study is to determine the mechanical characteristics of the filament wound composite tubes working under internal pressure loads, generating data for further investigation with a view of estimating the remaining life cycle of the tubes during service. Data is generated experimentally by measuring the mechanical behavior like strains in hoop direction, maximum hoop stresses that are formed during internal pressure loading. Results have been used to identify and generate the necessary data to be adopted in the design applications. In order to determine these parameters, internal pressure tests are done on the filament wound composite tube specimens according to ASTM D 1599-99 standard. The test tubes are manufactured by wet filament winding method, employing two different fiber types, two different fiber tension settings and five different winding angle configurations. The internal pressure test results of these specimens are studied in order to determine the mechanical characteristics, and the effects of the production variables on the behavior of the tubes. Pressure tests revealed that the carbon fiber reinforced composite tubes exhibited a better burst performance compared to the glass fiber reinforced tubes, and the maximum burst performance is achieved at a winding angle configuration of [&plusmn / 54&deg / ]3[90&deg / ]1. In addition, the tension setting is found not to have a significant effect on the burst performance. The burst pressure data and the final failure modes are compared with the results of the ASME Boiler and Pressure Vessel Code laminate analysis, and it was observed that there is a good agreement between the laminate analysis results and the experimental data. The stress &ndash / strain behavior in hoop direction are also studied and hoop elastic constants are determined for the tubes.

Uma grande variedade de modelos é utilizada para estimar a pressão de ruptura de dutos contendo defeitos de corrosão. O presente trabalho tem como objetivo estudar a precisão dos modelos mais comuns e avaliar a pressão de ruptura de dutos submetidos à corrosão. Os modelos avaliados são: ASME B31G, ASME B31G modificado, DNV RP F101 e PCORRC. O estudo é baseado em mais de 400 resultados de ensaios de ruptura em dutos corroídos, todos coletados da literatura. A base de dados contem defeitos de corrosão reais e artificiais. Uma análise estatística foi realizada para a variável erro de modelo. Uma análise de regressão não-linear foi realizada para investigar os efeitos da variável erro de modelo, das variáveis mais relevantes, como profundidade e comprimento do defeito, e tensão de ruptura do aço. Uma análise de confiabilidade foi realizada a partir das estatísticas obtidas da variável erro de modelo, sendo estimado o índice de confiabilidade e a probabilidade de falha do duto com defeitos de corrosão, através do método iterativo de primeira ordem, denominado FORM (First Order Reliability Method). Nesta análise avaliou-se a evolução da probabilidade de falha com o aumento da profundidade do defeito, bem como foram identificadas as variáveis aleatórias mais importantes na falha do duto. O estudo pode ajudar aos operadores a eleger qual modelo utilizar em análises de risco, proporcionando mais segurança às operações dutoviárias. / A variety of models exist to estimate burst pressures of pipelines containing corrosion defects. The objective of this work is to study the accuracy of some of the most popular empirical burst pressure models. The study addresses the models: ASME B31G, ASME B31G Modified, DNV RP-F101 and PCORRC. The investigation is based on over 400 burst test results, all collected from the literature, containing both real and artificial corrosion defects. A statistical analysis is performed for assessing the accuracy of semi-empirical models by using a model error variable. A non-linear regression analysis is performed to identify the influence, on model errors, of the most relevant variables, such as defect depth and length and steels rupture tension. A reliability analysis was carried out, using model error statistics developed herein, in order to evaluate reliability index and probability of failure of pipelines containing corrosion defects, through the iterative first order reliability method, or FORM - First Order Reliability Method. The evolution of failure probabilities, with increasing defect depth, was investigated. The most relevant random variables were identified. The study can help operators choose a proper empirical model to use in their risk analysis, leading to greater safety in pipeline operations.

Lung diseases, cancers, and trauma can result in injury to the connective tissue lining the lung, i.e., the pleura. Pleural injuries lead to pneumothoraxes or pleural effusions, i.e., air or fluid leaking out of the lung respectively, and potential lung collapse - an immediately life threatening condition. While several bioengineered soft tissue sealants exist on the market, there is only one sealant FDA-approved for use in pulmonary surgery. In addition, very limited techniques are presented in the literature for characterizing the burst properties of hydrogel tissue sealants. For my thesis, I proposed to develop a protocol for characterizing the burst properties of hydrogel sealants using a novel burst pressure test chamber. I further proposed a novel combination of oxidation and methacrylation reactions of alginate for tissue sealant applications, with a particular focus on developing a pulmonary sealant. The proposed research objectives are: 1) To develop protocol for testing hydrogel sealants for soft tissue applications; 2) To verify alginate as a potential for tissue sealant applications; and 3) To optimize an alginate hydrogel sealant and perform ex vivo analysis for a pleural sealant application. Alginate materials with varying degrees of oxidation and methacrylation were synthesized and characterized. Oscillatory rheometry was used to characterize material properties such as viscosity, hydrogel gelation kinetics, and complex moduli. Burst pressure measurements properties and failure mechanisms, i.e. delamination or material failure, were collected for a liquid and dry-state application. Preliminary ex vivo mouse lung model testing demonstrated that methacrylated alginate hydrogels are able to withstand physiological pressures associated with breathing, and failure occurs within the hydrogel for adhesive alginate-based tissue sealants.

[pt] Neste trabalho avalia-se uma metodología de cálculo para a previsão da pressão de falha de um duto que contem colônias de corrosão, chamada Método das Linhas Ortogonais de Ruptura (MLOR). As colônias de corrosão são representadas por defeitos retangulares, localizados na superfície externa do duto. O objetivo do MLOR é ser mais exato que os métodos semi-empíricos da ASME e DNV utilizados até o momento. O MLOR também tem como objetivo evitar resultados não conservativos que podem ser obtidos com o método Mixed Type of Interacting (MTI). O MLOR apresenta outra forma de avaliar a perda de espessura efetiva de um grupo de defeitos. Ele propõe que se tracem linhas representativas do caminho pelo qual a ruptura do duto tem maior possibilidade de ocorrer, usando linhas paralelas às direções longitudinal e circunferencial do duto. Estas linhas são chamadas de linhas ortogonais de ruptura (LOR). Também considera-se o emprego de um fator de resistência circunferencial f no cálculo de uma espessura efetiva para a colônia. Este fator multiplica somente os comprimentos das LOR que estiverem na direção circunferencial do duto. O material íntegro existente entre dois defeitos é considerado na resistência à ruptura por meio da seleção de um caminho crítico que une os defeitos retangulares e que usa as direções longitudinal e circunferencial. Para a avaliação do MLOR usou-se pressões de falha para tubos com colônias de defeitos determinados experimentalmente e já publicados, além de simulações numéricas feitas pelo método dos elementos finitos (MEF), utilizando-se para isto o software comercial ANSYS. Por fim, neste trabalho concluiu-se que o MLOR apresentou bons resultados (máximos erro médio igual a -0.14 por cento e desvio padrão do erro igual a 3.53 por cento) quando comparados com os resultados experimentais e numéricos, já publicados, de nove corpos de provas em tamanho real. / [en] This dissertation comprises the evaluation of a new calculation methodology developed to predict the burst pressure of pipeline segments containing corrosion colonies. The new methodology is called Method of Orthogonal Lines Rupture (MLOR). The corrosion colonies are represented by rectangular defects, located on the outer surface of the pipeline segment. The objective of MLOR is to determine more accurate results than those calculated by the semi-empirical methods of ASME and DNV. The MLOR has also the objective of avoiding non-conservative results that can be obtained with the Mixed Type Interacting method (MTI). The MLOR presents a new way to assess the loss of effective thickness of a group of defects. It proposes the drawing of lines parallel to the longitudinal and circumferential directions that intend to represent the path by which the rupture of the pipeline is more likely to occur. These lines are called Orthogonal Lines of Rupture (LOR). It is also considered the employment of a strength circumferential factor f in the calculation of the effective thickness of the colony. This factor multiplies only the lengths of the LOR which are associated with the circumferential direction of the pipeline. Using that, the intact material existing between two defects is considered in the calculation of the rupture resistance. The critical path connects the rectangular defects using lines parallel to the longitudinal and circumferential directions. The evaluation of the MLOR was accomplished by comparing its burst pressure calculations with already published results determined for nine full scale tests carried out with specimens that contained specially designed and constructed colonies of defects. The comparisons encompassed those experimentally published test results and also results determined by numerical simulations that employed the finite element method (ANSYS commercial software). Finally, the dissertation concludes that the MLOR showed good results (maximum average error equal to -0.14 percent and standard deviation of the error equal to 3.53 percent) compared with experimental and numerical results.

Este estudo estende a abordagem micromecânica baseada em células computacionais e a abordagem baseada em deformação utilizando o critério de CTOA para descrever extensão dúctil de trincas longitudinais em dutos de aços de elevada tenacidade sob alta pressão. Ensaios laboratoriais realizados em aços API 5L X60 e X70 utilizando corpos-de-prova padronizados de fratura com trinca profunda, produzem os resultados necessários para medir as curvas de resistência à propagação de trincas e calibrar os parâmetros dos modelos de Gurson e CTOA para estes materiais. O foco central deste trabalho é a aplicação da metodologia de células computacionais e o critério de CTOA para prever as pressões de colapso medidas experimentalmente em dutos de paredes finas contendo trincas longitudinais. O programa experimental inclui espécimes pré-trincados com 508 mm (20") e 219 mm (8 5/8") com diferentes profundidades de trincas. Foram conduzidas análises de elementos finitos, sob estado plano de deformações e no contexto 3D pleno utilizando modelos detalhados dos dutos para descrever a extensão de trinca com o incremento de pressão. As simulações numéricas demonstram a eficiência e limitações de ambas as abordagens para descrever a resposta de crescimento de dúctil e prever a pressão de colapso para os dutos testados. Enquanto o critério de CTOA ainda parece ter limitada aplicabilidade para prever o comportamento dúctil dos dutos, a previsão da resposta dúctil do dutos pré-trincados utilizando o modelo de células computacionais mostrou boa concordância com as pressões de colapso medidas experimentalmente. / This study extends a micromechanics approach based upon the computational cell methodology incorporating the Gurson model and a deformation-based approach using the CTOA criterion to describe ductile crack extension of longitudinal crack-like defects in high pressure pipeline steels. Laboratory testing of API 5L X60 and X70 steels at room temperature using standard, deeply cracked fracture specimens provides the data needed to measure the crack growth resistance curve and to calibrate the Gurson and the CTOA parameters for these materials. A central focus of the paper is the application of the cell methodology and the CTOA criterion to predict experimentally measured burst pressures for thin-walled gas pipeline containing longitudinal cracks. The experimental program includes precracked pipe specimens with 508 mm (20 inches) O.D. and 219 mm (8 5/8 inches) O.D. with varying crack depth to thickness ratios (at). Plane-strain and full 3D computations are conducted on detailed finite element models for the pipe specimens to describe crack extension with increased pressure. The numerical simulations demonstrate the effectiveness and limitations of both approaches to describe crack growth response and to predict the burst pressure for the tested pipes. While the CTOA criterion still appears to have limited applicability to predict ductile cracking behavior for the pipe specimens, the cell model predictions of the ductile response for the precracked pipes show good agreement with experimentally measured burst pressures.

Background: The use of stapling equipment for intestinal surgery in cats is rarely reported, and appropriate staple sizes for cat intestine are unknown. Objective: To determine staple cartridge sizes for thoracoabdominal (TA) and endoscopic gastrointestinal anastomosis (EndoGIA) that will simultaneously prevent leakage of small intestinal contents while also allowing for sufficient vascular permeability past the staple lines for intestinal healing. Methods: Two sizes of EndoGIA cartridges (2.0/2.5/3.0mm and 3.0/3.5/4.0mm) and two sizes of TA cartridges (2.5mm and 3.5mm), applied in a transverse manner across fresh cadaveric cat jejunum, were evaluated via intestinal burst pressure testing for maximum intraluminal pressure prior to leaking, and via infusion of an intravascular dye at normal arterial pressures to determine percentage of vascular patency past the staple lines. Vascular patency was compared not only from pre-and post-staple segments of the same intestinal sample, but also EndoGIA vascular patency was evaluated against TA vascular patency. Results: Two cats met study criteria. All samples had intraluminal burst pressures over twice the chosen minimum (of 30mmHg). Vascular patency post- staple line ranged from 0-90.8%, with the most consistently high numbers noted with the TA 3.5mm cartridges. No EndoGIA cartridge had a post- staple line vascular patency higher than 31.1%, and no intravascular dye was noted in any post- staple line sample in the EndoGIA 2.0/2.5/3.0mm group. Conclusions: While statistical analysis of the dataset was unable to be performed due to low numbers of samples for comparison, both intestinal intraluminal burst pressure trends and intravascular dye patterns suggested both the TA 3.5mm cartridge and (to a lesser extent) the 3.0/3.5/4.0mm EndoGIA cartridge could provide the ideal combination of intraluminal seal without restriction of vascular access for healing. The intravascular dye infusion technique, developed during this research, shows promise as a future instrument to determine vascular patterns around intestinal implants in cadaveric cat specimens. / Master of Science / Despite the regularity of feline small intestinal surgery, few reports exist of stapled anastomoses in cats, in part due to stapler size limitations. However, the recently developed endoscopic gastrointestinal anastomosis (EndoGIA) stapler shows promise as a future surgical tool for cats because it fits into cat intestine. In dogs, 3.5mm staples are often chosen for intestinal surgery; however, dog intestine is considerably thicker than cat intestine. The study goal was to evaluate not only intestinal burst pressures (the pressure at which repaired intestine leaks), but also the ability of fluids to flow through blood vessels that cross the staple lines of four stapler cartridge types from two staple lineages (EndoGIA 2.0/2.5/3.0mm, EndoGIA 3.0/3.5/4.0mm, TA 2.5mm, and TA 3.5mm). The central hypothesis was twofold. First, smaller stapler cartridge sizes (the EndoGIA 2.0/2.5/3.0mm and TA 2.5mm) would have higher intraluminal burst pressures when compared to the larger sizes (the EndoGIA 3.0/3.5/4.0mm). Second, larger stapler cartridges (the EndoGIA 3.0/3.5/4.0mm and the TA 3.5mm) would allow for increased flow of fluids in blood vessels past the stapler lines compared to the smaller cartridges (the EndoGIA 2.0/2.5/3.0mm and the TA 2.5mm). Two cats were included in the study. Trends in the data suggested that all components of the hypothesis might be proven with further data. However, due to the low number of cats acquired during the study period, the hypotheses could not be verified with statistics. The dye infusion technique to evaluate flow of fluids in blood vessels, developed during this research, shows promise as a future instrument to determine vascular patterns around intestinal implants. Future research should focus on acquiring more cats to have the ability able to perform statistical analyses (and prove the hypothesis), before proceeding with additional related studies.

Synthetic vascular grafts are useful to bypass diseased arteries. The long-term failure of synthetic grafts is primarily due to intimal hyperplasia at the anastomotic sites. The accelerated intimal hyperplasia may stem from a compliance mismatch between the host artery and the graft since commercially available synthetic conduits are much stiffer than an artery. The objective of this thesis is to design a method for fabricating a vascular graft that mechanically matches the patients native artery over the expected physiologic range of pressures. The creation of an optimized mechanical graft will hopefully lead to an improvement in patency rates. The mechanical equivalency between the graft and the host artery is defined locally by several criteria including the diameter upon inflation, the elasticity at mean pressure, and axial force. A single parameter mathematical for a thin-walled tube is used to describe of the final mechanical behavior of a synthetic graft. For the general problem, the objective would be to fabricate a mechanics-matching vascular graft for each host artery. Typically, fabrication parameters are set initially and the properties of the fabricated graft are measured. However, by modeling the entire fabrication process and final mechanical properties, it is possible to invert the situation and let the typical output mechanical values be used to define the fabrication parameters. The resultant fabricated graft will then be mechanically matching. As a proof-of-concept, several prototype synthetic grafts were manufactured and characterized by a single Invariant to match a canine artery. The resultant graft equaled the diameter upon inflation, the elasticity at mean pressure, and axial force of the native canine artery within 6%. An alternative to making an individual graft for each artery is also presented. A surgeon may choose the best graft from a set of pre-manufactured grafts, using a computer program algorithm for best fit using two parameters in a neighborhood. The design optimization problem was solved for both canine carotid and human coronary arteries. In conclusion, the overall process of design, fabrication and selection of a mechanics matching synthetic vascular graft is shown to be reliable and robust.

It was found that a significant improvement of mechanical properties of CFRPs can be achieved by the adjustment of the matrix properties such as toughness and CF/matrix adhesion via the chemical modification, as well as the physical modification by a small amount of cheap and environment-friendly nano fibers. Based on investigation of fracture mechanisms at macro/micro scale, the effects of matrix properties and nano fiber on the mechanical properties of CFRP have been discussed. Subsequently, the relationship has been characterized by a numerical model to show how to modulate the parameters of the matrix properties to achieve excellent fatigue properties of CFRP. / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University