No description available.

The work presented in this thesis concerns the problem of detecting and characterising the effect of fibre-matrix debonds in a fibre-reinforced composite, on ultrasonic backscattering. Theoretical and experimental investigations were conducted into this problem. Three mathematical models were examined. The first assumed that the debond was a thin crack with non-contacting faces surrounding the fibre. The second modelled the debond by allowing tangential slip between the matrix and fibre defined by an effective shear modulus, K. For the third model, the debond was approximated by a thin visco-elastic layer separating the matrix and fibre. The results of the modelling suggested that for an incident longitudinal wave, the first model acts as an air-filled void with a sharp resonance present in the low ka region. The second and third models both show the backscattering to be attenuated. Experimental investigations were carried out on scale models of a single fibre embedded in an araldite matrix. Steel or copper wires were used for the reinforcing fibre. The agreement between theory and experiment for a well-bonded wire was excellent. The effect on the longitudinal backscattered wave of the wire immediately after debonding was to attenuate heavily the resonances in the backscatter form function. However, after approximately an hour the scatter is seen to relax, closely resembling that from a well-bonded wire. In view of the only partial ability of longitudinal incident waves to detect debonds, shear wave (SH) incidence was investigated. It was shown that shear waves were far more sensitive to the presence of fibre-matrix debonds.

This thesis evaluates a particular ultrasonic nondestructive testing (NDT) system in order to determine its capabilities and limitations in locating defects in concrete structures; specifically tunnel linings, bridge decks, and pavements. The device, a phased-array ultrasonic tomography (UST) system that utilizes shear waves, is a significant advancement in NDT systems. Consequently, there is a need in structural engineering to verify new technologies by assessing their flaw-detecting capabilities in a variety of structural applications. The UST technique does not currently have a testing methodology that is field-ready. In order to develop a methodology, the system was evaluated based on its ability to detect simulated defects, then taken to the field to evaluate natural structural defects on public tunnels, pavements, and airport runways. Types of concrete defects the system is used to detect and localize include air- and water-filled voids, vertical cracks, horizontal delaminations, and abnormalities such as clay lumps. The device is also used to determine reinforcement depth and spacing as well as concrete thickness measurements. This research concludes that the UST system is exceptional at locating horizontal delaminations ranging from 0.05-2.0 mm (0.002-0.079 in.), and is able to differentiate between fully debonded and partially-bonded areas. Vertical cracks could only be detected once they begin to form parallel to the testing surface; however, omission of surface details was found to be a strong indicator of crack presence. Backwall surfaces up to a depth of 762 mm (30 in.) were successfully and accurately determined. Air- and water-filled voids as well as reinforcement details such as layout and depth were also successfully determined and located. With the exception of some medium-sized clay lumps (with a diameter of approximately 102 mm, or 4 in.) surrounding reinforcement, all clay lumps tested were also highly successful.

Submitted by Kleber Silva (kleberbs@ufba.br) on 2017-06-01T20:18:43Z No. of bitstreams: 1 Tese final - Amâncio.pdf: 4405750 bytes, checksum: ceb4c269d4cf1fa74d0861c679a6f10d (MD5) / Approved for entry into archive by Vanessa Reis (vanessa.jamile@ufba.br) on 2017-06-07T11:28:44Z (GMT) No. of bitstreams: 1 Tese final - Amâncio.pdf: 4405750 bytes, checksum: ceb4c269d4cf1fa74d0861c679a6f10d (MD5) / Made available in DSpace on 2017-06-07T11:28:44Z (GMT). No. of bitstreams: 1 Tese final - Amâncio.pdf: 4405750 bytes, checksum: ceb4c269d4cf1fa74d0861c679a6f10d (MD5) / Context: Code smell is a term commonly used to describe potential problems in the design of object-oriented systems. The theory about code smells, initially presented in nineties, is focused on characterization of different types of smells and heuristics for their detection and removal. Since then, empirical studies have evaluated the impact of the practical adoption of the code smell concept on software development. We call this issue the code smell effect. The findings of empirical studies on the code smell effect have presented inconsistencies with respect to what is expected by the theory. This phenomenon is not well understood. Objective: Enhancing the understanding of the code smell effect, characterizing problems hindering the practical adoption of the smell concept and investigating their origin. More specifically, we focus on the major confounding factor affecting observations on the code smell effect, which is the human role on smell detection. The human role is mostly disregarded by the theory and it strongly affects the experiments on the subject. Method: We explore the problem empirically, from two perspectives. First, we synthesize the current knowledge on the code smell effect from a set of primary studies published in the literature. To do this, we performed a systematic review based on thematic synthesis. Second, we propose the investigation of factors affecting the human evaluation of smells. To do this, we performed a family of controlled experiments. In it, we investigate an extensive number of factors affecting the human perception of smells. The factors are the use of design comprehension tool support; developer's experience, knowledge and training; and software size. From the thematic synthesis and the family of controlled experiments, we identify challenges for the area and present them as a research agenda. Results: We find out that human evaluation of smell should not be trusted. The studies indicate that the agreement on smell detection is low. They also show that demographic attributes, such as developers' experience, impact the agreement on smell detection. We also concluded that, nowadays, there are not evidences supporting the use of code smells for practical evaluation of design quality. Our evidences are divergent findings correlating code smells and software attributes, such as changes on source code. In some cases, the studies converge showing that code smells do not impact some attributes. This happens, for example, with studies correlating smells and effort on maintenance. Conclusion: This thesis points out to the gap between the theory and the experimental findings about the code smell effect. Our evidences indicate that the main source for this gap is the low number of studies focusing on the human role on the smell effect. The researches on the subject should focus on better understanding this issue. This not seems the path followed by the area, which has directed its effort on researches focused on tool assessments, such as automatic detection or smell removal. In order to face the problem, we propose a research agenda, indicating that the area needs to: i) investigate the nature of smells, grouping them according to their characteristics; ii) explore human factors affecting smell detection, and their relationships; iii) explore cognitive aspects affecting human perception of smells; and iv) outline attributes of the experiments in order to classify the context where findings can be grouped. These challenges indicate some paths to be followed by the area in order to systematize the use of code smell in the practice of the software development. Despite difficulties, we believe that this is possible and our thesis contributes for this journey. / Contexto: Code smell ´e um termo comumente utilizado para descrever potenciais problemas em projetos de software orientados a objetos. A teoria relacionada a code smells, inicialmente apresentada nos anos noventa, tem foco na caracteriza¸c˜ao de diferentes tipos de smells e nas estrat´egias para sua detec¸c˜ao e remo¸c˜ao. Desde ent˜ao, estudos emp´ıricos tˆem avaliado o impacto da ado¸c˜ao do conceito de code smell no desenvolvimento de software, ou seja, o “efeito code smell”. Os resultados destes estudos tˆem apresentado inconsistˆencias com rela¸c˜ao aos efeitos propostos pela teoria. As causas deste fenˆomeno n˜ao s˜ao bem compreendidas. Objetivo: Melhorar a compreens˜ao sobre o efeito code smell, identificando problemas que tˆem dificultado uso do conceito no desenvolvimento de software. Mais especificamente, nos concentramos no papel humano na detec¸c˜ao de smells. O fator humano ´e uma vari´avel pouco considerada pela teoria, mas afeta significativamente os resultados dos estudos emp´ıricos sobre o tema. M´etodo: N´os exploramos o problema de forma emp´ırica, a partir de duas perspectivas. Primeiro, n´os sintetizamos o conhecimento relacionado ao efeito code smell a partir de um conjunto de estudos prim´arios existente na literatura. Para isso, n´os realizamos uma revis˜ao sistem´atica, com base no m´etodo de s´ıntese tem´atica. Segundo, n´os propusemos a investiga¸c˜ao de fatores que afetam a percep¸c˜ao humana sobre smells. Neste caso, n´os realizamos uma fam´ılia de experimentos controlados, investigando um extensivo n´umero de fatores que afetam a percep¸c˜ao humana sobre smells. Os fatores s˜ao: o uso de ferramentas de suporte `a compreens˜ao do projeto de software; a experiˆencia; o conhecimento te´orico sobre code smells e o treinamento dos desenvolvedores; e o tamanho do software. A partir da s´ıntese tem´atica e da fam´ılia de experimentos, n´os identificamos alguns desafios para a ´area, apresentandoos como uma agenda de pesquisa. Resultados: N´os percebemos que a avalia¸c˜ao humana de smells n˜ao ´e confi´avel. Os estudos indicam que o grau de concordˆancia relacionado `a avalia¸c˜ao humana ´e baixo. Al´em disso, os estudos mostram que atributos demogr´aficos, como experiˆencia do desenvolvedor, afetam o grau de concordˆancia na detec¸c˜ao de smells. Tamb´em conclu´ımos que n˜ao h´a evidˆencias que indiquem o uso do conceito de code smells como ferramenta para a avalia¸c˜ao da qualidade dos projetos de software. Estas evidˆencias s˜ao as inconsistˆencias nos resultados correlacionando os smells e atributos de software, como mudan¸cas no c´odigo. Em alguns casos, os estudos concordam que os smells n˜ao tem correla¸c˜ao com certos atributos. Isso ocorre, por exemplo, com estudos correlacionando smells e esfor¸co na manuten¸c˜ao de software. Conclus˜ao: Esta tese evidencia uma lacuna existente entre a teoria e os estudos emp´ıricos relacionados ao efeito code smell. Nossas evidˆencias apontam o baixo n´umero de estudos abordando o papel humano na detec¸c˜ao de smells como principal causa desta lacuna. Pesquisas na ´area devem se concentrar em entender este aspecto. Este n˜ao parece ser o caminho seguido pela ´area, que tem se concentrado principalmente no desenvolvimento de ferramentas de suporte, como ferramentas para detec¸c˜ao autom´atica e remo¸c˜ao de smells. Para auxiliar neste sentido, n´os propomos uma agenda de pesquisa indicando pontos importantes a serem considerados: i) investiga¸c˜ao da natureza dos smells, agrupando-os de acordo com suas caracter´ısticas; ii) explora¸c˜ao de fatores humanos afetando a detec¸c˜ao de smells e seus inter-relacionamentos; iii) explora¸c˜ao de aspectos cognitivos afetando a percep¸c˜ao humana de smells; e iv) identifica¸c˜ao de atributos relacionados aos estudos emp´ıricos de forma a delinear o contexto onde resultados podem ser agrupados. Estes desafios indicam alguns caminhos que a ´area pode seguir para sistematizar o uso do conceito de code smell no desenvolvimento de software. Apesar das dificuldades, n´os acreditamos que isso ´e poss´ıvel e nossa tese visa a contribuir neste sentido.

Master of Science / Food Science Institute - Animal Sciences & Industry / Jayendra K. Amamcharla / High-protein dairy powders are added to a variety of products to improve nutritional, functional, and sensory properties. To have the intended properties, the powder must be soluble. The solubility is effected by processing storage, and dissolution conditions, as well as the type of powder. Various tests are used to determine solubility, but they are time-consuming and subjective. Literature has shown that ultrasound spectroscopy can characterize the solubility of high-protein dairy powders, but it requires expensive equipment and skilled technicians. An economical alternative is to use an ultrasonic flaw detector, which is commonly used in the construction industry. For this study, an ultrasonic flaw detector based method was developed to characterize the solubility of high protein dairy powders. To evaluate the method, commercially available milk protein concentrate (MPC) was obtained and stored at 25°C and 40°C and stored for four weeks to produce powders with different dissolution properties. To test the powders, a 5% (w/w) concentration of powder was added to water. A focused beam reflectance measurement (FBRM) and solubility index were used as a reference method. After powder addition, data was collected at regular intervals for 1800s. The FBRM and solubility index showed that the powders lost solubility as the storage time and temperature increased. From the ultrasound data, one parameter was extracted from the relative velocity and three parameters were extracted from the attenuation data. A soluble powder had a low relative velocity standard deviation from 900-1800s, high area under the attenuation curve, low peak time, and high peak height. The ultrasonic flaw detector detected differences in solubility before the solubility index. When testing MPC with protein contents ranging from 85% to 90% and at a dissolution temperature of 40°C and 48°C, data from the ultrasonic flaw detector and FBRM showed that the solubility decreased as the protein content increased and increasing the dissolution temperature improved the solubility of the powder. Overall, the ultrasonic flaw detector can characterize the solubility of high-protein dairy powders.

Since the introduction of fiber reinforced polymers (FRP) for the repair and retrofit of concrete structures in the 1980’s, considerable research has been devoted to the feasibility of their application and predictive modeling of their performance. However, the effects of flaws present in the constitutive components and the practices in substrate preparation and treatment have not yet been thoroughly studied. This research aims at investigating the effect of surface preparation and treatment for the pre-cured FRP systems and the groove size tolerance for near surface mounted (NSM) FRP systems; and to set thresholds for guaranteed system performance. The research included both analytical and experimental components. The experimental program for the pre-cured FRP systems consisted of a total of twenty-four (24) reinforced concrete (RC) T-beams with various surface preparation parameters and surface flaws, including roughness, flatness, voids and cracks (cuts). For the NSM FRP systems, a total of twelve (12) additional RC T-beams were tested with different grooves sizes for FRP bars and strips. The analytical program included developing an elaborate nonlinear finite element model using the general purpose software ANSYS. The model was subsequently used to extend the experimental range of parameters for surface flatness in pre-cured FRP systems, and for groove size study in the NSM FRP systems. Test results, confirmed by further analyses, indicated that contrary to the general belief in the industry, the impact of surface roughness on the global performance of pre-cured FRP systems was negligible. The study also verified that threshold limits set for wet lay-up FRP systems can be extended to pre-cured systems. The study showed that larger surface voids and cracks (cuts) can adversely impact both the strength and ductility of pre-cured FRP systems. On the other hand, frequency (or spacing) of surface cracks (cuts) may only affect system ductility rather than its strength. Finally, within the range studied, groove size tolerance of +1/8 in. does not appear to have an adverse effect on the performance of NSM FRP systems.

Ceramic composites for high temperature applications must be designed with crack arrest capability to improve the resistance to flaws produced in service, such as by thermal shock. Laminated composites containing Al2O3 layers in 3mol%Y2O3-ZrO2 (TZ3Y) were fabricated by electrophoretic deposition (EPD) and pressureless sintering. The layering design (Al2O3 layer thickness and volume fraction) was varied to determine the influence on fracture behaviour. The residual stress in Al2O3 layers was measured using a fluorescence spectroscopy technique. The fracture strength of 15 different laminates, and monolithic Al2O3 and TZ3Y, was tested in 4-point bending at room temperature. Vickers indentation (10 kg load) was used to simulate natural flaws at the sample surface before testing as a measure of flaw tolerance. Fracture ranged from catastrophic failure, to multi-stage failure and complete delamination (in processing). Transitions in behaviour were found related to a geometrical parameter derived from the strain energy release rate for edge cracks. The strength of three Al2O/TZ3Y composites was compared with monolithic Al2O3 and TZ3Y for a range of indentation loads (up to 20 kg). The strength of the composites was similar to monolithic TZ3Y but the flaw tolerance was improved due to multi-stage fracture. The strength and flaw tolerance (using 10 kg indentation) of two Al2O3/TZ3Y composites and monolithic TZ3Y was measured < 1300°C. The multi-stage fracture behaviour disappeared > 25 °C, and there was no beneficial effect of the Al2O3 layers on the strength. Superplastic deformation of the TZ3Y layers at 1300°C was prevented by the constraint of the Al2O3 layers. Recommendations are made about the design of flaw tolerant ceramic laminates for high temperature use. / Thesis / Master of Engineering (ME)

Fatigue assessments have been carried out predominantly with quasi-deterministic approaches, such as the use of SN curves. However, both the loading and the resistance of fatigue prone components are subjected to significant uncertainties. Consequently, a prediction of the remaining fatigue life based on deterministic load and resistance models can lead to unreliable results. This work presents a general reliability-based approach to predict fatigue life of steel components. The approach incorporates prediction of fatigue crack initiation, modeled with a strain-based correlation approach, and propagation, modeled using a linear elastic fracture mechanics approach, and is applicable to new, cracked or repaired structural components. Based on the analysis of existing test results and additional crack initiation and propagation tests on weld metal, the relevant probabilistic fatigue material properties of grade 350WT steel and a matching weld metal were established. An experimental program was carried out on welded details tested either in the as-welded, stress-relieved, conventionally peened, or ultrasonically peened condition. It was demonstrated that ultrasonic peening is superior to the other investigated post weld treatment methods. Using finite element analyses, the results of the tests were deterministically predicted for several different initial conditions, including initial flaw and crack sizes and locations, as well as different levels of residual stresses. A model incorporating an initial flaw and accounting for crack closure and the threshold stress intensity factor range was retained. A probabilistic analysis using Monte Carlo Simulation was carried out to calibrate the relevant parameters. A general reliability-based approach, which includes both the loading and resistance sides of the limit state function was proposed and applied to three practical examples: prediction of test results from two test programs and the prediction of the remaining fatigue life of a cracked component as a function of the safety index. These three applications demonstrated that accurate fatigue life predictions targeting a predefined safety index are achieved. / Structural Engineering

No description available.

This thesis deals with the issue of determining the causes of defects and failures, focusing on a specific property and their significance in determining the price of the property. The first part focuses on the theory explaining the basic concepts used in the valuation of real estate, basic methods of property valuation and classification of construction defects and failures. This chapter includes an analysis of the real estate market in the years 2008 - 2013. The second part is devoted to determining the amount of property damage at a specific property, the calculation of this particular property which is based on technical surveys and subsequent valuation of the property with regard to the results of the survey. The aim is to create a design procedure for reducing the price of the property with the defect.