Resistance spot welding is used frequently as a successful joining method for a variety of work commonly in automotive and other manufacturing processes. Spot weld nugget is generally hidden between two sheets, causing its inspection difficult and expensive. Undersized nuggets, brittle or cracked nuggets, and excessive indentation of electrodes reveals the lack of fusion between the parts that can make the weld sub-standard. Visual inspection, pry testing and physical teardown with chisel and hammer method or a combination of them are being used traditionally. However, this study presents a more effective nondestructive inspection method based upon an ultrasonic pulse-echo technique. The theory of the technique together with the experimental verification are presented and its advantages over the other destructive and nondestructive techniques are considered.

This dissertation is focused on the research of the applicability of the thermographic method in the diagnosis of concrete bridges in the Czech Republic. The theoretical part characterizes selected defects of concrete structures and the principle of their detection. The practical part describes the measurements made in the laboratory on the test specimen and the field on the concrete bridge. Most attention is paid to infrared thermography, ground-penetrating radar and ultrasonic pulse-echo method. Based on the results of the dissertation, recommendations for the use of the thermographic test method in practice were developed.

The ability to numerically determine the received signal in an ultrasound pulse-echo system is very important for the development of new ultrasound applications, such as tissue characterization, complex object recognition, and identification of surface topology. The output signal from an ultrasound pulse-echo system depends on the transducer geometry, reflector shape, location and orientation, among others, therefore, only by numerical modeling can the output signal for a given measurement configuration be predicted. This thesis concerns about the numerical modeling and optimal design of annular array based ultrasound pulse-echo system for object recognition. Two numerical modeling methods have been implemented and evaluated for calculating received signal in a pulse-echo system. One is the simple, but computationally demanding Huygens Method and the other one is the computationally more efficient Diffraction Response for Extended Area Method (DREAM). The modeling concept is further extended for pulse-echo system with planar annular array. The optimal design of the ultrasound pulse-echo system is based on annular array transducer that gives us the flexibility to create a wide variety of insonifying fields and receiver characteristics. As the first step towards solving the optimization problem for general conditions, the problem of optimally identifying two specific reflectors is investigated. Two optimization methods, the straightforward, but computationally intensive Global Search Method and the efficient Waveform Alignment Method, have been investigated and compared.

Orientador: Antonio Carlos Bannwart / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica e Instituto de Geociencias / Made available in DSpace on 2018-08-12T11:22:37Z (GMT). No. of bitstreams: 1 Santos_GuilhermeRosariodos_M.pdf: 4731485 bytes, checksum: 22f7c73b5cfe98d8ceda0b200e009a5f (MD5) Previous issue date: 2006 / Resumo: Um dos problemas cruciais no atual cenário da indústria nacional de petróleo é a medição das vazões de óleo, gás e água produzidos por cada poço. Este problema se agrava no contexto da produção de óleos pesados sob condições offshore em águas profundas, dadas as condições adversas desse ambiente, alta viscosidade do óleo, formação de emulsões com água, dificuldade natural para sua elevação e escoamento, entre outras. Excetuando os casos em que um poço é testado, quando então sua produção pode ser determinada na superfície, não se dispõe atualmente de sistemas e métodos de medição simples, confiáveis e não-intrusivos para as vazões de cada poço. O presente trabalho investiga a utilização de técnicas de ultra-som para fins de monitoramento do filme de água em escoamentos gás-líquido e líquido-líquido. O objetivo deste trabalho é desenvolver uma ferramenta de medição de espessura instantânea do filme líquido em escoamentos gás-líquido e líquido-líquido utilizando técnicas de ultra-som. A medição do tempo de trânsito do sinal acústico ultra-sônico através de uma camada de material - líquido, gás ou sólido - permite a obtenção da espessura local e instantânea dessa camada, a partir do conhecimento da velocidade de propagação do som nesse meio, através de calibração prévia. Assim, por meio de diversos experimentos com diferentes pares de fluidos e padrões de escoamento, pretende-se definir as melhores condições para utilização do ultra-som para esse fim. Os tempos de trânsito podem ser detectados através dos picos de amplitude gerados quando os pulsos refletidos atingem o receptor. A utilização do ultra-som é uma técnica não intrusiva e não-invasiva, isto é, não causa perturbações ao escoamento, possibilitando ainda medições in situ em tempo real de grandezas de escoamentos múltifásicos presentes inclusive na indústria do petróleo. Este estudo mostrou ser possível a aplicação da técnica de ultra-som paia escoamentos gás-líquido, uma vez que a diferença de impedância acústica permite que grande ,parte do pulso incidente seja refletida na interface entre os dois meios líquidos. Em escoamentos líquido-líquido, o monitoramento da espessura de filme é mais difícil, sendo necessário o uso de recursos computacionais mais robustos. A pequena diferença de impedância acústica entre os líquidos, muitas vezes, dificulta a captação do pulso correspondente à interface entre os meios líquidos. Um outro fator agravante é a presença de emulsões em escoamentos líquido-líquido ou óleos com viscosidades maiores. Nessas situações, a atenuação do pulso refletido na interface entre os dois meios líquidos é ainda maior. / Abstract: One of the most important problems in the current scenario of petroleum industry is the flow rate measurements of oil, gas and water produced by each well. This problem becomes more complicated in the context of heavy oils production under offshore conditions in deepwater, due to the adverse environment, high oil viscosity, formation of emulsion with water, difficulties for its lift and flow, etc. Excepting the cases in which a well is being tested, when its flow rate can be determined at the surface, it does not exist any simple, reliable and non-intrusive system or measurement method for flow rate of an individual well. The present work looks over an application of ultrasonic techniques for monitoring of water film in gas-liquid and liquid-liquid flows. The specific purpose of this work is to develop a toei for instantaneous thickness measurement of liquid film in gas-liquid and liquid-liquid flows by ultrasonic techniques. The transit time measurement of an acoustic signal through a material layer (solid, liquid or gas) allows its local and instantaneous evaluation, knowing the ultrasound propagation speed for each medium from previous calibration. ln this way, through several experiments with different fluid pairs and flows pattems, it intends to establish the better conditions for application of the ultrasound technique. The transit times can be detected through the amplitude peaks generated when the reflected pulses reach the receiver. The ultrasound application is a non-invasive and non-intrusive technique, that is, it does not cause any disturbance in the flow, allowing in situ measurements in real time of many parameters of multiphase flows inc1uding the petroleum industry. This study showed the possibility of applying a pulse-echo technique t6 the gas-liquid flows, because the acoustic impedance difference allows the majority of incidem,t ultrasound be reflected in the gas-liquid interface. The monitoring of liquid films thickness is more difficult in liquid-liquid flows, being necessary the use oi rugged computational resources. The low difference of acoustic impedance between liquids can make more difficult the reception of a pulse which corresponds to the liquid-liquid interface. Another difficulty occurs when emulsions are formed or the oil is highly viscous. ln these situations, the attenuation of reflected ultrasound from the liquid-liquid interface is still larger. / Mestrado / Explotação / Mestre em Ciências e Engenharia de Petróleo

Neste trabalho são analisados os campos acústicos gerados por transdutores ultrassônicos planos e circulares, do tipo pistão plano, no modo pulso-eco, trabalhando como emissor e receptor de ondas, com freqüências de 1,6 MHz, 2,25 MHz e 5 MHz. As ondas emitidas por esses transdutores interagem com interfaces denominadas alvos, com diversas geometrias de superfícies, como planas e circulares, planas com cavidade do tipo alvéolo circular, e cone reto, todas compostas de alumínio e imersas em tanque com água. O campo acústico refletido varia de acordo com o tipo de geometria do alvo. Para essas analises foram produzidas e comparadas modelagens do campo acústico no software Matlab, por meio de dois modelos teóricos: método da resposta impulsiva e método da representação discreta. Foram analisados o tempo de computação produzido pelo método numérico com relação a discretização dos elementos de área do transdutor e do alvo, alem da influencia da conversão de modo nas respostas impulsivas simuladas para essas superfícies. Os resultados mostraram uma boa correlação entre os dois métodos teóricos, porem o de representação discreta possibilita o estudo em transdutores com geometria diferente do pistão plano, sem o uso de integrais complexas. As diferenças dos resultados experimentais e teóricos podem ser minimizadas por meio de uma escolha adequada da relação entre a discretização e comprimento de onda (Dx/), em que foi considerado um valor aceitável de erro relativo de 15% para Dx/ 0,68. Foi observado que o uso da conversão de modo na interface refletora influi apenas na amplitude do sinal de eco (atenuação) e não na forma do sinal. / This work deals with acoustic fields generated by ultrasonic broadband transducers as a planar circular piston, operating in pulse-echo mode, with frequencies of 1.6 MHz, 2.25 MHz and 5 MHz. The waves emitted by transducers interact with water-immersed aluminum targets of different geometries such as planar circular surfaces, concave circular cavity on plane surfaces, and right circular conical surfaces. The impulse response and the discrete representation methods were applied to model the echo responses, using the Matlab software. The influence of mode conversion over the simulated impulse responses for these surfaces was analyzed. The results show a good correlation between the two theoretical methods, but the discrete representation enables the study of arbitrary aperture transducers, with no need to solve complex integrals. The computational times of the discrete representation method was analyzed were respect to the spatial discretization of both the transducer aperture and the target. Experimental tests were carried out to validate the simulated results. Differences in experimental and theoretical results can be minimized by an appropriate choice of the discretization/wavelength ratio (Dx / ). A relative error of 15% was considered acceptable for Dx / 0,68. It was observed that the use of mode conversion at the reflected interface modifies only the amplitude of the echo signal (attenuation), but not its shape.

Neste trabalho são analisados os campos acústicos gerados por transdutores ultrassônicos planos e circulares, do tipo pistão plano, no modo pulso-eco, trabalhando como emissor e receptor de ondas, com freqüências de 1,6 MHz, 2,25 MHz e 5 MHz. As ondas emitidas por esses transdutores interagem com interfaces denominadas alvos, com diversas geometrias de superfícies, como planas e circulares, planas com cavidade do tipo alvéolo circular, e cone reto, todas compostas de alumínio e imersas em tanque com água. O campo acústico refletido varia de acordo com o tipo de geometria do alvo. Para essas analises foram produzidas e comparadas modelagens do campo acústico no software Matlab, por meio de dois modelos teóricos: método da resposta impulsiva e método da representação discreta. Foram analisados o tempo de computação produzido pelo método numérico com relação a discretização dos elementos de área do transdutor e do alvo, alem da influencia da conversão de modo nas respostas impulsivas simuladas para essas superfícies. Os resultados mostraram uma boa correlação entre os dois métodos teóricos, porem o de representação discreta possibilita o estudo em transdutores com geometria diferente do pistão plano, sem o uso de integrais complexas. As diferenças dos resultados experimentais e teóricos podem ser minimizadas por meio de uma escolha adequada da relação entre a discretização e comprimento de onda (Dx/), em que foi considerado um valor aceitável de erro relativo de 15% para Dx/ 0,68. Foi observado que o uso da conversão de modo na interface refletora influi apenas na amplitude do sinal de eco (atenuação) e não na forma do sinal. / This work deals with acoustic fields generated by ultrasonic broadband transducers as a planar circular piston, operating in pulse-echo mode, with frequencies of 1.6 MHz, 2.25 MHz and 5 MHz. The waves emitted by transducers interact with water-immersed aluminum targets of different geometries such as planar circular surfaces, concave circular cavity on plane surfaces, and right circular conical surfaces. The impulse response and the discrete representation methods were applied to model the echo responses, using the Matlab software. The influence of mode conversion over the simulated impulse responses for these surfaces was analyzed. The results show a good correlation between the two theoretical methods, but the discrete representation enables the study of arbitrary aperture transducers, with no need to solve complex integrals. The computational times of the discrete representation method was analyzed were respect to the spatial discretization of both the transducer aperture and the target. Experimental tests were carried out to validate the simulated results. Differences in experimental and theoretical results can be minimized by an appropriate choice of the discretization/wavelength ratio (Dx / ). A relative error of 15% was considered acceptable for Dx / 0,68. It was observed that the use of mode conversion at the reflected interface modifies only the amplitude of the echo signal (attenuation), but not its shape.

Esta Tesis Doctoral presenta un sistema automatizado de inspección no destructiva de materiales usando ultrasonidos para la detección de heterogeneidades en piezas metálicas, en concreto, de acero al carbono de tipo S275JR. Para ello, se han utilizado guías lineales que se han automatizado con motores paso a paso cuyos movimientos se controlan desde el computador, mediante una aplicación gráfica diseñada específicamente para este trabajo. Una vez detectados los defectos, se permite una posterior clasificación de los defectos según morfología, posición y tamaño con programas que utilizan algoritmos basados en Reconocimiento de Patrones. Tras su ejecución se obtienen los informes de resultados indicando la estimación de los datos buscados. / This Thesis presents an automated system to the inspection of materials using ultrasounds to the detection of heterogeneities in metallic pieces, in particular, carbon steel S275JR. For that, it used linear guides that have been automated with stepper motors, whose movements are controlled from the computer using a graphic application designed specifically to this research. When defects are detected, it allows the later classification of defects according to their morphology, size and position with programs that use algorithms based on Pattern Recognition. After execution of the programs, results reports provide an optimal estimation of expected data.

A piezoelectric impedance-based structural health monitoring technique was developed at the Center for Intelligent Material Systems and Structures. It has been successfully implemented on several complex structures to detect incipient-type damage such as small cracks or loose connections. However, there are still some problems to be solved before full scale development and commercialization can take place. These include: i) the damage assessment is influenced by ambient temperature change; ii) the sensing area is small; and iii) the ability to identify the damage location is poor. The objective of this research is to solve these problems in order to apply the impedance-based structural health monitoring technique to real structures. First, an empirical compensation technique to minimize the temperature effect on the damage assessment has been developed. The compensation technique utilizes the fact that the temperature change causes vertical and horizontal shifts of the signature pattern in the impedance versus frequency plot, while damage causes somewhat irregular changes. Second, a new impedance-based technique that uses multiple piezoelectric sensor-actuators has been developed which extends the sensing area. The new technique relies on the measurement of electrical transfer admittance, which gives us mutual information between multiple piezoelectric sensor-actuators. We found that this technique increases the sensing region by at least an order of magnitude. Third, a time domain technique to identify the damage location has been proposed. This technique also uses multiple piezoelectric sensors and actuators. The basic idea utilizes the pulse-echo method often used in ultrasonic testing, together with wavelet decomposition to extract traveling pulses from a noisy signal. The results for a one-dimensional structure show that we can determine the damage location to within a spatial resolution determined by the temporal resolution of the data acquisition. The validity of all these techniques has been verified by proof-of-concept experiments. These techniques help bring conventional impedance-based structural health monitoring closer to full scale development and commercialization. / Master of Science

This thesis deals with the inspection and construction-technical survey of the highway bridges D2-058..1 and D2-058..2. These structures ale located on the border with the Slovak Republic and were built in 1980. The thesis is focused on the substructure of this long overpass, because of its major failures caused by leaking water. Theoretical part contains information about construction-technical surveys of the bridges, bridges inspections and theory of ultrasound methods. That method has been used in the practical part for identification of the damage extent. Also, material property have been verified and overall condition of the substructure has been evaluated.