Pneumatic drives are an integral part of many machinery, with high demands on their reliability. Unfortunately, they sometimes fail, either due to improper production or assembly at the factory or by gradual degradation of moving parts and sealing elements during operation. Current diagnostic methods do not allow localization or identification of the type of damage and do not allow the operator to make a qualified decision. This work deals with the use of acoustic emission for these purposes. On PB type cylinders manufactured by Poličské strojírny a.s., a methodology is introduced which leads to the direct identification or at least localization of selected defects. By implementing this methodology in the final inspection of the production plant, the percentage of exposed pieces of waste will be increased, thus preventing accidents of these faulty pieces during operation.

Volvo Group Truck Technology has the ambition to automate parts of their routine service. Therefore a project was launched to investigate which parts of the routine that could be automated. The idea of this project is to lower the time spent on the service and also improve the working environment for the personnel. The purpose of this thesis is to develop and build a conceptional prototype for a low-cost crack detecting sensor. This thesis is a part of a larger proof of concept project which Volvo GTT runs in cooperation with Robotdalen and Robot Application Center (RAC). The work done in this thesis has been based on literature studies, interviews and company visits. The gathered knowledge and observations was translated into what would be required to fit the needs. This thesis covers different techniques that could be used to detect flaws in braking discs. However, this thesis is mostly focused on one non-destructive method technique based on induced eddy currents. Several non-destructive techniques and conceptual designs has been tested and evaluated with varying results during this project. The result of this thesis was a design that reacts to discontinuities in conductive materials, such as the grey cast iron material used in the Volvo trucks braking discs. The results are represented as a voltage drop change and can be visualized by an oscilloscope. This study shows that the method of choice has the potential to be used as a crack detecting system and that the system can be built reliable with rather cheap components. Further development should aim towards making the design even cheaper and the components should be assembled on a PCB instead of a breadboard in order to make the system less sensitive to noise and easier to assemble alongside the trucks braking discs.

A técnica de perfilagem gama de colunas de destilação já está no mercado há pelo menos 30 anos. Acompanhando o desenvolvimento tecnológico mundial, a técnica e a indústria prosperaram e se difundiu, podendo ser encontrada em diversos países e sendo implementada por diversas empresas comerciais e centros de pesquisa. Todavia, apesar das melhorias na qualidade dos resultados bem como na rapidez e praticidade da tomada de dados; o conceito básico da técnica permaneceu inalterado. Este trabalho condensa como o aprendizado de 20 anos, em gamma scan e tomografia industrial, propiciou fundamentos para uma técnica inovadora, testada em laboratório e depois efetivamente aplicada em condições reais de campo, que permitiu obter resultados nunca antes obtidos numa perfilagem de coluna. / Distillation column gamma scanning has been in the market for more than 30 years. Following world\'s technology development the industry grew and spread worldwide. Nowadays gamma scanning can be found in many countries performed by commercial companies and research centers either. However, in spite of all development achieved, resulting in high quality data and easy data sampling; the technology concepts remains the same. This works condense how 20 years apprentice ship in gamma scanning and industrial tomography, rise up fundaments for an innovative technique, tested in laboratory scale and effectively applied in real field conditions; culminated in results that have never been obtained with a gamma scan.

A técnica de perfilagem gama de colunas de destilação já está no mercado há pelo menos 30 anos. Acompanhando o desenvolvimento tecnológico mundial, a técnica e a indústria prosperaram e se difundiu, podendo ser encontrada em diversos países e sendo implementada por diversas empresas comerciais e centros de pesquisa. Todavia, apesar das melhorias na qualidade dos resultados bem como na rapidez e praticidade da tomada de dados; o conceito básico da técnica permaneceu inalterado. Este trabalho condensa como o aprendizado de 20 anos, em gamma scan e tomografia industrial, propiciou fundamentos para uma técnica inovadora, testada em laboratório e depois efetivamente aplicada em condições reais de campo, que permitiu obter resultados nunca antes obtidos numa perfilagem de coluna. / Distillation column gamma scanning has been in the market for more than 30 years. Following world\'s technology development the industry grew and spread worldwide. Nowadays gamma scanning can be found in many countries performed by commercial companies and research centers either. However, in spite of all development achieved, resulting in high quality data and easy data sampling; the technology concepts remains the same. This works condense how 20 years apprentice ship in gamma scanning and industrial tomography, rise up fundaments for an innovative technique, tested in laboratory scale and effectively applied in real field conditions; culminated in results that have never been obtained with a gamma scan.

"Despite its maturity, the powder metallurgy (PM) fabrication process continues to rely heavily on indirect methods to determine and predict the quality of its compacts early in the manufacturing line. Currently, the most comprehensive testing is performed on sintered parts, resulting in higher cost and increased waste. This dissertation addresses the need of early inspection by developing a novel approach whereby PM compacts are tested in the green-state without intrusion and with minimal cost per compact tested. The method is based on an infrared detection scheme with two fundamental embodiments. For high resolution applications, or offline testing, an active thermography approach is adopted; electric energy is deposited into the compact in a contact-less fashion to evaluate all parts for cracks, inclusions, or delaminations. As an alternative, for lower resolution high-yield applications, a system based on a passive thermography approach is developed. This system relies on residual heating emanating from the process. Thermal data is then collected and analyzed in an effort to yield part integrity and process stability information. In this dissertation we will discuss our design approach, theoretical modeling aspects, and a proof-of-concept instrument with associated data processing software. We will first describe the underlying physical principles, followed by predictions from the modeling formulation, including a solution of the heat equation. As part of our experimental data processing, we will present results that are collected both in a laboratory setting and in an industrial manufacturing line. The integrity of the compacts is carried out with the aid of a specialized software package."

"Non-destructive testing (NDT) is critical to many precision industries because it can provide important information about the structural health of critical components and systems. In addition, NDT can also identify situations that could potentially lead to critical failures. Specifically, NDT by optical methods have become popular because of their non-contact and non-invasive nature. Shearography is a high-resolution optical NDT method for identification and characterization of structural defects in components and has gained wide acceptance over the last decade. Traditional workflow of NDT by shearography has been determined to be inefficient, due to the requirements of having experienced operators that must determine the most suitable loading methods to identify defects in samples under testing as well as to determine the best system arrangement for obtaining the maximum measuring sensitivity. To reduce the number of experiments that are required and to allow inspectors to perform NDT by laser shearography in a more efficient way, it is necessary to optimize the experimental workflow. The goal of the optimization would be an appropriate selection of all experimental variables including loading methods, boundary conditions, and system¡¯s sensitivities, in order to avoid repeating experiments several times in the processes of components characterization and health monitoring. To achieve this goal, a hybrid approach using shearographic fringe prediction with Finite Element Analysis (FEA) has been developed. In the FEA simulations, different loading conditions are applied to samples with defects, and in turn, the shearographic fringes are predicted. Fringe patterns corresponding to specific loading conditions that are capable of detecting defects are chosen and experimental tests are performed using those loading conditions. As a result, using this approach, inspectors could try different combinations of loading methods, and system¡¯s sensitivities to investigate and select appropriate experimental parameters to improve defect detection capabilities of the system by using low-cost computer simulations instead of lengthy and expensive experiments. In addition, to improve the identification of defects on the sample, camera calibration and image registration algorithms are used to project the detected defects on the sample itself to locate and visualize the position of defects during shearographic investigations. This hybrid approach is illustrated by performing NDT of a plate made of acrylic that has a partial hole at the center. Fringe prediction with finite element analysis are used to characterize the optimized experimental procedures and in turn, corresponding measurements are performed. A multimedia projector is employed to project the defects on the surface of the plate in order to visualize the location of the partial hole (defect). Furthermore, shearographic system is used for other applications including NDT of a composites plate and of a thin latex membrane. The procedures shows the effectiveness of the approach to perform NDT with shearography methods. "

Tese de mestrado integrado. Engenharia Civil. Faculdade de Engenharia. Universidade do Porto. 2010

In certain industries, quality testing is crucial, to make sure that the components being manufactured do not contain any defects. One method to detect these defects is to heat the specimen being inspected and then to study the cooling process using infrared thermography. The explorations of non-destructive testing using thermography is at an early stage and therefore the purpose of this thesis is to analyse some of the existing techniques and to propose improvements. A test specimen containing several different defects was designed specifically for this thesis. A flash lamp was used to heat the specimen and a high-speed infrared camera was used to study both the spatial and temporal features of the cooling process. An algorithm was implemented to detect anomalies and different parameter settings were evaluated. The results show that the proposed method is successful at finding the searched for defects, and also outperforms one of the old methods.

Nondestructive testing (NDT) plays a more important role today in evaluating structural integrity of civil infrastructure. Impact-echo method (IE) is an effective stress wave based NDT method for locating defects in concrete structures. However, the contact requirement between sensor and concrete surface significantly limits the test speed and wide application of this method to large-scale structures such as bridges. Recent studies show the feasibility of air-coupled sensing, which eliminates the contact requirement and thus accelerates IE test. To further improve the test speed, a fully non-contact IE test using air-coupled sensing and excitation is investigated in this dissertation. This dissertation provides the theoretical basis required for developing an effective air-coupled IE method. For air-coupled sensing, 2D numerical simulations are first conducted to study the wave propagation in the air-solid system during IE tests. Visualized wavefield indicates that parabolic reflectors can effectively enhance the IE signal strength by focusing airborne IE waves to an air-coupled sensor. To maximize signal amplification, an analytical solution for the focused axial pressure response of a parabolic reflector with incident plane waves is derived. This solution is used to determine the reflector geometry that gives the highest focusing gain. For air-coupled excitation, a focused spark source with an ellipsoidal reflector is employed to excite stress waves in concrete. Numerical simulations and available nonlinear computer code (KZKTexas) are employed to investigate the reflector geometry that gives the highest stress wave excitation in solids. An acoustical muffler that works with the focused spark source is proposed to decrease the spark-induced noise level. The effect of source receiver spacing on received IE signals is studied. Simulated wavefield demonstrates that the mode shape of IE surface displacement distribution along the radial direction matches the Bessel function of the first kind (J0). Numerical 3D simulation results show the relation between focused IE signals and source receiver spacings, and indicate the spacing should be minimized to obtain better focused IE signal strength. Air-coupled IE test using through transmission setup is also investigated. / text

Non-destructive testing (NDT) plays an important role today in condition assessment of civil infrastructure. Among these NDT methods, the Impact-Echo (IE) method is widely used to determine the thickness of a plate structure and locate delaminations in concrete. The conventional IE test uses a contact impact source and a contact sensor, which limits the scanning speed. Recent studies show the feasibility of applying the air-coupled sensing technology to the IE test. With the contact requirement eliminated, a fully air-coupled NDT system can be realized to achieve rapid scanning on large scale structures. In this dissertation, the air-coupled IE test is first simulated using 2D finite element models. The numerical simulation results are validated by experimental measurements. It is shown that the airborne IE mode is a quasi-plane wave in air. A parabolic reflector is proposed to focus the airborne IE wave and amplify the air-coupled IE test signals. The focusing effect is validated by experimental results. By applying a parabolic reflector to the air-coupled sensor, it is found that large sensor lift-off height and source-receiver spacing can be used in the air-coupled IE test. The geometry of the parabolic reflector and source-receiver spacing are optimized using numerical simulations. A focused spark source is proposed as a non-contact source for the fully air-coupled test system. The spark source is first calibrated in an anechoic chamber. The feasibility of using the focused spark source for stress wave excitation is validated by experiments. A fully air-coupled testing system is realized by combining the air-coupled sensor and the air-coupled source. Experimental studies show that this system can measure surface wave and the IE mode. The fully air-coupled system is tested using a conventional IE test setup and a through transmission test setup. An acoustic muffler is introduced to suppress the acoustic noise from the spark source. Several advanced signal processing techniques to reduce the acoustic noises are also investigated. The air-coupled sensor has been adopted on a crawler NDT system for concrete inspection in a noisy field environment. / text