In laser materials processing, the direct measurement and characterization of material and process depth is traditionally a diffcult task. This is particularly difficult when such information needs to be obtained in real-time for feedback and dynamic analysis applications. This thesis outlines a novel method and apparatus for real-time depth measurement during laser processes such as welding, drilling, cutting and ablation called inline coherent imaging (ICI). The approach borrows the coherent imaging ideas from the primarily medical field of optical coherence tomography and adapts them to the new application. Without requirements for flawless image quality and limitations on sample exposure the design is free to emphasize speed in acquisition and processing. Furthermore, the imaging optics are specialized for compatibility with off-the-shelf beam delivery systems. Several generations of the imaging technique and relevant design equations are described and shown and realized. Also described is the design and construction of two laser processing stations used for testing ICI in macro- and micro-processing applications. A variety of applications for ICI in the understanding of percussion drilling and welding of metals and other industrial materials are discussed. The imaging technique is further extended to provide manual and fully automatic closed-loop control of drilling and ablation processes in industrial materials. Finally, some important applications of ICI in the processing of bone in both open and closed-loop configurations are demonstrated. / Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2012-11-04 15:34:14.379

The report examines the factors which may be a contributing cause to the problems that are present when ferritic stainless steel are eddy current tested in a warm condition. The work is carried out at Fagersta Stainless AB in Fagersta which manufactures stainless steel wire. In the rolling mill there is an eddy current equipment for detection of surface defects on the wire. The ferritic stainless steels cause a noise when testing and this noise complicates the detection of defects.Because of this, a study was made of how the noise related to factors such as steel grade, temperature, size and velocity. By observing the signal and with the possibilities to change the equipment settings the capability to let a signal filter reduce the noise level were evaluated. Theories about the material's physical properties have also been included, mainly the magnetic properties, electrical conductivity and the material's tendency to oxidize.Results from the tests show that a number of factors do not affect the inductive test significantly and to use a filter to reduce the noise level does not seem to be a viable option. The level of noise does not relate to the presence of superficial particles in form of oxides.The ferritic stainless steels showed some difference in noise level. Which noise level there was did match well with the steels probability for a precipitation of a second phase, and precipitation of austenite may in this case contribute to noise when using an eddy current instrument.The noise is probably due to some physical material property that varies within the thread.

The quantitative nondestructive evaluation (NDE) of cement-based materials is a critical area of research that is leading to advances in the health monitoring and condition assessment of the civil infrastructure. Ultrasonic NDE has been implemented with varying levels of success to characterize cement-based materials with complex microstructure and damage. A major issue with the application of ultrasonic techniques to characterize cement-based materials is their inherent inhomogeneity at multiple length scales. Ultrasonic waves propagating in these materials exhibit a high degree of attenuation losses, making quantitative interpretations difficult. Physically, these attenuation losses are a combination of internal friction in a viscoelastic material (ultrasonic absorption), and the scattering losses due to the material heterogeneity. The objective of this research is to use ultrasonic attenuation to characterize the microstructure of heterogeneous cement-based materials. The study considers a real, but simplified cement-based material, cement paste - a common bonding matrix of all cement-based composites. Cement paste consists of Portland cement and water but does not include aggregates. First, this research presents the findings of a theoretical study that uses a set of existing acoustics models to quantify the scattered ultrasonic wavefield from a known distribution of entrained air voids. These attenuation results are then coupled with experimental measurements to develop an inversion procedure that directly predicts the size and volume fraction of entrained air voids in a cement paste specimen. Optical studies verify the accuracy of the proposed inversion scheme. These results demonstrate the effectiveness of using attenuation to measure the average size, volume fraction of entrained air voids and the existence of additional larger entrapped air voids in hardened cement paste. Finally, coherent and diffuse ultrasonic waves are used to develop a direct relationship between attenuation and water to cement (w/c) ratio. A phenomenological model based on the existence of fluid-filled capillary voids is used to help explain the experimentally observed behavior. Overall this research shows the potential of using ultrasonic attenuation to quantitatively characterize cement paste. The absorption and scattering losses can be related to the individual microstructural elements of hardened cement paste. By taking a fundamental, mechanics-based approach, it should be possible to add additional components such as scattering by aggregates or even microcracks in a systematic fashion and eventually build a realistic model for ultrasonic wave propagation study for concrete.

Historical Turkish baths still keeping their functional systems represent their original architectural and building technologies. Studies on the functional systems of historical baths are therefore needed to discover such technologies and to maintain them in working order. This study was conducted on a 15th century historical Turkish bath, Seng&uuml / l Hamami, in Ankara for assessment of its water supply and drainage systems. These systems comprised of hot and cold-water supply, wastewater and rainwater drainage, were examined in terms of their adequacy, capacity and faults. Comparisons were made with certain other historical Turkish baths to determine their original water storage and consumption capacities. The investigations were made by using non-destructive methods. Among them, the calculation methods used for discharge capacity assessment of drainage systems in Seng&uuml / l Hamami and consumption capacities of its water supply system were adapted and developed from the calculation methods used for contemporary buildings. Serious dampness problems arising from certain roof drainage faults were identified in the building. The wastewater collection and discharge system was found to have serious problems due to improper grading and inadequate flow dimensions of drains and wastewater channels. The ideal situation for the improvement of discharge systems was discussed together with some suggestions on the urgent remedial interventions, preventive measures and future improvements. The methods developed in this study were considered useful for the calculation of adequacy and capacity of wastewater and roof drainage systems and of water storage and consumption capacities of water supply system for the other historical baths.

<p>The purpose of this work is to contribute to a process formaking buildings with good function and to avoid prematurefaults.</p><p>The design, construction and installation of low-slopedroofs are important parts of creating a durable building. Mostof the leakages in low-sloped roofs occur where materials withdifferent thermomechanical properties are joined together. Withbetter knowledge about these joints, the expected service lifecould better be estimated. Common roofing materials onlow-sloped roofs are roof membranes.</p><p>To avoid damages and to minimise energy consumption thedetection of air and water leaks is essential. It can bedifficult to localise a leak in e.g. a roof since water canflow far within the construction. Leakage detection can beapplied both as a quality assurance method after installationof low-sloped roofs and as field inspection methods. Theleakage detection can also be extended to terrace slabs and thewhole building envelope.</p><p>To investigate the strength of jointsbetween sheet metaland roofing membranes, several small-scale tests and somelarge-scale tests were performed. The test methods weredeveloped to match the loads that can be expected on this kindof joints.</p><p>A number of water leak-detection methods were evaluatedthrough application on test roofs. Some of the methods todetect leaks on low-sloped roofs can also be used to detect airleakage in other parts of the building envelope. To develop andevaluate air leak-detection procedures, selected methods wereused in two case studies.</p><p>The circumstances regarding welding of the material jointswere found to have great impact on the strength. The roofshould be designed so no long-term strain will appear since acomparatively low stress may damage the joint over time.</p><p>The performance of the leak-detection methods depends on theroofing material. All methods tested were an improvementcompared to visual inspections. Different recommendedapproaches for leakage detection and quality control is given.The case studies show that air leakage detection could beperformed with good accuracy. The potential difference methodcould without doubt be a tool for leakage localisation inwaterproofing layers both on roofs and in terrace slabs.</p><p><b>Keywords:</b>Roofing, roof membrane, durability,waterproofing, leakage, wind-load, non-destructive testing,NDT, BSL4, BSL3, air leakage, building envelope</p>

<p>Composite structures can lower the weight of an airliner significantly. The increased production cost, however, requires the application of cost-effective design strategies. Hence, a comparative value is required which is used for the evaluation of a design solution in terms of cost and weight. The direct operating cost (DOC) can be used as this comparative value; it captures all costs that arise when the aircraft is flown. In this work, a cost/weight optimization framework for composite structures is proposed. It takes into account manufacturing cost, non-destructive testing cost and the lifetime fuel consumption based on the weight of the aircraft, thus using a simplified version of the DOC as the objective function.</p><p>First, the different phases in the design of an aircraft are explained. It is then focused on the advantages and drawbacks of composite structures, the design constraints and allowables, and non-destructive inspection. Further, the topics of multiobjective optimization and the combined optimization of cost and weight are addressed. Manufacturing cost can be estimated by means of different techniques; here, feature-based cost estimations and parametric cost estimations proved to be most suitable for the proposed framework. Finally, a short summary of the appended papers is given.</p><p>The first paper contains a parametric study in which a skin/stringer panel is optimized for a series of cost/weight ratios (weight penalties) and material configurations. The weight penalty, defined as the specific lifetime fuel burn, is dependent on the fuel consumption of the aircraft, the fuel price and the viewpoint of the optimizer. It is concluded that the ideal choice of the design solution is neither low-cost nor low-weight but rather a combination thereof.</p><p>The second paper proposes the inclusion of non-destructive testing cost in the design process of the component, and the adjustment of the design strength of each laminate according to the inspection parameters. Hence, the scan pitch of the ultrasonic testing is regarded as a variable, representing an index for the (guaranteed) laminate quality. It is shown that the direct operating cost can be lowered when the quality level of the laminate is assigned and adjusted in an early design stage.</p>

In recent years, bridge foundations have been in the spotlight throughout the nation. Bridges built over running water are susceptible to erosion or scour around their foundations. The reduction in load capacity to piers and abutments pose a safety risk to highway motorists. It has become necessary for engineers to examine and monitor these "scour critical" bridges. The difficulty arises with subsurface foundations of which very little is known about their construction. Hence, the methods applied to analyzing "Unknown Foundations" have become a necessary topic of research. This thesis explores a method to determine foundation lengths. Similar to Sonic Echo / Impulse Response, this procedure measures reflected shock waves sent through concrete pilings. The technique is non-destructive in nature and is performed near the surface of the foundation. The test is performed on the side of the exposed piling. Current methods are limited by the fact that the tops of most pilings are inaccessible due to pilecaps or beams. Often times, pilings are embedded in stiff soils, which have a dampening effect on the stress waves. This thesis employs a method of analysis that will overcome such limitations and provide engineers with another tool to determine subsurface foundation lengths.

X-Ray Diffraction Contrast Tomography (DCT) is a recently developed, non-destructive synchrotron imaging technique which characterizes microstructure and grain orientation in polycrystalline materials in three dimensions (3D). By combining it with propagation based phase contrast tomography (PCT) it is for the first lime possible to observe in situ the 3D propagation behavior of short fatigue cracks (SFCs) within a set of fully characterized grains (orientation and shape). The combined approach, termed 3D X-ray Tomography of short cracks and Microstructure (3DXTSM), has been developed on the metastable beta titanium alloy "Beta21S". A large part of this work deals with the development of the 3DXTSM methodology. In the combined dataset, each point on the 3D fracture surface can be associated with a multidimensional data structure containing variables describing the grain orientation, the local fracture surface normal and the propagation history. The method uses a surface mesh composed of triangles that describes the crack (in other words: the fracture surface) in the last propagation state measured. Grain orientations, crack fronts, local growth rates and grain boundaries can be visualized by assigning colors to this mesh. The data structure can be interrogated in a number of different ways. Tools for extracting pole figures and pole density distribution functions have been implemented. An algorithm was developed that is capable of measuring the 3D local growth rate of a crack containing branches. The accuracy of the grain boundaries as reconstructed with OCT was evaluated and the elastic constants of Beta21S were determined.

This thesis reports on the application of ground penetrating radar (GPR) as a non-destructive technique for the monitoring of ring separation in brick masonry arch bridges. In addition, research is reported on the assessment of the clay capping layer often used in construction as a waterproof backing to arches. The thrust of the research is numerical modelling, verified by large laboratory experiments. Due to the heterogeneity of these structures, the resultant signals from the interaction between the GPR system and the bridge are often complex and hence, hard to interpret. This highlighted the need to create a GPR numerical model that would allow the study of the attributes of reflected signals from various targets within the structure of the bridge. The GPR numerical analysis was undertaken using the finite-difference time-domain (FDTD) method. Since micro regions in the bridge structure need to be modelled, the introduction of subgrids of supporting finer spatial resolution into the standard FDTD method was considered essential in order to economise on the required computational resources. In the main part of this thesis, it is demonstrated how realistic numerical modelling of GPR using the FDTD method could greatly benefit from the implementation of subgrids into the conventional FDTD mesh. This is particularly important when (a) parts of the computational domain need to be modelled in detail (i.e., ring separation between the mortar layers and the brick units, which is the case studied in this thesis); and also (b) when there are features or regions in the overall computational mesh with values of high relative permittivity supporting propagation of waves at very short wavelengths. A scheme is presented that simplifies the process of implementing these subgrids into the traditional FDTD method. This scheme is based on the combination of the standard FDTD method and the unconditionally stable alternating-direction implicit (ADI) FDTD technique. Given that ADI-FDTD is unconditionally stable, its time-step can be set to any value that facilitates the accurate calculation of the electromagnetic fields. By doing so, the two grids can efficiently communicate information across their boundary without requiring to use a time-interpolation scheme. The performance of ADI-FDTD subgrids when implemented into the traditional FDTD method is discussed herein. The developed algorithm can handle cases where the subgrid crosses dielectrically inhomogeneous and/or conductive media. In addition, results from the comparison between the proposed scheme and a commonly employed purely FDTD subgridding technique are presented. After determination of the optimum ADI-FDTD scheme, numerical experiments were conducted and calibrated using GPR laboratory experiments. Good correlations were obtained between the numerical experiments and the actual GPR experiments. It was shown both numerically and experimentally that significant mortar loss between the masonry arch rings can be detected. Dry hairline delaminations between the mortar and the brick masonry are difficult to detect using standard GPR procedures. However, hairline faults containing water produce distinct and detectable GPR responses. In addition, the clay layer was successfully identified and its thickness calculated to a satisfactory accuracy.

In this thesis, two ultrasonic timing methods are used in order to investigate the accuracy and reliability of measurements for surface breaking cracks having different orientations and heights. Also the best applicable measurement technique is searched by comparing the received test results. These methods are the Time of Flight Diffraction (TOFD) Method using diffraction of longitudinal waves and another method using the reflection of shear waves from the crack tips. In order to simulate and measure the height of surface breaking cracks three sets of test blocks from steel, and two sets of wedges from plexiglas material are manufactured. Also several probes having frequencies of 2Mhz, 4Mhz, 5Mhz and angles of 45o and 70o are used. Some test procedures are created to make realistic comparisons between the test results and the ones found by previous studies in literature. The results are compared according to the standard deviations of errors in crack height measurements and it is found that the depth, orientation of defects and the frequency of probes have considerable affect on the results. With wider probe angles and higher frequencies of probes to some extent the errors are observed to be running low and the height of cracks could be measured closer to the original size. The amount of the errors is increased in measurements with the increasing angle of cracks. The results of both methods are found to be very satisfactory. A range of &plusmn / 0.5 mm for means of error from the original vertical crack heights is determined. The results agree with the previous studies.