No description available.

No description available.

No description available.

No description available.

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. 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. 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. 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. / QC 20101112

<p>Aging public infrastructure in North America continues to challenge engineers and scientists to develop repair and rehabilitation strategies that are practical, durable and cost effective. Of specific interest is the state of concrete and concrete repair in buildings and civil engineering infrastructures that are in deteriorating condition. In particular, cracks pose a threat to the durability and ultimately the structural integrity of concrete. Cracks in concrete may form for several reasons, e.g. plastic shrinkage, thermal contraction, mechanical loading or as a result of overloading. Once formed, cracks present a combination of problems to the service life and performance of the structure. Therefore cracks must be repaired for the following reasons: to prevent the ingress of deleterious agents such as water, other liquids, vapour, gas, chemicals and biological agents; to either restore or increase the structural load-bearing capacity of the cracked concrete member; to restore the aesthetic condition of the structure.</p> <p>The effectiveness of two different repair methods, crack injections and cementitious overlays, were examined. Two repair materials, a low viscosity epoxy and polyurethane were injected into the cracks, and a thin polymer-modified cementious overlay was applied on the cracked surface. Two types of cement were used, an ordinary Portland cement and a blended cement with 8% silica fume. The specimen properties were evaluated using non-destructive testing, prior to being subjected to a series of freeze-thaw conditioning regimes. From the experimental program, it was determined that the epoxy injection repair was more effective in restoring the air tightness than the thin overlay. The polyurethane material was unsuccessful. Following the freeze-thaw regimes, an overall improvement of conditions for all three repairs was observed, with the cementitious overlay seeing the greatest improvement in air tightness. These results indicate that the on-going cement hydration mechanism had a greater effect on the performance in comparison to the deleterious effects of the environmental loads.</p> / Master of Applied Science (MASc)

Proper design of bridge structures requires an appreciation for the possible failure mechanisms that can develop over the lifetime of the bridge, many of which are related to natural hazards. For example, scour is one of the most common causes of bridge failures. Scour occurs due to the erosion of soil and sediment within a channel with flowing water. During a flood event, the extent of scour can be so great that it can destabilize an existing bridge structure. In order to evaluate the scour potential of a bridge, it is necessary to have information regarding the substructure, particularly the bridge foundations. However, as of 2011 there are more than 40,000 bridges across United States with unknown foundations. Generally for these bridges there are no design or as-built plans available to show the type, depth, geometry, or materials incorporated into the foundations. Several non-destructive testing (NDT) methods have been developed to evaluate these unknown foundations. The primary objective of this research is to identify the most current and widely used NDT methods for determining the embedment depth of unknown bridge foundations and to compare these methods to an ultrasonic P-wave reflection imaging system. The ultrasonic P-wave reflection system has tremendous potential to provide more information and address several short-comings of other NDT methods. A laboratory study was initiated to explore various aspects related to the P-wave system performance, in order to characterize the limitations of the system in evaluation of unknown foundations prior to deployment in field studies. Moreover, field testing was performed using the P-wave system and a number of the current NDT methods at two selected bridge foundations to allow comparison between the results. / Civil Engineering

Drilled shafts are deep foundation elements created by excavating cylindrical shafts into the ground and filling them with concrete. Given the types of structures they support, failure to meet their performance criteria can jeopardize public safety and cause severe financial losses. Consequently, quality control measures are warranted to ensure these foundations meet design specifications, particularly with respect to their structural integrity and geotechnical capacity. Due to their inaccessibility, non-destructive testing (NDT) techniques have received much attention for drilled shaft quality control. However, there are limitations in the NDT tools currently used for structural integrity testing. Moreover, there is no current NDT tool to evaluate conditions underlying drilled shaft excavations and aid in verifying geotechnical capacity. The main objective of this research is to examine the development of new NDT methodologies to address some of the limitations in the inspection of drilled shaft structural integrity and geotechnical conditions underlying their excavations. The use of stress waves in large laboratory models is first examined to evaluate the performance of ray-based techniques for detecting anomalies. The study then continues to investigate the improvements offered by using a full waveform inversion (FWI) approach to analyze the stress wave data. A hybrid, multi-scale FWI workflow is recommended to increase the chance of the convergence of the inversion algorithms. Additionally, the benefits of a multi-parameter FWI are discussed. Since FWI is computationally expensive, a sequential optimal experimental design (SOED) analysis is proposed to determine the optimal hardware configurations for each application. The resulting benefit-cost curves from this analysis allow for designing an NDT survey that matches the available resources for the project. / Civil Engineering

A change in a part's response to vibrations can be measured and utilized as a non-destructive testing method to detect deviations in the part's materials or geometry through processes such as laser acoustic resonance spectroscopy. This work focuses on leveraging vibration resonance to detect flaws in prints produced through additive friction stir deposition that arise through environmental contamination. More specifically, the use case considered is the printing of AA7075 in an iron oxide rich environment, where iron oxide dust or powder could accidentally be stirred into the printed material creating a print flaw. The modeling of printed parts contaminated with iron oxide to predict their natural frequencies is examined. Two different finite element models are discussed, which were created to represent contamination flaws with and without voids. The first model considers the case where a part is void-free. In this case, the model assumes a solid, homogeneous material condition in the stir region. The second model considers the case where voids are present in the part. This model leverages x-ray computed tomography data to build a representative mesh. These models show that with a well-understood part and corresponding flaw, it is possible to predict the natural frequencies of a flawed part. By leveraging the part vibration measurements and model predictions of known defects, it may be possible to gain insights into and characterize unknown print flaws. / Master of Science / An important aspect of product or part creation is checking consistency between parts. Methods that can verify a part is good without damaging the part are valuable, especially when only a few parts are being made, or there is a high chance of something going wrong. One way of checking a part is to shake it and watch how it reacts and bends. If there is a difference in how a part reacts to the shaking from a known good part, then there is a problem. This work examines creating computer simulations to predict how a part should react to shaking when it is good and how it should react when it has flaws. This work considers flaws caused by debris from the environment during part creation. This work also considers whether such debris causes holes or voids to form in the parts and conducts predictions with the holes included.

The focus in this work is on the use of ultrasonic testing as a method for inspecting components manufactured through additive manufacturing (AM) processes. The research is rooted in the need for effective non-destructive testingtechniques that can adapt to the unique challenges posed by AM-produced materials, including complex defect geometries and surface conditions. Ultrasonic testing is a versatile form of non-destructive testing, offering theability to detect internal flaws, such as voids, cracks, and inclusions, with highprecision and in real-time. Unlike many competing methods, ultrasonic testing works on most types of materials. Ultrasonic testing has been applied forinspection purposes for a long time. Now with emerging manufacturing methods, there is a need for evaluation techniques to keep up with this development.New data processing algorithms open up possibilities of extracting more information from the acquired signal. The thesis provides a review of UT’s capabilities in detecting and classifyingdefects within AM components, with a particular emphasis on the subtletiesintroduced by the layer-by-layer construction method inherent to AM technologies. The work advances development and validation of simulation modelsaimed at predicting the ultrasonic response from manufactured defects. Thesemodels are crucial for understanding the interaction between ultrasound wavesand material anomalies, offering insights into the potential for enhanced defectdetection strategies. The research also explores the practical case of integrating UT into the quality assurance processes by relying on mathematical simulation rather than experimental data. The findings suggest avenues for the refinement of creation of inspection procedure, including the the use of meta-models to cheaply acquire worst-case scenario defects, to better accommodate the specificities of AM materials. / Den här avhandlingen handlar om ultraljudsprovning av additivt tillverkade metalkomponenter. Ultraljud är en av flera metoder som används för att detektera defekter i komponenter utan att förstöra komponenten i processen. Samlingsnamnet för dessa metoder är oförstörande provning. Oförstörande provning är en viktig pusselbit i samhällets säkerhet då det möjliggör identifiering och utvärdering av potentiella defekter i material, vilket förebygger olyckor och strukturella fel. Vidare är det en viktig del inom hållbar utveckling genom att maximera nyttjandet av komponenter då dessa inte behöver ersättas med ett överdrivet försiktigt underhållsintervall. Ultraljudsprovning fungerar genomatt ultraljud introduceras in i en komponent, varefter en givare registrerar ekon som uppstår när ljudvågorna interagerar med eventuella defekter. Detta möjliggör både lokalisering och storleksbedömning av defekter, t.ex. sprickor, bindfel eller porer. Resultaten av den här avhandlingen syftar till att ge förutsättningar för att förbättra tolkningen av dessa signaler, dels genom att experimentellt validera simuleringsmodeller, samt tillämpning av dessa modeller för att utveckla en metamodell för att prediktera amplitudsvaret från en mängd defekter inom en viss parameterrymd. Med verktyg som detta kan billigare inspektionsprocedurer möjliggöras genom att man till större del kan förlita sig på simulering av signaler snarare än att skaffa stort underlag med experimentell data. / <p>Paper A, B and C are not included in the eletronic version. Paper C is under submission.</p>