Design for Producibility in Fabricated Aerospace Components - A framework for predicting and controlling geometrical variation and weld quality defects during multidisciplinary design

In the aerospace industry, weight reduction has been one of the key factors in making aircraft more fuel efficient in order to satisfy environmental demands and increase competitiveness. One strategy adopted by aircraft component suppliers to reduce weight has been fabrication, in which small cast or forged parts are welded together into a final shape. Fabrication increases design freedom due to the possibility of configuring several materials and geometries, which broadens out the design space and allows multioptimization in product weight, performance quality and cost. However, with fabrication, the number of assembly steps and the complexity of the manufacturing process have increased. The use of welding has brought to the forefront important producibility problems related to geometrical variation and weld quality.The goal of this research is to analyze the current situation in industry and academia and propose methods and tools within Engineering Design and Quality Engineering to solve producibility problems involving welded high performance integrated components. The research group “Geometry Assurance and Robust Design” at Chalmers University of Technology, in which this thesis has been produced, has the objective to simulate and foresee geometrical quality problems during the early phases of the product realization process to allow the development of robust concepts and the optimization of tolerances, thus solving producibility problems. Virtual manufacturing is a key within the multidisciplinary design process of aerospace components, in which automated processes analyze broad sets of design variants to trade-off requirements among various disciplines. However, as studied in this thesis, existing methods and tools to analyze producibility do not cover all aspects that define the quality of welded structures. Furthermore, to this day, not all phenomena related to welding can be virtually modelled. Understanding causes and effects still relies on expert judgements and physical experimentation to a great deal. However, when it comes to assessing the capability of many geometrical variants, such an effort might be costly. This deficiency indicates the need for virtual assessment methods and systematic experimentation to analyze the producibility of the design variants and produce process capability data that can be reused in future projects.To fulfill that need, this thesis provides support to designers in assessing producibility by virtually and rapidly predicting the welding quality of a large number of product design variants during the multidisciplinary design space process of fabricated aerospace components.The first step has been to map the fabrication process during which producibility problems might potentially occur. The producibility conceptual model has been proposed to represent the fabrication process in order to understand how variation is originated and propagated. With this representation at hand, a number of methods have been developed and employed to provide support to: 1) Identify and 2) Measure what affects producibility; 3) Analyze the effect of the interaction between factors that affect producibility and 4)Predict producibility. These activities and methods constitute the core of the proposed Design for Producibility framework. This framework combines specialized information about welding problems (know-hows), and inspection, testing and simulation data to systematically predict and evaluate the welding producibility of a set of product design variants. Through this thesis, producibility evaluations are no longer limited to a single geometry and the study of the process parameter window. Instead, a set of geometrical variants within the design space can be analyzed. The results can be used to perform optimization and evaluate trade-offs among different disciplines during design space exploration and analysis, thus supporting the multidisciplinary design process of fabricated (welded) aerospace components

Improvement of safety operating conditions in overhead conductors based on ampacity modeling using artificial neural networks

Thermal ratings are usually considered for planning the operating conditions for overhead lines and are usually obtained with static parameters. These conditions can be improved using dynamic ratings based on the region weather forecasts, and this improvement can be ever higher when a local prediction is performed at the point where the line is located. In this work, a model based on artificial neural networks techniques is applied to predict the ampacity property of a transmission overhead line, in order to adjust and optimize the operation point of the grid under safety conditions. These predictions are calculated for a time horizon of 24 hours and are validated with actual conditions of a real overhead line monitored by sensors. With the conclusion that applying the selected model, the operational security of the conductor can be improved, passing from a 17.82% of overheating conditions to only a 3.91%.This work is financially supported by the Ministerio de Economía, Industria y Competitividad, Spain, under the project DPI2016-77215-R (AEI/FEDER, UE)

Individualizing assembly processes for geometric quality improvement

Dimensional deviations are a consequence of the mass production of parts. These deviations can be controlled by tightening production tolerances. However, this solution is not always desired because it usually increases production costs. The availability of massive amounts of data about products and automatized production has opened new opportunities to improve products\u27 geometrical quality by individualizing the assembly process. This individualization can be conducted through several techniques, including selective assembly, locator adjustments, weld sequence optimization, and clamping sequence optimization in a smart assembly line for spot-welded sheet metal assemblies. This study focuses on two techniques of individualizing the assembly process, selective assembly, and individualized locator adjustments in assembly fixtures. The existing studies and applications of these methods are reviewed, and the research gaps are defined. The previous applications of selective assembly are limited to linear and rigid assemblies. This study develops the application of selective assembly for sheet metal assemblies. This research addresses another research gap regarding the selective assembly of sheet metals by reducing the calculation cost associated with this technique. This study also develops a new locator adjustment method. This method utilizes scanned geometries of mating parts to predict the required adjustments. Afterward, a method for individualized adjustments is also developed. Considering applied and residual stresses during the assembly process as constraints is another contribution of this research to locator adjustments. These methods are applied to three industrial sample cases and the results evaluated. The results illustrate that individualization in locator adjustments can increase geometrical quality improvements three to four times.Accumulation of the potential improvements from both techniques in a smart assembly line is also evaluated in this study. The results indicate that combining the techniques may not increase the geometrical quality significantly relative to using only individualized locator adjustments.A crucial factor in the achievable improvements through individualization is the utilized assembly fixture layout. This study develops a method of designing the optimal fixture layout for sheet metal assemblies. Different design and production strategies are investigated to acquire the maximum potential for geometrical improvements through individualization in self-adjusting smart assembly lines

Development of a multi-objective optimization algorithm based on lichtenberg figures

This doctoral dissertation presents the most important concepts of multi-objective optimization and a systematic review of the most cited articles in the last years of this subject in mechanical engineering. The State of the Art shows a trend towards the use of metaheuristics and the use of a posteriori decision-making techniques to solve engineering problems. This fact increases the demand for algorithms, which compete to deliver the most accurate answers at the lowest possible computational cost. In this context, a new hybrid multi-objective metaheuristic inspired by lightning and Linchtenberg Figures is proposed. The Multi-objective Lichtenberg Algorithm (MOLA) is tested using complex test functions and explicit contrainted engineering problems and compared with other metaheuristics. MOLA outperformed the most used algorithms in the literature: NSGA-II, MOPSO, MOEA/D, MOGWO, and MOGOA. After initial validation, it was applied to two complex and impossible to be analytically evaluated problems. The first was a design case: the multi-objective optimization of CFRP isogrid tubes using the finite element method. The optimizations were made considering two methodologies: i) using a metamodel, and ii) the finite element updating. The last proved to be the best methodology, finding solutions that reduced at least 45.69% of the mass, 18.4% of the instability coefficient, 61.76% of the Tsai-Wu failure index and increased by at least 52.57% the natural frequency. In the second application, MOLA was internally modified and associated with feature selection techniques to become the Multi-objective Sensor Selection and Placement Optimization based on the Lichtenberg Algorithm (MOSSPOLA), an unprecedented Sensor Placement Optimization (SPO) algorithm that maximizes the acquired modal response and minimizes the number of sensors for any structure. Although this is a structural health monitoring principle, it has never been done before. MOSSPOLA was applied to a real helicopter’s main rotor blade using the 7 best-known metrics in SPO. Pareto fronts and sensor configurations were unprecedentedly generated and compared. Better sensor distributions were associated with higher hypervolume and the algorithm found a sensor configuration for each sensor number and metric, including one with 100% accuracy in identifying delamination considering triaxial modal displacements, minimum number of sensors, and noise for all blade sections.Esta tese de doutorado traz os conceitos mais importantes de otimização multi-objetivo e uma revisão sistemática dos artigos mais citados nos últimos anos deste tema em engenharia mecânica. O estado da arte mostra uma tendência no uso de meta-heurísticas e de técnicas de tomada de decisão a posteriori para resolver problemas de engenharia. Este fato aumenta a demanda sobre os algoritmos, que competem para entregar respostas mais precisas com o menor custo computacional possível. Nesse contexto, é proposta uma nova meta-heurística híbrida multi-objetivo inspirada em raios e Figuras de Lichtenberg. O Algoritmo de Lichtenberg Multi-objetivo (MOLA) é testado e comparado com outras metaheurísticas usando funções de teste complexas e problemas restritos e explícitos de engenharia. Ele superou os algoritmos mais utilizados na literatura: NSGA-II, MOPSO, MOEA/D, MOGWO e MOGOA. Após validação, foi aplicado em dois problemas complexos e impossíveis de serem analiticamente otimizados. O primeiro foi um caso de projeto: otimização multi-objetivo de tubos isogrid CFRP usando o método dos elementos finitos. As otimizações foram feitas considerando duas metodologias: i) usando um meta-modelo, e ii) atualização por elementos finitos. A última provou ser a melhor metodologia, encontrando soluções que reduziram pelo menos 45,69% da massa, 18,4% do coeficiente de instabilidade, 61,76% do TW e aumentaram em pelo menos 52,57% a frequência natural. Na segunda aplicação, MOLA foi modificado internamente e associado a técnicas de feature selection para se tornar o Seleção e Alocação ótima de Sensores Multi-objetivo baseado no Algoritmo de Lichtenberg (MOSSPOLA), um algoritmo inédito de Otimização de Posicionamento de Sensores (SPO) que maximiza a resposta modal adquirida e minimiza o número de sensores para qualquer estrutura. Embora isto seja um princípio de Monitoramento da Saúde Estrutural, nunca foi feito antes. O MOSSPOLA foi aplicado na pá do rotor principal de um helicóptero real usando as 7 métricas mais conhecidas em SPO. Frentes de Pareto e configurações de sensores foram ineditamente geradas e comparadas. Melhores distribuições de sensores foram associadas a um alto hipervolume e o algoritmo encontrou uma configuração de sensor para cada número de sensores e métrica, incluindo uma com 100% de precisão na identificação de delaminação considerando deslocamentos modais triaxiais, número mínimo de sensores e ruído para todas as seções da lâmina

NASA Tech Briefs, August 2012

Topics covered include: Mars Science Laboratory Drill; Ultra-Compact Motor Controller; A Reversible Thermally Driven Pump for Use in a Sub-Kelvin Magnetic Refrigerator; Shape Memory Composite Hybrid Hinge; Binding Causes of Printed Wiring Assemblies with Card-Loks; Coring Sample Acquisition Tool; Joining and Assembly of Bulk Metallic Glass Composites Through Capacitive Discharge; 670-GHz Schottky Diode-Based Subharmonic Mixer with CPW Circuits and 70-GHz IF; Self-Nulling Lock-in Detection Electronics for Capacitance Probe Electrometer; Discontinuous Mode Power Supply; Optimal Dynamic Sub-Threshold Technique for Extreme Low Power Consumption for VLSI; Hardware for Accelerating N-Modular Redundant Systems for High-Reliability Computing; Blocking Filters with Enhanced Throughput for X-Ray Microcalorimetry; High-Thermal-Conductivity Fabrics; Imidazolium-Based Polymeric Materials as Alkaline Anion-Exchange Fuel Cell Membranes; Electrospun Nanofiber Coating of Fiber Materials: A Composite Toughening Approach; Experimental Modeling of Sterilization Effects for Atmospheric Entry Heating on Microorganisms; Saliva Preservative for Diagnostic Purposes; Hands-Free Transcranial Color Doppler Probe; Aerosol and Surface Parameter Retrievals for a Multi-Angle, Multiband Spectrometer LogScope; TraceContract; AIRS Maps from Space Processing Software; POSTMAN: Point of Sail Tacking for Maritime Autonomous Navigation; Space Operations Learning Center; OVERSMART Reporting Tool for Flow Computations Over Large Grid Systems; Large Eddy Simulation (LES) of Particle-Laden Temporal Mixing Layers; Projection of Stabilized Aerial Imagery Onto Digital Elevation Maps for Geo-Rectified and Jitter-Free Viewing; Iterative Transform Phase Diversity: An Image-Based Object and Wavefront Recovery; 3D Drop Size Distribution Extrapolation Algorithm Using a Single Disdrometer; Social Networking Adapted for Distributed Scientific Collaboration; General Methodology for Designing Spacecraft Trajectories; Hemispherical Field-of-View Above-Water Surface Imager for Submarines; and Quantum-Well Infrared Photodetector (QWIP) Focal Plane Assembly

Increased precision in variation simulation by considering effects from temperature and heat

Every manufactured product deviates from the intended product. In a production series a number of noise sources will influence the product resulting in geometric variation. This variation leads to functional and aesthetical variation of the product. In geometry assurance, focus is on knowledge, methods, and tools to assure that the aesthetical and functional properties of a product are maintained for the non-nominal product. In this thesis, the effect of temperature and heat are considered in combination with variation. The relative ease of the manufacturing techniques and their flexible physical properties has made plastics an attractive alternative to metals in many industries. However, the thermal expansion of plastics is often much larger than metal, and is often of the size of other effects considered in geometry assurance. During assembly welding is a common joining technique. During welding a large amount of heat is induced into the welded assembly. It has previously been shown that welding deformations depend on positioning errors prior to welding. Therefore, in order to evaluate the robustness of an assembly that is welded; variation- and welding simulation need to be considered in combination. For this, methods and tools need to be developed. In this thesis an interview study is performed that reports current issues and problems when simulating for robustness in plastic design. This led to a framework for descriptive studies for robust plastic design where part-, assembly and functional assembly are considered as different levels of robustness. This study influenced the focus of this thesis toward temperature and heat. A study on the combination of thermal expansion and variation showed that geometric variation is dependent on temperature. In order to evaluate the effect of variation in combination with thermal expansion a method and tool to simulate the distribution of stresses was developed. Including contact modeling in variation simulation considering thermal expansion was shown to lead to long simulation times in some instances. Therefore, a new contact modeling approach for variation simulation has been developed and shown to reduce simulation time significantly. A study focusing on rattle and squeak simulation showed that this is a further area where thermal expansion for the non-nominal geometry needs to be considered. In order to enable variation simulation of welded assemblies, a method called the Steady state, Convex hull, Volumetric shrinkage-method (SCV-method) has been developed in a number of studies, giving reasonable results. Also, the influence of using clamps to reduce the effect of variation on weld induced deformation has been studied

Mass Production Processes

It is always hard to set manufacturing systems to produce large quantities of standardized parts. Controlling these mass production lines needs deep knowledge, hard experience, and the required related tools as well. The use of modern methods and techniques to produce a large quantity of products within productive manufacturing processes provides improvements in manufacturing costs and product quality. In order to serve these purposes, this book aims to reflect on the advanced manufacturing systems of different alloys in production with related components and automation technologies. Additionally, it focuses on mass production processes designed according to Industry 4.0 considering different kinds of quality and improvement works in mass production systems for high productive and sustainable manufacturing. This book may be interesting to researchers, industrial employees, or any other partners who work for better quality manufacturing at any stage of the mass production processes