21 research outputs found
Discrete Material Optimisation of Laminated Composite Structures using EAS and MITC Stabilised 4-Node Shell Element
No full textSimulation and optimisation methods are essential in the development process across several industries, such as wind turbines and aerospace. Computationally efficient optimisation techniques are crucial to designing complex laminated composite structures with the required functionalities, avoiding prototyping, reducing costs, and minimising time to market. This thesis uses gradient-based optimisation and the Discrete Material Optimisation (DMO) parameterisation to enhance the structural integrity of laminated composite structures. To improve the computational efficiency, analytical sensitivities of a 4-node shell element with Enhanced Assumed Strain (EAS) formulation and Mixed Interpolation of Tonsorial Components (MITC) are implemented into the MUltidisciplinary Synthesis Tool (MUST). Analytical sensitivities for buckling load factors are derived and implemented to address buckling-induced failure. Benchmark examples maximise the buckling load factors using the bound formulation and show a significant reduction in computation time compared to a 9-node isoparametric shell formulation. Given the absence of a universally accepted failure criterion for laminated composites, analytical sensitivity analyses are implemented for the maximum stress, maximum strain, and Tsai-Wu failure criteria. A benchmark example minimises the aggregate function for each of the failure criteria
Strength based optimization and test of fiber reinforced additively manufactured structures considering topology and fiber orientation
No full textStructural Optimization of Wind Turbine Blades Including Fatigue Constraints
Full text linkDesigning modern wind turbine blades is challenging due to the large scale and advanced materials utilized. Structural optimization has been shown to provide substantial benefits to both the design process and resulting design, however its application to blades is non-trivial, because of the required computational cost of solving optimization problems. Moreover, it is desirable to assess all structural failure criteria as part of the optimization, which is currently not possible, herein notably fatigue damage. The present work hence aims to further the structural optimization capabilities in application to wind turbine blades. Initial work concerns development of a fatigue optimization approach for general laminated composite structures within a gradient-based framework. The developed approach is later applied to optimize a blade root section model, along with buckling and static failure criteria, in context of both a thickness and multi-material and thickness parametrization. Significant reductions in material from the initial design accompany the attained variable-thickness laminates, emphasizing the potential of using the developed methods in the design process.Designing modern wind turbine blades is challenging due to the large scale and advanced materials utilized. Structural optimization has been shown to provide substantial benefits to both the design process and resulting design, however its application to blades is non-trivial, because of the required computational cost of solving optimization problems. Moreover, it is desirable to assess all structural failure criteria as part of the optimization, which is currently not possible, herein notably fatigue damage. The present work hence aims to further the structural optimization capabilities in application to wind turbine blades. Initial work concerns development of a fatigue optimization approach for general laminated composite structures within a gradient-based framework. The developed approach is later applied to optimize a blade root section model, along with buckling and static failure criteria, in context of both a thickness and multi-material and thickness parametrization. Significant reductions in material from the initial design accompany the attained variable-thickness laminates, emphasizing the potential of using the developed methods in the design process.<br/
Topology Optimization of General Structures with Anisotropic Fatigue Constraints
No full textDenne kandidatafhandling omhandler udvikling og implementering af topologioptimeringsmetoder til optimering af generelle 3D-printede metalkonstruktioner. Der gøres brug af en densitetsbaseret formulering, som sammenkobles med en lineær elastisk, statisk elementmetodemodel til analyse. Løsninger til topologioptimeringsproblemer i densitetsformulering er ikke veldefinerede og skal gøres geometrisk konsistente. Til dette formål benyttes filtrering, en metode oprindeligt brugt til signalbehandling. Typisk benyttes et sensitivitetsfilter eller et densitetsfilter - i den givne implementering foretrækkes densitetsfilteret. Filtermetoden udbygges ved brug af projektionsfiltre, der skal sikre en højere grad af diskretisering i designet. Disse anvendes efterfølgende til implementering af en metode til robust topologioptimering, som anvendes til at påtvinge produktionsbibetingelser i form af en veldefineret mindstestørrelse af de strukturelle detaljer. Ydermere forlænges elementdomænet for at tage højde for randbetingelsernes ukorrekte effekter på filtrering og mindstestørrelse. Optimeringskoncepter relaterende til spændingsanalyse diskuteres med særlig fokus på de medfølgende problemer; spændingers lokale definitioner og forekomsten af singulære optimum. Som løsning på disse problemer præsenteres henholdsvis aggregatfunktioner til at definere et globalt spændingsmål, som efterfølgende normaliseres med adaptiv skalering af bibetingelsen for at opnå højere nøjagtighed, og relaksering af spændingerne ved qp-metoden. Singulariteter kan fejlagtigt opstå i geometrien grundet skarpe kanter mellem elementerne, og løsningsmetoder hertil diskuteres. Formålet med at gennemgå spændingsaspekter er, at de skal bruges til at formulere en udmattelsesbetingelse til optimeringen. Generelle udmattelsesmodellering og -aspekter præsenteres. Udmattelses-optimeringsproblemer er komplicerede at løse grundet den ulineære formulering, og hertil præsenteres en effektiv skaleringsmetode, der sikrer høj nøjagtighed of hurtig optimering. Dette efterfølges af et grundigt studie af udmattelsesegenskaber for 3D-printede metaller, hvor det viser sig, at disse er væsentlig forringet sammenlignet med et tranditionelt fremstillet metal. Derudover forekommer der også anisotropisk opførsel i udmattelse som en bivirkning af processen. Dette benyttes til at udvikle en kontinuert funktion, der tager højde for den anisotropiske opførsel af det 3D-printede metal. Til at løse problemet benyttes førsteordens sensitivitetsbaserede metoder, hvilket anses som en effektiv løsning til disse komplekse optimeringsproblemer. Sensitiviteterne findes ved brug af adjoint design-sensitivitetsanalyse, hvilket er fordelagtigt når der er få bibetingelser - dette opnås ved brug af aggregatfunktioner. Efter præsentation af disse metoder løses flere eksempler, i både to og tre dimensioner, for at vise implikationerne ved brug og kombination af de forskellige metoder.Additively manufactured metals are special in that they behave close to isotropic in elasticity and monotonic strength, however their fatigue behavior is anisotropic and the fatigue strength is degraded. Designs generated by topology optimization have commonly been used as inspiration rather than realizing the actual design, primarily due to restrictions of the manufacturing methods. However, with additive manufacturing, it is possible to manufacture the highly complex designs common in topology optimization. An increased focus is therefore placed on design for manufacture, and for this purpose a novel smoothing approach is developed. Assuming isotropic stiffness and monotonic strength, the topology optimization is formulated as an extension to existing fatigue constraint functions using density-based topology optimization. An improved formulation for the fatigue damage is proposed to achieve a good combination of accuracy and computational efficiency, which has caused problems in previously published literature. These approaches and methods are demonstrated by solving both 2D and 3D problems, and the designs are subsequently verifiedusing commercial finite element software
Multi-material and thickness optimization of a wind turbine blade root section
Full text linkStructural optimization has been shown to be an invaluable tool for solving large-scale challenging design problems, and this work concerns such optimization of a state-of-the-art laminated composite wind turbine blade root section. For laminated composites structures, the key design parameters are material choice, fiber orientation, stacking sequence, and layer thickness, however a framework for treating these simultaneously in optimization, on the current wind turbine blade scale, has not been demonstrated. Thus, the motivation and novelty of the present work is providing and demonstrating a general gradient-based approach applicable to wind turbine blades, where the key design parameters and structural criteria, i.e., buckling, static strength, and fatigue damage, are considered for multiple design load cases. The optimization framework is based on a variation of the Discrete Material and Thickness Optimization approach, where the thickness is directly parametrized, allowing for appropriately treating the sandwich parts of the blade. It is demonstrated how optimization leads to a design consisting of complex variable-thickness laminates, a good overall distribution of the structural criteria in the model, and a significant reduction in mass compared to the initial design
Gradient-based structural optimization of a wind turbine blade root section including high-cycle fatigue constraints
Full text linkUnder the modern design paradigm of wind turbines, the continuous drive towards lower costs through longer blades is raising serious challenges in design, and structural optimization is key to solving the problems effectively. This article focuses on the challenging structural optimization of wind turbine blade root sections, which is scarcely treated in the literature owing to the complex and computationally expensive critical criteria, i.e. buckling, static failure and fatigue damage. The root is parametrized with 1894 thickness design variables and, to solve such an optimization problem efficiently, an adjoint gradient-based framework is proposed, which includes all the criteria mentioned for twelve load cases. Fatigue is notoriously difficult owing to its highly nonlinear behaviour, and its inclusion in the adjoint optimization framework for wind turbine blade optimization is a novelty. The resulting optimization behaviour, laminate layup and structural response are all illustrated, showing many active constraints at convergence, and a significant reduction in mass
Multi-material and thickness optimization of sandwich structures subject to failure criteria
No full textSandwich structures are essential for lightweight design, but their multi-material composition introduces complexities, particularly additional failure modes that must be addressed during design. Structural optimization provides an efficient means to manage these complexities and accelerate development of high-performance designs. Discrete Material and Thickness Optimization (DMTO) enables such optimization of general multi-material and multi-layered structures with varying thickness. The objective of this work is to extend the DMTO framework for sandwich structure design by incorporating sandwich failure criteria. The problems are parametrized using the Discrete Material and Direct Thickness Optimization (DMDTO), a variant of DMTO, allowing the layer thickness to vary independently in each sandwich face sheet and core. A sandwich failure analysis approach that includes key sandwich failure criteria is presented in this context, particularly shear crimping and face wrinkling criteria — novel additions within multi-material and thickness optimization. These criteria are formulated to allow utilizing efficient gradient-based solvers with adjoint design sensitivity analysis to compute problem gradients. Several numerical examples are solved to demonstrate the approach, including a simplified wind turbine blade main spar that highlights the potential for industrial application of the approach
Research in medical education - chances and challenges : international conference, 20th - 22nd May 2009, Heidelberg ; congress abstracts
No full textOn the use of structural optimization to drive the transition to sustainable core materials in wind turbine blades
Full text linkStructural design of modern wind turbine blades poses a serious engineering challenge. Key contributing factors include the use of complex laminated composite materials, the double-curved geometry of modern aerodynamically efficient designs, and the length scale of current commercial offshore blades exceeding 100 m. Yet, developing even larger wind turbines is key to increase the energy output at lower cost. Moreover, it is important that blades are designed as sustainable, which implies transitioning away from many of the materials currently used in designs. To encourage collaboration and innovation for reaching these goals, Gurit Wind Systems has published an in-house developed 98-meter blade model: the Gurit98m. The objective of this work is to introduce the Gurit98m model and demonstrate a use case concerning transitioning to recycled PET foam as the core material as well as discover the optimal distribution of PET core in the model. For this purpose, a gradient-based thickness optimization approach is applied, aiming to minimize the mass of the core materials under buckling, tip displacement, and static failure constraints for twelve different load cases. Moreover, shear crimping and face wrinkling sandwich failure criteria are included as failure criteria, which is a novelty in thickness optimization of wind turbine blades. Structural optimization is performed on different versions of the Gurit98m model, containing one, two, and three shear webs respectively. The optimizations results reveal possible mass reductions, identify critical criteria, and show ideal PET distribution tendencies for the three designs, which can be used as a starting point for more detailed designStructural design of modern wind turbine blades poses a serious engineering challenge. Key contributing factors include the use of complex laminated composite materials, the double-curved geometry of modern aerodynamically efficient designs, and the length scale of current commercial offshore blades exceeding 100 m. Yet, developing even larger wind turbines is key to increase the energy output at lower cost. Moreover, it is important that blades are designed as sustainable, which implies transitioning away from many of the materials currently used in designs. To encourage collaboration and innovation for reaching these goals, Gurit Wind Systems has published an in-house developed 98-meter blade model: the Gurit98m. The objective of this work is to introduce the Gurit98m model and demonstrate a use case concerning transitioning to recycled PET foam as the core material as well as discover the optimal distribution of PET core in the model. For this purpose, a gradient-based thickness optimization approach is applied, aiming to minimize the mass of the core materials under buckling, tip displacement, and static failure constraints for twelve different load cases. Moreover, shear crimping and face wrinkling sandwich failure criteria are included as failure criteria, which is a novelty in thickness optimization of wind turbine blades. Structural optimization is performed on different versions of the Gurit98m model, containing one, two, and three shear webs respectively. The optimizations results reveal possible mass reductions, identify critical criteria, and show ideal PET distribution tendencies for the three designs, which can be used as a starting point for more detailed design
The Gurit98m:a detailed open-source modern offshore wind turbine blade structural model with optimization applications
No full textOne of the primary challenges in wind turbine blade optimization research is creating a model that is representative of current state-of-the-art blade structures. This task is complex and time-consuming, given the multiple disciplines involved in blade design and the large-scale of such blades, which now exceed 100 milliseconds in length. Moreover, the procedures used to establish the models are typically not scientific, implying a significant risk associated with blade research, as substantial resources spent on developing models are wasted if the actual research ideas are ineffective in practice. To reduce the risk and accelerate research efforts in the scientific community, this work introduces an open-source large offshore wind turbine blade model and demonstrates application in structural optimization research. A detailed thickness optimization of the blade’s constituent material layers is performed, with the objective of minimizing cost while accounting for buckling, tip displacement, and static failure constraints, which are many of the key design criteria according to design certification guidelines. A semi-analytical adjoint design sensitivity analysis approach is used to efficiently compute problem sensitivities, allowing inclusion of the constraints for up to twelve extreme load cases each. Application of the presented optimization strategy reduces cost by 17% and mass by 25%, while maintaining all constraints within allowable limits. The change from initial to optimized laminate thickness distribution is shown, and the optimized function response is demonstrated on the blade, showing the material is at its load-carrying limit throughout the entire blade, highlighting the efficiency of the achieved design.</p
