Engineering design frequently involves optimisation problems incorporating computationally expensive analysis tools. Surrogate-based optimisation has been shown to reduce the runtime of these optimisations. Multi-point (MP) and multi-fidelity (MF) infill strategies can further accelerate convergence, yet their combination has not been studied extensively.
This thesis introduces and evaluates an asynchronous MP MF infill strategy, benchmarked against eleven unconstrained MF numerical problems, using expected runtime (ERT).
The asynchronous MP single-fidelity strategy (16 ranks) reduced the geometric mean ERT by 72.7% compared with the baseline Efficient Global Optimisation with Expected Improvement. The single-point MF strategy, on the other hand, increased the ERT by 21.2%, degrading performance. The combined asynchronous MP MF strategy achieved a 68.2% reduction relative to the baseline.
These results show that the asynchronous MP strategy substantially improves performance. In contrast, the selected MF strategy proves detrimental, indicating that a revised MF strategy is required to yield further gains. ... Read more

Heart failure affects millions of people worldwide, creating a critical need for effective Total Artificial Hearts (TAHs) as a bridge to heart transplantation. Soft robotics offer a promising approach for creating TAH's with a more natural, physiological pumping motion. However, current soft TAHs (sTAHs) rely on pneumatic actuation, requiring bulky external compressors and skin-penetrating tubes that pose severe infection risks and limit patient mobility. This thesis explores the transition toward a fully implantable, hydraulically actuated sTAH. Because hydraulic fluid is significantly denser and more viscous than air, this shift introduces substantial energy efficiency challenges. To address these challenges, this research utilizes lumped-parameter models and physical testing within a mock circulatory loop, actuating the sTAH with a custom-designed hydraulic pump. The primary focus of this thesis is the geometrical redesign of the existing pneumatic LIMO (Less In More Out) sTAH prototype. The LIMO prototype utilizes a circular array of pouch motors which contract a central ventricle upon inflation. To minimize hydraulic resistance, the redesigned 'HYDRO LIMO' prototype maximizes cross-sectional flow area and integrates fluid flow paths directly into these pouches, significantly reducing viscous losses. Operating under pulmonary conditions, the HYDRO LIMO achieved an average cardiac output of 6.7 L/min at the 25 W continuous power limit of the proposed Transcutaneous Energy Transfer (TET) system, surpassing the average resting cardiac output of 5-6 L/min. Furthermore, the prototype demonstrated a competitive peak capacity of 8 L/min average at 35 W. Alongside geometric optimization, two theoretical energy-saving strategies were evaluated: resonant actuation and actuation waveform optimization. Simulation results indicate that resonant actuation is not a viable energy-saving strategy for sTAHs. The heavily overdamped nature of the cardiovascular system causes viscous forces to completely dominate the system dynamics and the introduction of an elastic element yields a net electrical energy penalty. Furthermore, while waveform optimization (sine, triangular, square) yielded negligible efficiency differences for the current low-resistance HYDRO LIMO prototype, simulations reveal that rapid diastolic unloading (e.g., a square wave) is beneficial to maximize stroke volume under the restrictive filling conditions as a result of future system miniaturization. Ultimately, this thesis demonstrates that the transition to a hydraulically actuated sTAH is highly viable when prioritizing the minimization of internal flow resistance and optimizing diastolic filling conditions. The HYDRO LIMO establishes a strong, energy-efficient foundation for the future development of fully implantable, TET-powered soft artificial hearts. ... Read more

Formula 1 suspension design is a fundamentally multidisciplinary challenge, requiring simultaneous consideration of vehicle dynamics, aerodynamics, structural integrity, and packaging constraints under extreme time pressure. Despite the growing maturity of Multidisciplinary Design Optimisation (MDO) methodologies, their application to early-phase suspension concept development in motorsport remains limited. This thesis develops an integrated MDO framework coupling kinematic analysis, ground-structure topology optimisation, aerodynamic modelling, half-car finite element compliance analysis, and vehicle dynamics simulation within a single NSGA-II-driven optimisation loop.

The framework operates over a 49-dimensional design space of suspension pickup point coordinates, arm stiffness parameters, and a discrete architecture selector. A production run of 482 evaluations was completed in approximately 50 hours of simulation time, with 89.4% satisfying all 52 constraints. The resulting 10-solution, three-objective Pareto front reveals the trade-off structure between three performance objectives: tyre grip utilisation (exploitation of tyre load potential through camber and toe control), transient vehicle stability, and aerodynamic downforce. Two distinct solution families emerge: a kinematic-priority cluster that simultaneously optimises grip utilisation and vehicle stability, and an aerodynamic-priority cluster that prioritises downforce at the cost of kinematic precision. The dominant conflict is between kinematic performance and aerodynamic compliance; grip and stability are broadly complementary rather than conflicting. This is consistent with established suspension design theory and constitutes the primary design insight of the framework.

Structural optimisation is integrated via a Ground Structure Method (GSM) for upright topology optimisation, maintaining computational tractability by avoiding full finite element mesh regeneration at each iteration. The resulting structural superelements are directly coupled to the half-car compliance model, propagating stiffness information into the vehicle dynamics simulation. Domain expert knowledge is embedded through heuristics-based design partitioning and experience-based aerodynamic assessment, ensuring the optimiser explores only viable architectural configurations.

A Model-Based Systems Engineering (MBSE) development process is proposed in which the MDO execution can be structured and implemented in future work, providing a concrete foundation for transitioning the framework into a fully model-driven engineering environment.

The framework demonstrates that a 49-dimensional multidisciplinary suspension design problem is tractable as a single automated optimisation loop, suggesting that the conventional sequential, discipline-by-discipline approach at the conceptual phase is not the only viable option for problems of this complexity. The 50-hour unattended run completes a multidisciplinary concept exploration that would require multiple coordinated simulation campaigns under conventional manual workflows. ... Read more

To create an X-ray Interferometry test bed a high precision adjustable slit mechanism is needed. Com pliant mechanisms are ideal solutions for such high precision mechanisms. This research presents the design, manufacturing, and testing of such a compliant mechanism. Furthermore, topology optimization is explored and evaluated as an alternative design method to find a novel mechanism that performs better than a traditionally synthesized counterpart. A traditionally designed mechanism was first designed and characterized using a 405 nm laser source and Fraunhofer diffraction analysis. Although optical verification was limited to a minimum slit width of 3 μm, experimental results demonstrate that the traditionally developed design has the potential to achieve dimensional requirements, with demonstrated step sizes of 0.2 μm. Simultaneously, a topology optimization model was developed, implementing penalized strain energy, parasitic displacement, and decoupling constraints, along with a robust formulation, to generate an alternative multi-degree-of-freedom mechanism. Although topology optimization proved a tool capable of producing an alternative compliant mechanism, there is still work to be done to fully mature this synthesis method. The research concludes that the developed mechanism meets the requirements set for the X-ray Interferometry test bed, whilst the topology optimization proves a viable alternative, albeit complex, method for future high-performance iterations. ... Read more

Loudspeaker cabinet design has historically been constrained by conventional manufacturing methods, which favour rectangular panel construction due to its simplicity and repeatability. Large Format Additive Manufacturing (LFAM) removes this constraint by enabling complex curvatures and geometries at manageable production costs. This introduces new possibilities for geometry-driven acoustic performance improvement, but also new challenges. In particular, the anisotropic material properties of 3D-printed polymers and a general lack of research on vibroacoustic behaviour in this context. This thesis develops a computational framework for simulating and optimising the vibroacoustic performance of sealed, low-frequency loudspeaker cabinets. The core problem is the coupled interaction between structural vibrations of the cabinet panels and the acoustic field they radiate, which is a multiphysics problem that requires numerical methods to solve. A hybrid FEM/BEM simulation model is implemented in COMSOL Multiphysics, combining finite element structural analysis with boundary element acoustic radiation modelling. The framework is validated against anechoic measurements of a physical prototype provided by partner Addit Audio. The validated simulation model is integrated into a gradient-based shape optimisation framework. Cabinet panel geometries are parameterised and iteratively deformed to suppress panel resonances and improve sound dispersion, using adjoint sensitivity analysis to efficiently compute gradients. Manufacturability constraints imposed by the LFAM process are incorporated throughout. The optimisation is applied to a rectangular reference cabinet, and the results are analysed in terms of physical mechanism, robustness, and transferability. The findings are broadly applicable to the vibroacoustic optimisation of thin-walled structures beyond the loudspeaker domain, wherever panel resonances and radiated sound are of concern.
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High-tech machinery increasing demands results in more and more heat output by it’s components. To lower the temperature of these components cooling channels are used. The performance of these cooling channels can be increased by adding flow disrupting structures inside the channel. This study explores the use of density-based topology optimization to optimize the geometry of these structures. A Darcy-Forchheimer penalization method is used combined with a vorticity-based objective to avoid the use of the heat transfer model during optimization. The resulting designs show increased heat transfer as the amount of vorticity increases. However, post-processing results show that overall thermal performance largely related to the pressure drop in the channel rather than detailed geometry. Under these very specific conditions increased flow velocity by narrowing the channel has more effect on thermal performance than disrupting the flow. However, more research is needed making use of a turbulence flow model or different restrictions to the design. ... Read more

Achieving consistent liquid thickness in Liquid Phase Transmission Electron Microscopy (LPTEM) is essential for repeatable, high-resolution imaging. Inconsistencies in chip deformation during clamping can lead to variation in liquid layer thickness and compromise imaging quality. This research develops a simulation–experiment framework to evaluate and minimize deformation in MEMS-based liquid cells, with the goal of improving mechanical repeatability during assembly. The modeling approach begins with 2D finite element simulations to identify critical deformation trends, followed by uncertainty quantification (UQ) and geometry optimization to improve chip flatness. These insights guide full 3D simulations, where the lid geometry is refined to reduce chip deformation and maintain a uniform inter-chip gap near the membrane region. The 50 nm SiNx membrane is decoupled from the main model and studied separately using extracted boundary conditions to reduce computational cost. In parallel, white-light interferometry is used to characterize chip curvature at multiple torque levels using a previous-generation holder. A Gauge Repeatability and Reproducibility (R&R) analysis shows that the experimental method reliably distinguishes deformation trends due to torque variation. Simulation and experiment show qualitative agreement in chip bowing behavior supporting optimization strategy. This work delivers a simulation–experiment workflow for improving mechanical repeatability in MEMS-based LPTEM holders, providing a foundation for future design enhancements and fabrication. ... Read more

In the high-tech engineering sector, industry is always looking for the competitive, technological edge. Through optimisation, in particular the optimisation of component designs, performance gains can often be realised compared to conventional design geometries. Even within existing implementations, this so-called topology optimisation allows for improvements in component performance, simply by exchanging its existing conventional design, and ultimately to higher-level machine assemblies and modules. This low barrier to entry makes topology optimisation a field of engineering that has been gaining traction over the past decades within various fields of high-tech engineering and, of course, research. While much research has been done into the field of topology optimisation, including research into multi-physics optimisation problems, such as conjugate heat transfer problems, more work is still to be done to improve models, improve optimisation schemes and approaches, reduce computational time, increasing results accuracy and much more. This thesis, in particular, is focussed on devising a strategy to derive and implement a thermofluidic model specifically for density-based topology optimisation applications. In doing so, emphasis is placed on the accuracy of the optimisation model when compared to numerical results found in regular thermofluidic analyses of systems. In this thesis, a new technique is introduced to refine existing fluidic topology optimisation models for density-based methods: dubbed IGPP, Implicit Gradient-Parallel Penalisation for fluid velocity fields is devised, implemented and evaluated numerically. Furthermore, a parameterisation is created for the material properties relevant to conjugate heat transfer problems. Finally, the model’s performance is evaluated. ... Read more

This thesis presents several novel methods developed for imposing geometric constraints for cleanability in density based topology optimization. Design for cleanability is a field of growing relevance, and requirements for cleanibility should be taken into account during the design optimization instead of using post-optimization design modifications. The first method presented ensures that a cleaning fluid can passively run off the surfaces of a part under the effect of gravity alone, which assures drainability. Secondly, a method is introduced to ensure designs where the entire surface can be cleaned by jetting a cleaning fluid. Next, building on the previous method, simultaneous optimization of component design and the jet positions is established. This method is presented as a general framework suitable for any geometric requirement. Finally, building on the concepts developed in the aforementioned method, a new feature mapping TO approach is presented with highly flexible feature shapes, parametrized by NURBS. Every proposed method is demonstrated and investigated through various numerical examples, and all methods succeed in ensuring the targeted geometric requirements. ... Read more

The design of high-performing fluid and thermal devices is crucial for many aerospace applications such as heat exchangers and flow manifolds. These systems often operate under transient conditions, adding another layer of complexity to their design. Conventional design principles have limitations as they depend on engineers to propose the principal structure. In this dissertation, topology optimization (TO) is investigated as a method to design transient flow and thermal devices. To date, the use of TO for transient flow or thermal problems remains limited to experts in the field. Performing successful optimization heavily relies on the tuning of model and optimization parameters. By systematically investigating and improving the algorithms, their parameters and their characteristics, this thesis provides engineers with guidelines for their use.
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This paper presents the design of a lab-scale silicon nitride photonic crystal lightsail, demonstrating the LightSailSim software package. LightSailSim, an open-source analysis pipeline, integrates a custom mechanical solver based on a particle system model with optical simulation results. The resulting design balances dynamic and structural stability with propulsive performance. It consists of an optimised photonic crystal that provides a suitable trade-off between stability and propulsive force. The sail is suspended at its edges by a circular ring made of silicon, providing sufficient boundary tension to prevent sail deformation-induced instability. The design is made such that it can be produced from a single silicon wafer and levitated using a single 400 W laser.
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Soft robots, characterised by compliant mechanisms (CMs) made from low-stiffness materials, offer improved adaptability compared to traditional, rigid robots. These CMs are often actuated by pressure loads. Moreover, soft robots provide new possibilities in the area of robotics. They can be used in search and rescue and interact safely in collaboration with humans.

The current state-of-the-art in Topology Optimisation (TO) for design-dependent pressure-actuated CMs (PACMs) relies heavily on linear models. The determination of design-dependent pressure loads involves employing the Darcy method, which integrates Darcy's law with the drainage term to obtain the pressure field. Subsequently, the finite element method (FEM) is used to transform the pressure field into consistent nodal forces. However, it is crucial to acknowledge that these linear models are only valid for small displacements.

This thesis introduces a novel approach by incorporating nonlinearities into the solid mechanics of the TO process for PACMs in conjunction with the Darcy method. Additionally, this work incorporates nonlinearities into the solid mechanics of the TO process for PA multi-material compliant mechanisms, presenting another novel method.

Four nonlinearities in the solid mechanics of PA soft robots may occur, two of which are addressed in this thesis: geometric nonlinearities and a hyperelastic material model. Geometric nonlinearities arise from large deformations caused by high applied pressures. The Neo-Hookean material model is implemented to describe the low-stiffness material accurately.

The TO of pressure-actuated (PA) soft robots is simulated using COMSOL, a commercial software program for multi-physics simulation. This research presents a detailed comparison between theoretical predictions and practical outcomes as realised in COMSOL. Furthermore, this thesis includes a case study validating the successful implementation of the new method, covering a PA inverter, a PA compliant gripper, a PA member of the Pneumatic Networks, and a PA multi-material compliant gripper. The obtained results indicate limitations on the allowable applied pressure loads for the mechanisms, specifically in the case of the PA member of the Pneumatic Networks and a PA multi-material-compliant gripper. However, the PA inverter and PA compliant gripper validate the expectation that incorporating a hyperelastic material model yields significantly different results than the linear elastic material model. Moreover, the TO with the hyperelastic material model can predict displacements more accurately than the linear TO, as the differences between the displacements obtained from the TO and the analysis align more closely.

The Wang method is investigated to observe its influence on the range of the applied pressure loads during the TO of PA soft robots. The Wang method employs an interpolation technique that interpolates between linear and nonlinear theories. In this approach, void elements are described using linear theory, while solid elements are characterised by nonlinear theory. This interpolation method is developed to address distorted elements during large displacements. It effectively extended the range of applied loads during the TO of structures. However, it is found that this method does not influence the range of the applied load during the TO of CMs. ... Read more

Granular materials are all around and have many secrets that still need to be unravelled. This thesis shows how the stochastic behaviour of granular materials can be identified and efficiently included in design of bulk handling equipment. To achieve this, metamodels play a key role as they are able to capture trends of physical models and give fast predictions. In this research it is shown what the opportunities and limitations of metamodels are in a hopper case study based on simulation data from a discrete element model (DEM). Next a procedure is presented in which the stochastic behaviour and metamodels are combined to calibrate a DEM model including the stochastic behaviour of the granular material. The stochastically calibrated DEM model is accurate and used as the basis for a design optimization case study in which the effect of robust optimization was evaluated and validated. These studies combined show that stochastic behaviour of granular material can be included in design of bulk handling equipment and lead to improved and robust designs. ... Read more

Given the growing number of environmental and societal concerns we confront today, the idea of sustainability has gained importance. At the same time, new strategies for improving the performance of structures and systems have been developed due to developments in engineering and computational design. This research aims to generate a sustainable design using topology optimization by focusing on design for disassembly. One advantage of design for disassembly is that when a product can be disassembled, the parts can be reused, repaired, recycled, and remanufacture. This facilitates other aspects of product sustainability, such as the product's life cycle and end-of-life. A structure is divided into two parts and attached by a connection point, this connection point is called the connector. Due to sustainability, the connection method needs to be a non-destructive method, which in this case is the bolts. Next to the connector, two voids are required to insert, tighten and remove the bolts. Therefore, in this research, a structure is optimized using topology optimization and simultaneously optimizing the position of cut lines and connectors. The approach taken uses level set functions to model the cut of the structure, as well as the connectors and the voids. Then, they are converted into a density field using a smoothed Heaviside function. A Solid Isotropic Material with Penalization (SIMP) motivated method is used to join all the different density fields into an equation for the interpolated elasticity modulus. The optimization aims to minimize compliance with volume and no-overlap constraints. The non-overlap constraint is applied to the connectors.
The structure and the position of the cut line and the connectors are optimized using the Method of Moving Asymptotes (MMA) method. A gradient based sensitivity analysis is used in the MMA. Afterwards, the influence of the cut line, the connector and the voids are observed individually. After optimizing the parts individually, the full optimization was performed, where the structure, the cut lines and the connectors with the voids were optimized. Furthermore, a parameter study was done to observe their influence on the final layout. The optimizer's behaviour was observed by looking at the optimization results and the parameter study. For example, how the optimizer tends to stack some connectors together to create a member of the structure or the influence of the voids.

With the approach presented, the main idea of optimizing a structure using topology optimization and simultaneously dividing it and optimizing the connector's position is obtained. However, the optimization has some limitations, as some assumptions and design considerations are not accurate, further research is needed to get accurate results.
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In the engineering industry, all structural parts have to be designed as efficient and lightweight as possible. Traditionally, the design process has been carried out through manual design iterations, which can be time-consuming and require significant engineering expertise. Over the last decades however, several computational design techniques like Topology Optimization and Generative Design have been developed to support engineers in the structural part design process. Even though these techniques can have a positive influence on the design process, they both also have their downsides. Topology Optimization only gives a single result that is often a local optimum, influenced by boundary conditions and numerical settings. Commercial Generative Design tools explore multiple design options in a single run using AI algorithms, but need cloud-based systems to carry out their demanding simulations which still take several hours per run. It is however expected that a combination of the two, a Topology Optimization based Generative Design approach in the form of an auxiliary tool, has potential to improve the early stages of the design process even more. With such a design approach, multiple design solutions are explored quickly to study the effect of boundary conditions or numerical settings. This can help designers by giving direction and insight in trade-offs between multiple objectives, early on in the design process when design decisions still have the highest impact.

The goal for this research was therefore to research the effect of such a Topology Optimization based Generative Design approach on the design performance and experience. In order to do so, a robust and user-friendly TOP-GD tool was created. In this tool, multiple design solutions are explored quickly by implementing a batch-run setup that varies several chosen parameters, without needing to manually run several optimizations consecutively. Calculations are done with a simple TO script using coarse geometries, and without taking into account manufacturing methods yet. This asks for less demanding, detailed and complicated calculations than AI-based Generative Design tools currently offer, while at the same time moving from a single TO result to generating a range of candidate solutions. A lot of effort was put in the user-friendliness of the TOP-GD tool, enabling an easy workflow for the setup of design problems and a clear presentation of the results by means of a simple GUI.

The use of the TOP-GD tool in the design process was evaluated in an experiment, where it was compared with a more simple TO tool and a basic manual design approach using just pen and paper. This was done by giving the participants of the experiments three simple design assignments, that they had to carry out using each of the design approaches one by one. Evaluation of the approaches was done by comparing the design performance, and assessing the design experience with a survey and using Eye-tracking techniques.

The results of this experiment did not show enough evidence to conclude that the different design approaches had an effect on the design performance for the simple assignments executed during the experiment. However, the results of the survey show a clear positive impact of both the TO tools on the design experience, compared to manually designing. Furthermore, the TOP-GD tool has the largest positive impact on the design experience and its use in the design process is considered a big improvement, especially in quickly exploring new design directions and creating overview. This confirms the expectation that a Topology Optimization based Generative Design approach has a positive effect on the early stages of the design process. The differences found with Eye-tracking between the TO tools support this, although a more extensive experiment should be done to convincingly confirm this conclusion. ... Read more

Offshore wind turbines have seen a significant increase in size over the past decades. A critical consequence of this increase in size is a substantial increase in the torque transferred from the wind turbine rotor. This leads to the necessity of larger and heavier drivetrains to adhere to structural failure requirements and subsequently to larger and heavier tower and support structures increasing the total mass and cost of the turbine. Hence, reducing the mass-to-torque ratio of the drivetrain has become a key design challenge.

The company Delft Offshore Turbines (DOT) proposes to replace the conventional drivetrain in the top of the turbine with a hydraulic drivetrain, which has a lower mass-to-torque ratio. Although this concept shows promise, finding a low mass design that fulfils the infinite fatigue life requirement can be challenging. Using topology optimization to minimize mass while constraining the structural requirements could, therefore, be instrumental in the realization of this concept.

The design case by DOT can be classified as rotating machinery. In general rotating machinery is
commonly subjected to periodic loading that varies non-proportionally in time. This results in fluctuating stresses causing material fatigue. A consequence of the non-proportionality of loading is that the time response needs to be computed to evaluate for fatigue, which adds additional computation cost. However, another common aspect found in rotating machinery is that parts are cyclic symmetric, which allows for a potential reduction in computation cost.

In this thesis a method is presented to implement infinite fatigue life constraints into density based topology optimization for structures subjected to non-proportional loading, while cyclic symmetric properties are exploited to reduce computation cost. It was found that when the load case on a cyclic symmetric part adheres to certain conditions, a single static FE-analysis can provide multiple time steps for a quasi-static analysis. Decreasing the computational burden roughly proportional to the unique number of time steps obtained. The largest local variations in stress are estimated using a smooth min/max function and aggregated into a global constraint.

The method was tested on several numerical problems as well as applied to the DOT design case. The results showed that the method was able to properly constrain a global fatigue constraint while minimizing mass, achieving final designs that might not be trivial to find by hand.
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Silicon based power semiconductors have long been used as the standard in ‘semiconductor technology in power conversion applications’. Recent developments replaces the Silicon with Silicon Carbide as it results in superior performance of the power conversion applications. However, due to the increased performance, challenges regarding heat dissipation emerge and the lifetime of the power semiconductor packaging or power module is compromised. Since this leads to an increase power density, the cooling of the power module is becoming of more importance and the heat sink becomes an interesting component to optimize. The best performance of a heat sink can be obtained when the flow through the device is turbulent. Developing turbulent flow heat sinks by using topology optimization methods can significantly improve the cooling performance compared to the current designs. This work is thus aimed towards improving methods for topology optimization of turbulent flow cooling devices. However, this work focuses on turbulent flow topology optimization only and aims to improve the accuracy of current methods. It is important that the flow physics are accurate since the thermal energy transfer is dependent on the flow field. The current state-of-the-art method based on the 𝑘−𝜔 turbulence model developed by Dilgen et al. is investigated. A design domain is subdivided into elements since the finite element method (FEM) is used, such that an optimization algorithm is able to turn every element into either fluid or solid with the goal of finding the best performing structure. This density based approach, models the solid domain as a highly impermeably porous material. To inhibit flow in the solid domain a Darcy penalization is added to the momentum equation. Moreover, in the method by Dilgen et al. boundary conditions in the other turbulent fields are also enforced using a similar penalization approach. Weaknesses and errors in the density based method are investigated by comparing solutions to ones computed on a body fitted mesh. It has been found that the largest errors in the solution, by using the state-of-the-art method, appear at the solid/fluid interface in the design. In these regions the penalizations are not applied correctly for the desired boundary conditions. Therefore, in this work it is improved on by the enforcement of the boundary condition by using the Dilation method. The Dilation method focuses on the solid/fluid region where it shifts the boundary conditions for the specific dissipation rate (𝜔) and ensures it reaches the desired value at the solid/fluid interface. Secondly, severe flow leakage is found in the “porous” solid domains using the state-of-the-art method. Flow leakage is reduced by using an improved formulation of the maximum Darcy penalization in the solid domain. Finally, the improved approach is investigated in several topology optimization cases and compared to the state-of-the-art Dilgen method. It is shown that by using the new approach, different designs with a better accuracy can be obtained. In an extreme test case, the Dilgen method resulted in an infeasible design which disconnects the flow inlets from the outlets while the new and improved method resulted in a feasible design. ... Read more

The recent success of - and demand for - compliant mechanisms has increased rapidly within the micro-electromechanical systems-, aircraft-, spacecraft-, surgical-, and precision-instrument industries. Yet, even greater success may be achieved by overcoming the computational cost and instability of the mechanisms' design methodology. This involves large-scale topology optimization, geometrically non-linear structural analysis, and particularly integrating the latter into the former. Therefore, a novel framework is proposed that extends the powerful design freedom of topology optimization with most of the geometrically non-linear qualities, without as much of the computational ramifications. Utilizing a Bayesian-enhanced perturbed analysis, the equilibrium curve is locally approximated by an asymptotic expansion, satisfying the curve's higher-order geometric derivatives at the undeformed state. Each of the latter is recursively and efficiently obtained through a linear solve with the same, Cholesky-factorized stiffness matrix. Furthermore, a tensor reformulation and -decomposition of the four-noded bilinear element's Green-Lagrange strain energy model are successfully exploited. A tight error estimator is derived to govern the Bayesian analysis and balance approximation efficiency and accuracy during optimization. Design-sensitivities of this error-estimator and other design-dependent responses are analytically obtained through the adjoint method, and applied in a few classical density-based topology optimizations; While Bayesian-enhanced perturbed analysis required noticeably less computational effort compared to Newton-Raphson analysis under mildly non-linear conditions, it often resulted in practically identical performance improvements compared to linear analysis. ... Read more

By 2030, the global semiconductor industry is projected to hit the valuation of becoming a trillion dollar industry. Advancements in electronic devices have gave rise to tougher requirements thereby requiring the manufacturers to push the limits of consistency. This has lead to a need to enhance the accuracy of the chip manufacturing process. Wafer flatness is one of the primary prerequisites for attaining high accuracy in integrated circuit manufacturing. The high accuracy is achieved by incorporating optical lithography in the development of circuits with small feature sizes. The current lithography machine requires precise estimation of wafer flatness on a sub-nanometer scale for the elimination of deviations between the exposed region and the plane of focus. In this thesis, the point of focus is on the short stroke positioning system of a lithography machine. The critical aspect of flatness is interpreted by performing scanning operations on a wafer table surface. These operations provide an estimation of the types of deformations the wafer is subjected to. The wafer table acts as a wafer carrier, which undergoes lithography operations. Therefore, it becomes very critical to examine the nature of the wafer table. After performing scans for surface deformations, an optimization problem is formulated which involves placing piezoelectric actuators under the wafer table. The role of the piezoelectric actuators is to correct the wafer table thereby enhancing its flatness property. Through this research, the optimization yields to give a better estimation of flatness by placement of actuators. The problem formulation and the solution proposed are able to correct the flatness by approximately 95% of the initial deformation value. The work done in this research can be extended from an application point of view and can be utilized in estimating and correcting the deformations of any given structure. Since this research involved working in a 2-dimensional domain, the further implications of this research involves extending the proposed flatness correction technique to a 3-dimensional domain. ... Read more

In a high-precision system that performs measurements or tooling on a workpiece, alignment of the tool and workpiece is of prime importance. To prevent misalignment, which leads to a loss in accuracy and precision, unwanted vibrations in structures must be attenuated. Topology Optimization (TO) is evolving as a mature design tool that provides innovative designs beyond human creativity. This thesis focuses on developing and investigating TO methods for the limitation of response peaks on a flat surface for suspended structures. When optimizing for multiple excitation frequencies at multiple output points, the complexity of the problem increases, and the number of required constraints grows manifold. Thus, for a compact formulation, there is a need for aggregation of peaks in both dimensions, space, and frequency. Furthermore, the application requires the top surface of the suspended structure to remain flat during operation. In such a scenario, where a structure is excited harmonically, the dynamic deformations on the surface become key to quantifying surface flatness. The incorporation of dynamic flatness measures in TO framework is studied and implemented, and the results show that the proposed methods look promising. ... Read more