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In the process of metal cutting, realizing effective monitoring of tool wear is of great significance to ensure the quality of parts machining. To address the tool wear monitoring (TWM) problem, a tool wear monitoring method based on data-driven and physical output is proposed. The method divides two Physical models (PM) into multiple stages according to the tool wear in real machining scenarios, making the coefficients of PM variable. Meanwhile, by analyzing the monitoring capabilities of different PMs at each stage and fusing them, the PM's ability to deal with complex nonlinear relationships, which is difficult to handle, is improved, and the flexibility of the model is improved; The pre-processed signal data features were extracted, and the original features were fused and downscaled using Stacked Sparse Auto-Encoder (SSAE) networker to build a data-driven model (DDM). At the same time, the DDM is used as a guidance layer to guide the fused PM for the prediction of wear amount at each stage of the tool, which enhances the interpretability of the monitoring model. The experimental results show that the proposed method can realize the accurate monitoring of tool wear, which has a certain reference value for the flexible tool change in the actual metal-cutting process., QC 20240829

Modern railway infrastructures, especially bridges, are exposed to significant vibrations with potential safety implications. In this context, previous studies have shown the inconsistency and inadequacy of some conventional design methods necessitaing them to be improved. The assessment of safety inherently deals with uncertainties. Therefore, the current study is dedicated to this objective using reliability-based methods. Of the various possible failure modes, the investigations presented here are limited to running safety and passenger comfort. The investigation of these limit-states requires constructing complex computational models with train-track-bridge interaction capabilities. However, the application of these computationally intensive models in the context of structural reliability does not appear to be feasible. Simplifying the system, the vertical acceleration and the deflection of the bridge serve as implicit limit-state measures. Initially, using First Order Reliability Method (FORM) revealed limitations in the application of the current safety factor, resulting in inconsistent reliability indices. Therefore, probabilistic design curves are proposed, defining minimum required bridge mass and stiffness based on cross-section types, span configurations and train speeds. These results are obtained by formulating a FORM-based optimization. Subsequently, the results are used to investigate the sensitivity of the estimated failure probabilities with respect to the contributing basic random variables. Acknowledging the limitations of FORM, surrogate-assisted simulation-based reliability assessments were used for further investigations. A comparison of the performance of widely used regression-based surrogate models under an identical active learning scheme showed the superior performance of the Kriging method over the others. Within areliability-based design optimization framework, this Kriging model facilitates the generation of new probabilistic design cur, Moderna järnvägsbroar utsätts för betydande säkerhetsrelaterade vibrationer. Tidigare studier har visat att vissa konventionella dimensioneringsmetoder är inkonsekventa och otillräckliga, vilket kräver förbättringar. Säkerhetsbedömning handlar i grunden om osäkerheter. Därför ägnas den föreliggande studien åt detta mål med hjälp av tillförlitlighetsbaserade metoder. Undersökningarna här begränsas till trafiksäkerhet och passagerarkomfort som möjliga dimensioneringsvillkor. Undersökningen av dessa gränstillstånd kräver komplexa beräkningsmodeller som beaktar tåg-spår-bro-interaktion. Att använda beräkningsintensiva modeller för strukturell tillförlitlighet verkar inte genomförbart. Genom förenklingar av systemet kan vertikal acceleration och nedböjning ansättas som mått för implicita gränsvillkor. Inledningsvis visade användningen av första ordningens tillförlitlighetsmetod (FORM) begränsningar i tillämpningen av nuvarande säkerhetsfaktor, vilken resulterade i inkonsekventa säkerheter. För att adressera detta föreslås probabilistiska dimensioneringskurvor, som definierar minsta erforderliga bromassa och styvhet baserat på tvärsnittstyper, spannkonfigurationer och tåghastigheter. Dessa resultat erhålls genom att formulera en FORM-baserad optimering. Därefter används resultaten för att undersöka känsligheten hos de uppskattade brottsannolikheterna med avseende på de ingående grundläggande stokastiska variablerna. Med tanke på begränsningarna med FORM användes simulering-baserade tillförlitlighetsbedömningar med hjälp av surrogatmodeller för fortsatta undersökningar. I en jämförelse av kända regressionsbaserade surrogatmodeller, under identiska inlärningsförutsättningar, visade Kriging-metoden överlägsen effektivitet. Inom ramen för en tillförlitlighetsbaserad optimering underlättar denna Kriging-modell framtagningen av nya probabilistiska designkurvor. Detta uppnås genom en ny formulering av metoden där korrelationen mellan de stokastiska variablerna beaktas med hjälp, QC 240325, IN2TRACK2, IN2TRACK3, IAM4RAIL

Semi-crystalline polymers is an important group of materials that is used in a vast array of products. In this study, the rate-dependent properties of high-density polyethylene (HDPE) are investigated, both experimentally and theoretically. Experimental compression testing of a three-dimensional HDPE structure is performed and analysed numerically by use of the finite element method. In addition, an Eulerian constitutive material model for isotropic, semi-crystalline polymers is proposed. The model is able to account for such essential phenomena as strain-rate dependence, work hardening, pressure-dependence of inelastic deformations, and damage. The proposed material model was implemented in Abaqus as a VUMAT, which is an explicit implementation. The material model was calibrated by use of uniaxial tensile tests performed on HDPE dog-bone shaped samples, and the model was further explored by applying the VUMAT implementation to the compression tests of the HDPE structure. The simulation model was able to reproduce the experimental results well, both the uniaxial tests and the compression tests. In particular, the friction present in the compression tests seems to play an important role in determining the buckling mode of the structure.

This paper aims to elucidate the clear visibility of attenuating seismic waves (SWs) with forest trees as natural metamaterials known as forest metamaterials (FMs) arranged in a periodic pattern around the protected area. In analyzing the changeability of the FM models, five distinct cases of “metawall” configurations were considered. Numerical simulations were conducted to study the characteristics of bandgaps (BGs) and vibration modes for each model. The finite element method (FEM) was used to illustrate the generation of BGs in low frequency ranges. The commercial finite element code COMSOL Multiphysics 5.4a was adopted to carry out the numerical analysis, utilizing the sound cone method and the strain energy method. Wide BGs were generated for the Bragg scattering BGs and local resonance BGs owing to the gradual variations in tree height and the addition of a vertical load in the form of mass to simulate the tree foliage. The results were promising and confirmed the applicability of FEM based on the parametric design language ANSYS 17.2 software to apply the boundary conditions of the proposed models at frequencies below 100 Hz. The effects of the mechanical properties of the six layers of soil and the geometric parameters of FMs were studied intensively. Unit cell layouts and an engineered configuration for arranging FMs based on periodic theory to achieve significant results in controlling ground vibrations, which are valuable for protecting a large number of structures or an entire city, are recommended. Prior to construction, protecting a region and exerting control over FM characteristics are advantageous. The results exhibited the effect of the ‘trees’ upper portion (e.g., leaves, crown, and lateral bulky branches) and the gradual change in tree height on the width and position of BGs, which refers to the attenuation mechanism. Low frequency ranges of less than 100 Hz were particularly well suited for attenuating SWs with FMs. However, an engineering metho, Validerad;2024;Nivå 1;2024-03-26 (hanlid);Funder: Prince Sattam bin Abdulaziz University (PSAU/2023/R/1444); Beijing Municipal Education Commission; Islamic University of Madinah, Saudi Arabia;Full text license: CC BY

This study investigated mechanical and tribological properties of polyetheretherketone (PEEK) and PEEK composites, before and after aging in liquid nitrogen for 5 months. Tribological tests conducted at 25 °C and at − 100 °C in air and in high vacuum (10−5 Pa) environment revealed the effect of matrix modification, fillers, environment, temperature, and cryogenic aging on their performances. Cryogenic aging of the polymers resulted in cryogenic embrittlement and decrease of the fracture toughness by around 10% and increase of wear rate by at least 20%. Very low coefficient of friction (0.02) was achieved in cryogenic vacuum environment for carbon fiber, graphite, and PTFE reinforced PEEK. The results indicate the significant impact of aging, temperature and environment on PEEK and its composites., Validerad;2024;Nivå 2;2024-04-05 (marisr);Full text license: CC BY

Purpose: Severe disruptions to maritime supply chains, including port closures, congestion and shortages in shipping capacity, have occurred during the COVID-19 pandemic. This paper’s purpose is to explore flexibility-based countermeasures that enable actors in maritime supply chains to mitigate the effects of disruptions with different characteristics. Design/methodology/approach: Semi-structured interviews were conducted with shipping lines, shippers, forwarders and ports. Data on the COVID-19 pandemic's effects and countermeasures were collected and compared with data regarding the 2016–2017 Gothenburg port conflict. Findings: Spatial, capacity, service and temporal flexibility emerged as the primary countermeasures, whilst important characteristics of disruptions were geographical spread, duration, uncertainty, criticality, the element of surprise and intensity. Spatial flexibility was exercised in both disruptions by switching to alternative ports. During the COVID-19 pandemic, ensuring capacity flexibility included first removing and then adding vessels. Shipping lines exercising service flexibility prioritised certain cargo, which made the spot market uncertain and reduced flexibility for forwarders, importers and exporters that changed carriers or traffic modes. Experience with disruptions meant less surprise and better preparation for spatial flexibility. Practical implications: Understanding how actors in maritime supply chains exercise flexibility-based countermeasures amid disruptions with different characteristics can support preparedness for coming disruptions. Originality/value: Comparing flexibility-based measures in a pandemic versus port conflict provides insights into the important characteristics of disruptions and the relevance of mitigation strategies. The resilience of maritime supply chains, although underexamined compared with manufacturing supply chains, is essential for maintaining global supply chain flows., This research is funded by the Swedish Transport Administration through the project “The role of liner shipping for robust supply chains” and by the maritime collaboration platform Lighthouse through the pre-study projects “Shipping post-covid-19” and “Regionalised supply chains and the effects on shipping”. In addition, the University of Gothenburg and Chalmers University of Technology have funded parts of the work through the joint Strategic Research Area Transport.

The construction sector has been under growing public attention recently as one of the leading causes of climate change and its detrimental effects on local communities. In this regard, geopolymer concrete (GPC) has been proposed as a replacement for conventional concrete. Predicting the concrete’s strength before pouring is, therefore, quite useful. The mechanical strength of slag and corncob ash (SCA–GPC), a GPC made from slag and corncob ash, was predicted utilizing multi-expression programming (MEP). Modeling parameters’ relative importance was determined using sensitivity analysis. When estimating the compressive, flexural, and split tensile strengths of SCA–GPC with MEP, 0.95, 0.93, and 0.92 R2-values were noted between the target and predicted results. The developed models were validated using statistical tests for error and efficiency. The sensitivity analysis revealed that within the mix proportions, the slag quantity (65%), curing age (25%), and fine aggregate (3.30%) quantity significantly influenced the mechanical strength of SCA–GPC. The MEP models result in distinct empirical equations for the strength characteristics of SCA–GPC, unlike Python-based models, which might aid industry and researchers worldwide in determining optimal mix design proportions, thus eliminating unneeded test repetitions in the laboratory., Validerad;2024;Nivå 2;2024-04-09 (joosat);Funder: Microbial Deposited Calcium Carbonate Reinforced Recycled Fine Aggregate (GZY2021-NEW-06); Najran University (NU/RG/SERC/12/1);Full text license: CC BY

Photovoltaic (PV) modules play a pivotal role in renewable energy systems, underscoring the critical need for their fault diagnosis to ensure sustained energy production. This study introduces a novel approach that combines the power of deep neural networks and machine learning for comprehensive PV module fault diagnosis. Specifically, a fusion methodology that incorporates autoencoders (a deep neural network architecture) and support vector machines (SVM) (a machine learning algorithm) is proposed in the present study. To generate high-quality image datasets for training, unmanned aerial vehicles (UAVs) equipped with RGB cameras were employed to capture detailed images of PV modules. Burn marks, snail trails, discoloration, delamination, glass breakage and good panel were the conditions considered in the study. The experimental results demonstrate remarkable accuracy of 98.57% in diagnosing faults, marking a significant advancement in enhancing the reliability and performance of PV modules. This research contributes to the sustainability and efficiency of renewable energy systems, underlining its importance in the quest for a cleaner, greener future., Validerad;2024;Nivå 2;2024-04-04 (joosat);Full text license: CC BY-NC-ND

Reliable fuel consumption measurements play an essential role in the maritime sector whether for emission determinations or the use of novel fuels. A verification of the performance of flow meters used for fuel consumption determination under realistic conditions is thus of interest. Apart from the influence of the pressure- and temperature-dependent transport properties of the fuels, a characterization of the measurement performance under dynamic fuel consumption is of relevance. Traceable metrological infrastructure and procedures, which will enable an evaluation of the measurement performance of flow meters in this regard, are being developed in the scope of the EMPIR project “Safest” (20IND13). A consumption profile of a ferry navigating in a harbour serves as basis. In addition to the measurement accuracy under dynamic conditions, first investigations of the performance of flow meters are carried out in terms of fluid temperature and fuel transport properties for the example of spindle screw meters., This project (EMPIR JRP 20IND13 SAFEST) has received funding from the EMPIR programme co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation programme.

Rapid performance prediction tools are required for the evaluation, optimization, and comparison of different wind propulsion systems (WPSs). These tools should capture viscous aerodynamic flow effects in 3D, particularly the maximum propulsion force, stall angles, and interaction effects between the lift-generating units. This paper presents a rapid aerodynamic calculation method for wing sails that combines a semi-empirical lifting line model with a potential flow-based interaction model to account for 3D interaction effects. The method was applied to a WPS that consisted of several wing sails with considerable interaction effects. The results were compared to CFD RANS simulations in 2D and in 3D. For the evaluated validation cases, the interaction model improved the prediction considerably compared to when the interaction was not accounted for. The method provided acceptable driving force, moments, and stall predictions, with negligible computational cost compared to 3D CFD simulations., This research was funded by the Swedish Energy Agency , grant number 2022/P2021-00275 . The 3D CFD simulations were enabled by resources provided by the National Academic Infrastructure for Supercomputing in Sweden (NAISS) and the Swedish National Infrastructure for Computing (SNIC) at the Chalmers Centre for Computational Science and Engineering (C3SE), High Performance Computing Center North (HPC2N) and Uppsala Multidisciplinary Center for Advanced Computational Science (UPPMAX) partially funded by the Swedish Research Council through grant agreements no. 2022-06725 and 2018-05973

The optimization of sawing processes in the wood industry is critical for maximizing efficiency and profitability. The introduction of computerized tomography scanners provides sawmill operators with three-dimensional internal models of logs, which can be used to assess value and yield more accurately. We present a methodology for solving the sawing optimization problem employing a flexible sawing scheme that allows greater flexibility in cutting logs into products while considering product quality classes influenced by wane defects. The methodology has two phases: preprocessing and optimization. In the preprocessing phase, two alternative algorithms are given that generate and evaluate the potential sawing positions of products by considering the 3D surface of the log, product size requirements, and product quality classes. In the optimization phase, a maximum set-packing problem is solved for the preprocessed data using mixed-integer programming (MIP), aiming to obtain a feasible cut pattern that maximizes value yield. This is implemented in a system named FlexSaw, which takes advantage of parallel computation during the preprocessing phase and utilizes a MIP solver during the optimization phase. The proposed sawing methods are evaluated on the Swedish Pine Stem Bank. Additionally, FlexSaw is compared with an existing tool that utilizes cant sawing. Results demonstrate the superiority of flexible sawing. While the practical feasibility of implementing a flexible way of sawing logs is constrained by the limitations of current sawmill machinery, the potential increase in yield promotes the exploration of alternative machinery in the wood industry., This work was supported by Sweden’s Innovation Agency (VINNOVA) via BioInnovation under grant 2020–03734.

The current global changes and regulations in sustainability have a direct impact on suppliers to the automotive industry. Therefore, it is crucial for suppliers to the automotive industry to proactively monitor developments to avoid risking their competitiveness. This involves an increased focus on documentation and compliance with sustainability policies and certifications. Company X is a family-owned company located in Gnosjö, operating for nearly 80 years and supplying products to the automotive industry, among other sectors. The company specializes in industrial work and focuses on machining (turning and milling). To remain competitive and, above all, relevant for at least another 80 years, they strive for continuous development to meet customer demands. The guiding philosophy is to operate within the ”Global Automotive Sustainability Guiding Principles”, which clarify the automotive industry ́s expectations regarding sustainability efforts from their suppliers. In late 2022, Drive Sustainability, responsible for creating and maintaining the Self-Assessment Questionnaire (SAQ), raised the requirements from SAQ 4.0 to SAQ 5.0. The consequence of not being approved before June 2023 is the inability to initiate new business as a supplier to Scania. The thesis was conducted at Company X with the aim of investigating what is required for Business X to upgrade from SAQ 4.0 to SAQ 5.0. This involved identifying any gaps in the company’s environmental and quality management systems in relation to the SAQ portal. The project also aimed to examine whether the current quality and environmental management system needs adjustment to better reflect data in the SAQ portal. The main task of the author was to explore possible solutions to help Company X and other SMEs implement the SAQ process in a resource-efficient manner. To achieve the study ́s purpose, an analysis of the documentation in the company ́s environmental and quality management systems in relation to the SAQ po

As the world is evolving faster and technology gets cheaper and more powerful, simulations are proving to be more and more beneficial. Simulations allow for faster development with less lead time between iterations which means that product versions can be released more often and at less cost. The automotive industry is heavily affected by emission legislation and environmental politics. The development of more environmentally friendly engines forces the rate of development to speed up. Simulations allow the industry to keep up with the increasing requests for more complex systems. For software development, it speeds up the process significantly. Although real-life testing in engine test cells and test cars still sets the foundation for and validates the results of the simulations, simulations can drastically decrease the amount needed. Less unnecessary real-life testing with bugs in the software causing wasted time and cost. In the meantime, more iterations can be tested in a smaller time frame, making the actual real-life testing more valuable and giving. The aim of this thesis is to develop a method to convert an accurate but relatively slow simulation model of the airflow through an engine, into a faster-running format preparing it to run in close to Real-Time and with a fixed timestep. Then exporting the converted model as a functional mock-up unit, FMU, a standardised entity, part of the Functional Mock-up Interface standard. The FMU was to be used in Software in Loop, SiL, simulations using it in cooperation with Matlab Simulink and Synopsys Silver. The SiL environment is then to be used to develop and test calibration software for the engine in question.

These days, lightweight materials such as aluminum alloy sheets, especiallythose in the AA6xxx series, are in high demand for use inthe automotive industry. During natural aging, the properties of aluminummay undergo significant changes due to the diffusion of atomswithin the crystal structure, impacting the strength and formabilityof aluminum sheets. This phenomenon prompts suppliers to carefullyassess the appropriate duration of storage concerning the minimal rateof change and stability in mechanical properties. This study aims toinvestigate the effects of natural aging at room temperature on themechanical properties of two aluminum alloys AA6014 and AA6016,over predefined 10, 100, and 1000 hours. The Digital Image Correlationmethod and MATLAB employed alongside uniaxial tensile teststo estimate changes in Young’s modulus, yield strength, ultimate tensilestrength, and localized necking strain across three material anglesand three tensile load speeds during these specific time periods.Thisstudy aims to investigate the impact of natural aging on the mechanicalproperties of aluminum alloys, specifically AA6014 and AA6016with the goal of identifying the ideal storage duration that minimallyaffects their mechanical characteristics. Subsequently, it suggests therecommended strain rate for optimal time periods. To achieve thisgoal, over two hundred and sixty experiments have been conducted.How ever,the results indicated that,despite the two aluminum alloyshaving similar specifications, distinct behaviors were observed duringthe process of natural aging.Keywords: Aluminium Alloys 6014 and 6016, Mechanical properties,Strain rates, Natural aging.

This master thesis explores the implementation of Collaborative robots into Elekta's mechanical product verification process. Elekta is a pioneer in precision radiation therapy solutions. Ensuring the compliance of Elekta's products with performance, safety, and quality criteria is of great importance. The existing verification process faces challenges regarding resource management, ergonomics, efficiency, and test accuracy.This thesis delves into three main research areas, the study begins with theoretical research investigating Industry 4.0, automation, and human-robot collaboration, focusing on the ABB GoFa Cobot. The following research area analyzes the existing market, regarding the exploration of different robotic grippers. Lastly, the third research area focuses on the user. Including interviews and observations with Elekta testing employees and industry experts from ABB and Atlas Copco.This thesis examines insights from theoretical, market, and user research to identify key factors influencing the development of concepts, prototypes, and models. By this, strengths, weaknesses,and a criteria value matrix were created for various gripper options for Elekta's tests. Furthermore, test parameters were defined to make the test suitable for automated Cobot verification. Lastly, the conclusion from the user research was examined in several parts, including, efficiency, safety, ergonomics, limitations, robotics, and industry. The thesis continued with a creative process that contains the development and iterations of concepts by CAD modeling, 3D printing, and Cobot programming for a specific verification test. The results of this thesis include Cobot implementation guidelines, covering the selection of suitable tests for automation, gripper selection, and finger development. The report then delves into the sustainable regards related to Cobot implementation, studying social, economic, and environmental sustainability. Furthermore, decisive factors that could influenc, Denna masteruppsats utforskar implementeringen av kollaborativa robotar i Elektas mekaniska produktverifieringsprocess. Elekta är en pionjär inom precisionslösningar för strålterapi. Det är av stor vikt att säkerställa att Elektas produkter överensstämmer med kriterierna för prestanda, säkerhet och kvalitet. Den befintliga verifieringsprocessen står inför utmaningar när det gäller resurshantering, ergonomi, effektivitet och testnoggrannhet. Denna avhandling fördjupar sig i tre huvudsakliga forskningsområden, studien börjar med teoretisk forskning som undersöker Industri 4.0, automation och människa-robotsamarbete, med fokus på ABB GoFa Cobot. Följande forskningsområde analyserar den befintliga marknaden, avseende utforskning av olika robotgripare. Slutligen fokuserar det tredje forskningsområdet på användaren. Inklusive intervjuer och observationer med Elekta som testar anställda och branschexperter från ABB och Atlas Copco. Denna uppsats undersöker insikter från teoretisk forskning, marknads- och användarundersökning för att identifiera nyckelfaktorer som påverkar utvecklingen av koncept, prototyper och modeller. Genom detta skapades styrkor, svagheter och en kriterievärdesmatris för olika gripalternativ för Elektas tester. Dessutom definierades testparametrar för att göra testet lämpligt för automatiserad Cobot-verifiering. Till sist undersöks slutsatser från användarforskningen i flera delar, inklusive effektivitet, säkerhet, ergonomi, begränsningar, robotik och industri. Examensarbetet fortsatte med en kreativ process innehållande utveckling och iterationer av koncept genom CAD-modellering, 3D-utskrift och Cobot-programmering för ett specifikt verifieringstest. Resultaten inkluderar riktlinjer för implementering av Cobot inom industrin, som täcker valet av lämpliga tester för automatisering, val av gripdon och utveckling av fingrar anpassade efter gripdonet. Rapporten fördjupar sig sedan i de hållbara aspekterna relaterade till Cobot-implementering, genom att st

This thesis emerged from a question that had been repeating itself in my head for a long period of time: If myself and the rest of the world face the fact that we are likely to keep flying for years to come for reasons somehow considered valid, how can we at the same time still contribute efficiently to achieving a more sustainable future of aviation? Based on this dilemma and focusing on the factor of impact, an actor with the power of creating a larger impact than a single individual was firstly identified. This actor also provides the perspective used in this thesis. Meaning, the perspective of international companies that rely on flying for business for the purpose of surviving and thriving. The report’s purpose is to explore the opportunities and barriers for these companies with a will to contribute to the transformation to a future of sustainable aviation. The criteria of this company category are being both “international” and also “dependent” on business aviation. The term "international" in this context will later be defined and clarified, just as the definition of "dependent". Furthermore, this thesis is written based on an abductive literature study combined with a case study of an anonymous company located in Zürich, Switzerland. The Companyis included in the above category and could validate the hypothesis that companies like these exist through a series of interviews with employees.The validation of this hypothesis also paved the way to further explore the research questions on how these companies as customers can work both internally and externally with other stakeholders to enhance a Demand-Pull effect towards a more sustainable direction. It also discusses the Technology-Push effect from other stakeholders and its role in driving sustainable innovation development and implementation in technologies such as SAF, hydrogen and electric aviation. How to contribute to this large shift of an entire industry as a company that neither has expertise in sust, Detta arbete härstammar från en fråga som upprepat sig i mitt huvud under en längre tid: Om jag och resten av världen står inför det faktum att vi sannolikt kommer att fortsätta flyga i flera år framöver av skäl som på något sätt anses giltiga, hur kan vi samtidigt fortfarande bidra effektivt till att uppnå en mer hållbar framtid för flygindustrin? Utifrån detta dilemma och med fokus på hur man kan påverka som mest, identifierades först en aktör med kraften att skapa ett större genomslag än en enskild individ. Denna aktör bidrar också med det perspektiv som används i denna rapport. Det vill säga, perspektivet av internationella företag som är beroende av att flyga i affärssyfte för att överleva och växa. Syftet med rapporten är att utforska möjligheter och hinder för dessa företag med en vilja att bidra till omvandlingen till en framtid för hållbart flyg. Kriterierna för denna företagskategori är att vara både "internationell" och även "beroende" av affärsflyg. Termen "internationell" i detta sammanhang kommer senare att definieras och förtydligas, precis som definitionen av "beroende". Vidare är denna uppsats skriven baserat på en abduktiv litteraturstudie kombinerad med en fallstudie av ett anonymt företag beläget i Zürich, Schweiz. Företaget ingår i ovan nämnda kategori och kan därmed validera hypotesen att företag som dessa existerar genom en serie intervjuer utförda med anställda. Valideringen av denna hypotes banade också vägen för att ytterligare utforska frågeställningen om hur dessa företag som kunder kan arbeta både internt och externt med andra intressenter för att förstärka en Demand-Pull-effekt mot en mer hållbar riktning. Rapporten diskuterar också Technology-Push-effekten från andra intressenter och dess roll i att driva hållbar innovationsutveckling och implementering inom teknologier som SAF, vätgas och elflyg. Hur ett företag kan bidra till detta stora skifte av en hel bransch utan kompetens inom hållbarhet eller flyg är precis vad som presenteras

Introduction: Additive manufacturing (AT) also known as 3D printing has become a more widespread technology in various industries. The manufacturing method has increased the efficiency of manufacturing industries in producing products with technically challenging properties. Through continuous research and development, AT could compensate for traditional working methods and strive to reduce material and time loss as well as manufacturing costs. Purpose: The project aims to investigate how additive manufacturing can be used to create molds with accuracy and precision. It will also be explored how these molds will result in injection molding with high precision and accuracy. To obtain relevant data, a suitable material must be selected for injection molding. To realize this, it is necessary to define which parameters are required and how a mold should be constructed. The goal of the project has resulted in the formulation of two research questions: Q1: How can Additive Manufacturing (AT) be applied to make molds? Q2: Which parameters can be identified to optimize the quality of the mold and thereby achieve good precision and accuracy of the injection molded product? Method: Within the work, both qualitative and quantitative research has been conducted. The information gathered is based on scientific articles, relevant literature, and the execution of a case study in collaboration with Mälardalen industrial Technology Center (MITC). An abduction approach was used where data from both the literature and the case study were found continuously. During the process, the writers were allowed to develop a deeper understanding of the area which enabled the generation of new data from the literature and articles. By using these two data types in an iterative process to verify information, it increases validity and reliability. Conclusion: Within the case study, it was observed that SLA 3D printing was not completely accurate and produced unexpected results. The distinction betw, Introduktion: Additiv tillverkning (AT) även känd som 3D-printning har blivit en alltmer utbredd teknologi inom olika industrier. Framställningsmetoden har ökat effektiviteten för tillverkningsindustrier när det gäller att producera produkter med tekniskt utmanande egenskaper. Genom kontinuerlig forskning och utveckling har AT potentialen att ersätta traditionella arbetssätt och sträva efter att reducera material-och tidsförlust samt kostnader på tillverkning. Syftet: Projektet syftar till att undersöka hur additiv tillverkning kan användas för att skapa gjutformar med hög noggrannhet och precision. Det ska även utforskas hur dessa gjutformar kommer att resultera i formsprutningar med hög precision och noggrannhet. För att erhålla relevant data ska ett lämpligt material väljas för formsprutning. För att förverkliga detta är det nödvändigt att definiera vilka parametrar som erfordras och hur en gjutform bör konstrueras. Målet med projektet har resulterat i formulering av två forskningsfrågor: F1: På vilket sätt kan Additiv Tillverkning (AT) tillämpas för att tillverka gjutformar? F2: Vilka parametrar kan identifieras för att optimera gjutformens kvalitet och därmed uppnå god precision och noggrannhet på formsprutad produkt? Metod: Inom arbetet har både kvalitativ och kvantitativ forskning utförts. Informationen som har samlats in är baseras på vetenskapliga artiklar, relevant litteratur samt utförande av en fallstudie i samarbete med Mälardalen Industrial Technology Center (MITC). En abduktionsansats användes, där data från både litteratur och fallstudien löpande integrerades. Under processens gång utvecklade skribenterna en djupare förståelse av området som, vilket möjliggjorde generering av nya data från litteratur och artiklar. Genom att använda dessa två data typer i en iterativ process för att verifiera information, ökas studiens validitet och reliabilitet. Slutsats: I fallstudien framkom det att SLA 3D-printning inte var helt noggrann och ger oväntade resulta

This master thesis studies alternative energy sources for maritime shipping in Sweden. With current climate goals, and a need for change, the maritime sector currently undergoes intense transitions. For shipping companies to lower their carbon footprint, the need to replace non decarbonised fuels is hence critical. With numerous alternatives, currently being developed, actors are phasing obstacles regarding which energy source that is most mature in terms of technical readiness as well as how adequate it will fulfil current climate goals. This study will analyse four different energy sources, liquid hydrogen (LH2), electro-methanol (emethanol), electro-ammonia (e-ammonia) and wind (sails), and answer which out of these energy sources will be most suitable for actors to adapt. To answer this question, the Technological Innovation System framework has been utilised, and the results has been applied to some chosen climate target actions developed by Swedish authorities. The findings proved that e-methanol currently is most mature and has reached most alignment with current climate goals, followed by LH2/wind and lastly e-ammonia., Detta examensarbete studerar alternativa energikällor för fraktfartyg i Sverige. Med nuvarande klimatmål, och ett behov av förändring, genomgår den maritima sektorn intensiva omställningar. För att rederier ska kunna sänka sitt koldioxidavtryck är behovet att ersätta icke koldioxidneutrala bränslen därför stort. Med ett flertal alternativ, som för närvarande är under utveckling, står aktörer inför hinder angående vilken energikälla som är mest redo gällande teknikmognadsgrad samt hur adekvat den kommer att uppfylla nuvarande klimatmål. Denna studie kommer att analysera fyra olika energikällor, flytande väte (LH2), elektro-metanol (e-metanol), elektro-ammoniak (e-ammoniak) och vind (segel), och ta reda på vilka av dessa energikällor som är mest lämpad för aktörer att använda sig av. För att svara på denna fråga har ramverket Technological Innovation Systems använts och resultaten har tillämpats på några utvalda klimatmålsåtgärder som tagits fram av svenska myndigheter. Resultaten visade att e-metanol för närvarande är mest mogen och har nått mest anpassning till nuvarande klimatmål, följt av LH2/vind och slutligen e-ammoniak.

I Sverige finns det ungefär 2,5 miljoner ljuspunkter på statliga vägar och kommunala gator. Den huvudsakliga funktionen är att förbättra synförhållandena i trafiken, men den syftar även till att öka komfort, motverka brottslighet, samt skapa trivsel. I den här förstudien har RISE, tillsammans med 8 aktörer från gatubelysningssektorn, utforskat hur värdekedjan kan leverera de värden som offentlig belysning bidrar till med färre resurser och mindre negativ påverkan på människa och miljö än vad som görs i dag. Förstudien har utvärderat cirkularitet utifrån tre dimensioner i) att använda armaturer och dess komponenter länge, ii) att använda gatubelysningens resurser ändamålsenligt, och iii) att återcirkulera uttjänt material och att använda återcirkulerat material. En huvudsaklig slutsats är att begreppet cirkulär förmodligen är för brett för att användas i sin helhet, och att begreppet med fördel bör brytas ner till mindre beståndsdelar, för att enklare ta steg åt rätt riktning. Det underlättar för offentlig upphandling att ställa krav för förbättrad cirkularitet genom att bryta ner begreppet till mindre mål och strategier för att minska resursflödet, främst av jungfruligt material men även totalt. Detta för att det inte är tydligt i dag vad sektorn bör fokusera på. Utöver cirkulära krav på armaturerna har offentliga aktörer en viktig roll i gatubelysningens resursanvändning och påverkan på människor och biologisk mångfald genom deras beslut om var och hur mycket belysning som ska finnas, hur ofta och hur starkt den ska lysa. Två identifierade utmaningar är i) att integrerade komponenter i LED-armaturer försvårar reparation och möjlighet till återbruk, och ii) att det är svårt att sia vilka förändringar som kan komma att ske på 25 år. På ett kvarts århundrade finns mycket tid för teknologisk utveckling, ändrade krav på armaturer, eller ny lagstiftning som begränsar möjligheten att använda armaturer baserade på dagens design. På aggregerad nivå finns den största klimatb

At the onset of the pandemic in spring 2020, the Swedish shipping sector was first affected by border closures preventing passengers to use RoPax shipping and cruise ferries. There were some blank sailings but in general they kept operating to foster intra-European trade by trucks despite the missing revenues from passengers. Shipping in general was affected by port disrup-tions and complicated crew changes. Eventually, however, it was clear that the most dramatic disruptions on a global scale where experienced in the container segment. General media reported on delayed goods, high freight rates and, however not related to the pandemic, the Ever Given blocking the Suez Canal for a week in March 2021. Currently, there are few reports of supply chains and shipping suffering from disruptions and capacity constraints related to the pandemic. The peak in freight rates was rather replaced by depressed rates and there is a certain risk that some logisticians and supply chain managers regard the pandemic as a once-in-a-lifetime event and just want to get back to a previous be-haviour seeing container shipping as a commodity with indefinite capacity at a reasonable price. Nevertheless, the war in Ukraine, the drought in the Panama Canal and the attacks by the Houthi rebels in the Red Sea create other problems for container shipping. Freight rates increase significantly, but from very low levels. The purpose of the report is to describe and analyse how international container shipping was affected by the Covid-19 pandemic and other disruptions. The analysis takes a Swedish perspective on disruptions and tries to go beyond the anecdotal reporting and capture what happened and why. Container shipping is put into a context of economy, consumption, world trade, supply chains and logistics. The pandemic and more current events affecting container shipping market are described together with how shipping lines responded. A series of interviews with Swedish actors revealed how they p, This work was funded by the Swedish Transport Administration through the project The role of liner shipping for robust supply chains (Linjesjöfartens roll för robusta försörjnings-kedjor) and Lighthouse through the pre-study projects Shipping post-covid (Sjöfarten post-corona) and Regionalised supply chains and the effects on shipping (Regionaliserade försörjning-skedjor och påverkan på sjöfarten). In addition, University of Gothenburg and Chalmers have funded parts of the work through the joint Strategic Research Area Transport.

Digitalization and automation in industry can have both positive and negative effects on social sustainability. On one hand it can be a basis for monotonous, uncreative, and even dangerous workplaces and in some cases might even result in people losing their work. On the other hand, it can be a base for ergonomically sound and inclusive work, engaging everyone in improvements. This project aims for moving the focus on positive effects for social sustainability while still staying cost efficient and effective in economic and ecologic sustainability for digitalization and automation of work instructions and training in manual operations like assembly, machine operation & setup, maintenance, and material handling. The Industry 4.0 paradigm offers radically increased opportunities for doing just that. For example, increased digitization can create efficiency improvements through shorter lead times and reduced disruptions to production. New generations of technology and software as well as information dissemination can be accelerated and the traceability of products and materials in the industrial systems can be greatly increased. Digitization also provides opportunities to increase industrial resilience to challenges coming from elsewhere, such as demographic change and climate threats. Advanced application of digitization is seen by industries and decision-makers as the most important enabler for achieving the strategic sustainability goals and Agenda2030. A crucial factor for competitiveness is the human contribution. Here too, digitalisation is radically changing the conditions. In the last 20 years, work instructions have been transformed from printed text on paper into an increasingly digital representation. As knowledge increases about how work instructions for the manufacturing industry should be designed, they are rarely designed according to user conditions. At best, this results in a missed opportunity for performance improvements and at worst, it could po, First year report of DIGITALIS1 (DIGITAL work InStructions for cognitive work)1The project is funded by Swedish innovation agency Vinnova through the strategic innovation program Produktion2030. The following partners are included in DIGITALIS: Skövde University, Research Institutes of Sweden, Chalmers University of Technology, Husmuttern AB, SAAB AB, Volvo Powertrain, Swegon AB, CEJN AB, Hitech & Development Wireless Sweden and ESI Group.

The acoustic guitar is a stringed instrument, often made of wood, that transduces vibrational energy of steel strings into coupled vibrations of the wood and acoustic pressure waves in the air. Variations in wood selection and instrument geometry have been shown to affect the timbre of the acoustic guitar. Computational methods were utilized to investigate the impact of material properties on acoustic performance. Sitka spruce was deemed the most suitable wood for guitar soundboards due to its acoustic characteristics, strength, and uniform aesthetic. Mahogany was deemed to be the best wood for the back and sides of the guitar body due to its greater sensitivity to pressure difference, strength, and impedance matching with Sitka spruce.

Education plays a crucial role in promoting actions that mitigate climate change, enhancing understanding of the consequences of human actions on ecosystems and providing the knowledge, values and skills necessary for engineering students to act as agents of change. This article stems from documentary research aimed at reviewing Mechanical Engineering programs in Colombia, exploring their relationship and pertinence to environmental sus-tainability and the Sustainable Development Goals (sdg) No. 6, 7, 11 and 13. The methodological design aligns with the critical social paradigm, employing a qualitative approach through a descriptive and projective study. The study involves characterizing a sample of 15 Mechanical Engineering programs, analyzing the relevance of professional training concerning environmental sustainability. The survey conducted revealed that a significant portion of the ex-isting educational offerings in Mechanical Engineering programs does not align with the objectives of sustainability. Consequently, updating curricula is proposed as an opportunity to reflect, make them more flexible, and renew them to address the current environmental needs of the planet., A educação é um elemento essencial na promoção das ações que mitigam a mudança climática e melho-ram a compreensão das consequências da ação humana nos ecossistemas, fornecendo os conhecimentos, valores e habilidades necessários aos estudantes de engenharia para atuarem como agentes de mudança. Daí o objetivo que originou este artigo, fruto de uma pesquisa documental que revisou os programas de engenharia mecânica na Colômbia, ser a busca de sua relação com a sustentabilidade ambiental e os Objetivos de Desenvolvimento Sustentável (ods) n.º 6, 7, 11 e 13, por estes estarem mais diretamente relacionados com a mudança climática. O desenho metodológico se enquadrou no paradigma crítico-social, com um enfoque qualitativo através de um estu-do de tipo descritivo e projetivo, com a caracterização de uma amostra de 15 programas de engenharia mecânica, nos quais foi analisada a pertinência da formação profissional em relação à sustentabilidade ambiental. A pesquisa realizada permitiu identificar que grande parte da oferta educativa existente de programas de engenharia mecâni-ca não corresponde ao alcance desses objetivos de sustentabilidade. Por este motivo, sugere-se a atualização dos currículos como uma oportunidade para refletir, flexibilizar e renovar esses programas, de modo a responder às necessidades atuais e ambientais do planeta., La educación es un elemento esencial en la promoción de las acciones que amainan el cambio climático y mejora la comprensión de las consecuencias del accionar humano en los ecosistemas, proporcionando los conocimientos, valores y aptitudes que necesitan los estudiantes de ingenieríavpara actuar como agentes de cambio. De ahí que el objetivo que da origen al presente artículo, fruto de una investigación documental que revisó los programas de ingeniería mecánica en Colombia, sea la búsqueda de su relación con la sostenibilidad ambiental y los Objetivos de Desarrollo Sostenible (ods) N.º 6, 7, 11 y 13, por ser estos los más directamente relacionados con el cambio climático. El diseño metodológico se enmarcó en el paradigma crítico-social, con un enfoque cualitativo a través de un estudio de tipo descriptivo y proyectivo, con la caracterización de una muestra de 15 programas de ingeniería mecánica, en el que se analizó la pertinencia de la formación profesional en relación con la sostenibilidad ambiental. El sondeo realizado permitió identificar que gran parte de la oferta educativa existente de programas de ingeniería mecánica no corresponde al alcance de dichos objetivos de sostenibilidad. Por este motivo, se sugiere la actualización de los currículos como una oportunidad para reflexionar, flexibilizar y renovar estos programas, de manera que respondan a las necesidades actuales y ambientales del planeta.

In this work, I developed and tested designs for increasing energy efficiency in threeareas: soft robotics, buildings, and jumping.In the area of soft robotics, researchers are interested in using low-boiling point fluids topower pneumatic soft robots, because they can produce large volumes of pressurized gas without the need for bulky pumps and tubing. While this approach is effective at doing work via pressurized vapor, it is highly inefficient. One way to reduce energy consumption from onboard sources (e.g., batteries) is to harvest it, and another way is to improve the energy conversion process directly. In my work, I developed soft robots that can detect heat and light sources and use ambient thermal energy to locomote up to 10 m. I also developed strategies to improve efficiency by nearly two orders of magnitude.In the area of buildings, efficient thermal regulation is a major challenge; currently, halfof US building energy usage goes towards heating and cooling. One way to increase efficiency in heating and cooling is to take advantage of the Sun and deep space, respectively, via radiative heat transfer. For my work, I designed and tested a mechanical radiative switch in the form of a roofing tile. It helps save energy by passively switching between radiative heating and cooling states. Unlike previous passive designs, my design switches over a small range of temperatures (15 °C). Tests show potential energy savings of at least 2.5× for heating and cooling compared to similar non-switching devices.In the area of jumping, engineers have built jumpers that can achieve jump heights >30m; while impressive, an estimated 50% of the energy is lost before takeoff. To reduce the energy loss, I developed and analyzed new jumper designs. Preliminary experimental results show that these new designs can improve jump height. My findings can help make future jumping robots more efficient at converting spring potential energy into vertical center of mass kinetic energy, s

Fluid-driven subsurface fractures interact with a variety of heterogeneous elements in the surrounding environment, including fluid-filled pores, material discontinuities, and other cracks and fissures. Their complex propagation is governed by fluid-solid interactions, characterized by nonlinear and coupled dynamics between the flow and the fracture. This thesis focuses on addressing a variety of such problems related to fluid-driven fractures or hydraulic fractures within increasingly realistic situations. Initially, we examine the post-shut-in behavior of a hydraulic fracture in the viscous regime, where viscous dissipation is the dominant form of energy dissipation. Subsequently, we investigate the propagation of a hydraulic fracture driven by displacement flows of two immiscible fluids and the propagation of a hydraulic fracture across a material discontinuity.When pressurized fluid is injected in a homogeneous infinite solid medium, a simple penny-shaped fracture forms and grows in the direction of the minimum confining stress. This type of fracture offers a representative focus for experimental investigations in a laboratory environment, serving as a powerful tool to understand the various physical mechanisms governing the growth of the fracture. Throughout the thesis, we vary different material properties of the solid media and fracturing fluids, including the Young's modulus of the solids, the viscosity of the fluids and, the flow rate of the injection. Gelatin serves as the clear brittle elastic solid medium, that allows us to observe and record the fracture growth because of its transparent nature. In the first study, we examine the post-shut-in behavior of a penny-shaped hydraulic fracture in the viscous regime. We measure both the fracture aperture and radius, noting that the fracture radius continues to grow slowly over time even after injection stops, until it reaches a saturation point.Next, we investigate the injection of an immiscible fluid at the c

Natural materials have long inspired the design and fabrication of advanced materials. Characterized by intricate structures featuring hierarchical porosity, spatial heterogeneities, and architectural gradients, these materials offer unique combinations of stiffness, strength, and toughness at low density. Inspired by nature, this thesis explores the development of advanced materials through two distinct avenues.In the initial investigation, the adhesive capabilities of marine mussels are examined on various geometry-controlled surfaces. Through mechanical tests, the adhesion strength of mussel structures is assessed, revealing consistent detachment forces . This suggests their robustness to different substrate geometries. Subsequent scanning electron microscopy (SEM) analysis reveals substrate-dependent damages within microstructures, indicating that mussels are capable of changing damage mechanisms to maintain characteristic pull-off force, suggesting their adaptability to geometric conditions. Building upon the insights gained from natural materials, subsequent work focuses on the development of advanced materials using additive manufacturing (AM) techniques. Specifically, digital light processing (DLP) of photocurable resins combined with thermally expandable microspheres is employed to create polymer composite foams that are lightweight yet stiff. A two-step material processing approach enables precise control over porosity with tunable mechanical properties of the materials. Through mechanical analysis under compression, we elucidate how foaming alters the mechanics of the composite material, including changes in modulus, Poisson’s ratio, energy dissipation, and fatigue performance. In the final chapter, we investigate thermally induced transformations in the properties of the polymer foams. We observe that 3D-printed objects undergo extra-curing upon heating above the expansion temperature of the microspheres, indicating that the materials bear latent transfo

A longstanding goal in haptics is to engineer high-fidelity displays for spatially distributed haptic feedback, specified as digital media. Such haptic displays would make it possible to touch, feel, and interact with dynamic scenes, objects, or information presented anywhere in a continuous display medium, such as an interactive surface or three-dimensional environment. They would thus represent the haptic analogs of two- or three-dimensional video displays. This dissertation advances knowledge in the design and operational principles of such haptic displays, focusing on emerging technologies that harness and control propagating mechanical waves to deliver spatially distributed haptic feedback. Central to the innovation of wave-mediated haptic display is that the spatial resolution of haptic feedback is governed by the control of wave transmission rather than by the number and density of actuators, as would be the case in conventional approaches. This wave-mediated strategy reduces complexity, enabling practical and scalable displays capable of reproducing dynamic haptic media. This Ph.D. dissertation contributes new display designs exploiting wave transmission, algorithms and methods for wave-mediated haptic display, experimental findings that mechanically and perceptually characterize the proposed display methods, and investigations of the influence of skin biomechanics on display fidelity.The first part of this dissertation details two wave-mediated surface haptic displays composed of soft elastomers, which reproduce software-specified haptic media via viscoelastic wave field control. These displays can generate haptic feedback at multiple, arbitrary display locations with sub-centimeter resolution and accuracy using only a limited number of remotely positioned actuators. Using high-resolution measurements of wave field surface oscillations and behavioral studies, I also evaluate several proposed rendering algorithms that generate expressive, dynamic haptic cont

Branching morphogenesis is a fundamental process that occurs during the development of the mammary gland, and several signaling pathways that regulate mammary branching are disrupted during the development and progression of breast cancer. Much of our current understanding of morphogenesis comes from the effects of chemical morphogens, though recent work has revealed that the mechanics of the extracellular matrix (ECM) can regulate morphogenetic events. Conventionally, tissue development has been studied with ex vivo systems where mechanical properties of the extracellular environment are either poorly controlled in space and time, lack tunability, or do not mimic the native extracellular matrix mechanics. For these reasons, it remains unknown how matrix stress relaxation rate, a time-dependent mechanical property shown to influence several cellular functions and processes, regulates tissue branching in mammary development. My objective here is to determine the effect of ECM viscoelasticity on mammary branching using 3D collagen-rich matrices with tunable stress relaxation and spheroids of human mammary epithelial cells.

This report investigates the kinetics of lubricant molecules in the HAMR air bearing to understand the initiation and growth of PFPE contamination on the head surface. The collisions with the air bearing induce three forces—drag, thermophoresis, and lift. Of these, we find that lift forces are negligible. Then, a sensitivity analysis of the remaining two forces reveals the conditions where they dominate. Further, a hybrid simulation strategy is utilized to track their movements. The results show that the contaminations (smear) highly depend on the interplay between the thermophoresis and drag forces. We then explain the mechanism of the formation of the various observed patterns. Finally, we offer some recommendations to exploit the air bearing to contain smear on the head.

A multiscale micromechanics-based progressive damage model is developed to investigate the overall mechanical behavior and the interfacial microcrack evolutions of the cementitious composites featuring superabsorbent polymer (SAP) under uniaxial tension. Elastic properties, progressive damage process, and homogenization procedure of cementitious composites are systematically integrated in this model. The effective elastic moduli of the composites are determined based on a multiscale micromechanical framework. According to the small strain assumption, the total strain tensor and the elastic-damage compliance tensor are additively decomposed into elastic and damage-induced components. The damage-induced strains and compliances are then deduced from micromechanics. To characterize the progressive elastic-damage induced by microcracks, stages of microcrack propagation are identified from the interface contact stress and the matrix cleavage stress. The complex potentials and stress intensity factors for kinked interface cracks are derived from the distributed dislocations method. By implementing the homogenization process, the macroscopic mechanical behavior is obtained from the micro/mesoscale. The results indicate that the material parameters have clear mechanical significance. Different parameters, such as the SAP addition ratio, aggregate content, initial interfacial crack size, and initial interfacial crack location, are revealed to be influential in the overall mechanical behavior of the composites. The proposed model can be generalized to other particle-reinforced composites with different constituent properties, which can potentially contribute to the design and optimization of durable composites.

Electric multirotor aerial vehicles are an emerging technology with extensive potential applications across a wide range of fields, but flight time and range limitations currently impose significant constraints on the use of such vehicles. Improving the vehicle energy performance is therefore a critical research topic, and one promising strategy is to optimize operational energy efficiency through model-based motion planning and control. While there has been extensive research on the topic and important progress has been made, existing works generally oversimplify or disregard key vehicle subsystem behaviors, and therefore fail to capture the complete energy dynamics and exploit the full energy saving potential. To address this gap in the state of the art, a complete system-level vehicle model is developed and applied to planning and control, aiming at achieving significant energy performance improvements in this dissertation.The model captures all relevant subsystem dynamics related to the vehicle energy performance, including propeller aerodynamics, motor assembly electro-mechanical dynamics, battery electrical dynamics, and airframe rigid-body dynamics. Through experimental validation, the model demonstrates a high degree of fidelity over a wide range of operating conditions. The model is then used to demonstrate the importance and necessity of incorporating individual dynamics into model-based planning and control, highlighting the impact of battery dynamics on the propulsion limits, the influence of propeller (inflow) aerodynamics on the energy performance, and the breakdown of vehicle energy efficiency to each subsystem dynamics. An energy-optimal trajectory generation and feedback control framework is then developed based on this model, and is shown to reduce energy usage significantly relative to a baseline controller in both simulations and experimental validation over a range of waypoint-to-waypoint flight operations. Polynomial approximations of the optim

Hybrid rockets have recently become a more and more desirable method for small satellitepropulsion, due to their lack of safety issues compared to their liquid and solid rocket counterparts. A major reason for this is because the fuel and oxidizer are both separated by distance and state when stored in a hybrid rocket. This also makes it relatively more difficult to ignite and start up the rocket. While many igniter systems have been invented, currently no reliable, self-igniting system has been flown. Recently, a Hydrogen-Oxygen torch was designed, built, and tested in UC Davis’ Energy Research Lab. Methane is typically used in torch igniters for lab-scale testing of hybrid rocket motors. A side-by-side comparison on the same igniter system between Hydrogen and Methane as the igniter fuel was done to investigate which, if any, fuel can exhibit better transient and/or steady state performance. Due to the higher heat of combustion, adiabatic flame temperatures and theoretical characteristic exhaust velocities when reacting with Oxygen, Hydrogen was found to have more reliable and repeatable ignition transients. The solid fuel regression rates were also found to be higher when using Hydrogen despite competition to burn with Oxygen between Hydrogen and the solid Nylon-6 fuel. These performance benefits come at the cost of being less volumetrically efficient than Methane as Hydrogen has a significantly smaller density at a given temperature and pressure.

Nanostructured materials offer tremendous opportunities for engineering advanced device components for diagnostic and therapeutic applications. One such material, nanoporous gold (np-Au), has found use in applications ranging from catalysis to biosensing, where pore morphology plays a critical role in performance. Np-Au is typically produced by a process known as dealloying, where immersion in nitric acid selectively removes silver from a gold-silver alloy and gold surface atoms diffuse at the metal-electrolyte interface arranging into a bicontinuous ligament network. While morphology evolution of bulk np-Au has been widely studied, knowledge about its thin film form, which is influenced by the underlying substrate, is limited. This thesis delves into the mechanical behavior of nanoporous gold (np-Au) thin films on substrates of varying mechanical compliance, focusing on the role of substrate stiffness controlled by the thickness of polydimethylsiloxane (PDMS) layers anchored onto a rigid glass slide. Using a finite element analysis (FEA) framework, the study simulates the deformation and strain energy characteristics of np-Au films, revealing a nuanced interplay between substrate compliance and film morphology. Simulation results indicate that the effective elastic modulus of PDMS, modulated by its thickness, critically affects the deformation patterns in np-Au thin films. At the film-substrate interface, simulations show that the np-Au/PDMS system undergoes significantly greater deformation than np-Au/glass, characterized by both in-plane compressive and out-of-plane vertical displacements. The study further presents a detailed analysis of strain energies, with the simulations uncovering that the total strain energy of the film-PDMS system decreases as PDMS thickness increases. Corresponding experiments performed in our group show that the decrease in strain energy is associated with the diminished presence of macroscopic cracks in the np-Au films on thicker PDMS

With the increase in agriculture prices, reduced farm labor supply, and a higher population, fruit production must increase in the future. Shake-catch harvesting is a method where a tree’s trunk is shaken, and the fruits fall and drop onto catching surfaces. Existing designs cause excessive fruit damage and hence are used only for processing fruits or nuts. This work focuses on designing, building, and testing an apparatus for catching fruits in free fall without causing damage. First, several design variants were considered, and one design was selected. Next, a small-scale system was designed using CAD and built. Fruit-dropping on this system was simulated in ANSYS to predict fruit impact characteristics. Also, the simulation was calibrated by dropping an artificial instrumented fruit and measuring the impact characteristics. Finally, real fruit drop experiments were performed using cling peaches to assess the system’s capability to collect fruit without causing damage. The calibrated simulation will be used in future work to explore more design alternatives, guide material selection, and perform system optimization.

Passive two-phase fluid cooling systems are of major interest for cooling electronics in terrestrial and micro gravity environments due to their compactness and minimization of moving parts. In this thesis, the use of asymmetry for bubble ebullition and growth on a heated surface to passively generate lateral motion of fluid within an open-ended channel is discussed. The asymmetry is achieved by locating reentrant slot cavities on one face of a mm-scale 30/60-degree ratchet. Two such ratcheted walls with cavities in every third ratchet form the vertical walls of an open-ended channel. The ratcheted walls are heated using a serpentine thick-film metallic heater. The open-ended channel is located within a quiescent pool of a dielectric fluid. Visualization studies show that bubbles and slugs tend to move in a preferential direction within the open channel. This direction corresponds to the 30-degree slope face of the ratchet, in which the reentrant cavity is located. Prior studies have alluded to two potential mechanisms for this preferential lateral motion- (1) bubble pump model developed by Kapsenberg et al. [14], which attributes the lateral motion to the momentum imparted by the growing bubble to the surrounding liquid, and (2) asymmetry in the curvature of the slug that spans several ratchet lengths, resulting in a net surface tension force along the 30-degree slope of the ratchet. In order to assess the importance of the bubble pump model, bubble ebullition and growth from the nucleation sites for different heat fluxes and subcooling temperatures are captured using high speed videos and are analyzed using custom image processing of high-speed videos. The major purpose of the image processing is to detect the bubbles in the frames and obtain height and diameter of the bubbles attached to the ratchet in each frame. Active contouring and segmentation techniques are used to detect bubbles in the frames. The velocity imparted by the growing bubble on the ratchet to t

Without a precedent to laundering clothes off-Earth, a preliminary solution is required to develop a spaceflight laundry machine capable of operating in various gravity fields. With this thesis’ proposed solution, human exercise to power an agitating bladder, a closed-loop hydraulic system, and a wastewater sensor suite provide a desirable environment for quantifying waste-mass transfer away from textiles while minimizing textile damage. Bond Graph Theory is used to model the proposed solution and to evaluate how human-power and valve configurations affect the system’s cleaning performance. Bond Graph simulation results reveal preliminary performance metrics and hardware significantly impacting the machine’s performance. A human-powered laundry machine prototype and model are essential for maturing the technology to spaceflight readiness.