Wrap-up 2022


The Department of Mechanical and Industrial Engineering and its research unit, UNIDEMI, are pleased to announce that in 2022, that the following students have completed their Doctoral Programs:

Rui Manuel Ferreira Dias, Doctorate in Industrial Engineering, with the thesis: “Theory of Constraints: a Continuous Improvement methodology as a basis for the development, deployment and implementation of the Strategy” 

Abstract: Strategy, strategic planning and strategy deployment are words that managers deal with every day. Despite the knowledge and importance of these concepts, many organizations find it difficult to correctly apply them in a simple and agile way so that they can add value and boost growth. Well-developed, correctly deployed and better implemented strategies can be the differentiating factor, allowing us to win in increasingly innovative, more competitive and more demanding markets. This research work proposes the BHTLS model for strategy planning, deployment and implementation. BHTLS integrates strategic planning methodologies (Balanced Scorecard, Hoshin Kanri) used in addition to the first for development, systematization and monitoring of strategy in the long term (3 to 5 years) and the second for its deployment by teams in the short term, focusing on annually on the vital objectives, your action plans and goals to be achieved. The model also integrates continuous improvement methodologies (Theory of Constraints, Lean and Six-Sigma) with the aim of helping the organization to implement and incorporate into day-to-day activities the actions necessary for the implementation, implementation and standardization of actions. arising from the strategy. Over 3 cycles of research – action, research methodology used in the work, the model evolved from a TLS model of continuous improvement, to the final model – BHTLS that integrates strategic planning with continuous improvement. The BHTLS model developed and implemented made it possible to carry out the organization’s strategic planning, identify its vital objectives, design the action plans necessary to achieve them and implement them with the help of the TLS continuous improvement methodology. 

Elsa Maria Isqueiro Batista, Doctorate in Mechanical Engineering, with the thesis: “Innovative contributions on calibration methodologies towards reliable microflow measurements

Abstract: Flow measurement is critical in healthcare, chemistry and pharmaceutics, to mention a few. In fact, there are several applications in the microflow and nanoflow range, such as scaled-down process technology, drug development, and special health-care applications, as organ-on-a- chip technology. Nevertheless, the majority of the instruments used for the specified applica- tions are not sufficiently studied regarding their flow accuracy and traceability. Hence these fluid applications at the micro and nanoscale still lack well defined calibration methodologies for the devices working at the mentioned flow range with adequate uncertainty values. The work presented in this thesis focuses on the development and improvement of in- novative applications of calibration methodologies for microflow measuring instruments. The gravimetric method already implemented at IPQ from 120 mL/h to 2000 mL/h was used and improved for low flow rates down to 10 mL/h. Additionally, other 4 methods were developed to enable the calibration of micro/nano flows in a non-intrusive way. They are interferometry, pending drop, front track and comparison method (where a calibrated flow generator is used as the reference standard). The methodology that is best suited for each specific instrument and each measurement range, with the lowest uncertainty, was successfully identified along with the relevant influence factors in microflow measurements. A specific objective of this work was to increase the measuring range of IPQ-LVC down to 5 nL/min (0.3 mL/h) with a 3% target uncertainty (k=2). This objective was possible to achieve and even surpass with the use of the interferometric method, where measurements were per- formed down to 1.6 nL/min (0.1 mL/h) with 2 % uncertainty(k=2). This method was internally validated by comparison with the gravimetric method and is now in the process of external validation by EURAMET project 1508. 

João Pedro Alves Pássaro, Doctorate in Mechanical Engineering, with the thesis: “Numerical Development and Optimization of Thermal Storage Systems by Phase Change 

Abstract: The building sector accounts for a large portion of energy consumption and carbon dioxide emissions in Europe reducing buildings energy footprint can bring significant decreases in energy consumption. In this specific case, reducing the energetic footprint in residential buildings is a step in the right direction. One way of achieving this is using renewable en- ergies, however these have unreliable production windows, often with a mismatch between production and demand. Using the technical solutions presented here, this mismatch is bridged storing energy whenever it is available to use it when need, even when not available, thermally storing the energy. It was studied the behaviour of Phase Change Materials (PMCs) in heat exchanging and thermal energy storage applications using Computational Fluid Dynamic (CFD) tools. The work presented here successfully developed several tech- nical solutions of heat exchangers for different thermal storage systems components and applications using PCMs, specifically the heat exchangers that would allow for the maxi- mum benefit to use from the PCMs properties in order to heat, cool and provide domestic hot water (DHW) by means of a geothermal heat pump coupled with PCM enhanced bore- holes . The heat exchangers developed are to be employed in the domestic storage tanks applications and in the geothermal boreholes, thus storing renewable energy from solar and geothermal sources for domestic use. Additionally, developing heat exchangers that allow either macro or microscopic encapsulation usage of PCM to help maintain the underground soil average temperature in order to benefit from geothermal heat pump efficiency. It was concluded from these applications that a good methodology was achieved that allows for thermal storage system based on PCMs to be used in residential dwellings either already existing and retrofitted or designed specifically for new residences and successfully decrease their overall energy consumption and carbon footprint.   

Inês de Abreu Ferreira, Doctorate in Industrial Engineering, with the thesis: “Waste to 3D Printing: the development of additive symbiotic networks 

Abstract: Industry 4.0 technologies, such as additive manufacturing (AM) and blockchain technology, may drive the implementation of a new generation of circular economy strategies. However, the role of these new technologies in designing and implementing circular economy ecosystems is not a trivial issue. In this sense, this PhD research work intends to foster knowledge for developing industrial symbiosis networks within the AM industry – the so-called additive symbiotic networks. A systematic literature review reveals current circular economy relationships within the AM industry and highlights the potential of this industry to create and develop additive symbiotic networks in which plastic wastes from other industries may be used as material inputs for AM processes. However, given the digital nature of AM and considering challenges related to trust or implementing transactions, there is a need to find tools that enable additive symbiotic networks. Blockchain technology may be an enabler of such symbiotic networks, and its adoption within these settings may have implications for the supply chain of the additive symbiotic networks. Using an abductive research approach, two case studies are conducted concerning two additive symbiotic networks comprising companies that use AM processes to valorize plastic waste streams. Case study A proves there is space within the context of additive symbiotic networks to explore the adoption of blockchain technology and identifies a set of requirements that support the technology adoption in that specific network context. From this point, case study B is developed in order to understand the consequent implications of adopting such disruptive technology as blockchain in the supply chain structure of an additive symbiotic network. Results suggest that with the adoption of blockchain there is a reduction in the number of intermediary stakeholders involved in the network and an adaption of the value flows within the network. By offering a tool that helps to deal with the challenges associated with the additive symbiotic networks, exploring its adoption and some of its implications in the supply chain of those networks, this PhD thesis promotes the development of the additive symbiotic networks, contributing to the efficient use of natural resources, promoting the collaboration between industries and reducing waste streams to achieve more sustainable production. 

Tiago Miguel André Rodrigues, Doctorate in Mechanical Engineering, with the thesis:Improvement and tailoring of parts fabricated with Wire and Arc Additive Manufacturing 

Abstract: Wire and arc additive manufacturing (WAAM) is an Additive Manufacturing (AM) process that finds applications in different industrial sectors. It shows to be competitive compared to other AM technologies, mainly due to its low implementation costs, high deposition rates, and the ability to produce medium to large complex parts. Improvement of parts’ properties has been the primary goal of the scientific community and was also the main objective of this work, where significant scientific and technological developments were implemented. Different approaches were tested: i) by performing heat treatments; ii) by adding grain refiners to the molten metal; iii) by fabricating Functionally Graded Materials (FGM); iv) by developing a new process variant called Ultra cold Wire and Arc Additive Manufacturing (UC-WAAM). To fulfill these objectives, laboratory means were developed. Including the development of a multi-wire gas tungsten arc welding (GTAW) torch for creating components with a functional gradient, two prototypes to introduce ceramic particles in the molten pool, and a customized gas metal arc welding (GMAW) torch. The feasibility of using ceramic particles to refine the grain structure of WAAM parts was experimentally demonstrated on a High Strength Low Alloy (HSLA) steel and Inconel 625. Parts characterization was performed with multi-phenomena techniques: optical and scanning electron microscopy assisted by energy dispersive spectroscopy and electron backscatter diffraction, synchrotron X-ray diffraction, and mechanical testing. Despite the potential applications of FGM, one of the main limitations is related to significant stresses, chemical incompatibilities, and the possible formation of undesirable intermetallics. In this work, manufacturing of different FGM was successfully produced without defects by applying different building strategies. The results showed that a direct-type interface resulted in superior mechanical properties without intermetallics and smaller residual stresses than a smooth transition build-type. The development of UC-WAAM lowered the average temperatures experienced by the material and increased the cooling rates during parts fabrication compared to traditional GMAW. An overhang structure was fabricated, highlighting the potential for UC-WAAM to be used for this type of structures. 

Fábio Rúben Monteiro Conde, Doctorate in Mechanical Engineering, with the thesis:Multiscale optimization of non-conventional composite structures for improved mechanical response 

Abstract: Nowadays, due to governmental requirements to control climate change, there is a great inter- est on the part of the automotive and aerospace industry to design structures as light as possible, without jeopardize their performance, thus increasing their efficiency. Multi-material design is a way to achieve this goal, as will be shown in this work In this work, multi-material design is considered with the goal of improving the structure’s stiffness, strength, and non-linear behaviour when it yields. Firstly, a microstructural topology optimization is carried out seeking for multi-material microstructures with increased stiffness and strength compared to equivalent single-material microstructures. Afterwards, this study is further extended to perform multi-scale topology optimization, where a concurrent optimization of ma- terial and structure is done. Ultimately, the non-linear behaviour of hybrid fibre reinforced com- posites is optimized in order to introduce a so-called “pseudo-ductility”. Two different optimization problems are formulated and solved here. One compliance mini- mization with mass constraint problem and another stress-based problem where the maximal von Mises stress is locally minimized in the unit-cell. The multi-material design is investigated here using two different approaches. On one hand, the two solids coexist being bonded together across sharp interfaces. On the other hand, a functionally graded material is obtained as an extensive smooth variation of material properties on account of varying composition’s volume fractions of both solids throughout the design domain. The compliance-based optimization results show that multi-material microstructures can be stiffer compared to single-material ones for the same mass requirement. Regarding the stress-based problem, lower stress peaks are obtained in bi-material design solutions and, specially, in the case of graded material solutions. As regards multi-scale topology optimization, the results show that a multi-material structure can be stiffer than its single-material counterpart, which is in accordance with the microstructural study performed earlier. Hybrid composites can achieve the so-called “pseudo-ductile” behaviour mimicking the well- known elastic-plastic behaviour. To understand under what circumstances such behaviour is ob- tained, optimization problems are formulated and solved here. Two different types of optimiza- tion problems are considered. Firstly, one finds out the optimal properties of fibres to hybridize and get the pseudo-ductile behaviour. Once an optimal hybridization is found, another optimiza- tion problem is solved in order to understand the influence of the fibre dispersion on the composite response. The optimal results obtained show hybrid composites having a considerable pseudo- ductile behaviour. 

Jiajia Shen, Doctorate in Mechanical Engineering, with the thesis:Welding of High Entropy Alloys 

Abstract: High entropy alloys are novel engineering materials which possess extraordinary properties. Current weldability studies regarding this novel class of materials are scarce. Hence, the present work addresses this shortcoming by focusing on the use of arc-based welding processes for joining of single phase equiatomic CoCrFeMnNi (Co-Cr-Fe-Mn-Ni system), a dual phase non-equiatomic eutectic AlCoCrFeNi2.1 (Al-Co-Cr-Fe-Ni system) and a metastable Fe42Mn28Co10Cr15Si5 (Fe-Mn-Co-Cr-Si system) high entropy alloys. For the single phase CoCrFeMnNi, gas metal arc welding using 308 and 410 stainless steel fillers are used. Multiscale correlative microstructure characterization encompassing electron microscopy coupled with mechanical property analysis, alongside thermodynamic calculations, is used to address the effect of the weld thermal cycle across the joint. Overall, this material possesses excellent weldability, with the joints possessing good mechanical behavior. The first successful welding of a non-equiatomic eutectic AlCoCrFeNi2.1 is obtained using gas tungsten arc welding. Again, multiscale characterization enabled to determine the role of the weld thermal cycle across the welded joint. The volume fraction of the dual-phase structure, as well as those of the strengthening nanoscale precipitates was seen to be correlated to the distance to the heat source. The as-welded material possessed a combination of good strength and ductility, showcasing the good weldability of this material. Finally, gas tungsten arc welding of a metastable Fe42Mn28Co10Cr15Si5 was also successfully performed. Electron microscopy, aided by high energy synchrotron X-ray diffraction, were combined with thermodynamic calculation to understand how the existing phases varied across the welded joint. Similarly, to the other welded joints, the metastable alloy was also seen to present good weldability, with the observed mechanical behavior of the joints enabling its use for structural applications in different industries. The results obtained in this work show that arc-based welding processes are viable for welding of these novel materials and the resulting properties enable to consider the obtained joints for structural-oriented applications. 

Diogo Jorge de Oliveira Andrade Pereira, Doctorate in Mechanical Engineering, with the thesis:Developments in Magnetic Pulse Welding 

Abstract: Magnetic Pulse Welding is a solid state joining technology based on impact, which allows to produce overlap joints both in planar and tubular geometries. The technology has seen an increased interest in recent years, especially as a result of the industrial need to joint dissimilar materials (metallic and non-metallic) which easily form brittle intermetallic phases when welded by fusion-based processes. However, no significant improvements on existing equipments have been reported, which are normally sized for endurance, compromising the machine efficiency. In fact these are normally equipped with large storage capacitors banks, which are sometimes insufficient for dissimilar material combinations that require more energy to weld In this study existing equipments were analysed to understand the key components aiming at its optimization. A prototype machine was developed and assembled envisaging higher discharge energies efficiency. The equipment was tested and validated in tubular transitions due to the facility to produce the coils in laboratory facilities but also due to the industrial applications identified. This joining process is known to need a conductive flyer material to allow inducing current for the magnetic interaction which projects the flyer against the target to produce a weld. Thus, tube to tube and tube to rod welds were produced in AA6063 in similar and dissimilar metallic joints to Ti6A4V. AA7075 to carbon fibre reinforced polymer tubes transitions were also successfully produced especially when Cu or Ni ductile interlayers were used. The developed prototype equipment was compared to a commercial machine to identify the optimization achieved and to compare characteristics of the welds produced. For this, the joints were characterized both structural and mechanically. The prototype machine proved to have a higher efficiency needing less than 15% of the energy required on the commercial machine to produce similar aluminium transitions (reducing from 16 kJ to 2 kJ). The machine also proved to be efficient in producing dissimilar joints, such as aluminium to titanium transitions and metal to non-metal transitions. 

Valdemar Rebelo Duarte, Doctorate in Mechanical Engineering, with the thesis:Developments in Directed Energy Deposition Additive Manufacturing: In-situ Hot Forging and Indirect Cooling 

Abstract: Additive Manufacturing (AM) by Directed Energy Deposition-arc (DED-arc) is competing with other AM technologies due to its high deposition rate, ability to produce large parts with medium/high geometric complexity and low capital and running costs. However, residual stresses, coarse microstructures, and defects on parts, such as cracks and pores, may compromise in-service industrial applications and need to be overcome. This work aimed to develop and validate two innovative process variants: one based on in-situ hot forging; and the other on temperature control, that is, indirect cooling of deposited material and hot forging. The hot forging variant consisted of locally forging the deposited layer at high temperatures using low forces. The goal is to create an uniform plastic deformation zone along the layer, to promote grain refinement, reduce material anisotropy and collapse defects. The variant based on temperature control consisted of cooling the hammer components and the shielding gas used to protect the molten pool, to increase the solidification rate and thus, prevent grain coalescence. For this, dedicated DED-arc equipment was designed and manufactured with specific features for research. The effect of hot forging was analysed in detail on 316LSi stainless steel, and the feasibility of its application was verified in other relevant industrial materials. It was concluded that hot forging can induce dynamic recrystallization, increase nucleation sites and prevent epitaxial grain growth. Thus, it contributes to an overall refined and homogeneous microstructure with improved mechanical properties. The developed cooling system lowered the average temperature of the nozzle and hammer during consecutive depositions. Cooling of the shielding gas had no major effect on the cooling rates and microstructure of the materials, however, it was observed that the hot forging changes the heat flow conditions of the part, promoting higher cooling rates. 

Maximilian Zarte, Doctorate in Industrial Engineering, with the thesis:Decision Support System for Production Planning from a Sustainability Perspective”  

Abstract: Manufacturing enterprises supply our global demand for products, creating economic value. Moreover, they are also responsible for several environmental and social impacts, e.g., green-house gases, waste, and poor working conditions. These impacts cause climate change, air and sea pollution, and social inequality, which are a few examples of current challenges for global sustainability strategies. However, researchers have widely addressed these impacts and warned politicians and society about the risk of the collapse of ecosystems. Despite these warnings, manufacturing enterprises still have difficulties improving the sustainability of their production processes. Therefore, new technologies are required to support enterprises and help determine their production processes’ sustainability status by considering multiple aspects (economic, environmental, and social). Moreover, advice should be given on how the identified issues can be avoided, reduced, or compensated for future production activities. This research presents a fuzzy decision support system and an experimental study for sustainability-based production planning. For this approach, systematic literature reviews were made, analysing concept methods for sustainability-based production management and planning. The results show, among other things, that current methods for sustainability-production planning are focused on single aspects of sustainability (e.g., energy or waste planning). Therefore, a fuzzy decision support system was developed that simultaneously evaluates social, environmental, and economic aspects. The decision support system’s model identifies the most significant opportunities to improve the production program’s sustainability and gives recommendations on how to change it. The decision support system was tested and validated in an experimental study in the production planning laboratory at Emden University of Applied Sciences. The study results discuss problems, needs, and challenges affecting sustainability-based production planning. Moreover, opportunities for future research were identified based on the limitations of the experimental study.