In 1952 Alan Turing published his paper "The Chemical Basis of Morphogenesis", which described a model for how naturally occurring patterns, such as the stripes of a zebra and the spots of a leopard, can arise from a spatially homogeneous steady state through diffusion. Turing suggested that the concentration of the substances producing the patterns is determined by the reaction kinetics, how the substances interact, and diffusion.  In this project Turing's model with linear reactions kinetics was studied. The model was first solved using two different numerical methods; the finite difference method (FDM) and the finite element method (FEM) with different boundary conditions. A parameter study was then conducted, investigating the effect on the patterns of changing the parameters of the model. Lastly the controllability of the model and the least energy control was considered. The simulations were found to produce patterns provided the right parameters, as expected. From the investigation of the parameters it could be concluded that the size/tightness of the pattern and similarity of the substance concentration distributions depended on the choice of parameters. As for the controllability, a desired final state could be produced thorough simulations using control of the boundary and the energy cost of producing the pattern increased when decreasing the number of controls.

Detta examensarbete är på grundnivå som har genomförts under en period av 20 veckor undervåren 2023 och motsvarar 15 högskolepoäng. Projektet har haft som syfte att utveckla ett konceptför en kontaktor och tillämpa additiv tillverkningsteknik som en tillverkningsmetod för konceptet.Uppdragsgivaren för projektet har varit ABB Control Products i Västerås och de har identifieratbehovet av en lämplig lösning för limproblemet i släckpaketet för kontaktorer av storlek nio. Dennuvarande användningen av lim i kontaktorerna ansågs vara ohälsosam och uppfyllde intemiljökraven. Inom ramen för projektet genomfördes en konceptutveckling för att lösa det identifieradeproblemet. Dessutom undersöktes möjligheten att tillämpa additiv tillverkningsteknik ochgenomföra en förenklad kostnadsbedömning för att visa skillnaden i kostnad mellan den nuvarandetillverkningsmetoden och additiv tillverkningsteknik. Produktutvecklingsmetoder användes för attgenomföra projektet, vilket resulterade i ett fungerande teoretiskt koncept. För att sålla ut idéeroch koncept användes en prioriteringsmatris och ett poängsystem. Det resulterande konceptetrepresenteras av CAD-modeller som består av metallplåtar och två delar av det utveckladekonceptet. Konceptet möjliggör en ny design utan användning av lim vid montering. Det har ocksåvisat sig att det är möjligt att ändra tillverkningsmetoden genom att använda additivatillverkningstekniker. Även om prototyperna ännu inte har testats, anses de teoretiska lösningarnavara fungerande.

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Fused deposition modeling (FDM) is gaining an ever increasing attention for its ability to fabricate complex geometry parts and prototypes at lower cost. The technology is striving to produce parts with high mechanical resistance that can withstand and perform under high stress environment. The adhesion strength between layers, transverse strength, is a limiting factor that need to be quantitatively evaluated to further understand and improve the bonding behavior of thermoplastic polymer in FDM. This interfacial adhesion is derived by the diffusion and penetration of polymer chains across the interface allowing the chain entanglement to form a bonding medium. This study investigates the bonding behaviour of polylactic acid (PLA) as a function of chain branching. The adhesion strength is quantitatively evaluated by developing and performing a peel test of a two-printed layer samples. It is possible to increase chain branching of PLA by bulk modification with epoxy chain extender. The modification of PLA was carried out using an internal batch mixer with four different concentrations of chain extender. The modified PLA was processed into print filament and characterized by parallel plate rheometry and DSC. It was found that the addition of chain extender increased molecular weight and degree of branching of PLA and in return the peel testing results reflected a significant increase in adhesion strength. Such improvement can be attributed to the long branched chains of PLA and its ability to create entanglements between layers. These findings can help in producing better PLA filaments to provide a higher stress resistance for FDM fabricated functional parts. / Thesis / Master of Applied Science (MASc) / Fused Deposition Modeling (FDM) is a recent popular method of plastic 3D printing technique, in which plastic filament is heated to a molten state to be then deposited through a layer-by-layer fashion to successfully fabricate parts. One of the drawbacks of that technology is the low bonding strength developed between layers as compared to strength along the length direction of layers. This study focuses on developing a testing methodology to evaluate the adhesion strength between layers and altering the material structure to maximize such strength. Four types of polylactic acid with different degrees of chain branching were successfully processed, printed and tested. Material with higher degree of branching yielded higher adhesion strength.

Distributed temperature and strain sensing is demanded for a wide range of applications including real-time monitoring of industrial processes, health monitoring of civil infrastructures, etc. Optical fiber distributed sensors have attracted tremendous research interests in the past decade to meet the requirements of such applications. This research presents a multiplexed sensor array for distributed temperature and strain sensing that can multiplex a large number of UV-induced sensors along a single fiber. The objective of this research is to develop a quasi-distributed sensing technology that will greatly increase the multiplexing capacity of a sensor network and can measure temperature and strain with a high accuracy and high resolution. UV-induced intrinsic Fabry-Perot interferometric (IFPI) optical fiber sensors, which have low reflectance and low power loss, are good candidates for multiplexed sensors networks. Partial reflectors are constructed by irradiating photosensitive fiber with a UV laser beam. A pair of reflectors will form a Fabry-Perot interferometer that can be used for temperature and strain sensing. A sensor fabrication system based on a pulsed excimer laser and a shadow mask is developed. A spectrum-based measurement system is presented to measure the interference fringes of IFPI sensors. A swept coherent light source is used as the light source. The spectral responses of the IFPI sensors at different wavelengths are measured. A frequency division multiplexing (FDM) scheme is proposed. Multiple sensors with different optical path differences (OPD) have different sub-carrier frequencies in the measured spectrum of the IFPI sensors. The multiplexing capacity of the sensor system and the crosstalk between sensors are analyzed. Frequency estimation based digital signal processing algorithms are developed to determine the absolute OPDs of the IFPI sensors. Digital filters are used to select individual frequency components and filter out the noise. The frequency and phase of the filtered signal are estimated by means of peak finding and phase linear regression methods. The performance of the signal processing algorithms is analyzed. Experimental results for temperature and strain measurement are demonstrated. The discrimination of the temperature and strain cross sensitivity is investigated. Experimental results show that UV-induced IFPI sensors in a FDM scheme have good measurement accuracy for temperature and strain sensing and potentially have a large multiplexing capacity. / Ph. D.

A one-dimensional model of a heterogeneous material consisting of a matrix with embedded separated particles is considered, and the melting or solidification of the particles is investigated. The matrix is in imperfect contact with the particles, and the lumped capacity approximation applies to each individual particle. Heat is generated inside the particles or is transferred from the matrix to the particles coupled through a contact conductance. The matrix is not allowed to change phase and energy is either generated inside the matrix or transferred from the boundaries, which is initially conducted through the matrix material. The physical model of this coupled, two-step heat transfer process is solved using the energy method. The investigation is conducted in several phases using a building block approach. First, a lumped capacity system during phase transition is studied, then a one-dimensional homogeneous material during phase change is investigated, and finally the one-dimensional heterogeneous material is analyzed. A numerical solution based on the finite difference method is used to solve the model equations. This method allows for any kind of boundary conditions, any combination of material properties, particle sizes and contact conductance. In addition, computer programs, using Mathematica, are developed for the lumped capacity system, homogeneous material, and heterogeneous material. Results show the effects of control volume thickness, time step, contact conductance, material properties, internal sources, and external sources. / Master of Science

Rapid prototyping systems have advanced significantly with respect to material capabilities, fabrication speed, and surface quality. However, build jobs are still manually activated one at a time. The result is non-productive machine time whenever an operator is not at hand to make a job changeover. A low-cost auxiliary system, named Continuous Layered Manufacturing (CLM), has been developed to automatically load and unload the FDM 1600 rapid prototyping system (Stratasys, Inc.). The modifications made to the FDM 1600 system are minimal. The door to the FDM 1600 build chamber is removed, and the .SML build files that are used to drive the FDM 1600 are modified at both ends to facilitate synchronized operation between the two systems. The CLM system is capable of running three consecutive build jobs without operator intervention. As long as an operator removes finished build jobs, and adds new build trays before at most every three build jobs, the FDM can operate near indefinitely. The impact of the CLM system on the productivity of the FDM 1600 rapid prototyping system is demonstrated by the expected reduction from the customary eight weeks down to a future three and one-half weeks required to complete the typical forty build jobs during a semester in the course ME 4644 Introduction to Rapid Prototyping at Virginia Tech. / Master of Science

Syftet med rapporten är att redovisa en studie där val av utskrivningsmetod samt passande material inom additiv tillverkning ska motiveras, för att tillverka kalibreringsformar till Bucher Emhart glass glasmaskiner. Målet med studien är att tillverka kalibreringsformarna som väger mindre än stålformarna som används idag i glasmaskinerna, detta för att minska arbetsbelastningen på personalen. Stålformarna väger ca 9kg i dagsläget. För att utesluta material och utskriftmetoder användes i första steget kravspecifikationen, och sedan användes pughs matris för att väga de material och utskrivningsmetoder som klarar kraven som ställs. För att validera materialen gjordes även en FEM analys samt en analytisk beräkning på spänningarna. Utifrån Pughs matrisen kunde det konstateras att med den data som givits att en FDM skrivare med ASA som material är mest lämpat för detta projekt. Med denna 3D-skrivare och tillhörande material fick en formhalva en vikt på ca 700g, vilket minskar avsevärt vikten som måste lyftas och således minskar arbetsbelastningen hos arbetarna.