The competition in the car market in the world is continuously intensifying. To gain an advantage in the market while making a profit, each car manufacturer needs a strong focus on always improving in the technology development. It is not just technology of the cars that need development, but it is equally important to improve the manufacturing processes itself. In the end, this will result in more appealing products for the customer at a competitive cost. The aim and scope of this master thesis is to get a deeper understanding of the forces in the stamping die during sheet metal forming in manufacturing. By using strain gauges and microcontrollers, the forces during the entire forming process could be measured and analyzed. The relationship between the force on the pressure pins in the die and the length of the pressure pins was also investigated by adding shims on the pressure pins. A modular system using Arduino Uno with 3D-printed parts was developed to measure the forces in the blank holder during sheet metal forming. An Arduino software system and TeraTerm was found the most appropriate for collecting and organizing data from the strain gauge sensors and microcontrollers. Tests were then conducted using different settings of the press, and these showed that the forces in the blank holder were uneven. Adding shims to the pins so that they were all of equal length evened out the forces in the blank holder. Another test showed that adding more shims to only one of the pins increased the force in that pin, and that adding 0.5mm of shims to that pin more than doubled the maximum force. The system developed in this thesis can measure the forces in the blank holder during the sheet forming process at a lower speed of production. This system can also detect different force settings in the press. Lastly, it can also detect a difference in force for different pressure pin lengths. / Konkurrensen på bilmarknaden i världen intensifieras kontinuerligt. För att få en fördel påmarknaden samtidigt som de gör vinst måste varje biltillverkare ha ett starkt fokus på att alltid förbättrateknikutvecklingen. Det är inte bara bilens teknik som behöver utvecklas, utan det är lika viktigt attförbättra tillverkningsprocesserna i sig. I slutändan kommer detta att resultera i mer attraktiva produkterför kunden till ett konkurrenskraftigt pris. Syftet och omfattningen av detta examensarbete är att få en djupare förståelse av krafterna ipressverktyget under plåtformningprocessen. Genom att använda töjningsgivare och mikrokontrollerkunde krafterna under hela formningsprocessen mätas och analyseras. Förhållandet mellan kraften påmothållarpinnarna i verktyget och längden på pinnarna undersöktes också genom att lägga till shims påpinnarna. Ett modulsystem som använde Arduino Uno med 3D-printade delar utvecklades för att mätakrafterna i formen under formningsprocessen. Ett Arduino-mjukvarusystem och TeraTerm bedömdesvara det mest lämpliga för att samla in och organisera data från töjningssensorer och mikrokontroller. Tester genomfördes sedan med olika inställningar i pressen, och dessa visade att krafterna ipressverktyget var ojämna. Genom att lägga till shims på pinnarna så att de alla var lika långa utjämnadeskrafterna i pressverktyget. Ett annat test visade att genom att lägga till fler shims på endast en avmothållarpinnarna ökade kraften i pinnen. Genom att tillägg till 0,5 mm shims på den pinnen mer änfördubblade den maximala kraften. Systemet som utvecklats i denna rapport kan mäta krafterna i pressverktygets mothållarpinnarunder formningsprocessen vid en lägre produktionshastighet. Detta system kan också upptäcka olikakraftinställningar i pressen. Slutligen kan den också upptäcka skillnader i kraft vid olika längder påmothållarpinnarna.

Vid träning av baksida lår kan det vara svårt att förstå hur muskeln aktiveras. Genom att visualisera de myoelektriska signalerna från biceps femoris och semimembranosus till den som tränar kan personen få en bättre mind-muscle connection. I examensarbetet har två teoretiska EMG sensorer skapats och simulerats, kod har skrivits för att filtrera fyra EMG signaler samt överföra dessa över BLE, kraftsensorer är kopplade och kod är skriven för att avgöra den kraftutveckling som sker i en kontraktion av baksida lår. EMG sensorerna har jämförts med SparkFuns MyoWear muskelsensor, OpenBCI Cyton board och BioNomadix BN-EMG2-T. Båda de teoretiska lösningarna anses likvärdiga med ett billigare alternativ till Cryton Board, en flerkanalig lösning till MyoWear, BN-EMG2-T är för dyr att realistiskt implementeras till examensarbetets syfte. Simuleringarna visar att kretsarna behandlar signalen enligt tänkt sätt men det gick inte att bygga en prototyp då en pandemi har begränsat KTH:s verksamhet / One difficulty when training hamstrings is the understanding of how the muscle is activated. Through visualization of the myoelectrical signals from biceps femoris and semimembranosus to the exerciser, a better mind-muscle connection can be achieved. In this bachelor thesis, two theoretical EMG sensors were created and simulated, code to filter four EMG signals and transmit them through BLE was written, also a way to calculate how much force is applied in a hamstring curl was constructed. Both EMG sensors have been compared against SparkFuns MyoWear muscle sensor, OpenBCI Cyton Board and BioNOmadix BN-EMG2-T. The theoretical EMG sensors are interconvertible to a cheaper Cyton Board, a multichannel alternative to MyoWear, the BN-EMG2-T is too expensive to be a realistic alternative for this bachelor thesis attended purpose. Simulations show that the EMG sensors behave as intended but because of a pandemic, a prototype could not be created.

Additive manufacturing (AM) also commonly known as 3D-printing is a manufacturing method which creates parts from adding layer into another. In the field of printed electronics Inkjet printing (IJP) and Aerosol Jet printing (AJP) are the most common AM techniques. IJP and AJP are non-contact-based printing techniques where ink is deposited on a surface with droplets. AJP aerosolizes the ink into a mist which is deposited on a surface according to the predetermined pattern. IJP instead produces singular droplets when printing. These printing methods have been used for manufacturing various printed electronics such as strain gauges which has been the focus of this project.  The purpose of this thesis was to investigate the feasibility of printing strain gauges. Through a literature study the overall function and use for strain gauges and various printing methods were investigated, as well as previous studies related to printed strain gauges using AJP and IJP. To further investigate one of these techniques, strain gauges were printed using Inkjet printing. The sensors were printed using two different inks, one containing silver particles and the other containing constantan particles. The strain gauges were also printed on various substrates such as Polyimide (PI) and Polyetheretherketone (PEEK), to determine the best material combination. The silver strain gauges were then sintered in an oven while the constantan sensors were sintered using photonic sintering. To evaluate each ink-substrate combination several tests was performed throughout the printing and sintering process. A tape test was used to determine adhesion, SEM analysis was performed to study the effect of the sintering process and the resistance was measured to calculate the conductivity and study the printability on different substrates. To characterise the printed strain gauges a bending test was performed where the change in resistance was measured with changing strain. The output was also studied over time to determine the stability of the printed sensors.  The silver ink showed overall better properties compared to the constantan ink, which could be due to that the silver ink has been more developed than the constantan ink. The resistivity of the silver ink was calculated to 7.0E-07 Ωm and the constantan ink to 2.23E-05 Ωm. The average gauge factor for the silver ink printed on PI was calculated to GFavg~1.6 at low strain and GFavg~2.1 at high strain, the silver samples printed on PEEK was GFavg~2.4 at low strain and GFavg~2.3 at higher strain, and the constantan samples was determined to GFavg~2.7 during loading at low strain and GFavg~17 at high strain due to deformation. Some of the samples printed with silver ink showed quite linear behaviour while the samples printed with constantan deformed when applying high stress. The silver samples printed on PEEK showed more hysteresis compared to the silver samples printed on PI, but the PEEK samples showed a better stability over time compared to PI.  The thesis shows that it is possible to manufacture strain gauges, but the result depends a lot on the ink and substrate material chosen. Silver inks has been developed over a long period and thus making it easier to handle and the result is better compared to newer inks such as constantan.

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No description available.

A pressão intracraniana (PIC) é um dos principais parâmetros neurológicos em animais e humanos. A PIC é uma função da relação entre o conteúdo da caixa craniana (parênquima cerebral, líquido cefalorraquiano e sangue) e o volume do crânio. O aumento da PIC (hipertensão intracraniana) pode acarretar graves efeitos fisiológicos ou até mesmo o óbito em pacientes que não receberem rapidamente os devidos cuidados, os quais incluem o monitoramento em tempo real da PIC. Todos os métodos de monitoramento da PIC atualmente utilizados são invasivos, ou seja, é necessário introduzir um sensor de pressão no sistema nervoso central, acarretando aos pacientes riscos de infecções e traumas decorrentes do método. Neste trabalho desenvolvemos um método minimamente invasivo de monitoramento da pressão intracraniana, que consiste na utilização de sensores de deformação do tipo strain gauge fixados sobre a calota craniana. Os sinais oriundos deste sensor foram amplificados, filtrados e enviados para um computador com software apropriado para análise e armazenamento dos dados. O trabalho aqui apresentado objetivou os testes "in vivo" do sistema, onde foi utilizada mais de uma centena de animais em diversos testes, sendo que em todos os casos os resultados foram satisfatórios, apontando a eficácia do método. / The intracranial pressure (ICP) is one of the most important neurological parameter in animals and humans. The ICP is a function of the relation between the contents of the skull (brain parenchyma, cerebrospinal fluid and blood) and the volume of the skull. The increase in ICP (intracranial hypertension) may cause serious physiological effects and death in patients that do not receive appropriate care quickly, which includes real-time monitoring of ICP. All monitoring methods currently used in ICP are invasive, ie requiring invasion of the central nervous system by a pressure sensor, causing infections and traumas risks to patients. In this work we present a new minimally invasive method to monitor the intracranial pressure. This uses strain gauge deformation sensors, externally glued on the skull. The signal from this sensor is amplified, filtered and sent to a computer with appropriate software for analysis and data storage. "In vitro" and "in vivo" experiments let to the following results: (1) Our minimally invasive system is capable of adequately monitoring the ICP. (2) The measurements are in real and online time providing excellent signal and stability. (3) Simultaneous comparison with invasive methods not only validated our results but showed increased performance. The equipment cost effective will allow the use of our system in the Public Health System, with a important social aspect of our contribution.

The search for new solutions for the generation of energy is becoming more and more important for our future. Big arguments and disagreements on e.g. the questions of gas transport or the dependence on energy supplied by other countries raise demands on the development of new forms of alternative energy resources. Wave power is one of the main sources of renewable energy due to the high power density stored in ocean waves. Nevertheless, the dynamic forces of waves are so large that serious questions popped up on how to design a system which could work even in an unfavourable wave climate or could at least retain working capabilities after big storms without significant damages. This thesis studies the reliability of the mechanical parts of a linear direct driven permanent magnet generator. The results of offshore experiment where strain gauge sensors instrumented on the capsule and the inner framework structure are presented. Stress estimation analyses using strain gauges are carried out. A method for measuring forces and moments in the mechanical structure of the WEC is developed. Evaluation of the lateral force acting on the outer structure is a key factor for the design and construction of the WEC. A method for the measurement of the lateral force acting on the capsule has been developed. A study of the inclination angle between the Wave Energy Converter and the floating buoy has been carried out. The aim of this work is to contribute to the development of wave energy conversion system, and especially to the estimation of structural loads which are important for the survivability of the system under hard sea states. This work is a step that may influence future design of wave energy devices in terms of material aspect, survivability in a hard wave climate and cost-effective renewable energies.

This thesis explores experimentally and theoretically two different aspects of the properties and behaviour of metals: their ability to damp noise and their susceptibility to crack when solidifying. The first part concerns intrinsic material damping, and is motivated by increased demands from society for reductions in noise emissions. It is a material’s inherent ability to reduce its vibration level, and hence noise emission, and transform its kinetic energy into a temperature increase. To design new materials with increased intrinsic material damping, we need to be able to measure it. In this thesis, different methods for measurement of the intrinsic damping have been considered: one using Fourier analysis has been experimentally evaluated, and another using a specimen in uniaxial tension to measure the phase-lag between stress and strain has been improved. Finally, after discarding these methods, a new method has been developed. The new method measures the damping properties during compression using differential calorimetry. A specimen is subjected to a cyclic uniaxial stress to give a prescribed energy input. The difference in temperature between a specimen under stress and a non-stressed reference sample is measured. The experiments are performed in an insulated vacuum container to reduce convective losses. The rate of temperature change, together with the energy input, is used as a measure of the intrinsic material damping in the specimen. The results show a difference in intrinsic material damping, and the way in which it is influenced by the internal structure is discussed. The second part of the thesis examines hot cracks in solidifying shells. Most metals have a brittle region starting in the two-phase temperature range during solidification and for some alloys this region extends as far as hundreds of degrees below the solidus temperature. To calculate the risk of hot cracking, one needs, besides knowledge of the solidifying material’s ability to withstand stress, knowledge of the casting process to be able to calculate the thermal history of the solidification, and from this calculate the stress. In this work, experimental methods to measure and evaluate the energy transfer from the solidifying melt have been developed. The evaluated data has been used as a boundary condition to numerically calculate the solidification process and the evolving stress in the solidifying shell. A solidification model has been implemented using a fixed-domain methodology in a commercial finite element code, Comsol Multiphysics. A new solidification model using an arbitrary Lagrange Eulerian (ALE) formulation has also been implemented to solve the solidification problem for pure metals. This new model explicitly tracks the movement of the liquid/solid interface and is much more effective than the first model. / QC 20100929

There is no established method of measuring load accurately in a threaded connection at working temperatures exceeding 500°C. At these conditions conventional methods can not be used due to the sensitivity of the instruments and it is suggested that a non contact method should be used. The laser strain gauge was developed by the Loughborough University Optical Research Group and it is a non contact way of measuring surface strain. With the help of finite element analysis (FEA) a special nut was developed that can be used to measure the load on the connection by relating the surface strain of the nut to the load. Experimental work later revealed that due to the threads sticking in the connection there is hysteresis present between the load and surface strain relationship. To eliminate the hysteresis a new part was added to the connection which could be used to relate the surface strain on it to the load without any hysteresis. This new part was a specially designed washer with three grooves to allow easy access for the user to measure the surface strain using the laser strain gauge. Part of the design specification was that the load has to be determined to an accuracy of 0.5%. Using sensitivity analysis the washer was analysed in terms of how manufacturing imperfections affect the accuracy of the load measuring device. The results revealed that to achieve the required 0.5% accuracy the washer would have to be manufactured to very tight tolerances. To achieve these tight tolerances the manufacturing process would not be cost effective so it was proposed that individual calibration is required for each load measuring washer. Tests showed that with sufficient calibration the specially designed washer and the laser strain gauge can be combined and used as an accurate non contact load measuring device. As it is a non contact method it can be used in extreme environments including high temperatures. This thesis describes how background research, finite element analysis and experimental testing were used to develop the load measuring washer. Also it is shown, how in-depth sensitivity analysis was used to determine the accuracy of the prototype and that how manufacturing imperfections influence the working life of a threaded connection.

Le diagnostic de l'occlusion dentaire reste actuellement un défi majeur pour les chirurgiens-dentistes. Des outils dédiés existent, comme le papier à articuler et le T-Scan®, mais sont limités pour diverses raisons. L'objectif de cette thèse est alors de développer un nouvel outil sous forme de matrice de capteurs de pression sur substrat flexible alliant les avantages des outils nommés précédemment, à savoir un produit électronique, informatisé et de faible épaisseur pour ne pas être intrusif. Nous avons choisi une technologie piézorésistive et l'utilisation de jauges de contrainte en silicium microcristallin. Ce matériau est déposé à basse température (< 200°C) directement sur substrat Kapton® par PECVD (Plasma Enhanced Chemical Vapor Deposition) dans une perspective de faible coût. Ces jauges ont d'abord été caractérisées mécaniquement et électriquement lors de tests de courbure. Les facteurs de jauge longitudinaux et transversaux du silicium microcristallin ont été étudiés afin de maîtriser son comportement sous déformation. Les dispositifs restent fonctionnels jusqu'à des contraintes de 0,6 %, à partir de laquelle des dégradations apparaissent. Ces valeurs de contraintes permettent d'atteindre des rayons de courbure de l'ordre du millimètre pour des substrats de 25 µm d'épaisseur. Deux types de matrices ont ensuite été développées : une première de 800 jauges pour l'étude de la surface occlusale d'une dent puis une seconde de 6400 jauges pour l'étude d'une moitié de mâchoire. Dans les deux cas, des corrélations intéressantes entre le papier à articuler et nos réponses électriques ont été observées lors de caractérisations en conditions « semi-réelles » à l'aide d'un articulateur dentaire. Ces deux prototypes ont ainsi permis une preuve de concept fonctionnelle de l'objectif visé en utilisant des jauges en silicium microcristallin. / Dental occlusion diagnosis is still a major challenge for dentists. A couple of tools are dedicated to occlusal analysis, such as articulating papers and the T-Scan® system, but they are limited for various reasons. That's why, the goal of this thesis is to develop a novel system consisting in pressure sensor arrays on flexible substrates combining the positive aspects of both previously cited tools: an electronic and computerized system, on a very thin non-invasive flexible substrate. We chose a piezoresistive technology based on microcrystalline silicon strain gauges and 25-µm- or 50-µm-thick Kapton® substrates. Microcrystalline silicon is deposited directly on plastic at low temperature (< 200°C) using PECVD technique (Plasma Enhanced Chemical Vapor Deposition) in a cost-effective solution perspective. Strain gauges have firstly been characterized using bending tests. Longitudinal and transversal gauge factors have been studied in order to understand the behavior of our deposited materials under bending. Those gauges remained functional until strains up to 0.6 % and degradations appeared for higher values. These values correspond to bending radius on the order of 1 mm for 25-µm-thick substrates. Then, those gauges have been integrated in arrays with two different designs: one was an 800-element array to study the occlusal surface of one tooth, and the second was a 6400-element array to study the occlusal surface of a hemiarcade. Those prototypes have showed interesting correlations between articulating paper marks and our electrical responses during characterizations using a dental articulator to simulate a human jaw. Thus, we have developed in this work a proof-of-concept of a flexible strain sensor using microcrystalline silicon dedicated to dental occlusion diagnosis.