<p>Several fatigue criteria were evaluated with experimental fatigue test data. The fatigue tests contained many different geometries with different degrees of stress concentration. It was concluded that the differences between the criteria were neglectable when compared to the differences between the specimens. The stress concentrations with the stress gradients and sizes of the highly stresses volumes that resulted were very important. In order to understand this, gradient and volume methods were investigated. The gradient methods showed some improvement over the strictly local evaluation first attempted. The volume method, a weakest link application with a Weibull distribution of the fatigue strength, yielded results useable for actual design situations. The volume method is strongly recommended and the choice of criterion does not seem to be very important.</p>

<p>This licentiate thesis is generally concerned with the ductile failure and rupture mechanisms encountered under combined tension and torsion loading. In the first part entitled Paper A, an experimental investigation of the rupture mechanisms in a mid-strength and a high strength steel was conducted employing a novel test configuration. The specimen used was a double notched tube specimen loaded in combined tension and torsion at a fixed ratio. The effective plastic strain, the stress triaxiality and the Lode parameter was determined in the centre of the notch at failure. Scanning electron microscopy of the fractured surfaces revealed two distinctively different ductile rupture mechanisms depending on the stress state. At high stress triaxiality the fractured surfaces were covered with large and deep dimples, suggesting that growth and internal necking of voids being the governing rupture mechanism. At low triaxiality it was found that the fractured surfaces were covered with elongated small shear dimples, suggesting internal void shearing being the governing rupture mechanism. In the fractured surfaces of the high-strength steel, regions with quasi-cleavage were also observed. The transition from the internal necking mechanism to the internal shearing mechanism was accompanied by a significant drop in ductility.</p><p>In the second part entitled Paper B, a micromechanics model based on the theoretical framework of plastic localization into a band introduced by Rice is developed. The model employed consists of a planar band with a square array of equally sized cells, with a spherical void located in the centre of each cell. The periodic arrangement of the cells allows the study of a single unit cell for which fully periodic boundary conditions are applied. The micromechanics model is applied to analyze failure by ductile rupture in experiments on double notched tube specimens subjected to combined tension and torsion carried out by the present authors. The stress state is characterized in terms of the stress triaxiality and the Lode parameter. Two rupture mechanisms can be identified, void coalescence by internal necking at high triaxiality and void coalescence by internal shearing at low triaxiality. For the internal necking mechanism, failure is assumed to occur when the deformation localizes into a planar band and is closely associated with extensive void growth. For the internal shearing mechanism, a simple criterion based on the attainment of a critical value of shear deformation is utilized. The two failure criteria capture the transition between the two rupture mechanisms successfully and are in good agreement with the experimental result.</p>

<p>This thesis deals with physiological and mechanical properties of fast and slow twitch mouse muscles. It discusses isometric, concentric and eccentric contractions of mouse <i>extensor digitorum longus</i> ('EDL') and <i>soleus</i> ('SOL') muscles. This project primarily investigated the behaviors of muscles, to give better understanding and improved descriptions for the human system, when subjected to impact or sustained high loading conditions.</p><p>Muscle force has been shown to be length and activation dependent. The effect of passive or active length changes on muscle force production was studied. Isometric activation showed a maximal force at optimum length for each individual muscle, to which all experiments were related. This optimum length was stimulation frequency dependent and maximum produced force shifted towards shorter length with increasing frequency.</p><p>Active shortening of maximally stimulated muscle was shown to produce reduced force, but also a reduced isometric force (force depression) following shortening, regardless of the shortening conditions and the method of muscle stimulation.</p><p>Steady state force depression (Δ<i>F</i>_stdep) was correlated with the instant force depression Δ<i>F</i>_idep, pre-activation time, t0-t1 and the work (WS), performed by the muscle during shortening. It was positively correlated with the Δ<i>F</i>_idep when the shortening magnitude was varied ('VSM'). But in varying the shortening velocity ('VST'), it was negatively correlated with the instant force depression.</p><p>In active stretch, force was analogously enhanced during stretch, and this effect remained after stretch. Steady state force enhancement (Δ<i>F</i>_stenh)following muscle stretch was correlated with the instant force enhancement,Δ<i>F</i>_ienh, pre-activation time, t0-t1 and the work (WL), done on the muscle during stretch. It was positively correlated with Δ<i>F</i>_ienh when the stretch magnitude was varied ('VLM'). But in varying the stretch velocity ('VLT'), Δ<i>F</i>_stenh was negatively correlated with Δ<i>F</i>_ienh.</p><p>Furthermore, the rise time constant, (<i>Tr)</i> of redeveloped isometric forces following the</p><p>shortening and the fall time constant, (<i>Tf)</i> of the relaxed isometric force following muscle stretch were calculated. In VSM, <i>Tr</i> and<i> F</i>_stdep were positively correlated with each other, while in VST, they were negatively correlated. <i>Tf</i> and <i>F</i>_stenhwere negatively correlated in both VLM and VLT.</p>

<p>This report is a first practical study of micro valves for hydraulics, manufactured by Microstaq Inc. who uses, for hydraulics, new materials and new actuating technologies. The purpose is to evaluate if, in the future, there is any possibility of complementing or exchanging the classical use of electro magnetic solenoids in electro hydraulic applications with this new technology. The valves studied are of MEMS-type (Micro Electro Mechanical Systems), which are etched out of silicon and has an electro thermic actuation. During the study it showed that this new valve technology had some teething troubles. The valves had proplems managing high pressure drops, both regarding strength of materials and performance. If you let the manufacturers further develop this technology there are great potentials for using this in future hydraulic systems.</p>

Detta examensarbete utreder en ny typ av spjällhus som optimerats för dragracing. Spjällhuset styr luftflödet till förbränningsmotorn och regleras av gashandtaget. Konceptet är utvecklat av Emtes Ingenjörsbyrå och i examensarbetet ingår att konstruera ett spjällhus med det nya konceptet för motorcykelmodellen Suzuki Hayabusa. Det standardmonterade spjällhuset är anpassat för gatubruk och ett brett effektregister. För dragracing är den maximala effekten avgörande och det standard monterade spjällhuset är en flaskhals vid WOT (Wide Open Throttle). För konceptet saknas dock fullständiga lösningar för diverse funktioner. I examensarbetet ingår att komplettera konceptet med en returmekanism, synkroniseringsanordning och erforderliga standarkomponenter. I början av arbetet skall även en kravspecifikation och DFMEA (Design Failure Mode Effects Analysis) upprättas. Den slutliga konstruktionen uppfyller de uppsatta kraven enligt krav-specifikationen. Spjällhuset är kompakt, enkelt att montera och anpassat för tillverkning i små serier. Den symmetriska konstruktionen förenklar CNC-tillverkningen (Computer Numerical Control) och sänker tillverknings-kostnaderna. Avslutningsvis genomfördes provning för att jämföra det nya spjällhuset med det standardmonterade. Metoden visades vara olämplig och provningen av spjällhuset blev resultatlös. Vidare provning av spjällhuset med andra metoder rekommenderas men lämnas utanför examensarbetet på grund av tids¬begräsningarna. / In this undergraduate thesis a throttle body designed for drag racing is investigated and evaluated. The throttle body governs the air flow to the internal combustion engine and is controlled by the throttle twist grip. The concept is developed by Emtes Engineering and within this undergraduate thesis it includes to design a throttle body with the concept for the motorcycle Suzuki Hayabusa. The standard mounted throttle body is suitable for normal usage and a wide power range. For drag racing the maximum power output is crucial and the standard mounted throttle body is a bottle-neck at WOT (Wide Open Throttle). Complete solutions for various functions are missing for the concept. This undergraduate thesis includes completing the concept with a returning mechanism, synchronisation arrangement and proper standard components. At the beginning of the task it also includes to establish a specification of requirements and DFMEA (Design Failure Mode Effects Analysis). The final design fulfils the specification of requirements. The throttle body is compact, simple to assemble and suited for small scale manufacturing. The symmetrical design simplifies the CNC-manufacturing (Computer Numerical Control) and thereby reduces the costs. Finally a test was carried out to compare the new throttle body with the standard mounted. The methodology turned out to be unsuitable and the testing of the throttle body was without results. Further testing with other methods is recommended but that will not be a part of this undergraduate thesis.

Detta examensarbete på C-nivå behandlar design av en snöskoter. Uppdragsgivaren är företaget SnoWolverine som vill utveckla en snöskoter med tre drivband varav två placerade i fronten. Den omfattande informationsinsamling som har skett under arbetets gång har visat att en trebandad skoter, som har utmärkt framkomlighet, har en stor marknad. De lösningar som finns på marknaden, främst fyrhjuling med bandsats, har alla kompromisser. Produktutvecklingsverktyg som funktionsanalys och QFD har använts i processen. Stort fokus har legat på utveckling av formspråket för snöskoter och utvecklingen av smarta funktioner som efterfrågas av målgruppen. Resultatet är en kraftfull snöskoter med ett kompakt utseende. Främre boggin är gjord så utrymmessparande som möjligt och designad för att vara robust. Unika funktioner är bland annat en vindtunnel som fungerar som vindruta, frontbåge med vinschfäste, utfällbar sadel och förvaringslösningar.

This report is a first practical study of micro valves for hydraulics, manufactured by Microstaq Inc. who uses, for hydraulics, new materials and new actuating technologies. The purpose is to evaluate if, in the future, there is any possibility of complementing or exchanging the classical use of electro magnetic solenoids in electro hydraulic applications with this new technology. The valves studied are of MEMS-type (Micro Electro Mechanical Systems), which are etched out of silicon and has an electro thermic actuation. During the study it showed that this new valve technology had some teething troubles. The valves had proplems managing high pressure drops, both regarding strength of materials and performance. If you let the manufacturers further develop this technology there are great potentials for using this in future hydraulic systems.

Examensarbetet är utfört i samarbete med företaget Mil Tech i Västerås. Arbetet har gått ut på att konvertera en redan existerande turbojetmotor med dragkraft på 110 Newton till en turboaxelmotor där effekten tas ut via en axel. Konverteringen av turbojetmotorn till en turboaxelmotor sker genom att konstruera en modul bestående av ett friturbinsteg som fästes på turbojetmotorn. Arbetets fokus har legat på att få en lättillverkad och enkel moduluppbyggt friturbinsteg som med få medel kan fästas direkt på turbojetmotorns utloppsdel utan att behöva modifiera turbojetmotorn. Det moduluppbyggda friturbinsteget innehåller alla de mekaniska detaljer som gör en konvertering från turbojetdrift till turboaxeldrift möjlig. Arbetet har inletts med att ta fram termodynamiska beräkningar för att avgöra motorns prestanda och motorns fysikaliska krav på design, konstruktion, material och hållfasthet. Examensarbetet innehåller solidmodeller samt konstruktionsritningar som gör det möjligt att utifrån detta bygga en fungerande friturbinmodul.

No description available.

This thesis concerns a mechatronic system, designed and developed for the forest industry, to trace logs from forest to sawmill. The research is a key part of a large research project launched by the EU in 2006 called the Indisputable Key project. Wood waste during harvesting, transportation and refinement is a major concern for the wood industry worldwide. Some raw materials are not suited for specific end products, and acknowledging this late in the wood value chain is cost inefficient. Pinpointing specific raw material suitable for a particular end product could increase quality, reduce waste and environmental impact; to accomplish this, traceability is essential. To trace the raw material of a final wood product to its origin, marking and reading of the different specimens must occur at each refining stage in the wood value chain. The traceability chain can be divided into three main stages: forest to sawmill, inside the sawmill, and from sawmill to second manufacturer. The research presented here covers the first part of the wood value chain, namely, forest to sawmill. In Scandinavian countries, logs are cut to length in the forest using a harvester machine. To trace logs, a unique identity code needs to be associated with each log at harvesting time in the forest and detected before further processing at the sawmill. Earlier research using RFID transponders as code carriers have been functionally verified but too costly. Although the cost of RFID transponders is declining, alternative methods are considered a necessity. This constitutes the main driver behind this thesis. The thesis presents a promising alternative log marking method comprising a harvester saw-integrated log code printer and a sawmill code detection system. An identity code in the form of a standard matrix code is applied via the harvester saw bar during cutting. A prototype has been designed and realized and the results point towards a both time and cost efficient solution. The code detection system, to be placed in one or more locations at the sawmill, is based on vision technology and image processing to detect the applied log codes. Both log code marking and reading systems communicate with an ICT system which maintains the traceability database. A major advantage of the system is that both marking and reading is performed without any time-loss and hence do not disturb the high pace production flow in todays forestry. Also, the item cost of each code mark is very low, compared to e.g.a transponder. The marking technology is patent pending. A field test was performed in December 2009 in northern Sweden. A test batch of 320 logs was marked and read. Two code structures (i.e., matrix and barcode) were applied, where 210 barcoded logs were used to demonstrate log traceability between forest and sawmill. This result indicates that this technology has potential. The prototype is not intended for commercial use, but serves merely to demonstrate the potential of the method; further research is needed to improve its functionality. / QC 20110512