In this thesis we present numerical simulation studies of fluid-immersed granular systems using models of varying scales and complexities. These techniques are used to examine the effects of an interstitial fluid on the dynamics of dense granular beds within a number of vibrated systems. After an introduction to the field of granular materials, we present the techniques used to model both the granular dynamics and the fluid flow. We introduce various multiscale techniques to couple the motion of the granular and fluid phases. An extensive comparison between these techniques is conducted for some well-known systems. The fluid-grain coupling techniques are applied to some larger systems in order to determine under what situations the approaches are most suitable. An investigation concerning three-dimensional fluid-driven convection within vertically vibrated fluid-immersed granular beds is then presented. Here we observe granular piling and determine that this is a result of fluid-driven convective cycles within the bed which may be strengthened through the presence of wall friction. Our simulations capture this convective behaviour and lead to a detailed understanding of the mechanisms behind the phenomenon. Under a wide range of conditions a system of fluid-immersed fine grains within a vibrated partitioned cell will transfer in their entirety into just one of the segments through a linking channel at the cell base. We perform an experimental and numerical study in order to understand the principle mechanisms behind the “partition instability”. We determine that the instability arises due to the fluid experiencing less resistance to its motion when flowing through the shallower granular column during vibration. A simple analytical model is developed which captures this behaviour. It is commonly known that large dense intruders may rise rapidly to the surface of a granular bed when subjected to a vertical vibrational force. We next present an experimental and numerical study to determine the principle mechanism associated when the granular bed is immersed in a fluid, the fluid-enhanced Brazil nut effect. Our key finding is that the behaviour of the intruder is sensitive to the detailed fluid and particle flow in its vicinity. An analytical approach is developed to model the rising of a dense intruder in a vibrating fluid-immersed porous bed. Finally a brief study is presented into the behaviour of a vibrated system of fluid-immersed particles held within a zero-gravity environment. We conduct simulations which are able to reproduce the behaviour of a collection of particles suspended magnetically in a vibrating fluid.

Skeleton is one of the three Olympic sporting disciplines to be held in the manmade bobsleigh tracks. The sport of skeleton uses a one-man sled, on which the athlete travels headfirst down a mile long track reaching speeds of up to 147 km/h. As with many sports the engineering of the equipment is playing a greater role in the overall performance of the athlete. Although the sled alone cannot win medals a poor choice of equipment can be the difference between winning and losing. The primary focus of this research is on the trajectory and response of the sled frame and how these relate to athlete perception during a descent and overall performance. Sleds were instrumented with accelerometers and strain gauges that enabled the mechanical behaviour of the sled to be determined quantitatively. Qualitative data comprised of athlete training logs (mainly from the author), provided information about the feel and perception of the run. Tests were made on whole tracks, dedicated push-tracks and in the laboratory. In addition this PhD has touched on aerodynamics and runner-ice interaction. The thesis is split into three main sections: (1) The initial push phase of a descent was investigated at the Torino Sliding Centre and Calgary Olympic Park with a sled instrumented with an accelerometer. Using a single axis in the forwards direction of the sled determined the sensitivity of the measuring and acquisition device along with the capabilities and quality of information gained. Through analysis it is possible to identify the dynamics that occur during a push start and how to interpret them in order to improve athlete performance during the push start. (2) A whole descent at the Koenigssee International Race Track was measured using a three axis accelerometer. The dynamics at specific track locations were examined in detail and linked with athlete perception. Comparison of multiple descents enables the sled trajectory to be quantified to determine the overall success of the resultant trajectory. This analysis shows there is scope for maximizing athletic performance in conjunction with quantitative instrumentation of the equipment. (3) Complete descents at the Lake Placid Olympic Park were made on a sled instrumented with rosettes of strain gauges. The strain gauges were calibrated in the laboratory. Analysis of strain gauge data from the track showed the extent of deformation of the frame upon entering and exiting curves and while under the g-forces experienced, again this data is compared with athlete perception. Consideration is briefly given as to how these dynamic measurements can be used to evaluate current and future frame designs.

It is hoped that the research here outlined will give an additional understanding of the performance of "valves" under dynamic conditions and supplement existing steady state or continuous flow analysis as outlined by Wambsganss, MacLaren etc. The study describes tests carried out on disc valves in which the valve seat was withdrawn from the valve while a pressure difference existed across the valve. Simultaneous measurements were made of the force on the valve, the pressure in the plenum chamber and the displacement of the seat from the valve. Dynamic force measurements are compared with values of force measured during steady continuous flow conditions (static flow) at selected values of pressure difference and displacement of the valve from its seat. The comparison may, therefore, be considered as relating the force on the valve during dynamic withdrawal of the seat from the valve to the steady state force on the valve at corresponding pressures and displacements during steady continuous flow through the valve. It is shown that during the early part of the withdrawal, there are significant differences between the force on the valve and the steady state force. These differences are accentuated by the pressure difference across the valve and the rate at which the valve is opened. This study also deals at some length with the instrumentation used and problems encountered. From the work by Chan on the behaviour of inviscid incompressible fluids, a computer program has been developed for the steady continuous flow condition of the disc valves under study. This program is based on two-dimensional or axisymmetric potential fluid flow and uses the Finite Element method. The method employs the velocity potential Ø as the primary unknown and 8-node quadrilateral elements of arbitrary shape to represent the region of flow under study. This method is equally applicable to both confined and free surface flow problems. The method first computes a solution for the velocity potential throughout the entire flow domain and then calculates secondary unknowns, e.g. velocity, pressure and force distributions. For free surface flow problems, it also predicts the free surface location, and the contraction or discharge coefficient. Quantitative comparisons between this approach and experimental work previously outlined are also made and the quality of comparison is found to be good.

No description available.

Approved for public release, distribution unlimited / The flow patterns of two oil mist nozzles used in rotor blade excitation experiments were flow mapped using a traversing Laser Doppler Velocimeter (LDV) system to determine the velocity and the overall characteristics were recorded photographically. The nozzles were operated in a vacuum test chamber and measurements were obtained at three different spray pressures, at three different axial distances from the nozzle exit. For a 4 gallon per hour (gph) "mini-mist" nozzle, a 'referenced velocity' was defined which was found to be constant within a hollow cone, and the cone geometry and oil flow rate changed linearly with the oil supply pressure. A 6 gph "standard" nozzle gave a solid cone, but only gave a pattern free of liquid streaks at low pressures. Oil temperature affected this behavior. The analytic quantification of the spray pattern can be used to design specific blade excitation experiments in high cycle fatigue (HCF) vacuum spin

In electronic packaging, the reliability of solders is a critical issue, since serve as both electrical and mechanical connections. The most common failures arise from the thermo-mechanical fatigue (TMF) of solders, due to mismatches in the coefficient of thermal expansion between the Si-chip and the printed circuit board. In order to meet the demands of miniaturization and enhanced performance in severe environments, a novel adaptive Tin-Silver-Copper (SnAgCu) solder reinforced with NiTi shape-memory alloy (particles or fiber) developed. An experimental apparatus has been designed to investigate the thermo-mechanical straincontrolled fatigue life of the solder during both single and multiple thermal cycling under double-shear loading. For comparison, thermo-mechanical single shear tests were also performed in monolithic Tin- Silver-Copper solder and in solder reinforced with Cu fiber. Also, micro-structural evaluation of the solders during the 5th cycle was possible using Scanning and Optical microcopy together with EDS analysis.

Approved for public release; distribution is unlimited / The Cellular Automata (CA) method is based on the idea that the macroscopic behavior of a system can be captured by using simple local rules running at a microscopic level. In other words, a system can be modeled by means of simple local rules that govern the behavior of the whole system. In this thesis a local CA rule set is introduced and a methodology is developed to model physical systems that are governed by one and two dimensional wave equations. One dimensional systems are also successfully modeled by using CA and FEM techniques working as coupled, whereas two dimensional systems could only be modeled in an error margin due to the variation of the introduced time scaling factor when external forces are involved. Also, the applicability of the CA method to fracture mechanics problems is investigated. / Outstanding Thesis

All welding processes can give rise to defects, which weakens the joint and can eventually lead to the failure of the welded structure. In order to inspect welds for detects, without affecting the usability of the product, non-destructive testing (NDT) is needed. NDT includes a wide range of different techniques, based on different physical principles, each with its advantages and disadvantages. The testing is often performed manually by a skilled operator and in many cases only as spot-checks. Today the trend in industry is to move towards thinner material, in order to save weight for cost and for environmental reasons. The need for inspection of a larger portion of welds therefore increases and there is an increasing demand for fully automated inspection, including both the mechanised testing and the automatic analysis of the result. Compared to manual inspection, an automated solution has advantages when it comes to speed, cost and reliability. A comparison of several NDT methods was therefore first performed in order to determine which methods have most potential for automated weld inspection. Automated analysis of NDT data poses several difficulties compared to manual data evaluation. It is often possible for an operator to detect defects even in noisy data, through experience and knowledge about the part being tested. Automatic analysis algorithms on the other hand suffer greatly from both random noise as well as indications that originate from geometrical variations. The solution to this problem is not always obvious. Some NDT techniques might not be suitable for automated inspection and will have to be replaced by other, better adapted methods. One such method that has been developed during this work is thermography for the detection of surface cracks. This technique offers several advantages, in terms of automation, compared to existing methods. Some techniques on the other hand cannot be easily replaced. Here the focus is instead to prepare the data for automated analysis, using various pre-processing algorithms, in order to reduce noise and remove indications from sources other than defects. One such method is ultrasonic testing, which has a good ability for detecting internal defects but suffers from noisy signals with low spatial resolution. Work was here done in order to separate indications from corners from other indications. This can also help to improve positioning of the data and thereby classification of defects. The problem of low resolution was handled by using a deconvolution algorithm in order to reduce the effect of the spread of the beam.The next step in an automated analysis system is to go beyond just detection and start characterising defects. Using knowledge of the physical principles behind the NDT method in question and how the properties of a defect affect the measurement, it is sometimes possible to develop methods for determining properties such as the size and shape of a defect. This kind of characterisation of a defect is often difficult to do in the raw data, and is therefore an area where automated analysis can go beyond what is possible for an operator during manual inspection. This was shown for flash thermography, where an analysis method was developed that could determine the size, shape and depth of a defect. Similarly for laser ultrasound, a method was developed for determining the size of a defect. / <p>Godkänd; 2014; 20140415 (mike); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Patrik Broberg Ämne: Experimentell mekanik/Experimental Mechanics Avhandling: Imaging and Analysis Methods for Automated Weld Inspection Opponent: Professor Tadeusz Stepinski, Signaler och system, Institutionen för teknikvetenskaper, Uppsala universitet, Ordförande: Professor Mikael Sjödahl, Avd för strömningslära och experimentell mekanik, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Fredag den 13 juni 2014, kl 10.00 Plats: E243, Luleå tekniska universitet</p>

Why copy the best athletes? When you finally learn their technique, they may have already moved on. Using muscluloskeletal biomechanics you might be able to add the "know-why" so that you can lead, instead of being left in the swells. This dissertation presents the theoretical framework of musculoskeletal modeling using inverse dynamics with static optimization. It explores some of the possibilities and limitations of musculoskeletal biomechanics in cross-country skiing, especially double-poling. The basic path of the implementation is shown and discussed, e.g. the issue of muscle model choice. From that discussion it is concluded that muscle contraction dynamics is needed to estimate individual muscle function in double-poling. Several computer simulation models, using The Anybody Modeling System™, have been created to study different cross-country skiing applications. One of the applied studies showed that the musculoskeletal system is not a collection of discrete uncoupled parts because kinematic differences in the lower leg region caused kinetic differences in the other end of the body. An implication of the results is that the kinematics and kinetics of the whole body probably are important when studying skill and performance in sports. Another one of the applied studies showed how leg utilisation may affect skiing efficiency and performance in double-poling ergometry. Skiing efficiency was defined as skiing work divided by metabolic muscle work, performance was defined as forward impulse. A higher utilization of the lower-body increased the performance, but decreased the skiing efficiency. The results display the potential of musculoskeletal biomechanics for skiing efficiency estimations. The subject of muscle decomposition is also studied. It is shown both analytically and with numerical simulations that muscle force estimates may be affected by muscle decomposition depending on the muscle recruitment criteria. Moreover, it is shown that proper choices of force normalization factors may overcome this issue. Such factors are presented for two types of muscle recruitment criteria. To sum up, there are still much to do regarding both the theoretical aspects as well as the practical implementations before predictions on one individual skier can be made with any certainty. But hopefully, this disseration somewhat furthers the fundamental mechanistic understanding of cross-country skiing, and shows that musculoskeletal biomechanics will be a useful complement to existing experimental methods in sports biomechanics. / Varför ska man kopiera de som är bäst inom sin idrottsgren? När man väl har lärt sig deras teknik så har de antagligen redan gått vidare. Vore det inte bättre att öka sin förståelse så att man kan ligga i framkant, istället för i svallvågorna? Med biomekaniska simuleringar som ett komplement till traditionella experimentella metoder finns möjligheten att få veta varför prestationen ökar, inte bara hur man ska göra för att öka sin prestation. Längdskidåkning innehåller snabba och kraftfulla helkroppsrörelser och därför behövs en beräkningsmetod som kan hantera helkroppsmodeller med många muskler. Avhandlingen presenterar flera muskeloskelettära simuleringsmodeller skapade i The AnyBody Modeling System™ och är baserade på inversdynamik och statisk optimering. Denna metod tillåter helkroppsmodeller med hundratals muskler och stelkroppssegment av de flesta kroppsdelarna. Avhandlingen visar att biomekaniska simuleringar kan användas som komplement till mer traditionella experimentella metoder vid biomekaniska studier av längdskidåkning. Exempelvis går det att förutsäga muskelaktiviteten för en viss rörelse och belastning på kroppen. Detta nyttjas för att studera verkningsgrad och prestation inom dubbelstakning. Utifrån experiment skapas olika simuleringsmodeller. Dessa modeller beskriver olika varianter (eller stilar) av dubbelstakning, alltifrån klassisk stil med relativt raka ben och kraftig fällning av överkroppen till en mer modern stil där åkaren går upp på tå och använder sig av en kraftig knäböj. Resultaten visar först och främst att ur verkningsgradsynpunkt är den klassiska stilen att föredra då den ger mest framåtdrivande arbete per utfört kroppsarbete, dvs den är energisnål. Men ska en längdlöpare komma så fort fram som möjligt (utan att bry sig om energiåtgång) verkar det som en mer modern stil är att föredra. Denna studie visar också att för att kunna jämföra kroppens energiåtgång för skelettmusklernas arbete mellan olika rörelser så krävs det en modell där muskler ingår. Andra studier som presenteras är hur muskelantagonister kan hittas, hur lastfördelningen mellan muskler eller muskelgrupper förändras när rörelsen förändras samt effekter av benproteser på energiåtgång. Några aspekter av metoden presenteras också. Två muskelmodeller och dess inverkan på olika simuleringsresultat visas. En annan aspekt är hur muskeldekomposition och muskelrekryteringskriterium påverkar beräkningarna. Normaliseringsfaktorer för olika muskelrekryteringskriterium presenteras. / Beräkningsbaserad biomekanik inom längdskidåkningen - möjligheter och begränsningar

This dissertation concerns structural topology optimization in conceptual design stages. The objective of the project has been to identify and solve problems that prevent structural topology optimization from being used in a broader sense in the avionic industry; therefore the main focus has been on stress and fatigue constraints and robustness with respect to load uncertainties. The thesis consists of two parts. The first part gives an introduction to topology optimization, describes the new contributions developed within this project and motivates why these are important. The second part includes five papers. The first paper deals with stress constraints and a clustered approach is presented where stress constraints are applied to stress clusters, instead of being defined for each point of the structure. Different approaches for how to create and update the clusters, such that sufficiently accurate representations of the local stresses are obtained at a reasonable computational cost, are developed and evaluated. High-cycle fatigue constraints are developed in the second paper, where loads described by a variable-amplitude load spectrum and material data from fatigue tests are used to determine a limit stress, for which below fatigue failure is not expected. A clustered approach is then used to constrain the tensile principal stresses below this limit. The third paper introduces load uncertainties and stiffness optimization considering the worst possible loading is then formulated as a semi-definite programming problem, which is solved very efficiently. The load is due to acceleration of point masses attached to the structure and the mass of the structure itself, and the uncertainty concerns the direction of the acceleration. The fourth paper introduces an extension to the formulated semi-definite programming problem such that both fixed and uncertain loads can be optimized for simultaneously. Game theory is used in the fifth paper to formulate a general framework, allowing essentially any differentiable objective and constraint functions, for topology optimization under load uncertainty. Two players, one controlling the structure and one the loads, are in conflict such that a solution to the game, a Nash equilibrium, is a design optimized for the worst possible load.