Insects and small flyers operate at Reynolds numbers ranging from approximately 10-105 , where viscous forces are important. Due to their small size and weight, they are sensitive to small changes in the free stream during flight, such as wind gusts. First, the aerodynamics of flapping flight is briey explained. Then the lift, drag and power usage for a flapping NACA 0012 airfoil is simulated in ANSYS Fluent for different oncoming wind directions. The aim of the report is to understand how the pitching amplitude, the apping frequency and the plunging amplitude can be adjusted to compensate for oncoming wind gusts. The simulation is modelled as quasistatic since the time scale of the flapping wings of the insect is much shorter than the time scale of the wind gusts. / Insekter och andra små flygande djur flyger vid låga Reynolds tal som sträcker sig från cirka 10-100 000. Det medför att viskösa krafter är viktiga. På grund av sin ringa storlek och vikt är de känsliga för små förändringar i den friströmmen under flygningen, till exempel vindbyar. Först förklaras teorin bakom aerodynamiken vid flaxande flygning. Sedan simuleras lyftkraft, dragkraft och effektförbrukning för en flaxande NACA 0012 vingprofil vid olika riktningar på friströmmen med hjälp av ANSYS Fluent. Syftet med rapporten är att förstå hur pitching-amplitud, vingslagsfrekvens och vingslagsamplitud kan justeras för att kompensera för inkommande vindbyar. Simuleringen modelleras som kvasistatisk eftersom tidsskalan hos insekters flaxande vingar normalt är mycket kortare än tidsskalan hos vindbyar.

When investigating mechanical problems it is often more convenient to deal with scalars rather than vectors. In this project methods stemming from the field of analytical mechanics, which lets one derive the equations of motion using scalar quantities instead of vectors, have been used. Two mechanical problems were investigated, a double pendulum with a spring and particles orbit in a sphere. The equations of motion of the two systems were derived with the assistance of computer algebra, using Maple and the external package Sophia. The systems were investigated with regard to periodicity and conserved quantities. / Vid undersökning av mekaniska problem är det oftare smidigare att utgå från skalära storheter än vektorstorheter. I detta projekt har metoder från den analytiska mekaniken använts vilka låter ett systems rörelseekvationer härledas med just skalära storheter istället för vektorstorheter. Två mekaniska system har undersökts, en dubbelpendel med fjäder och en partikels banrörelse i en halvsfär. Systemens rörelseekvationer har tagits fram och lösts med hjälp av datoralgebra, i Maple med det externa programpaketet Sophia. Systemen har sedan undersökts med avseende på periodicitet och bevarade storheter.

In this project we have used the theory of analytical mechanics to derive equations of motion for complex mechanical systems in order to study their behaviour over time. Even if the theory provides powerful tools to tackle tough problems which would be very hard to solve by methods of Newtonian mechanics, you are still relatively limited without running any computer simulations. One realises that in a faster rate it will be an incredibly difficult task to find an analytical solution when the degrees of freedom increases. Even if one would succeed to derive the equations, one still has to solve them to get the information of the systems behavior. Of experience one knows that the equations in general are nonlinear and hence must be integrated numericaly. These nonlinearities preposses the sensible dependence on initial conditions which means that small perturbations from equilibrium will lead to divergent outcomes in the continuing evolution of the motion. The motion is then what you call chaotic. Since we have been dealing with nonlinear problems, numerical and symbolical analysis has been performed with the computer aid. Hence, a big part of this project has been to get familiar with the Maple based simulation program ’Sophia’, developed by the department of mechanics at KTH [7]. With this program we could simulate different kinds of pendulum systems and by plotting their solutions, investigate the influence on the overall motion by the parameter values and initial conditions. / I det här projektet har vi studerat komplexa mekaniska system där vi genom teori från den analytiska meknaiken, härlett rörelseekvationer som vi sedan har löst symboliskt. Trots att den analytiska mekaniken erbjuder kraftfulla verktyg för att bemöta svåra problem som man med Newtonsk mekanik skulle få stora svårigheter att lösa, är man ändå relativt begränsad utan datorn till hjälp. Man inser i allt snabbare takt att det blir en övermäktig uppgift att finna en analytisk lösning när antalet frihetsgrader för systemet ökar. Även om man skulle lyckas med att härleda rörelseekvationerna, vilket ofta är en krävande uppgift i sig, är allt arbete förgäves om man inte lyckas lösa dom. Av erfarenhet vet man att differentialekvationerna i allmänhet blir ickelinjära och måste därför integreras numeriskt om man inte nöjer sig med att inskränka sig till små rörelser [7]. I sådana fall kan dom ickelinjära termerna linjäriseras genom taylorserieutvecklingar och man blir då kvar med linjära ekvationer som är lösbara analytiskt. Dessa olinjäriteter påverkar systemets känslighet för initialvillkor vilket innebär att små avvikelser i begynnelsevärdena ofta leder till stora förändringar i systemets fortsatta rörelseevolution. Rörelsen blir alltså lätt vad man kallar kaotisk. Då vi har intresserat oss av systemens allmänna rörelser och inte enbart små rörelser, har symboliska och numeriska beräkningar varit gryndläggande för analysen. Stora delar av detta projekt har därför varit att bekanta oss med det Maplebaserade simuleringsprogrammet ’Sophia’, uppkallat till ära efter Sveriges första kvinnliga professor och matematiker, Sofia Kovalevskaja [7]. Med detta program kunde vi simulera olika typer av pendelrörelser och genom att rita upp grafer och animeringar, undersöka parameter-och begynnelsevärdenas inflytande på den fortsatta rörelsen.

The human neck is especially vulnerable to severe injuries why it is of interest to gain a better understanding of the injury mechanisms involved. A 3D Finite Element (FE) model including the geometry of the individual neck muscles has been developed at Kungliga Tekniska Högskolan (KTH) and gives the possibility to study the strains inside the muscles. However, in this model the muscles are only hindered to interpenetrate and can glide relative each other with a roughly estimated coefficient of friction. The focus of this thesis has been to modify the FE-model in order to model the connectivity on a physiological basis using methods available in the used FE-software. The main reason for this was to get a more realistic muscle displacement without separations that are present in the current model. The connective tissue surrounding and connecting the muscles was modeled with two principal approaches. The first was based on a combination of FE-contacts where the material properties were contacts. The other approach was based on a new element type called Smoothed Particle Hydrodynamics (SPH) elements in combination with FE-contacts. Both approaches showed that the structural stiffness did not increase significantly, but the strain levels where somewhat elevated. Stability issues arouse with deleted elements and negative element volumes causing the FE‐contact based approach to fail prematurely. The SPH‐based approach had fewest deleted elements and completed the simulation but increased the calculation time with approximately 50 %. It was concluded that the implementation of a connection between the muscles had a relatively low influence on the strains and kinematics of the neck and could be used to avoid muscle separations. The influence on stability of the model was however more evident and the most stable result increased the calculation time significantly. / Den mänskliga nacken är en väldigt sårbar del av kroppen och det är därför av stort intresse att lära sig mer om de olika skademekanismerna inblandade. På Kungliga Tekniska Högskolan (KTH) har en 3D Finita Element (FE) modell utvecklats som inkluderar musklernas geometri och ger möjlighet att studera töjningarna inuti musklerna. Men i denna modell hindras musklerna endast från penetration och kan glida relativt varandra med en grovt uppskattad friktionskoefficient. I detta examensarbete har fokus legat på att modifiera FEM‐modellen för att modellera sammanbindningen mellan musklerna på en fysiologisk basis med hjälp av tillgängliga metoder i den använda FEM‐mjukvaran. Huvudmålet med detta var att uppnå mer realistiska muskelrörelser utan separationer som uppstår i den befintliga modellen. Den bindvävnad som omger och binder samman musklerna modellerades med två grundstrategier. Den första var baserad på en kombination av FEM‐kontakter där materialegenskaperna kopplades till styvheten i FEM-kontakterna. Den andra strategin baserades på en ny elementtyp kallad Smoothed Particle Hydrodynamics (SPH) i kombination med FEM‐kontakter. Båda strategierna visade att den strukturella styvheten inte ökade med några signifikanta nivåer, men töjningsnivåerna ökade något mer. En del stabilitets problem uppstod som gav raderade element och negativa elementvolymer vilket ledde till att den FEM‐kontakt baserade strategin kraschade innan simuleringen slutförts. Den SPH‐baserade strategin resulterade i minst antal raderade element och slutförde simuleringen men ökade beräkningstiden med c.a. 50 %. Det fastställdes att implementeringen av de nya metoderna hade en relativt liten påverkan på töjningar och kinematiken hos nacken och kan användas för att undvika muskelseparationer. Inverkan på stabiliteten hos modellen var dock mer märkbart och det stabilaste resultatet ökade beräkningstiden betydligt.

The design of a paperboard testing machine, developed in order to analyse the mechanical behaviour of paperboard during the combined of out-of-plane shear and compressive loading as in the deepdrawing process, is presented. The methodology to design a paperboard testing machine is discussed and the most appropriate concepts are compared and evaluated. The design process is presented in detail, and some pilot tests are performed to give an overview about the functionality of the manufactured prototype.

Both theoretically as well as in many applications like exhaust systems, ventilation pipes, mufflers, air intakes and also large scale industrial smoke stacks, it is of interest to understand how sound waves are scattered at duct exists. Especially for aeronautical application such as jet engines, the effect of coupling of acoustics and flow on sound radiation and reflection from a duct termination in a uniform is an important problem. In order to predict the acoustic performance in duct systems, it is essential to know how the incoming acoustic waves are propagated and transmitted and reflected. This thesis work aims at developing suitable simulation methods as extension to existing software and to validate these methods to experimental measurements and theory. Firstly, numerical simulations of fully developed flow through a duct exit has been carried out. The goal in this part is to obtain the mean values for the velocity and pressure. The commercial code Fluent 12.1 is used for numerical simulations in two space dimensions. Secondly, numerical simulations of the acoustic part has been studied with the commercial software Comsol 3.5a with the objective to investigate the ability of the frequency domain Navier-Stokes equations to the characteristic properties of the acoustics at the duct termination. Finally, numerical results are compared to available experimental results with acceptable agreement which shows successes and also constraints of the simulations.

The ACM 2 spot weld model is the currently most widely used spot weld model in industry. It is designed to be tuned using parameters to represent the stiffness characteristics of a spot weld in a suitable way. The choice of these parameters is however often associated with uncertainties. Therefore, the set of parameters with best performance is determined by employing an updating algorithm. Further, the result is compared to a new category of models, the so called Spider models, which intend to overcome mesh dependence in the spot weld area by re-meshing the structures locally. The results are formulated as guidelines for the optimum implementation of these spot weld models for structural dynamics. The studies are performed using two cut-out parts from a Volvo FH truck cabin. In addition, a new analytical approach for updating material data of isotropic shell structures is derived and the equations are verified using the same test pieces.

No description available.

To be able to verify that a cylinder head design meats the expectations a good test method is needed. The aim of this thesis is to determine the best way of testing with respect to validity, cost, time consumption, quantity of tested material and repeatability. The base of the new method is the current single head method and this have been expanded to the suit the cylinder head of a seven litre engine currently in production. In order to determine how many cylinders to test and the order of these simulations of fatigue have been performed. Comparing these different ways of testing was done with a comparison of the safety factor against fatigue in a reference case composed of the ignition sequence and 17 feasible test methods. From the simulation results two suitable test fixtures have been designed in Catia. A method composed of two phases of pulsation with cylinders 1, 3 and 5 in the first phase and 2, 4 and 6 in the second phase is suggested as test method.

No description available.