Over the last few years Norway has seen an increasing number of hours where the grid frequency exceeds the required limits (49.9-50.1Hz). To improve this situation one alternative is to implement hydropower governing with quicker response time. However, long conduits and oscillatory flow set strict requirements to the hydropower system stability and turbo set governing. This thesis establishes a simulation program based on the structure matrix method for stability analysis of hydropower systems. The method is implemented in a Matlab program to study the oscillatory flow in the frequency domain. Implementation of frictional influence, turbine characteristics, and alternative governing has been given special attention. The program is validated through comparison with measurements and previous analysis at Kongsvinger and Tafjord power plants. The program simulations generally compare well with physical dynamics of the two systems. Further a stability analysis of speed governing at Aldal power plant has been performed. Finally some alternative control systems are discussed.

Denne masteroppgaven bygger videre på samme problemstilling som i fordypningsprosjektet (TMM 4501)”Analyse av Al-ekstrudering for å forhindre rekrystallisasjon”,høsten 2011.Oppgaven er gjennomført i samarbeid med Benteler Aluminum Systems Norway AS på Raufoss. Problemstillingen handler om uønsket grovrekrystallisering i aksesymmetrisk Al-ekstrudering ved senere prosessering. Det er gjennomgått teori som tar for seg opphavet til forskjellige rekrystalliseringsfenomerer under varmdeformasjon av Al-legeringer. Teorien tar for seg fysiske og empiriske rekrystallisasjonsmodeller. Fysiske modeller er baset på kornvekst, dannelser av subkorn og korngrenseorienteringer. Empiriske modeller inkluderer parametere som temperaturer, tøyninger, tøyningshastigheter og ulike konstanter. I tillegg belyser teorien ulike ekstruderingsforsøk og datasimuleringer av ulike varmformingsprosesser. Litteraturen har opphav fra ulike forskningsmiljøer. Fra besøk hos Bentlers industrilokaler på Raufoss ble det tatt med ekstruderte Al-prøver av aksesymmetrisk stangprofil tilbake til NTNU. På Verkstedtekniske laboratorier ble det kappet tre diskprøver fra den samme aluminiumen. Deretter ble diskene slipt, varmebehandlet og etset for å spore opp grovrekrystallisering i det ytre sjiktet av profilen.En simuleringsmodell fra fordypningsprosjektet har i denne oppgaven blitt forandret og tilpasset Bentelers største ekstruderingspresse P40. To stangprofiler med 80 og 43 mm i diameter ble simulert i Deform 2D.I Deform 3D ble det forsøkt simulert en kompleks modell av to paralelle hulprofiler som brukes i bilkonstruksjoner. Fra simuleringsmodellene er det vist bilder med tilhørende forklaringer.Resultater fra undersøkelsen av teori, skiveprøver og simuleringer er oppsummert og diskutert i eget kappittel.Rapporten er skrevet i Microsoft Word og datasimuleringer er gjennomført i Deform 2D og Deform 3D (versjon 10.2 og 11.0).

The purpose of this study was to explore the posibilities and challenges with simulating fatigue crack growth (FCG) by the extended finite element method (XFEM). Another aim was to develope a procedure for XFEM FCG simulations in Abaqus by means of scripting. Finally was the procedure used to simulate FCG in an API standard, cone shaped threaded connection. Different FCG models were reviewed by a limited litterature search and a procedure 2D FCG simulations was carried out by a python script. The procedure succeeded with the simulation of FCG when applied to a model with refined mesh around the crack tip. In the suggested partial tasks of the thesis description were a procedure 3D FCG simulation also suggested, but as this required more computer capacity than available in the study this was not carried out.

The goal of this Thesis is to verify a winning solution for the DNV Fuel Fighter 2, the verification of the design and development will be achieved by a series of verification, validation and testing activities.The Literature review of the report represents the VVT activities during the entire life cycle. The Theory and Methods used in the Thesis are based on A. Engel’s “Verification, Validation and Testing activities of Engineered Systems”. The author has customized those VVT activities so they fit the time and resource constrains of the case of study.The case is the NTNU’s fifth entrance to the Shell Eco Marathon competition, The DNV Fuel Fighter 2. The actual repot is a reflection of the first time in SEM’s project where an entire Thesis reflects the VVT activities in order to qualify the vehicle.This Master Thesis follows the work that was done in the specialization project 2011 fall in the NTNU. The fall report was focused on the trade-off and requirement analysis and in the definition a high level architecture that could be use in the project. The project work was used as a foundation for the work that was done afterwards in this Master Thesis. The work done during the year is based on the systems engineering effort made from the previous year. The author along with the other system engineer of the project has upgraded the SE effort.The main contribution of the Thesis has been the development of the VVT activities and to prove that they are useful for projects with time and resource constrains. The suggested future work consists of continuing with the use of the VVT strategy performed this year and to upgrade it until the Acceptance stage; where the final user will be the responsible of performing the tests.

The main goal for this thesis has been to perform fatigue life predictions on large components.Dierent methods were to be chosen and reviwed critically. Experimental datafor girth welded pipes was assessed by means of a version of BS7910 which were modeledfrom scratch. This version was veried with results from CrackWise, and used to predictthe fatigue life for loade cases matching the selected experimental data. The fatigue assessmenttool P-FAT was used to predict the fatigue life for the same experimental data,and the results were compared. Except for some deviations recorded for embedded cracks,a generally good agreement was found between the two tools.Both the modeled BS7910 and P-FAT predicted conservative but accurate fatigue livesfor the experimental data that had signicant defects. They predicted non conservativeresults for specimens that did not have signicant defects, when the initial crack depthwas set to 0.1 mm. When the initial crack depth was set to 0.5 mm the modeled versionpredicted fatigue lives in agreement with the experimental results.Fatigue life predictions were also performed by assistance of S-N curves provided by DNVRP-C203.The results from these predictions were in agreement with the experimentaldata, except for four specimens. These four specimens had signicant aws, which reducedthe fatigue life signicantly.A review of a two-phase fatigue assessment model was made. This model uses a strainedbased approach to assess the fatigue crack initiation phase, and the fracture mechanicapproach suggested in the BS7910 to assess fatigue crack growth. This method haveshown promising results for fatigue assessment of llet welds in the literature, but themodel needs further investigation and calibration to be used to predict fatigue life ofgirth welded structures. A specic area to investigate is the proposed transition depth of0.1 mm. This depth is dubious based on the results

This paper is a master thesis written at NTNU for the Co-Patch project. The Co-Patch project is an EU-funded consortium of 15 organizations from 8 different countries, developing a standard for composite patch repair of steel structures in fire hazard areas. The standard includes methods for dimensioning against delamination. This thesis looks at the fatigue properties in delamination of patches from their substrates. By testing Double Cantilever Beam and End-Notched Flexure specimens in fatigue loading, G-N curves were made for Mode I and Mode II fatigue fracture. This gives an indication of the lifetime of a patch given a specific cyclic load condition and a pre-existing crack. The longest cycle life recorded was 4.35E5 cycles at 104 J/m2 for Mode I and 1.23E5 cycles at 122 J/m2 for Mode II.Furthermore, a relation for crack propagation rate and energy release rate in Mode I was found for low cycle life estimation. From this relation, the crack front position may be estimated for a given set of cycles through calculations using Paris’ law. Based on the quasi-static data of a previous report, and the fatigue data found in this thesis, a numerical simulation procedure for crack propagation was proposed. Using direct cyclic fatigue analysis and Virtual Crack Closure Technique based on linear elastic fracture modelling, the crack propagation may be estimated for patches exposed to combined conditions, such as plane strain/plane stress and different fracture modes, as well as on advanced geometries. The procedure was validated as a viable simulation, but more work needs to be done on the model for accurate estimates. 

An experimental study of Carbon Nanotube (CNT) growth has been performed by using radio frequency plasma enhanced chemical vapour deposition with methane (CH4) as the hydrocarbon source. The experimental results have been compared towards earlier experiments and theories that exist. A study of the effect by changing parameters during thermal- and plasma- pretreatment has been conducted which have led to successful yield of vertically aligned CNTs forests. Different growth conditions have been conducted in order to see the influence of the following: Methane (CH4) flow, plasma power, growth time, temperature, methane (CH4)/ammonia (NH3) mixtures during growth, no barrier layer, thermal- versus plasma-pretreatment and oxidizing pretreatment. The conclusion from this experiment is that oxidizing pretreatment seems yields the tallest vertically aligned CNTs with the narrowest diameter.

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I dette prosjektet er en barnevugge blitt designet. Vuggen tar utgangspunkt i en vippemekanisme utviklet av Terje Rølvåg ved Institutt for Produktutvikling og Materialer på NTNU. Målet med prosjektet har vært å utforme en estetisk og funksjonell vugge tilpasset vippemekanismen. Mekanismen skal bidra til å roe barnet ved hjelp av vugging ved optimal frekvens.Det ble uført en enkel segmentanalyse hvor ulike brukergrupper og forretningsideer ble drøftet før et utvalgt konsept ble videreført. Dessuten ble det foretatt et litteratursøk for å underbygge tidligere undersøkelser som antydet en frekvens på 1-1,5 Hz som optimal vuggefrekvens for babyer.Basert på det valgte konseptet ble kundekrav og -interesser identifisert for å kunne lage en adekvat kravspesifikasjon. Forskjellige løsninger er presentert før ett av designene ble tatt videre og modellert i NX.Forskjellige sikkerhetsstandarder ble gjennomgått for å sikre optimal kvalitet på sluttproduktet. Det endelige designet er basert på gjeldende sikkerhetsstandarder for vugger samt funn fra brukeranalysen.Prosjektet resulterte i fire ulike designforslag. Det vil være opp til veileder eventuelt å føre et av disse designene videre.

The production of model Francis runner to be used in the Waterpower laboratory at NTNU is a length and costly process. Due to the production cost there are years between each time a new Francis model is bought. The Tokke Francis model at Waterpower laboratory, was given from the industry after they had run model tests in the laboratory when design- ing the Tokke prototype.In order to give the students at the Waterpower laboratory an opportunity to design their own turbines and test, the production cost must be significantly reduced. To be able to do that, new designs need to be developed and new production method used.The objective of this thesis is to carry out a new mechanical design of a Francis model runner and evaluate different mechanical designs of guide vanes and stay vanes. The new alternative designs were made with a combination of standard production methods and material, and new plastic materials from rapid prototyping such as selective laser sintering (SLS) and rapid CNC machining.To carry out the new mechanical runner design, the MATLAB design software Khoj was used. From Khoj two sets of streamlines were generated, one set for the sucction side and one for the pressure side. Then the streamlines were imported into the CAD program PTC Creo Parametric and a 3D-model of the design was made.Two test pieces in a polyamide material was made using selective laser sintering. One of the test pieces was tested for pull-out strength using some self tapping thread inserts, the results showed that the pull-out strength was more than good enough. The threaded insert could be used to attach the runner vanes to the hub and ring.The main focus of this thesis has been the new mechanical design of a model runner and runner vanes. The model design was not produced and tested in the laboratory due to lack of time and money.