Problematik med utmattningsbrott är känt sedan början på 1800-talet och fenomenet har studerats sedan dess. Efter lång tids arbete har man hittat en metodik för att ta fram analytiska beräkningsmodeller samt säkra och noggranna livslängdsberäkningar för stålkonstruktioner. Syftet med detta arbete har varit att undersöka en marin ångpannas utmattningshållfasthet under loppet av dess ekonomiska livslängd. I den här studien har en analytisk beräkning gjorts på en marin ångpannas utmattningslivslängd med hjälp av DNV ́s regler för klassifikation av fartyg samt Europeiska tryckkärlsnormen. I studien har författarna tagit hänsyn till ångpannans tryckvariationer, temperaturvariationer samt den marina ångpannans yttre påverkan från fartygets rörelse i vattnet och de resulterande hävkrafterna. Detta för att med hög tillförlitlighet (konfidens) kunna värna om människoliv, natur och miljö, fysisk egendom (fartyg samt last), operativa tillgänglighet samt lagar och regler. / Problems with fractures due to fatigue have been known since the early 19th century, and the phenomenon has been studied since then. After long periods of work, a methodology has been found to develop analytical fatigue calculation models for steel structures. The purpose of this work has been to investigate the fatigue assessments of marine boilers during it ́s economic lifetime. In this study, an analytical calculation has been made of the marine boiler using DNV's ship classification rules and the European pressure vessel standard. In the study, the authors have taken into account the boilers pressure variations, temperature variations, and the marine boiler's external impact from the vessel's motion in the water and the resulting forces. In order to be able to protect human life, nature and the environment, physical property (ships and cargo), operational availability as well as laws and regulations, with high reliability (confidentiality).

This master thesis deals with lower-limb prosthesis. The aim of the first part of this work is stress-strain analysis of trans-tibial prosthesis, which is understand without prosthetic socket and the foam prosthetic feet. Analysis is made using finite element method in ANSYS Workbench 12.0 software. For the purpose of setting up the computational model it is necessary to make few partial models. Model of geometry of the prosthesis is made in SolidWorks 2009. Based on the outputs of stress-strain analysis and the results evaluation, the critical component is chosen and this one is evaluated according to limite state for fatigue. The algorithm of evaluation of named component in the state of high cycle fatigue is discussed in the second part of this thesis.

Les machines agricoles doivent être conçues pour être optimales, fiables et résistantes à la rupture par fatigue. L’approche déterministe de la conception ne garantit pas ces exigences, elle est néanmoins traditionnellement appliquée pour la conception de machines agricoles. Cela est dû à la difficulté de modéliser la nature stochastique des forces agissant sur les machines agricoles, en particulier les machines de labour, car elles fonctionnent dans un environnement irrégulier et dans des conditions de fonctionnement variables. Le principal objectif de cette thèse est de développer un cadre général pour la conception de machines agricoles, en intégrant les outils d'optimisation, de fiabilité et de fatigue. En cela, nous visons à proposer une alternative à l'approche déterministe. Tout d'abord, cette thèse propose des méthodes et des modèles pour modéliser la variabilité des forces durant le labour en prenant en compte à la fois la variabilité des paramètres du système de labour et de rupture du sol. Deuxièmement, sur la base des méthodes d’optimisation fiabiliste et d’analyse de la fatigue, nous proposons des méthodologies pour la conception de machines agricoles. Tout au long de la thèse, les approches développées sont appliquées à la conception de la dent d'un chisel. / Agricultural machines should be designed to be optimal, reliable and have thecapacity to resist failure by fatigue. Although, the deterministic design approach does not guarantee these requirements, it is traditionally applied in the design of agricultural machines. This is due to the difficulties to model the stochastic nature of the forces acting on agricultural machines, especially the forces acting on tillage machines which work in irregular environment and under varying conditions. Therefore, the main objective of this dissertation is to develop a general framework for the design of agricultural machines by integrating the optimization, the reliability and the fatigue tools. We aim to provide an alternative to the traditional deterministic design one. First, this dissertation proposes methods and models for modeling the variability in tillage forces considering both thevariability in tillage system parameters and the soil failure. Second, based on the available methods in reliability-based design optimization and fatigue analysis approaches, itproposes methodologies for the design of agricultural machines. Throughout the dissertation, the developed approaches are applied to the design of the shack of a chisel plough.

Steel Catenary Riser (SCR) is a popular solution for a floating production facility in the deep and ultra-deep ocean. In the analysis of SCR, the behavioral characteristics are investigated to check the failure modes by assessing the magnitude and the frequency of the stress and strain which SCR goes through in time series. SCR is affected by the motions of connected floating production facility and exciting environmental loads. The driven force and motion of SCR has an interaction with seabed soil which represents the stiffness and friction force where SCR touches the seabed. Dynamic response of SCR is primarily caused by the coupled motion of floating structure. The displacement of floating structure is often large and fast enough to cause short cycles of negative and positive tension on SCR. The interaction between SCR and seabed is concentrated at the touchdown zone resulting into the compression and corresponding deformation of pipeline at the position. This paper presents models of floating production facilities and connected mooring lines and SCRs in 100-year hurricane environmental loads and seabed, focusing on the motional characteristics of SCR at the touchdown zone. In time series simulation, the model of SCR is first analyzed as a pipeline with indefinite elasticity so that the SCR does not fail even if the exciting loads exceed the property limit of SCR. Then the SCR design is manually checked using criteria for each failure mode to estimate the integrity.

In the field of ergonomics, biomechanics, sports and rehabilitation muscle fatigue is regarded as an important aspect since muscle fatigue is considered to be one of the main reasons for musculoskeletal disorders. Classical signal processing techniques used to understand muscle behavior are mainly based on spectral based parameters estimation, and mostly applied during static contraction and the signal must be stationary within the analysis window; otherwise, the resulting spectrum will make little physical sense. Furthermore, the shape and size of the analysis window also directly affect the spectral estimation. But fatigue analysis in dynamic conditions is of utmost requirement because of its daily life applicability. It is really difficult to consistently find the muscle fatigue during dynamic contraction due to the inherent non-stationary nature and associated noise in the signal along with complex physiological changes in muscles. Nowadays, in addition to linear signal processing, different non-linear signal processing techniques are adopted to find out the consistent and robust indicator for muscle fatigue under dynamic condition considering the high degree of non-linearity (caused by functional interference between different muscles, changes of signal sources and paths to recording electrodes, variable electrode interface etc.) in the signal. In this work, various linear and nonlinear-non-stationary signal processing methods, applied on surface EMG signal for muscular fatigue analysis under dynamic contraction are studied. In present study, surface EMG (sEMG) signals are recorded from Biceps Brachii muscles from eight (N=8) physically active college students during dynamic lifting 7 kg load at the rate of 20 lifts/min till they become fatigue. EMG data is processed in two ways -1. taking the whole EMG response and 2. breaking into three ranges of contraction (0-45)o, (45-90)o and >90o, to study better response region. It is observed that in spectral estimation techniques auto-regressive (AR) based spectral estimation technique gives better frequency resolution than periodogram for small epochs, as AR is based on parametric estimation. Both the previous methods provide only the frequency information in the signal. In order to estimate the time varying nature of frequency content in a signal various time-frequency signal processing techniques are used like – Short Time-Fourier Transform (STFT), Smoothed pseudo Wigner-Ville (SPWD), Choi-William distribution (CWD), Continuous Wavelet Transform (CWT), Huang-Hilbert Transform (HHT) and Recurrence Quantification Analysis (RQA) are used. The last two techniques are used by considering the EMG signal as non-linear and non-stationary signals. Among these techniques, STFT is the simplest time-frequency analysis technique. But tradeoff between time and frequency resolution is the major constraint in STFT, therefore, a window length of 256 samples are considered in this study. In order to tackle time-frequency resolution problem different Cohen-class distribution techniques are used like SPWD and CWD, where the result is severely affected by the presence of interference terms which make its interpretation really difficult. Different adaptive filters are used in SPWD and CWD to suppress these interference terms during analysis. Among these time-frequency analysis techniques continuous wavelet transform provides the most accurate results in comparison to other time-frequency analysis techniques. Similar result is obtained in present study. This fatigue response is further improved using non-linear and non-stationary techniques like HHT and RQA. HHT shows less variation in frequency response than CWT analysis result. Percentage of determinism calculated using recurrence quantification analysis method is found to be more sensitive than mean frequency estimation. Therefore, non-linear and non-stationary signal processing techniques are to be better indicator of muscle fatigue during dynamic contraction.

Fatigue analysis is a critical stage in the design of any structural component. Typically fatigue is analysed during post-processing, but as the size of the analysed component increases, the amount of data stored for the analysis increases simultaneously. This increases the computational and memory requirements of the system, intensifying the work load on the engineer. A continuum mechanics approach namely ’Continuous time fatigue model’, for fatigue analysis is available in a prior study which reduces the computational requirements by simultaneously computing fatigue along with the stress. This model implements a moving endurance surface in the stress space along with the damage evolution equation to compute high-cycle fatigue. In this thesis the continuous time fatigue model is compared with conventional model (ie.Cycle counting) to study its feasibility. The thesis also aims to investigate the continuous time fatigue model and an evolved version of the model is developed for non-proportional load cases to identify its limitations and benefits.

Mobility is a symbol of dignity. A platform lift enables everyone of different physical abilities to move vertically with ease. Currently, the platform lift by Aritco Lift is made of steel sheet metal. It is heavy, thus difficult to handle. Sandwich design is researched to see whether and, if possible,how much dead load reduction. A simulation model is produced in SolidWorks to facilitate the material selection and the sandwich design. Sandwiches of aluminium face sheets are investigated, although steel face sheet works as well. No recommendation on core material can be made. Connection methods are investigated in SolidWorks to join the 35mm-thick sandwich-based floor to the lift body without creating a large deflection. Several general directions are investigated. None yielded results sufficiently satisfactory, although two directions have provided results that are very close to the requirements. Simulations are conducted on a 40mm-thick sandwich using one of the optimal joint options, yielding better weight savings and deflection results. Certain honeycomb properties are approximated using formulae rather than measured or simulated directly. To quantify how significant is the deviation of the approximated model, simulations are conducted by changing the length, width, and height of the sandwiches modelled using both the approximation and exact geometry. Fatigue life analyses are conducted on two of the candidate floors. Both are comfortably within the limit imposed by the standards. The success of a design in this thesis hinged on the validity of the honeycomb model. The test results reject the honeycomb model as the deflection is significantly higher than simulated. Plastic deformation has also occurred, though more probably due to the deformation local at the weld. Even though honeycomb is demonstrated not to be able to meet the requirements on its own, sandwich as a category of structure should not be discounted as a whole. Environmental factor is a drawback for using large quantities of aluminium even considering the weight difference between the design and the original steel structure. / Rörlighet är en symbol för värdighet. En plattformslyft gör att alla med olika fysiska förmågor kan röra sig vertikalt med lätthet. För närvarande är plattformslyften av Aritco Lift gjord av stålplåt. Den är tung och därför svår att hantera. Sandwichdesign undersöks för att se om och, om möjligt, hur mycket egenlastreduktion kan åstadkommas. En simuleringsmodell tas fram i SolidWorks för att underlätta materialvalet och sandwichdesignen. Sandwichkonstruktioner av aluminiumplåtar undersöks, även om stålplåt fungerar också. Ingen rekommendation om kärnmaterial kan ges. Fogningsmetoder undersöks i SolidWorks för att sammanfoga det 35 mm tjocka sandwichbaserade golvet till lyftkroppen utan att skapa en stor nedböjning. Flera allmänna riktningar utreds. Ingen av dessa gav tillräckligt tillfredsställande resultat, trots att två riktningar har gett resultatsom ligger mycket nära kraven. Simuleringar utförs på en 40 mm tjock sandwich med ett av de optimala fogalternativen, vilket ger bättre viktbesparingar och nedböjningsresultat än förväntat. Vissa bikakeegenskaper uppskattas med formler snarare än att mätas eller simuleras direkt. För att kvantifiera hur betydande avvikelsen av den approximerade modellen är, genomförs simuleringar där längden, bredden och höjden ändras på de modellerade sandwicharna med användning av både approximationer och data från den exakta geometrin. Utmattningsanalyser genomförs på två av designförslagen. Båda är bekvämt inom de gränser som ställs av standarderna. Framgången för en design i denna avhandling hängde på giltigheten av honeycomb-modellen. Testresultaten förkastar modellen eftersom nedböjningen är betydligt högre än simulerad. Plastiskdeformation har också förekommit, men troligen på grund av den lokala deformationen vid svetsen. Även om honeycomb har visat sig inte kunna uppfylla kraven på egen hand, bör sandwich som strukturkategori inte bortses från som helhet. Miljöfaktorn är en nackdel för att använda stora mängder aluminium även med tanke på viktskillnaden mellan konstruktionen och den ursprungliga stålkonstruktionen.

RESUME A partir de lanalyse des incidents des FSOs de type CALM Soft Yoke de Vietsovpetro aux gisements White Tiger (Tigre Blanc) et Dragon, on saperçoit du besoin de développer des structures offshore (y compris les FPSOs) installées et opérées «en sécurité» dans les conditions spéciales des états de mer du Vietnam, où apparaissent de nombreux vents violents et de fréquents typhons tropicaux. Dans le cadre de cette thèse, une recherche générale sur les systèmes dancrage des FPSO a été réalisée en considérant divers problèmes : efforts hydrodynamiques du second ordre, réponses dynamiques aléatoires des systèmes dancrage des FPSO, analyses du dommage de fatigue aléatoire et estimation de la durée de vie des lignes dancrage. Plus spécialement, une étude plus approfondie avec un nouveau concept a été proposée pour estimer la fiabilité totale dun système de lignes d'ancrage des FSPO. La fiabilité totale a été déterminée selon les conditions de mer extrêmes (ULS), elle diminue avec le temps à cause de la prise en compte de l'accumulation du dommage en fatigue des lignes d'ancrage (FLS). Dans la dernière part de thèse, cette méthode a été appliquée aux conditions de mer sévères du Vietnam, surtout dans les états limites extrêmes, prenant en compte l'accumulation du dommage en fatigue. En application numérique, deux FSOs existants au Vietnam ont été analysés. Le contenu principal des études de la thèse a également contribué à réaliser un Projet National de Recherche du Vietnam (intitulé code KC.09.15/06-10), dont lun des membres est lauteur de cette thèse./ ABSTRACT From analyzing incidents of the CALM Yoke FSOs of Vietsovpetro in the White Tiger and Dragon fields, we can identify the need to develop offshore structures (including FPSO) installed and operated in safety in most severe Vietnamese sea states, with many and frequent strong winds and tropical typhoons. In this thesis, a general research on the FPSO mooring systems has been carried out by considering various problems: second order hydrodynamic efforts, random dynamic responses of the FPSO mooring systems, analyzing random damage of fatigue and estimating the durability of the mooring lines. In particular, a thorough study with a new concept was proposed to estimate the total reliability of FSPO mooring line systems. The total reliability was estimated for extreme sea conditions (ULS), which decreases with the time due to the accumulation of the damage by fatigue of the moorings lines (FLS). In the last part of thesis, this method was applied to the severe sea conditions of Vietnam, especially considering the ultimate limit states and taking into account the accumulation of the fatigue damage. For numerical application, two FSOs existing now in Vietnam were analyzed. The main studies in this thesis have also contributed to develop a National Research Project in Vietnam (entitled code KC.09.15/06-10), in which the author acts as a research team member.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / As pontes rodoviárias de concreto armado estão sujeitas à ações dinâmicas variáveis devido ao tráfego de veículos sobre o tabuleiro. Estas ações dinâmicas nem sempre são corretamente consideradas pelos projetistas. Deste modo, a correta consideração destes aspectos mostra-se de fundamental importância, de forma a se avaliar os esforços dinâmicos oriundos do tráfego de veículos sobre o tabuleiro. De acordo com este contexto, a ponte rodoviária investigada nesta dissertação é constituída por duas vigas longitudinais, três transversinas, sendo uma central e duas sobre os apoios, e por um tabuleiro em concreto armado. O modelo computacional, desenvolvido para a análise dinâmica da ponte, foi concebido com base no emprego de técnicas usuais de discretização através do método dos elementos finitos. Os veículos são representados a partir de sistemas do tipo "massa-mola-amortecedor". O tráfego destes veículos é considerado mediante a simulação de comboios semi-infinitos, deslocando-se com velocidade constante sobre a ponte. As técnicas para a contagem de ciclos de tensões e a aplicação das regras de dano acumulado foram analisadas através das curvas S-N de diversas normas e recomendações internacionais vigentes que versam sobre o tema. As conclusões deste trabalho de pesquisa se referem à análise da resposta dinâmica bem como da vida útil de serviço da obra de arte rodoviária de concreto armado investigada, quando submetida às ações dinâmicas provenientes do tráfego de veículos pesados sobre o tabuleiro. / Reinforced concrete highway bridges are subjected to dynamic actions of variable magnitude due to vehicles crossing on the deck pavement. In general, these dynamic actions are not properly considered by the designers. The proper consideration of these aspects has shown to be of fundamental importance to assess the actions from the vehicles traffic on the bridge deck. According to this context the investigated bridge consists of two longitudinal beams (girders), three transverse beams, one central and two on the supports, and a reinforced concrete deck. The computational model, developed for the bridge dynamic analysis, adopted the usual mesh refinement techniques present in finite element method simulations. The vehicles were simulated by spring-mass-damper models. The vehicles traffic is considered based on semi infinity convoys moving with constant speed on the bridge deck. The stress cycles counting techniques and the cumulative damage rules were applied through S-N curves related to international codes. The conclusions of this research were related to the dynamic response as well the service life of the investigated highway reinforced concrete bridge, when subjected to dynamic actions from the heavy vehicles traffic on the deck pavement surface.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / As pontes rodoviárias de concreto armado estão sujeitas à ações dinâmicas variáveis devido ao tráfego de veículos sobre o tabuleiro. Estas ações dinâmicas nem sempre são corretamente consideradas pelos projetistas. Deste modo, a correta consideração destes aspectos mostra-se de fundamental importância, de forma a se avaliar os esforços dinâmicos oriundos do tráfego de veículos sobre o tabuleiro. De acordo com este contexto, a ponte rodoviária investigada nesta dissertação é constituída por duas vigas longitudinais, três transversinas, sendo uma central e duas sobre os apoios, e por um tabuleiro em concreto armado. O modelo computacional, desenvolvido para a análise dinâmica da ponte, foi concebido com base no emprego de técnicas usuais de discretização através do método dos elementos finitos. Os veículos são representados a partir de sistemas do tipo "massa-mola-amortecedor". O tráfego destes veículos é considerado mediante a simulação de comboios semi-infinitos, deslocando-se com velocidade constante sobre a ponte. As técnicas para a contagem de ciclos de tensões e a aplicação das regras de dano acumulado foram analisadas através das curvas S-N de diversas normas e recomendações internacionais vigentes que versam sobre o tema. As conclusões deste trabalho de pesquisa se referem à análise da resposta dinâmica bem como da vida útil de serviço da obra de arte rodoviária de concreto armado investigada, quando submetida às ações dinâmicas provenientes do tráfego de veículos pesados sobre o tabuleiro. / Reinforced concrete highway bridges are subjected to dynamic actions of variable magnitude due to vehicles crossing on the deck pavement. In general, these dynamic actions are not properly considered by the designers. The proper consideration of these aspects has shown to be of fundamental importance to assess the actions from the vehicles traffic on the bridge deck. According to this context the investigated bridge consists of two longitudinal beams (girders), three transverse beams, one central and two on the supports, and a reinforced concrete deck. The computational model, developed for the bridge dynamic analysis, adopted the usual mesh refinement techniques present in finite element method simulations. The vehicles were simulated by spring-mass-damper models. The vehicles traffic is considered based on semi infinity convoys moving with constant speed on the bridge deck. The stress cycles counting techniques and the cumulative damage rules were applied through S-N curves related to international codes. The conclusions of this research were related to the dynamic response as well the service life of the investigated highway reinforced concrete bridge, when subjected to dynamic actions from the heavy vehicles traffic on the deck pavement surface.