The purpose of this study was to determine the validity and reliability of an 8-flight tower climb test (TCT) to assess anaerobic performance in urban firefighters. Twenty-five professional urban firefighters participated in the validity testing of the TCT versus the Wingate Anaerobic Test (WAT) over 2 randomly sequenced testing sessions. Test-retest reliability was assessed separately in 21 active male and female participants over 2 TCT trials. During both validity and reliability testing for the TCT, participants ascended a firefighting training tower as fast as possible from a 1.7m running start while wearing firefighter protective equipment. Time was measured and power was calculated from the foot of the training tower to the top of the first (height = 1.75m) and eighth (height = 13.89m) flights of stairs. During the other session assessing TCT validity, participants completed a 30-second WAT using a resistance of 85gkg-1 body weight (BW). Several significant correlations were found including those between TCT power and: 1) mean WAT power generated for the duration equivalent to TCT time (r = 0.869), 2) peak power for the first 2 seconds of the WAT (r = 0.868), and 3) WAT peak power (r = 0.864). TCT test-retest performance in 21 active males and females showed that the test is highly reproducible. The mean time of completion of the 8-flight TCT was 21.81 + 5.03 seconds and 21.38 + 4.86 seconds for Trials 1 and 2, respectively. Intraclass correlations for time and power data from the first and eighth flights ranged from 0.94 to 0.99, and coefficients of variance ranged from 2.0% to 7.5%. These findings provide strong evidence that the TCT is a valid and reliable field-based assessment of occupation-specific anaerobic performance in urban firefighters. / Graduate

Les aciers austénitiques inoxydables sont des candidats potentiels pour des composants de circuits des réacteurs de génération IV. Ces composants sont conçus pour fonctionner à hautes températures (500-600°C) et seront soumis à des sollicitations cycliques incluant de longs maintiens (~1mois) induisant une relaxation due aux phénomènes de viscoplasticité et de diffusion de lacunes. Ces temps de maintien sont inaccessibles en laboratoire d'où l'intérêt de la modélisation. L'objectif de cette étude a été de proposer des modèles de comportement capables de reproduire les différents mécanismes physiques observés expérimentalement. Dans un premier temps, une étude expérimentale a été menée sur l'acier 316L(N) incluant des essais de fatigue et de fatigue-relaxation à 500°C. Des essais de traction à différentes vitesses de déformation ont également été réalisés afin d'étudier le phénomène du vieillissement dynamique. La démarche de modélisation a été progressive. Nous nous sommes d'abord intéressés à la modélisation du comportement mécanique en fatigue pure et à température ambiante, pour différents matériaux métalliques de structure cubique à faces centrées dont l'acier 316L(N), en adoptant l'homogénéisation à champs moyens validée grâce à des calculs par éléments finis multicristallins. Ensuite, un modèle cristallin basé sur les densités de dislocations a été proposé et identifié pour des chargements de traction simple. Le modèle a ensuite été enrichi afin de prendre en compte les mécanismes de viscoplasticité, de montée et le vieillissement dynamique. le modèle fait appel à trois paramètres ajustables seulement et prédit correctement les courbes de traction et de relaxation. / Austenitic stainless steels are potential candidates for structural components of sodium-cooled fast neutron reactors. Many of these components will be subjected to cyclic loadings including long hold times (~ 1month) under creep or relaxation at high temperature. These hold times are unattainable experimentally. The aim of the present study is to propose mechanical models which take into account the involved mechanisms and their interactions during such complex loadings. First, an experimental study of the pure fatigue and fatigue-relaxation behavior of 316L(N) at 500°C has been carried out with very long hold times (10h and 50h) compared with the ones studied in literature. Tensile tests at 600°C with different applied strain rates have been undertaken in order to study the dynamic strain ageing phenomenon. Before focusing on more complex loadings, the mean field homogenization approach has been used to predict the mechanical behavior of different FCC metals and alloys under low cycle fatigue at room temperature. Both Hill-Hutchinson and Kröner models have been used. Next, a physically-based model based on dislocation densities has been developed and its parameters measured. The model allows predictions in a qualitative agreement with experimental data for tensile loadings. Finally, this model has been enriched to take into account viscoplasticity, dislocation climb and interaction between dislocations and solute atoms, which are influent during creep-fatigue or fatigue relaxation at high temperature. The proposed model uses three adjustable parameters only and allows rather accurate prediction of the behavior of 316L(N) steel under tensile loading and relaxation.

<p>Materials to be used in thermal power plants have to resist creep deformation for time periods up to 30 years. The role of alloying elements for creep strength of 9-12% Cr steels is analysed. The creep strength in these steels relies on minor additions of alloying elements. Precipitates give rise to the main strengthening and remaining elements produce solid solution hardening. Nucleation, growth and coarsening of particles are predicted by thermodynamic modelling. Phase fractions and size distributions of M₂₃C₆ carbides, MX carbonitrides and Laves phase are presented. The size distributions are needed in order to determine the particle hardening during creep. At elevated temperatures the climb mobility is so high that the dislocations can climb across particles instead of passing by making Orowan loops.</p><p>By solving Fick's second law the concentration profile around a moving dislocation can be determined. The results show an accumulation of solutes around the dislocation that slows down dislocation movement. When Laves phase grows a decrease in creep strength is observed due to a larger loss in solid solution hardening than strength increase by particle hardening. Solid solution hardening also gives an explanation of the low dislocation climb mobility in 9-12% Cr steels.</p><p>Three different dislocation types are distinguished, free dislocations, immobile dislocation and immobile boundary dislocations. This distinction between types of dislocations is essential in understanding the decreasing creep with strain during primary creep. The empirical relation with subgrain size inversely proportional to stress has been possible to predict. The total creep strength can be predicted by adding the contribution from individual mechanisms.</p>

Materials used in thermal power plants have to resist creep deformation for time periods up to 30 years. Material evaluation is typically based on creep testing with a maximum duration of a few years. This information is used as input when empirically deriving models for creep. These kinds of models are of limited use when considering service conditions or compositions different from those in the experiments. In order to provide a more general model for creep, the mechanisms that give creep strength have to be identified and fundamentally described. By combining tools for thermodynamic modelling and modern dislocation theory the microstructure evolution during creep can be predicted and used as input in creep rate modelling. The model for creep has been utilised to clarify the influence of aluminium on creep strength as a part of the European COST538 action. The results show how AlN is formed at the expense of MX carbonitrides. The role of heat treatment during welding has been analysed. It has been shown that particles start to dissolve already at 800ºC, which is believed to be the main cause of Type IV cracking in commercial alloys. The creep strength of these steels relies on minor additions of alloying elements. Precipitates such as M23C6 carbides and MX carbonitrides give rise to the main strengthening, and remaining elements produce solid solution hardening. Particle growth, coarsening and dissolution have been evaluated. By considering dislocation climb it is possible to determine particle strengthening at high temperatures and long-term service. Transient creep is predicted by considering different types of dislocations. Through the generation and recovery of dislocation densities an increase in work hardening during primary creep is achieved. The role of substructure is included through the composite model. Cavity nucleation and growth are analysed in order to explain the intergranular fracture and to estimate the ductility. / QC20100616

abstract: The Doghouse Plot visually represents an aircraft’s performance during combined turn-climb maneuvers. The Doghouse Plot completely describes the turn-climb capability of an aircraft; a single plot demonstrates the relationship between climb performance, turn rate, turn radius, stall margin, and bank angle. Using NASA legacy codes, Empirical Drag Estimation Technique (EDET) and Numerical Propulsion System Simulation (NPSS), it is possible to reverse engineer sufficient basis data for commercial and military aircraft to construct Doghouse Plots. Engineers and operators can then use these to assess their aircraft’s full performance envelope. The insight gained from these plots can broaden the understanding of an aircraft’s performance and, in turn, broaden the operational scope of some aircraft that would otherwise be limited by the simplifications found in their Airplane Flight Manuals (AFM). More importantly, these plots can build on the current standards of obstacle avoidance and expose risks in operation. / Dissertation/Thesis / Masters Thesis Aerospace Engineering 2017

This diploma thesis describes the design of the E2 hill climb car and it is design by following the FIA rules. Next parts are focused on detailed design of the front and rear suspension and design of the frame. Diploma thesis is processed using CAD system Autodesk Inventor 2011, in which was created all sketches and models. The suspension geometry during bound and rebound movement of the wheel was made in MBS system MSC Adams 2010. FEM analysis of the frame was made in ANSYS Workbench 12.1.

Des amas de lacunes ont été observés et caractérisés expérimentalement dans les métaux de haute pureté après déformation plastique ou après une suite de traitements thermiques particuliers. Ces amas sont des obstacles à la propagation des dislocations et peuvent par conséquent induire un durcissement du métal.Cette étude par simulations numériques a permis d'explorer différents mécanismes de propagation de dislocations dans une concentration d'amas en fonction de la contrainte de cisaillement appliquée et de la température. À haute contrainte, la force appliquée sur la dislocation devient supérieure aux forces d'ancrage s’exerçant sur la ligne. La dislocation franchit la distribution d'amas en glissant et en cisaillant les amas. La dépendance de la force d'ancrage en fonction de la taille de l'amas est ajustée sur nos simulations de statique moléculaire. Dans ce domaine de contrainte, les configurations d'amas ancrant la dislocation sont rares et l'activation thermique suffit à désancrer la ligne. La probabilité de désancrer la ligne dépend de l'enthalpie d'activation, un paramètre que nous avons également estimé à l'aide d'un modèle analytique ajusté sur nos résultats atomistiques. À plus faible contrainte, lorsque la force appliquée est inférieure aux forces d'ancrage induites par les amas, la probabilité que la dislocation se désancre uniquement par glissement devient faible. La diffusion des lacunes, émises préférentiellement des amas, intervient alors et favorise la formation de crans. Cela contribue au désancrage de la ligne. Ce mécanisme est le glissement assisté par la montée. Les barrières d'émission, d'absorption et de migration de lacunes ont été déterminées par statique moléculaire et sont fortement dépendantes du champ élastique et de la distorsion du réseau atomique générés par la présence de la dislocation. Cela induit une forte anisotropie de diffusion au voisinage des dislocations qui conduit notamment au mécanisme de 'pipe diffusion'. L'évolution au cours du temps de l'ensemble de ces mécanismes a été étudiée à l'aide d'un modèle de ligne élastique couplé à un algorithme de Monte Carlo cinétique dont l'ensemble des barrières d'énergie provient de nos simulations atomistiques. Moyennant les hypothèses du modèle, nous avons alors obtenu une estimation de la vitesse des dislocations en fonction de la contrainte et de la température appliquée. Nous avons ensuite utilisé la loi d'Orowan pour estimer la vitesse de déformation liée à ces mécanismes. / Vacancy clusters have been observed and characterized experimentally in highly pure metals after plastic deformation or after a particular sequence of heat treatments. These clusters hinder the dislocation propagation and can therefore harden the metal.Using numerical simulations we have explored different mecanisms of dislocation propagation through a vacancy-cluster distribution, for several applied shear stress and temperature. At high stresses, the force applied on the dislocation becomes greater than the pinning forces acting on the line. The dislocation gets through the cluster distribution by gliding and shearing the clusters. The dependence of the pinning force with the cluster size is adjusted on our molecular static simulations. In this stress range, the pinning configurations are rare and the thermal activation is sufficient to unpin the line. The probability for the line to pass the pinning configuration depends on the activation enthalpy, a parameter that we have also estimated using an analytical model adjusted on our atomistic results. At lower stresses, when the applied force is below the pinning forces induced by the cluster, the probability that the dislocation unpins by pure glide becomes negligeable. The diffusion of vacancies, emitted preferentially from the vacancy clusters, intervenes and promotes the formation of jogs that contributes to the unpinning of the line. Such a mecanism is the glide assisted by climb. The emission, the absorption and the vacancy migration barriers have been determined by molecular static and are highly dependent on the elastic field and the atomic network distortion induced by the dislocation. This promotes a strong diffusion anisotropy in the vicinity of the dislocations which leads in particular to the pipe diffusion mechanism. The evolution with time of all these mechanisms has been studied using an elastic line model coupled to a kinetic Monte Carlo algorithm in which the parameters come from our atomistic simulations. According to the model assumptions, we obtained an estimation of dislocation velocity as a function of the applied shear stress and the temperature. We used the Orowan's law to estimate the strain rate related to such mechanisms.

No description available.

Materials to be used in thermal power plants have to resist creep deformation for time periods up to 30 years. The role of alloying elements for creep strength of 9-12% Cr steels is analysed. The creep strength in these steels relies on minor additions of alloying elements. Precipitates give rise to the main strengthening and remaining elements produce solid solution hardening. Nucleation, growth and coarsening of particles are predicted by thermodynamic modelling. Phase fractions and size distributions of M23C6 carbides, MX carbonitrides and Laves phase are presented. The size distributions are needed in order to determine the particle hardening during creep. At elevated temperatures the climb mobility is so high that the dislocations can climb across particles instead of passing by making Orowan loops. By solving Fick's second law the concentration profile around a moving dislocation can be determined. The results show an accumulation of solutes around the dislocation that slows down dislocation movement. When Laves phase grows a decrease in creep strength is observed due to a larger loss in solid solution hardening than strength increase by particle hardening. Solid solution hardening also gives an explanation of the low dislocation climb mobility in 9-12% Cr steels. Three different dislocation types are distinguished, free dislocations, immobile dislocation and immobile boundary dislocations. This distinction between types of dislocations is essential in understanding the decreasing creep with strain during primary creep. The empirical relation with subgrain size inversely proportional to stress has been possible to predict. The total creep strength can be predicted by adding the contribution from individual mechanisms. / QC 20101112

Thesis analyses the problem about motorsport discipline hill climb races. Using the findings is designed database structure and created user application together with websites for current result publishing. The work also describes the hardware that is compatible with this application.