Coiled springs are one of the important parts providing comfort during driving vehicles. These components highly demand on their fatigue life. This thesis examines the possibility of the influence of surface quality of a spring wire during production process of coiled springs on their mechanical properties and durability.

La région sahélienne est caractérisée, depuis la moitié du XXème siècle, par un déficit pluviométrique important marqué par de fortes sécheresses en 1972-73 et en 1983-84 qui ont eu des effets considérables sur l'écosystème, les ressources et la population locale. Les réponses hydrologiques induites par ce déficit se traduisent par des effets contrastés suivant la zone géographique considérée. Si dans la zone soudano-guinéenne, une baisse des écoulements de surface a été observée, la zone sahélienne, paradoxalement, a connu une augmentation de ces écoulements durant la même période. La plupart des études visant à mieux comprendre cette évolution paradoxale ont été effectuées en milieu sahélien cultivé, où l'augmentation du ruissellement a souvent été attribuée au changement d'usage des sols suite aux besoins de la population croissante. Toutefois, ce même phénomène est aussi observable dans les zones majoritairement pastorales où les modifications d'usage des sols ne suffisent pas à expliquer les modifications hydrologiques observées. Les objectifs de cette thèse consistent à étudier, au travers de la modélisation hydrologique, l'évolution conjointe des différents processus régissant l'hydrologie sahélienne et de hiérarchiser leurs impacts sur l'évolution du ruissellement de surface sur les 50 dernières années en milieu pastoral. Pour ce faire, le modèle de ruissellement KINEROS2, a été appliqué au bassin versant d'Agoufou. Ce bassin de type endoréique est situé dans la région du Gourma, au Mali et est instrumenté par le service d'observation AMMA-CATCH qui fournit une partie des données nécessaires au forçage et à l'évaluation du modèle. La première partie de ces travaux a été dédiée à la quantification des changements survenus au cours des 50 dernières années sur ce bassin ainsi qu'au niveau de son exutoire, le lac d'Agoufou. Une cartographie des unités paysagères identifiées à partir d'images satellite et de photographies aérienne, a été réalisée pour les années 1956 et 2011. Cette cartographie a mis en évidence l'évolution des états de surface, marquée par l'érosion des sols peu profonds et la dégradation de la végétation de type brousse tigrée en faveur de l'extension des surfaces de sols nus (+35 km² entre 1956 et 2011) ainsi que par l'augmentation de la densité du réseau de drainage (×1.5) et par celle de la superficie du lac (534 m² en 1956 pour 2×106 m² en 2011). L'évolution du débit au cours du temps a été quantifiée à partir des variations de volume du lac établies via une relation entre les surfaces estimées par télédétection et les hauteurs d'eau mesurées in-situ. Cette relation a été couplée à une équation de bilan d'eau, prenant en compte les précipitations, l'évaporation et l'infiltration sur le lac pour quantifier les apports d'eau à l'exutoire. Nous avons ainsi mis en évidence l'évolution nette du coefficient de ruissellement du bassin qui est passé de 0% dans les années 1970 à 5.5 % dans les années 2000. La deuxième partie de cette thèse a été consacrée à la modélisation hydrologique et à la réalisation de simulations de références et d'attribution des changements observés à différents facteurs. L'augmentation des surfaces de sols nus associée à une diminution de la végétation explique largement l'évolution de l'hydrologie de surface du bassin depuis les années 1960. Le développement du réseau de drainage et l'encroûtement des dunes jouent des rôles secondaires dans cette évolution. En revanche, la variation du régime des pluies, tend à diminuer le ruissellement au cours du temps de plus de 34%. Les mécanismes identifiés sur le bassin d'Agoufou montrent l'importance de la dynamique du système couplé végétation/érosion/réseau hydrique et de leurs rôles sur d'autres bassins Sahéliens où l'augmentation du ruissellement a été également mise en évidence. / Since the mid-twentieth century, the Sahel is characterized by a significant rainfall deficit marked by severe droughts in 1972-73 and 1983-84 that have significantly impacted ecosystems, resources and local population. The responses induced by this deficit result in opposite effects according to geographical area. If, in the Sudano-Guinean zone, a reduced surface runoff was observed, the Sahel experienced a paradoxical increase of surface runoff during the same period. Most of the studies aiming at understanding this paradoxical situation have been performed in crop-dominated areas, where the runoff increase has been attributed to land use change following population growth. However, the same phenomenon is also observed in pastoral areas where land use change cannot explain the observed hydrological changes. The objective of this thesis is to study the different processes governing Sahelian hydrology and prioritize their impact on the surface runoff evolution in pastoral areas by means of hydrological modeling. To do this, the KINEROS2 runoff model was applied to the Agoufou watershed. This endorheic watershed is located in the Gourma region, in Mali. It is instrumented by the AMMA-CATCH observatory, which provides most of the necessary data for forcing and evaluating the model. The first part of this work was dedicated to the quantification of the changes occurred over the last 50 years on the Agoufou watershed and its outlet, the Agoufou lake. Land cover maps derived from satellite images and aerial photographs for 1956 and 2011 allowed estimating the changes in surface characteristics. Erosion of shallow soil and degradation of the tiger bush vegetation in favor of the bare soil extension (35 km² between 1956 and 2011) as well as increases in drainage density (× 1.5) and in lake area (534 m² in 1956 to 2 x 106 m² in 2011) were the main changes observed. The discharge evolution over time was quantified from changes in lake's volume, computed via a relationship between the lake's surface estimated by remote sensing and in-situ water height data. This relationship was coupled to a water balance equation, taking into account precipitation, water evaporation and lake's bottom infiltration to quantify the water inflow to the lake. The runoff coefficient of the watershed was shown to increase from 0 % in the 1970s to 5.5% in the 2000s. The second part of this thesis was dedicated to hydrological modeling in order to rank the impact of the surface changes highlighted above on runoff. Series of reference and attribution simulations were performed. The increase in bare soil surfaces associated with a decrease in vegetation largely explains the hydrological changes of the watershed since the 1960s. The development of the drainage network and the crusting of sandy dunes play a less important role on this evolution, while the evolution of daily precipitation reduces runoff over time by more than 34%, which contradicts the observed trend. The mechanisms identified in the Agoufou watershed highlight the pivotal role of the dynamics of the coupled vegetation/erosion/drainage network system and their role in other Sahelian regions, where increased runoff was also observed.

The work carried out is based on the thesis properties of clinched joints are determined by the proportions of binding mechanisms form-closure, force-closure and material-closure. To describe the acting binding mechanisms and thus to derive the joint properties, detailed knowledge of the local effect of the individual binding mechanisms is necessary to ensure their targeted adjustment by the joining process. The targeted setting of different proportions of the binding mechanisms is achieved firstly via tool geometry and secondly via surface condition of the joined parts. An introduced form-closure component can be quantified by metallographic cross section with subsequent measurement of the quality-determining parameters such as undercut, penetration depth and neck thickness. To qualify the force-closure component, a torsional load can be applied mechanically at rotationally symmetrical clinch joints. This also allows the influence of different surface conditions on the tribological system to be quantified. Measurement of electrical resistance can reveal the binding mechanisms of force- and material-closure. These investigations are carried out on an aluminum joining part combination of the same type. As a result of these investigations, the clinched joints can be designed according to the load occurring in the later life cycle in the form of an optimum and compromise variant with regard to minimum loads to be transmitted mechanically, electrically with regard to low resistance or manufacturing with minimum energy input.

Ce mémoire s'inscrit dans l'étude du comportement tribologique d'un couple de matériaux ferromagnétique acier XC48 en contact mécanique et magnétique à sec. Le but consiste à identifier les effets liés à la présence ou à l'absence d’un champ magnétique au niveau de l'interface de contact statique et de contact glissant. La première étape a été d'établir des équations de contraintes qui régissent la réponse linéaire, ponctuelle et surfacique des solides sous chargements donnés, en utilisant des modèles développés dans la théorie d'élasticité. Elles ont ensuite été simulées sous Mathématica pour obtenir des résultats analytiques des champs de contraintes en sub-surfaces. Dans la deuxième étape, des essais par contact sec effectués au moyen d'un tribomètre du type pion-disque nous révèlent une augmentation du coefficient de frottement avec le champ magnétique sur le tribocontact. L'analyse en diffraction des rayons X montre que les débris d'usures lors des essais avec champ magnétique comportent la présence d'oxyde de fer. La caractérisation en microscopie électronique à balayage et en profilométrie du matériau usé met en évidence l'état de la sub-surface avec modification de la structure des grains et une présence d'usure douce due aux essais avec champ magnétique. La mesure en photoélasticimétrie montre l'influence du champ magnétique sur les champs de contraintes. En faisant varier les paramètres cinématiques de l'essai sur notre modèle numérique, nous observons une augmentation des champs contraintes. Ces paramètres mécaniques, magnétiques et physico-chimiques sont complexes et l'étude contribue à comprendre ces problématiques liées au frottement sec. / This thesis is about the study of the tribological behavior of a couple of ferromagnetic materials XC48 steel in mechanical and magnetic dry contact. It consists in identifying the generated effects of the presence or absence of a magnetic field at the static and sliding contact interface. The first step was to establish constraint equations which govern the linear, punctual and surface response of the solids under given loadings, by using models developed in the theory of elasticity. They were then simulated under Mathematica to obtain analytical results of stress fields in sub-surfaces. In the second phase, the dry contact tests carried out by means of a standard pin-on-disc tribometer reveal an increase in the coefficient of friction with the magnetic field on the tribological contact. The analysis by X-ray diffraction shows that the wear debris during the tests with magnetic field comprises the presence of iron oxide. The characterization by scanning electron microscopy and profilometry of worn material shows the state of the sub-surface with modification of the grain structure and presence of soft wear from testing with magnetic field. The photoelasticity measurements show the influence of the magnetic field on the stress fields. By varying the kinematic parameters of the test on our numerical model, we observe an increase in stress fields. These mechanical, magnetic and physicochemical parameters are complex and the study contributes to understanding these problems of dry friction.

Various improvements which have been made to the vehicle (reduced engine noise, reducedaerodynamic related NVH), have resulted in tire road noise as the dominant source of thevehicle interior noise. Generally, vehicle interior noise has two main sources, 1) travellinglow frequency excitation below 800 Hz from road surface through a structure- borne pathand 2) the high frequency (above 800 Hz) air-borne noise that is caused by air- pumpingnoise caused by tread pattern.The structure-borne waves of the circumference of the tire are generated by excitation atthe contact patch due to the road surface texture and characteristics. These vibrations arethen transferred from the sidewalls of the tire to the rim and then are transmitted throughthe spindle-wheel interface, resulting in high frequency vibration of vehicle body panels andwindows.The focus of this study is to develop several statistical-based models for analyzing the roadsurface and using them to predict the tire-road noise structure-borne component. In order todo this, a new methodology for sensing the road characteristics, such as asperities and roadsurface condition, were developed using virtual sensing and intelligent tire technology. In ad-dition, the spindle forces were used as an indicator to the structure-borne noise of the vehicle.Several data mining and multivariate analysis-based methods were developed to extractfeatures and to develop an empirical model to predict the power of structure-borne noiseunder different operational and road conditions. Finally, multiple data driven models-basedmodels were developed to classify the road types, and conditions and use them for the noisefrequency spectrum prediction. / Doctor of Philosophy / Multiple data driven models were developed in this study to use the vibration of the tirecontact patch as an input to sense some characteristics of road such as asperity, surface type,and the surface condition, and use them to predict the structure-borne noise power. Also,instead of measuring the noise using microphones, forces at wheel spindle were measuredas a metric for the noise power. In other words, a statistical model was developed that bysensing the road, and using the data along with other inputs, one can predict forces at thewheel spindle.

This master thesis deals with the pavement management system as a tool for a management and maintenance of the roads in the Liberec region. The aim is to collect road failures within the network pavement management system level on roads of 2nd and 3rd class. The resulting data will be used for evaluate pavement condition and make plans of pavement maintenance and rehabilitation in variants. Furthermore, the thesis deals with individual variants in the process of data evaluation when evaluating their suitability and accuracy. The theoretical part summarises the information needed to understand the functioning of the road management system, as well as a description of the software used to collect and subsequent work with the data. In the practical part are presented results of the thesis and moreover the questions arising from the goals set are answered.