Arbeitswissenschaftliche digitale Menschmodelle werden als Werkzeuge virtueller Ergonomie zur Gestaltung menschengerechter Produkte und Arbeitsplätze genutzt. Der bislang nur qualitativ beschriebene Praxiseinsatz wird durch theoretische Analysen und eine empirische Studie systematisiert und darauf aufbauend werden die Schwachstellen der Systeme erörtert. Ein wesentlicher Ansatzpunkt für Weiterentwicklungen ist die Erarbeitung ergonomischer Bewertungsverfahren bzw. -modelle, insbesondere für Belastungen aufgrund von Bewegungen. Digitale Menschmodelle bieten das Potenzial, aus simulierten Bewegungsdaten und den damit zusammenhängenden Belastungen eine Bewertung der Arbeitsvorgänge zu generieren. In dieser Arbeit wird daher ein neues arbeitswissenschaftliches Bewertungsmodell für muskuläre Beanspruchungen erforscht, d.h. methodisch hergeleitet und evaluiert. Dazu ist ein Versuchsstand zur Standardisierung und Belastungserzeugung notwendig. In der darauffolgenden Laborstudie werden die Belastungsparameter statischer Momentanteil, Winkelgeschwindigkeit und Momentrichtung variiert und die daraus entstehende Veränderung der muskulären Beanspruchung von Probanden erforscht. Ein dafür benötigtes, neues Verfahren zur Normalisierung wird vorgestellt. Die Laborstudie zeigt, dass der statische Momentanteil linear steigend mit der Arbeitsbeanspruchung zusammenhängt. Die durchschnittliche Winkelgeschwindigkeit beeinflusst die Arbeitsbeanspruchung je nach Muskeltyp entweder linear steigend oder ohne Zusammenhang. / Digital human models for human factors are used as tools for virtual ergonomics and the design of products and workplaces. In this work the use of the systems is analysed with theoretical models and an empirical study. Therefore, disadvantages of the systems are identified. A main idea for further developments is the research on ergonomic approaches and models, especially for movements and the strain caused by movements. Digital human models are capable to assess work processes based on data from simulations. In this work a new human factors orientated rating model for muscular strains is developed and evaluated. A test stand generates and standardizes the stress. In a laboratory survey the stress parameters are analysed. The variation of the static torque part, the angular velocity and the torque direction cause changes in the muscular strains. Hence, these muscular strains are measured electromyographically. A new normalisation method, the normalized standard movement, is introduced. The survey shows the existence of a correlation of static torque part and work strain. Depending on the muscle type, the angular velocity either affects the work strain linear increasing or does not affect it.

This thesis reports on experimental investigations of the mechanisms inherent in the joint action of short and continuous fibres in high-performance, cement-based composites. Experiments on different levels of observation (macro- meso- and micro-levels) were performed to provide detailed insights into the various effects of adding different types of short fibres (dispersed AR glass, integral AR glass and dispersed carbon fibres) on the strength, deformation, and failure behaviour of textile-reinforced concrete (TRC) subjected to tensile loading. Moreover, visual inspections of the specimens' surfaces and microscopic investigation of the fracture surfaces and the interface zone between fibre and matrix were performed and evaluated. Subsequently, the mathematical descriptions for TRC with short fibres under deformation controlled tensile loading conditions were derived based on a multi-scale rheological-statistical modelling approach. Based on a literature review, the state of the art is presented and discussed to identify key questions that are yet to be answered satisfactorily. This provides the starting point for the investigations presented in this thesis. The experimental program on the macro-level included uniaxial tension tests performed on thin, narrow plates reinforced by: a) only textile reinforcement, b) only short fibres, and c) hybrid reinforcement (both textile reinforcement with the addition of short fibres). Special attention was directed toward the course of the stress-strain relationship, crack pattern development, and fibre failure behaviour. The stress-strain curves resulting from uniaxial tension testing demonstrated clearly the positive influence of all types of short fibre on the mechanical performance of TRC. While the first-crack stress in TRC specimens increased significantly due to the addition of short fibres, an expansion of the strain region, where multiple cracks form, was observed for the stress-strain curves for TRC with added short fibres. The visual inspection of the specimens\' surfaces showed a higher number of cracks and finer crack patterns for given strain levels in the cases when short fibres were added to TRC. Moreover, depending on fibre type, the positive effects of the addition of short fibres on both tensile strength and work-to-fracture of the composite were found to vary significantly. The findings at the micro- and meso-levels of observation provided to a great extent a core of understanding of some particular mechanical behavioural properties of TRC with short fibres at the macro-level of observation. Thus, in addition to the experimental testing performed on composite materials with different parameter combinations, investigations of the action of individual material components, i.e., multifilament-yarns and single short fibres, embedded into cement-based matrices were carried out. It was found that short fibres indeed improve the bond between multifilament-yarns and the surrounding matrix. By their random positioning on the yarn\'s surface, short fibres built new adhesive cross-links which provided extra connecting points to the surrounding matrix. Furthermore, the water-to-binder ratio of the matrix influenced bond quality between fibre and matrix, i.e., various degrees of matrix-fibre bond were observed. As a result, the mechanical behaviour of the composite varied with w/b: While the good bond of the fibre embedded in a matrix with a low water-to-binder ratio leads to increase in stiffness and strength of the composite, fibres with weak bonding can be considered as defects with respect to stiffness as they lead to a decrease in the value. The thesis further derives the mathematical relationships for TRC with the addition of short fibres under deformation-controlled tensile loading. A physically based rheological model consisting of simple rheological elements was developed based on the experimental results on the micro-scale, using single-fibre pullout tests. Special attention was paid to the gradual de-bonding process and the resulting force-displacement branch. The model adequately reproduced both relevant fibre failure scenarios: fibre fracture and fibre pullout. By means of statistical procedures the combination of these models led to description of the stress-crack opening behaviour of an individual crack bridged by the given number of short fibres. The stress-strain relation for TRC with short fibres subjected to tensile loading was then derived. The concept followed at the macro-level of observation was modelling separately the three main regions of the characteristic stress-strain curve. The regions of crack-free material and crack-widening were considered linear and described based on the corresponding characteristic values of each region. The behaviour of the multiple cracking region was derived by considering an increasing number of cracks in serial interconnection and the contribution of the uncracked matrix in between. The stress transfer, i.e., bridging stress, across the crack was determined based on the contribution of both short fibres and multifilament-yarns. Behaviour of individual cracks was adjusted by varying the number of bridging fibres in different cracks and by varying the yarn bridging stress according to range observed in the pullout experiments. / In der vorliegenden Arbeit wird über Untersuchungen zu den Mechanismen der Wechselwirkungen zwischen Kurz- und Endlosfasern in zement-basierenten Hochleistungskompositen berichtet. Hierzu wurden experimentelle Untersuchungen auf verschiedenen Betrachtungsebenen (Makro-, Meso- und Mikroebene) durchgeführt mit dem Ziel, detaillierte Erkenntnisse zu den Auswirkungen der Zugabe von verschiedenen Arten von Kurzfasern (disperse und integrale AR-Glasfasern, Kohlenstofffasern) hinsichtlich des Festigkeits-, Verformungs- und Bruchverhaltens von Textilbeton (engl.: textile-reinforced concrete = TRC) unter Zugbeanspruchung zu gewinnen. Die Bruchflächen sowie die Gestalt der Interphase zwischen der Bewehrung aus Textilien oder Kurzfasern und der umhüllenden zemengebundenen Matrix wurden mit optischen und elektronenmikroskopischen Verfahren hinsichtlich der Wechselwirkungsphänomene ausgewertet. Die Ergebnisse der experimentellen Arbeiten bildeten den Ausgangspunkt für die mathematischen Beschreibungen für TRC mit Kurzfasern unter verformungsgesteuerter Zugbelastung. Die Formulierungen erfolgten auf Grundlage multiskalarer rheologisch-statistischer Modellansätze. In einer Literatursichtung wurde zunächst der Kenntnisstand zu den Materialien und zum Verhalten von TRC und Faserbeton unter Zugbeanspruchung dargestellt und diskutiert. Die noch zu erforschenden Fragen wurden präzisiert und die Grundlagen für deren Untersuchung geschaffen. Bei den Experimenten auf der Makroebene wurden drei Bewehrungsvarianten betrachtet: a) textile Bewehrung, b) Kurzfaserbewehrung, und c) hybride Bewehrung (Textil und Kurzfasern). An Dehnkörpern wurde die Spannungs-Dehnungsbeziehung unter einachsiger Zugbelastung studiert und dabei das Rissbild und die Phänomene des Faserversagens detailliert beobachtet. Anhand der Spannungs-Dehnungsbeziehungen konnte gezeigt werden, dass die Zugabe von Kurzfasern bei allen untersuchten Kurzfaserarten zu einer erheblichen Verbesserung der Leistungsfähigkeit von Textilbeton führt. Dies zeigte sich unter anderem in einer ausgeprägten Anhebung der Erstrissspannung sowie der Entwicklung von zahlreicheren und damit feineren Rissen, die zu einer Verbesserung der Duktilität führten. Ebenso wurden Steigerungen der Zugfestigkeit und der Energiedissipation festgestellt. In welchem Maß diese Änderungen stattfinden, hängt von der Art der Kurzfasern ab. Die Experimente auf der Mikro- und Mesoebene wurden so konzipiert, dass sie die Erkundung der Mechanismen, die den auf der Makroebene beobachteten Phänomenen zugrunde liegen, unterstützten. Auf der Mesoebene wurden Mulitifilamentgarnauszugversuche (mit und ohne Kurzfasern in der Matrix) und auf der Mikroebene Einzelfaserauszugsversuche für alle betrachteten Kurzfasertypen durchgeführt. Es wurde festgestellt, dass die Kurzfasern den Verbund zwischen Matrix und Multifilamentgarn verbessern. Kurzfasern können bei zufälliger Positionierung an der Garnoberfläche zusätzliche Haftbrücken bzw. Verbindungsstellen zu umgebender Matrix bilden. Für die Verbundqualität zwischen Faser und Matrix ist der Wasser-Bindemittel-Wert (W/B-Wert) von entscheidender Bedeutung. Bei einer Matrix mit niedrigem W/B-Wert führt die gute Qualität des Verbunds der eingebetteten Fasern zu einer Erhöhung der Steifigkeit sowie der Festigkeit des Komposites. Bei hohem W/B-Wert haben die Fasern einen schlechten Verbund zur Matrix und müssen überwiegend als Fehl- bzw. Schwachstellen betrachtet werden. Festigkeit und Steifigkeit des Komposits nehmen daher ab. Die Ableitung mathematischer Beziehungen für Textilbeton mit Zugabe von Kurzfasern unter verformungsgesteuerter Zugbelastung erfolgte aufbauend auf den Ergebnissen der experimentellen Untersuchungen auf der Mikroebene. Die Einzelfaserauszugsversuche wurden mit Hilfe eines physikalisch basierten Modelles nachgebildet, das aus einfachen rheologischen Elementen besteht. Phänomene wie die graduelle Ablösung der Faser, Faserbruch und Faserauszug wurden durch eine entsprechende Kombination und Parametrierung der rheologischen Elemente abgebildet. Im Ergebnis wurden zutreffende Kraft-Rissöffnungsbeziehungen modelliert. Auf der Mesoebene wurde ein einzelner Riss modelliert, der sowohl durch Multifilamentgarne als auch Kurzfasern überbrückt werden kann. Der rissüberbrückenden Wirkung der zahlreichen Kurzfasern wurde mit Hilfe statistischer Methoden rechnung getragen, die unterschiedliche Faser-Risswinkel und Einbindelängen berücksichtigen. Die resultierende Spannungs-Rissöffnungskurve umfasst die rissüberbrückende Wirkung von Multifilamentgarnen und Kurzfasern. Auf der Makroebene kann die charakteristische Spannungs-Dehnungsbeziehung von TRC unter Zugbelastung in 3 Bereiche (Zustände I, IIa, IIb) unterteilt werden. Die Kurvenverläufe im Zustand I (ungerissenen) sowie Zustand IIb (abgeschlossenes Rissbild) wurden als linear betrachtet und basierend auf den entsprechenden charakteristischen Werten des jeweiligen Zustands beschrieben. Das Verhalten im Zustand IIa (multiple Rissbildung) wurde durch die Reihenschaltung einer zunehmenden Anzahl von Rissen sowie den Beitrags der ungerissenen Matrix zwischen den Rissen modelliert.

The desire for energy and resource savings brings magnesium alloys as lightweight materials with high specific strength more and more into the focus. Most structural components are subjected to cyclic loading. In the course of computer aided product development, a numerical prediction of the fatigue life under these conditions must be provided. For this reason, the mechanical properties of the considered material must be examined in detail. Wrought magnesium semifinished products, e.g. magnesium sheet metals, typically reveal strong basal textures and thus, the mechanical behavior considerably differs from that of the well-established magnesium die castings. Magnesium sheet metals reveal a distinct difference in the tensile and compressive yield stress, leading to non-symmetric sigmoidal hysteresis loops within the elasto-plastic load range. These unusual hysteresis shapes are caused by cyclic twinning and detwinning. Furthermore, wrought magnesium alloys reveal pseudoelastic behavior, leading to nonlinear unloading curves. Another interesting effect is the formation of local twin bands during compressive loading. Nevertheless, only little information can be found on the numerical fatigue analysis of wrought magnesium alloys up to now. The aim of this thesis is the investigation of the mechanical properties of wrought magnesium alloys and the development of an appropriate fatigue model. For this purpose, twin roll cast AM50 as well as AZ31B sheet metals and extruded ME21 sheet metals were used. Mechanical tests were carried out to present a comprehensive overview of the quasi-static and cyclic material behavior. The microstructure was captured on sheet metals before and after loading to evaluate the correlation between the microstructure, the texture, and the mechanical properties. Stress- and strain-controlled loading ratios and strain-controlled experiments with variable amplitudes were performed. Tests were carried out along and transverse to the manufacturing direction to consider the influence of the anisotropy. Special focus was given to sigmoidal hysteresis loops and their influence on the fatigue life. A detailed numerical description of hysteresis loops is necessary for numerical fatigue analyses. For this, a one-dimensional phenomenological model was developed for elasto-plastic strain-controlled constant and variable amplitude loading. This model consists of a three-component equation, which considers elastic, plastic, and pseudoelastic strain components. Considering different magnesium alloys, good correlation is reached between numerically and experimentally determined hysteresis loops by means of different constant and variable amplitude load-time functions. For a numerical fatigue life analysis, an energy based fatigue parameter has been developed. It is denoted by “combined strain energy density per cycle” and consists of a summation of the plastic strain energy density per cycle and the 25 % weighted tensile elastic strain energy density per cycle. The weighting represents the material specific mean stress sensitivity. Applying the energy based fatigue parameter on modeled hysteresis loops, the fatigue life is predicted adequately for constant and variable amplitude loading including mean strain and mean stress effects. The combined strain energy density per cycle achieves significantly better results in comparison to conventional fatigue models such as the Smith-Watson-Topper model. The developed phenomenological model in combination with the combined strain energy density per cycle is able to carry out numerical fatigue life analyses on magnesium sheet metals.

This thesis deals with problems of biomechanics of soft tissues, namely of stress-strain analysis of abdominal aortic aneurysm (AAA). The introduction describes briefly the possibility of aneurysm occurrence with a focus on an aneurysm in the abdominal aorta.

Im Rahmen dieser Arbeit wird ein physikalisches Modell für weichelastische EVA-Schaumstoffe entwickelt, das das mechanische Verformungsverhalten (Spannungs-Verformungs-Kurve) bei der Interaktion zwischen Sportler und Sportgerät am Beispiel eines Laufschuhs anwendungsgerecht – d.h. bei hoher Verformung und Belastungsgeschwindigkeit – kennzeichnet. Im Stand der Technik werden als Einflussfaktoren auf das mechanische Verformungsverhalten von Weichschäumen die Parameter Schaumdichte, Zellgröße bzw. Zelldurchmesser, Schaumhärte und Verformungsgeschwindigkeit ermittelt. Diese werden für die vorliegenden vier Versuchsmaterialien analysiert, wobei die letzten zwei Parameter im Modell Berücksichtigung finden. Das Modell setzt sich aus einem Matrix- und einem Gasphasenanteil zusammen. Der Matrixphasenanteil wird experimentell bei der jeweiligen Verformungsgeschwindigkeit bestimmt, wohingegen der Gasphasenanteil der in den Zellen komprimierten Luft auf einem physikalischen Zusammenhang beruht und anhand der gemessenen Schaumhärte und des Atmosphärendrucks bei der jeweiligen Verformung berechnet wird. Die Voraussetzungen für die Verwendung des Modells, zu denen inkompressible Matrixphase, Geschlossenzelligkeit und keine Querausdehnung des Schaums zählen, werden vorab umfangreich geprüft. Zusammenfassend lässt sich aussagen, dass das gewählte Modell eine gute Übereinstimmung mit den experimentell bestimmten Ergebnissen erzielt. Dies wird anhand der Mittelwertes der Differenz von experimentell ermittelten zu modellierten Daten bestimmt, für den ein Wert von 7 % berechnet wird. / The purpose of this doctoral thesis is developing a physical model for flexible foam materials (e.g. ethylene/vinyl acetate foam) characterizing the mechanical deformation behavior (stress-strain-curve) at the interaction between athlete and sports equipment (e.g. running footwear) during high deformation and high loading rate. Previous studies described various parameters influencing the mechanical deformation behavior of flexible foams: foam density, cell size / cell diameter, foam hardness and loading rate. These parameters are being analyzed for the four present foams whereof the last two parameters were considered in the model. The model consists of a matrix phase measured experimentally at required loading rate multiplied with a correction factor and a gas phase of the air compressed in the foam cells which is calculated by atmospheric pressure and foam hardness. The requirements (incompressible matrix phase, closed cells and zero Poisson ratio) for using the model are verified first of all. In conclusion, the developed model presents a good accordance with the experimental data calculated by a mean difference between experimental and modeled data of 7 %.

A major concern for geotechnical engineers is the ability to predict how a soil will react to large ground motions produced by earthquakes. Of all the different types of soil, liquefiable soils present some of the greatest challenges. The ability to quantify the degradation of a soil's shear modulus as it undergoes liquefaction would help engineers design more reliably and economically. This thesis uses ground motions recorded by an array of downhole accelerometers on Port Island, Japan, during the 1995 Kobe Earthquake, to quantify the shear modulus of sand as it liquefies. It has been shown that the shear modulus of sand decreases significantly as it liquefies, apparently decreasing in proportion to the increasing excess pore water pressure ratio (Ru). When completely liquefied, the shear modulus of sand (Ru = 1.0) for a relative density of 40 to 50% is approximately 15% of the high-strain modulus of the sand in its non-liquefied state, or 1% of its initial low-strain value. Presented in this thesis is an approach to modeling the shear modulus degradation of sand as it liquefies. This approach, called the "degrading shear modulus backbone curve method" reasonably predicts the hysteretic shear stress behavior of the liquefied sand. The shear stresses and ground accelerations computed using this method reasonably matches those recorded at the Port Island Downhole Array (PIDA) site. The degrading shear modulus backbone method is recommended as a possible method for conducting ground response analyses at sites with potentially liquefiable soils.

Presented work deals with Biomechanical study of the facial skeleton. This work is focused on the fixation of the mandible after removal of a tumor from affected bone tissue. The aim of the work is to perform biomechanical study of the facial skeleton with subsequent detailed stress strain analysis of two mandible implants designed and manufactured for specific patients. The geometry model of mandible used for design of mandible implants and used for computational modelling has been obtained on the basis of CT data of two patients. A Theoretical-Clinical sub-study that deals with the comparison the CT data processing which is necessary for creating the model of geometry is a part of the thesis. Two models of mandible with applied mandible implant have been created for two specific patients with tumorous mandible bone tissue. Stress strain analysis has been performed for these two models. Results of the stress strain analysis of two models of mandibles with mandible implants are presented in the final chapters of the thesis. Findings of the biomechanical study have been published and applied in clinical practice.

Die vorliegende Arbeit beschäftigt sich mit einer Methode zur Bestimmung von realistischeren Steifemoduln für eine genauere Setzungsprognose von Flachgründungen in sehr „laborfeindlichen“ veränderlich festen Gesteinen. Die vergleichenden Laboruntersuchungen an teilverwitterten Keuperböden ergaben, dass die Steifemoduln aus den K0-Triaxialversuchen um den Faktor zwei bis drei größer sind als die Moduln aus den Standardoedometerversuchen. Durch, sowohl analytische, wie auch numerische, Nachrechnungen der durchgeführten Feldversuche und der Setzungsmessungen konnte nachgewiesen werden, dass mit Moduln aus K0-Triaxialversuchen deutlich zutreffendere Setzungsprognosen im Keuper möglich sind, als mit Moduln aus den Oedometerversuchen. Es konnte eine deutliche Abhängigkeit der Entwicklung des Steifemoduls von der Belastungsgeschichte, insbesondere im Übergangsbereich von der „echten“ Wiederbelastung zur Erstbelastung, gefunden werden. Für grobe Näherungen, z.B. für Vorbemessungen, werden Abhängigkeiten zwischen Auflastspannungen und Steifemoduln für die Erst- und für die Wiederbelastung angegeben. So lassen sich Moduln für beliebige Spannungen direkt abschätzen. Aus den abgeleiteten Moduluszahlen m des untersuchten Spannungs-Verformungsverhaltens von Böden, können, insbesondere unter Einbeziehung von Daten aus der internationalen Literatur, Korrelationsgleichungen in Abhängigkeit von Anfangsporenzahl bzw. Anfangsporenanteil mit guten bis sehr guten Regressionen angegeben werden. Da der Steifeexponent a nur geringfügig vom Anfangsporenanteil n abhängt und an den in dieser Arbeit untersuchten Böden weder sinnvolle Korrelationen mit R > 0,8 zwischen a und n, noch Abhängigkeiten von a zur Korngröße gefunden wurden, werden für die Steifeexponenten Mittelwerte angegeben.

The compression behavior of a newly developed near eutectic Al-Si based cast alloy with three different microstructures has been investigated in the present work. Microstructures with modified and unmodified Si particles and matrix with different tempers are investigated. The main objective of this work is to understand the effect of heat treatment and modification on the fracture behavior of the alloy under compression. This alloy is subjected to compressive loading at different strain rates and temperatures during the operation of the engines. Hence, the effect of strain rates and temperatures is also considered. The compression tests are carried out at different strain rates from quasi-static to dynamic viz., 3*10-4 to 102/s and three different temperatures RT, 100°C and 200°C. Microstructure of the alloys studied predominantly consists of eutectic colonies of α-Al and Si with a few interspersed α-Al dendrites. Modified alloy has more globular Si particles than unmodified alloy. Heat treated alloys are found to have hardening precipitates S’ & Al7Cu4Ni and 3-7 atomic layer thick zones, which may be precursors to S’ phase. A variety of large intermetallics, viz., plate like particles Al4.5FeSi, Chinese script like particles Al19Fe4MnSi2 and bulky phase Al3NiCu are also observed in the alloys. Mechanical behavior of the alloys is found to be different for different microstructures. Modification improves strength and ductility. Heat treatment improves strength of the alloy at the expense of ductility. A transition in mechanical behavior is observed after a particular strain rate for all the alloys studied. This transition strain rate is dependent on heat treatment, Si particle size and temperature. This transition can be explained on the basis of dislocation-precipitate and dislocation-Si particle interactions. Work hardening behavior of the alloys depends on the matrix microstructure in the unmodified alloys, and both matrix and particles play a role in the modified alloy. A statistically robust quantitative micro structural analysis has been carried out after compressing the samples at various strain rates and temperatures. The unique contribution of this work is the understanding of combined effect of strain rate and temperature on Si particle fracture characteristics in the alloy with different microstructures. From the fracture characteristics of Si particles, it is concluded that both dislocation pile-up mechanism and fibre loading are responsible for particle fracture in the modified alloy, whereas the fibre loading mechanism alone is sufficient to explain the particle fracture characteristics in the unmodified alloy. Si particles in the modified condition are found to cleave along the lowest surface energy planes {112} & {110} and the particles with orientations {112} & {111} are more prone to fracture. In addition to Si particle fracture, elongated Fe rich intermetallic particles are also seen to show peculiar fracture behavior. The Al4.5FeSi intermetallics with (100) as the plane of the plate cleave along (100) planes. This is a novel finding in this work and could have immense implications on the role of Fe impurities in the fracture behavior of these alloys. Moreover, since these cleavage fractures are seen to be more than 200 microns in size (which implies that the real penny shaped crack would be even larger) their role cannot be assumed to be negligible, as was previously thought. The load sharing between the Al matrix and eutectic Si particles are simulated by microstructure based finite element modeling. The program OOF (Object-Oriented Finite element analysis) is used to generate the finite element meshes for real microstructures with different Si morphology. The experimentally obtained stress – strain properties of the alloy is given as an input to describe the plastic behavior of the Al matrix, in the finite element simulation. This analysis helps to understand the effect of particle size, shape, orientation & clustering and matrix temper on the stress transferred to the Si particles. Combination of Electron Back-Scattered Diffraction (EBSD) and frequency shift, polarized micro-Raman technique is applied to validate the stress states in Si particles with {111} orientations. The stress at fracture of Si particles is also estimated from Raman technique. Even though the alloys with different microstructures show different mechanical behavior, the sequence of fracture mechanisms is found to be same for all the alloys. The failure occurs in three stages: cracking of Si particles at low strains, micro-crack formation along the fractured particles, micro-crack coalescence and propagation leading to final failure. Thus, the proposed analysis links various deformation mechanisms ranging from nano precipitate-dislocation interactions to micro short-fiber theory of load sharing by eutectic silicon along with coupled effect of strain rate and temperature. In addition, negative strain rate sensitivity is also observed in the lower strain rate regimes (3*10-4, 10-3& 102/s) at RT and 100°C for all the three alloys, and serrated flow is also observed in the same strain rate and temperature regimes. Some of the features of serrated flow can be explained by the dynamic strain aging model and some other features by precipitate shearing.

Presented work deals with Biomechanical study of the facial skeleton. This work is focused on the fixation of the mandible after removal of a tumor from affected bone tissue. The aim of the work is to perform biomechanical study of the facial skeleton with subsequent detailed stress strain analysis of two mandible implants designed and manufactured for specific patients. The geometry model of mandible used for design of mandible implants and used for computational modelling has been obtained on the basis of CT data of two patients. A Theoretical-Clinical sub-study that deals with the comparison the CT data processing which is necessary for creating the model of geometry is a part of the thesis. Two models of mandible with applied mandible implant have been created for two specific patients with tumorous mandible bone tissue. Stress strain analysis has been performed for these two models. Results of the stress strain analysis of two models of mandibles with mandible implants are presented in the final chapters of the thesis. Findings of the biomechanical study have been published and applied in clinical practice.