The need to produce lighter components due to environmental aspects and the development of electrical vehicles represents an opportunity for cast aluminium-silicon alloys. With high specific strength, good castability, high corrosion resistance and recyclability, these alloys offer an attractive combination of properties as an alternative to steel, cast iron and titanium-based components in certain applications. To take advantage of such a combination of properties, there is a need to ensure that they can be reliably achieved. In other words, high performing components need to be produced. For that, the production cycle, from alloy selection and melt preparation, to the casting and heat treatment of the component must be understood and controlled as a whole. The different steps in the production cycle will affect the microstructure of the components and hence the resulting mechanical properties. Understanding the relation between the different steps in the production cycle, its consequences on the microstructural features and on the mechanical properties constitutes the aim of this thesis. Experiments applying state-of-the-art knowledge regarding effect of casting process, alloying system and post-process variables were performed aimed at achieving properties similar to those of high pressure die casting (HPDC) components. Different melt quality determination tools were evaluated on three different EN AC-46000 melt qualities. The influence of modification, grain refinement and both treatments together was assessed on an Al-10Si alloy solidified under different cooling rates. The tensile behaviour and the impact of features such as secondary dendrite arm spacing (SDAS) or grain sizes was quantified. It was corroborated that by appropriate selection and control of such alloying system, process and post-process variables it is possible to achieve HPDC EN AC-46000 tensile and fatigue properties through a T5 treated sand cast EN AC-42100 alloy. On the other hand, the available techniques for melt quality assessment are inadequate, requiring further analysis to successfully identify the melt quality. Additionally, it was observed that decreasing the melt quality by additions of 25 wt.% of machining chips did not significantly decrease the tensile properties but slightly increased the variation in them. In relation to the modification and grain refinement of Al-10Si alloys it was concluded that with the slowest cooling rate tested, additions of only grain refiner did not successfully produce equiaxed grains. For cooling rates corresponding to dendrite arm spacings of 15 μm and slower, combined additions of grain refiner and modifier can lead to higher tensile properties compared to the corresponding separate additions. SDAS was observed to describe flow stress through the Hall-Petch equation but grain size did not show a physically meaningful relationship. Furthermore, beginning of cracking was detected in the plastic deformation region at dendrite/eutectic boundaries and propagated in a trans-granular fashion.

The effect of hydrogen charging current density and tensile strain rate on the mechanical properties of X80 pipeline steel were investigated by slow strain rate test (SSRT), Charpy impact test, and scanning electron microscopy (SEM) in this thesis. The results show that both the ultimate tensile strength and elongation to failure of X80 steel were deteriorated significantly after charging with hydrogen. With a strain rate of 5 x 10-5 s-1, the relative tensile strength and plasticity loss of X80 steel had no significant change within the range of assumed hydrogen partial pressures at room temperature. At room temperature, X80 steel had no apparent variation in ultimate tensile strength and elongation, except at the strain rate of 10-6 s-1. Specimens obtained the greatest relative tensile strength loss and plasticity loss when strained at 10-6 s-1 with a current density of 4.6 mA/cm2. The fracture morphology of two test groups of X80 steel exhibited significant brittle rupture when tested with dynamic hydrogen charging. The impact energy of X80 was not affected by hydrogen charging. Different current density also had no influence on the results of the impact test.

Advances in biomaterials have enabled medical practitioners to replace diseased body parts or to assist in the healing process. In situations where a permanent biomaterial implant is used for a temporary application, additional surgeries are required to remove these implants once the healing process is complete, which increases medical costs and patient morbidity. Bio-absorbable materials dissolve and are metabolized by the body after the healing process is complete thereby negating additional surgeries for removal of implants. Magnesium alloys as novel bio-absorbable biomaterials, have attracted great attention recently because of their good mechanical properties, biocompatibility and corrosion rate in physiological environments. However, usage of Mg as biodegradable implant has been limited by its poor corrosion resistance in the physiological solutions. An optimal biodegradable implant must initially have slow degradation to ensure total mechanical integrity then degrade over time as the tissue heals. The current research focuses on surface modification of Mg alloy (MZC) by surface treatment and polymer coating in an effort to enhance the corrosion rate and biocompatibility. It is envisaged that the results obtained from this investigation would provide the academic community with insights for the utilization of bio-absorbable implants particularly for patients suffering from atherosclerosis. The alloying elements used in this study are zinc and calcium both of which are essential minerals in the human metabolic and healing processes. A hydrophobic biodegradable co-polymer, polyglycolic-co-caprolactone (PGCL), was used to coat the surface treated MZC to retard the initial degradation rate. Two surface treatments were selected: (a) acid etching and (b) anodization to produce different surface morphologies, roughness, surface energy, chemistry and hydrophobicity that are pivotal for PGCL adhesion onto the MZC. Additionally, analyses of biodegradation, biocompatibility, and mechanical integrity were performed in order to investigate the optimum surface modification process, suitable for biomaterial implants. The study concluded that anodization created better adhesion between the MZC and PGCL coating. Furthermore, PGCL coated anodized MZC exhibited lower corrosion rate, good mechanical integrity, and better biocompatibility as compared with acid etched.

The ductile fracture process, which consists of the nucleation, growth and coalescence of microvoids, was extensively studied for materials deforming homogeneously. For materials with a non-homogeneous deformation behavior, such as those having hexagonal closed packed (HCP) crystal structure, experimental and numerical data is lacking. Therefore, the fracture properties of materials with such HCP structure, like titanium (used in aerospace and biomedical applications), zirconium (nuclear industry) and magnesium (manufacturing industry) are not well understood. The main research objective of this Ph.D. thesis is to better understand the mechanisms governing fracture in commercially pure (CP) titanium. In particular, the effect of grain orientation on void growth is investigated. The fracture process of CP titanium was visualized in model materials containing artificial holes. These model materials were fabricated using a femtosecond laser coupled with a diffusion bonding technique to obtain voids in the interior of titanium samples. Diffusion bonding was carried out either above or below the phase transformation temperature resulting in different microstructures. Changes in void dimensions during in-situ straining were recorded in three dimensions using x-ray computed tomography. Void growth obtained experimentally was compared with the Rice and Tracey model which predicted well the average void growth. However, a large scatter in void growth was observed experimentally and was explained in terms of differences in grain orientation which was confirmed by crystal plasticity simulations. It was also shown that grain orientation has a stronger effect on void growth than intervoid spacing and material strength. Intervoid spacing, however, appears to control whether the intervoid ligament failure is ductile or brittle. While this study showed a good agreement between experiments and simulations on average, there is no direct void growth comparison for particular grain orientations. In a follow-up study, an experimental approach was developed to directly relate the growth of a void to its underlying grain orientation. This is achieved by first annealing CP titanium samples below the α-β phase transformation temperature, then performing electron backscatter diffraction iii (EBSD) and finally diffusion bonding the samples together. Samples were then tested in x-ray tomography. This study showed the importance of the local state of strain on void growth. Crystal plasticity simulations that take into account the particular grain orientation and the local state of strain were found to predict well experimental void growth. Crystal plasticity simulations confirmed that the orientation of the voidcontaining grain is more important than the orientation of surrounding grains and more important than the volume fraction of voids, in order to determine void growth. This thesis on the growth and coalescence of voids is important to validate and improve the predictions of ductile fracture models and to design new materials with improved fracture properties.

Les procédés de mise en forme des tôles métalliques sont largement utilisés dans l’industrie mécanique. La simulation numérique des opérations de mise en forme nécessite une caractérisation précise des modèles de comportement rhéologique des matériaux. Dans de nombreuses opérations de mise en forme des tôles métalliques telle que l’emboutissage, l’hydroformage, …, de grandes déformations et des vitesses de déformations dites intermédiaires peuvent être atteintes sous des états biaxiaux de déformation ou de contrainte. L’objectif de ce travail est de montrer le potentiel de l’essai de traction bi-axiale pour caractériser l’écrouissage des tôles métalliques pour de grandes déformations et dans une gamme de vitesse de déformation dite intermédiaire. A partir de simulations numériques, une forme optimale d’éprouvette en croix, permettant d’atteindre 30% de déformation plastique équivalente dans la zone centrale de l’éprouvette sous un chargement équibiaxial, a été proposée. Par la suite, des essais quasi-statiques et dynamiques de traction bi-axiale ont été réalisés sur la forme d’éprouvette proposée à partir d’une machine dédiée d’essais servo-hydraulique à quatre vérins. Dans un premier temps, le matériau choisi est un alliage d’aluminium AA5086 ne présentant pas de dépendance à la vitesse de déformation. Les déformations expérimentales sont déterminées à partir de la technique de corrélation d’images. L’écrouissage isotrope de différents modèles est identifié à partir d’une procédure inverse basée sur une modélisation éléments finis de l’essai de traction biaxiale. Trois critères de plasticité (Mises, Hill 48 et Bron et Besson) ont été successivement utilisés pour l’identification des paramètres des lois d’écrouissage. Les résultats obtenus montrent d’une part que la modélisation est très sensible au critère de plasticité choisi, et d’autre part que le critère de Bron et Besson permet d’obtenir une très bonne corrélation entre les courbes d’écrouissage identifiées à partir de l’essai bi-axial et de l’essai uni-axial. Pour les tests dynamiques bi-axiaux, les phénomènes de résonance du dispositif mécanique, générés à l’impact initial de début d’essai et matérialisés par de fortes oscillations du signal d’effort, sont atténués par l’interposition d’un élément en élastomère dans le système d’ancrage de chaque bras de l’éprouvette. Pour finir, la méthodologie d’identification proposée est appliquée à la caractérisation du comportement viscoplastique d’un acier dual phase DP600. Les courbes d’écrouissage identifiées à partir des essais bi-axiaux ont été comparées à celles obtenues par des essais uni-axiaux pour une gamme de vitesse de déformation allant de 10- 3s-1 à 101s-1. Le DP600 présente une même sensibilité à la vitesse de déformation quelque soit la sollicitation, uni-axiale ou bi-axiale. Les lois d’écrouissage de Ludwick et de Voce, identifiées jusqu’à 30% de déformation plastique équivalente sur la base de données expérimentales constituées des essais bi-axiaux, sont relativement proches. Les différences observées entre ces courbes d’écrouissage et celles identifiées à partir des essais de traction uni-axiaux montrent tout l’intérêt de l’essai de traction bi-axiale sur éprouvette en croix. / Sheet metal forming processes are widely adopted to produce panels, tubes, profiled parts in manufacturing industry. The numerical simulation of the forming processes requires accurate constitutive models of material. In many sheet metal working operations such as stamping, hydroforming, …, large strains and intermediate strain rates can be reached under biaxial strain or stress states. The objective of this work is to show the potential of the biaxial in-plane tensile test to characterize the hardening behaviour of metal sheets up to large strain levels. By numerical investigation, an optimal cruciform shape is designed to obtain large equivalent plastic strain, up to 30%, at the central zone under equi-biaxial strain path. As expected, the initial cracks of tested specimens are always observed at the central zone. Then, quasi-static and dynamic biaxial tensile tests on in-plane cross specimens have been performed on a dedicated servo-hydraulic machine. These biaxial tensile tests have been carried out on aluminium alloy AA5086 to validate the identification methodology of hardening behaviour under biaxial loading. This alloy has been chosen since its hardening behaviour is not dependent on the strain rate. Digital Image Correlation (DIC) technique is used for strain measurement. The parameters of isotropic hardening models are identified by inverse analysis based on the finite element model of the biaxial tensile test. Three yield criteria of Mises, Hill48 and Bron and Besson are compared for the parameter identification of different hardening laws. It is shown that the hardening law identified by biaxial test is precise only if an appropriate yield function is preliminarily determined. The biaxial flow stress curve identified with Bron and Besson yield function have been found in good agreement with the experimental flow stress curve obtained from uniaxial tensile tests. For biaxial tests at intermediate strain rates, damping layers are adopted to reduce oscillations on force versus time curves. The comparison of flow stress curves, identified from quasi-static and dynamic biaxial in-plane tensile tests on the non strain rate-dependent material AA5086, validates the identification methodology of strain-rate dependent hardening models. Finally, the proposed methodology is applied to the hardening characterization of a strain-rate dependent Dual Phase steel DP600 at room temperature. Identified biaxial flow stress curves have been compared with uniaxial ones for different strain rates ( . = 10-3s-1, 10-1s-1 and 101s-1). DP600 steel exhibits the same positive strain rate sensitivity for uniaxial and biaxial strain states. The biaxial flow stress curves identified on the basis of Ludwick and Voce hardening models are close, up to equivalent plastic strains of 30%. The benefits of the proposed methodology, based on a biaxial in-plane tensile test carried out on cross specimen, are clearly shown since the hardening behaviour identified in this case for large strains (up to 30%) is very different from the one identified from uniaxial tensile test on a smaller strain range.

Orientador: Marcelo Giannini / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ondontologia de Piracicaba / Made available in DSpace on 2018-08-08T01:52:29Z (GMT). No. of bitstreams: 1 Arrais_CesarAugustoGalvao_D.pdf: 8768801 bytes, checksum: bf5f97c936134b9476bb797b23d446d6 (MD5) Previous issue date: 2006 / Resumo: A não fotoativação do sistema adesivo previamente à aplicação do cimento resinoso tem sido proposta quando sistemas de cimentação de dupla ativação (SCDA - sistemas adesivos de dupla ativação / cimentos resinosos de dupla ativação) são utilizados. Entretanto, existe uma carência de relatos científicos a respeito da efetividade dos SCDA. Os objetivos deste estudo foram: 1- avaliar a resistência de união (RU) e a morfologia da interface de união de restaurações indiretas de compósito através da utilização da microscopia confocal laser quando os sistemas adesivos de dupla ativação foram ou não fotoativados previamente à aplicação dos cimentos resinosos; 2- analisar o grau de conversão (GC), através da Espectroscopia Infravermelha Transformada de Fourier (FTIR), e a RU de SCDAs quando a fotoativação não foi realizada ou atenuada pela presença da restauração indireta; 3- avaliar o GC e resistência coesiva de sistemas de união quando utilizados diferentes unidades de fotoativação (LEDs e de luz halógena). A RU e resistência coesiva foram avaliadas através do ensaio de microtração. Para a análise em microscopia confocal laser, diferentes corantes foram incorporados nos SCDAs previamente à sua aplicação. Para a análise do GC, os SCDAs foram aplicados na superfície do diamante da unidade de reflectância total atenuada acoplada ao espectrômetro infravermelho. O GC dos sistemas de união não relacionados aos SCDAs foi obtido utilizando-se filmes de resina adesiva. Os resultados demonstraram que a não fotoativação do sistema adesivo de dupla ativação previamente à cimentação não afetou a RU, e que os valores foram até superiores para um SCDA de 4ª geração quando o agente de união não foi fotoativado. A análise em microscopia confocal laser exibiu variação nas características morfológicas da interface de união, variando de acordo com o SCDA utilizado e com o modo de ativação de ambos componentes (sistema adesivo e cimento resinoso). Para alguns SCDAs, o GC foi reduzido pela presença do disco de compósito posicionado entre o SCDA e a ponta da unidade fotoativadora. A não fotoativação dos SCDAs resultou em GC inferiores aos obtidos com exposição direta da luz. A não fotoativação da maioria dos SCDAs também resultou em valores inferiores de RU, exceto quando um sistema de 4ª geração foi utilizado. A utilização de LED resultou em GC inferior ao obtido quando a luz halógena foi utilizada mas não afetou a resistência coesiva dos sistemas adesivos avaliados. Pode-se concluir que a não fotoativação dos sistemas adesivos é uma alternativa aceitável durante a cimentação de restaurações indiretas, porém os SCDAs necessitam de luz fotoativadora para garantir adequada RU. A utilização de LEDs pode comprometer o GC dos sistemas adesivos / Abstract: The lack of light-activation of dual-cured bonding agents before the resin cement application has been an alternative technique of cementing indirect restorations when dual-cured cementing systems are used (DCS ¿ dual-cured bonding agents / dual-cured resin cements). However, few reports exist regarding the effectiveness of DCS when dual-cured bonding agents are left in the uncured state before the seating of the indirect restoration. Therefore, the aims of this study were: 1- to evaluate the microtensile bond strength (MTBS) and micromorphology of the adhesive interface of indirect restorations by confocal laser microscopy (CLSM) when the dual-cured bonding agents were left in the uncured state; 2- to analyze the degree of conversion (DC) by Fourier Transformed Infrared Spectroscopy and the bond strength of indirect restorations when DCSs were applied to the tooth and light activated or allowed to self-cure; 3- to evaluate the DC and ultimate tensile strength (UTS) of bonding agents light-activated with light curing units (LEDs and halogen light). The MTBS and UTS were analyzed using microtensile bond strength test. Different dyes were incorporated to the DCSs before they were applied to teeth for the CSLM analysis. For the DC analysis, the DSCs were applied to the diamond surface of attenuated total reflectance unit of the infrared device. The DC of the bonding agents related to the study evaluating the effectiveness of light-curing units was obtained from thin resin adhesive films. The results demonstrated that the MTBS was not affected, and the values were even higher for one 4th generation DCS, when the dual-bonding agents were left in the uncured state before the resin cement application. The CLSM analysis exhibited some variation in the micromorphological features, which depended on the DCSs and on the curing modes of bonding agents and resin cements. Some DCSs showed lower DC when pre-cured resin composite discs were used. The self-cured groups exhibited lower MTBS than the light-activated ones, except for one 4th generation DCS. The LED promoted lower DC in all bonding agents than did the halogen light. No difference in UTS was observed when LED was used. It was concluded that leaving the dual-cured bonding agent in the uncured state before seating the indirect restoration may be a reliable technique to ensure adequate MTBS, but most DCSs should be light-activated after seating the indirect restoration to provide optimal bond strength. Some LEDs can compromise the DC of adhesive systems / Doutorado / Dentística / Doutor em Clínica Odontológica

Orientador: Marcelo Giannini / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-18T10:52:55Z (GMT). No. of bitstreams: 1 Aguiar_ThaianeRodrigues_D.pdf: 24572936 bytes, checksum: 8141f58fcbce6835d1091f52127552a7 (MD5) Previous issue date: 2011 / Resumo: O emprego dos cimentos resinosos na fixação de peças protéticas têm sido avaliado em muitos estudos, entretanto, trabalhos que simulem os desafios presentes na cavidade bucal e o comportamento a longo prazo dos cimentos resinosos autoadesivos ainda são escassos na literatura. Diante disso, o presente estudo teve como objetivo: 1) verificar a composição inorgânica das partículas de carga e caracterizá-las quanto ao tipo e morfologia; 2) analisar a ultramorfologia da interface de união dentina-cimento resinoso através da microscopia confocal por varredura a laser e da microscopia eletrônica de varredura (MEV); 3) avaliar o efeito do armazenamento por 1 ano ou da ciclagem mecânica (50.000 ciclos) na resistência de união dentina-cimento resinoso. Quatro cimentos resinosos foram avaliados: dois autoadesivos (RelyX Unicem, 3M ESPE e Clearfil SA Luting, Kuraray Medical Inc.) e dois convencionais (RelyX ARC/Adper Scotchbond Multi-Purpose Plus, 3M ESPE e Clearfil Esthetic Cement/Clearfil DC Bond, Kuraray Medical Inc.). Para analisar os principais componentes inorgânicos e avaliar as características das partículas de carga, o conteúdo orgânico dos cimentos resinosos foi removido por solventes orgânicos e as amostras analisadas em MEV/EDX (Espectroscopia de energia dispersiva por raios-X). Terceiros molares humanos foram utilizados na avaliação da ultramorfologia da interface dentina-cimento resinoso e no ensaio de resistência de união à dentina. Na análise da ultramorfologia da área de união, corantes (fluoresceína e rodamina) foram previamente adicionados aos materiais estudados para possibilitar a obtenção das imagens. Para o ensaio de resistência de união, discos de resina composta indireta foram confeccionados visando simular as restaurações indiretas. Após a cimentação, os dentes restaurados foram submetidos a três tratamentos e ao ensaio de microtração: 1- espécimes testados após 24 h (grupo controle); 2- ciclagem mecânica e em seguida testados; 3- armazenados em saliva artificial por 1 ano na forma de "palitos" e testados. Os dados obtidos a partir do ensaio de resistência de união foram analisados estatisticamente (ANOVA e teste Tukey, p<0,05). Nos outros dois estudos, a análise descritiva dos dados obtidos a partir das imagens microscópicas foi realizada. Na avaliação MEV/EDX notou-se elevado conteúdo de silício em todos os materiais. O cimento RelyX ARC apresentou partículas de carga esféricas e irregulares, enquanto os outros materiais demonstraram partículas com formato irregular. Nas fotomicrografias, a hibridização dentinária somente foi observada para os sistemas de cimentação convencional. No ensaio de resistência de união, os tratamentos não influenciaram a resistência de união dos cimentos resinosos à dentina. Os cimentos autoadesivos apresentaram médias de resistência de união significantemente superiores aos chamados convencionais. Embora os materiais avaliados apresentem partículas de carga com distintas composições inorgânicas e interagem com a dentina através de diferentes mecanismos, os tratamentos de envelhecimentos propostos não reduziram a resistência de união à dentina, quando comparados ao grupo controle. Os cimentos autoadesivos não formam camada híbrida na dentina intertubular, nem tags de resina nos túbulos dentinários, entretanto, apresentam partículas de carga com maior tamanho e demonstraram os maiores valores médios de resistência de união à dentina entre os cimentos estudados / Abstract: Resin luting materials to fixed prosthetic restorations have been evaluated in many studies, however, little is known about self-adhesive resin cements, mainly involving long-term durability and when these materials have been submitted to challenges of oral environment. Thus, the purpose of this study was: 1- to verify the filler particles components and to characterize them according to type and morphology; 2- to analyze the ultramorphology of the dentin-resin interfaces using confocal laser scanning microscopy and scanning electron microscopy (SEM) and 3- to evaluate the effect of the storage for 1 year or the mechanical cycling (50.000 cycles) on bond strength of resin cements to dentin. Four resin cements were used in this study: two self-adhesive resin cements (RelyX Unicem, 3M ESPE and Clearfil SA Luting, Kuraray Medical Inc.) and two conventional resin cements (RelyX ARC/Adper Scotchbond Multi- Purpose Plus, 3M ESPE and Clearfil Esthetic Cement/Clearfil DC Bond, Kuraray Medical Inc.). For indentifying the main inorganic components and to evaluate the filler particles characteristics, the organic phase of resin cements was removed using organic solvents and the sample was analyzed by SEM/EDX (Energy-dispersive X-ray spectroscopy). Human third molars were used for micromorphology analysis of resin-dentin interfaces and microtensile bond strength test. For micromorphology analyses of resin-dentin interfaces, two fluorescent dyes (fluorescein and rhodamine B) were incorporated into the materials previously. For microtensile bond strength, pre-polymerized resin discs were prepared to simulate indirect restorations. After bonding procedures, the restored teeth were submitted to three treatments: 1- control group (tested 24 h after specimen preparation); 2- tested after mechanical cycling; 3- beams were storage for one year in artificial saliva and tested. Bond strength data were statistically analyzed by two-way ANOVA and Tukey test (?<0.05). Qualitative analysis was performed for two other studies using microscopic images. For SEM/EDX measurements, high amount of silicon was identified for all cements. The resin cement RelyX ARC showed spherical and irregular particles, while other cements presented irregular shape fillers. Hybrid layer formation was observed only for conventional resin cements in micromorphology analyses. For microtensile test, the treatments did not reduce the bond strength between dentin-resin cement. Self-adhesive resin cements provide significantly higher bond strength than those conventional materials. Despite the resin cements showed filler particles with differences in the inorganic composition and different bonding mechanisms, the mechanical cycling and storage for one year did not affect the bond strength to dentin when it was compared to control group. The self-adhesive resin cements showed no hybrid layer formation in intertubular dentin and nor resin tags in the dentinal tubules were detected. However, these materials showed the biggest filler particles and higher bond strength to dentin than conventional resin cements studied / Doutorado / Dentística / Doutor em Clínica Odontológica

Ce travail thèse a pour objet une méthode expérimentale combinant un essai de traction indirect par écaillage et une mesure de champs à partir d’images obtenues par caméra ultra rapide, ceci à des fins d’identification des propriétés de rupture du béton sous chargement de traction dynamique. Cette méthode, proposée dans la littérature peu de temps avant le démarrage de ces travaux, fait ici l’objet d’une étude approfondi ainsi que d’une série de développements et d’amélioration. Les images obtenues sont traités par une technique de grille et la méthode des champs virtuels est appliquée pour identifier le comportement local des matériaux quasi-fragiles soumis à de hautes vitesses de déformation (plusieurs 100 1/s}). Dans un premier temps, afin de valider la technique de traitement maus aussi d’étudier l’incertitude de mesure associée, un simulateur de la chaîne de mesure complète a été mis au point. Il a été ainsi possible d’étudier l’influence de différentes sources potentielles d’erreurs qui peuvent être rencontrées dans le protocole expérimental. Cette étude a permis de retenir des recommandations sur les conditions de réalisations réelles de l’essai afin d’améliorer la fiabilité des mesures obtenues. D’un point de vue expérimental, différents capteurs ultra haute vitesse ont été utilisés afin d’étudier leur performances vis-à-vis des mesures réalisées. Ainsi, les campagnes d’essais ont été réalisées sur un matériau aux caractéristiques bien identifiées permettant l’étude des performances métrologiques de toute la chaine d’identification, pour chaque modèle de capteur. Enfin, le protocole expérimentale a été mis en place pour étudier le comportement de plusieurs types de béton soumis en traction dynamique. L’objectif, ici, est d’identifier leur comportements mécaniques ainsi que leur caractéristiques de rupture et fragmentation sous traction dynamique. En ce qui concerne la résistance à la traction, les valeurs identifiées dans cette étude sont inférieures, pour chaque cas, à celles rapportées dans la littérature et obtenues, pour la plupart, à partir du traitement de la vitesse matérielle mesurée en face arrière de l’échantillon. Pour ce qui est de l’énergie spécifique de rupture, les valeurs obtenues dans ces travaux sont égalements inférieures à celles publiées dans les revues scientifiques. / In this thesis a recently proposed photomechanical spalling experiment has been used in light of identifying concrete failure properties under dynamic tension.The experimental technique uses ultra-high speed imaging, the grid method and the virtual fields method.First, in order to investigate the accuracy and validate the processing technique, a methodology of using simulated experiments has been developed by numerically simulating the entire identification process.In this way, several potential sources of errors have been investigated allowing to place guidelines on how to perform the experiment in a more reliable manner.Second, several latest ultra-high speed acquisition systems have been used in order to investigate their contribution to a possible measurement refinement.In this case, the trial experiments have been conducted on a material of known characteristics which allowed investigating the metrological performance of the acquisition system on the entire identification chain.Finally, the experimental methodology has been applied to testing several grades of concrete in light of identifying the material constitutive response as well as their fracturing characteristics under dynamic tension.The identified tensile strengths in this work were found to be consistently lower than those obtained from the standard processing of the rear-face velocity profile.Moreover, the values of the identified specific fracture energy were also found to be markedly lower than the ones often reported in the literature.

Content: With the development of China sports, researches related to sports leather should be paid attention because they usually required higher strength than commonly used leather. In this paper, we focus on the production of gymnastics leather. In gymnastics, the athlete's hand will have high intensity contact with the balance bar, so the gymnastics leather is required to have high intensity performance. At the same time, in order to comply with the ornamental function, gymnastics leather is required to be light color. In this research, glutaraldehyde was used as the main tanning agent, while acrylic polymer and synthetic were used for retanning, in order to obtain high strength, environmentally friendly white gym leather. The shrinkage temperature and mechanical properties of tanned leather were determined and analyzed to determine the suitable tanning agent. Besides, other properties including softness, gas permeability, water permeability, flexing resistance and yellowing-resistance were also measured for selecting proper production process. Therefore, gymnastics leather with ideal performance can be prepared by this method, and the leather conforms to the practical application standard. In addition, the research has guiding significance and application prospect for high strength chrome-free tanned leather. Take-Away: Aldehyde tanning agents and retanning agents, which can be used for gymnastics leather making, were evaluated and selected to achieve ideal effect of finish leather. This research is meaningful to produce not only gymnastics leather but also other sporty leather which require high strength.

Content: Since hundreds of years, tanners share the opinion that hides from different cattle breeds lead to varying leather qualities. Especially European hides from the alpine region (e. g. Simmentaler or brown origin) are preferred by tanners. These leathers feature a higher thickness, a maximum utilisation induced by a minor thickness difference over the whole area and a lower tensile strength in contrast to leathers from other breeds. However, are these alpine hides better because of their breed affiliation or because they are kept in special regional conditions? It is known that, besides the breed, also other factors can influence the rawhide and leather quality like age, gender, nutrition and climate conditions. In addition, present dairy and beef cattle are high-performance cattle by breeding, which leads to more crossbreeds than 100 years ago. Our intention was to find out, whether leather quality nowadays is still a function of breed or not. For that purpose, 40 rawhides from four different cattle breeds (Angus, Charolais, Simmentaler, Limousin) were collected from the Saxon region. From each breed, five male and five female rawhides were collected. The age of each individual was restricted to two years. All 40 rawhides were tanned with the same technology for furniture leather. Leather quality was characterized by determining chemical and physical parameters. Chemical parameters included collagen content, fat content and ignition lost (DIN 181218). The physical parameters were tensile strength (DIN EN ISO 3376), elongation at break (DIN EN ISO 3376) and stitch tear resistance (DIN EN ISO 23910). The analyses revealed that the chemical parameters were identical for all examined breeds. For this reason, the chemical composition of a cattle skin is irrespective of breed origin. The tensile strength of the leathers showed only a small significant difference between Angus and Limousin (p= 0.05). Leathers from Limousin hides showed significantly different elongations at break compared to Angus, Charolais and Simmentaler. The stitch tear resistance varied in nearly all breeds. Significant differences were detected between all breeds except between Angus and Charolais as well as Angus and Simmentaler. Plotting the measured physical values against gender or age of the individuals showed no correlation. In summary, only minor differences between the cattle breeds were found. But this tendency must be confirmed by a larger quantity of test individuals. For this purpose, an analysis is planed with 100 individuals from different breeds and crossbreeds. Take-Away: Many tanners share the opinion that hides from different attle breeds lead to varying leather qualities. We found only minor differences of the physical parameters between the cattle breeds with a random sample of 10 individuals per breed. To confirm this tendency, an analysis is planed with 100 individuals from different breeds and crossbreeds.