L’objectif de cette thèse est d’étudier le comportement d’un mélange de fluide supercritique(diazote ou dioxyde de carbone) et de polyuréthane thermoplastique àl’état fondu lors de la mise en œuvre de butée d’attaques d’amortisseurs par le procédé d’injection Mucell®. Dans un premier temps, l’état de l’art a été développé dans une synthèse bibliographique qui a permis de décrire les principaux phénomènes intervenants lors de la transformation d’un mélange de fluide supercritique et de polymère en mousse micro-cellulaire. Puis, une étude à l’échelle laboratoire a permis de caractériser et de modéliser le comportement d’un polyuréthane thermoplastique mis en contact avec un fluide supercritique et de déduire les caractéristiques et les comportements essentiels à la compréhension des différents phénomènes rencontrés dans le procédé de mise en œuvre (diffusion, solubilité, nucléation...). Enfin, la dernière partie de ces travaux concerne la mise en application des connaissances précédemment acquise sur les moyens industriels dans le but de d’analyser et de stabiliser le moussage micro-cellulaire généré. / The aim of this thesis is to study the behavior of a supercritical fluid (nitrogen or carbon dioxide) and thermoplastic polyurethanemeltmix during the production of jounce bumpers by the MuCell® injection molding process. First of all, the state of the art was developed in a literature review which allowed to describe the main phenomena that occur during processing of a mixture of supercritical fluid and polymer in microcellular foam. Then, a study at the laboratory scale allowed to characterize and model the behavior of a thermoplastic polyurethane in contact with a supercritical fluid and deduct the characteristics and behaviors essential to the understanding of various phenomena encountered during the process(diffusion, solubility , nucleation...). Finally, the last part of this work concerns the implementation of previously acquired knowledge on industrial means in order to analyze and stabilize the generated microcellular foam.

The following paper will illustrate the development of a multiflex chain in hybrid construction. The aim of this novel chain variant is to improve the stiffness and strength in comparison to conventional plastic slide chains. A two part multiflex chain with a chain pitch of 33.5 mm and a structural width of 83 mm was used as the basis for the development of the hybrid multiflex chain. The hybrid multiflex chain is supposed to be integrated in already existing layouts of chain conveyors. The load bearing structure of the single chain links is manufactured in the metal die cast procedure while taking the constructive, production related, and operational aspects into consideration and subsequently covered in the injection molding process with plastics commonly used for multiflex chains. The evaluation of the improved stiffness and strength takes place in the course of extensive test series. / In der folgenden Abhandlung wird die Entwicklung einer Multiflex-Kette in Hybridbauweise erläutert. Mit dieser neuartigen Kettenvariante soll eine Steifigkeits- und Festigkeitssteigerung gegenüber den konventionellen Kunststoffgleitketten erzielt werden. Als Ausgangsbasis für die Entwicklung der hybriden Förderkette dient eine zweiteilig ausgeführte Multiflex-Kette mit der Teilung von 33,5 mm und einer Baubreite von 83 mm. Die hybride Förderkette soll in bestehende Layouts von Kettenförderern integriert werden können. Unter Beachtung konstruktiver, fertigungstechnischer und betrieblicher Aspekte wird die lasttragende Struktur der einzelnen Kettenglieder im Metalldruckgussprozess gefertigt und anschließend mit einem, für Multiflex-Ketten üblichen Kunststoff im Spritzgießprozess ummantelt. Die Evaluierung der Steifigkeits- bzw. Festigkeitssteigerung erfolgt im Rahmen umfangreicher Versuchsreihen.

The use of fiber-reinforced polymer composites formed via injection molding is of increasing interest due to their superior mechanical properties as compared to those of the polymer matrix alone. These mechanical properties, however, are strongly dependent on the fiber length and orientation distributions within a molded part. As such, there is a need to understand and model the orientation evolution of chopped fibers in flow in order to accurately simulate the final fiber orientation distribution within injection molded parts. As a result of this, accurate and reliable experimental measurement of fiber orientation is needed. Within this research, the application and validity of the Method of Ellipses for determining the orientation of long, semi-flexible glass fibers within injection molded composites has been investigated. A fiber suspension with an average length of approximately 3.9 mm was the focus of this study and assumed to be representative of commercial distributions. A novel method to quantify fiber curvature was developed and utilized to show that flexibility in center-gated disc and the end-gated plaque samples was minimal on average for the selected fiber length distribution. Thus, it was determined that the Method of Ellipses was applicable when utilized to obtain reliable orientation data for the selected long glass fiber suspension and within the chosen geometries that exhibit 1-, 2-, and 3-dimensional velocity fields. However, a modified image analysis width was found to be necessary in regions of highly aligned fibers, due to the increase in ellipse size and the need to reduce the number of partial objects and thus minimize error. This allowed for a direct comparison of the experimental orientation behavior of short and long glass fibers within the center-gated disc and the end-gated plaque, as well as the effect of the orientation distributions on the global modulus of the part. / Ph. D.

I have used computer simulations to investigate the behavior of polymeric materials at the molecular level. The simulations were performed using the molecular dynamics method with Lennard-Jones potentials defining the interactions between particles in the system. Significant effort was put into the creation of realistic materials on the computer. For this purpose, an algorithm was developed based on the step-wise polymerization process. The resulting computer-generated materials (CGMs) exhibit several features of real materials, such as molecular weight distribution and presence of chain entanglements. The effect of the addition of a liquid crystalline (LC) phase to the flexible matrix was also studied. The concentration and distribution of the second phase (2P) were found to influence the mechanical and tribological properties of the CGMs. The size of the 2P agglomerates was found to have negligible influence on the properties within the studied range. Moreover, although the 2P reinforcement increases the modulus, it favors crack formation and propagation. Regions of high LC concentration exhibit high probability of becoming part of the crack propagation path. Simulations of the tensile deformation under a uniaxial force have shown that the molecular deformation mechanisms developing in the material depend on several variables, such as the magnitude of the force, the force increase rate, and the level of orientation of the chains. Three-dimensional (3D) graphical visualization tools were developed for representation and analysis of the simulation results. These also present interesting educational possibilities. Computer simulations provide us information which is inaccessible experimentally. From the concomitant use of simulations and experiments, a better understanding of the molecular phenomena that take place during deformation of polymers has been established.

This diploma thesis deals with assessment of environmental load by selected plastic molding technology. The first part is focused on the ecological legislation in the field of mechanical engineering, which also includes the production of plastics, and describes various methodologies for assessing the environmental load. Another chapter is an overview of polymers and their properties as well as the possibilities of plastics processing with description of individual types of production methods. The practical part of this work describes the composition of the produced piece and the injection molding process of plastic production. Its two methods (direct gating and hot sprue method) are analyzed and then the environmental load evaluation is performed using the LCA method – product life cycle assessment. The environmental load of both production methods is assessed.

This thesis describes influence of plasticizers and setting accelerators in binder system based aluminasilikates. Following survey includes changes of characteristics of aluminate cements in combination with various setting accelerators. Practical testing and measuring summarizes and compares interdependence of structure, compressive strength, permeability and abrasion resistance. As a final part of thesis individual mixes are analysed economically and are accompanied by suggestions for future use and use in working experience.

The subject of this thesis was to develop a comprehensive methodology for evaluating the plasticity of molding sand. This study was focused on four types of mixtures that are used in the foundry industry. For the evaluation of plasticity was important to provide an indicator of the deformation ability, calculation of deformation and logarithmic transformation for compression. Plasticity methodology was applied in this work only on the pressure effect. Studies of this issue can have a great influence on the production of correct forms due to the ability to withstand tension without breaking form.

This thesis deals with optimization of a press line part for the manufacture of reflectors present at the Automotive Lighting Company, Jihlava. The first part focuses on describing the current workplace layout of the press line. The workplaces are located inconveniently and thus require a larger number of operators and a considerable amount of manual work. The second part of the thesis proposes layout solutions for the injection presses and for other machine parts. At the same time, a smoother transition design is proposed for the press line and for the manufacturing section that follows. Based on an evaluation of selected criteria, the optimum version is chosen, thereby adding to the efficiency of the molding process by reducing the number of operators required, by lowering the proportion of manual work relative to other activities, and by limiting the risk of poor quality. The conclusion of the thesis sums up the necessary investment costs and offers an economic assessment of introducing the selected press line arrangement to operation.

This diploma thesis deals with thermal qualities of moulding mixtures of foundry mould of various types of sand grains and a computer simulation of the solidification of the cast. The aim of this work is to compare the values of thermal qualities of moulding materials bonded with water glass taken in experimental measurements to the values of thermal qualities of moulding materials connected with organic binding agent contained in simulation software. A sample cast will be moulded in order to evaluate cooling capacities of individual moulding mixtures according the shift of thermal axis. These results will consequently be compared to the results of the simulation.

The thesis deals with the design and arrangement of a new paint line at company Automotive Ligting s.r.o in Jihlava. It deals with design of several possible options of arrangement of machines that are required for the processing of polycarbonate granules and their conversion into acrylic glass using two-component injection molding. The glass is then coated with the coating line which is part of the arrangement included in this project. Design of the individual sites and their organization is based on both the company's requirements and the principles of technological design. The best of the three options is analyzed in detail and evaluated from the economic point of view.