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Showing 1 to 4 of 4 (0.039 seconds)Spelling suggestions: "subject:"atructural para"" "subject:"dtructural para""
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Material and Process Models for the Forming of Oriented Polymer TubesAzhikannickal, Elizabeth 03 1900 (has links)
<p>The lightweight and good strength of oriented thermoplastic tubes, produced through the ram extrusion process, renders this class of material advantageous from an automotive structural part forming perspective. An analytical model, capable of predicting the forming limits for these materials at elevated temperatures, would avoid the need for difficult and time-consuming tube forming experiments.</p> <p> The uniaxial tensile stress-strain properties of the oriented polypropylene (OPP) tubes along the axial and hoop direction wene determined while methods were developed for obtaining the uniaxial compressive properties of the tube. The uniaxial and biaxial testing of the OPP tubes enabled representation of the experimental plastic work contours for the material at a range of temperatures. The use of the pressure-modified Hill criterion, the concept of plastic work contours in stress space, and the stress strain data from uniaxial testing of the tube allowed accurate prediction of the plastic work contours for the OPP tubes as a function of temperature. The analytical prediction was able to capture the anisotropy, pressure dependency and anisotropic hardening exhibited by the material at elevated temperatures. In addition, the use of a localized necking criterion, which involved the point at which the maximum force along the hoop direction of the tube was reached, allowed the temperature dependent forming limits for the material to be predicted. The forming limits increased with temperature for all of the strain paths considered. In addition, at a given temperature, the forming limits decreased with increasing strain ratio. The limiting strains achieved with axial end feeding were markedly higher than those in which no axial end feeding was used. </p> <p> Good agreement was observed between the predicted forming limits and the results from tube forming tests of the material, along a range of strain paths and at various temperatures.</p> / Thesis / Doctor of Philosophy (PhD)
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Endommagement par fatigue et durée de vie de structures en matériaux composites à fibres continues pour application liaison au sol / Fatigue damage and lifetime prediction of continuous fibre reinforced composites used for suspension systems applicationBen Toumi, Rim 26 October 2015 (has links)
L'allègement des véhicules est un enjeu majeur de l'industrie automobile pour participer, avec l'évolution des motorisations, à la maîtrise des consommations énergétiques et la réduction des émissions de gaz à effet de serre. Dans ce travail, nous nous intéressons à l'introduction des matériaux composites dans les pièces de structure et particulièrement dans le périmètre de la liaison au sol composé d'organes de sécurité active, sujets au phénomène de fatigue multi axiale à grand nombre de cycles.Les matériaux composites présentent une solution séduisante en raison de leurs propriétés mécaniques intéressantes combinées à une faible densité. Toutefois, la fatigue des matériaux composites reste un sujet complexe relativement peu abordé. C'est dans ce cadre que s'inscrit cette thèse qui vise à mettre en place une méthodologie de dimensionnement des composants automobiles de structure, à partir d'un composite tissé verre/époxy. Cette méthodologie s'attache à être facile d'utilisation et adaptable au calcul de structure pour être applicable en Bureau d'Études. La première étape de cette étude est la caractérisation de la tenue en service du matériau sous chargements monotones et cycliques et l'identification des cinétiques d'endommagement. Au vu des résultats expérimentaux obtenus et à partir des approches de dimensionnement existantes, un critère de fatigue multi axiale est proposé. Ensuite, une optimisation du protocole d'identification des paramètres est effectuée afin de réduire au minimum le volume des campagnes d'essais. Enfin, le critère mis en place pour évaluer la durée de vie en fatigue du matériau composite tissé est validé sur des éprouvettes trouées et sur le train avant à lame composite. / The reduction of fuel consumption and greenhouse gas emissions is one of the most important challenges facing the automotive industry. An efficient strategy to meet these targets is by reducing the weight of vehicle. In this work, we are interested in introducing composite materials in automotive structural parts and especially in suspensions which are subjected in service to high-cycle fatigue loadings. Therefore, a good prediction of fatigue life is required. As continuous fibre-reinforced composites provide good mechanical properties combined with a low density, they have been increasingly used in many lightweight structures. However, the fatigue behaviour of composites has not been widely investigated. This work aims at developing an approach to predict the lifetime in service of structural automotive components, made with woven glass / epoxy composite. This approach has to be easy to use by design engineers at the scale of the structure. The first step is the characterization of the material. Then, the processes involved in degradation of the composite subjected to both monotonic and cyclic loadings were identified.Given the experimental results and the existing approaches, a multiaxial fatigue criterion is proposed. An optimization of the identification protocol is also performed to reduce the quantity of needed experimental data. Finally, the fatigue life prediction model criterion is validated by tests on notched coupons and on composite vehicle's suspension.
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Beitrag zu hochbelasteten Krafteinleitungselementen für Faserverbundbauteile / Excerpt to heavy load force translation components for fibre composite elementsSchievenbusch, Florian 19 September 2003 (has links) (PDF)
Fibre reinforced plastics (FRP) are increasingly employed in structural parts of the automotive, aviation and aerospace as well as railway industries. For those applications a heavily loaded, as well as crash and safety relevant force translation component is developed. This Hybrid-Insert consists of SMC and a metal insert, and is based on modular assembly through standard elements. The galvanic insulation of the metal insert by the SMC provides an excellent corrosion protection. The couplingstrength of the metal insert moulded into the SMC fulfills the tensile requirements of a M10 10.9 screw fit by VDI 2230 standards. Additionally the component provides a high degree of energy absorption and a gradual failure process. / Faserverstärkte Kunststoffe (FVK) werden zunehmend in Strukturbauteilen der Automobil-,der Luft- und Raumfahrt- sowie der Schienenfahrzeugindustrie eingesetzt. Für diese Anwendungen wird ein hochbelastetes sowie crash- und sicherheitsrelevantes Krafteinleitungselement entwickelt. Dieses Hybrid-Insert, bestehend aus SMC und einem Metalleinsatz, ist modular aus Standardkomponenten aufgebaut. Die galvanische Isolation des Metalleinsatzes durch das SMC bietet für diesen einen hervorragenden Korrosionsschutz. Die Verankerungsfestigkeit des Metalleinsatzes im SMC genügt den Anforderungen einer M10 10.9 Verschraubung nach VDI 2230. Zusätzlich zeichnet sich das Krafteinleitungselement durch eine hohe Energieabsorption und ein gutmütiges Versagen aus.
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Beitrag zu hochbelasteten Krafteinleitungselementen für FaserverbundbauteileSchievenbusch, Florian 11 August 2003 (has links)
Fibre reinforced plastics (FRP) are increasingly employed in structural parts of the automotive, aviation and aerospace as well as railway industries. For those applications a heavily loaded, as well as crash and safety relevant force translation component is developed. This Hybrid-Insert consists of SMC and a metal insert, and is based on modular assembly through standard elements. The galvanic insulation of the metal insert by the SMC provides an excellent corrosion protection. The couplingstrength of the metal insert moulded into the SMC fulfills the tensile requirements of a M10 10.9 screw fit by VDI 2230 standards. Additionally the component provides a high degree of energy absorption and a gradual failure process. / Faserverstärkte Kunststoffe (FVK) werden zunehmend in Strukturbauteilen der Automobil-,der Luft- und Raumfahrt- sowie der Schienenfahrzeugindustrie eingesetzt. Für diese Anwendungen wird ein hochbelastetes sowie crash- und sicherheitsrelevantes Krafteinleitungselement entwickelt. Dieses Hybrid-Insert, bestehend aus SMC und einem Metalleinsatz, ist modular aus Standardkomponenten aufgebaut. Die galvanische Isolation des Metalleinsatzes durch das SMC bietet für diesen einen hervorragenden Korrosionsschutz. Die Verankerungsfestigkeit des Metalleinsatzes im SMC genügt den Anforderungen einer M10 10.9 Verschraubung nach VDI 2230. Zusätzlich zeichnet sich das Krafteinleitungselement durch eine hohe Energieabsorption und ein gutmütiges Versagen aus.
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