Temperature-dependent anisotropic material modeling of the sheet metal component within the polymer injection forming process
In the course of this work, an extended material model for a carbon steel sheet metal has been developed based on Hill’48 yield criterion, considering temperature-dependent plastic anisotropy coefficients. This material model is applied on a polymer injection forming process in which the sheet metal heats up to a critical forming temperature through the contact with the plastic melt. At this temperature range blue brittleness occurs. The elastic properties, the yield stress as well as the plastic anisotropy coefficients of the sheet material become significantly different compared to those at room temperature. It should be emphasized that especially temperature-dependent anisotropy coefficients are not yet considered in most common material models. With the help of the presented modelling approach a more precise modelling of the temperature-dependent carbon steel material behavior can be realised.
Kunststoffe im Automobilbau
Thermoplastische und duroplastische Kunststoffe, Elastomere, textile Materialien und Faserverbundkunststoffe gehoren heute zu den Standardwerkstoffen im modernen Automobilbau. Diese Werkstoffklasse unterstutzt nachhaltig den automobilen Leichtbau, die aktive und passive Sicherheit von Kraftfahrzeugen sowie eine optisch und haptisch hochwertige Bauteilgestaltung. Dieser Beitrag gibt einen Uberblick zu aktuellen kunststofftechnischen Entwicklungen aus dem Exterieur und Interieur bei BMW. Daruber hinaus werden neuartige Verbundbauweisen mit Kunststoffen sowie nanotechnologische Ansatze in Verbindung mit Kunststoffen vorgestellt.
Measuring Sheet Resistances of Dielectrics Using Co‐Planar Hydrogel Electrochemical Cells with Practical Applications to Characterize the Protective Quality of Paints on Sculptures
Electrical properties of thin dielectric films at the solid-liquid phase boundary are an important performance characteristic of many devices, coatings and sensors. In this paper, co-polymeric hydrogels of polyacrylic acid co-sulfonic acid, swollen with a salt solution to act as the solid electrolyte, were used to assess interfaces using electrochemical impedance spectroscopy (EIS) in a co-planar geometry. Silane-modified glasses were characterized by the co-planar hydrogel EIS cell and found to be distinguishable based on their surface monolayer chemistry. EIS measurements were also made on primed and painted metal substrates, using both test panels and an outdoor sculpture, Tony Smith's Stinger. The panels were then exposed to accelerated and outdoor weathering and showed degradation on the surface paint layers, which was observable electrochemically using EIS and confirmed visually by SEM. Electrochemical spectral features were compared between data from a standard paint-test cell versus this co-planar hydrogel cell; both cell types were able to measure coating capacitance, providing useful information about the condition of the bulk coating. Yet, sheet resistance (Rs) was a spectral feature seen only by the co-planar hydrogel cell. Thus, it can be concluded that the use of such co-planar hydrogel cells can provide an earlier warning sign to coating degradation and such cells provide a new type of spectral information that is not assessable by the standard geometry.