Fachbereich Technik
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Der Einsatz von Lötverfahren zum Fügen reduziert gegenüber der Schweißtechnik die Prozesstemperaturen und ermöglicht sowohl die Realisierung anspruchsvoller Mischverbindungen als auch das Fügen verzinkter Stähle mit minimaler Zinkschichtverletzung. Aktuelle Entwicklungen von Lotwerkstoffen zielen sowohl in Richtung Absenkung der Schmelztemperaturen als auch in Richtung Festigkeitssteigerung, um die Anwendungsmöglichkeiten noch weiter zu vervielfältigen. Dabei unterliegen sowohl Eisenbasislegierungen als auch Systeme auf Kupfer- oder Zinkbasis einer stetigen Weiterentwicklung. Die bereits heute erreichbaren Festigkeiten reichen bis etwa 900 MPa (CuAl8Mn13Ni2Fe2) bei Kupferbasislegierungen und 410 MPa (AnAl7,5Cu2,5 + 180 ppm Mg) bei Zinklegierungen. Neben der Energieeinsparung durch die reduzierten Prozesstemperaturen beim Fügen und der Möglichkeit Hybridstrukturen herzustellen, ergeben sich außerdem Vorteile bei der Reparatur und dem Recycling von Bauteilen. Da der Zusatzwerkstoff unabhängig vom Grundwerkstoff wiederaufgeschmolzen werden kann, sind eine leichtere Reparatur und auch ein Trennen der Bauteile zum Recycling möglich. Dies führt bei Betrachtung des gesamten Produktlebenszyklus zu einer höheren Energieeffizienz und einer Schonung der natürlichen Rohstoffe und Ressourcen. Durch die steigenden Energie- und Werkstoffkosten und den damit verbundenen Kostendruck rückt dieser Aspekt neben der Machbarkeit und Produktivität langsam, aber sicher ins Blickfeld der Unternehmen. Kostenvorteile ergeben sich außerdem durch Betrachtung und Modifikation ganzer Fertigungsketten. Niedrigschmelzende Zusatzwerkstoffe ermöglichen beispielsweise das Fügen verzinkter Halbzeuge ohne Zinkschichtverletzung. Da Halbzeuge in großen Mengen kostengünstiger verzinkt werden können als fertige Konstruktionen, ist das Fügen verzinkter Halbzeuge insgesamt günstiger als das Verzinken geschweißter Stahlkonstruktionen.
RMOD-K V 7.09
(2007)
There are two aims for the second part of this paper: verifying the theory presented in the first part through parameter variation and comparison between simulation and experiment, and to study the effect of the belt structure on the cornering properties of radial tyres. Research has been carried out with a passenger car radial tyre and two different kinds of truck or bus radial tyres using both simulation and experiment. This second part of the paper shows that belt structure plays an important role in the generation of tyre forces and moments in addition to the effects of the tread stiffness and friction coefficients. The theory and method presented in this paper opens a new robust way to predict the tyre forces and moments from the tyre design and provides a reliable model for a generation mechanism.
Tyre rolling kinematics and prediction of tyre forces and moments: part I - theory and method
(2012)
A new method to describe tyre rolling kinematics and how to calculate tyre forces and moments is presented. The Lagrange–Euler method is used to calculate the velocity and contact deformation of a tyre structure under large deformation. The calculation of structure deformation is based on the Lagrange method, while the Euler method is used to analyse the deformation and forces in the contact area. The method to predict tyre forces and moments is built using kinematic theory and nonlinear finite element analysis. A detailed analysis of the tyre tangential contact velocity and the relationships between contact forces, contact areas, lateral forces, and yaw and camber angles has been performed for specific tyres. Research on the parametric sensitivity of tyre lateral forces and self-aligning torque on tread stiffness and friction coefficients is carried out in the second part of this paper.
Among load cases concerning vehicle suspension strength and durability, the misuse case is very special because of large obstacles. In this paper, an extension of the flexible belt model RMOD-K 7 concerning misuse situations is discussed. In normal rolling conditions, contact occurs between tire and road surface. To handle misuse deformations, the contact between the inner surface of the tire and the rim has to be dealt with. Results of the validation process are shown, leading to normal forces up to 70 [kN]. The model can be used together with mbs full vehicle models. One example is the determination of the critical test velocity, which generates the maximum of suspension stresses and can be found using RMOD-K 7.
Über die Farben der Sonne und des Himmels: Rayleigh- und Miestreuung in Demonstrationsexperimenten
(2002)
Old and new laboratory experiments on atmospheric optics with a focus on mirages, rainbows, and halos are presented. Some qualitative demonstrations serve primarily didactical purposes, e.g., by proving the existence of curved light rays in media with a gradient of the index of refraction, by directly visualizing the minimum-deviation curve for rainbow paths in water droplets, or by helping to elucidate the ray classes in hexagons that contribute to a specific halo. In addition, quantitative experiments allow a direct comparison of angular positions and intensities with analytical computations or Monte Carlo simulations of light scattering from small water droplets or ice hexagons. In particular, the latter can help us to understand complex halo phenomena.
© 1998 Optical Society of America
Some laboratory demonstrations on atmospheric optics are presented. The focus is on dispersion effects in mirages, lateral mirages, and inferior mirages produced with small hot plates. We also show a demonstration of the upper-tangent-arc halo, produced with a hexagonal prism, rotating about two axes.
© 2003 Optical Society of America
Thermography of Microsystems
(2004)
A procedure to experimentally simulate pollen coronas is discussed. Observed coronas are due to pine and birch pollen having different geometries. Using computer simulations, two-dimensional projections of a large number of pollenlike objects with adjustable shapes, with or without preferential orientation and statistical or regular spatial distribution, are generated. The photograph of the printout allows samples with typical sizes between 20 and 200 µm. Their diffraction patterns can closely resemble the ones observed in nature and predicted by theory.
© 2005 Optical Society of America
Light scattering from small particles changes if the particles are absorbing. Whereas the effect is small for coronas and Bishop's ring, glories show pronounced attenuation with increasing absorption. Results indicate suitable wavelength regions for studies of glory scattering from cloud tops. The behavior of core-shell particles could have applications for studying the atmosphere of Venus; in addition it provides more insight into the simple ray-path model of the glory.
© 2005 Optical Society of America
Solar load and reflection effects and respective time constants in outdoor building inspections
(2009)
Rainbows, water droplets, and seeing—slow motion analysis of experiments in atmospheric optics
(2011)
Many physics processes underlying phenomena in atmospheric optics happen on a rather short time scale such that neither the human eye nor video cameras are able to analyze the details. We report applications of high-speed imaging of laboratory experiments in atmospheric optics with subsequent slow motion analysis. The potential to study respective transient effects is investigated in general and for a few phenomena in detail, in particular for rainbow scattering due to single oscillating droplets during free fall, and for light propagation effects through atmospheric paths with turbulences, leading, e.g., to scintillation of stars or shimmering of mirage images.
© 2011 Optical Society of America
Model simulations of laboratory-generated and natural crepuscular rays are presented. Rays are created in the laboratory with parallel light beams that pass through artificial fogs and milk–water solutions. Light scattered by 90° in a dilute mixture of whole milk first increases in intensity with distance from the source to a maximum as a result of multiple scattering by mainly small angles before decreasing exponentially due to extinction as distance continues to increase. Crepuscular rays are simulated for three cloud configurations. In case 1, the Sun at the zenith is blocked by a cloud with an overhanging anvil. The rays appear white against blue sky and are brightest when atmospheric turbidity, β≈11 . Shading by the anvil separates maximum brightness from apparent cloud edge. In case 2, a ray passes through a rectangular gap in a cloud layer. The ray is faint blue in a molecular atmosphere but turns pale yellow as β and solar zenith angle, ϕsun , increase. At ϕsun=60° it appears most striking when the cloud is optically thick, β≈5 , and the beam width Δx≈1000 m . In these cases, increasing aerosol radius, raer , to about 1000 nm brightens, narrows, and shortens rays. In case 3, the twilight Sun is shaded by a towering cloud or mountain. The shaded rays are deeper blue than the sunlit sky because the light originates higher in the atmosphere, where short waves have suffered less depletion from scattering. The long optical path taken by sunlight at twilight makes color and lighting contrasts of the rays greatest when the air is quite clean, i.e., for β−1≪1 . In all cases, the brightest rays occur when sunlight passes through an optical thickness of atmosphere, τ≈O(1) .
© 2011 Optical Society of America
Gasdetektion mit Infrarotkameras ist eine relativ neue Anwendung. Aufgrund der industriellen Bedeutung einiger Gase wurden sensitive Kameras mit Schmalbandfiltern entwickelt. Heute gibt es kommerzielle Systeme für die Detektion flüchtiger Kohlenwasserstoffe, Schwefelhexafluorid und Kohlenmonoxid. In dieser Arbeit werden Laborergebnisse der Detektion von CO2 vorgestellt und potenzielle Anwendungen diskutiert.