TY - JOUR A1 - Reisgen, Uwe A1 - Schleser, Markus A1 - Mokrov, Oleg A1 - Ahmed, Essam T1 - Uni- and bi-axial deformation behavior of laser welded advanced high strength steel sheets JF - Journal of materials processing technology N2 - Bead-on-plate butt joints of 2.5 mm hot rolled DP600/DP600 and 1.2 mm cold rolled TRIP700/TRIP700 steel sheets were performed using 6 kW CO2 laser beam welding. The welding speed ranged from 1.5 to 3.0 and from 2.1 to 3.9 m/min in DP/DP and TRIP/TRIP steel weldments respectively. A top surface helium gas was used as a shielding gas at a flow rate of 20 l/min. Metallographic examinations and transverse tensile testing (DIN EN 895: 1995) were carried out to characterize the weldments. The formability of base metals and weldments were investigated by standard Erichsen test (DIN EN ISO 20482). It was found that the uniaxial plastic behavior of both DP600 and TRIP700 base metals was in agreement with Swift and modified Mecking–Kocks models respectively. In a perpendicular tensile test to the weld line, all specimens were fractured at the base metal however the strengths were somewhat higher than those of base metal. There was a significant reduction in formability caused by welding of both DP/DP and TRIP/TRIP steel weldments and the formability has been improved with the increase of the welding speed. Y1 - 2010 U6 - https://doi.org/http10.1016/j.jmatprotec.2010.08.003 SN - 0924-0136 VL - 210 IS - 15 SP - 2188 EP - 2196 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Reisgen, Uwe A1 - Schleser, Markus A1 - Mokrov, Oleg A1 - Ahmed, Essam T1 - Shielding gas influences on laser weldability of tailored blanks of advanced automotive steels JF - Applied surface science N2 - The effects of shielding gas types and flow rates on CO2 laser weldability of DP600/TRIP700 steel sheets were studied in this work. The evaluated shielding gases were helium (He), argon (Ar) and different mixtures of He and Ar. Weld penetration, tensile strength and formability (Erichsen test) of laser welds were found to be strongly dependent upon the shielding gas types. The ability of shielding gas in removing plasma plume and thus increasing weld penetration is believed to be closely related to ionization potential and atomic weight which determine the period of plasma formation and disappearance. It was found that the higher helium shielding gas flow rate, the deeper weld penetration and the lower weld width. Y1 - 2010 U6 - https://doi.org/10.1016/j.apsusc.2010.08.042 SN - 0169-4332 (E-Journal); 0169-4332 (Print) VL - 257 IS - 5 SP - 1401 EP - 1406 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Reisgen, Uwe A1 - Schleser, Markus A1 - Jerabek, Jakub A1 - Chudoba, Rostislav T1 - Messung der Strahlqualität einer Elektronenstrahlanlage in Umgebungsatmosphäre JF - Materialwissenschaft und Werkstofftechnik N2 - In den letzten Jahrzehnten hat das Elektronenstrahlschweißen, das bereits im größeren Maßstab verwendet wird, seine Fähigkeit als qualitatives Werkzeug für die Verbindung verschiedener Materialen nachgewiesen. Das Non Vacuum Electron Beam Welding (NV-EBW) hat zahlreiche Vorteile im Vergleich zum Elektronenstrahlschweißen im Vakuum, da man unter normalem Atmosphärendruck arbeiten kann. Im Hinblick auf die reproduzierbare Qualität, insbesondere im Bereich der Massen-Fertigung, ist die Kontrolle der Strahlparameter sowie deren Einfluss auf das Schweißergebnis von großer Bedeutung. Durch eine genaue Kenntnis der Strahlkenngrößen wie des Strahldurchmessers und der Leistungsdichteverteilung kann eine Aussage über die sich ausbildende Schweißnaht sowie die Schweißbaddynamik getroffen werden. Messungen der Strahlkenngrößen im Prozess erlauben insbesondere die Untersuchung von Humping-Effekten. In diesem Beitrag wird der Prozess der Elektronenstrahlvermessung unter atmosphärischen Bedingungen beschrieben. Es wird zudem die Abhängigkeit der Elektronenstrahlcharakteristika von den verschiedenen Prozessparametern dargestellt. Y1 - 2010 SN - 1521-4052 VL - 41 IS - 1 SP - 45 EP - 52 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Reisert, Steffen A1 - Henkel, Hartmut A1 - Schneider, Andreas A1 - Schäfer, Daniel A1 - Friedrich, Peter A1 - Berger, Jörg A1 - Schöning, Michael Josef T1 - Development of a handheld sensor system for the online measurement of hydrogen peroxide in aseptic filling systems JF - Physica Status Solidi (A). 207 (2010), H. 4 Y1 - 2010 SN - 1862-6300 N1 - Special Issue: Engineering of Functional Interfaces EnFI 2009 SP - 913 EP - 918 ER - TY - JOUR A1 - Recker, Elmar A1 - Bosschaerts, Walter A1 - Wagemakers, Rolf A1 - Hendrick, Patrick A1 - Funke, Harald A1 - Börner, Sebastian T1 - Experimental study of a round jet in cross-flow at low momentum ratio JF - 15th International Symposium on Applications of Laser Techniques to Fluid Mechanics Lisbon, Portugal, 05-08 July, 2010 - 1 Y1 - 2010 SP - 1 EP - 13 ER - TY - JOUR A1 - Probst, M. A1 - Behbahani, Mehdi A1 - Borrmann, E. A1 - Elgeti, S. A1 - Nicolai, M. A1 - Behr, M. T1 - Hemodynamic Modeling for Numerical Analysis and Design of Medical Devices Y1 - 2010 N1 - Posterpresentation ; NIC Symposium 2010 ; 24 - 25 February 2010 Jülich, Germany ER - TY - JOUR A1 - Pressler, Axel A1 - Esefeld, Katrin A1 - Scherr, Johannes A1 - Ali, Mohammad A1 - Hanssen, Henner A1 - Kotliar, Konstantin A1 - Lanzl, Ines A1 - Halle, Martin A1 - Kaemmerer, Harald A1 - Schmidt-Trucksäss, Arno A1 - Hager, Alfred T1 - Structural alterations of retinal arterioles in adults late after repair of aortic isthmic coarctation JF - The American Journal of Cardiology N2 - Patients after coarctation repair still have an increased risk of cardiovascular or cerebrovascular events. This has been explained by the persisting hypertension and alterations in the peripheral vessels. However, involvement of the central vessels such as the retinal arteries is virtually unknown. A total of 34 patients after coarctation repair (22 men and 12 women; 23 to 58 years old, age range 0 to 32 years at surgical repair) and 34 nonhypertensive controls underwent structural and functional retinal vessel analysis. Using structural analysis, the vessel diameters were measured. Using functional analysis, the endothelium-dependent vessel dilation in response to flicker light stimulation was assessed. In the patients after coarctation repair, the retinal arteriolar diameter was significantly reduced compared to that of the controls (median 182 μm, first to third quartile 171 to 197; vs 197 μm, first to third quartile 193 to 206; p <0.001). These findings were independent of the peripheral blood pressure and age at intervention. No differences were found for venules. The functional analysis findings were not different between the patients and controls (maximum dilation 3.5%, first to third quartile 2.1% to 4.5% vs 3.6%, first to third quartile 2.2% to 4.3%; p = 0.81), indicating preserved autoregulative mechanisms. In conclusion, the retinal artery diameter is reduced in patients after coarctation repair, independent of their current blood pressure level and age at intervention. As a structural marker of chronic vessel damage associated with past, current, or future hypertension, retinal arteriolar narrowing has been linked to stroke incidence. These results indicate an involvement of cerebral microcirculation in aortic coarctation, despite timely repair, and might contribute to explain the increased rate of cerebrovascular events in such patients. Y1 - 2010 U6 - https://doi.org/10.1016/j.amjcard.2009.10.070 SN - 0002-9149 VL - 105 IS - 5 SP - 740 EP - 744 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Poghossian, Arshak A1 - Wagner, Holger A1 - Schöning, Michael Josef T1 - Automatisiertes „wafer level“-Testsystem zur Charakterisierung von siliziumbasierten Chemo- und Biosensoren JF - Tagungsband: Sensoren und Messsysteme 2010 N2 - Es wurde ein automatisiertes, computerunterstütztes Testsystem für die Funktionsprüfung und Charakterisierung von (bio-)chemischen Sensoren auf Waferebene entwickelt und in einen konventionellen Spitzenmessplatz integriert. Das System ermöglicht die Charakterisierung und Identifizierung „funktionstauglicher“ Sensoren bereits auf Waferebene zwischen den einzelnen Herstellungsschritten, wodurch weitere, bisher übliche Verarbeitungsschritte wie das Fixieren, Bonden und Verkapseln für die defekten oder nicht funktionstauglichen Sensorstrukturen entfällt. Außerdem bietet eine speziell entworfene miniaturisierte Durchflussmesszelle die Möglichkeit, bereits auf Waferlevel die Sensitivität, Drift, Hysterese und Ansprechzeit der (bio-)chemischen Sensoren zu charakterisieren. Das System wurde exemplarisch mit kapazitiven, pH-sensitiven EIS- (Elektrolyt-Isolator-Silizium) Strukturen und ISFET- (ionensensitiver Feldeffekttransistor) Strukturen mit verschiedenen Geometrien und Gate-Layouts getestet. Y1 - 2010 SN - 978-3-8007-3260-9 N1 - Sensoren und Messsysteme 2010 - 15. ITG/GMA-Fachtagung, 18.05.2010 - 19.05.2010 in Nürnberg SP - 89 EP - 92 PB - VDE Verlag CY - Berlin ER - TY - JOUR A1 - Pieper, Martin A1 - Klein, Peter T1 - Numerical solution of the heat equation with non-linear, time derivative-dependent source term JF - International Journal for Numerical Methods in Engineering N2 - The mathematical modeling of heat conduction with adsorption effects in coated metal structures yields the heat equation with piecewise smooth coefficients and a new kind of source term. This term is special, because it is non-linear and furthermore depends on a time derivative. In our approach we reformulated this as a new problem for the usual heat equation, without source term but with a new non-linear coefficient. We gave an existence and uniqueness proof for the weak solution of the reformulated problem. To obtain a numerical solution, we developed a semi-implicit and a fully implicit finite volume method. We compared these two methods theoretically as well as numerically. Finally, as practical application, we simulated the heat conduction in coated aluminum fibers with adsorption in the zeolite coating. Copyright © 2010 John Wiley & Sons, Ltd. Y1 - 2010 U6 - https://doi.org/10.1002/nme.2937 SN - 0029-5981 VL - 84 IS - 10 SP - 1205 EP - 1221 PB - Wiley CY - Chichester ER - TY - JOUR A1 - Pham, Phu Tinh A1 - Vu, Khoi Duc A1 - Tran, Thanh Ngoc A1 - Staat, Manfred T1 - A primal-dual algorithm for shakedown analysis of elastic-plastic bounded linearly kinematic hardening bodies Y1 - 2010 N1 - ECCM 2010, IV European Conference on Computational Mechanics, Paris, France, May 16-21, 2010. SP - 1 EP - 7 ER -