Foundation Institute for Material Science

Bremen, Germany

Foundation Institute for Material Science

Bremen, Germany
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Hasselbruch H.,Foundation Institute for Material Science | Herrmann M.,University of Bremen | Mehner A.,Foundation Institute for Material Science | Kuhfuss B.,University of Bremen | Zoch H.-W.,Foundation Institute for Material Science
Procedia Manufacturing | Year: 2017

Rotary swaging is an incremental cold forging process with very short cycle times for manufacturing of complex bar or tube profiles such as axles or gear shafts made of steel or aluminum alloys. Conventional rotary swaging requires high amounts of lubricants usually made of crude oil. Dry rotary swaging would improve the ecological balance of this process considerably and would also accelerate the process due to cleaning of the manufactured components after processing becomes obsolete. This study deals with a first benchmark of dry rotary swaging as a function of macro and micro-structured tool surfaces coated with wear resistant and low friction a-C:H:W coating systems with respect to the resulting workpiece quality and tribological process conditions. In addition, the influence of a surface finishing is investigated related to the dominating and locally changing coating wear mechanisms. The presented results allow for further coating development towards dry rotary swaging. © 2017 The Authors


Ellendt N.,University of Bremen | Stelling O.,Foundation Institute for Material Science | Uhlenwinkel V.,University of Bremen | Von Hehl A.,Foundation Institute for Material Science | Krug P.,PEAK Werkstoff GmbH
Materialwissenschaft und Werkstofftechnik | Year: 2010

Due to high cooling rates spray forming is an appropriate process to produce aluminum alloys with a high content of Mg2Si. Compared to common casting processes, a fine microstructure can be achieved yielding in improved mechanical properties. In this work, billets were spray formed from the two alloys AlMg15Si8Cu2 (22 mass-% Mg2Si) and AlMg20.5Si11Cu2 (30 mass-% Mg2Si) under different spraying conditions. The analysis of the microstructure showed that the size of Mg2Si dispersoids is very sensitive to process parameters. Besides the well known thermal effects of melt superheat (carried out from -40 K to +170 K) and GMR (varied from 2.0 to 6.3) a strong influence of the scanning frequency of the atomizer nozzle (7 Hz and 15 Hz) could be observed. Similar effects could be found for the occurrence of porosity. A new parameter, the enthalpy flow to gas flow ratio (EGR), was defined from these two parameters of which correlations of Mg2Si dispersoid size and amount of porosity were found. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Ibragimov A.,University of Bremen | Uhlenwinkel V.,Foundation Institute for Material Science | Ellendt N.,Foundation Institute for Material Science | Madler L.,Foundation Institute for Material Science | Lang W.,University of Bremen
2013 Transducers and Eurosensors XXVII: The 17th International Conference on Solid-State Sensors, Actuators and Microsystems, TRANSDUCERS and EUROSENSORS 2013 | Year: 2013

A new silicon based thermogenerator with a reduced parasitic contact resistivity and respectively a broad working range from 250°K up to 1000°K is presented. The reduction of the contact resistivity was achieved due to changes in the contact pads geometry including implementation of three-dimensional contacts as well as altering of their characteristic by additional dopant diffusion. The resulting thermogenerator was embedded in metal using the method of metal-spray-deposition, which ensures high yield of the successfully embedded thermogenerators (30 functional of the total of 32) due to relatively low mechanical forces applied during the embedding process and reduced thermomechanical stress during the following cool-down phase. © 2013 IEEE.


Ibragimov A.,University of Bremen | Uhlenwinkel V.,Foundation Institute for Material Science | Ellendt N.,Foundation Institute for Material Science | Madler L.,Foundation Institute for Material Science | Lang W.,University of Bremen
Sensors and Actuators, A: Physical | Year: 2014

A new silicon-based thermogenerator with a reduced parasitic contact resistivity and a large temperature working range from 250 K up to 1000 K is presented. Three-dimensional contact geometry and additional doping reduces the contact resistivity from 12.7 MΩ μm2 to 57.6 kΩ μm2. In this way, for all temperatures above 250 K the contact resistivity is negligible with respect to the inner resistivity of the thermoelectric materials. At room temperature it is only 1% of the total resistivity. The thermogenerator was embedded in metal using the method of metal-spray-deposition, which ensures high yield of the successfully embedded thermogenerators (30 functional of the total of 32) due to relatively low mechanical forces applied during the embedding process and reduced thermo-mechanical stress during the following cool-down phase. Our results demonstrate that it is possible to embed silicon microsystems in metals during high-temperature metallurgic primary forming processes. © 2014 Elsevier B.V.


Brinksmeier E.,Foundation Institute for Material Science | Eckebrecht J.,Foundation Institute for Material Science | Wilkens A.,Foundation Institute for Material Science
Advanced Materials Research | Year: 2011

The chip removal process in grinding is characterized by intensive friction and plastic deformation leading to the risk of thermal damage of the surface-layer of the machined part. Thus productive and reliable grinding processes need effective monitoring. The difficult to access contact zone between the grinding wheel and the workpiece led to extensive research work on the temperature measurement in the grinding arc. In order to develop a tool integrated temperature monitoring system a new approach was undertaken which makes use of the measurement of infrared-radiation to monitor the temperatures in the grinding arc. The presented research work shows promising results suitable for an industrial applicable system for temperature measurement in grinding. The optical transmission of the infrared temperature information in combination with a fast detecting infrared sensor bares the potential to establish a highly miniaturized measuring system which is easy to integrate in any grinding wheel at comparably low production costs. © (2011) Trans Tech Publications, Switzerland.

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