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Garbsen, Germany

Gaebel C.M.,An der University 2
Advanced Materials Research | Year: 2013

The application of ground and satin stainless steel sheet metal with anti-fingerprint coating is well established in the household appliance industry. In essence, they reduce the adhesion and visibility of fingerprints on satin stainless steel surfaces and improve the cleaning characteristics. The thickness of these imperceptible clear coatings amounts to a few micrometers. They are applied by the stainless steel manufacturer in a coil coating process. The required high hardness and scratch resistance is achieved by an ultraviolet radiation curing procedure and a nanoparticle reinforced coating system. The final painted sheets are further processed e.g. to covering panels of white goods. During forming operations a damage of the clear coating results in the form of crack formation and delamination. But due to the optical properties of the coating systems specifically adjusted to ground stainless steel surfaces, the damage in the clear coating is difficult to identify. This paper deals with the identification of the deformation induced coating damage on the bending edges of a typical covering panel geometry. The experiments show an influence on the coating damages resulting from the grinding direction and the use of a deep drawing foil. Furthermore, panels are formed at higher temperatures with an effect on the coating damages. In addition, mandrel bending specimens are formed. Due to different bending radii and orientations of the grinding direction the damage varies. These specimens are also examined in a salt spray test to analyze the influence of the coating damage degree on the corrosion resistance. © (2013) Trans Tech Publications, Switzerland. Source

Akin M.,An der University 2 | Rissing L.,An der University 2
Proceedings - Electronic Components and Technology Conference | Year: 2015

Driven by low-cost, resource abundance and distinct material properties, the use of paper in electronics, optics and fluidics is under investigation. In order to realize a dense coverage of sensor networks as part of the roadmap of the internet-of-things, achieving lower manufacturing cost of the aforementioned sensors is required. Considering microelectro-mechanical systems based on magneto-resistance principles (anisotropic, giant, tunnel) that are conventionally manufactured onto inorganic semiconductor materials, we propose the use of paper substrates for cost reduction purposes primarily. In particular, we studied the magneto-resistance sensitivity of permalloy (Py:Ni81Fe19) onto paper substrates utilized in various daily applications. Here, the Py:Ni81Fe19 coating was developed by means of, but not limited to, sputter deposition, and spans an area of 10x10 mm2 and a thickness of 70 nm. In this research, we investigated several paper materials covering a range of grammage of [80, 350] g/m2, surface roughness of [0.21, 3.462] μm given by the root mean squared Rims, various impregnations, porosity levels and surface macro-structures. Yet, in this paper, we focus on our findings with clean room paper (80 g/m2, Rrms = 2.877 μm, 23% surface porosity, latex impregnation, no embossed macro-structure). Employing a four-point-probe resistivity measurement setup, we investigated the change of electrical resistance of Py:Ni81Fe19 under the presence of an oriented external magnetic field. Compared to the theoretical limit of 2.5% of Py:Ni81Fe19 on smooth surfaces, we have obtained large and positive magneto-resistive changes (2.5 - 14%) for these aforementioned systems. Principally, we analyzed the effect of surface topology of the clean room paper on the magneto-resistance sensitivity of Py:Ni81Fe19. We concluded that the occurrence of such magnetic behavior is most probably due to tunneling of electron waves through the asperities and porosity of the paper surface and subsequent scattering of electrons at pinned domain walls. © 2015 IEEE. Source

Denkena B.,An der University 2 | Gummer O.,An der University 2
Production Engineering | Year: 2012

For economical reasons it is necessary to reduce the machining time and to increase the process automation. This leads to the need for fast machine tools with high process stability in order to enhance the material removal rate. However, the machine often does not limit the process stability but the tool because of its compliance. This paper presents a new possibility of expanding the stable process range of long and slender end mills with an adaptronic spindle system. The system is able to position the spindle dynamically in the range of microns with three piezo actuators. In order to disturb the regenerative effect, which leads to an instable process, the chip thickness is modulated by a dynamic spindle actuation. This is realized by a superposition of vibrations of the tool in feed direction. In milling tests the degree of stabilization is verified for different superpositions. Hence, the stable process range could be improved for spindle speeds up to 5,000 rpm. © 2012 German Academic Society for Production Engineering (WGP). Source

Denkena B.,An der University 2 | Grove T.,An der University 2 | Maiss O.,An der University 2
Procedia CIRP | Year: 2016

The endurance of highly loaded parts such as bearings is influenced by their surface integrity. Low surface roughness and high compressive residual stresses lead to an increased lifetime. In contrast to grinding and honing, the processes hard turning and deep rolling can induce compressive residual stresses up to σ = -1000 MPa with depths of d0 = 500 μm in combination with surface roughness values of Rz < 0.8 μm. Combining both processes to the innovative hybrid turn-rolling exhibits benefits with respect to topography and residual stress stability. Developing this process, the interactions of the single processes are analyzed in this paper. © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license. Source

Denkena B.,An der University 2 | Grove T.,An der University 2 | Behrens L.,An der University 2
Production Engineering | Year: 2015

PCBN offers high potentials in turning or milling of ferrous materials and highly heat resistant materials. Due to its thermal stability PCBN achieves a longer tool life than PCD despite its lower hardness. These properties currently lead to high production costs of the PCBN inserts. Generally, plunge face grinding with diamond grinding cup wheels is the final machining step in the process chain of the PCBN-insert production. The grinding process of PCBN inserts is characterized by a high amount of grinding wheel wear from the first contact. Normally the ratio between the worn grinding layer and the material removal is lower than one. To increase the productivity the relationships between grinding wheel properties, process parameters and PCBN insert specifications have to be obtained. In an initial step the main factors on the grinding wheel wear and cutting mechanisms are determined. The statistically evaluated results show, that the productivity of the grinding process can be adjusted independently of the achieved PCBN inserts. The process parameters affects only the productivity in the considered area. High insert qualities like sharp cutting edges and low roughness values on the flank face can be produced by the use of small abrasive grains. © 2015, German Academic Society for Production Engineering (WGP). Source

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