Papers by Keyword: Microstructuring

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Authors: Jenny Andersson, P. Hollman, S. Jacobson
Authors: Yasuhiro Takada, Mitsuru Shinozaki, Minoru Ota, Kai Egashira, Keishi Yamaguchi, Yoshitaka Hattori
Abstract: Whirling electrical discharge texturing (WEDT) was developed to process microstructures on the inner surface of cylindrical parts made of high hardness materials. However, the minimum processable diameter of the cylindrical parts was φ 5 mm and the equipment could not feed the new tool electrodes. Therefore, the authors devised a novel method of WEDT using a straight wire tool electrode for a cylindrical surfaces with a small diameter. It was confirmed that microstructures could be created on the inner surface of a cylinder of φ 1.1 mm diameter, and that the texture-area ratio could be controlled by the workpiece feed speed. Moreover, new EDT equipment with a feeding system for a wire tool electrode and a bending system for the tip of a wire tool electrode was developed. As a result, the equipment that can process microstructures on the inner surface of a cylinder with a small diameter and feed a wire tool electrode during texturing was successfully developed.
Authors: Peter Scholz, Richard Börner, Ralf Kühn, Roland Müller, Andreas Schubert
Abstract: In the sheet metal forming industry lubricants are applied in forming processes to expand the technological boundaries by reducing friction and wear. The friction between tool and sheet metal is crucial to the deep drawing process. Due to economic and ecological reasons the aim of the manufacturers is to reduce or even avoid the use of lubricants. Consequently, this approach enables both a shortening of the process chains and an essential saving of resources. The advantages of structured forming tools in lubricated processes concerning the reduction of the coefficient of friction by the appearance of lubricating micro pockets are well-known. However, without using any lubricant this effect does not work. In this case the contact area is reduced by structuring the forming tool which affects the tribological system.In this paper the influence of microstructures with different geometries and surface treatments (uncoated / a-C:H:Si-coating) on the coefficient of friction in dry metal forming of the alloy AA5182 is compared to the frictional behaviour of unstructured forming tools using lubricant as reference. Before coating, the forming tools are machined by milling to generate tribologically effective microstructures. With the use of a strip drawing plant the effects of different surface microstructures and materials on the coefficient of friction are investigated.
Authors: Zhi Qing Hu, Ji Zhao, Zeng Ming Feng
Abstract: Micro-structured surfaces with drag reduction, desorption, and excellent optical performance are widely used in the field of automotive, aerospace, marine applications. Therefore, the manufacturing of the micro-structure on the metal surface is of high impotance. Although the processing methods for micro-patterning of surfaces have progressed in recent years, micro-structure processing is still not used on large metal surfaces. In this paper, a method of roll forming micro-structure on the plate surface is proposed. A simulation model for micro-structure roll forming (MRF) was presented by using three-dimensional finite element method (FEM). The strain and stress, and the displacements caused by micro-structure were analyzed. The results provide theoretical guidance for the design of different micro-structures and the sequence of their processing.
Authors: J. Hauptmann, G. Wiedemann
Authors: Andreas Schubert, Philipp Steinert, Torsten Schmidt, Matthias Hackert-Oschätzchen
Abstract: Among the major interests in powertrain development are the reduction of frictional losses and service life extension from improved wear resistance. Surface finishing and deterministic microstructuring have been shown to be effective methods in improving the tribological properties of sliding contacts such as bearings and cylinder liners. This is due to their acting as micro pressure-chambers and as wear debris traps. In this work, tribometric ring-on-disc tests were performed in order to evaluate the influence of surface structure − namely, the microstructure geometry and layout − on the frictional behavior of lubricated surfaces. The material combination bronze against steel as typically used in powertrain applications was investigated. The surface structures where machined using electrochemical machining by closed electrolytic free jet (Jet-ECM). It was determined that microstructuring reduced the friction coefficient by up to 45 % in the hydrodynamic regime under loads and speeds found in automotive components. The friction measurements showed that microstructures with low aspect ratios result in the least friction. In addition to the tribological investigations, the process capabilities and implementability in serial production of two surface microstructure fabrication processes: Jet-ECM and a newly developed, hybrid roller micro-embossing and burnishing process were evaluated and contrasted. It was shown that both fabrication methods can attain high structure quality.
Authors: Vitchuda Lertphokanont, Takayuki Sato, Minoru Ota, Keishi Yamaguchi, Kai Egashira
Abstract: The authors developed Whirling Electrical Discharge Texturing (WEDT) in order to reduce friction coefficient of cylinder-shaped parts. In previous research, the authors verified fundamental characteristics of WEDT by observation of textured surface. It was found that a crater shape and texture-area ratio can be controlled by WEDT. The texture-area ratio depends on feed speed of tool electrode. In this research, crater depth, crater diameter, texture area ratio and total removal volume of craters were investigated to confirm characteristics of WEDT in detail. In addition, tungsten wire was used as a whirling shaft in order to improve stability of whirling phenomenon. Moreover, a textured surface was finished by lapping-film in order to remove protrusions around craters and reduce friction coefficient. As a result, it was verified that the texture-area ratio slightly increased with decreasing feed speed and it was confirmed that crater depth, crater diameter, and total removal volume of craters were also related to feed speed.
Authors: Peter Bechtold, Godehard Mayer, Patrick Lühring, Michael Schmidt
Abstract: In laser materials processing, trepanning optics are used to fabricate laser drilled holes of high aspect ratios (> 10) and controllable drill-hole conicity. However, trepanning optics available up to today are limited to circular trepanning geometries. Thus, only circular holes with drill-hole wall angles of rotational symmetry are feasible. Within this paper we will present a novel trepanning optic based on two piezo-actuatoric tip/tilt mirrors, being first of its kind, which allows arbitrary developments of propagation angle and lateral position of the laser beam, both being independent of each other. Consequently, the novel trepanning optic allows arbitrary drill-hole geometries such as circular, elliptical, rectangular etc. At the same time the drill-hole wall angle may be varied freely. Thus, asymmetric drill-hole wall angles are feasible such as tilt of the drill hole or wobbling of the drill-hole wall angle for instance. Demonstrative drill-holes of different shapes produced with an ultrashort pulsed laser prove the flexibility of the trepanning optic presented.
Authors: Florian Zeller, Nirdesh Ojha, Claas Müller, Holger Reinecke
Abstract: Silicon carbide (SiC) is a high performance ceramic material which is increasingly used in applications which demand for high temperature stable materials. The microstructuring of this material in its sintered state is a challenge for conventional machining methods due to its extraordinary mechanical properties. To overcome these limitations the process of electrical discharge machining (EDM) was modified with a so called assisting electrode (AE) to enable the structuring of non-conductive ceramics such as SiC. This paper presents a parametric analysis of micro electrical discharge milling process of non-conductive SiC for two different tool materials, tungsten carbide (WC) and copper (Cu). A full factorial design with four factors was conducted. The significant factors are shown with main effects plots. Two sets of optimized parameters for maximum material removal rate (MRR) and minimum tool wear rate (TWR) for both tool materials are presented. Hardness and surface roughness are measured and compared to the non-machined material.
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