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Torres H.,Ac2t Research Gmbh | Horwatitsch D.,AIT Austrian Institute of Technology | Varga M.,Ac2t Research Gmbh | Schuster M.,Aerospace and Advanced Composites GmbH | And 2 more authors.
Tribology International

Metal sheet shearing is a necessary procedure for dimensional control during steel forming. Due to extreme operating conditions, shearing blades suffer from severe wear and need frequent repair, causing high maintenance costs. In order to increase the lifetime of cutting blades, FEM simulation of the metal shearing process was performed, implementing a hybrid friction coefficient based on data obtained from a newly developed forming tribometer. A good correlation was found between the shape of the sheared work piece as predicted by the FEM model and as found in the real application. Finally, a relationship is proposed between stress and temperature distributions as calculated by the simulation and shearing blade areas most affected by wear. © 2014 Elsevier Ltd. All rights reserved. Source

Katsich C.,Ac2t Research Gmbh | Polak R.,Aerospace and Advanced Composites GmbH
Key Engineering Materials

The main aim of this study was to determine the influence of substrate heat treatment on iron and nickel based hardfacings under two and three-body conditions. Commonly used wear resistant tempered steel was used as substrate material. Heat treatment investigations were performed on two Fe-based tool steel alloys (M2 and FeVCrC) and a Ni-based alloy reinforced with WC/W2C (Ni-FTC) deposited by plasma transferred arc technology (PTA), respectively. After hardfacing a heat treatment optimized for tempered steel substrate was performed on hardfaced samples. Microstructure investigations were done by optical microscopy, scanning electron microscopy and hardness measurements. Additionally wear behavior was estimated by dry-sand rubber-wheel test (three-body abrasion) and continuous impact abrasion test (two-body abrasion). Results showed significant influence of heat treatment, due to microstructural changes, on wear performance under 3-body conditions of Fe-based tool steels. This effect was not as pronounced in Ni-based alloy than in types of tool steel. Interestingly, in both M2 tool steel and Ni-based systems heat treatment led to the decrease of the two-body abrasive wear resistance. However, heat treated V-rich tool steel type showed good wear performance in continuous impact abrasion test. Composed wear map, based on this study, shows critical changes in general wear performance for investigated hardfacings. © 2016 Trans Tech Publications, Switzerland. Source

Rojacz H.,Ac2t Research Gmbh | Mozdzen G.,Aerospace and Advanced Composites GmbH | Winkelmann H.,Ac2t Research Gmbh
Materials Characterization

Strain hardening is a common technique to exploit the full potential of materials in diverse applications. Single impact studies were performed to evaluate work hardening effects of different steels, correlated to their deformation at different energy and momentum levels. Three different steels were examined regarding their forming behavior and their tendency to strain harden in impact loading conditions, revealing different intensities of hardness increase, deformation and coinciding microstructural changes. Detailed studies in the deformed zone such as micro hardness mappings were performed to reveal the materials hardness increase in the deformed zones. Additionally high resolution scanning electron microscopy (HRSEM) supported by electron backscatter diffraction (EBSD) was used to determine microstructural changes. Results indicate, that the influence of different velocities/strain rates at constant energy levels cannot be neglected for the strain hardening behavior of steels and provide data for a better control of the hardness increase in impact dominated materials fabrication operations. © 2014 Elsevier Inc. Source

Dunn B.D.,European Space Agency | Mozdzen G.,Aerospace and Advanced Composites GmbH
Soldering and Surface Mount Technology

Purpose: This paper aims to evaluate the morphology and thickness of oxides that form on the surfaces of tin whiskers. The problems related to the growth of tin whiskers are stated, and the relevance of oxide layers adhering to whiskers is discussed. Design/methodology/approach: Modern laboratory methods including focused ion beam sectioning, energy dispersive spectroscopy and X-ray photoelectron spectroscopy have been used to characterise the composition of oxides present on the surfaces of 48-year-old whiskers. These very old whiskers had nucleated and grown on electronic equipment stored at ambient temperatures. They were compared to the oxide layers on newly grown 2-week-old whiskers. Findings: A dual oxide film, consisting of stannous and stannic oxides, was found present on both the old and the new whiskers. Measurements of oxide thickness were established for both generations of whiskers and these were noted to be similar to those films present on pure, cleaned bulk tin. Research limitations/implications: Only very new and very old whiskers, and their oxide films, were the focus of this investigation. However, sufficient data were gained to predict the effect both kinds of oxide films would have during whisker bridging between conductors and the risk of short circuits. Thick oxide films (order of 30 nm) may have a greater resistance to shorting, but they will be more difficult to remove during solder dipping (with respect to whisker mitigation). Practical implications: A knowledge of the oxide thickness on growing/gyrating tin whiskers will provide the electronics industry with data useful for establishing the risk of short circuits. It will also be useful during the forensic work associated with component and assembly failure analysis. Originality/value: The data resulting from this study are unique. They are of value to others who may require knowledge of the morphology, composition and thickness of oxides present on tin whiskers of different vintage. © Emerald Group Publishing Limited. Source

Agency: Cordis | Branch: FP7 | Program: CP | Phase: SPA.2010.2.2-01 | Award Amount: 1.70M | Year: 2011

On spacecrafts reduction of mass and power consumption are a major issue. On the other hand, in case of mechanisms for Solar Arrays or antennas big masses have to be moved and kept in position for long times. Harmonic Drives would fulfil the requirements: high gear ratios enable the use of small actuator motors (low mass and power), they provide high stiffness and high precision even at very low speeds. However, the use is presently limited by the need of grease lubrication. This is linked with risk of outgassing, contamination of other parts and limits the usage in temperatures approx. -50C to \70C. The use of solid lubricants typically for bearings may extremely widen the usage to at least -170C to 300C. First trials to apply these technologies for space use based on commercial available coatings (partially used in space bearings) did not lead to success, due to the strongly differing mechanical and contact situation in the Harmonic Drive. Therefore, project HarmLES will focus on the development of solid lubricant coatings for Harmonic Drives in space. This is seen as an integrated approach between gear design and material adaptation and the application of a suitable coating. It will start with a promising composite coating which has already been tested in space. On the other hand, a huge variety of coatings are available that claim self-lubricating, they will be benchmarked for their applicability in space. Besides space related lab-testing, application testing will ensure the proper feedback. The overall, tribosystem will be re-considered on bases of FEM-simulations and alternative material solutions. An end-user group consisting of several industrial end-users from space will be involved to recommend the research path by defining requirements for later applications. The consortium is small, but it covers the major players and reflects existing expertise in this field to perform the project successfully.

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