Bad Berleburg, Germany
Bad Berleburg, Germany

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Rakette R.,NOXMATGmbH | Mader D.,NOXMATGmbH | Neumann B.,EJOT GmbH and Co. KG
Gaswaerme International | Year: 2017

In the field of process heat utilization, various measures are available for increasing energy efficiency. According to the technological process, a large part of the process heat is generated as waste heat. It is a very effective way of recycling this waste heat directly to the process, e. g. by means of intensive combustion air preheating at industrial burners. The long proven recuperator burners are limited in energy efficiency due to the restriction of the recuperator surface. The use of metal foam in connection with the robust finned tube design generates higher efficiencies which achieve 10-15 % energy savings compared to conventional finned tube recuperator burners.


Bera S.,Indian Institute of Technology Kharagpur | Zuberova Z.,Robert Bosch GmbH | Hellmig R.J.,EJOT GmbH and Co. KG | Estrin Y.,Monash University | Manna I.,Indian Institute of Technology Kharagpur
Philosophical Magazine | Year: 2010

Cu-4.5 wt % Cr and Cu-4.5 wt % Cr-3 wt % Ag alloys, with and without nanocrystalline Al2O3 dispersions (particle size <10 nm), were synthesized by mechanical alloying/milling and consolidated by equal-channel angular pressing (ECAP) at ambient temperature. Microstructural characterization and phase analysis by X-ray diffraction, as well as scanning and transmission electron microscopy, provided evidence for the formation of a Cu-rich extended solid solution with nanometric (<30 nm) crystallite size after 25 h of milling, with uniformly dispersed alumina nanoparticles embedded in it. Consolidation of Cu-4.5 wt % Cr-3 wt % Ag alloy with 10 wt % nanocrystalline Al2O3 by eight ECAP passes was shown to result in a composite with an exceptionally large hardness of 390 VHN and enhanced wear resistance. The electrical conductivity of the pellets of the latter alloy without Al2O3 is about 30% IACS (international annealing copper standard), whereas pellets with 5 or 10 wt % Al2O3 dispersion exhibit a conductivity of about 20-25% IACS. Thus, the present room temperature synthesis and consolidation route appear to offer a promising avenue for developing high-strength, wear/erosion-resistant Cu-based electrical contacts with nano-ceramic dispersion.


Brendler G.,TU Chemnitz | Scharf I.,TU Chemnitz | Hartel M.,EJOT GmbH and Co. KG | Nickel D.,TU Chemnitz | And 3 more authors.
Materialwissenschaft und Werkstofftechnik | Year: 2011

The realization of hybrid constructions in the automotive and aerospace industry is posing new challenges to screw joints. Anodized high-strength aluminium screws are intended to replace thread-forming steel screws and prevent the corrosion of material compounds. The corrosion and wear resistance as well as the screw-in behaviour of anodized aluminium screws with respect to the selected processes of direct or liquid contacting has been studied. The hard anodized screws are corrosion- and wear resistant and suitable for direct assembly. The results indicate that specific surface treatment can extend the scope of application of anodized aluminium screws considerably. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Grober D.,TU Chemnitz | Georgi W.,TU Chemnitz | Sieber M.,TU Chemnitz | Scharf I.,TU Chemnitz | And 4 more authors.
International Journal of Fatigue | Year: 2015

Self-tapping aluminium screws are an innovative joining technology for the assembly of lightweight components in industrial scale. It has been established in the past that porous anodic oxide coatings in many cases reduce the fatigue strength of specimens without notches. In the present work, the fatigue behaviour of notched specimens, i.e. self-tapping screws made from aluminium alloys EN AW-6056, 6082 (both in a conventional state and in a fine-grained state produced by equal channel angular pressing - ECAP) and 7068 with and without oxide coatings is examined. The coatings are produced by hard anodising and are necessary for the thread-forming process during assembly. While the coatings do not affect the static tensile strength, they reduce the fatigue strength for the specimens of the 6056 and the 6082 alloy. For the 7068 alloy a slight increase in fatigue strength is discovered on a low load horizon. The scatter of endured fatigue cycles until fracture of specimens is generally reduced by the anodic oxide coatings. © 2015 Elsevier Ltd. All rights reserved.


Merken D.,Friedrich - Alexander - University, Erlangen - Nuremberg | Drummer D.,Friedrich - Alexander - University, Erlangen - Nuremberg | Kobes M.O.,Friedrich - Alexander - University, Erlangen - Nuremberg | Kunkel R.,EJOT Gmbh and Co. KG | Kornsteiner W.,EJOT Schweiz AG
Zeitschrift Kunststofftechnik/Journal of Plastics Technology | Year: 2011

Assembly injection moulding can be used to economically produce friction-locked coupling compo-nents, e.g. for overload protection. To realize the potential of this application successfully, a systemat-ic consideration of the aspects material, part design and processing is necessary. In this paper, si-mulative and analytical approaches for designing of assembly injection moulded friction-clutches are presented. © Carl Hanser Verlag.


Wick D.,University of Siegen | Wick D.,EJOT GmbH and Co. KG | Wick T.,Austrian Academy of Sciences | Wick T.,TU Munich | And 3 more authors.
Computational Materials Science | Year: 2015

Abstract In this work, we consider a phase-field framework for crack propagation problems in elasticity and elasto-plasticity. We propose a rate-dependent formulation for solving the elasto-plastic problem. An irreversibility constraint for crack evolution avoids non-physical healing of the crack. The resulting coupled two-field problem is solved in a decoupled fashion within an augmented Lagrangian approach, where the latter technique treats the crack irreversibility constraint. The setting is quasi-static and an incremental formulation is considered for temporal discretization. Spatial discretized is based on a Galerkin finite element method. Both subproblems of the two-field problem are nonlinear and are solved with a robust Newton method in which the Jacobian is built in terms of analytically derived derivatives. Our algorithmic developments are demonstrated with several numerical tests that are motivated by experiments that study failure of screws under loading. Therefore, these tests are useful in practice and of high relevance in mechanical engineering. The geometry and material parameters correspond to realistic measurements. Our goal is a comparison of the final crack pattern in simulation and experiment. © 2015 Elsevier B.V.


Scharf I.,TU Chemnitz | Hellmig R.J.,EJOT GmbH and Co. KG | Nickel D.,TU Chemnitz | Hartel M.,EJOT GmbH and Co. KG | Lampke T.,TU Chemnitz
Materialwissenschaft und Werkstofftechnik | Year: 2010

The use of high-strength Al screws is of particular interest with regard to lightweight construction and its respective economic and ecological aspects. The subject of the project T1 is the transfer of different surface treatments that have been classified promising in fundamental experiments into industrial assessment and application. The focus is on protective coatings which develop from the substrate (anodizing). This process group offers the potential to obtain the required surface refinement of the Al screws. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Sieber M.,TU Chemnitz | Scharf I.,TU Chemnitz | Hartel M.,EJOT GmbH and Co. KG. | Hellmig R.J.,EJOT GmbH and Co. KG. | Lampke T.,TU Chemnitz
Materialwissenschaft und Werkstofftechnik | Year: 2012

Enhanced use of lightweight materials, namely aluminium and magnesium, requires the application of appropriate production techniques. Self-tapping screws represent an innovative joining technology. High-strength aluminium alloys can be used as screw material. Stringent requirements regarding the wear resistance of screw surfaces result from the thread-forming process. These requirements are met by oxide ceramic conversion layers produced by hard anodizing. Based on application-oriented testing methods, the influence of hard anodized layers on the screwing behaviour and susceptibility to stress corrosion cracking of high-strength aluminium screws is examined. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


The invention relates to a screw having a head, an adjoining retaining section and a functional tip for use as a self-tapping screw. The functional tip is of greater hardness than the retaining section. The entire screw is made of hardened low-alloy carbon steel. The special feature of this screw is that its functional tip has a higher carbon and/or nitrogen content than its retaining section

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