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Dillingen an der Donau, Germany

DiRienzo A.L.,University of Wyoming | Yakacki C.M.,University of Colorado at Denver | Frensemeier M.,Leibniz Institute for New Materials | Schneider A.S.,AG der Dillinger Huttenwerke | And 3 more authors.
Journal of the Mechanical Behavior of Biomedical Materials | Year: 2014

The focus of this study was to fabricate and investigate the mechanical behavior of porous poly(para-phenylene) (PPP) for potential use as a load-bearing orthopedic biomaterial. PPPs are known to have exceptional mechanical properties due to their aromatic backbone; however, the manufacturing and properties of PPP porous structures have not been previously investigated. Tailored porous structures with either small (150-250. μm) or large (420-500. μm) pore sizes were manufactured using a powder-sintering/salt-leaching technique. Porosities were systematically varied using 50 to 90. vol%. Micro-computed tomography (μCT) and scanning electron microscopy (SEM) were used to verify an open-cell structure and investigate pore morphology of the scaffolds. Uniaxial mechanical behavior of solid and porous PPP samples was characterized through tensile and compressive testing. Both modulus and strength decreased with increasing porosity and matched well with foam theory. Porous scaffolds showed a significant decrease in strain-to-failure (<4%) under tensile loading and experienced linear elasticity, plastic deformation, and densification under compressive loading. Over the size ranges tested, pore size did not significantly influence the mechanical behavior of the scaffolds on a consistent basis. These results are discussed in regards to use of porous PPP for orthopedic applications and a prototype porous interbody fusion cage is presented.© 2013 Elsevier Ltd. Source

Weyand S.,Saarland University | Britz D.,Saarland University | Rupp D.,AG der Dillinger Huttenwerke | Mucklich F.,Saarland University
Materials Performance and Characterization | Year: 2015

The thermo-mechanical simulator Gleeble 3800 was used in combination with the electron backscattered diffraction (EBSD) technique to analyze the austenite microstructure evolution during hot deformation in a low-carbon, microalloyed steel. The parent austenite grain structure was automatically reconstructed from EBSD datasets by applying the commercially available ARPGE software [Cayron, C., Artaud, B., and Briottet, L., "Reconstruction of Parent Grains from EBSD Data," Mater. Charact., Vol. 57, Nos. 4-5, 2006, pp. 386-401]. The work aims at two aspects: the ability to quantify the austenite evolution depending on different process parameters, and the validation of the EBSD reconstruction software ARPGE to evaluate the accuracy of reconstruction and demonstrating the application in low-carbon steels. For these steels, the conventional metallographic methods like Bechet-Beaujard [Bechet, S. and Beaujard, L., "Nouveau réactif pour la mise en évidence micrographique du grain austénitique des aciers trempés ou trempés-revenus," Rev. Met., 1955] are limited and not reproducible in determining the former austenite. The presented approach provides an attractive alternative. In this context, hot compression tests were performed on cylindrical samples using a Gleeble 3800 simulator to create defined austenite conditions. The samples were rapidly quenched after processing to preserve the austenite microstructure. The obtained bainitic/martensitic microstructure is an essential precondition for the reconstruction procedure. For the validation of the results, correlative measurements using classical metallographic techniques and ARPGE data were performed to check the reliability of the reconstruction. The results obtained in this study provide a direct correlation of the microstructure simulation by Gleeble and the austenite microstructure evolution during processing of low-carbon steels. Especially, austenite grain-growth phenomena and grain refinement could be successfully observed and quantified. Furthermore, the measurements show that even on large EBSD maps (1000 μm × 1000 μm), the shape of the austenite grains are calculated with good accuracy. © 2015 by ASTM International. Source

Bruckhaus R.,AG der Dillinger Huttenwerke | Fandrich R.,Stahlinstitut VDEh
Transactions of the Indian Institute of Metals | Year: 2013

Abstract: About 60 % of the crude steel in Europe is currently produced by the oxygen steelmaking process and 40 % by the electric steelmaking process. The product range is of decisive importance for the layout of the steelworks and the equipment for secondary metallurgical treatment. Regarding steelmaking worldwide, thin slabs are increasingly being produced in addition to conventional formats such as slabs, blooms, billets and beam blanks. In order to ensure long-term economic success, however, companies have continuously to develop sophisticated technologies for steel production. Challenges for the future remain in the production of high-purity steel grades, as well as the development of zero-error strategies with maximum productivity and flexibility. This paper summarizes current trends in the development of steelmaking processes. © 2013 Indian Institute of Metals. Source

Kiefer T.,AG der Dillinger Huttenwerke | Graichen K.,Vienna University of Technology | Kugi A.,Vienna University of Technology
IEEE Transactions on Control Systems Technology | Year: 2010

This brief deals with the tracking control design of a helicopter laboratory experimental setup. In order to be able to realize highly dynamic flight maneuvers, both input and state constraints have to be systematically accounted for within the control design procedure. The mathematical model being considered constitutes a nonlinear mathematical mechanical system with two control inputs and three degrees of freedom. The control concept consists of an inversion-based feedforward controller for trajectory tracking and a feedback controller for the trajectory error dynamics. The design of the feedforward controller for a point-to-point flight maneuver is traced back to the solution of a 2-point boundary value problem in the Byrnes-Isidori normal form of the mathematical model. By utilizing special saturation functions, the given constraints in the inputs and states can be systematically incorporated in the overall design process. In order to capture model uncertainties and external disturbance, an optimal state feedback controller is designed on the basis of the model linearization along the desired trajectories. The proposed control scheme is implemented in a real-time environment, and the feasibility and the excellent performance are demonstrated by means of experimental results. © 2009 IEEE. Source

Steinboeck A.,Vienna University of Technology | Wild D.,AG der Dillinger Huttenwerke | Kugi A.,Vienna University of Technology
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2011

A Lyapunov-based MIMO state feedback controller is developed for slab temperatures in a continuous, fuel-fired reheating furnace. Following an early lumping approach, the computationally simple tracking controller is designed for a nonlinear, switched dynamic model that captures both conductive and radiative heat transfer. The controller modifies reference trajectories of furnace temperatures and is part of a cascade control scheme. Given some nonrestrictive conditions, exponential stability is ensured, even under non-steady state operating conditions. The capabilities of the controller are demonstrated by means of an example problem. © 2011 IFAC. Source

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