77 Works

Novel, highly-filled ceramic–polymer composites synthesized by a spouted bed spray granulation process

Michael F. H. Wolff, Vitalij Salikov, Sergiy Antonyuk, Stefan Heinrich & Gerold A. Schneider
We present a novel processing route to synthesize homogeneous ceramic polymer composites with ultrahigh ( 78 vol.%) packing density by using the spouted bed granulation technology and subsequent warm pressing. In the granulation process, two ceramic particle size fractions (a-Al2O3) and a thermoplastic polymer (polyvinyl butyral) are assembled to granules. In the process, lm-sized particles are coated with a layer of polymer which contains a second, nm-sized ceramic particles fraction. The mass fractions of each...

Three-dimensional discrete element modeling of micromechanical bending tests of ceramic–polymer composite materials

Michael F. H. Wolff, Vitalij Salikov, Sergiy Antonyuk, Stefan Heinrich & Gerold A. Schneider
Ceramic–polymer composite materials are used throughout materials science, but theoretical models which take into account the microstructural design to predict their mechanical properties are still not fully developed. We present an approach to use the discrete element method to model the mechanical behavior under bending load of dense composite materials made from ceramic particles which are bonded together by polymeric layers. Unlike many other modeling approaches, the internal particulate structure of the material, including the...

Low-latency audio over IP on embedded systems

Florian Meier
Übertragung von Audiodaten über Netzwerke wie das Internet ist eine weitverbreitete Technology. Bis jetzt ist die hauptsächliche Anwendung die Übertragung von menschlicher Stimme (Voice over IP). Obwohl moderne Voice over IP Systeme dafür ausgelegt sind Latenz zu reduzieren, ist diese immer noch zu groß um bidirektional Livemusik zu übertragen. Die Entwicklung einer Musikumgebung mit niedriger Latenz würde verteilte Musikaufführungen, sowie "Jamming over IP" erlauben. Diese Arbeit geht einen Schritt in diese Richtung in dem ein...

Strain changes on the cortical shell of vertebral bodies due to spine ageing: a parametric study using a finite element model evaluated by strain measurements

Yongtao Lu, Eike Rosenau, Helge Paetzold, Anke Klein, Klaus Püschel, Michael Morlock & Gerd Huber
The probability of fractures of the cortical shell of vertebral bodies increases as ageing progresses. Ageing involves all the spinal component changes. However, the effect of the spinal component ageing on the fracture risk of the cortical shell remains poorly understood. In this study, the influence of the ageing of the spinal components on cortical shell strain was investigated. A lumbar spinal specimen (L3-L5) was mechanically tested under a quasi-static axial compressive load. Clinical computed...

Modeling creep damage of an aluminum–silicon eutectic alloy

Holm Altenbach, Sergii Kozhar & Konstantin Naumenko
Aluminum–silicon casting alloys are widely used in the automotive industry. The aim of this article is to analyze creep and creep damage of the eutectic AlSi12CuNiMg cast piston alloy and to present a constitutive model that reflect basic features of deformation, aging and damage behavior. Creep tests and force-controlled low cycle fatigue tests are carried out at several levels of temperature. Creep curves exhibit classical three stages. The tertiary creep stage is controlled by damage...

Dynamic positioning of underwater robotic vehicles with thruster dynamics compensation

Wallace Moreira Bessa, Max Suell Dutra & Edwin Kreuzer
The development of accurate control systems for underwater robotic vehicles relies on the adequate compensation of thruster dynamics. Without compensation, the closed-loop positioning system can exhibit limit cycles. This undesired behaviour may compromise the overall system stability. In this work, a fuzzy sliding-mode compensation scheme is proposed for electrically actuated bladed thrusters, which are commonly employed in the dynamic positioning of underwater vehicles. The boundedness and convergence properties of the tracking error are analytically proven....

Analysis of Fast Radix-10 Digit Recurrence Algorithms for Fixed-Point and Floating-Point Dividers on FPGAs

Malte Baesler & Sven-Ole Voigt
Decimal floating point operations are important for applications that cannot tolerate errors from conversions between binaryand decimal formats, for instance, commercial, financial, and insurance applications. In this paper we present five different radix-10 digit recurrence dividers for FPGA architectures. The first one implements a simple restoring shift-and-subtract algorithm, whereas each of the other four implementations performs a nonrestoring digit recurrence algorithm with signed-digit redundant quotient calculation and carry-save representation of the residuals. More precisely, the...

Closed Contour Specular Reflection Segmentation in Laparoscopic Images

Jan Marek Marcinczak & Rolf-Rainer Grigat
Segmentation of specular reflections is an essential step in endoscopic image analysis; it affects all further processing steps including segmentation, classification, and registration tasks. The dichromatic reflectance model, which is often used for specular reflection modeling, is made for dielectric materials and not for human tissue. Hence, most recent segmentation approaches rely on thresholding techniques. In this work, we first demonstrate the limited accuracy that can be achieved by thresholding techniques and propose a hybrid...

Power generation expansion planning including large scale wind integration: A case study of Oman

Arif S. Malik & Cornelius Kuba
Many options can be effectively used to meet the future power needs of a country in ways which would be more economically viable, environmentally sound, and socially just. A least-cost generation expansion planning study is conducted to find the economic feasibility of large scale integration of wind farms in the main interconnected transmission system of Oman. The generation expansion planning software used is WASP which is restricted in its ability to model intermittent nature of...

Contact analysis of a dry friction clutch system

Oday I. Abdullah & Josef Schlattmann
The numerical simulation of the friction clutch system (pressure plate, clutch disc, and flywheel) during the full engagement period (assuming no slipping between contact surfaces) is carried out using finite element method. Two types of load condition considered affect on the clutch elements during the full engagement period are the contact pressure of diaphragm spring and the centrifugal force. The study of the pressure distribution between the contact surfaces and the factors affecting it is...

Modelling of ballistic impact over a ceramic-metal protection system

Leandro Neckel, Dachamir Hotza, Daniel Stainer, Rolf Janßen & Hazim Ali Al-Qureshi
The behavior of ceramic-metal protection against a projectile impact is modeled. The model takes into account the mass and velocity for each stage of the phenomenon. A former model was modified considering more realistic parameters such as geometries and deformation profile. To analyze the model, simulations on different parameters have been run. The impact results of different ballistic projectiles were simulated, and the movement was plotted. In addition, a deterministic simulation on the mechanical properties...

Biomechanical evaluation of 3 stabilization methods on acromioclavicular joint dislocations

Jakob Valentin Nüchtern, Kay Sellenschloh, Nicholas Bishop, Sabrina Yvonne Jauch, Daniel Briem, Michael Hoffmann, Wolfgang Lehmann, Klaus Püschel, Michael Morlock, Johannes M. Rueger & Lars Gerhard Großterlinden
Traumatic acromioclavicular (AC) joint dislocations can be addressed with several surgical stabilization techniques. The aim of this in vitro study was to evaluate biomechanical features of the native joint compared with 3 different stabilization methods: locking hook plate (HP), TightRope (TR), and bone anchor system (AS).

Influence of cooling on curing temperature distribution during cementing of modular cobalt-chromium and monoblock polyethylene acetabular cups

Stephan Rothstock, Mahnaz Saadatmand, Matthias Vollmer, Andreas Paech, Christian Jürgens, Roman Nassutt & Michael Morlock
Total hip replacements for older patients are usually cemented to ensure high postoperative primary stability. Curing temperatures vary with implant material and cement thickness (30°C to 70°C), whereas limits for the initiation of thermal bone damage are reported at 45°C to 55°C. Thus, optimizing surgical treatment and the implant material are possible approaches to lower the temperature. The aim of this study was to investigate the influence of water cooling on the temperature magnitude at...

A three-component model of the control error in manual tracking of continuous random signals

Hans Gerisch, Gerhard Staude, Werner Wolf & Gerhard Bauch
The performance of human operators acting within closed-loop control systems is investigated in a classic tracking task. The dependence of the control error (tracking error) on the parameters display gain, k(display), and input signal frequency bandwidth, f(g), which alter task difficulty and presumably the control delay, is studied with the aim of functionally specifying it via a model.

Transport into nanosheets : diffusion equations put to test

Nils E. R. Zimmermann, Timm J. Zabel & Frerich J. Keil
Ultrathin porous materials, such as zeolite nanosheets, are prominent candidates for performing catalysis, drug supply, and separation processes in a highly efficient manner due to exceptionally short transport paths. Predictive design of such processes requires the application of diffusion equations that were derived for macroscopic, homogeneous surroundings to nanoscale, nano-structured host systems. Therefore, we tested different analytical solutions of Fick’s diffusion equations for their applicability to methane transport into two different zeolite nanosheets (AFI, LTA)...

Transport at gas–zeolite interfaces probed by molecular simulations

Nils E. R. Zimmermann
In dieser Arbeit wird das Phänomen der Oberflächenbarrieren von Kohlenwasserstoffen, die in silikatreiche Zeolithe eindringen, untersucht. Mithilfe molekularer Simulationsmethoden (transiente und Gleichgewichtsmolekulardynamik, Monte Carlo, Reaktivflusssimulationen) und des Abgleichs mit experimentellen Daten aus der Literatur erfolgte eine Kategorisierung, unter welchen Bedingungen (systemisch, thermodynamisch und chemisch) die Barrieren signifikante Auswirkungen auf Diffusionsmessungen haben.

A novel method for a multi-level hierarchical composite with brick-and-mortar structure

Kristina Brandt, Michael F. H. Wolff, Vitalij Salikov, Stefan Heinrich & Gerold A. Schneider
The fascination for hierarchically structured hard tissues such as enamel or nacre arises from their unique structure-properties-relationship. During the last decades this numerously motivated the synthesis of composites, mimicking the brick-and-mortar structure of nacre. However, there is still a lack in synthetic engineering materials displaying a true hierarchical structure. Here, we present a novel multi-step processing route for anisotropic 2-level hierarchical composites by combining different coating techniques on different length scales. It comprises polymer-encapsulated ceramic...

Transforming the Library – Bibliotheksbau für die Zukunft

Inken Feldsien-Sudhaus
The changes taking place in libraries have an impact on various aspects of the day-to-day operations: new competencies of library employees, the expansion of digital services in an increasingly mobile society, changes in the physical and organizational structures, as well as different strategies for necessary adaptations of existing library operations and buildings. This article deals with the latest prognoses being discussed in the USA regarding future areas of activity. Major building projects in other countries...

Auslegung von keramischen Strukturbauteilen unter mehraxialer statischer und zyklischer Beanspruchung

Anna K. Usbeck
Die Werkstoffwissenschaften haben in den letzten Jahrzehnten viele verbesserte und neue Materialien entwickelt. Viele Innovationen sind ohne neue Werkstoffe undenkbar. Zu diesen neuen Materialien gehören die Hochleistungskeramiken, die nicht nur thermische und elektrische, sondern auch mechanische Eigenschaften aufweisen, die für spezielle Anwendungen im Maschinenbau besonders geeignet sind. In der Produktentwicklung stößt der Werkstoff Keramik jedoch oft auf Unverständnis, da sowohl die Herstellprozesse als auch die Verbindungstechniken und Berechnungsverfahren von denen der gängigen Werkstoffe abweichen. In...

Jahresbericht 2012 des Präsidiums der Technischen Universität Hamburg-Harburg

Garabed Antranikian & Technische Universität Hamburg-Harburg
Jahresbericht des Präsidiums der TU Hamburg-Harburg 2012

Eine Methode zur strategischen Planung modularer Produktprogramme

Henry Jonas
Durch den Wechsel von Verkäufer- zu Käufermärkten ist es für die meisten Unternehmen erforderlich, eine hohe Varianz individualisierter Produkte anzubieten. Allerdings führt eine hohe Produktvarianz in der Regel zu einer steigenden Komplexität innerhalb des Unternehmens. Ein zentraler Ansatz muss es deshalb sein, die angebotene Vielfalt marktgerecht auszurichten und die angebotene, extern hohe Varianz unternehmensintern zu reduzieren. Im Rahmen dieser Arbeit wird eine neue Methode zur strategischen Planung modularer Produktprogramme vorgestellt. In der ersten Phase der...

In vitro-Tests für die Charakterisierung von Magnesium als resorbierbares Implantatmaterial

Janine Fischer
Magnesium bietet optimale Eigenschaften als resorbierbares Implantatmaterial. Das beim Abbau der Magnesiummaterialien entstehende Milieu ist allerdings problematisch für die hinsichtlich der Zulassung notwendigen Zytotoxizitätstests nach ISO-Normen. In dieser Arbeit wurde untersucht, zu welchen Problemen es kommen kann, welche Ursachen hierfür relevant sein können und Lösungsmöglichkeiten dargestellt.

The Blue Engineer : IngenieurInnen mit ökologischer und sozialer Verantwortung. Ausgabe 02, Wintersemester 2013/2014

Blue Engineering AG TUHH
The Blue Engineer hat sich der Aufgabe widmet, über inner- und außeruniversitäre Themen mit Bezug zu ganzheitlich verstandener Nachhaltigkeit zu berichten.

Prozessentwicklung zur biotechnologischen Produktion von Acrolein aus Nebenprodukten der Bioethanolherstellung

Sebastian Oehmke
Da fossile Quellen endlich sind, werden Chemikalien aus nachwachsenden Rohstoffen immer interessanter für die Forschung und Industrie. Zu den vielversprechenden Plattformchemikalien gehört das Stoffpaar 3-Hydroxypropionaldehyd/ Acrolein. Jedoch sind bisherige Ansätze für eine wirtschaftliche Produktion von 3-Hydroxypropionaldehyd/ Acrolein im industriellen Maßstab nicht ausreichend. Deshalb wurde in dieser Arbeit geprüft, inwieweit sich Schlempe, ein glycerinhaltiges Nebenprodukt der Bioethanolherstellung, zur 3-Hydroxypropionaldehyd/ Acrolein Produktion nutzen lässt und inwieweit diese Produktion in den Bioethanolprozess im Sinne des Bioraffineriekonzeptes integriert werden...

Infrarot- und Massenspektrometer-System für die dynamische Messung von Motorabgasen

Lars Schomann
Due to growing individual transport in industrial countries and associated increase in pollutant emissions, legislature toughens emission standards regularly. Automakers are therefor challenged to develop ever more efficient low-emission vehicles to take account of the public climate debate and effects of pollutants on humans and nature. Conventional exhaust gas measurement systems are limited when it comes to measuring gases other than O2, CO2, CO, NOX and total-HC or when high measurement frequencies are of the...

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