374 Works

Active vibration control using the centrifugal forces of eccentrically rotating masses

Richard Bäumer
In this PhD thesis, active vibration control using eccentrically rotating masses is investigated. The basic layout of the so-called twin rotor damper (TRD) consists of two eccentric control masses rotating about two parallel axes. In a preferred mode of op-eration, the continuous rotation mode, both control masses rotate in opposite direction with a constant angular velocity. Under further operational constraints, the generated centrifugal forces superimpose to a harmonic control force in a single direction. The...

Transport in nanoporous materials including MOFs : the applicability of Fick’s laws

Tobias Titze, Alexander Lauerer, Lars Heinke, Christian Chmelik, Nils E. R. Zimmermann, Frerich Keil, Douglas M. Ruthven & Jörg Kärger
Die Diffusion in nanoporösen Wirt-Gast-Systemen wird oft als viel zu kompliziert angesehen, als dass sie mit so “einfachen” Beziehungen wie dem ersten und zweiten Fickschen Gesetz vereinbar sein könnte. Wir zeigen nun, dass die mikroskopischen Diffusionsmesstechniken, vor allem die NMR-Spektroskopie mit gepulsten Feldgradienten (PFG) und die Mikrobildgebung mittels Interferenzmikroskopie (IFM) und IR-Mikroskopie (IRM), den direkten experimentellen Nachweis für die Anwendbarkeit der Fickschen Gesetze auf solche Systeme liefern. Dies gilt oft auch dann noch, wenn die...

Hybrid system calibration for multidimensional magnetic particle imaging

Anselm von Gladiß, Matthias Gräser, Patryk Szwargulski, Tobias Knopp & Thorsten M. Buzug
Magnetic particle imaging visualizes the spatial distribution of superparamagnetic nanoparticles. Because of its key features of excellent sensitivity, high temporal and spatial resolution and biocompatibility of the tracer material it can be used in multiple medical imaging applications. The common reconstruction technique for Lissajous-type trajectories uses a system matrix that has to be previously acquired in a time-consuming calibration scan, leading to long downtimes of the scanning device. In this work, the system matrix is...

Numerical investigation of compaction of deformable particles with bonded-particle model

Maksym Dosta, Clara Costa & Hazim Ali Al-Qureshi
In this contribution, a novel approach developed for the microscale modelling of particles which undergo large deformations is presented. The proposed method is based on the bonded-particle model (BPM) and multi-stage strategy to adjust material and model parameters. By the BPM, modelled objects are represented as agglomerates which consist of smaller ideally spherical particles and are connected with cylindrical solid bonds. Each bond is considered as a separate object and in each time step the...

Lösender Angriff auf zementgebundene Baustoffe – Veränderungen der Porenstruktur und Folgen für Transport- und Korrosionsprozesse

Holle Kerstin Goedeke
Es wurden Korrosionsversuche an Zementmörteln mit stationären und instationären Randbedingungen durchgeführt. In weiteren Versuchen wurden die Veränderung der Porosität und Porenstruktur sowie die damit verbundenen Auswirkungen auf die Stofftransportprozesse betrachtet. Weiterhin wurden Simulationsberechnungen durchgeführt. Mit dem Ziel einer Verbesserung der Berechnung von Transportprozessen erfolgte eine Anwendung verschiedener Porenstrukturmodelle auf experimentell ermittelte Daten. Den Abschluss bildet die Vorstellung eines neuen Modellansatzes zur Beschreibung der Porenstrukturänderung infolge von Korrosionsprozessen.

Dominant damping effects in friction brake noise, vibration and harshness : the relevance of joints

Merten Tiedemann, Sebastian Kruse & Norbert Hoffmann
The experimental analysis of a single component of a brake system and an assembly consisting of three components is used to clarify the relevance of joints in terms of damping and non-linearity in state-of-the-art brake systems. For this purpose a series of experimental modal analyses are conducted. A comparison of the results obtained from the single component and from the assembly strongly indicate that the joints which necessarily exist in an assembled structure have a...

Advances in porous biomaterials for dental and orthopaedic applications

Meenakshi Mour, Debarun Das, Thomas Winkler, Elisa Hoenig, Gabriela Mielke, Michael Morlock & Arndt Schilling
The connective hard tissues bone and teeth are highly porous on a micrometer scale, but show high values of compression strength at a relatively low weight. The fabrication of porous materials has been actively researched and different processes have been developed that vary in preparation complexity and also in the type of porous material that they produce. Methodologies are available for determination of pore properties. The purpose of the paper is to give an overview...

Strain-gauge-based measurements of ice loads on ships

Till Zorn
Design loads are a central element of ship construction, because they influence plate and frame thickness. For the construction of ships that are destined to navigate in cold areas, it is extremely important to take into account the loads of ice impacts and their location on the hull. But ice is a particularly inconsistent material. To measure ice-induced loads, a lot of measurement has been undertaken, many of them used strain gauges. However, long-term strain...

Supplier Integration in Industry 4.0 – Requirements and Strategies

Julian Marius Müller, Johannes Veile & Kai-Ingo Voigt
Cross-company networking is essential to successfully implement Industry 4.0. In this context, numerous new demands on suppliers arise leading to integration challenges that require specific integration strategies. While these topics are important in business practice, an aggregated holistic overview is still missing. Therefore, this article examines new demands on suppliers, challenges in the implementation process, and integration strategies for supplier integration in the context of Industry 4.0. Expert interviews with 15 different industrial companies from...

Frequency or amplitude? : Rheo-electrical characterization of carbon nanoparticle filled epoxy systems

Hauke Meeuw, Valea Kim Wisniewski & Bodo Fiedler
Dispersion of carbon nanoparticles in epoxy resin is the key factor to adjust the resulting electrical and mechanical properties of the nanocomposite. A profound understanding of the driving forces of standard methods like ultrasonic and mechanical dispersion is necessary. To derive the impact of applied frequency and strain on the resulting dispersion of multi-walled carbon nanotube (MWCNT)-filled epoxy resin, this work addresses the strain and frequency dependency of oscillatory shear flow-induced network changes. Strain- and...

Exploring the acceptance of ubiquitous computing-based Information services in brick and mortar retail environments : an integration of UTAUT2 and media system dependency theory

Sara Kheiravar
Stationäre Einzelhändler setzen zunehmend digitale Technologie ein, um ihren Kunden bei Informationssuche und -bewertung zu unterstützen. Die eingesetzten Technologien werden als In-Store Ubiquitous Computing basierende Informationstechnologien bezeichnet. Erkenntnisse zu Akzeptanz dieser Technologien durch Kunden stehen noch aus. In dieser Dissertation wird ein Kontext spezifisches Modell zur Technologieakzeptanz basierend auf UTAUT2 entwickelt und um Nutzer, Service und Technologie relevante Aspekte erweitert. Das abgeleitete Modell wird mit Hilfe eines Strukturgleichungsmodells (PLS) auf Basis einer auf Szenarien basierenden...

Design of cylindrical shells using the single perturbation load approach : potentials and application limits

Benedikt Kriegesmann, Eelco Luc Jansen & Raimund Rolfes
The Single Perturbation Load Approach (SPLA) is a promising deterministic procedure on the basis of mechanical considerations to determine reasonable design loads for cylindrical shells in axial compression. In this paper, two main issues are identified that should be understood better in order to appreciate the potential and the limits of application of the SPLA. Firstly, the question whether a single perturbation load in general represents a “worst case” imperfection is addressed. Secondly, the influence...

An energy approach for the active vibration control of an oscillator with two translational degrees of freedom using two auxiliary rotating masses

Richard Bäumer, Richard Terrill & Uwe Starossek
An active mass damper implementing two auxiliary masses rotating about a single axis is presented. This device is used for the vibration control of an oscillator performing translational motion in a plane (two translational degrees of freedom). In a preferred mode of operation, both auxiliary masses rotate with the same constant angular velocity in opposite directions. The resultant of the produced harmonic centrifugal forces is used for the vibration control. The direction of this control...

Clinical and wear analyses of 9 large metal-on-metal total hip prostheses

Maarten C. Koper, Nina M. C. Mathijssen, Florian Witt, Michael Morlock & Stephan B. W. Vehmeijer
Metal-on-Metal (MoM) total hip arthroplasties (THA) are associated with pseudotumor formation and high revision rates. This prospective study analysed the clinical and wear analyses of 9 large Metal-on-Metal (MoM) total hip arthroplasties (THA) to understand the underlying mechanisms of failure. The MoM bearings were revised for multiple reasons; the main reason was pseudotumor formation.

Combined FEM-SPH simulations for ice in compression

Niklas Düchting
Within this chapter the outcome of the numerical investigation on a combined FEM-SPH simulation is summed up. The practical approach of this project allows only a rather sim-ple assessment and there are aspects that need to be investigated further. An outlook in-dicates possible aspects for future research. Regarding the correlation of the contact forces the results of the final simulations pre-sented in section 3.3.1 are satisfying. The ability to model the transformation of the ma-terial...

Forschungsdatenmanagement - Umfrage TUHH

Andreas Pohnke, Inken Feldsien-Sudhaus & Detlev Bieler
Poster mit Auszügen der Ergebnisse der Umfrage zum Forschungsdatemnamagement an der TUHH, Zeitraum: 11. Juli bis 15. August 2016, Zielgruppe: MitarbeiterInnen des wissenschaftlichen Personals der TUHH. Vollständige Auswertung hier abrufbar: https://doi.org/10.15480/882.1326

Identification of fully coupled anisotropic plasticity and damage constitutive equations using a hybrid experimental–numerical methodology with various triaxialities

Z. M. Yue, Celal Soyarslan, H. Badreddine, K. Saanouni & A. E. Tekkaya
A hybrid experimental–numerical methodology is presented for the parameter identification of a mixed nonlinear hardening anisotropic plasticity model fully coupled with isotropic ductile damage accounting for microcracks closure effects. In this study, three test materials are chosen: DP1000, CP1200, and AL7020. The experiments involve the tensile tests with smooth and notched specimens and two types of shear tests. The tensile tests with smooth specimens are conducted in different directions with respect to the rolling direction....

Cross-disciplinary communication among Ph.D. candidates : how to make it work

Ulrike Herzog, Alette Winter & Christian H. Kautz
Cross-disciplinary research settings are highly challenging for young scientists. In our research centre, Ph.D. candidates with various disciplinary backgrounds are expected to cooperate. To support cooperation, we designed a Ph.D. programme that fosters cross-disciplinary communication. The programme uses an innovative teaching format that aims to broaden the participants’ understanding of technical basics and to improve their academic teaching skills. Being faced with dissatisfaction among the Ph.D. candidates at first, we introduced a targeted feedback process...

Hierarchical aerographite 3D flexible networks hybridized by InP micro/nanostructures for strain sensor applications

Irina Plesco, Julian Strobel, Fabian Schütt, Cameliu Constantin Himcinschi, Nabiha Ben Sedrine, Teresa Monteiro, Maria Rosário Correia, Leonid Gorceac, Boris Cinic, Veaceslav Ursaki, Janik Marx, Bodo Fiedler, Yogendra Kumar Mishra, Lorenz Kienle, Rainer Adelung & Ion Tiginyanu
In the present work, we report on development of three-dimensional flexible architectures consisting of an extremely porous three-dimensional Aerographite (AG) backbone decorated by InP micro/nanocrystallites grown by a single step hydride vapor phase epitaxy process. The systematic investigation of the hybrid materials by scanning electron microscopy demonstrates a rather uniform spatial distribution of InP crystallites without agglomeration on the surface of Aerographite microtubular structures. X-ray diffraction, transmission electron microscopy and Raman scattering analysis demonstrate that...

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 nanoporous gold-polypyrrole hybrid nanomaterial for actuation

Ke Wang, Charlotte Stenner & Jörg Weißmüller
We discuss actuation with a hybrid nanomaterial that is made by electro-polymerizing pyrrole on the internal surfaces of dealloying-derived nanoporous gold and then letting aqueous electrolyte be imbibed in the remaining pore space. In this way, active polypyrrole films are contacted by two separate but individually contiguous conduction paths, providing efficient transport of ions in the electrolyte channels and of electrons in the metal skeleton. The metal skeleton also serves to enhance the mechanical behavior...

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...

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...

Settlements in unsaturated granular soils induced by changes in saturation and suction

Marius Milatz, Tom Törzs & Jürgen Grabe
In this contribution the hydro-mechanically coupled behaviour of a sand is experimentally investigated with the focus on settlements induced by changes in degree of saturation and suction. This phenomenon, referred to as collapse behaviour, is attributed to rearrangements of the grain skeleton due to changing capillary effects on wetting of the soil. For the experimental investigation of the collapse behaviour of a medium coarse sand cyclic dryingwetting tests are performed under oedometric conditions. In the...

Deformation of press-fitted metallic resurfacing cups. Part 2: Finite element simulation

A. Yew, Zhongmin Jin, A. Donn, Michael Morlock & Graham H. Isaac
The deformation of metallic acetabular cups employed for metal-on-metal hip resurfacing procedures was considered theoretically using the finite element method in the present study, following on the experimental investigation reported in Part 1. Three representative cups, characterized by the cup wall thickness as thin, intermediate, and thick, were considered. For the intermediate cup, the effects of both the size and the diametral interference on the cup deformation were investigated. Both two-dimensional axisymmetric and three-dimensional finite...

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  • 2018

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