bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis Techniques for Eddy Current Imaging of Carbon Fiber Materials*
Authors: Schulze Martin H. , Meyendorf Norbert , Heuer Henning
Published: December 2013

Carbon fiber materials become more and more important for many applications. Unlike metal the technological parameters and certified quality control mechanisms for Raw Carbon Fiber Materials (RCF) have not yet been developed. There is no efficient and reliable testing system for in-line inspections and consecutive manual inspections of RCF and post laminated Carbon Fiber Reinforced Plastics (CFRP). Based upon the multi-frequency eddy current system developed at Fraunhofer IZFP, structural and hidden defects such as missing carbon fiber bundles, lanes, suspensions, fringes, missing sewing threads, and angle errors can be detected. Using an optimized sensor array and intelligent image pre-processing algorithms, the complex impedance signal can be allocated to different carbon fiber layers. This technique enables the detection of defects in depths of up to 5 layers, including the option of free scale measuring resolution and testing frequency. Appropriate parameter lists for optimal error classifications are available. The dimensions of the smallest detectable flaws are in the range of a few millimeters. Algorithms and basic Eddy Current C-Scan processing techniques for carbon fiber material testing are described in this paper.
Entwicklung von aufwandsoptimierten Prüfmethoden zur Charakterisierung und Harshnessbeurteilung von Luftfedern
Authors: Puff Matthias , Pelz Peter , Wirnitzer Andreas
Published: December 2013

Kurzfassung

Luftfederung ist eine durch deutsche Fahrzeughersteller und Zulieferer vorangetriebene, vergleichsweise junge Technologie. Die zuverlässige Fertigung dünner Elastomer-Rollbälge mit einer Wandstärke kleiner als 2 mm hat sich erst in den vergangenen zehn Jahren seit der Serieneinführung der Mercedes-Benz-Baureihe W220 (S-Klasse) im Jahr 1998 entwickelt. Bedingt durch die kurze Historie der modernen PKW-Luftfederung wurden Prüfmethoden zur Charakterisierung und Bewertung des zu erwartenden Abrollkomforts in einem frühen Entwicklungsstadium des Fahrzeuges noch nicht in ausreichendem Maße entwickelt und kommuniziert. Dies veranlasste die Technische Universität Darmstadt, Institut Fluidsystemtechnik, eine aufwandsoptimierte Prüfspezifikation zu entwickeln. Neben der Charakterisierung stand dabei der Entwurf von Prüfmethoden zur Beurteilung des Harshnessverhaltens von Luftfedern im Vordergrund. Durch die Zusammenarbeit mit dem VDA-FAT-Arbeitskreis für Fahrdynamik wurde neben der Aufwandsoptimierung eine Vereinheitlichung der Prüfspezifikationen der Fahrzeughersteller und Zulieferer erreicht. Insbesondere wird eine Sprunganregung eingeführt und diskutiert.
Dreidimensionale Untersuchung der Wasserverteilung in einer Miniatur-PEM-Brennstoffzelle
Authors: Krüger Philipp , Markötter Henning , Klages Merle , Haußmann Jan , Arlt Tobias , Riesemeier Heinrich , Hartnig Christoph , Banhart John , Manke Ingo , Scholta Joachim
Published: December 2013

Kurzfassung

Synchrotronstrahlung wird für tomografische Aufnahmen eingesetzt, um die Wasserverteilung in der Gasdiffusionslage (GDL) von Niedertemperatur-Polymerelektrolytmembran-Brennstoffzellen (PEMFC) zu untersuchen. Die hohe räumliche Auflösung von ca. 10μm bei gleichzeitig großem Sichtfeld ermöglicht die Analyse der Wasseragglomerationen in der porösen Struktur der GDL sowie in den Gasverteilerkanälen. Durch die dreidimensionale Aufnahme der Zelle ist ein umfassender Einblick in den Wassergehalt möglich. Dazu wird die Brennstoffzelle in einem stationären Zustand betrieben und direkt nach dem Betrieb tomografiert. Die Tomogramme können bei verschiedenen Betriebszuständen aufgenommen und analysiert werden. Einblicke in das Zellgefüge sind aus unterschiedlichen Blickwinkeln möglich. Schnittansichten ermöglichen darüber hinaus detaillierte Untersuchungen, insbesondere des Wasserhaushalts in der GDL. Neben der Visualisierung der Wasserverteilung ist somit auch eine Charakterisierung der verwendeten Materialien hinsichtlich ihrer Transporteigenschaften möglich.
Hochauflösende Synchrotron- Radiografie
Authors: Markötter Henning , Manke Ingo , Hartnig Christoph , Krüger Philipp , Wippermann Klaus , Arlt Tobias , Choinka Gerard , Riesemeier Heinrich , Banhart John
Published: December 2013

Kurzfassung

In-situ-Synchrotron-Radiografie wird eingesetzt, um die Verteilung und den Transport von CO2und Wasser in Direktmethanol- und Polymerelektrolytmembran-Brennstoffzellen (DMFCs und PEMFCs) sichtbar zu machen, um so die Eigenschaften der eingesetzten Materialien gezielt optimieren zu können. Bei der Synchrotronradiografie werden vor allem dynamische Prozesse sowohl zeitlich als auch räumlich sehr gut aufgelöst und Vorgänge in einer Brennstoffzelle zerstörungsfrei und nichtinvasiv während des Betriebes sichtbar gemacht. In diesem Artikel wird eine Übersicht über die vielfältigen Anwendungsmöglichkeiten der Synchrotron-Radiografie in der Brennstoffzellenforschung gezeigt. Flüssigkeits- und Gasverteilungen werden sowohl flächig (through-plane) als auch im Querschnitt durch die Zelle (in-plane von Anode zu Kathode) analysiert. Anhand ausgewählter Beispiele werden der Zusammenhang zwischen Mikrostruktur der eingesetzten Materialien und dem Medientransport sowie der Einfluss von Betriebsparametern auf die Medienverteilung dargelegt.
Hochortsauflösendes, großflächiges Neutronen-Detektorsystem für die Brennstoffzellenforschung
Authors: Tötzke Christian , Hilger André , Arlt Tobias , Markötter Henning , Choinka Gerard , Kardjilov Nikolay , Schröder Alexander , Wippermann Klaus , Scholta Joachim , Hartnig Christoph , Banhart John , Manke Ingo
Published: December 2013

Kurzfassung

Die speziellen Eigenschaften von Neutronen, insbesondere die hohe Sensitivität für Wasser sowie die Fähigkeit, viele metallische Komponenten zu durchdringen, macht die Neutronenradiografie zum attraktiven Werkzeug für die Brennstoffzellenforschung. Die detaillierte Untersuchung des Wasserhaushalts erfordert eine hohe Ortsauflösung des Detektors sowie ein flexibles und großes Abbildungsfeld. Bislang schränkte die geringe räumliche Ortsauflösung konventioneller Detektorsysteme die Detailtiefe bei der Wiedergabe von Wasserverteilungen in Zellen stark ein. Spezielle hochauflösende Detektorsysteme hingegen ermöglichen nur die Abbildung kleinster Teilbereiche der Zelle. Am Helmholtz-Zentrum Berlin wurde ein Detektorsystem entwickelt, das beide Grundforderungen erfüllt: Ein neuartiger Gadox-Szintillator ermöglicht eine deutlich verbesserte Ortsauflösung von max. 25 μm. Das verwendete Kamerasystem mit einem 4096×4097-Pixel-CCD-Sensor ermöglicht ein großes und flexibles Abbildungsfeld, z.B. 61,44×61,44 mm2beim 1:1-Abbildungsmaßstab. Mit diesem System lassen sich Brennstoffzellen großflächig und mit hoher Auflösung untersuchen.
Small Mass Impact Testing of Sandwich Structures
Authors: Dietrich Stefan , Kuppinger Jan , Elsner Peter , Weidenmann Kay
Published: December 2013

Small mass impacts pose a threat to modern lightweight materials even at low velocities. In this study we describe a test method with a suitable setup to access the materials impact response to masses below 500 g and velocities up to 20 m/s. The setup uses a highspeed camera and adapted semi-automatic image processing algorithms to extract the time-force history of the indenter. The results show good agreement to analytical impact models for hollow core sandwich structures.
Development of an Armor Steel for Ballistic Protection
Authors: Yilmaz Alpay
Published: December 2013

In this study, a newly developed Boron alloyed armor steel is presented and its mechanical properties as well as its ballistic applications are given. Further, a description of ballistic terms is included to understand the development of armor steel for the use in civil and defence applications. The main subject of the study is the microstructural design of these steels. For this purpose a Boron alloyed experimental steel has been produced by quenching and tempering. The microstructures obtained after such heat treatments have been examined by light microscopy (LM) and scanning electron micoscopy (SEM). The application of precipitation hardening is highlighted by the effect of alloying elements and the resulting matrix hardening potential. As a result, a suggestion is given for the alloy design of the new armor steel with Boron additions. The effect of microstructure and mechanical properties (strength, hardness, toughness, etc.) of this experimental armor steel have been evaluated by methods similar to homogeneous rolled armor steels (MIL-A-12560) targeted at a good ballistic performance. Also the effect of heat treatment on the mechanical properties of armor steel is shown. The impact toughness values at different test temperatures are comparatively given in addition to the relationship between ballistic performance and hardness for armor steels. Attempts have been undertaken to explain the cause of deformation and failure occurred in the steel plates due to projectile penetration with light and scanning electron microscopical studies.
In-Situ Crack Detection Using Thermo Elastic Stimulated Lock-In Thermography
Authors: Brucksch Rolf , Bär Jürgen , Gudladt Hans-Joachim
Published: December 2013

In this work the lock-in-thermography was tested for crack detection capabilities. Instead of an external heat source the thermo elastic effect induced by the mechanical loading is used for cyclic thermal stimulation. This procedure was applicable for crack detection in an aluminium centre cracked tension specimen (CCT) during a running fatigue test. As lock-in input signal the force as well the signal of a strain gauge, placed in the surrounding of an estimated crack initiation site, can be used, respectively. This strain gauge can also be attached perpendicular to the loading direction.
Enhanced Grain Orientation in Pb(Zr,Ti)O3 Powder-Modified SrBi2Ta2O9 Ferroelectric Ceramics
Authors: Liu Jingsong , Li Huiqin
Published: December 2013

Pb(Zr,Ti)O3 (PZT) powder modified SrBi2Ta2O9 (SBT) ceramics, hereafter called SBT-PZT, were prepared by the solid phase synthesis method. With the aid of atomic force microscopy and x-ray diffractometry, the SBT-PZT ceramics were found to exhibit an enhanced c-axis orientation compared with SBT ceramics. Ferroelectric and dielectric properties of SBT-PZT ceramics were revealed to be anisotropic by relevant measurements. Because of differences in heteropolar valence and ionic radius between SBT and PZT, the PZT may be introduced into SBT as a heterogeneous system and embedded in the SBT grain boundaries. The large differences in crystal structures between SBT and PZT were proposed to be responsible for the SBT-PZT grain orientation mechanism. Obviously, the grain orientation resulted in electrical anisotropies of SBT-PZT ceramic. The internal stress, which was induced by heterogeneous system doping, was considered to affect the polarization reversal of SBT-PZT ceramics.
Grundlagen eines Walzenverschleiß-Prüfstandes für Warmwalzen
Authors: Goryany Vyacheslav
Published: December 2013

Kurzfassung

Es wurden die Grundlagen eines Modells zur Verschleißprüfung von Walzen entwickelt. Diese berücksichtigen den Einfluss von Einsatzparametern in einem Warmwalzgerüst und ermöglichen eine gute Ähnlichkeit der Kontakt- sowie Reibbedingungen zwischen einer Probe („Walze“) und einem Reibkörper („Walzgut“) in einem Prüfstand.
Leichtbaupotenzial zyklisch belasteter Laserstrahl-Hybridschweißverbindungen aus S1100QL
Authors: Winderlich Bernd , Jahn Axel , Brenner Berndt
Published: December 2013

Kurzfassung

Laserstrahl-Hybridschweißverbindungen aus S1100QL sind sehr gut für den industriellen Einsatz in zyklisch hochbelasteten Leichtbaukonstruktionen geeignet. Vorteile gegenüber dem MAG-Schweißen ergeben sich u. a. aus kürzeren Prozesszeiten, geringerem Wärmeeintrag und der Reduzierung des Verzuges. Blecheben überschliffene Hybrid-Stumpfnähte erreichen die Schwingfestigkeit des reinigungsgestrahlten Grundwerkstoffs. Poren im Schweißgut sind der begrenzende Faktor. Der Einsatz der Schweißverbindungen ist sinnvoll bei hohen Mittelspannungen und geringen Lastspielzahlen. Hier ergibt sich ein Vorteil des Schleifens gegenüber dem UIT-Verfahren zur Erzeugung von Druckeigenspannungen am Nahtübergang. Auslegungs- und Fertigungsaspekte sowie Prüferfordernisse werden erörtert.
Topology Optimization for a Micro/Nano Compliant Grip and Move with Parallel Movement Tips Using Multi-Objective Compliance
Authors: Helal Mahmoud , Sun Lining , Chen Liguo , Harbin Weibin Rong
Published: December 2013

The past few years have witnessed an increasing maturity of the micro- and nano-electro-mechanical systems (Mems/Nems) industry and a rapid introduction of new products addressing applications ranging from biochemical analysis to fiber-optic telecommunications. The assembly of micro-devices involves handling of parts that are extremely very small. A microgripper compliant mechanism is one of the key elements in micro-robotics and micro-assembly technologies for handling and manipulating micro- objects without damage. This paper presents the design of compliant grip and move manipulators with parallel movement tips. The integration of both, gripping and moving manipulators, with parallel movement tips is accomplished by the use of compliant mechanisms, which generate paths that are symmetric. These mechanisms can grip an object and convey it from one point to another with parallel movement. The structural topology optimization approach is applied in order to find the optimal material distribution in the proposed domain for compliant mechanisms. The objective of the optimization problem is to maximize the structural stiffness within the limit of prescribed design volume. A two-dimensional finite element analysis model using Ansys is constructed for the proposed design domain. Three optimal configurations of two-dimensional compliant mechanism, which can realize a micro grip and move with parallel movement tips for a wide range of micro- and nano-objects, are demonstrated.
Modelling and Experimental Study of Mechanical Behaviour of Walls Produced by Different Knitting
Authors: Kamanli Mehmet , Donduren Mahmut Sami , Cogurcu Mustafa Tolga , Altin Mustafa
Published: December 2013

This study aims to investigate the shear behavior and resistance of brick walls produced by various knitting types. For this purpose, 15 samples were produced using Holland knitting, block knitting, cross knitting, lock knitting, and plain knitting. The samples were forced in experiments to collapse and in the non-linear region, the changes in the samples related with shear forces and shear rigidity of the wall sections were determined. In the performed experimental study, the standard sliding resistance test technique for the masonry wall samples has been determined as recommended in ASTM Standard 1391-81. The numerical modeling was carried out by the finite elements method with the program package Ansys, taking into account the local mechanical parameters of bricks and mortar. The behavior of the experimental samples and the cracks occurred during the experiments were analyzed and shear stress graphs and load-displacement graphs were derived. The modeling with the Ansys program was compared with the experimental results and the most appropriate wall knitting type could be proposed.
Festigkeitskonzepte für schwingbelastete geschweißte Bauteile*
Authors: Störzel Klaus , Baumgartner Jörg , Bruder Thomas , Hanselka Holger
Published: December 2013

Kurzfassung

Für die schwingfeste Bemessung von Schweißverbindungen an Stahl- oder Aluminiumstrukturen behauptet sich in jüngster Zeit das Kerbspannungskonzept zunehmend gegenüber den traditionell angewendeten Nenn- und Strukturspannungskonzepten. Insbesondere bei der Anwendung des Kerbspannungskonzeptes auf Schweißverbindungen von dünnen Blechen mit dem Referenzradius rref = 0,05 mm zeigen sich vielfältige Einflussfaktoren auf die Bemessungswöhlerlinie, welche durch Größeneinflüsse erklärt werden können.
Praxisnahes Absicherungskonzept für neue Material- und Fügetechnologien in der Betriebsfestigkeitsberechnung*
Authors: Ruf Andreas , Barenbrock Dirk , Behr Robert
Published: December 2013

Kurzfassung

Grundlage für eine verlässliche digitale Betriebsfestigkeitsauslegung sind validierte Berechnungsmethoden mit bekannten Sicherheitsfaktoren. Letztere lassen sich jedoch höchstens eingeschränkt aus einfachen Probenversuchen bestimmen, da hier die praxisnahe Belastung, Fertigung und Prüfung nur teilweise berücksichtigt werden. Gleichzeitig bedeutet der zunehmende Entfall von Erprobungsträgern im Fahrzeugbau auch einen Verlust an Validierungsmöglichkeiten. Um die daraus entstehende Lücke im Absicherungsprozess zu schließen, wurde bei der Daimler AG ein flexibel, aber praxisnah einsetzbares Prinzipbauteil entwickelt. Damit ergibt sich ein durchgängiges Absicherungskonzept für neue Berechnungsmethoden von der Kalibrierung auf Probenbasis bis zur Bestimmung der Sicherheitsfaktoren.
A Verified and Efficient Approach Towards Fatigue Validation of Safety Parts*
Authors: Weihe Stefan , Weigel Nicolas , Dreßler Klaus , Speckert Michael , Feth Sascha
Published: December 2013

In the automotive industry, safety parts must be designed according to the state of the art of science and technology such that they do not fail as long as the vehicle is used according to its purpose and misuse of the vehicle does not exceed a reasonably expectable degree. Due to scatter in customer loads and component properties, fatigue validation needs to be based on statistical methods. Mathematically sound methods are devised in order to make the validation process as efficient as possible. They allow considering all test results, including censored test data (e.g. tests suspended due to premature failure of components which are not under consideration). Furthermore, these methods permit adapting the success run criterion successively to the testing process.
Shearing Mechanical Properties of Structural Planes of a Regular Tooth Rock
Authors: Zhang Qingzhao , Shen Mingrong , Clark Carl
Published: December 2013

Mechanical properties of discontinuities are different from those of a whole rock. In particular, shear strength of a discontinuity is closely related to its morphological characteristics. Study on mechanical behavior and its failure mechanism of jointed rocks under shear stresses is of great theoretical significance. This paper presents a fundamental research on mechanical properties of the regular jugged discontinuity under various normal stresses. The strength and roughness of discontinuity under shear stress are investigated by analysis of the shear test data. An empirical formula between slope ratio and roughness coefficient of discontinuity are proposed to calculate shear stiffness, and an empirical formula is finally established to evaluate shear strength of discontinuity.
Characterization of Microstructural Changes in a Duplex Stainless Steel Using Spectral Analysis and Conventional Ultrasonic Techniques
Authors: Rodríguez Edda , Stella Jorge , Ruiz Augusto , Fargas Gemma , Mateo Antonio
Published: December 2013

In the present study, spectral analysis of ultrasonic signals and measurements of the velocity of longitudinal ultrasonic waves have been carried out on a duplex stainless steel type 2205. Specimens were annealed at 875°C in time periods between 1800 and 86400 s in order to promote microstructural changes associated to σ-phase formation. Transducers with frequencies of 5, 10 and 17 MHz were used to obtain power spectra. The spectra corresponding to long time treatments showed a high attenuation of the ultrasonic waves, which is attributed to the precipitation of σ-phase and secondary austenite. Furthermore, overall results suggest that spectra obtained at frequencies of 10 and 17 MHz allow, with acceptable accuracy, distinguishing the microstructural changes that take place in this duplex steel for prolonged aging times.
Effects of Thermal Oxidation and Subsequent Pickling on Pitting Geometry of Austentitic Stainless Steels in Chloride Solutions
Authors: Alar Vesna , Esih Ivan , Budic Ivan , Brod Slavonski
Published: December 2013

Harmful effects of thermal oxides formed on austenitic stainless steels (SS) like AISI 304 and 316L by heating in air or other oxidizing gases on their pitting liability in chloride solutions have been studied by pursuing geometric characteristics of corrosion process (pits density, their depths, and mouth areas, ie. penetrating and superficial detrimental consequences etc.). The possibility of preventing the decay of thermally oxidized austenitic SS by chemical removal (pickling) of oxides before exposure to chloride solutions was successfully applied on simple specimens but serious difficulties arose on welded parts and on parts exposed to other temperature gradients during manufacture or in exploitation.
Plasmagestützte Ionisations-spektroskopie (PGIS) zur Materialanalyse
Authors: Brückner Stephan , Rösner Simon , Gerhard Christoph , Wieneke Stephan , Viöl Wolfgang
Published: December 2013

Kurzfassung

Im Rahmen des Niedersächsischen Innovationsverbunds Plasmatechnik (NIP) werden neue Anwendungen der Plasmatechnologie in den Bereichen Fertigungstechnik und Materialanalyse bis hin zur Medizintechnik erschlossen sowie ihr ökonomischer und ökologischer Nutzen evaluiert. Im Bereich der Materialanalyse zählt dazu die Entwicklung eines spektroskopischen Verfahrens unter Nutzung eines ökoeffizienten Atmosphärendruckplasmas zur Emissionsanregung. Zum Einsatz kommt hierbei eine im Rahmen des Projekts entwickelte neuartige Plasmaquelle, die für die Analyse gasförmiger, flüssiger und fester Proben in unterschiedlichen Modi betrieben werden kann. Der Energieeintrag in das Probenmaterial durch diese Plasmaquelle beträgt hierbei wenige Mikrojoule. An verschiedenen Probenmaterialien wurde gezeigt, dass sich dieses Verfahren zur Erzeugung und Detektion elementspezifischer Spektrallinien eignet.
Schadensvermeidung und Lebensdauerverlängerung in technischen Komponenten*
Authors: Richard Hans Albert , Kullmer Gunter , Schramm Britta , Riemer Andre
Published: December 2013

Kurzfassung

Maßnahmen zur Schadensuntersuchung, Schadensvermeidung und Lebensdauerverlängerung von technischen Bauteilen und Strukturen stehen im Mittelpunkt dieses Beitrags. Behandelt werden Schäden durch mechanische Beanspruchungen, wobei zwischen Festigkeitsversagen und bruchmechanischem Versagen unterschieden wird. Lebensdauerverlängernde Maßnahmen werden anhand von Praxisbeispielen aufgezeigt.
Keramische Werkstoffe für Walzen und andere Komponenten für das Warmwalzen
Authors: Goryany Vyacheslav , Düsseldorf Dirk Lowke , Wagner Rolf
Published: December 2013

Kurzfassung

Das Verhalten von Stauchbahnen aus verschleißfesten und hochtemperaturbeständigen keramischen Werkstoffen wie Siliciumnitrid (Si3N4) verschiedener Qualitäten sowie aluminiumoxydverstärktem Zirkonoxyd (ATZ) bei den Zylinderstauchversuchen mit Stahl, Kupfer-Zinn- (CuSn), Kupfer-Silber-Legierungen (CuAg) wurde untersucht. Die dargestellten Ergebnisse zeigen die Oberflächensituation der Stauchbahnen (Porigkeit, Rissbildung, Anhaftungen, Verschleiß) vor und nach den Kalt- und Warmumformversuchen. Der Oberflächenzustand der Proben wurde mittels Licht- sowie Rasterelektronenmikroskopie analysiert.
Schadensursachen und Schadensmanagement an Straßenbahnen*
Authors: Fleischer Thomas , Rennert Roland , Uebel Lutz , Bobsien Steffen
Published: December 2013

Kurzfassung

In diesem Artikel werden die Themen Schadensursache und Schäden, Strukturmodifikationen, Sicherheitskonzept, Festigkeitswerte und Ergebnisse an Straßenbahnen behandelt.
ANN-Based Wear Performance Prediction for Plasma Nitrided Ti6Al4V Alloy
Authors: Kahraman Fatih , Karadeniz Süleyman , Durmuş Hülya
Published: December 2013

Surface modification of a Ti6Al4V titanium alloy was made by the plasma nitriding process. Plasma nitriding was performed in a constant gas mixture of 20% H2–80% N2 at temperatures between 700 and 1000° C and process times between 2 and 15 h. Samples nitrided at different treatment times and temperatures were subjected to the dry sliding wear test using the pin-on-disc set up under 80N normal load with rotational speed of counter face disc of 0.8 m/s at room conditions. An artificial neural network (ANN) model of was developed for prediction of wear performance of the plasma nitrided Ti6Al4V alloy. The inputs of the ANN model were processing times and temperatures, diffusion layer thickness, Ti2N thickness, TiN thickness and hardness. The output of the ANN model was wear loss. The model is based on the multilayer backpropagation neural technique. The ANN was trained with a comprehensive dataset collected from experimental conditions and results of authors. The model can be used for the prediction of wear properties of Ti6Al4V alloys nitrided at different parameters. The ANN model demonstrated the best statistical performance with the experimental results.
Non-Linear Modelling of PM Brake Lining Wear Behaviour
Authors: Istif Ilyas , Isin Ovun , Uzunsoy Erdem , Uzunsoy Deniz
Published: December 2013

The brake friction materials in automotive brake systems play an important role in the overall braking performance of a vehicle. Wear test results have previously been presented for a 1040 steel disc interacting with a PM copper-based brake lining material without and with MoS2 additive at constant applied load and sliding velocity. In this paper, a non-linear model has been developed and compared with a previously developed linear model and experimental results. Nonlinear ARX model structure with sigmoid network having one hidden layer was used to find the best possible results. Linear and non-linear approaches have been applied to simulate the wear behaviour of the brake lining material. Comparative results showed that the nonlinear model provides results closer to the experimental study. Therefore, non-linear process modelling can be used as an effective tool for the prediction of brake lining material properties instead of time-consuming experimental processes.
In-situ-Aufschmelz-Methode zur Bestimmung der Hochtemperatureigenschaften von Stählen
Authors: Djuric Dragan , Höller Christian , Oberroither Michael , Sonderegger Bernhard , Sommitsch Christoph
Published: December 2013

Kurzfassung

Der Vorgang der Erstarrung hat einen wesentlichen Einfluss auf die Mikrostruktur und die Hochtemperatureigenschaften von Stählen. Besonders bei Prozessen des Form- und Stranggusses ist die Gewinnung von Materialkennwerten an der Gussstruktur direkt nach dem Aufschmelzen und Erstarren von großer Bedeutung. Weiters kann man die Heißrissbildung im Laborversuch mit einer vorhergehenden Aufschmelzung realitätsnäher untersuchen. Es werden konventionelle Versuchsmethoden zur Bestimmung von Hochtemperatur-Materialkennwerten wie der Duktilität und Festigkeit von Stählen und eine neue Methodik zur Aufschmelzung von Heißzugproben vorgestellt. Die Aufschmelzung der Proben erfolgt bei dieser Testmethode ohne eine konventionelle Schmelzbadsicherung. Eine ungestörte Temperaturmessung während des ganzen Versuches ist damit gewährleistet.
The Evaluation of Waste Papers for the Ceramic Industry
Authors: Selte Aydin , Guler Kerem Altug , Marsoglu Muzeyyen
Published: December 2013

The aim of this study is the production of the metal tile core using waste paper. Paper which can be recycled many times is one of the most consumed materials in Turkey and all around the world. The reason behind the preference of paper usage is that 80 % of waste paper can be recycled. It has been noticed that recycled paper can be used in ceramic industry, as for instance for roof coverings and tiles, as a low cost raw material. A certain amount of waste paper was soaked with water and turned into pulp followed by a forging process to form the pulp into fibres. The mixture used as raw material for metal tile core production was composed of clay, quartz, and pulp. The raw material was shaped into tiles by slip casting and hand pressing. Tiles were dried, in a drying oven and coated with epoxy resin. Water absorption and bending tests were applied to the final samples.
Dependence of Steel Corrosion Rate on the Machining Emulsion Concentration
Authors: Alar Vesna , Stojanović Ivan , Židov Bruno
Published: December 2013

In today's manufacturing, the emulsions for cooling and lubricating are an extremely important and necessary factor for the performance of machining processes. Depending on their composition, properties and production, emulsions in metal cutting operations have various technology functions such as lubricating the surfaces of the tools, facilitating the process of deformation of the cut layer, improving the quality of machined surface as well as cooling the tool and workpiece by removing the part of the heat created by deformation and friction. Corrosion protection of workpieces and tools during and after treatment is also one of the important functions of technological emulsions for cooling and lubricating. In this paper the effects of different concentrations of three emulsions on the corrosion rate of steel workpieces is reported. The results indicate that a higher concentration of emulsion does not provide better protection against corrosion.
Leichtbau mit Kunststoffen – Ermüdungsverhalten von lang-faserverstärkten Kunststoffen*
Authors: Fleckenstein Johanna , Büter Andreas
Published: December 2013

Kurzfassung

Basierend auf Schwingfestigkeitsuntersuchungen mit Flachproben wurde im Rahmen zweier Projekte der Einfluss der Faserausrichtung und des Faservolumengehalts auf die Schwingfestigkeit von Sheet Moulding Compound (SMC) untersucht. Darüber hinaus wurden hierbei auch verschiedene Spannungsverhältnisse und damit Mittelspannung betrachtet, um so, unter Berücksichtigung der Mittelspannungsempfindlichkeit, ein erstes Materialmodell zur Bemessung von SMC ableiten zu können. Im Rahmen dieser Veröffentlichung kann u. a. auf Basis dieser experimentellen Ergebnisse gezeigt werden, dass SMC eine hohe Schadenstoleranz besitzt.
Vereinheitlichung der linearen Effektivspannungskonzepte mittels des Riesz´schen Repräsentationstheorems (Funktionalanalysis)*
Authors: Zhang Genbao
Published: December 2013

Kurzfassung

Die elastische Spannung korreliert nicht immer direkt mit der Schwingfestigkeit eines Bauteils. Vielfach werden Effektivspannungen basierend auf der elastischen Spannung eingeführt, die zur Korrelierung zwischen der Beanspruchung und Beanspruchbarkeit eines Bauteils dienen. Die Ansätze sind vielfältig, wie das Stützziffer-Konzept, die Methoden der Spannungsmittelung, des kritischen Abstands und des sogenannten Hot-Spots, u. a. Zwischen diesen Ansätzen scheint keine unmittelbare Verbindung zu bestehen. Im vorliegenden Beitrag wird eine allgemeine Theorie für die Methode der Effektivspannung vorgestellt, die auf der Funktionalanalysis basiert und Ähnlichkeit zur nichtlokalen Kontinuumsmechanik aufweist. Die Theorie wird auf V-Kerben und Schweißnähte angewandt. Dabei werden detaillierte Vergleiche zwischen den verschiedenen Methoden vorgenommen.
Quantifizierung des Kerbeinflusses bei der Korrosionsermüdung
Authors: Salber Stephan , Ertelt Hans-Jürgen
Published: December 2013

Kurzfassung

Bedingt durch die Bauteilgeometrie oder Belastungsart kann es in einem hochbelasteten Querschnitt eines Bauteils zu einer inhomogenen Spannungsverteilung kommen. Dabei sinkt in der Regel die Nennspannungsdauerfestigkeit im Vergleich zu einem homogen beanspruchten Werkstoff ab. Für den Fall, dass keine Korrosionsvorgänge stattfinden, ist bekannt, dass es bei inhomogenen Beanspruchungen häufig zu Stützwirkungen kommt. Am Beispiel einer Aluminium-Knet- und einer Druckgusslegierung wird gezeigt, dass auch für den Fall der Korrosionsermüdung eine „korrosive Stützziffer“ definiert werden kann, die ähnlich wie die bereits für trockene Umgebungsbedingungen bekannte Stützziffer vom vorherrschenden Spannungsgradienten und von der Werkstofffestigkeit abhängt. Damit ist es möglich, aus einer Werkstoffwöhlerlinie eine Bauteilwöhlerlinie rechnerisch abzuleiten und weitere Bauteildimensionierungen unter Berücksichtigung der Korrosionser­müdung durchzuführen.
Festigkeitskennwerte und mehrachsige Schwingfestigkeit von lamellarem Gusseisen
Authors: Klubberg Franz , Broeckmann Christoph , Beiss Paul
Published: December 2013

Kurzfassung

Vorgestellt werden analytische und experimentelle Untersuchungen zum Ermüdungsverhalten von Gusseisen mit Lamellengraphit (GJL). Neben statistisch abgestützten Kennwertfunktionen für die zur Festigkeitsrechnung maßgeblichen Eingangsgrößen und zum Einfluss von Normal- und Torsions-Mittelspannungen, wurden Versagensgrenzen für GJL unter zweiachsig schwingenden Lastspannungszuständen durch Rechnung und Versuche verifiziert.
Numerical and Experimental Investigations on the Defect Tolerance of Brazed Steel Joints
Authors: Lis Adrian , Koster Michael , Leinenbach Christian
Published: December 2013

Based on the combination of FE-calculations and experimental results a defect assessment procedure for brazed steel joints was developed in the present work, which reliably takes into account the effect of different steel heat treatments and defined artificial defects in the braze layer. Tensile tests with defect free joints consisting of X3CrNiMo13-4 as substrate material and of Au-18wt.-%Ni as filler metal serve as a basis to simulate the elastic-plastic material behaviour. By correlating experimental and numerical methods, failure criteria could be derived which indicate and predict failure of brazed components. These failure criteria were also presumed to calculate the maximum tolerable loads for specimens containing different defects. The results show that the simulations correlate very well with the experimental results. Furthermore, they provide a possibility to analyze the failure behaviour for different defect types and the influence of different heat treatments on the joint strength.
Observation of the Fatigue Crack Propagation Rate of an Aluminum Alloy Specimen under Fatigue Spectrum Loadings
Authors: Abdullah Shahrum , Zakaria Kamarul Ariffin , Ghazali Mariyam Jameelah
Published: December 2013

This paper presents an assessment on fatigue crack propagation (FCG) behaviour and fractography observation of an aluminum alloy that was exposed under spectrum loadings. The FCG test has three types of cyclic loadings, namely, constant-amplitude loading (CAL) as well as high-to-low and low-to-high sequence loadings. All three have been performed with the Al6061-T6 specimens. The tests were performed using a 100 kN servo-hydraulic fatigue testing machine according to ASTM E647 standard. The results show that fatigue crack propagation and its fractography were influenced by the load interaction and the sequence, which affect the fracture behaviour of aluminum alloys. The fracture surface exhibited irregular local striation spacings under the spectrum loading. Moreover, the micrographs show increased plasticity throughout the crack propagation compared to CAL.
Experimental Investigation of VHCF of Polymer Composites: Two Alternative Approaches*
Authors: Julian Adam Till , Horst Peter , Lorsch Paul , Sinapius Michael
Published: December 2013

The need for reliable fatigue predictions arises with an increasing application of fibre-reinforced composites in primary light-weight structures with intended service times of up to 30 years. Only few data about very high cycle fatigue (VHCF) of polymer composites are available, because VHCF testing is rather challenging due to time consuming tests. Moreover, problems arise when testing at high frequencies. Two alternative approaches are presented in this article, a bending test rig for high-frequency testing of flat specimens and a resonant test rig for tube specimens.
Effect of Co Addition to Heat- Treated P/M 316L Stainless Steel on α′-Martensite Formation and Mechanical Properties
Authors: Pichaiwong Nantawan , Wangyao Panyawat , Lothongkum Gobboon , Visuttipitukul Patama , Asavavisithchai Seksak , Tongsri Ruangdaj , Chuankrerkkul Nutthita
Published: December 2013

The effect of various Co additions to P/M 316L stainless steel on α ’-martensite formation and mechanical properties (bending strength and hardness) were investigated. Powder mixtures were compacted using a single action press at 498 MPa and sintered at 1,300°C for 30 min under hydrogen atmosphere, followed by heat-treating in air at 800°C and 900°C for 25 h, 50 h, 75 h, and 100 h, respectively. It is found that oxide formation in closed pores at high temperatures can induce the α ’-martensite formation and reduce the area fraction of porosities, resulting in higher hardness of the heat-treated specimens than that of the sintered specimens. The Co additions can also reduce the amount of α ’-martensite. Long-term heating results in a slight decrease of bending strength due to high connected oxide formation in the internal pores.
Greenhouse Gas (GHG) Reduction Technologies and Applications in Automotive Industry
Authors: Kulekci Mustafa Kemal , Yelken Tugba , Esme Ugur , Buldum Baris
Published: December 2013

Greenhouse gas (GHG) emissions cause global warming and climate changing. This review summarizes the up-to-date applications that contribute to greater fuel economy and reduce CO2 emissions. A detailed explanation of the recent developments in the main concepts of fuel economy and CO2 reducing in automotive industry is given with a special relation to the materials to be selected. In the study, the past, present and future projection of fuel economy and CO2 emission is evaluated. The result of the study conclude that mass of the vehicle, kind of energy for engine, driving techniques and the technology level of the vehicles affect the fuel economy and CO2 emissions.
Effect of Alloying Elements on the Tooling Capabilities of High Speed Steels Fabricated by Powder Metallurgy
Authors: Toptop Guven Orkun , Kisasoz Alptekin , Karaaslan Ahmet
Published: December 2013

SPM 10 and ASP 2052 alloys fabricated by powder metallurgy have a higher alloying elements content than rolled types. Such higher alloying contents improve the mechanical properties of tool steels and provide a longer tooling life. In this study, the effects of alloying elements and different heat treatments processes on the properties of SPM 10 and ASP 2052 were investigated. Also, the effects of alloying elements and process parameters on the mechanical properties as well as tooling abilities of the specimens were studied. The specimens were characterized by Rockwell hardness tests and the tooling abilities of the specimen were determined by characterizing the number of screws that could be fabricated with specimens. According to the results of the experiments, higher hardness values were obtained at elevated austenitization temperatures. Besides, the presence of Co as an alloying element evolved better hot work properties of the specimens.
Development of Novel Luminescent Materials with High Quality Blue Light-Emitting Properties Based on Zinc Oxides
Authors: Zhang B. R. , Yu H.Y. , Rong Cheng
Published: December 2013

ZnO:Tm,Gd materials with high quality blue light-emitting were successfully prepared using the chemical co-precipitation method. The surface morphology, composition, crystal structure and fluorescence properties were investigated using the thermogravimetric analysis/differential thermal analysis (TG/DTA), scanning electronic microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL). The results showed that the lowest sintering temperature was 580°C, the optimal sintering temperature was 900°C, ZnO:Tm3+, Gd3+ had two emission peaks: 1 D2 → 3 H4 and 1 G4 → 3 H6, the optimal heat preservation time was 3 h, the proportion of matrix and doping elements was 100: 2, and the optimal proportion of Tm and Gd was 3: 2.
Pt-Rh Alloys: Investigation of Creep Rate and Rupture Time at High Temperatures
Authors: Trumić Biserka , Gomidželović Lidija , Marjanović Saša , Krstić Vesna , Ivanović Aleksandra , Dimitrijević Silvana
Published: December 2013

The results of experimental investigation of creep rate and rupture time of the alloys of Pt-Rh system are presented in this paper. Selected alloys with 7–40 wt.-% Rh content were examined using a universal device for tensile testing of materials at high temperatures, and monitoring structure changes of the samples by electron microscopy. Investigations were performed in the temperature range between 1200°C and 1700°C at a stress between 2 MPa and 15 MPa.
Creep Behaviour of NearEquiatomic Nickel-Titanium Wires
Authors: Eker Aysegul Akdogan , Sonmez Deniz , Kucukyildirim Bedri Onur
Published: December 2013

The creep behaviour of near-equiatomic (50.8 at.-% Ni) NiTi wire with a diameter of 0.49 mm is studied between 82 MPa and 127 MPa tensile stress as well as in a temperature range of 575 °C to 650 °C. For 600 °C and between 82–107 MPa a stress exponent of n = 4.5 as well as for 82 MPa between 600–625 °C an activation energy of Q = 300 kJ mol-1 have been found, these results have been compared with previous creep studies. In contrast to previous studies, this investigation has been performed with high stresses for thin NiTi wires. Moreover, fracture surfaces and ductility of wires have been investigated. The main reasons for the various results are discussed.
A Study on Wear Testing of Orthopedic Implant Materials in Simulated Body Fluid
Authors: Atar Erdem
Published: December 2013

In this study, the sliding wear behaviour of the materials utilized in manufacturing of load-bearing orthopedic implants (316 L, Ti6Al4V, and CoCrMo nickel alloys) was examined by a reciprocating wear tester under ceramic-on-metal configuration in a simulated body fluid (SBF). During the tests the generated wear debris were transferred into the SBF and increased its optical density. In accordance with its poor wear resistance, Ti6Al4V alloy provided a large amount of wear debris transfer into the SBF along with the heavy material attachment to the contact surface of the counterface. Dissolution of wear debris led to an increase of the metal ion concentration in the SBFs. Even though few wear debris were generated, trace elements were detected in the SBFs of the 316 L and CoCrMo alloy, besides the main elements.
Assessment of Fatigue Behaviour under Different Loading Sequences Using Signal Analysis Approaches
Authors: Padzi Mahfodzah Md , Abdullah Shahrum , Nuawi Mohd Zaki
Published: December 2013

Constant amplitude data obtained from smooth specimens have been used for many years to evaluate the fatigue life of components. However, most of the loadings used in real applications are variable or random. In this research, three types of loading were applied – constant, low–high (LH), and high–low (HL) loading sequences. This paper presents an assessment of the fatigue behaviour under these three types of loading, and the effects of each loading on the fatigue behaviour as well as on life are highlighted. Fatigue tests were performed according to ASTM E466-96 standard with a strain gauge attached to the specimen being tested. AISI 1045 carbon steel was used as material for this tests due to its wide applications in the automotive industry. Fatigue tests were carried out at a constant, LH, and HL loading stresses at a sampling frequency of 8 Hz. A set of data acquisition system was used to collect the fatigue strain signals. All signals obtained were analyzed using two signal-processing approaches – the power spectral density (PSD) method and the integrated Kurtosis-based algorithm for Z-filter (I-kaz) technique. Fatigue behaviour was observed from the initial until the last stage of the fatigue test. The PSD peak values and I-kaz coefficients were determined to explain and describe the behaviour of fatigue damage. Both results are comparable in the fatigue damage assessment.
Effects of Wax Coating on the Surface Quality of EPS Patterns for Solid Mould Investment Casting
Authors: Guler Kerem Altug
Published: December 2013

Expandable polystyrene (EPS) foam has been a well-known pattern material for a long time in the investment casting process, however it always suffers from insufficient surface finish compared to wax patterns. In this study, EPS foam patterns were coated with waxes and the effects of such coating on the surface quality were investigated. Cubic shaped EPS patterns were coated with liquid ordinary candle wax (c-wax) and commercial pattern wax (p-wax). These patterns and an uncoated pattern were used to prepare plaster bonded solid investment casting moulds and a A319 aluminium alloy was casted into these moulds. Average surface roughness (Ra) of the patterns, moulds internal surfaces and cast parts were measured, cross sections of the coated patterns were investigated by optical microscopy and the coating thicknesses were measured with an image analyser. As an obvious result, wax coating significantly increases the surface quality and the p-wax creates smoother, while the c-wax creates more uniform coating films.
Production of Self-Compacting Lightweight Concrete with Pumice Aggregate
Authors: Açıkel Hicran , Günaydın Murat
Published: December 2013

This study aimed to produce self-compacting normal weight concrete by the use of lightweight aggregate, which has become more widespread, as Turkey has many natural lightweight aggregate sources. Nevşehir pumice aggregate was used in the tests. The characteristics of fresh concrete incorporating additives as fly ash and super plasticizer were determined via self-compacting concrete tests such as slump flow, V-funnel and L-box flow. Compression, flexure and split tests were conducted on cube, cylinder and girder samples produced with the concrete. The test results and strength data showed that self-compacting lightweight concrete could be produced by the methods used in this study.
Tomografische Methoden für die Brennstoffzellenforschung∗
Authors: Arlt Tobias , Grothausmann Roman , Manke Ingo , Markötter Henning , Hilger André , Kardjilov Nikolay , Tötzke Christian , Banhart John , Kupsch Andreas , Lange Axel , Hentschel Manfred P. , Krüger Philipp , Haußmann Jan , Hartnig Christoph , Wippermann Klaus
Published: December 2013

Kurzfassung

Aufgrund des hohen Wirkungsgrades und der vielfältigen Einsatzmöglichkeiten können Brennstoffzellen einen wichtigen Beitrag zur zukünftigen Energieversorgung leisten. Für die Optimierung der Brennstoffzellentechnik ist es erforderlich, die während des Zellbetriebs ablaufenden Prozesse zu verstehen und exakt zu charakterisieren. Ein ausbalanciertes Wassermanagement ist die Grundlage für die optimale Leistungs­fähigkeit einer wasserstoffbetriebenen Zelle. Das während des Betriebs entstehende Wasser muss die Membran ausreichend befeuchten, um deren Protonenleitfähigkeit aufrechtzuerhalten. Andererseits behindern zu große Wasseransammlungen in der Zelle die Gaszufuhr durch die porösen Materialien sowie in den Kanälen der Gasverteilerstrukturen. Alterungsphänomene einzelner Zellkomponenten können die Verteilung der Wasseransammlungen und somit das Wassermanagement empfindlich stören und so die Leistungsfähigkeit der Brennstoffzelle herabsetzen. Zur Analyse der Wasserverteilung werden zerstörungsfreie, bildgebende Methoden, wie die Ex-situ-Neutronentomografie und die In-situ-Synchrotronradiografie, eingesetzt. Diese Methoden können während des Brennstoffzellenbetriebs mit weiteren Messverfahren, beispielsweise der ortsaufgelösten Stromdichtemessung, kombiniert werden. Auf diese Weise werden einzelne Komponenten, wie zum Beispiel die Gasdiffusionsschichten, charakterisiert.
Experimental Study of Imida zoline as an Inhibitor of Carbon Steel in Acid Media
Authors: Alar Vesnar , Juraga Ivan , Stojanoviæ Ivan , Šimunoviæ Vinko , Borko Tihomir
Published: December 2013

The electrochemical behaviour of a carbon steel in deaerated acid media with concentrations of 20 ppm, 50 ppm, 100 ppm and 200 ppm imidazoline at different temperatures and with different stirring rates has been evaluated by using anodic and cathodic polarization curves (Tafel) and electrochemical impedance spectroscopy (EIS) to compare the corrosion inhibition efficiency. The experimental results suggest that imidazoline is a good corrosion inhibitor at 50 ppm concentration.