bluuebunny/crossref_metadata_2025 huggingface dataset:
Röntgen-Kanten-Tomografie und -Radiografie zur Untersuchung von Alterungseffekten in Brennstoffzellenmaterialien
Authors: Arlt Tobias , Manke Ingo , Wippermann Klaus , Schröder Alexander , Mergel Jürgen , Riesemeier Heinrich , Banhart John
Published: December 2013

Kurzfassung

Die Korrosion von Ruthenium ist eine der Hauptursachen für die Alterung von Direkt-Methanol-Brennstoffzellen (DMFC). Mittels monoenergetischer Synchrotronstrahlung wird gezeigt, dass der in DMFC-Anoden enthaltene Co-Katalysator Ruthenium nach einem beschleunigten Alterungstest eine Umverteilung in der Anodengasdiffusionselektrode zwischen Bereichen unter Kanälen und unter Stegen erfährt und von der Anode zur Kathode gelangt. Für die tomographischen Untersuchungen wurden Proben aus einer gealterten Membran-Elektroden-Einheit (MEA) herauspräpariert und ex situ untersucht. Es wird gezeigt, dass diese Umverteilungen auf den Stofftransport in der MEA und die Struktur der Gasdiffusionsschicht (GDL) zurückgeführt werden können.
Charakterisierung von Katalysatormaterialien für Brennstoffzellen mittels Elektronentomografie
Authors: Grothausmann Roman , Manke Ingo , Zehl Gerald , Dorbandt Iris , Bogdanoff Peter , Fiechter Sebastian , Hentschel Manfred P. , Lange Axel , Kupsch Andreas , Hilger André , Banhart John
Published: December 2013

Kurzfassung

Zur Optimierung moderner Katalysatoren für Brennstoffzellen werden diese elektronen-tomografisch charakterisiert. Die Elektronentomografie ermöglicht einzigartige Einblicke in die Nanometer-Strukturen der metallischen Katalysatorpartikel, die auf einem elektrisch leitenden, inerten Kohlenstoffträger abgeschieden werden. Die dreidimensional bildgebende Methode ermöglicht über qualitative Untersuchungen hinaus detaillierte quantitative Form- und Strukturanalysen der Katalysatormaterialien. So werden beispielsweise die Positionen der Katalysatorpartikel relativ zum Trägermaterial analysiert. Ihre Form und Einbettung in den Träger, welche die für die katalytische Reaktion maßgebliche „freie Oberfläche“ definieren, werden bestimmt. Die Elektronentomografie ermöglicht somit quantitative Vergleiche zwischen verschiedenen Katalysatormaterialien und Herstellungsverfahren. Sie erweitert die Möglichkeiten der Korrelation gewünschter elektrochemischer Eigenschaften mit der Nanostruktur dieser Materialien und macht so weitere Optimierungen der Katalysatormaterialien möglich.
Werkstoffprüfung an Mikroproben und -halbzeugen
Authors: Köhler Bernd , Bomas Hubert , Zoch Hans-Werner , Stalkopf Jens
Published: December 2013

Kurzfassung

Der Sonderforschungsbereich 747 „Mikrokaltumformen – Prozesse, Charakterisierung, Optimierung“ der Deutschen Forschungsgemeinschaft (DFG) beschäftigt sich seit 2007 mit der Bereitstellung von Prozessen und Methoden für die umformtechnische Herstellung metallischer Mikrokomponenten. Im Teilprojekt B4, Bauteilfestigkeit, in dem drei der Autoren arbeiten, geht es um die statische und dynamische Untersuchung der mechanischen Eigenschaften von Mikroproben und -halbzeugen. Die Prüfung derartiger kleiner Prüflinge erfordert eine an deren Dimensionen angepasste Prüftechnik. Vor dem Hintergrund dieses besonderen Anforderungsprofils werden die infrage kommenden unterschiedlichen Prüfmaschinenklassen vergleichend diskutiert. Zur Durchführung des genannten Projekts wurde ein Prüfsystem beschafft, welches am geeignetsten erschien, bestehend aus der elektrodynamischen Prüfmaschine des Typs Instron ElectroPuls™ E1000 und dem berührungslos arbeitenden Videoextensometer AVE. In diesem Artikel werden einige Erfahrungen mit diesem Prüfsystem beschrieben.
Material Composition Optimization of FGM Plates Containing a Hole
Authors: Hedia Hassan S. , Aldousari Saad M. , El Midany Tawfik T.
Published: December 2013

By definition, Functionally graded materials (FGM) are new advanced composite materials which are used to produce components featuring engineered gradual transitions in microstructure and/or composition. FGMs permit tailoring of material composition so as to derive maximum benefits from their inhomogeneity. The aim of the study behind this contribution is to optimize the composition variation between the ceramic and the metal in order to minimize the maximum stress concentration around the hole in a plate made of FGMs in case of the plate is subjected to pressure, heating or both pressure and heating. The finite element method (FEM) has been used to optimize the material composition of functionally graded materials made from Al 1100 as the metal portion and SiC as the ceramic portion using the ANSYS package. The objective has been to minimize the stress concentration factor around a hole in a plate expressed by the ratio between the principal stress calculated by the ANSYS and the applied stress at different volume fractions of the metal and the ceramic. The investigations have shown that when applying pressure or heating to the plate the optimum for minimizing the stress concentration is to have a ceramic-rich plate and when the plate is subjected to both pressure and heating the optimality is to have a metal-rich plate.
Effects of Binder and Water Contents on Extrusion Behavior of Zeolite
Authors: Kim Jongmin , Kang Kyoung-Hoon , Lee Sungkyu , Seo Min Hye , Cho Sung-Su , Choi Ho Sang
Published: December 2013

Effects of binder and water contents on extrusion behavior of a 100 CPSI (cells per square inch) square lattice channel honeycomb-type zeolite monolith support with 0.59 mm wall thickness and an overall cross-sectional square area of 100 cm2 have been studied. Process variables for successfully processing the green-body were first optimized, but drying condition of the green body turned out to be more crucial in successful fabrication of the calcined honeycomb-type support. Overall, the addition of processing additives such as 2.4 wt.-% of organic binder, 17.6 wt.-% of distilled-water to 60.0 wt.-% natural zeolite paste exhibited low exit pressure and contributed to successful fabrication of honeycomb-type zeolite monolith green body. The green bodies thus fabricated were dried for about 140 h under 95% relative humidity at 60 °C before final calcination treatment for 2 hr at 600 °C.
Bio-Medical Materials in Human Joint Implants — A Review
Authors: Hedia Hassan S. , Najjar Ismail M. R.
Published: December 2013

Since the introduction of aseptic surgery by Lister towards the end of the eighteenth century, engineering materials have been implanted into the human body in many forms. Implant surgery has developed to the extent that implants are now used in most branches of surgery and are becoming increasingly more sophisticated. Orthopaedic surgery probably uses more implants than any other branch of medicine. Fracture fixation being one of the oldest and most common applications. This literature review tries to inclusively summarize the recent development in bio-medical materials and its applications in human joint implants up to year 2010.
Production of Open Cell Aluminium Metal Foam with Lost Foam Technique
Authors: Güler Kerem Altug , Taslicukur Zeynep , Özer Gökhan
Published: December 2013

Metallic foams represent materials with low densities as well as good physical, mechanical, thermal, and electrical properties. Since they have pores, metal foams have a set of unusual properties compared with bulk structural materials, i. e. the can offer a unique combination of several properties that can not be obtained in one conventional material at the same time. Metal foams can be produced by different processing technologies and many of them are still under development. The lost foam technique is an alternative foundry process as compared to other conventional techniques. This paper reports about a new approach for the production of open-cell aluminium foam metal by such casting procedure. During the process, an expanded polystyrene cell has been used for pattern making and all critical steps for manufacturing open-cell metal foam by the new technique are described in detail.
Beanspruchungskollektive für Nutzfahrzeuge in Gesamteuropa*
Authors: Schindler Martin , Dietrich Jakob , Streicher Manfred
Published: December 2013

Kurzfassung

Die beanspruchungsgerechte Auslegung von Nutzfahrzeug-Komponenten erfordert gute Kenntnis zu erwartender harter Kundeneinsätze. Je größer der Streubereich möglicher Einsätze ausfällt, desto wichtiger wird die Überprüfung vorhandener Auslegungsstrecken hinsichtlich ihrer Eignung. Werden Fahrzeuge in bisher wenig bekannten Regionen verwendet, müssen Lasten ermittelt werden. Die Definition eines sogenannten 1%-Kundeneinsatzes wird überprüft und gegebenenfalls neu festgelegt.

Ein Ansatz zur Bestimmung von Bemessungskollektiven ist die statistische Auswertung klassierter Schwingspielhäufigkeiten von Messabschnitten gleicher Streckenlänge, welche durch Kombination zu charakteristischen Einsatzstrecken eine quantifizierbare Abschätzung der Betriebsbeanspruchung in Kundeneinsätzen festgelegter Gesamtfahrleistung erlauben.
Zur Auswertung von Schwingfestigkeitsversuchen im Zeitfestigkeitsbereich —
Authors: Martin Andreas , Hinkelmann Karsten , Esderts Alfons
Published: December 2013

Kurzfassung

Experimentell ermittelte Wöhlerlinien bilden häufig die Grundlage eines Ermüdungsfestigkeitsnachweises. Der vorliegende Beitrag soll zum einen den Anwender dafür sensibilisieren, dass trotz präziser Fertigungsverfahren, exakter Prüftechnik, gleicher Chargen usw. Versuchsergebnisse streuen und somit immer nur eine Schätzung der Wöhlerlinie vorliegt. Zum anderen werden die Einflussgrößen auf die Vorhersagegenauigkeit von Wöhlerlinien im Zeitfestigkeitsbereich untersucht. Insbesondere wird auf den notwendigen Stichprobenumfang, die Aufteilung der zur Verfügung stehenden Prüfkörper und die Versuchsauswertung eingegangen. Die Fortpflanzung der Schätzfehler wird mit einer anschließenden Schadensakkumulationsrechnung bewertet. Aus den Untersuchungen werden Hinweise für die Versuchsdurchführung und Auswertung von Schwingfestigkeitsversuchen im Zeitfestigkeitsbereich abgeleitet. Teil 1 behandelt die Schätzung von 50%-Wöhlerlinien; in Teil 2 wird auf die Schätzung der Streuung näher eingegangen.
Einfluss von Zusätzen auf phosphatgebundene hoch tonerdehaltige feuerfeste Materialien
Authors: Yesiltas Ersin , Genc Yasin , Yeprem H. Aygül
Published: December 2013

Kurzfassung

In der Studie für diesen Beitrag wurde das Eindringen von Al-Schmelze in hochtonerdehaltige Feuerfest-Materialien auf Basis Aluminium-Silikat untersucht. Die Wirkung des flüssigen Aluminiums — legiert mit 5 wt.-% Magnesium und folglich Bildung einer aggressiven Umgebung — auf hoch tonerdehaltige feuerfeste Steine wurde untersucht. Die Steine wurden bei 825°C getempert oder bei 1350°C gebrannt. Die Untersuchung bezüglich des Eindringens beruhte auf dem Tiegeltest gemäß DIN 51069. Hier wurden Proben mit Zusätzen von Phosphorsäure, Phosphorsäure und Bariumsulfat, Phosphorsäure und Bariumsulfat und Borsäure physikalisch und analytisch untersucht. Diese Arbeit fokussiert sich auf das Thema, wie Zusätze von Phosphorsäure, Baryt und Borsäure, phosphatgebundene, hoch tonerdehaltige Feuerfest-Steine beeinflussen und gegen das Eindringen von Al schützen. Für die Eindringenstests wurden hoch tonerdehaltige feuerfeste Materialien auf Bauxit-Basis als Referenzsteine verwendet.
Weld Metal Grain Refinement of Aluminium Alloy 5083 through Controlled Additions of Ti and B
Authors: Schempp Philipp , Schwenk Christopher , Rethmeier Michael , Edward Carl
Published: December 2013

The refinement of the weld metal grain structure may lead to a significant change in its mechanical properties and in the weldability of the base metal. One possibility to achieve weld metal grain refinement is the inoculation of the weld pool. In this study, it is shown how additions of titanium and boron influence the weld metal grain structure of GTA welds of the aluminium alloy 5083 (Al Mg4.5Mn0.7). For this purpose, inserts consisting of base metal and additions of the master alloy Al Ti5B1 have been cast, deposited in the base metal and fused in a GTA welding process. The increase of the Ti and B content led to a significant decrease of the weld metal mean grain size and to a change in grain shape. The results provide a basis for a more precise definition of the chemical composition of commercial filler wires and rods for aluminium arc welding.
TIG Riveting of Temperature Sheath Microprobe
Authors: Burcă Mircea , Liţă Marin , Cucuruz Laurenţiu Roland
Published: December 2013

In order to close one of the microprobe ends covering, considering geometrical sizes and the properties of the material, the electro riveting process by TIG welding was chosen. The semi spherical shape of the end closed by welding supposed a pre-preparation of the end and an adequate positioning of gun and covering so that the material burning was avoided and the process automatically developed. Macroscopic investigations related to the geometrical shape of the closed end allowed the optimization of the welding process and the structural investigations made by optical microscopy and X-rays diffraction evinced the structural transformations of the material, supplying information for the post welding heat treatment to increase the corrosion resistance characteristics of the covering.
Artificial Neural Network (ANN) Approach to Hardness Prediction of Aged Aluminium 2024 and 6063 Alloys
Authors: Meyveci Ahmet , Karacan İsmail , Durmuş Hülya , Çalıgülü Uğur
Published: December 2013

In this study, the effect of aging heat treatment on the hardness of AA 2024 and AA 6063 aluminum alloys was investigated by experimental and an Artificial Neural Network (ANN). AA 2024 and AA 6063 aluminum alloys were solution treated at two different temperatures of 490° C and 520° C. Then both samples were cooled to room temperature. After this process, the samples were aged at three different temperatures (140° C, 180° C, 220° C) for ten different periods of time (2, 4, 6, 8, 10, 12, 14, 16, 18, and 20 h.). The experimental results were trained in an ANNs program, and the results were compared with experimental values. It is observed that the experimental results coincided with the ANNs results.
Cavitation Erosion Behaviour of Stainless Steels with Constant Nickel and Variable Chromium Content
Authors: Bordeasu Ilare , Mitelea Ion
Published: December 2013

The paper highlights new aspects in the evaluation of cavitation erosion resistance based on the chromium content variation and implicit on the Cr/Ni equivalent which constitutes the microstructure development using the information given by the Schaeffler diagram. The presented and analysed results show that it is possible to establish an optimum relation between the chromium and nickel content, in order to obtain a substantial increase of the cavitation erosion resistance. For this purpose, four stainless steels used in manufacturing of machinery parts, heavily subject to cavitation such as hydraulic turbine runners and pump impellers, were analyzed from the point of view of cavitation erosion. The cavitation erosion behaviour was evaluated by the microstructure behaviour investigated through optic and electronic microscopy and by comparisons with the characteristic curves for reference steels.
Weldability Characteristics of Dissimilar Al/Cu Friction Stir Weld Joints
Authors: Sarsilmaz Furkan
Published: December 2013

In the present investigation, the AA1030 aluminium alloy and commercially pure copper plates were joined by friction stir welding. The effect of the processing parameters on the interface morphology, microstructure and strength of the joints was analyzed. The experimental results showed that some intermetallic compounds such as AlCu, Al4Cu9 and Al2Cu cause the weld to crack during the friction stir welding process on the centerline of the weld. Especially at lower traverse speeds such as 60, 90, and 125 mm/min, some tunnels and voids were detected in the Aluminium close to the Al/Cu interface. The maximum tensile strength of the samples was obtained at a traverse speed of 160 mm/min getting by without cavity defects in the weld. In addition, the fracture morphology revealed both partially brittle and cleavage-like fracture.
Correlation Between Work Index and Mechanical Properties of some Saudi Ores
Authors: Haffez Gamal S. Abdel
Published: December 2013

The crushing energy for applications in the mineral processing industry is usually determined by an empirical bond index, regardless of the mechanical properties of a rock. Although several attempts have been made to obtain the comminution energy based on theoretical approaches, it would be beneficial to examine this relation based on a physical concept. In this paper, some Saudi samples of bauxite, kaolinite, granodiorite, magnetite, granite, feldspar and quartz were tested for hardness, abrasion, compressive strength as well as modulus of elasticity and the bond work index of these samples was estimated. The value of the bond work index of the above samples has shown a variation from 10.8 kWh ton-1 for bauxite (high abrasion value and low compressive strength) to 20.4 kWh ton-1 for granite (low abrasion value and high modulus of elasticity). The correlation between the abrasion value (X2) and work index (Wi) is found to be Wi = −1.8 Ln(X2) + 11.5 with a correlation coefficient of 0.80.
TMF Cracking in Metallic Heat Shields of Gas Turbine Combustion Chambers
Authors: Neidel Andreas , Cagliyan Erhan , Jahnke Anne , Riesenbeck Susanne , Ullrich Thomas , Wallich Sebastian
Published: December 2013

Several metallic heat shields of the combustion chamber of a large industrial gas turbine were affected by thermo-mechanical cracking after long service exposure. The base metal Alloy 617 is coated with a thermal barrier system. While microstructural evidence allowed the exclusion of creep damage as the metallurgical cause of failure, other microstructural features led to the conclusion that the affected components were massively overheated and experienced service temperatures of up to 1100 °C. There are several possible reasons for such overheating, ranging from burner failure and lack of cooling to abuse in service. A discussion of these factors is not the subject of this case study.
Ein neues Verfahren zur präzisen Analyse des diffusiblen Wasserstoffanteils in Stählen
Authors: Kühn Sebastian , Luithle Alexander , Unterumsberger Fabian , Pohl Michael
Published: December 2013

Kurzfassung

Hochfeste Stähle mit einer kubisch raumzentrierten Gitterstruktur können bereits bei sehr geringen Wasserstoffgehalten zur verzögerten Rissbildung neigen. Zum sicheren Einsatz dieser Stähle ist deshalb die Kenntnis des enthaltenen diffusiblen Wasserstoffes notwendig, der sich schadensursächlich auswirken kann. In diesem Beitrag wird die Funk­tionsweise eines neuen Wasserstoffanalyseverfahrens beschrieben, welches sich in der Verfahrensabfolge von konventionellen Verfahren, wie der Trägergasheißextraktion bzw. Trägergasschmelzextraktion, unterscheidet. Bei dem entwickelten Verfahren, der sogenannten Hydrogen Collecting Analysis (HCA), werden die zu analysierenden Proben in Glasküvetten eingeschmolzen und die Wasserstoffextraktion aus der Probe und die Wasserstoffanalytik in zwei konsekutive Verfahrensschritte unterteilt. Mit dem HCA-Verfahren können die Anteile an diffusiblem Wasserstoff in Metallproben im Hundertstel-ppm-Bereich hochgenau analysiert werden.
Effect of Pin Penetration Depth on the Mechanical Properties of Friction Stir Spot Welded Aluminum and Copper
Authors: Özdemir Uğur , Sayer Sami , Yeni Çınar
Published: December 2013

The effect of pin penetration depth on the mechanical properties of friction stir spot welded (FSSW) aluminum alloy 1050 and pure copper has been investigated. For a certian tool geometry, constant tool rotation speed and penetration time, the materials have been friction stir spot welded in three different penetration depths, namely 2.8 mm, 4 mm and 5 mm. Tensile shear tests, microhardness measurements and micostructural investigation have been carried out on the welded specimens in order to investigate the effect of penetration depth. 2.8 mm plunge depth has resulted in a weak joint, whereas 4 mm and 5 mm plunge depths offer acceptable tensile shear results. Presence of intermetallic phases had an influence on the tensile shear and hardness values.
Fatigue Life Behaviour of Nanocomposite Coated Carbon Steel
Authors: Hedia Hassan S. , Aldousari S. M. , Khairy A. , Aljabarti Ezat
Published: December 2013

Recently, nano-materials have received increasingly more attention for their potential applications as structural and functional materials. The unique mechanical properties of CNTs, their high strength and stiffness and the enormous aspect ratio provide potentials for the improvement of the mechanical properties of structural materials. The aim of this research is to investigate experimentally the effect of nanocom­posite coating on the fatigue life of carbon steel AISI 1045 specimens with different surface finishes. Nanoadhesives of epoxy resin are synthesized and evaluated. They are originally modified by multiwalled carbon nanotubes (MWCNT) with 0.5 wt.-% as reinforcement. Fatigue tests are conducted on the respective specimens by a rotating bending machine of the cantilever type. Comparing the results for specimens coated with 0.5 wt.-% MWCNT-epoxy composition with the base materials it is found that fatigue life increased five times for a roughness of 0.3 µm and three times for an average specimen roughness of 0.8, 1.6 and 2.5 µm, respectively.
Surface Roughness Changes and Corrosion on Nickel Titanium Orthodontic Wires Compared to Stainless Steel Wires in Various Artificial Salivas
Authors: Kucukyildirim Bedri Onur , Eker Aysegul Akdogan
Published: December 2013

Nickel titanium shape memory alloy and stainless steel orthodontic wires were exposed to three different artificial saliva solutions which are modified Fusayama, modified Fusayama with 1g/l NaF addition and modified Fusayama with 1.7 % H3PO4 addition. Under conditions similar to oral cavity temperature, corrosion behaviours were observed by using weight loss method and by macro surface photographic observations. Also, surface roughness of wires were investigated and compared. Consequently, it was determined that corrosion rates of all NiTi wires exposed to the modified Fusayama solutions with NaF addition are higher because of galvanic interaction of NiTi and hydrogen embrittlement of titanium. Also, surface roughness of NiTi wires were increased in modified Fusayama solution with NaF addition.
Experimental and Numerical Strategies to Consider Hole Eccentricity for Residual Stress Measurement with the Hole Drilling Method
Authors: Nau Andreas , Scholtes Berthold
Published: December 2013

For the analysis of residual stress depth distributions the semi-destructive incremental hole drilling method is the process of choice for quick and cost-efficient measurements. Nevertheless, the experimental execution has to be carried out carefully. Minor deviations of the ideal case, for example incorrect depth setting or eccentricity of the drilled hole to the center of the applied strain gage rosette can result in large errors or invalid results. In this paper two different strategies are presented, in order to take eccentricity into consideration. The first strategy requires a specific strain gage rosette consisting of eight single strain gages arranged at 45° angle to each other. The second strategy works with standard strain gage rosettes, but with calibration functions modified for the eccentric case. Both strategies are able to reveal and to correct the consequences of eccentricity on the results of stress analyses. In order to improve the quantitative accuracy of residual stress measurements the latter strategy should be preferred.
Rolling Contact Fatigue of Wheel and Rail
Authors: Dörner Florian , Kleiner Otto , Schindler Christian , Starke Peter , Eifler Dietmar
Published: December 2013

This investigation describes rolling contact fatigue phenomena in the wheel/rail-contact area of railway vehicles. In the scope of this paper new calculation, experimental results of stresses and strains within the wheel as well as a new method the determination of fatigue strength are presented. The stress fields in railway wheels introduced by different loads are calculated using the finite element method. The results are validated on a full-scale test rig. The results of the measurements are used to draw conclusions for the fatigue strength of wheels. Furthermore, the fast and cost saving “PHYBALLIT” method for the determination of fatigue properties is described.
Detection of Defects in Natural Composite Materials Using Thermal Imaging Technique
Authors: Suriani M. J. , Ali Aidy , Khalina A. , Sapuan S. M. , Abdullah S. , Haftirman
Published: December 2013

Nowadays, non-destructive testing (NDT) is frequently replacing destructive techniques in determining the properties of materials. In this study, defects in Kenaf/epoxy composite materials were detected using an inyyfrared (IR) thermal imaging technique, which is one of the most practical non-destructive techniques currently applied. Kenaf bast fibres were used to fabricate composite materials with epoxy resin as a binding material. The composites were manufactured using a manual lay-up process. The thermography analysis of the IR camera were verified by optical microscope and scanning electron microscope (SEM) investigations. The defect detection accuracy of this technology is 95%.
Effect of Curing Conditions on the Interface Strength of Single-Fibre Composite Specimens
Authors: Solmaz Murat Yavuz , Kaman Mete Onur , Turan Kadir
Published: December 2013

The purpose of this paper is to examine the effect of curing conditions on interface strength in single-fibre composites. Test specimens produced by using polyester resin and single glass fibre were cured under four different temperatures, which were room temperature, 40°C, 55°C and 70°C for three different curing periods, which were 1 hour, 4 hours and 8 hours. Afterwards they were subjected to tensile test. As a result of the examination under optic microscope, it has been observed that the major damage formations are in the form of matrix cracks and fibre fragments. Young modulus and therefore mechanical properties of single-fibre composite specimens improved after a treatment above 40°C.
Zur Lebensdauerberechnung faserverstärkter Kunststoffe im Automobilbau*
Authors: Oppermann Helge
Published: December 2013

Kurzfassung

Faserverstärkte Kunststoffe finden im Automobilbau zunehmend auch für hochbelastete Bauteile Verwendung. Für die betriebsfeste Auslegung solcher Bauteile müssen zuverlässige Lebensdauerberechnungsverfahren zur Verfügung stehen. Die Methodenentwicklung zur Lebensdauerberechnung von faserverstärkten Kunststoffbauteilen und zu deren Verbindungstechniken steht im Automobilbau noch in den Anfängen. Zwar existieren bereits methodische Ansätze für Teilaspekte der Lebensdauerberechnung, jedoch ist die virtuelle betriebsfeste Auslegung von faserverstärkten Kunststoffbauteilen im Entwicklungsprozess heute noch nicht ohne experimentellen Mehraufwand möglich. Der experimentelle Prüfaufwand ist vergleichsweise zu Metallen bei den Composites aufgrund der Komplexität der Einflussfaktoren (Interlaminare Spannungen, Viskoelastizität, Alterung usw.) je nach Problemstellung deutlich größer. Dieser Aspekt ist auch bei der Methodenentwicklung zur Lebensdauerberechnung unbedingt zu berücksichtigen, d. h., der experimentelleAufwand zur Ermittlung der Materialdaten für die Berechnung darf ein akzeptables Maß nicht überschreiten.
Scanning-Laservibrometrie zur integrierten Bauteilüberwachung mit Hilfe von Ultraschallober­flächenwellen
Authors: Neumann Mirko Nikolaj , Schell Jochen , Lammering Rolf , Behrendt Reinhard
Published: December 2013

Kurzfassung

Ultraschall-Lamb-Wellen werden aktuell als vielversprechende Möglichkeit zur Schadensdetektion in dünnwandigen Strukturen untersucht. Um die physikalischen Phänomene technisch gut ausnutzen zu können, ist das Ausbreitungsverhalten der Wellen und ihre Interaktion mit Defekten zu untersuchen. Gut geeignet hierfür sind optische Messtechniken, die sich durch Rückwirkungsfreiheit auf die mechanischen Strukturen auszeichnen – zum Beispiel die Laservibrometrie. Die Technik liefert im Scanning-Verfahren flächige, zeitkontinuierliche Schwingungsdaten zur Beurteilung der Wellenfelder. Im 3D-Scanning-Verfahren sind hierbei In-Plane- und Out-of-Plane-Schwingungen voneinander unterscheidbar, während sich die Verschiebungsinformationen bei der 1D-Vibrometrie bezüglich der Ortsrichtung vermischen, was zu Fehlinterpretationen führen kann. Lamb-Wellen in isotropen Platten und Faserverbundplatten werden kurz beschrieben und ihre Beobachtung mittels (3D-)Scanning-Vibrometrie vorgestellt. Ein kurzes Experiment mit transient angeregten Lamb-Wellen zur Detektion von Impact-Schäden in einer CFK-Platte wird vibrometrisch beobachtet und beschrieben, wobei eine gute Eignung von Lamb-Wellen zur Struktur­überwachung festgestellt wird.
Impact of High Pressure Hydrogen Atmosphere on the Mechanical Properties of Haynes 282 Superalloy
Authors: Bruchhausen Matthias , Fischer Burkhard , Hähner Peter , Soller Sebastian
Published: December 2013

Haynes 282 alloy is a newly developed nickel-base superalloy, with properties focussed on high creep strength, thermal stability, good weldability and fabricability, which might qualify it as a substitute for established materials like Hastelloy-X or René-41 e.g. in aerospace applications. However, so far no information on the sensitivity for hydrogen environment embrittlement (HEE) has been published for this material. In the present work, tensile tests under hydrogen atmosphere have been carried out at room temperature and the results have been compared to those from tests under argon. Haynes 282 is found to show significant hydrogen embrittlement.
Microstructure and Mechanical Behaviour of Friction Welded AISI 2205/AISI 1040 Steel Joints
Authors: Kirik İhsan , Özdemir Niyazi , Sarsilmaz Furkan
Published: December 2013

The goal of this study is to investigate the effect of friction time on mechanical and microstructural properties of dissimilar AISI 1040/AISI 2205 stainless steel couples. The experiments were carried out with continuous drive friction welding set-up. Friction welding experiments with different frictional times and constant friction pressure as well as rotational speed were carried out. The strength of the welds was determined by tensile strength tests. Hardness variation of the joint was also obtained. The results were compared with those of previous studies. The results of applied tests and observations showed that the properties of microstructure change and that the interface temperature increases with friction time. The best tensile strength of the joint was observed for the specimen welded at 1700 rpm rotation speed and a friction time of 3 s.
Zur Wiederverwendung von Durchläufern im Treppenstufenversuch
Authors: Müller Christian , Hinkelmann Karsten , Wächter Michael , Masendorf Rainer , Esderts Alfons
Published: December 2013

Kurzfassung

Viele Bauteile sind während ihrer Nutzungsdauer schwingenden Beanspruchungen ausgesetzt. Ermüdungsfestigkeitsnachweise sollen den sicheren Betrieb schwingend beanspruchter Bauteile garantieren. Ein wichtiger Kennwert zur Führung von Ermüdungsfestigkeitsnachweisen ist die Bauteildauerfestigkeit. Ihre experimentelle Bestimmung ist zeit- und kostenintensiv. Häufig stehen nur wenige Prüfkörper zur Verfügung, sodass eine statistische Auswertung unmöglich wird. Um dennoch Aussagen über die Bauteildauerfestigkeit abzuleiten, können so genannte Durchläufer wiederholt eingesetzt werden. Im vorliegenden Beitrag werden die Auswirkungen des Wiedereinsatzes von Durchläufern diskutiert. Hierbei werden keine werkstoffmechanischen Betrachtungen zur Vorschädigung oder zur Trainierwirkung angestellt. Vielmehr werden Simulationsmethoden vorgestellt, mit denen sich maximale Fehler bei der 50%-Dauerfestigkeitsschätzung ableiten lassen. Durch nachträgliche Berücksichtigung des maximalen Fehlers kann ein Bemessungskennwert auch mit wenigen Proben abgeleitet werden.
Approximation of Damage Accumulation in Fibre Reinforced Polymers
Authors: Zachariev Georgi
Published: December 2013

A unified approach for the derivation of the known equations describing damage accumulation as a result of loading of fibre-reinforced polymers is proposed. The investigated materials are short glass fibre-reinforced polyoxymethylene (GF/POM) and long glass fibre-reinforced epoxyresin (GFRP). The damage structures themselves consist of the accumulation of additional internal surfaces within the entire material volume as measured by small angle scattering X-ray refractometry. On the basis of the concept for a loading percentage under creep, damage accumulations applying short-term and long-term loading are compared. It is shown that for the investigated materials our approximations by a double exponent function are more effective than the approximations according to Weibull. It is also shown how the coefficients of the double exponent cumulative function can be found.
Wear Behaviour of Heat Treated Hot Work Tool Steels under Dry Sliding Conditions
Authors: Polat Şeyda , Atapek Ş. Hakan , Türedi Enbiya , Aktaş Gülşah
Published: December 2013

In this study, commercial hot work tool steels were selected and their wear behaviour under dry sliding condition was investigated after heat treatment applications. In the first stage of the study, solution annealing, quenching, and finally tempering treatments were applied to the experimental steels. All samples were examined by light microscopy after metallographic preparations. In the second stage, hardness values (HRC) of the steels were determined to evaluate the surface resistance to wear. Finally, wear tests were carried out using ‘ball-on-disc’ type tribometer under dry sliding condition and all worn surfaces were characterized using both light and scanning electron microscopy. It is concluded that (i) the steels had typical tempered martensite matrices, (ii) alloy content affected the final microstructure and a finer matrix was obtained due to vanadium addition, (iii) hardness levels directly affected the coefficient of wear of steels, and (iv) worn surfaces exhibited abrasive and adhesive wear tracks.
Predictive Modelling of Ball Burnishing Process Using Regression Analysis and Neural Network
Authors: Ugur Esme , Kulekci Mustafa Kemal , Ozgun Sueda , Kazancoglu Yigit
Published: December 2013

The present paper focuses on two techniques, namely regression and neural network techniques, for predicting surface roughness in ball burnishing process. Values of surface roughness predicted by the two techniques were compared with experimental values. Also, the effects of the main burnishing parameters on surface roughness have been determined. Surface roughness (Ra) was taken as response (output) variable and burnishing force, number of passes, feed rate, and burnishing speed were taken as input parameters. Relationship between the surface roughness and burnishing parameters was found out for direct measurement of the surface roughness. Results showed the application of the regression and neural network models to accurately predict the surface roughness.
Einsatz der Bayes'schen Statistik in der Zuverlässigkeitsbestimmung von zerstörungsfreien Prüfsystemen
Authors: Kanzler Daniel , Müller Christina , Ewert Uwe , Pitkänen Jorma
Published: December 2013

Die Fehlerauffindwahrscheinlichkeit oder “Probability of Detection” ist zu einer wichtigen Qualitätskennzahl von zerstörungsfreien Prüfsystemen geworden. Die Einschätzung von nur künstlichen Fehlern ist jedoch als Bewertungsgrundlage meist nicht ausreichend. Die später verwendeten Prüfobjekte mit den real vorkommenden Fehlern sind die zu betrachtende Basis, für die der Endanwender eine gültige Qualitätseinschätzung der angewandten zerstörungsfreien Prüfung fordert. Jedoch ist bei dem Fall, dass die Datenmenge gering ist, auch die Aussage der POD beschränkt. Es muss daher eine Zwischenlösung gefunden werden, in der die Informationen von beiden Prüfungen kombiniert werden. Die Mathematik ermöglicht mit der Bayes'schen Statistik, diese Informationen miteinander zu kombinieren und somit beide Informationen in die Bewertung einfließen zu lassen. Dabei spielt jedoch der Zusammenhang zwischen Signal und Fehlerausprägung eine wichtige Rolle. Praktisch angewendet und erprobt wird diese Vorgehensweise für die Bewertung der zerstörungsfreien Prüfungen der Firma POSIVA, die sich mit dem Bau eines Endlagers für hochradioaktiven Abfall in Finnland beschäftigt.
Paradigm Shift in the Holistic Evaluation of the Reliability of NDE Systems
Authors: Mueller Christina , Bertovic Marija , Pavlovic Mato , Kanzler Daniel , Ewert Uwe , Pitkänen Jorma , Ronneteg Ulf
Published: December 2013

The aim of this publication is to provide an overview of new methodologies for evaluating the reliability of NDE systems in accordance with the specific requirements of industrial applications. After a review of the substantive issues of the previous decades, the go forward guidance is concluded. For high safety demands a quantitative POD (Probability of Detection) created from hit/miss experiments or signal response analysis and ROC (Receiver Operating Characteristics) are typically created. The modular reliability model distinguishes between the pure physical-technical influence, industrial application factors, and human factors. It helps to learn which factors can be determined by modeling and by open or blind trials. A new paradigm is offered to consider the POD or reliability of the system as a function of the configuration of input variables and is used for optimization rather than for a final judgement. New approaches are considered dealing with real defects in a realistic environment, affordable but precisely like the Bayesian approach or model assisted methods. Among the influencing parameters, human factors are of high importance. A systematic psychological approach helps to find out where the bottlenecks are and shows possibilities for improvement.
Coating Distribution Depending on Surface Microgeometry
Authors: Runje Biserka , Marković Marija , Stojanović Ivan , Jakovljević Suzana , Alar Željko
Published: December 2013

This paper investigates the effects of surface microgeometry on coating thickness, both theoretically and experimentally. In the theoretical part of the paper, surface roughness parameters are analyzed and basic definitions and general requirements on coating quality defined. The experimental part of the paper gives a calculation for the coating quantity required in order to fill “dead volume” depending on surface roughness. Coating distribution is analyzed using scanning electronic microscopy (SEM). The paper also evaluates quality of a measuring system using magnetic method for measuring coating thickness.
Stress Analyses of Pump Gears Produced by Powder Metallurgy
Authors: Cetinel Hakan , Yilmaz Burak
Published: December 2013

In this study, trochoidal type (gerotor) hydraulic pump gears were produced by powder metallurgy (P/M) technique. Several gears with different mechanical properties have been obtained by changing process variables. The tooth contact stresses were calculated analytically under particular operation conditions of the hydraulic pump. The 3D models have been obtained from real gears by using Capability Maturity Model (CMM, 3D scanning) operation and SOLIDWORKS software. Stress analyses were conducted on these 3D models by using ANSYS WORKBENCH software. It was found that the density increases by the increase of sintering duration and mechanical properties were positively affected by the increase of density. Maximum deformation takes place in the region of the outer gear where failure generally occurs with the minimum cross-section area.
Synchrotron-Radiographie und -Tomographie einer PEM-Brennstoffzelle
Authors: Markötter Henning , Arlt Tobias , Banhart John , Manke Ingo , Riesemeier Heinrich , Krüger Philipp , Haußmann Jan , Klages Merle , Scholta Joachim
Published: December 2013

Die dreidimensionalen Wasserverteilungen und -transportwege in den Gasdiffusionslagen (GDL) einer Polymer-Elektrolyt-Membran(PEM)-Brennstoffzelle werden bei verschiedenen Betriebsbedingungen analysiert. Die Methode der quasi In-situ-Röntgen-Tomographie wird für eine dreidimensionale Visualisierung der Wasserverteilung sowie der Struktur der GDL genutzt. Basierend auf Ergebnissen dynamischer radiographischer Messungen werden Wassertransportwege aufgefunden und anschließend mithilfe der Tomographie im Detail untersucht. Die Kombination dieser 2D- und 3D-Techniken erlaubt eine Identifizierung der Transportwege durch die GDL. zwei Mechanismen werden auf der Kathodenseite beobachtet: zum einen Wasser, das aus der GDL in den Kanal transportiert wird, und zum anderen Wasser, das in die GDL zurückgedrückt wird.
The Effect of Aging and Sliding Speed on Wear Behaviour of Cu-Cr-Zr Alloy
Authors: Özyürek Dursun , Ciftci Ibrahim , Tuncay Tansel
Published: December 2013

In this study, the sliding wear behaviour of non-aged and aged Cu-Cr-Zr alloy specimens were investigated. The specimens were aged for 2 h at the temperatures of 450 °C and 475 °C. Prior to the wear tests, microstructural examinations and hardness measurements were performed on all Cu-Cr-Zr alloy specimens. The wear tests were performed on a pin-on disk type wear apparatus at the sliding speeds of 0.5 ms−1, 1.0 ms−1 and 1.5 ms−1 as well as under 40 N applied load. After the wear tests, the worn surfaces of all samples were analyzed by SEM and energy dispersive X-ray spectroscopy (EDS). The experimental results indicated that aging heat treatment led to increase in the hardness values of Cu-Cr-Zr alloys and the highest wear loss was observed for non-aged specimens. With increasing sliding speed, the wear loss increased to a maximum value beyond which it decreased.
An Automatic Detecting Apparatus for Antarctic Sea Ice Cracks
Authors: Xiaomin Chang , Yinke Dou , Zhuo Dun , Jianmin Qin
Published: December 2013

The change in width of sea ice cracks seriously affects the transportation during human's activities in the Antarctic sea, but there are few automatic technologies for accurate monitoring of such cracks. To solve this problem, an automatic detecting apparatus for sea ice cracks was designed, and its feasibility and monitoring principles were studied. Furthermore, a practical methodology was developed and such apparatus was applied to the testing of the Antarctic sea ice cracks. The testing results showed that the data were reliable and stable for the analysis of icing behaviour.
Acoustic Emission Evaluation of Fatigue Life Prediction for a Carbon Steel Specimen using a Statistical-Based Approach
Authors: Mohammad Mazian , Abdullah Shahrum , Jamaluddin Nordin , Innayatullah Othman
Published: December 2013

This study was carried out to investigate the relationship between the strain and acoustic emission (AE) signals to ascertain the applicability of AE in predicting the fatigue life of metallic specimens. This paper is an extension research of previous work that has been published before. Previous paper presents the ability of AE to predict the fatigue life using statistical parameters such as root mean square (r.m.s) and kurtosis. The same approach also has been carried out in this recent paper but this time, the common parameters that can be directly extracted from the AE data acquisition system were used. To achieve the objective, the strain and AE signals were measured using a strain gauge and a AE piezoelectric transducer on SAE 1045 steel specimens. These measurements were conducted during the cyclic test at constant loadings of 570 MPa, 610 MPa, and 650 MPa. For data collection, AE parameters, i. e., count rate, hits, and duration, were extracted from specific software and were then correlated to fatigue lives calculated using the strain data. Fatigue life values were calculated using strain-life models. The correlation between the experimental and predicted values of fatigue life was then established by the so-called coefficient of correlation which is within 97.2 % and 98.5 % for the Coffin-Manson model and between 92.7 % and 94.3 % for the Smith-Watson-Topper model, respectively. As for the Morrow model, the coefficient of correlation was tabulated at approximately between 71.9 % and 73.6 %. Good correlation values expressed that the AE technique is applicable for predicting the fatigue life of metallic specimens.
Bemessung laserstrahlgeschweißter Überlappverbindungen aus Magnesium und Aluminium unter mehrachsiger Beanspruchung∗
Authors: Exel Nora , Wiebesiek Jens , Sonsino Cetin Morris , Hanselka Holger
Published: December 2013

Der vorliegende Beitrag vergleicht die beiden Leichtmetallknetlegierungen AlMg3,5Mn und MgAl3Zn1 auf Basis von Schwingfestigkeitsergebnissen laserstrahlgeschweißter Überlappverbindungen. Die Versuche wurden sowohl unter reiner Axial- und Torsionsbelastung als auch kombiniert mit konstanten und veränderlichen Hauptspannungsrichtungen durchgeführt. Die Ergebnisse werden mit dem Referenzradiuskonzept rref = 0,05 mm bewertet und mit zulässigen Beanspruchbarkeiten aus einem Regelwerk verglichen. Des Weiteren werden zwei spannungsbasierte Methoden zur Bewertung der Beanspruchungsmehrachsigkeit vorgestellt.
Verhalten von lasergeschmolzenen Bauteilen aus der Titan-Aluminium-Legierung TiAl6V4 unter zyklischer Beanspruchung∗
Authors: Riemer Andre , Leuders S. , Richard Hans A. , Tröster T.
Published: December 2013

Selektives Laserschmelzen (SLM) gehört zu den additiven Fertigungsverfahren (AM) und gewinnt zunehmend an Bedeutung. Im Fokus dieses Beitrags stehen Ergebnisse der Untersuchungen an zyklisch belasteten SLM-Bauteilen aus der Titan-Aluminium-Legierung TiAl6V4. Hierzu wurden Experimente zur Bestimmung der Schwingfestigkeit sowie zur Charakterisierung des bruchmechanischen Materialverhaltens durchgeführt. Die Ergebnisse verdeutlichen, dass z. B. die Dauerfestigkeit und der Schwellenwert des Materials gegen Ermüdungsrissausbreitung beim SLM-Verfahren niedriger sind als die des Grundmaterials. In dieser Arbeit wird jedoch gezeigt, wie durch gezielte Wärmebehandlungsmethoden die Materialkenndaten der SLM-Bauteile verbessert werden können.