bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Heat Treatment and Thermochemical Processes on the Properties of the Steel X 38 CrMoV 5 3
Authors: Kisasoz Alptekin , Karaaslan Ahmet
Published: December 2013

In this study, the effects of heat treatments and cooling rates on the properties of the steel X 38 CrMoV 5 3 were investigated. Heat treatments and cooling rates during the steel fabrication processes are critical parameters for the properties of tool steels, since the phases and the lattice structures change respectively. In the experiments, four different heat treatment processes and also, nitriding and carbonitriding processes were applied to specimens made from the investigated steel. For such experiments, two different austenitising temperatures with three different cooling rates were selected and the effects of the process para­meters on the mechanical strength were investigated. Microstructure evaluations were carried out by image analysis and by using a scanning electron microscope. To determine and compare the mechanical properties, Vickers hardness tests and three-point bending tests were applied.
Development of Vibration Isolation Mounts of a Vehicle Using Static and Dynamic Analysis
Authors: Korkmaz İbrahim
Published: December 2013

In automotive industry, rubber mounts are widely used to cushion the loads and isolate vibration in passenger vehicle compartments. In this study an engine rubber mount and strut bushing are analysed. The static and dynamic characteristics of the rubber specimen as well as the viscoelastic and hyperelastic properties are obtained by static and dynamic testing. The material properties coefficients in the finite element analysis have been implemented accordingly to the test data. The dynamic and static characteristics of the strut bushing and the engine mount are predicted with finite element analysis. The solutions show satisfactory agreement between predicted and experimental results. According to the authors, this work on the development of vibration isolation mounts using physical tests and simulations for verification of the final product, and providing the static and dynamic design factors represents pioneer work in open literature.
Mechanical Properties of A6063/SiC Composites Produced Using the Lost Foam Casting Process
Authors: Güler Kerem Altug , Kisasoz Alptekin , Yuksel Caglar , Karaaslan Ahmet
Published: December 2013

Aluminum matrix composites have a long history and they are still in the focus of interest. Molten metal processes are basic and the most common techniques of these kind of materials. Using lost foam casting process (LFCP) for aluminum matrix composite production is a new approach. LFCP is a special casting method, and it has flexibilities and advantages under complexity, material, and production aspects. It was considered that, reinforcement materials (SiC particles, etc) can be added to molten aluminum within the expanded polystyrene (EPS) foam patterns. Successful experiments were performed; SiC particles and molten aluminum were mixed with lost foam casting (LFC) technique. And this current study was carried out to determine the mechanical properties of A6063/SiC cast composites. The microstructures of the castings were investigated with optical and scanning electron microscopy (SEM). Archimedes density test, tensile, impact, and Brinell hardness tests were performed, and the results are consistent to those generally observed for metal matrix composites. Hardness, especially yield strength of matrix was increased with reinforcement addition, however ductility and toughness were decreased. Also, the respective production technique has a significant effect on the mechanical properties.
Statistical Optimization of Gold Recovery from Difficult Leachable Sulphide Minerals Using Bacteria
Authors: Ahmed H. A. M. , El-Midany A. A.
Published: December 2013

Some of refractory gold ores represent one of the difficult processable ores due to fine dissemination and interlocking of the gold grains with the associated sulphide minerals. This makes it impossible to recover precious metals from sulphide matrices by direct cyanide leaching even at high consumption of cyanide solution. Research to solve this problem is numerous. Application of bacteria shows that, some types of bacteria have great affect on sulphides bio-oxidation and consequently facilitate the leaching process. In this paper, leaching of Saudi gold ore, from Alhura area, containing sulphides before cyanidation is studied to recover gold from such ores applying bacteria. The process is investigated using stirred reactor bio-leaching rather than heap bio-leaching. Using statistical analysis the main affecting variables under studied conditions werde identified. The design results indicated that the dose of bacteria, retention time and nutrition K2SO4 are the most significant parameters. The higher the bacterial dose and the bacterial nutrition, the better is the concentrate grade. Results show that the method is technically effective in gold recovery. A gold concentrate containing >100 g/t gold was obtained at optimum conditions, from an ore containing < 2 g/t gold i.e., 10 ml bacterial dose, 6 days retention time, and 6.5 kg/t K2SO4 as bacteria nutrition.
Characterization of Eutectic Sn-Cu Solder Alloy Properties Improved by Additions of Ni, Co and In
Authors: Piyavatin Pitinan , Lothongkum Gobboon , Lohwongwatana Boonrat
Published: December 2013

Recently, the cost factor of raw materials has emerged continuous improvement of tin-copper solder alloys. This work aims to improve the microstructural and mechanical properties of the eutectic tin-copper solder alloys by addition of nickel, cobalt and indium. The temperature profile of reflow soldering in surface-mount assembly was simulated to produce realistic joint microstructures. Key properties for electronic soldering were characterized, i.e. melting behaviour, solidification beha-viour, wettability, electrical resistivity, microstructures and mechanical properties. The results showed that addition of Ni, Co and In can effectively improve the mechanical properties of Sn-0.7Cu solder alloy i.e. microhardness and shear strength by providing preferred interfacial morphology and formation of intermetallic compound precipitates. The new solder alloys also showed reduced liquidus and solidus temperatures whereas no significant degradation of other key properties were seen.
Abgestimmte Testumgebung aus dem Baukasten für Betriebsfestigkeitsversuche an Cabrioverdecken*
Authors: Mawick Gregor , Gries Christian , Schmiedt Stefan , Kuttner Thomas
Published: December 2013

Kurzfassung

Ein flexibler Shakerbock für Cabrioverdecke mit einstellbaren Massen und Steifigkeiten ist entwickelt und für den Einsatz auf einer 4-Stempelanlage erprobt worden. Damit wird der Versuchsaufbau bestmöglich in der Geometrie, den Eigenfrequenzen und Eigenformen dem zum Zeitpunkt des Versuches nicht verfügbaren Gesamtfahrzeug angepasst. Durch den modularen Aufbau kann der flexible Shakerbock an verschiedene Fahrzeuge angepasst werden und ermöglicht den Aufbau aller üblichen Dachsysteme.
Exploiting the Property Profile of High Strength Steels by Damage Mechanics Approaches*
Authors: Münstermann Sebastian , Sharaf Mohamed , Lian Junhe , Golisch Georg
Published: December 2013

Although high strength low alloy steels offer the potential for lightweight design, their application is often rather limited due to existing design rules. A further development of these standards requires precise prediction of realistic limit states. The damage model of Bai and Wierzbicki has been extended in order to improve the description of the ductile failure behaviour of steels, especially when crack initiation in dynamic loading is to be simulated. Application examples of the extended model are given in order to show that it can be used for limit state analysis. An outlook presents the application of the model to derive improved safety factors for probabilistic safety concepts.
Microstructure and Mechanical Properties of Dual Matrix Aluminium-Fly Ash Composites Processed via Cryomilling, Cold Compaction and Hot Extrusion
Authors: Mindivan Harun , Vatansever Recep , Sabri Kayali Eyup
Published: December 2013

AA6061/Al alloy chips of different size and fly ash particles have been recycled using the solid state process. The effect of chip size and fly ash content on the microstructure, mechanical and wear properties of the recycled AA6061/Al two phase composites were investigated. Microstructural characterization revealed a uniform distribution of fly ash particles in recycled composites with fine chips and a good interface between fly ash particulates and AA6061/Al two phase matrixes. According to mechanical and wear results, the incorporation of fly ash particles in the AA6061/Al two phase matrix caused reasonable increase in hardness, compressive strength, and wear resistance. On the recycled composites fine chips, the destructive action of the steel ball was very limited compared to that of the Al 2O3 ball.
Innovative Prüfmethodik zur Ermittlung der thermomechanischen Ermüdung an Zylinderköpfen
Authors: Bischoff Tobias , Rödling Steffen , Stauder Bernhard
Published: December 2013

Kurzfassung

Im Auslegungsprozess von Zylinderköpfen spielt die Bewertung der thermomechanischen Ermüdung eine wesentliche Rolle. Der IABG- Zylinderkopfprüfstand basiert auf einer innovativen Methode, die eine Beurteilung und Optimierung von Zylinderköpfen hinsichtlich thermomechanischer Ermüdung bereits in einem sehr frühen Entwicklungsstadium erlaubt. Durch die im Vergleich zu konventionellen Prüfmethoden deutlich kürzeren Versuchszeiten bietet der Prüfstand die Möglichkeit, die Entwicklungszeiten neuer Zylinderkopfkonzepte bei gleichzeitiger Reduzierung der Versuchskosten erheblich zu verkürzen. Der offene Aufbau des Prüfstandes ermöglicht zudem erstmals eine In-situ-Detektion des Anrisses sowie eine Verfolgung des Rissfortschrittes im Brennraumdach. Der vorliegende Artikel stellt das Prüfkonzept und die Ergebnisse eines Variantenvergleichs von konstruktiv identischen Zylinderköpfen mit unterschiedlichen Aluminium-Gusslegierungen vor.
How to Deal with Very High Cycle Fatigue (VHCF) Effects in Practical Applications?*
Authors: Bacher-Hoechst Manfred , Issler Stephan
Published: December 2013

Fatigue designing of high-stressed engine components is a key factor for reliable power train systems in automotive industry. In this context load assumptions are very important since this is attended with a pre-designing of important machine elements. Load analyses are usually performed by using experimental methods since the accuracy of load simulations are often not precise enough. An example for VHCF problems occurs in modern high pressure pumps for gasoline direct injection systems, which have load spectra with a large amount of cycles up to 109 including a very powerful shape of the spectra. At the same time it is necessary to consider the properties of fuels in service since they might affect the fatigue strength significantly. For example, ethanol-based gasoline fuels are used in a lot of countries worldwide and especially their additives may lead to significant corrosion fatigue effects. In addition, it is well known that material inclusions play an important role for the VHCF behaviour especially for high-strength steels. This paper deals with possibilities to avoid VHCF problems of components in service to maintain reliable systems.
Drilling Template Used to Produce Cellular EPS Patterns for the Lost Foam Casting Process
Authors: Guler Kerem Altug , Uster Ates , Cigdem Mustafa
Published: December 2013

Cellular metals differ from the other materials by a lower density which is their characteristic property. Besides, they show unusual physical, mechanical, thermal, acoustic and electrical properties. Even though they have lots of pores compared to solid materials they can show a unique combination of several properties that cannot be obtained in a conventional material at the same time. There are several kinds of production methods for cellular materials. Nowadays, lots of researches have been carried out with respect to new production methods. The lost foam process, which bases on evaporating the polystyrene foam model, reduces the process steps of investment casting and can be an alternative method to many production methods. In this study, open cell samples were produced with two different aluminium alloys by using the lost foam casting technique. A413 as a casting alloy and A6063 as a wrought alloy were selected for casting experiments. After production of these two aluminium alloys, the decrease in weight, compression strengths, deformation ratios were determined and compared to each other.
Upgrading of an Ultrasonic Fatigue Testing Machine by Means of Early Stage Damage Detection
Authors: Kovacs Stephan , Stille Sebastian , Ernstes Daniel , Beck Tilmann
Published: December 2013

This contribution highlights the implementation of different methods for early stage damage detection in very high cycle fatigue (VHCF) experiments by means of an ultrasonic testing machine developed by BOKU in Vienna. Basically three different methods are used for in-situ evaluation of degradation: the analysis of (i) the harmonics, (ii) the development of the resonance frequency, (iii) the damping behaviour of the specimen at the end of each testing pulse. The fatigue experiments and measurements of the relevant parameters are controlled using the software LabView. We demonstrate the sensivity of the different methods on two specimen variants: (i) round samples of the chromium steel X10CrNiMoV12-2-2 and (ii) flat samples of the aluminium alloy Al-2024.
Assessment of Fracture Behaviour under Impact Loading with Simultaneous Recording of Acoustic Emission
Authors: Schoßig Marcus , Bierögel Christian , Grellmann Wolfgang
Published: December 2013

The objective of this paper is the assessment of the toughness of glass fiber-reinforced polypropylene and polybutene-1 by means of fracture mechanics concepts to describe the resistance against unstable crack initiation for these materials. In addition, the acoustic emissions during the instrumented Charpy impact test were recorded, which allows the characterization of the damage kinetics. For this purpose, the recorded transient signals of the acoustic sensor were analyzed with the wavelet transform. Thus, it was possible to describe the onset of the damage in the time domain, as well as the load Fs and the corresponding deflection fs. In dependence on the bonding conditions of the materials, the damage onset was detected for polypropylene before and for polybutene-1 at the transition from elastic to elastic-plastic behaviour.
A Crack Identification Approach for Beam-Like Structures under Moving Vehicle using Particle Swarm Optimization
Authors: Gökdağ Hakan
Published: December 2013

A crack identification method for beam type structures under moving vehicle is proposed. The basic of the method is to formulate damage detection as an inverse problem, and solve for damage locations and extents. With respect to this, an objective function is defined based on the difference of damaged beam dynamic response and the response calculated by the mathematical model of the beam. The optimization problem is solved by the particle swarm optimization (PSO) with linearly increasing inertia weight to obtain crack locations and their depths. By the numerical simulations, it was observed that cracks with depth ratio of 0.1 can be identified with reasonable error by the present method in spite of noise interference of 3 %.
Low Frequencies for Cardboard Quality Assurance
Authors: Ebersold Zoran , Mitrović Nebojša , Đukić Slobodan , Peulić Aleksandar , Obradović Dragiša
Published: December 2013

During the ultrasound defectoscopy the ultrasound absorption factor inside the material is raised to the fourth power of frequency. In conjunction with the previously stated, the attenuation of the sound signal which is caused by the reflections of the sound inside the sample, the application of high frequency ultrasound in porous and hollow materials is very limited or even impossible. The frequencies are the reason for this, because they are in the range of just several megahertz, which are currently the main trend in the ultrasound examination. This paper presents a principle of this new method, including the experimental results from its application on the typical represent of product packaging material. Also, it is shown that the expressed absorption of ultrasound waves from porous and hollow structures can be avoided by applying the method with such low frequencies.
Effects of Surface Treatment on Corrosion Resistance of 316 Stainless Steel Implants in Tyrode Solution
Authors: Ahmadian Zeinab , Danaee Iman , Golozar Mohammad Ali
Published: December 2013

The effect of different surface preparation methods such as mechanical, chemical, and electrochemical surface preparation as well as ultrasonic cleaning on the formation, stability, and deterioration of surface films formed on austenitic 316 stainless steel was investigated in Tyrode's solution. The methods of cyclic polarization, AC impedance measurements and surface techniques were used. A hysteresis loop in a cyclic polarization curve was obtained that indicates a delay in re-passivation of an existing pit when the potential is scanned cathodically. Nyquist diagrams consist of two strongly overlapped capacitive semicircles which are assigned to charge transfer and passive film resistance. Electrolytic polishing improves corrosion resistance by increasing the value of the corrosion potential and breakdown potential of the passive layer as well as the pit initiation potential. After chemical passivation and acid cleaning, no perfect passivation region was observed. Change in surface fractal is in good agreement with the result obtained from height roughness factor of AFM.
Direct Decomposition of N2O Emitted from Nitric Acid Plant Tail Gases Using Noble Metal Supported Mordenite-Zeolite Catalysts∗
Authors: Kwon Byung-Chan , Cho Sung-Su , Seo Minhye , Lee Sungkyu , Song Jinho
Published: December 2013

Mordenite based catalysts for direct decomposition of N2O have been successfully prepared and their direct decomposition performance characterized at the operating temperature of 300–400 °C commonly encountered in the nitric acid plants tail gases. The catalyst was prepared in 2 steps: 1. Precursor wet ion exchange, 2. Precursor impregnation. In addition to the previous contribution, it is shown here that the bimetallic Rh-, Pd-, Ir-Fe-MOR catalysts thus prepared exhibited an excellent N2O decomposition performance: total conversion efficiency of Rh-Fe-MOR catalyst has been achieved at 400 °C and between 7500 h−1 and 10 000 h−1 space velocity.
A Numerical Study on the Mechanical Properties and the Processing Behaviour of Composite High Strength Steels
Authors: Münstermann Sebastian , Vajragupta Napat , Weisgerber Bernadette , Kern Andreas
Published: December 2013

The demand for lightweight construction in mechanical and civil engineering has strongly promoted the development of high strength steels with excellent damage tolerance. Nowadays, the requirements from mechanical and civil engineering are even more challenging, as gradients in mechanical properties are demanded increasingly often for components that are utilized close to the limit state of load bearing capacity. A metallurgical solution to this demand is given by composite rolling processes. In this process components with different chemical compositions were jointed, which develop after heat treatment special properties. These are actually evaluated in order to verify that structural steels with the desired gradients in mechanical properties can be processed. A numerical study was performed aiming to numerically predict strength and toughness properties, as well as the processing behaviour using Finite Element (FE) simulations with damage mechanics approaches. For determination of mechanical properties, simulations of tensile specimen, SENB sample, and a mobile crane have been carried out for different configurations of composite rolled materials out of high strength structural steels. As a parameter study, both the geometrical and the metallurgical configurations of the composite rolled steels were modified. Thickness of each steel layer and materials configuration have been varied. Like this, a numerical procedure to define optimum tailored configurations of composite high strength steels could be established.
The Effects of Process Parameters on the Recycling Efficiency of Used Aluminium Beverage Cans (UBCs)
Authors: Ozer Gokhan , Yuksel Caglar , Comert Zekeriya Yasar , Guler Kerem Altug
Published: December 2013

In this paper, the effects of process parameters on the recycling efficiency of used aluminium beverage cans (UBCs) were investigated. In the experimental studies, separated internal workshop scraps and used aluminium beverage cans are used as charge materials for melting process. Aluminium beverage cans are thin walled parts and produced with high Mg content aluminium alloys. Thus its high oxidation affinity reduces recycling efficiency of the cans. Used can pieces were pressed to obtain briquettes for charging. To increase the recycling efficiency and to optimize the process conditions, preheating, pre-charging, and fluxing were applied. The optimum parameters that provide the maximum recycling efficiency were determined. Chemical analyses and tensile tests were carried out with the resulting as cast samples.
Processing of Finely disseminated Saudi Iron Ores
Authors: Ahmed Hussin A. M. , Mahran Gamal M. A.
Published: December 2013

Iron ores located in Alswaween area, Saudi Arabia are of finely disseminated nature. They require ultrafine grinding for a considerable degree of liberation. In this paper, different upgrading techniques are described for their processing. The applied upgrading techniques included selective flocculation and column flotation as recent efficient technologies in fines upgrading. Each technique was investigated and optimized separately. Results showed that neither selective flocculation nor column flotation can be successfully used alone to produce high quality iron concentrate, especially when using iron ore of size fraction 0.075 mm (100 %). The best quality concentrate was found to have 55 % Fe and 57 % Fe when applying selective flocculation and column flotation, respectively, at their optimum operating conditions. Meanwhile, the previously obtained results can be significantly improved when grinding the ore < 45 µm first and applying selective flocculation as cleaning step for the concentrate obtained from the column flotation. Thus, it is possible to obtain a concentrate having an iron content of 63.55 % Fe with 52.3 % yield which means an iron recovery in the concentrate of about 80 %.
The Effect of Helical Pin Profiles on the Friction Stir Welding Performance of Aluminium Alloy AA6082
Authors: Kasman Şefika
Published: December 2013

In this study, one of the solid state welding methods, friction stir welding, was studied with the AA6082 aluminum alloy. Two types of pins with a special geometry were used to investigate the effect of pins profile, tool rotational speed, and welding speed on the mechanical properties of welded joints. The pin profile was associated with weld joint properties such as tensile strength, elongation, bending strength, bending force, hardness distributions and temperature. Results have shown that the friction surface area of the pin has a significant role on the mechanical behaviour of the joint. The results of tensile tests associated with the pin profile indicate that the helical two-flute pin has a high tensile strength and elongation compared to the helical four-flute pin. Discrepancies in the tensile strength of the welded samples of the two pin profiles have been found between 37–55 % at the same welding conditions. Despite the relatively poor static properties, the helical four-flute pin has better bending properties. Higher bending strength and force (260.634 MPa and 347.513 daN) were obtained at test conditions of 2000 rpm and 100 mm/min. Bending without any defect on the joint was achieved at 2000 rpm and 200 mm/min. The effect of welding parameters on the hardness profile was not clear, and it has been observed that, in comparison, the helical two-flute pin did not create a remarkable difference with regard to hardness.
Characterization of Sigma Phase in Duplex Stainless Steels Using Non-destructive Ultrasonic Techniques
Authors: Rodriguez Cristina , Biezma Victoria , Fernandez Monica
Published: December 2013

Duplex stainless steels have wide applications in industry due to their high mechanical strength, excellent toughness, and high corrosion resistance regarding to other types of steels. However, these steels are susceptible to form brittle phases during heat treatment associated to manufacture or welding processes, in particular the negative effect of sigma-phase into ferrite-austenitic microstructure has to be pointed out. In this work, a study is carried out about the use of ultrasonic nondestructive technique to establish a relationship between sigma phase signal percentages in 2507 duplex stainless steel and more relevant features of the collected ultrasonic signal in an equation. Thus, a novel method is obtained to perform the inspection of these materials in-situ in order to avoid the loss of mechanical resistance and to increase the susceptibility to localized corrosion in service.
Investigating the Wear Behaviour of FeCrC/B4C Powder Alloys Coating Produced by Plasma Transferred Arc Weld Surfacing Using the Taguchi Method
Authors: Gür Ali Kaya
Published: December 2013

In this study, the optimization of the abrasive wear behaviour of a medium carbon steel surface with a FeCrC/B4C powder coating applied by using the plasma arc weld surfacing process is examined. Optimization of the process parameters represents the key step in the Taguchi method to achieve high quality without increasing cost. The Taguchi method uses orthogonal arrays to maximize the effect of controllable parameters and to minimize the effect of uncontrollable process para­meters. The abrasive wear behaviour of the surface of a medium carbon steel substrate material coated with FeCrC and with 15 % or 25 % B4C was tested at loads of 10 N, 20 N, and 30 N and at distances of 10 m, 20 m, and 30 m. The lowest wear loss, representing the most important criterion in determining the wear behaviour, was optimized with the so-called lowest-the best control characteristics of the Taguchi method and the results were analyzed by graphical methods.
Mathematical Modeling of Diameter and Circularity Deviation in Wire Electrical Discharge Machining of a Hot Work Tool Steel
Authors: Esme Ugur , Kulekci M. Kemal , Akkurt Adnan , Seker Ulvi , Ozkul Iskender
Published: December 2013

The suitable selection of manufacturing process and conditions are very important in manufacturing processes to obtain good surface quality and dimensional precision. Thus, it is required to know properties relating to material, surface quality and dimensional precision by means of mathematical models which allow some predictions taking into account operation conditions such as feed rate, current and pulse on time, etc. Wire electrical discharge machining (WEDM) represents a modification of electro discharge machining (EDM) and is widely used for a long time for cutting punches and dies, shaped pockets as well as other machine parts on conductive work materials. Present work is focused on the regression modeling predicting diameter and circularity deviation of a hot work tool steel. Mathematical relationships between circularity and diameter deviation as well as WEDM cutting parameters (feed rate, current and pulse on time) have been investigated. Results show that, regression analysis can be successfully applied for this mathematical model.
Bewertung der Schwingfestigkeit von Schweißnahtenden mit dem Kerbspannungskonzept und bruchmechanischen Methoden∗
Authors: Waterkotte Ralf , Baumgartner Jörg , Ai Qingfeng
Published: December 2013

In dieser Arbeit wurde eine Bewertungsmethodik untersucht, mit der das komplexe Versagensverhalten von geschweißten Verbindungen beschrieben werden kann. Die Bewertung erfolgt dabei auf Basis eines Zwei-Phasen-Modells, in dem die Berechnung der Anrisslebensdauer und der Rissfortschrittslebensdauer getrennt durchgeführt wird. Die Anrisslebensdauer wird basierend auf dem Kerbspannungskonzept mit Spannungsmittelung nach Neuber sowie der Theorie des kritischen Abstandes nach Taylor berechnet. Die Makro-Rissfortschrittslebensdauer wird ausgehend von FE-Analysen unter Verwendung von bruchmechanischen Kennwerten bestimmt. Die untersuchten Methoden lieferten bei der Abschätzung der Anrisslebensdauer gute Ergebnisse. Beim Vergleich der berechneten Spannungsintensitätsfaktoren zeigen sich Unterschiede in Abhängigkeit von den verwendeten Berechnungsansätzen. Es zeigte sich, dass die eingesetzten Methoden für den industriellen Einsatz weiter verbessert werden sollten.
Evaluation of the Cold Formability of Multiphase Steels by Damage Mechanics Approaches∗
Authors: Münstermann Sebastian , Lian Junhe , Vajragupta Napat
Published: December 2013

During sheet metal forming of multiphase steel for automotive application, more and more often failure happens prior to necking, so that the forming limit diagram is not an appropriate measure for cold formability anymore. Alternatively, the modified Bai Wierzbicki (MBW) model can be applied since it belongs to the group of coupled continuum damage mechanics models. It considers all invariants of the stress tensor both in the yield potential and in the crack initiation criterion. In this publication the model is successfully applied to characterize the cold formability of a dual phase steel of the grade DP600. Additionally, a procedure is described which delivers the parameters of the macroscopic MBW model's damage initiation criterion by simulations of representative volume elements. In these simulations, the underlying physical mechanisms of crack initiation and propagation are quantitatively described.
Plättchen-Biegeversuch nach VDA 238-100∗
Authors: Neuhaus Ralf , Borsutzki Michael
Published: December 2013

Kurzfassung

Zur Ermittlung der Versagensanfälligkeit von metallischen Werkstoffen bei Biege-Umformprozessen sowie von Kennwerten zur numerischen Simulation des Verformungsverhaltens dient der sogenannte Plättchen-Biegeversuch. Als Kennwert dient der beim Anriss der Probe herrschende Biegewinkel, der in der Regel aus dem aufgenommenen Stempelweg und der Geometrie der Prüfanordnung rechnerisch ermittelt wird. Bei ThyssenKrupp Steel Europe ist hierzu ein neuartiges optisches Winkelmesssystem im Einsatz, das zeitlich synchronisiert mit dem Kraft-Weg-Verlauf der Maschine den Biegewinkel kontinuierlich und direkt an der Probe bestimmt. Durch den Vergleich berechneter und gemessener Biegewinkelverläufe wird gezeigt, dass insbesondere bei Biegewinkeln über 90° deutliche Unterschiede in den Prüfergebnissen auftreten.
Prüftechnik in der Kupferhalbzeugindustrie∗
Authors: Theobald Stefan , Hofmann Uwe , Riedle Joachim
Published: December 2013

Kurzfassung

Die technologischen Eigenschaften von Halbzeugen aus Kupfer und Kupferlegierungen hängen neben der chemischen Zusammensetzung auch von den Parametern der thermo-mechanischen Herstellprozesse ab. Mess-, Prüf- und Regeltechnik dient dabei neben der Überprüfung der Qualität vor allem der Prozessoptimierung. Nach einem Überblick der üblicherweise zum Einsatz kommenden Prüftechnik werden vor allem anwendungsspezifische Prüfverfahren erläutert. Exemplarisch werden die Kontaktwiderstandsmessung an Steckverbinderwerkstoffen sowie Geräte zur Bestimmung der Biegewechselfestigkeit von Drähten in Seewasseratmosphäre vorgestellt. Zur Bestimmung des Umformvermögens der Werkstoffe ist die Messung der Fließkurve (auch temperatur- und geschwindigkeitsabhängig) von Bedeutung. Ein dafür selbst entwickelter Torsionsplastometer-Messplatz wird mit Anwendungsbeispielen beschrieben.
Application of Genetic Algorithms (GA) for the Optimization of Riveted Joints
Authors: Baskal Tamer , Nursoy Mustafa , Esme Ugur , Kulekci Mustafa Kemal
Published: December 2013

Genetic algorithms have an effective search technique in a predefined research space based on natural selection theory. They use the same combination of selection, recombination, and mutation to evolve a solution to a problem. In this study, it has been demonstrated how to determine the optimal diameter, sheet thickness, and sheet width in riveted joints by means of genetic algorithms (GA). In this study the optimization of objective function for the variables in predetermined limit ranges was applied. Since the algorithms developed by this way are based on a principle to find out the best within a range like genetic process, it is becoming possible to predict the most suitable values for riveted junction dimensions in the defined limit range. The algorithms were restrained considering rivet diameter, thickness and width of the sheet, shear strength, tensile strength, and tear hazard of the sheet.
Röntgenrückstreuradiografie – Eindringen statt Durchdringen, aber Bilder mit Schatten
Authors: Wrobel Norma , Kolkoori Sanjeevareddy , Osterloh Kurt
Published: December 2013

Kurzfassung

Der große praktische Vorteil der Rückstreuradiografie allgemein ist, dass kein Bilddetektor am Objekt auf der der Strahlenquelle gegenüberliegenden Seite aufgestellt werden muss. Dieses ist immer dann gegeben, wenn sich das Untersuchungsobjekt in oder an einer Wand befindet oder es so groß ist, dass eine Durchstrahlung aufgrund der zu durchdringenden Schichtdicken nicht infrage kommt. Von der üblichen Methode, das Objekt mit einem wandernden ausgeblendeten Einzelstrahl („Bleistiftstrahl“) abzutasten und die gesamte rückgestreute Strahlung großflächig zu registrieren, unterscheidet sich das hier verwendete Verfahren grundsätzlich. Das Objekt wird voll von einem (unkollimierten) Kegelstrahl angestrahlt. Das Bild wird mit einer Kamera aus absorbierendem Material (Wolfram, Blei) aufgenommen, die einen Matrixdetektor als Bildempfänger enthält. Die „Optik“ besteht aus einer besonders geformten Schlitzblende, die nach einem erweiterten Lochkameraprinzip arbeitet, das auch dickere Blendenmaterialschichten zulässt. Die voneinander unabhängige Positionierung von Kamera und Strahlenquellen erlaubt unterschiedliche Einstrahlgeometrien, die verschiedene Ergebnisbilder liefern. So erscheint ein komplexer Gegenstand vor einer rückstreuenden Wand völlig anders, als wenn er frei im Raum steht. Röntgenrückstreubilder müssen deshalb abhängig von ihrer „Ausleuchtung“ mit der Röntgenstrahlung und näheren Umgebung interpretiert werden.
Surface Roughness Changes on β-Titanium Orthodontic Wires after Corrosion in Various Artificial Saliva Solutions
Authors: Kucukyildirim Bedri Onur , Eker Aysegul Akdogan
Published: December 2013

β-Titanium orthodontic wires are exposed to three different artificial corrosive environments, modified Fusayama, modified Fusayama with 0.1 % NaF addition, and modified Fusayama with 1.7 % H3PO4 addition, which are similar to the oral cavity conditions. Corrosion behaviours of wires are observed by using weight loss method and scanning electron microscope observations. Afterwards, surface roughness of wires is investigated in details. Consequently, it is determined that corrosion rate of β-titanium wires exposed to the modified Fusayama solutions with H3PO4 addition is higher because of the acidity of this saliva. Furthermore, maximum increase in surface roughness and skewness are observed in the same environment. Hydrogen embrittlement of titanium is also an important factor for the corrosion of wires.
Experience with MTR fuel at the HOR reactor
Authors: Verkooijen A. H. M. , de Vries J. W.
Published: December 2013

In the last three years 3 events were observed in which the release rate of fission products from the fuel plates into the pool water increased significantly. Although intervention levels laid down in the permit and safety analysis were never reached, the ALARA principle was the incentive to analyse the situation and take appropriate actions.
A clean nuclear blasting technique for the excavation of a new isthmus canal in Central America
Authors: Seifritz W.
Published: December 2013

Based an new insights into the physics of thermonuclear burn waves a novel nuclear blasting technique is proposed for the excavation of a new Isthmus canal in Central America. It allows the spatial decoupling of a small fission trigger from the main DD fusion charge in the geometrical form of a cylinder with an extremely high length-to-diameter ratio in such a way that absolutely no fission products can escape into the atmosphere. A clean nuclear blasting technique could thus be made available.
Practical applications of the exemption principle in radiation protection
Authors: Wrixon A. D.
Published: December 2013

The concept of exemption has been widely used in radiological protection. It is part of the regulator's arsenal for applying legislative requirements in a graded fashion, to avoid the expenditure of effort on situations where the return in terms of improvement in protection would otherwise be trivial. Nevertheless, it still remains a controversial matter. It is not so much the dosimetric criteria for exemption that cause debate; it is more the way in which the concept is used; the scenarios employed to calculate derived activity concentrations, and its relationship to the somewhat analogous concept of exclusion. A particular problem has been the full integration into the legislative system of protection of exposures to radiation from sources of natural origin and the degree to which exemption is a relevant concept for dealing with such situations. The purpose of this paper is to attempt to provide some clarity on the two concepts and their practical implementation with a view to encouraging international harmonization and avoiding further unnecessary debate.
Determination of the replacement cooling tower capability at the ETRR-2 research reactor
Authors: El-Morshdy S. El-Din
Published: December 2013

The ETRR-2 replacement cooling tower capability has been evaluated by the thermal acceptance test performed in June 2003. All instruments used were calibrated prior to the test. The measured data are collected at regular intervals in accordance with the acceptance test code for water cooling towers of the Cooling Tower Institute recommendations. Both the characteristic curve and the performance curve methods were used to evaluate the tower capability. The test results yield a tower capability of about 105% and so the tower is thermally accepted.
Brennstabauslegung und Brennstabmodellierung – Teil 1
Authors: von Collani Elart , Baur Karl
Published: December 2013

Kurzfassung

Die Brennstabauslegung ist ein wesentlicher Aspekt für den sicheren und wirtschaftlichen Betrieb von Kernkraftwerken. Die langjährige Betriebserfahrung zeigt, dass der Sicherheitsstandard der Brennstäbe sehr hoch ist und die international anerkannten Schutzziele eingehalten werden. Zwischenzeitlich haben wirtschaftliche Überlegungen zu einer Erhöhung der mittleren Brennelementabbrände von 35 MWd/kgSM auf heute etwa 55 MWd/kgSM geführt. Neben der besseren Wirtschaftlichkeit wird dadurch im Sinne des Umweltschutzes der Kernbrennstoffbedarf reduziert und die Anzahl der zu entsorgenden Brennelemente verringert. Allerdings bedeutet jede weitere Abbranderhöhung auch zusätzliche Anforderungen an die Brennstäbe, insbesondere an die Hüllrohrmaterialien, wodurch sich erneut die Notwendigkeit des Nachweises der Brennstabintegrität ergibt. Im Vordergrund dieser Nachweise steht seit geraumer Zeit der Übergang von deterministischen zu statistischen Auslegungsmethoden, mit dem Ziel durch Berücksichtigung der vorhandenen Variabilität der Vorgänge im Reaktorkern zu einer wirklichkeitsnäheren Beschreibung zu gelangen. Dadurch können zuverlässigere und genauere Vorhersagen über das Verhalten der Brennstäbe gemacht werden, die die Grundlage für eine effektive Brennstabauslegung und den Nachweis der Brennstabintegrität bilden. Dieser Beitrag beschäftigt sich mit der Frage, inwiefern die bestehenden Modelle aus stochastischer Sicht die Variabilität berücksichtigen und zeigt, dass ein stochastisches Modell neue Chancen für zuverlässige Nachweise bietet. Das vorgeschlagene stochastische Modell behebt gewisse Schwächen der bisherigen Vorgehensweisen, setzt alle vorhandenen Erkenntnisse direkt um und macht die stets vorhandene Ignoranz sichtbar. Zusätzlich werden im Beitrag einige, insbesondere in der Bundesrepublik Deutschland aufgeworfene Fragen, kritisch betrachtet. Der Beitrag besteht aus zwei Teilen. Im ersten Teil werden die benötigten Grundlagen gelegt, während im zweiten Teil auf die mehr technischen Fragen eingegangen wird.
Decommissioning strategy selection
Authors: Warnecke E.
Published: December 2013

At the end of their useful life nuclear facilities have to be decommissioned. The strategy selection on how to decommission a facility is a highly important decision at the very beginning of decommissioning planning. Basically, a facility may be subject to (a) immediate dismantling; (b) deferred dismantling after a period of “safe enclosure” or (c) entombment where a facility is turned into a near surface disposal facility. The first two strategies are normally applied. The third one may be accepted in countries without significant nuclear activities and hence without disposal facilities for radioactive waste. A large number of factors has to be taken into account when a decision on the decommissioning strategy is being made. Many of the factors cannot be quantified. They may be qualitative or subject to public opinion which may change with time. At present, a trend can be observed towards immediate dismantling of nuclear facilities, mainly because it is associated with less uncertainty, less local impact, a better public acceptance, and the availability of operational expertise and know how. A detailed evaluation of the various factors relevant to strategy selection and a few examples showing the situation regarding decommissioning strategy in a number of selected countries are presented in the following article.
Decommissioning technologies, including recent developments and special features of the dismantling of nuclear research and prototype facilities
Authors: Bach Fr.-W. , Pfeifer W. , Versemann R. , Wilk P. , Valencia L. , Eisenmann B. , Hammer G.
Published: December 2013

A variety of technologies is available for the decontamination and dismantling of nuclear facilities. All over the world, these technologies as well as conditioning processes of decommissioning waste are further developed. So far, they have been mainly applied to the dismantling of research and prototype facilities. Dismantling of reactors of higher power has started with the nuclear power plants of Greifswald and Würgassen among others. The present paper shall present the state of the art of decontamination and dismantling techniques as well as of post-treatment processes of radioactive decommissioning waste. From the technical point of view, the most complex step is the remote dismantling of activated and highly contaminated components. The prototype facilities of Forschungszentrum Karlsruhe, which are currently being dismantled, cover all types of plants. Their status of dismantling and the experience gained from using decommissioning technologies that are also suited for power facilities shall be illustrated. Further developments and adaptations of individual techniques, e. g. thermal and mechanical cutting methods, as well as of the complete systems technology, including carrier system, manipulator system, and tools, are reasonable and indispensable for managing the variety of dismantling tasks and, not least, for reducing their operation times and costs of use.
The decommissioning of light water reactors – experience
Authors: Schiffer K. , Bacmeister G. U. , Adler J.
Published: December 2013

More than ten nuclear power plants in Germany have been decommissioned or are under dismantling. Objectives, strategies, preparatory work, licensing, technical dismantling and safety considerations are explained from the utility point of view, using the Stade (KKS) decommissioning as an example. Challenges with respect to characterisation, logistics and economy are discussed.
Decommissioning and dismantling of the Siemens fuel cycle facilities
Authors: Kindleben G. , Baumann R. , Faber P.
Published: December 2013

Four Siemens-owned German fuel cycle facilities are being decommissioned at the Hanau and Karlstein sites. Decommissioning of one of these facilities has already been completed. The facilities comprise three fuel fabrication plants and a facility for post-irradiation investigations of fuel assemblies. In each case the actual decommissioning phase was preceded by clean-out. Extensive preparatory investigations and planning, including licensing procedures, had been necessary. In some cases new measuring techniques and systems had to be developed and waste processing systems erected. In addition to providing a general survey of the different conditions and procedures involved, the MOX facility is used in this paper as an example for presenting these activities in greater detail. This includes the concept of immediate conditioning of radwaste for maintenance-free long-term interim storage (storage for several decades until a repository is available) in such a way as to also meet the requirements for shipment and final disposal without any need for further actions. A number of lessons have been learned and recommendations derived from the many years of decommissioning work at the four facilities.
Neutronic conceptual design of the ETRR-2 cold neutron source
Authors: Khalil M. Y. , Shaat M. K. , Abdelfattah A. Y.
Published: December 2013

The conceptual neutronic design of the cold neutron source (CNS) for the Egyptian second research reactor (ETRR-2) was carried out using the MCNP code. A parametric analysis was also performed to choose the type and geometry of the moderator and the required CNS dimensions to maximize the cold neutron production. The moderator cell is a spherical annulus containing liquid hydrogen. The cold neutron gain and brightness are calculated together with the nuclear heat load of the CNS. The effects of void fraction in the moderator cell and the ortho:para ratios on cold neutron gain were calculated.
Simulation of the neutronic-thermal hydraulic stability behaviour of boiling water reactors
Authors: Gorzel A. H. , Henschel M. W. , Mrosk E. M. , Scheerer W. E.
Published: December 2013

Neutronic-thermal hydraulic oscillations are a well known phenomenon in the operation of boiling water reactors. Despite the progresses that have been made concerning their simulation, the computational determination of the stability threshold in the power-flow map still suffers from inaccuracies. In this work, the decay ratio of neutronic-thermal hydraulic oscillations and hence the stability threshold was calculated with the SIMULATE-3K code developed by Studsvik Scandpower. It is known from experience that there is a higher probability for a less stable reactor operation in the case of one or more pumps tripped while the remaining pumps run at minimum speed. For the analysis of this state, the characteristics of the pump system were modelled carefully. It is shown that the stability behaviour is determined by the axial and radial power profile due to control rod manoeuvring and fuel burn-up and by the number of pumps running. Furthermore the calculations reveal the impacts of the insertion of shallow rods and of the control-rod group insertion on the decay ratio. A comparison of the calculations with experimental results of stability measurements shows that by a thorough analysis and proper modelling of the plant characteristics the decay ratios can be calculated with the SIMULATE-3K code.