Faser‐ und drahtverstärkte Kupferlegierungen als Wärmesenke für Fusionsreaktoren

Fibre and wire reinforced copper alloys as heat sinks for fusion reactors The CuCr1Zr alloy is used in existing experimental fusion reactors and planned to be used as a heat sink in ITER because of his mechanical properties and thermal conductivity (at 20 °C 310–330 W/m/K). Because of aging this dispersion‐hardened alloy is limited in use to temperatures below 450 °C. A possibility to increase the service temperature (the aim is 550 °C) is to reinforce the alloy with SiC‐fibres or W‐wires. With the aid of SiC (SCS‐6) fibres and W‐wires (diameter ～150 μm for both) coated with the CuCr1Zr‐alloy, Cu‐MMCs are produced and their properties (tensile strength, thermal conductivity, fibre/matrix interface properties) are determined. Processing (Hot Isostatic Pressing) causes the alloy to age, making an additional heat treatment necessary in order to optimize the properties. The tensile strength of the different Cu‐MMCs was determined as a function of the volume content of the reinforcements. Tensile strength rises with increasing volume fraction of fibres (or wires) and reaches e.g. 1000 MPa for a SiC‐fibre volume fraction of 24 % or a W‐wire volume fraction of 27 %. Measurements of the thermal conductivity, performed by laser flash, show that the thermal conductivity is reduced with increasing fibre volume fraction (e.g. 200 W/m/K for a fibre volume fraction of 30 %). The W‐wire reinforced CuCr1Zr alloy has been selected because of its better thermal conductivity and interfacial properties to estimate the potential of this Cu‐MMC in a first design study of heat sinks on the basis of different divertor construction types.     

Analysis of a rotation‐free 4‐node shell element

In this paper, a shell element for small and large deformations is presented based on the extension of the methodology to derive triangular shell element without rotational degrees of freedom (so‐called rotation‐free). As in our original triangular S3 element, the curvatures are computed resorting to the surrounding elements. However, the extension to a quadrilateral element requires internal curvatures in order to avoid singular bending stiffness. The quadrilateral area co‐ordinates interpolation is used to establish the required expressions between the rigid‐body modes of normal nodal translations and the normal through thickness bending strains at mid‐side. In order to propose an attractive low‐cost shell element, the one‐point quadrature is achieved at the centre for the membrane strains, which are superposed to the bending strains in the centred co‐rotational local frame. The membrane hourglass control is obtained by the perturbation stabilization procedure. Free, simply supported and clamped edges are considered without introducing virtual nodes or elements. Several numerical examples with regular and irregular meshes are performed to show the convergence, accuracy and the reasonable little sensitivity to geometric distortion. Based on an updated Lagrangian formulation and Newton iterations, the large displacements of the pinched hemispherical shell show the effectiveness of the proposed simplified element (S4). Finally, the deep drawing of a square box including large plastic strains with contact and friction completes the ability of the rotation‐free quadrilateral element for sheet‐metal‐forming simulations. Copyright © 2005 John Wiley & Sons, Ltd.     

Klebflächenvorbehandlung von Aluminiumoberflächen mit SIP‐Haftvermittler

Surface pretreatment for adhesive bonding of aluminium with adhesive mediator SIP The present contribution describes the influence of different surface pretreatments including adhesive mediator SIP for adhesive bonding of aluminium alloy AlMg4,5Mn0,4. The investigations were performed using two cold hardening two‐components epoxy‐adhesives, one hot hardening one‐component epoxy‐adhesive and one cold hardening two‐components polyurethane‐adhesive. The adhesive bonds with epoxy‐adhesives show after three‐step pretreatment degreasing + corundblasting + SIP coating the highest adhesive strength values whereas adhesive bonds with polyurethane‐adhesive showed a decrease of bond strength as compared with the delivering surface condition.     

Entwicklung einer niedrigschmelzenden Legierung und deren Applikation zum Korrosionsschutz hochfester Stähle

Development of low‐temperature galvanizing and its application for corrosion protection of high‐strength steels Apart from reliability and quality, vehicle safety and cost efficiency are the decisive criteria for automobile manufacturers. Corrosion protection plays a decisive role because it increases the service life. The ultra‐high‐strength steels are materials which exhibit high lightweight potential as well as a very good energy absorption capacity because of their mechanical properties. In connection with the possibility of hot forming, they are predestined for the fabrication of complicated, load‐compatible shapes in the crash‐relevant frame and body construction. The application of these steel qualities has been carried out in structural parts which are protected from corrosion by a hot‐dip coat of FeAl7 – the so‐called Usibor. However, at the moment there is no ready‐for‐production solution for later corrosion protection of already hot‐formed parts. Therefore, a corrosion protection system on the basis of conventional low‐temperature galvanizing processes has been developed and utilized. First, the softening behavior of the highly‐resistant 22MnB5 substrate was analyzed. Afterwards, a galvanizing system was developed and applied. The corrosion protection coatings were characterized with regard to their structure and corrosion protection potential. As a result, a significant improvement of the corrosion behaviour has occurred.     

Eigenschaften langzeitgealterter,artgleicher Schweißnähte der Ni‐Basislegierung alloy 602 CA

Properties of long‐time aged matching joints of Ni‐base alloy 602 CA The paper presents results about the influence of a 2‐year exposure in the production process of ammonia synthesis on the microstructure and the mechano‐technological properties of matching TIG‐ and e‐manual welds of the high‐temperature resistant Ni‐based alloy 602 CA (NiCr25FeAlY, Material‐No. 2.4633 / UNS N 06025). These results show, that Ni‐base alloy 602 CA possesses a very good resistance against metal dusting. Furthermore typical metallurgical characteristics of the welding process of this extremely hot‐crack sensitive alloy are presented and recommendations for a hot‐crack safe manufacturing of components made of this alloy are given.     

Auslegung keramischer Präzisionsgleitlager mit textiler Verstärkungskomponente

Design of ceramic high‐accuracy bearings containing textile fabrics In order to determine the thermo‐elastic behaviour of slide bearings with a bearing sleeve of textile structured ceramic matrix composites (CMC), a new method for computation of the material properties of the composite material was implemented. Therefore a small cut‐out from the regular fabric structure was discretised with the finite element method (FEM). The woven rowings were thereby regarded as unidirectional long‐fiber‐reinforced composites, for which assured calculation methods are available. Additionally pores can be considered in the model. The computed material properties were examined and used as input data for a further FEM‐Model describing the slide bearing with CMC sleeve. By means of this model the thermo‐elastic behaviour of the bearing is determined. The main problem using CMCs as bearing surface (bearing sleeve) in a steel box are the different thermal coefficients of expansion. During the warm up phase the outline of the bearing surface changes. Applying constructional changes based on the simulation the dissipation loss of the bearing sinks substantially and the bearing is prevented from galling.     

Ultrathin and Switchable Nanoporous Catalytic Membranes of Polystyrene‐b‐poly‐4‐Vinyl Pyridine Block Copolymer Spherical Micelles

An easy fabrication of close‐packed and block copolymer micelles‐based ultrathin membranes for water purification, separation, catalytic, and dye degradation applications is reported. Nanoporous membranes based on the self‐assembly of 2‐(4′‐hydroxybenzeneazo) benzoic acid (HABA)‐polystyrene‐b‐poly(4‐vinylpyridine) (PS‐b‐P4VP) diblock copolymers supramolecular complexes are prepared by simple spin coating on pore‐filled polyethylene terephthalate (PET) track‐etched membranes. The prepared membranes are characterized by scanning electron microscopy, atomic force microscopy, transmission electron microscopy, and water permeation studies. The separation performance is studied by lysozyme protein rejection. The prepared membranes are also used to in situ synthesize gold nanoparticles in the corona of PS‐b‐P4VP spheres for catalytic activity towards the reduction of p‐nitrophenol and degradation of congo red dye in flow through operation mode in a stirred cell membrane reactor. More than 95% reduction for p‐nitrophenol and >98% degradation of Congo red at a sufficiently high flux indicates its suitability for catalytic transformation and environmental remediation applications.     

A 4‐node assumed strain quasi‐conforming shell element with 6 degrees of freedom

Quasi‐conforming formulations of 4‐node stress‐resultant shell elements are presented. The element formulations use interrelated displacement–rotation interpolations. The formulation also includes drilling degrees of freedom, which improves membrane behavior and allows the modeling of stiffened plates and shells. The proposed treatment for bending provides very good results in the 4‐node shell element. The stiffness matrices for the present elements are explicitly expressed and the stresses are taken accurately at the nodal points. Compared to elements using Gauss integration, where the stresses are most accurate at the integration points, the extrapolation procedure needed for post‐processing is eliminated in the present shell element. A lot of numerical tests were carried out for the validation of the present 4‐node shell element and the results are in good agreement with references. Copyright © 2003 John Wiley & Sons, Ltd.     

Experimentelle und analytische Untersuchung des out‐of‐plane‐Verhaltens von unbewehrten Mauerwerkswänden unter Erdbebenbelastung

Experimental and analytical investigation of the seismic out‐of‐plane behavior of unreinforced masonry walls In addition to the vertical and horizontal load‐bearing in‐plane, masonry must also withstand out‐of‐plane loads that occur in earthquake scenarios. The out‐of‐plane behavior of unreinforced masonry walls depends on a variety of parameters and is very complex due to the strong non‐linearity. Current design methods in German codes and various international codes have not been explicitly developed for out‐of‐plane behavior and contain considerable conservatism. In the present work, shaking‐table experiments with heat‐insulating masonry walls have been conducted to investigate the out‐of‐plane behavior of vertical spanning unreinforced masonry walls. As shown in previous numerical investigations, important parameters are neglected in existing design and analysis models and the out‐of‐plane capacity is underestimated significantly. In the conducted experiments the results of these numerical investigations are verified. Furthermore, the development of an analytical design model to determine the force‐displacement relationship and the out‐of‐plane load‐bearing capacity considering all significant parameters is presented.     

Wechsellast‐Prüfung von Hüftgelenk‐Pfannen mit keramischen Einsätzen

Fatigue Test of Hip‐Joint Cups with Ceramic Inserts A safe design of hip‐joint components for the long‐term use in humans requires an evaluation of the fatigue lifetime under the in‐vivo loading conditions. For compound cups with ceramic inserts no standardized or commonly agreed procedure exists up to now. Therefore, a test is presented here which is practised by the authors and which possibly could be the basis for a standard. Because of the expensive testing procedure and the large number of possible cup‐insert combinations a failure test with only few samples was chosen.     

Elektrisch leitfähige kohlenstofffaserverstärkte Kunststoffe (CFK) mit freiliegender Funktionsschicht

Efficient lightweight requires intelligent materials that meet versatile functions. One approach is to extend the range of properties of carbon‐fiber‐reinforced plastics (CFRP) by plating the fiber component. Functions such as thermal and electrical conductivity, contactability, solderability, and adhesion promoting are integrated on this road. When processing the metallized carbon fibers to carbon‐fiber‐reinforced plastics the functional layer is covered by the matrix polymer. Thus, it is no longer accessible for further proceeding. In this work, different strategies for the production of carbon‐fiber‐reinforced plastics with accessible functional layers are analyzed. Thereby, selective uncovering of the functional layer as well as proceeding the carbon‐fiber‐reinforced plastics and metal‐layers without damages are important criteria. An evaluation of the processes was carried out using microstructural investigations and adhesive tensile testing. Correlations between electrical conductivity measurements, wetting and joining experiments, surface machining and solderability can be derived.     

Validierung der Beständigkeit von ZrO2‐Minikugeln gegenüber Heißdampfsterilisation

Validation of the Resistance of ZrO₂‐Mini Balls against Hot Vapour Sterilisation Mini‐balls are used in bearings of dental drills. As the bearings as well as the drills are hot vapour sterilised, the bearings are operated under non‐lubricated conditions. In the present study, Raman scattering experiments show that hot vapour sterilisations of Y₂O₃ stabilised ZrO₂‐Mini‐balls lead to a phase transition from tetragonal to monoclinic ZrO₂. This phase transition finally causes the failure of ZrO₂‐Mini‐balls under the tribological conditions typical for dental drills. If, however, the ZrO₂‐Mini‐balls are stabilised using CeO₂, such hot vapour sterilisation induced phase transitions could not be observed. Subsequent tribological experiments prove that CeO₂ stabilised ZrO₂‐Mini‐balls, produced in a Sol‐Gel process, are resistant to slip‐rolling conditions, if large pores can be avoided.     

A technique of object‐adaptive vertex‐based shape coding for MPEG‐4 videos

The MPEG‐4 visual standard is the first international standard that allows the transmission of arbitrarily shaped video objects and provides technologies to view, access, and manipulate objects rather than pixels. It addresses the encoding of video objects by shape coding, motion estimation, and texture coding for interactivity, high compression, and scalability. Current binary shape‐coding techniques can be classified into two categories: bitmap based and contour based. O'Connell (1997) proposed an object‐adaptive vertex‐based shape‐coding method to improve the efficiency of shape coding. This method encodes the relative locations of a video object's vertices by adapting the representation to the dynamic range of the relative locations and by exploiting an octant‐based representation for each relative location. We propose an extension of O'Connell's method. Two relative locations of a video object's vertices are grouped and the x pairs and y pairs of the locations are encoded, respectively. Simulation results demonstrate that our method outperforms O'Connell's method. © 2001 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 11, 277–282, 2000     

Verschleißreduzierung an Matrizen für das Präzisionsschmieden von Zahnrädern durch Mehrlagenhartstoffbeschichtung (TiN‐TiCN‐TiC)

Wear reduction on dies for precision forging of gear wheels by means of multi‐layer coating (TiN‐TiCN‐TiC) Due to high thermal, mechanical and tribological loads the tool life quantity of hot forging dies compared to other manufacturing processes is relatively low. Depending on the number of forged parts the mentioned loads lead to different failure causes of the dies. In this connection wear is the main failure cause of hot forging dies. Especially in the precision forging process of gear wheels with its exacting tolerances the tool life quantity is low, which leads to often interruptions of the production process. Because wear concentrates on the near‐surface die areas, these problems can be reduced by increasing the wear resistance of these areas by the Duplex PACVD‐Method, which means nitriding and multi‐layer coating (TiN‐TiCN‐TiC).     

Laserstrahlschweißen von Mikrodrähten aus Nickel‐Titan‐Formgedächtnislegierungen und austenitischem Stahl

Laserwelding of microwires made of nickel‐titanium shape memory alloys and austenitic steel The special properties of nickel‐titanium shape memory alloys are currently used in micro engineering and medical technology. In order to integrate nickel‐titanium components into existing parts and modules, they often need to be joined to other materials. For this reason, the present contribution deals with the laser welding of thin pseudoelastic nickel‐titanium wires (100 μm) with a neodymium‐doped Yttrium Aluminium Garnet laser. Based on extensive parameter studies, joints without defects were produced. This study deals with the microstructure in the fusion and heat‐affected zones, the performance of the joints in static tensile tests and their functional fatigue. It can be shown that nickel‐titanium/nickel‐titanium joints reach about 75 % of the ultimate tensile strength of pure nickel‐titanium wires. In case of welding nickel‐titanium to steel no interlayer was used. The dissimilar nickel‐titanium/steel joints provide a bonding strength in the fusion and heat‐affected zones higher than the plateau stress level. Nickel‐titanium/steel joints of thin wires, as a new aspect, enable the possibility to benefit from the pseudoelastic properties of the nickel‐titanium component.     

Modell zur Analyse des knöchernen Anwachsverhaltens auf bioaktiv beschichteten Implantatoberflächen

Model to analyse the bone on‐growth on bioactive coated implant surfaces Especially on the field of bone regeneration, transient and permanent implants are an important method of therapy in the Orthopaedic Surgery. In this context, bioactive surfaces on metallic implants provide an improved contact to the surrounding bone. The goal of our study was to establish an in‐vitro test system to evaluate the on‐growth of bone‐derived cells on different surface coatings. Therefore, we invented a special kind of clamps made of commercially‐pure (c‐p) titanium and blasted with hydroxyapatite particles followed by electrochemically coating with calcium phosphate (BONIT®‐HA, BONIT®). Definite pieces of human cancellous bone were attached to these clamps, inserted onto tissue culture plates and cultivated in DMEM for ten days. Finally, the contact area between human cancellous bone and the implant surface was analyzed and the spreading of osteoblast‐like cells evaluated by scanning electron microscopy (SEM). A well‐spread morphology of bone cells was observed on the implant surfaces coated with calcium phosphate (CaP). In comparison the clamps without CaP coatings showed only a marginal growth of bone cells on the clamp surface. The presented newly in‐vitro test setup using titanium clamps coated with bioactive layers attached to human cancellous bone represents a well‐functioning model for qualitative evaluation of bone on‐growth.     

A Flexible Ionic Liquid Gelled PVA‐Li2SO4 Polymer Electrolyte for Semi‐Solid‐State Supercapacitors

A novel high‐performance flexible gel polymer electrolyte (FGPE) for supercapacitors is prepared by a freeze‐drying method. In the presence of 1‐butyl‐3‐methylimidazolium chloride (BMIMCl) ionic liquid, Li₂SO₄ can easily be added into poly(vinyl alcohol) (PVA) aqueous solution over a large concentration range. The resultant FGPE demonstrates considerably high ionic conductivity (37 mS cm⁻¹) and a high fracture strain at 100% elongation at the optimal weight ratio of PVA:BMIMCl:Li₂SO₄ = 1:3:2.2. The supercapacitor fabricated with the resultant FGPE and activated carbon electrodes shows an electrode‐specific capacitance of 136 F g⁻¹ with a stable operating voltage of 1.5 V, a maximum energy density of 10.6 Wh kg⁻¹, and a power density of 3400 W kg⁻¹. Double supercapacitors in series can efficiently drive a light emitting diode (LED) bulb for over 5 min and the retention of the specific capacitance reaches 90% even after 3000 charge–discharge cycles. The ionic conductivity and charge–discharge behaviors of the resultant FGPE are not affected by bending up to 180°. The flexible supercapacitor device shows only a small capacitance loss of 18% after 1000 cycles of 135° bending.     

Einfluss der Netztopologie der künstlich neuronalen Netze auf das Ergebnis der Abschätzung zyklischer Kennwerte

Several estimation methods have been developed to estimate the cyclic material parameters out of the static material properties. Most of these methods are based on empirical equations. Increasing numbers of input‐ and influencing parameters lead to an rising effort for determining these equations and the accuracy decreases. For this reason new suitable methods are sought to estimate the cyclic material behaviour. A very promising approach is the application of the artificial neural networks, which can derive self‐depended a relationship between in‐ and output parameters. Static parameters such as yield strength, tensile strength …? etc., which can rapidly be determined used as input parameters. The output parameters are the cyclic material parameters of the strain‐life curve and stress‐strain curve according to the Manson‐Coffin‐Basquin‐ and Ramberg‐Osgood curve. Many different artificial neural networks with different structures and complexity can be applied. In this paper the influence of the topology of an artificial neural network on the estimation accuracy will be investigated. Based on the results of a reference artificial neural network it will be shown, that more complex topologies in the network do not lead inevitably to better estimations.     

Standsicherheitsberechnungen an bestehenden Gewichtsstützwänden

Stability calculations for existing gravity retaining walls Many parts of older waterway structures consist of gravity retaining walls. The construction is characterized by cross‐sections, several meters thick, consisting of unreinforced concrete or masonry. Besides earth pressure and impacts caused by operation, frequently high water loads have to be borne. Static recalculations, applying the existing standards using the normal simplified approach, almost always lead to theoretical deficits regarding structural stability. These, in turn, result in expensive structural reinforcement measures or even replacement constructions. Deficits result especially from neglecting the multidimensional stress and strain states and the very conservative approach of the inner water pressure in form of crack and pore water pressure in accordance with the applicable standards. This article uses the example of numerical analyses performed in a two‐dimensional FE‐model of a retaining wall, taking into account the interaction between crack formation and distribution of the inner water pressure for each variation considered, to show that calculatory safety margins are clearly detectable. It is recommended to extend the scope of the analysis to a wider range of models, in order to confirm the gained findings as well as to upgrade on this basis the engineering model in common practice.     

Gesteinbearbeitung mittels dünner Kreissägeblätter

Treatment of stones by means of thin circular saw blades Circular saws and/or abrasive machining of granite or marble blocks takes place in the industry by block circular saws with 40 to 80 circular saw blades on a shaft. Each of these tools with a tool diameter of approx. 1,000 mm produces a kerf of approx. 6.5 mm. By use of a case‐hardened quality for the master sheets the master sheet thickness and the kerf can be reduced approx. 1 mm. Related to the block which can be separated substantial material savings result in the case of sawing of high‐quality raw materials. Because the used tools are to finish very difficulty with conventional, mechanical technologies, the laser technology became develops for stretching and arranging the disk‐shaped tools. The Laser application is a requirement for the automizableness these work procedures.