Werkstoffanwendungen von Stahl im Zeitstandbereich – technische Herausforderung mit Langzeitwirkung

Application of creep resistant steels – A technical challenge with long‐term importance The development activities for creep resistant steels based on joint research programs in Germany and Europe have resulted in significant progress for materials application in the power plant area. Steels of 9‐11 %CrMoV are already used in operating power plants and will be applied in the planned next generation plants. In particular, the results of these newly developed steels show that a reliable long‐term extrapolation of the creep‐rupture strength is only possible on the basis of real long‐term tests and microstructural understanding. Three material examples of current relevance, P92, T122, HR1200, are given to show the reasons for and the effect of the reduction of an extrapolated 100,000h creep rupture strength. Finally, the paper deals with an example of software development for residual life estimation of CrMoV materials, developed with the results of more than 20 years of research work.     

Klebtechnik – multifunktionales Fügen für den nachhaltigen Werkstoffeinsatz im 21. Jahrhundert

Adhesive bonding technology – multifunctional joining for the sustainable use of materials in the 21^st century Adhesive bonding meets the key requirements for the sustainable joining technology of the 21^st Century: different materials can be assembled with integrated additional functions in a weight saving manner. The review paper outlines introductory the origin and the commercial relevance of adhesive bonding technology. Methods of surface treatment and the meaning of adhesion and cohesion are discussed. The classification of the adhesives occurs according to the setting mechanism. The right selection is explained. The comparison with other joining technologies is important for the assessment of adhesive bonding. The geometric design of the joint is based on construction guidelines: one should avoid stress peaks and maximize the glue area. Simple notes for the strength calculation make dimensioning easier. Materials testing in adhesive bonding engineering is described. The thick‐adherend tensile shear test is suited for the in situ determination of mechanical characteristics. Applications of adhesive bonding in aviation and aerospace and transportation are presented. Besides these traditional industries, new markets in sectors like electronics and medicine are opened up. Due to high strength and deformability, chemically curing products solve demanding tasks in adhesive bonding and sealing technology.     

Gründerzeitliche Mauerwerksbauten unter Erdbebeneinwirkung – Tragverhalten im Widerspruch zur aktuell angewandten Nachbemessung

Historic masonry buildings under earthquakes – Load‐bearing behaviour in contradiction to the currently applied methods of analysis The stability of historic masonry buildings must be guaranteed not only under normal conditions, but also during natural disasters. The seismic assessment of the masonry buildings of the Gründerzeit (1840–1918) in Vienna is a central topic in the qualitative and constructive assessment. Although masonry construction has been used for many centuries, the realistic evaluation of the load‐bearing behaviour is still a complex challenge. The methods of analysis according to current regulations are only insufficiently able to reflect the real load‐bearing behaviour and the possible activation of global failure mechanisms. As a result, the simplified verification is often difficult to calculate for many historic buildings, and questionable reinforcement measures are taken to compensate, even though the buildings have already experienced several earthquakes and survived most of them without damage. The present work deals with the approaches of current methods of analysis and aims to identify problem points and to compare them with time history analysis, which is supported by a powerful material model based on test series. It is shown that the conventional analysis for the historic masonry buildings without consideration of the interaction and load transfer effects as well as the characteristic construction methods only partially reflect the real load‐bearing behaviour. The work is intended to be a contribution to the technical expert discussions on the seismic safety of historic buildings and to stimulate the discussion on the formulation of realistic methods of analysis.     

Mikrostruktur und Eigenschaften HVOF‐gespritzter Schichten im System TiO2 – Cr2O3

Microstructure and properties of HVOF‐sprayed coatings of the TiO₂ – Cr₂O₃ system Thermally sprayed titanium oxide coatings are known for their good tribological properties and their electrical conductivity. The latter is due to oxygen deficiency from the stoichiometric composition TiO₂. These lattice defects can be ordered and are called crystallograhic shear planes. These structures are known as Magnéli phases. At high temperature in oxygen‐containing atmospheres the material forms isolating TiO₂, therefore the application under such conditions is restricted. At the titania‐rich side of the system TiO₂‐Cr₂O₃ also compounds with the structure of Magnéli‐phases are formed. According to information from the literature, these phases are stable in oxygen‐containing atmospheres and are therefore promising for corresponding coating applications at elevated temperatures. In this paper first results of systematic studies of microstructure and properties of HVOF‐sprayed coatings are presented.     

Eine innovativ im Sol‐Gel‐Prozeß hergestellte,hochporöse Siliziumoxidkeramik zum Knochenersatz – In‐vivo Langzeitergebnisse

A new high porous silica‐sol‐gel‐ceramics for bone grafting – in‐vivo long‐time investigations The new calcium phosphate ceramics was produced by a sol‐gel‐process at 200 °Celsius with silica (SiO₂) as adjuvant. The aim of this investigation was to test the osteoinductive effect of these bioceramics and to prove its biodegradation by means of animal experiments. One year old minipigs were used and divided into three groups (n=6). Critical size defects (>5cm³) in the mandible were filled by different materials (group1: 60 % hydroxilapatite [HA] + 40 % ß‐tricalciumphosphate, group 2: only HA; group 3: control, without ceramics). Eight months later clinical, histological, morphometrical and REM investigations concerning the state of former defected mandible were made. In groups 1 and 2 a complete reossification of the bone defects and a biodegradation rate of ceramics of more than 96 % were recognized. In conclusion silica‐calcium phosphate ceramics made by a sol gel method seems to be suitable for filling bone defects in men and is of interest for orthopedic surgery, traumatology, craniomaxillofacial surgery and dentistry. Recently a clinical study was started.     

Innovative façade technology using masonry – Solid construction 2.0 / Innovative Fassadentechnik mit Mauerwerk – massiv construction 2.0

This article illustrates the solid building envelope both as an integral system and in terms of its potential for additive manufacturing. The Façade Research Group at the TU Delft works on the building envelope, investigating strategic and process support for development and planning processes and renovation technologies, as well as functionally integrated building envelopes. The Institute of Structural Mechanics and Design at the TU Darmstadt undertakes research and development in the areas of materials technologies (glass, polymers) and additive manufacturing as they relate to building structure.     

Verification of sound insulation in residential building – the new DIN 4109 / Nachweis des Schallschutzes im Wohnungsbau – die neue DIN 4109

The central sound insulation standard for building in Germany, DIN 4109, was issued in a revised version in July 2016. The calculation procedures described in the standard can now be used to verify constructional sound insulation for masonry buildings with insulated external walls. For other building materials and construction methods, the minimum requirements can be verified, or if required the enhanced requirements. Measurements in completed buildings confirm the results and show that provided the construction materials are suitable and the specialist design is correct, good sound protection is regularly achieved.     

Thermisch‐mechanisches Ermüdungsverhalten der partikelverstärkten Aluminiumknetlegierung EN AW‐6061‐T6 und die Entwicklung von Eigenspannungen im Matrixwerkstoff unter thermisch‐mechanischer Beanspruchung

Thermal mechanical fatigue behaviour of particle reinforced EN AW‐6061‐T6 and development of residual stresses in the matrix material by thermal mechanical loading The behaviour of non reinforced and 15 Vol.‐% α‐alumina particle reinforced wrought aluminium alloy EN AW‐6061‐T6 in thermal mechanical fatigue loading was investigated at different maximum temperatures. The tests were performed in strain controlled mode by means of an electro‐mechanical testing machine. Alternating load deformation and life cycle behaviour either materials were compared. It came out, that the reinforcement leads to an decreasing thermal mechanical fatigue life cycle while keeping constant the maximum temperature and mechanical loading. The two materials showed softening behaviour due to high maximum temperatures of 573 K to 673 K. However, there is an intense scatter of the number of cycles to failure of the non reinforced alloy aggravating the interpretation of the results. On the other hand the thermal mechanical life cycle increases in combination with increasing maximum temperatures. Simultaneously the part of plastic deformation in mechanical loading increases for both materials, while for a constant total strain range the effective maximum and minimum stresses are decreasing. Furthermore, the development of residual stresses in the matrix of the reinforced alloy by thermal mechanical fatigue loading was analysed. It was observed that only small absolute values of residual stresses will be obtained for these loads. Nevertheless, tendencies of mounting tensile residual stresses can be identified in the direction of thermal mechanical fatigue loading and subsequently reduction of the residual stresses.     

Neue Methoden zur Beurteilung der Betriebsfestigkeit im Fahrzeugauslegungs‐ und ‐absicherungsprozess

Advanced durability evaluation in vehicle design and validation process The modern process of evaluation and validation conducted in the automotive industry uses experimental, metrological, and calculation‐based methods. Offering various examples, the present paper describes new developments in the determination and evaluation of operating strength, particularly in terms of virtual methods and their application in practice. The first point considered is the virtual determination of load data, the second is the improvement of calculated fatigue life. Two current examples in the development of methods are presented in this context: The first example examines the inhomogeneity of materials in calculating aluminium castings. The second example describes the approach taken in the configuration of components made of short‐fibre‐reinforced polymers, applying a new method of calculation.     

Current developments in fire protection – Changeover to design and classification according to the Eurocode / Aktuelle Entwicklungen im Brandschutz – Umstellung auf die Bemessung und Klassifizierung nach europäischen Normen

The European requirements for fire safety design and testing of structural masonry members are already the governing requirements in many cases. In principle, both the European and the German classification may be used according to the Bauregelliste. However, the latter may only be used when European classification of a member or construction material is not possible because the appropriate European standards do not exist. The European standards do not differ fundamentally from the German standard DIN 4102‐2. One significant difference is that according to the DIN 4102‐2, it was required to carry out two tests with the most unfavourable result governing, while according to the European standard, only one test is required. According to the EN Standard, the tests for fire resistance and the reaction to fire are carried out separately. There are other differences related to the pressure in the furnace as well as the use of plate thermocouples instead of jacketed thermocouples. Fire safety design of masonry is carried out in accordance with EC 6‐1‐2 and the National Annex. Only the members not regulated in the EC 6‐1‐2, e.g. pre‐cast masonry members, non‐load‐bearing walls, lintels, connections and joints, should be designed and checked according to the revised DIN 4102‐4.     

CJEU Judgment,Standardisation and Eurocode 6 / EuGH‐Urteil,Normung und Eurocode 6 – Aktuelle Fragen im Mauerwerksbau

This article reviews current challenges for the masonry industry from a regulatory perspective. First, the CJEU judgment and its consequences will be discussed. The judgment of 16 October 2014 will make fundamental changes in the German regulatory system necessary. How these will be implemented is not yet clear so that this article can only give an overview of the present situation (September 2015) in the discussions. What is clear is that the changes in the regulatory system will have repercussions in the field of standardisation. These repercussions will be outlined – in general and specifically for the masonry sector – in the second part of this article. Finally, the paper will look at the progress in the implementation of Eurocode 6 (Design of masonry structures).     

Sicherer und wirtschaftlicher Betrieb von Kraftwerken – Ergebnis der Forschung im Bereich Werkstoffe,Auslegung und Instandhaltung

Safe and Economic Operation of Power Plants – Research Results in the Field of Materials, Design and Maintenance Components of power plants which undergo high temperatures are subjected to complex loading situations. The requirements on the used materials result from the special operation conditions of the plants and have to be adjusted to the steadily growing requirements on higher efficiency of the complete power plant as well as to those of safe and economic operation. The expenses for control and downtimes are directly connected with economic efficiency and availability. However, in case of new procedures or components it is not possible to revert to the existing know‐how. Different failure mechanisms than known before can occur. The same goes for the load situation. Therefore the knowledge base has to be extended to in‐advance or even parallely running scientific examinations that life assessment and maintenance strategies can be applied which guarantee the operational reliability and the efficiency of the plant. The main emphasis of these F&E works has to be put on condition monitoring based on actual operational data, the standard materials’ and component’s behaviour (deformation, damage and failure behaviour) in connection with design of components and the related material laws. In the framework of applied AVIF projects, following problems are handled:. – qualification of materials by determinating parameters related to practise. – optimal design of components by making available material laws and numerical tools. – economic manufacturing of components by qualifying processing methods such as welding. – The results can be transferred to concepts for safe and economic operation of power plants, especially for newly introduced materials for which there is no operational experience available.     

Aluminium alloys exposed to borderline solutions – a methodology to evaluate the susceptibility to corrosion fatigue with respect to corrosive de‐icers

In addition to high mechanical loads certain components for the automotive industry are exposed to corrosive environments, especially during winter, when corrosion promoting de‐icers are essential to sustain road traffic. The underlying research work contributes to the evaluation of the corrosion fatigue performance of aluminium alloys relevant for automotive application generally, while the present text focuses on wrought alloys. Aluminium alloys are of special interest because of the opportunity to reduce expenses for an additional corrosion protection and to support lightweight construction of vehicles. Components exposed to simultaneous mechanical and corrosive service loads as well as corrosion tests of different scale level (immersion and cabinet testing, long term outdoor exposure of components, usage on test carriers) were analysed to evaluate typical forms of corrosion. Based upon the prevailing damaging mechanism of material conditions with known differences in susceptibility to specific forms of corrosion, like intergranular corrosion or pitting, methods were derived to evolve service relevant types of corrosion during laboratory tests.     

Flussmittelfreies Hartlöten unter reaktiver Prozessgasatmosphäre – ein alternatives Verfahren zum Fügen von Aluminiumwerkstoffen

Flux‐free brazing under reactive process gas atmosphere – an alternative process for joining of aluminium materials Due to the high affinity of aluminium towards oxygen, joining of aluminium materials has ever been a challenge. In particular the efficiency of the process and the abandonment of fluxes during controlled atmosphere brazing have been within the focus of current research projects. The specific addition of reactive gases to the inert process gas atmosphere offers a suitable possibility of aluminium brazing without the use of fluxes. Under the application of hydrogen chloride the activation of the brazing and the workpiece surfaces is to be initiated, thus leading to dissolving the oxide layers. Moreover, the strongly reducing gas silane is used, which specifically removes oxygen and water residuals from the controlled atmosphere. Through a suitable controlled atmosphere brazing process the combination of both, reductive and activating additions, is to be used and tested upon their influence on the gas mixtures and materials used [1–5].     

Chemische Zusammensetzung und Mikrostruktur polymerabgeleiteter Gläser und Keramiken im System Si–C–O. Teil 1: Phasenidentifikation mittels Si‐L2,3‐Ionisationskanten‐Elektronenenergieverlustspektroskopie nach dem Fingerprint‐Verfahren und energiegefilterter Durchstrahlungselektronenmikroskopie

Chemical Composition and Microstructure of Polymer‐Derived Glasses and Ceramics in the Si–C–O System. Part 1: Phase identification by means of Si‐L_2,3‐ionisation edge electron energy‐loss spectroscopy according to the fingerprinting technique and energy‐filtered transmission electron microscopy Polymer or precursor ceramics represent a novel class of high‐performance materials that are produced by controlled pyrolysis of organometal compounds. Shrinkage and porosity resulting from thermal decomposition can be compensated by adding chemically reactive filler powders. This technique permits manufacturing of dense ceramic bulk components true to size by cost‐effective near‐net‐shape forming of cross‐linked green compacts. For process control, definition of the course of the reaction of the active fillers and thus the exact knowledge of the chemical composition and the microstructure development of the solid residues during pyrolysis of the polymer precursor is required. Due to both the great technical importance of the final ceramic products and their economical availability, in the present work, thermal decomposition of a silicone resin (polymethylsiloxane) at temperatures between 525 and 1550 °C was characterized nanochemically and microstructurally. In part 1, the results of the quantitative phase identification by means of analytical electron microscopy are reported. The bonding state of silicon was determined by fine structure analysis (Si‐L_2,3‐ionisation edge) of the electron energy‐loss spectrum and has proved to be always mainly oxidic. By means of energy‐filtered transmission electron microscopy, elemental distributions in the nanometre range were recorded. The phase separation of the polymer‐derived Si–C–O matrix into SiO₂, C and SiC could be proved definitely. The characterization of structure formation by high‐resolution imaging and diffraction methods follows in part 2.