Die Anwendung von Schallemission für die Schweißnahtkontrolle

The use of Acoustic Emission as a weld Quality Monitor . The results obtained from our experiments with spot welding, gas tungsten-arc welding, and submerged-arc welding demonstrate the potential of acoustic emission monitoring as a nondestructive test for welds. The real-time nature of the acoustic emission data sets this technique apart from other nondestructive methods used for weld inspection. Since the acoustic emission from weld defects is transient, empirical calibration is required for each application. Defects can be located approximately but the type of defekt cannot be determined.     

Einflußgrößen auf die Schweiß;kraft elektrischer Kontaktstücke in der Energietechnik

Parameters Influencing the Welding Force of Electric Contacts in Power Engineering . Main parameters influencing the accumulated frequency distribution of the welding force using bouncing contacts are: contact force, closing velocity, duration of bouncing, number of operations, testcurrent, phase displacement, frequency, moment of contact in relation to current zero at inductive load. The statistical distribution over a wide range of the values of the welding force is traced back on the relative position of the weldings on the surfaces of the contacts by means of a model. The influence of duration of bouncing, number of operations, contact force, opening velocity, value of test current and polarity on the welding force is described by accumulated frequency distribution plottings for various contact materials when making contact synchronous- and asynchronously.     

Sinterwerkstoffe für elektrische Kontaktstücke der Energietechnik und ihre Eigenschaften

Sintered Materials for Electric Contacts in Power Engineering and their Properties . In the field of electric contacts the task of material development lies in optimating of contact properties e. g. weld strength, erosion and contact resistance. Included is a survey of the systems of metal-metal, metal-metal compound and metal-metaloid including examples for base metals and additives. Knowledge of weld strength and erosion by arcing are necessary besides physical properties and structure for selecting contact materials. The properties mentioned have been measured by WATE (welding-arc erosion-test-equipment). The values of the weld strength are presented as cumulative frequency plottings. Joining-technique of contact and supporting metal is of special importance. A reliable connection is obtained by two-layer-contacts. Changes of structure caused by arcing are described; for example contacts from AgNi40, WCu30 and AgCdO12. Both, construction and modern contact materials have helped to increase the capacity of contactors and switches as well as the reliability.     

Die Bedeutung der Werkstoffauswahl für die Gebrauchstauglichkeit von Chemieapparaten Auswahlkriterien und Prüfverfahren

Materials selection and service properties of chemical plants – criteria of selection and testing methods . Materials selection and technical design – operating temperature and limit of stress – corrosion and abrasion resistance – corrosion testing methods – testing of corrosion behavior of welded joints.     

Anrißerzeugung in WC-Co-Hartmetall-Proben für die Messung des kritischen Spannungsintensitätsfaktors KIC

Precracking of WC-Co-Hardmetal-Specimens for Fracture-Toughness Testing The determination of a valid critical stress intensity factor K_IC requires an extremely sharp, well defined initial crack. Methods producing such a crack are well known for metallic materials, but they often can not be used with brittle materials, like cemented carbides or ceramics. Their low fracture toughness makes a controlled crack growth under pure tensile stress nearly impossible. More useful are precracking methods, utilizing a stress gradient to stop the crack at defined depth. A very simple methods uses the indentation of a hardness tester to produce a semi-elliptical surface crack, interfered with residual stresses. For different areas of application and specimen geometries, bridge indentation, wedge indentation and composite bending method produce cracks with a straight front. Also under cyclic loading, under tensile as well as under compressive stress, the creation of a sharp precrack, applicable in K_IC measurement, is possible.     

Ionen- und plasmagestützte Verfahren der Oberflächentechnik für die Randschichtbehandlung von Leichtmetallwerkstoffen

Surface engineering of light weight materials with ion- and plasma-assisted methods Increasing applications of light weight materials are expected in the future. Pursuing this trend surface engineering of these materials – especially ion- and plasma-assisted methods – swill be of increasing interest to enhance their wear and corrosion resistance. In a research co-operation some promising methods were examined on different aluminium and titanium alloys to assess their potential to increase the surface properties. Among these were magnetron sputtering of chromium nitride, ion beam assisted deposition of Cr/CrN and Al/A₂O₃ layers, ion implantation and ion beam assisted nitriding. Compared to the steel substrates the assessment of the mechanical properties such as the critical load of the scratch test of the coated light weight materials is different. Furthermore, it could be shown that both spherical section and glow discharge optical spectroscopy are useful methods to characterize the near-surface zone influenced by ion implantation.     

Rechnerprogramm für PC zum Nachweis der Tolerierbarkeit von Fehlern für Komponenten des chemischen Apparatebaus

A PC Program for Determination of the Acceptability of Defects in Components of Chemical Apparatuses The paper describes development and features of a PC program for the assessment of defects in components. The program based on approximate methods of linear elastic and elastic plastic fracture mechanics has several accuracy and effort levels and does not require special fracture mechanics expertise. A collection of material data is attached to the program.     

Beurteilung der Zuverlässigkeit von Schmiermitteln für die Feinwerktechnik

Assessment of the Reliability of Lubricants for Precision Machinery. The critical examination of the reliability of lubricants for instruments and precision machinery needs first the recognition of all the parameters influencing the efficiency of the lubricants. Afterwards these parameters have to be classified according to their significance of the application of the instruments and precision machinery. These numerous influences cause unexpected and very complicated interactions which often can only be recognized, if the instruments and precision machinery are tested under practical conditions. The very small quantities of lubricants used in the instruments and precision machinery require new techniques for examining the lubricated bearings. A well equipped laboratory and a serious planning of the tests as well are therefore indispensable.     

Umformtechnik für die Produkte von morgen

Metal forming for the products of tomorrow An increasing global competition, shorter product lifetimes and a higher demand for functionality, environmental soundness and quality, represents a large challenge for metal forming. Due to newly developed processes, metal forming at the same time has the possibility to expand into areas at present controlled by other manufacturing methods.     

Ionenbeschuss von Polymeren für die Medizintechnik

Ion Bombardment of Polymers for Biomedical Applications Ion implantation, a standard technology in the semiconductor industry, is also used since the 1960s for biomaterials. In the following, a variation of the method is presented for illustrative — plasma immersion ion implantation (PIII). In PIII treatments process times of less than a minute are found to be sufficient to change the surface energy at least for several weeks. In addition, a modified coefficient of friction, wear and topography can be obtained, with reduced wear rates and an increased roughness having a positive impact on the biocompatibility and the bioactivity. For combined coating and implantation processes with simultaneous energetic ion bombardment, an excellent adhesion is obtained even at room temperature. In addition to the formation of photo‐active surfaces, which may have an antibacterial effect here also an osteoinductive topography can be achieved.     

Plasmapolymerisation für die Hartbeschichtung von Kunststofflinsen

The use of plastic as a substrate material for optical lenses has been increasing in importance due to smaller density, simpler machining and lower price. However scratches present a major problem wherever the lens surface is exposed to the environment. Various processes have thus been developed to protect the surfaces with hard coatings. The most common technique is the dipping process while spinning or spraying are other methodsto apply lacquer. Common to all these techniques are the required post treatments such as drying and heat or UV curing. Safety considerations as well as the long processing time and the handling required between the different steps, gave rise to the development of new technologies. Plasma polymerization, a technology relying on plasma enhanced chemical vapor deposition (PECVD), is used to deposit dense organic layers with reproducible, well defined surface properties. In contrast to dip coating, plasma polymerization even coats strongly curved structures with good uniformity. This is important for bifocal or trifocal lenses, featuring sharp edges on the surface. Due to the wide range of refraction indexes (about n = 1.5–1.8) available by using different monomers, even the latest high index materials can be coated without disturbing interference fringes. After a survey of plasma polymerization basics, some aspects of industrial equipment and processes for ophthalmic applications are presented. An outlook into the future of plasma polymerization for optical applications concludes the paper.     

Anwendung des FWK-Konzepts für die Berechnung der Lebensdauer bei mehrstufiger Kriechbelastung

The application of the Consecutive-Wöhler-Curve-Concept in Computation of the life values for multi-stage creep It is known that at multi-stage creep load there cannot be calculated any reliable life values by means of linear damage accumulation hypotheses. A practicable non-linear statement was proposed by Pantelakis. Besides the one-stage creep life curve, results from two-stage tests are required for determining the damage exponent, With this exponent, which is a function of temperature and stress in the load stage applied first, the life values can be calculated only for two-stage sequences whose stress stages have to be identical to those of the two-stage tests. For the application of the consecutive Wöhler curve concept described in the following there is required the knowledge of the one-stage creep life curve and of the creep function for increasing and decreasing stress sequences derived from two-stage tests. Then, the life values can be calculated for the most different multi-stage loads. The stages should lie within the stress range used in the two-stage tests.     

Streuung der Werkstoffestigkeit und die Wahrscheinlichkeit für das Versagen von Probenstäben an ausgesuchten Beispielen

Scattering of Strength and Probability to Failure of Smooth Test Bars – on Selected Examples . The influence of scattering of material properties (distribution density function f) and of the loading spectrum (distribution density function g) on the probability to failure is discussed. For the distribution density functions f and g, simple model functions (Gaussian function, δ-function) were used. It is shown that in typical design situations, a small reduction of the scatter of the material properties may reduce the probability to failure to some orders of magnitude. The width of the loading spectrum is shown to be less important compared to the width of the scatter of the material properties. For materials with a large scatter of properties e.g. ceramics, the probability to failure is really high, even if a large safety factor is used. A satisfactory reliability for designs made from such materials can be reached, if lower limits of strength can be guaranted – e.g. applying advanced methods of material testing. Under this special condition, the width of the loading spectrum and the safety factor gains a large influence on the probability to failure.     

Werkstoffkennwerte für die Lebensdauerberechnung von Strukturen aus Stahlfeinblechen für den Automobilbau

Materials Data for Fatigue Life Calculation of Steel Sheet Structures for Automotive Engineering Within a joint project of the steel and automotive industry 17 steel sheet materials for automotive engineering in various delivery and forming conditions at temperatures of –40 °C, 22 °C and 100 °C were investigated. In the course of 37 test series strain controlled fatigue curves to crack initiation and stress‐strain‐curves under monotonic and cyclic loading were determined. All experimental data, hysteresis loops and determined cyclic properties are available in a database. A correlation between the mechanical properties from tensile tests and the properties from strain controlled cyclic experiments seems to be possible.     

Untersuchung der Verteilung und Intensität filamentierter Barrierenplasmen für die Behandlung von Oberflächen

The application of barrier discharges at atmospheric pressure in air expands on the market of plasma technology, because it is an ecological and cost‐effective alternative to other processes of surface treatment. These plasmas usually consist of a multitude of spatially and temporally localized filaments, whose distribution should be as even as possible for homogeneous treatment. This holds especially for the plasma treatment of sensitive goods such as wool or other textiles. In equipment for continuous pass of material the barrier arrangements often consist of a system cylinder – cylinder or cylinder – plane, whereby the gap width changes locally. Space distribution and intensity of filaments has been investigated by means of short‐time photography and spatially resolved measurement of current distribution and energy distribution derived from it. The local dependency found can be explained by means of a capacitive equivalent circuit.