Experimentelle Ermittlung von Werkstoffkenngrößen für innovative Leichtbauprodukte – Bauschinger‐Kenngrößen für 54SiCr6 auf Basis von Zug‐/Druckversuchen

Simulation of multiple plastic bending deformations processes with loadings vice versa needs suitable parameters. For high‐strength spring steel there are not enough investigations available. Investigation and comparison of appropriate parameters for 54SiCr6 will be shown. On the one hand the results of tensile/pressure trials at 54SiCr6 shows that Bauschinger‐Effect is existing. Dependence of tangent modulus and plastic reverse deformation to degree of plastic deformation are obvious. Tangent modulus is decreasing according to increasing plastic deformation – plastic reverse deformation increases according to increasing plastic deformation. Investigated parameters probably depend to degree of plastic deformation and do presumable not accord to deformation history.     

Nutzung von Werkstoffstrukturgrößen als Messnormale

Use of material structure sizes as measuring‐normal Lengths measurement is a comparison/evaluating of received measuring signals with a standard/calibration yardstick. The nano‐technology requires measuring accuracies from the submeter to the nanometer range, i.e. a range over 9 orders of magnitude. Strobes and possible measuringnormal are classified according to their requirements and analyzed on requirements, accuracy, stability, data sets and feasibility. For nano‐position‐ and nano‐measuring‐maschine are summarized suggestions for a feasibility.     

Bestimmung bruchmechanischer Kenngrößen für Probekörper mit elastischen,anisotropen Materialeigenschaften mittels Finite-Elemente Methode

Computation of Fracture-Mechanical Parameters for Specimens with Elastic Anisotropic Properties by Finite-Element Technique A method for direct calculation of the different mode m stress intensity factors K_m from the crack tip stress- or deformation fields of a finite element model is proposed that is suitable especially for linear elastic, anisotropic materials. The practical aim of the investigation was to get a procedure to split experimental results for mixed mode energy release rate, G_sum, into the the parts G_m of the pure modes m. This problem will raise for instance in the experimental characterization of delamination behaviour of fibrereinforced polymer composites with complicated sample geometries. The method is tested and the accuracy of the results is compared with well established solutions for the „double-cantilever-bea”︁ (DCB-) specimen.     

Charakterisierung des Ermüdungszustandes in zyklisch beanspruchten Schweißverbindungen durch röntgenographische und mikromagnetische Kenngrößen

Characterization of the Fatigue of Cyclically Loaded Welded Joints by X-Ray Diffraction and Micromagnetic Testing The fatigue behaviour of welded Joints is influenced by the state of the material, its microstructure and residual stresses. By means of the micromagnetic Barkhausen-noise testing method in connection with x-ray diffraction the behaviour of cyclically loaded welded joints of the steel S355 is investigated. Proved by the results of the present investigations, the macro-and micro-residual stresses, micromagnetic and strain characteristic values are strongly connected with each other. Plastic deformations in the HAZ and base material during cyclic loading were identifies by a significant relaxation of the micro-residual stresses and a characteristic change in the micro-residual stresses determined by X-ray profile analysis. Analogous to the growing plastic strain amplitude an advancing damage process in the material is accompained by a significant change in the micromagnetic parameters. As a conclusion the micromagnetic testing method can be suited for the identification of fatigue processes in the material before a final damager of the specimen.     

Auswertung von Stichproben normalverteilter,quantitativer Merkmalsgrößen

Estimates for the standard deviation of samples of metrical, normally distributed statistical variables can be determined by a number of different approaches leading to different results. In order to evaluate these approaches, a large number of samples were generated randomly with the help of a computer from a normally distributed population and evaluated in relation to the mean x and the standard deviation s. The hereby generated Characteristic statistical values x and s can then be compared to the Values of the underlying normal distribution. As this study shows, only the position probabilities Pì (normal ranks) derived by Henning and Wartmann deliver standard deviations ture to the expected values. Rosows commonly applied equation P_i = (3i – 1)/(3n + 1) is equally correct. All other methods examined result in systematic statistical deviations (bias) from the expected value. This includes the estimate s = $ \sqrt v $, taken from the variance v, which is used almost exclusively. The bias, however, is known due to this study and therefore can be corrected. Should outliers be eliminated, none of the appreaches investigated deliver standard deviations true to the expected values. The treatment of outliers is complex, however, and discussed in the paper. The confidence fpr the estimate of the standard deviation is independent of the method chose, i.e. none of the examined methods has an advantage over the others.     

Erprobungsmethodik für zyklisch überelastisch beanspruchte Bauteile unter Torsion – Bauschinger‐Kenngrößen für 54SiCr6

Power transmission contains several torsion‐stressed parts. Especially shafts and springs are numerous considered. Helical springs as a special type of springs are mainly stressed by torsion load. During operation the spring's load is basically elastic. In some cases, like overload or machine disaster, the load exceeds the spring's yield stress. For a single event the deformations can be calculated easily by using flow charts. However in other cases the spring will be stressed several times with alternating plastic load. Therefore the calculation will not be as easy as in the single load case. Especially the hardening and softening mechanisms have major influence on material behavior. For high strength steel this material behavior is not fully investigated right now. Present article shows a way how to investigate several important Bauschinger parameters based on plastic torsion load for the high strength steel 54SiCr6. Finally it can be shown that 54SiCr6 is influenced by the Bauschinger effect. On the other hand the needed material characteristic can be investigated by the shown methodology. Based on the identified data, analytical and numerical calculation of alternating plastic torsion load can be done.     

Einflußgrößen bei der Analyse von Schallemissionen

Factors Influencing Acoustic Emission Analysis . The interpretation of AE measurements requires careful consideration of the prevailing conditions, to ensure reproducable results. By the use of simulated signals in a small steel plate, an analysis of the effect of these various conditions, on the frequency and amplitude distribution of these signals, is possible. In this way the accuracy of location of emission sources can be improved.     

Fragen zu Vakuum‐Molekularpumpen

Questions about vacuum molecular pumps For experiments about gas friction we used a turbomolecular pump with magnetic bearings. The blade system was replaced by a cylinder of carbon fiber materal. lt rotates in a stationary aluminium cylinder at a distance of 0. 8 and 0. 4 millimeters at a rotating speed up to 48000 rpm. We got a linear dependance of the reciprocal values of pressure and viscosity in good agreement with other experiments in that field. Preparing experiments showed us our apparatus is working like a pump too. We saw differential pressures in dependance of flow and gas pressures. In our sytem pumping works against the flow resistance. The pumping range is limited by a graph showing the compensation of pumping and resistance. Here we have no flow through the system but only in tangential direction by the rotation The experiments showed graphs with 2 arms showing the compensaion of pumping and flow resistance. In the range between the arms the pressure difference reaches the highbest negativ numbers. That is the point of best pumping. The position of this point decreases to lower rotation frequencies with rising gas pressure and flow. The question is: what are the reasons for this behavior? Possibly the molecular pump developped by Siegbahn uses this effect. It makes higher compression rates by lowering the friction speed. The molecular pump of the Holweck type has at a constant rotation speed an optimal pumping effect at a certain nitrogen gas pressure and flow. At this optimum the pump makes high compression rates for additional hydrogen or helium.     

Membranvakuumpumpen als Turbo‐Vorpumpen

Diaphragm Vacuum Pumps for Backing Turbo Pumps State‐of‐the‐art turbo pumps with integrated molecular drag stage can be operated with forevacuum levels in the mbar range. Therefore oilfree diaphragm vacuum pumps can be used for backing. Advances of diaphragm technology and electronic drives for speed variable operation make diaphragm pumps even more compact, powerful and reliable. Long term tests running for more than five years indicate a diaphragm lifetime in excess of 40,000 hours and an excellent ultimate vacuum over the full operating time. Especially with variable speed drive systems maintenance intervals similar to turbo molecular pumps are now reachable.     

Bestimmung von Reflektorgrößen mit rechteckigen Ultraschallschwingern (b/a = 0,5)

Determining the size of reflectors using ultrasonic probes with rectangular crystals [b/a = 0,5] . When using ultrasound for testing large parts, either manually or automatically, rectangular crystals are often used instead of the usual disk shaped ones. For determining the size of a reflector however the auxiliary equipment used in conjunction with disk shaped oscillators has not been available for rectangular crystals. Therefore theoretic and experimental results are given here for determining the sizes of reflectors using rectangular oscillators with the ratio of the sides given by 2b/2a = 0.5.     

Röntgenographische Spannungsanalyse in einzelnen Kristalliten – Mess‐ und Auswerteroutinen sowie Einflussgrößen

X‐ray Stress Analysis in Single Crystallites – Measuring Method and Analysis Routines The X‐ray stress analysis in single grains of a coarse grained material can be performed by using the single crystal method. In this work theoretical basics and measuring algorithms for the single crystal method are presented. Test measurements on an iron‐silicon alloy were carried out for different wave lengths and for different lattice planes. It is demonstrated that the Mo‐Kα radiation is well suited for the X‐ray stress analysis in single grains of the material investigated.     

Beeinflussbarkeit der Bauteilgestalt durch Prozessstellgrößen beim Außenlängsdrehen von AlSi9Cu3 ‐ GJS400 Parallelverbunden

Influence of the process variables on the workpiece form accuracy in the machining of parallel compounds out of AlSi9Cu3 ‐ GJS400 To guarantee excellent work piece quality for the machining of compound materials characteristic interactions between the components have to be considered in the process design. Especially by parallel compounds, where the different components are processed in an alternating manner, the machinability of the compound differs considerably from the machinability of each homogeneous component. Depending on the compound partner the surface topography of a component can vary considerably. Rotationally symmetric compound work pieces primary hold radius and transition deviations. In addition to unequal tool and workpiece deflection the radius deviations results from the different topographies in each component. The surface topography and its measurement methods as well as the process parameters and their influence on the process forces have to be considered for a proper process design.     

Größeneinfluß auf die Schwingfestigkeitseigenschaften von Schweißverbindungen

The size effect on the fatigue properties of weldments Constant amplitude fatigue tests (R = ? 1 and 0)have been carried out in order to investigate the influence of specimen size and manufacturing conditions on the high-cycle fatigue behaviour of large welded I-beams (web height 500 mm, total length 12 and 7 m respectively). The specimens contained transverse butt welds and longitudinal fillet welds, mainly produced by manual metal arc welding. The Δs?-concept, as proposed in international standards for fatigue related design is supported by the test results as far as transverse butt welds or longitudinal fillet welds in large sections are concerned. The HCF-behaviour of butt joints in large sections, welded under site conditions, are reasonably covered by Eurocode 3 category 90. EC 3-Category 100 does not conservatively cover the HCF-behaviour of longitudinal fillet joints in large sections.     

Geometrieunabhängige bruchmechanische Werkstoffkenngrößen – Voraussetzung für die Zähigkeitscharakterisierung von Kunststoffen

Geometry independent fracture mechanics values – Requierenent for toughness characterization of polymers Starting from the history of introducing the Charpy test to the characterization of plastics, polymer‐specific requirements for the specimen geometry relevant for the determination of fracture mechanics parameters of plastics are summarized. Here, the influence of the specimen thickness, the specimen configuration and size, and a/W‐ratio are considered. In order to characterize the geometry independence of fracture mechanics parameters, in this connection, geometrical factors are used to estimate requirements for the specimen geometry without an experimental determination of the geometry influence. For plastics, these experimentally determined factors vary in a wide range. For this reason, the use of constant geometrical factors must cause a pronounced under‐ or overevaluation of the requirements on the specimens. The relationships between the geometrical factors and the fracture mechanics parameters those are universally valid for plastics are independent from the kind of loading (static, dynamic) and the crack propagation behaviour (stable, unstable).     

Laserstrahl‐Kurzpulsschweißen von Metallfolien

Laser Beam Short Pulse Welding of Metal Foils Joining of metallic foils by laser beam spot welding is applied in different fields of electronic production and micro joining technology. The main challenges hereby are the realization of weld spots with high quality, i. e. weld spots with high stability and smooth shape, as well as the stabilization of the process. By the application of short laser pulses usually used for drilling or cutting the time at which the melt pool exists can be reduced and therefore the probability of arising instabilities, too. Short laser pulses are pulses with a length lower than one millisecond; pulses with a pulse length lower than one nanosecond are called ultra short pulses. The attempt of welding metallic foils by short laser pulses provides also the advantage of a lower thermal influence of the material. And a more simple system technology is possible then because different manufacturing methods can be realized with one laser. The main intention of the shown results of some investigations is the qualification of the welding process. Hereby the reachable weld spot quality as well as the enlargement of the process window is of special importance.     

Übertragung von Schwingfestigkeitswerten mit dem statistischen Größeneinfluß

Transfer of Fatigue Life Data with the Statistical Size Effect The statistical size effect and the Basquin-equation are used to derive a function with the ability to describe the failure probability of fatigue data. Based on the results of fatigue tests the transfer of the life times to other specimens is possible. The specimens may differ in their shape and size. The assumptions, limitations and the potential of the proposed method are discussed and proved in a large experimental programme. Six specimen geometries where made of the Al-alloy 7075 T 7351 and loaded with two different load histories (Gauss, MiniTWIST). The highly stressed part of the specimens, where the cracks will originate, is characterized with stress integral. The location of the initial cracks is examined and correlated with the local stress, which is responsible for crack initiation.