Energy optimized jerk-decoupling technology for translatory feed axes

Dynamic feed axes for machine tools are usually optimized for high jerk rates. This, however, might lead to excitations of the machine frame due to reaction forces of the linear motor. This paper describes the development of a jerk-decoupled feed axis with an innovative guidance system and energy-optimized spring-damper-elements. An accomplished system simulation is based on an energy observer applied to accomplish the energy-optimal design of an example jerk-decoupled feed axis. The simulatory results are verified at a test bed using adjustable adaptronic components. A concluding verification proves the positive effects of this technology without negative effect on the accuracy.     

Microstructuring of functional surfaces by means of cutting processes

Microstructuring of mechanically and thermally highly stressed surfaces offers an innovative alternative for adjusting tribological properties and thus reducing friction losses and wear. At the Institute of Production Engineering and Machine Tools (IFW) functional surfaces are structured via cutting. This paper introduces to the basic principles of manufacturing microstructures in ductile materials foccussing cutting tool- and process-dimensioning. Scratch tests are carried out at planar surfaces to describe the basic chacacteristics when producing structures in micron range. Due to the small structure depths, size effects have to be considered. On this account, influences and interrelations of cutting edge microgeometry, material properties, as well as cutting parameters are investigated. In order to avoid further finishing operations, sharp structures with tolerable burr formation have to be achieved. The investigations presented in this paper are supported by the German Research Foundation (DFG) within the project “Microstructuring of Thermomechanically High Stressed Surfaces”.     

Comparison of residual strength behavior after indentation,scratching and grinding of zirconia-based ceramics for medical-technical applications

In this study, three methods of characterizing the damage tolerance of different zirconia-based ceramics for medical-technical applications are presented. The damage is inflicted statically, with Vickers hardness impressions and dynamically by scratching with a Rockwell diamond, as well as by means of a reproducible grinding process. The damage intensity is, in each case, successively increased.The measured strength values as a function of the inflicted damage thus provide information on the grinding robustness of the material. This permits the determination of critical grinding parameters above which the component quality is impaired and, ultimately, the patient is endangered. The continuing pressure to reduce production costs by shortening processing times makes damage tolerant behavior of materials extremely important. Ultimately, this permits the reduction of production costs while maintaining component quality and the guarantee of future patient safety.     

Threshold-avoiding proteomics pipeline

We present a new proteomics analysis pipeline focused on maximizing the dynamic range of detected molecules in liquid chromatography-mass spectrometry (LC-MS) data and accurately quantifying low-abundance peaks to identify those with biological relevance. Although there has been much work to improve the quality of data derived from LC-MS instruments, the goal of this study was to extend the dynamic range of analyzed compounds by making full use of the information available within each data set and across multiple related chromatograms in an experiment. Our aim was to distinguish low-abundance signal peaks from noise by noting their coherent behavior across multiple data sets, and central to this is the need to delay the culling of noise peaks until the final peak-matching stage of the pipeline, when peaks from a single sample appear in the context of all others. The application of thresholds that might discard signal peaks early is thereby avoided, hence the name TAPP: threshold-avoiding proteomics pipeline. TAPP focuses on quantitative low-level processing of raw LC-MS data and includes novel preprocessing, peak detection, time alignment, and cluster-based matching. We demonstrate the performance of TAPP on biologically relevant sample data consisting of porcine cerebrospinal fluid spiked over a wide range of concentrations with horse heart cytochrome c.     

Large‐Area Synthesis of Continuous and Uniform MoS2 Monolayer Films on Graphene

Heterostructures composed of multiple layers of different atomically thin materials are of interest due to their unique properties and potential for new device functionality. MoS₂‐graphene heterostructures have shown promise as photodetectors and vertical tunnel transistors. However, progress is limited by the typically micrometer‐scale devices and by the multiple alignments required for fabrication when utilizing mechanically exfoliated material. Here, the synthesis of large‐area, continuous, and uniform MoS₂ monolayers directly on graphene by chemical vapor deposition is reported, resulting in heterostructure samples on the centimeter scale with the possibility for even larger lateral dimensions. Atomic force microscopy, photoluminescence, X‐ray photoelectron, and Raman spectroscopies demonstrate uniform single‐layer growth of stoichiometric MoS₂. The ability to reproducibly generate large‐area heterostructures is highly advantageous for both fundamental investigations and technological applications.     

Tool behavior at alternating thermo-mechanical loads during milling of compounds out of aluminum and spheroidal cast iron

The mass of high-performance components can be reduced by the use of materials with a high ultimate strength. However, due to increasing demands on the performance of such components this design strategy reaches its limits, especially if certain parts of the components demand special physical properties. Therefore, in a load-dependent strategy hybrid components out of compounds are used. Through this, suitable materials are placed in the highly loaded component areas. This contribution presents results of experimental investigations of the tool behavior when milling compounds. The focus is on tool wear during face slab milling of a compound out of an aluminum alloy and a spheroidal cast iron. In order to distinguish between the thermal and mechanical influences on the tool wear, different material combinations are used. The influence of tensile strength is studied during the milling of materials with the same heat conductivity (GJS400/GJS600), while the influence of the heat conductivity is examined with materials with comparable tensile strengths (AW2030/GJS400).     

Active linear guidances for micro actuators: alternative concepts and first prototypes

In micro actuated systems, active guidances provide guiding a runner frictionless and fail-safe. Thus, the research objectives within the Collaborative Research Centre CRC516 sub-project C3 are related to aerostatic and magnetic principles for active guidances. Concerning guidances using the aerostatic principle, one version with thin-film techniques as well as one without were developed, manufactured with aid of other sub-projects, and tested. The force characteristics of the prototypes were determined and the dynamic behaviour of the aerostatic guidances was analysed within experimental investigations. Furthermore, an integrated capacitive displacement measurement system was developed and successfully validated within its prototypic functionality. Concerning the magnetic principle, guidances based on repulsive forces as well as on attractive forces were analysed. Hence, different types of controllers were developed and the behaviour of the controlled system was simulated by means of Matlab/Simulink and VisualNastran.     

Expandable graphite: A fire retardant additive for polyurethane coatings

The study investigates the mechanism of fire retardancy induced by expandable graphite in a polyurethane coating. A complementary investigation to the spectroscopic study performed previously confirms that little interaction occurs between the matrix and the additive. X‐ray diffraction study demonstrates that the crystalline structure of the graphite is maintained during the intumescent process. The presence of free radicals in the protective shield is then demonstrated but at low concentration compared with classical intumescent systems, such as for example polyurethane/ammonium polyphosphate. Finally, the physical properties of the char are then investigated. Blowing measurement demonstrates the high degree of expansion of the layer which may partially explain the fire retardant performance of expandable graphite in polyurethane. Surface analyses by optical microscopy and optical profilometry also enable a better understanding of the efficiency of expandable graphite. In the absence of a fire retardant additive the coating displays cracks and holes, providing a pathway for oxygen diffusion as well as heat and mass transfer between the flame and the virgin polymer. Both phenomena are limited when expandable graphite is added to polyurethane. Consequently, fire retardancy of expandable graphite results more from a physical than from a chemical action. Copyright © 2003 John Wiley & Sons, Ltd.     

Development of New Combined Manufacturing Technologies ‐ Influence of the Cutting Process on Workpiece Properties

Properties of materials for high‐strength structure components are influenced by production processes. These influences can be augmented by a combination of two presently consecutively executed process steps. The presented work shows first results in the development of novel combined manufacturing technologies, which along with prospective tools use this effect to adjust the material properties locally, adapted to the requirements. The combination consists of a merging of the process steps ‘material separation’ (metal cutting) and ‘changing properties’ (rubbing, rolling) to one single process step. For this purpose novel combined tools have to be developed. For the estimation of the possibilities of properties changes by combined processes at first the influences of single processes have to be determined. This contribution presents results of a “material separation” process. The investigated material is the industrially important aluminium wrought alloy AI7075‐T6, the applied process is orthogonal turning, the process parameters varied are cutting speed and feed as well as the tool geometry. Cutting force and feed force are measured, and the process influences on surface and subsurface properties are determined.