Restrictions in the design of gear wheel components and drives for micro technology

 According to enhanced interest for use of micro mechanical gear drives increased requirements occur for the transmittable power output with at same time proceeding miniaturization. To meet these future necessities research trends lead to micro technical parts from metal and ceramic materials. Using these materials the design of the parts has to meet restrictions of several disciplines, predominantly manufacturing and moulding technologies. Received: 10 August 2001/Accepted: 24 September 2001 This paper was presented at the Fourth International Workshop on High Aspect Ratio Microstructrue Technology HARMST 2001 in June 2001.     

Validation of micromechanical systems

For a reliable function of micro-mechanical systems the behavior of the used gear wheels is of extreme importance. But up to now there is no general available method for quality assurance of them. In this paper an adoption of the tangential and radial composite inspection as defined in standards for macroscopic gear wheels to the special needs and boundary conditions in micro technology is proposed. It is based on an examination of the differing results if the same gear wheels are mated with varying angles of rotation. Additionally special test rigs are presented which are able to test micro gear wheels. Finally some exemplary results are shown.     

Micro-specific design flow for tool-based microtechnologies

Design of systems and components being produced with tool-based microtechnologies is strongly driven by technology. Thus, there are multitechnological influences from production, materials or micro-specific effects, which restrictively affect design and have to be considered. Under special regard of these peculiarities and in context with live cycle stages of tool-based microtechnological products, a design flow is presented. This incorporates a new design model, called sickle model visualizing the specific aspects when designing products of tool-based microtechnology. In order to support the design process, design rules are used to transfer knowledge from subsequent and adjacent life cycle stages to the current design stage.     

Comparison of pure and “Latinized” centroidal Voronoi tessellation against various other statistical sampling methods

A recently developed centroidal Voronoi tessellation (CVT) sampling method is investigated here to assess its suitability for use in statistical sampling applications. CVT efficiently generates a highly uniform distribution of sample points over arbitrarily shaped M-dimensional parameter spaces. On several 2-D test problems CVT has recently been found to provide exceedingly effective and efficient point distributions for response surface generation. Additionally, for statistical function integration and estimation of response statistics associated with uniformly distributed random-variable inputs (uncorrelated), CVT has been found in initial investigations to provide superior points sets when compared against latin-hypercube and simple-random Monte Carlo methods and Halton and Hammersley quasi-random sequence methods. In this paper, the performance of all these sampling methods and a new variant (“Latinized” CVT) are further compared for non-uniform input distributions. Specifically, given uncorrelated normal inputs in a 2-D test problem, statistical sampling efficiencies are compared for resolving various statistics of response: mean, variance, and exceedence probabilities.     

Adaptive anisotropic meshing for steady convection-dominated problems

Obtaining accurate solutions for convection–diffusion equations is challenging due to the presence of layers when convection dominates the diffusion. To solve this problem, we design an adaptive meshing algorithm which optimizes the alignment of anisotropic meshes with the numerical solution. Three main ingredients are used. First, the streamline upwind Petrov–Galerkin method is used to produce a stabilized solution. Second, an adapted metric tensor is computed from the approximate solution. Third, optimized anisotropic meshes are generated from the computed metric tensor by an anisotropic centroidal Voronoi tessellation algorithm. Our algorithm is tested on a variety of two-dimensional examples and the results shows that the algorithm is robust in detecting layers and efficient in avoiding non-physical oscillations in the numerical approximation.     

Influence of the V2O5 Loading on the Structure and Activity of V2O5/TiO2 SCR Catalysts for Vehicle Application

In this paper the effect of the vanadium oxide loading on the surface vanadia structure and the activity as well as selectivity in the catalytic reduction of NO with NH₃ was studied for a V₂O₅/TiO₂ model system. A series of TiO₂ (WO _x stabilized anatase) supported vanadia catalysts with varying loadings were characterized by laser Raman spectroscopy, ⁵¹V MAS-NMR, V K XANES. To determine the acidic properties, DRIFTS measurements were done with pyridine adsorbed on the samples. The measurements indicate that with increasing active phase loading square pyramidal coordinated surface vanadia species are replaced by an amorphous highly dispersed vanadium oxide phase with a coordination like V₂O₅. In addition, the ratio of Brønsted to Lewis acid sites is shifted from a comparatively low to an equal level at high loadings. This structural change is accompanied by a clearly improved catalytic activity and selectivity.     

Knowledge-based design environment for primary shaped micro parts

This contribution describes a prototypical knowledge-based design environment predominantly concentrating on the production-relevant design of micro parts. In this environment a computer-aided knowledge base is linked with a design system (CAD-system). In contrast to a complete knowledge-based design, i. e. modelling a part by the rule-based connection of distinct basic objects or features (which is a matter of structured combination rather than creative designing) the prototype presented promzotes conventional practical design. The designed part is subsequently checked on the basis of parameters derived from the geometry of said part.This paper was presented at the Fifth International Workshop on High Aspect Ratio Microstructure Technology HARMST 2003 in June 2003. The work is part of the DFG (Deutsche Forschungsgemeinschaft) funded collaborative research center 499 Development, production and quality assurance of primary shaped micro components from metallic and ceramic materials