Direct Position‐Based Solver for Stiff Rods

In this paper, we present a novel direct solver for the efficient simulation of stiff, inextensible elastic rods within the position‐based dynamics (PBD) framework. It is based on the XPBD algorithm, which extends PBD to simulate elastic objects with physically meaningful material parameters. XPBD approximates an implicit Euler integration and solves the system of non‐linear equations using a non‐linear Gauss–Seidel solver. However, this solver requires many iterations to converge for complex models and if convergence is not reached, the material becomes too soft. In contrast, we use Newton iterations in combination with our direct solver to solve the non‐linear equations which significantly improves convergence by solving all constraints of an acyclic structure (tree), simultaneously. Our solver only requires a few Newton iterations to achieve high stiffness and inextensibility. We model inextensible rods and trees using rigid segments connected by constraints. Bending and twisting constraints are derived from the well‐established Cosserat model. The high performance of our solver is demonstrated in highly realistic simulations of rods consisting of multiple 10 000 segments. In summary, our method allows the efficient simulation of stiff rods in the PBD framework with a speedup of two orders of magnitude compared to the original XPBD approach.     

Invariant cones for non-smooth dynamical systems

In this paper we study the dynamics of piecewise linear systems with regard to generalisations of the familiar notion of Hopf bifurcation for smooth systems. It is shown that the concept of invariant planes with a change from a stable focus to an unstable focus through a center should be replaced in the case of non-smooth systems by an invariant cone with similar dynamical behaviour. In that way results for planar systems are extended into higher dimensions. To determine the invariant cone and its stability properties various extended systems are derived.     

Modular Micro Reaction System Including Ceramic Components

Micro reaction technology offers the possibility to improve the flexibility, selectivity, and mobility of chemical reactions in the chemical industry, process engineering, or pharmaceutical industry. In comparison with conventional chemical devices, the scale down to a millimeter or micrometer scale will result in remarkable time and cost savings, especially in the area of research and development of smaller- and medium-sized enterprises and at universities. The Fraunhofer Alliance Modular Micro Reaction System (FAMOS), consisting of six Fraunhofer institutes, has developed a software-based micro reaction toolkit provided with all essential elements of conventional chemical devices, e.g., micro reactors, micro mixers, or analyzing modules. All these elements are arranged on a single platform. Besides modules made of other materials, ceramics play a dominant role in micro reactor components. Their chemical and thermal resistance show a number of advantages for application in micro reaction technology, especially in such cases when aggressive media are combined with high temperatures. For this reason, ceramic micro mixers and reaction modules containing multichannel plates for screening of catalysts or ceramic self-heating foam structures were developed. This contribution will introduce the modular micro reaction system FAMOS such as different ceramic modules. It will show the development of the modules including construction, shaping, covering, and testing.     

ZrO2 ceramics with aligned pore structure by EPD and their characterisation by X-ray computed tomography

Using the electrolytic gas generation during the electrophoretic deposition (EPD) from aqueous suspensions, planar zirconia green bodies with unidirectionally aligned pore channels were produced. Number, diameter distribution, and arrangement of the pore channels could be controlled by the experimental conditions such as the electrolyte content of the suspension, the applied electric field strength, and the kind of the deposition electrode. The green bodies were sintered at 1450 °C in air. Besides optical microscopy and mercury porosimetry, X-ray computed tomography was used for characterising the porous samples. The CT investigations were well suited for this purpose because they enabled a three-dimensional characterisation of the pore structure by a non-destructive method.     

Powder-binder separation in injection moulded green parts

For powder injection moulding (PIM) the ceramic powder is mixed with a thermoplastic binder system to achieve an injectable feedstock. In contrast to injection moulding of polymeric components, the binder must be removed after the shaping step before sintering the ceramic part to full density. During the mould filling process shear forces act on the blend that might cause separations of powder particles and binder. In this case polymer films form at the mould surface and at internal interfaces which induce microstructural defects in the debinded part. In particular for multi-component parts this effect is critical since binder films in the joining zone weaken the bonding strength between the two components that might even lead to delamination.For detecting binder separations within the injection moulded bulk material and at joining zones of two-component parts the microstructure of green samples has been studied. Since conventional machining techniques like grinding and polishing modify the original structure, e.g. when particles are pulled out of the matrix and binder smears onto the surface, a special ceramographic method for the preparation of cross-sections was applied. This approach bases on broad ion beam techniques and enables the simultaneous polishing of hard ceramic particles and soft polymer molecules without destroying the structure or producing a relief at the surface. In the analysed samples binder accumulations were found along flow lines, at weld lines, at boundaries of so-called dead water regions and at the interface of two-component parts.     

Intermixing and charge neutrality at DyScO3/SrTiO3 interfaces

Recently, interfaces between complex insulating oxides have attracted much attention due to their broad spectrum of electronic properties. Joining two materials of different polarity can provide highly conducting layers. The polar discontinuity delivers the driving force for a charge accumulation in the interfacial region which has been demonstrated for lanthanum-based perovskite interfaces with SrTiO₃. Here it is shown that the polar discontinuity can be accommodated by variations in composition of cation lattice planes at the polar oxide interface between DyScO₃ and SrTiO₃, where DyScO₃ holds the same polarity as the lanthanum-based perovskites. An intermixing extending over two monolayers at the interfaces for both the Dy–Sr sublattice and the Sc–Ti sublattice is quantified. As a result, charge neutrality is established by electrical compensation between neighbouring atomic planes.     

Investigation of Droplet Deposition for Suspensions Usable for Thermoplastic 3D Printing (T3DP)

Thermoplastic 3D printing (T3DP) is an additive manufacturing (AM) technology, which can be used for the production of dense single- and especially multi-material components. This becomes possible because of the combination of the precise deposition of small droplets of molten thermoplastic suspensions containing ceramic or metal particles, and a curing mechanism caused on cool down increasing the viscosity. In this paper, the droplet formation behavior of zirconia suspensions for T3DP (82 and 84 wt.%) was investigated. The droplet fusion factor (dff) is introduced to calculate the necessary distance between two droplets to form filament-like structures by fusion of adjacent droplets. Filament-like structures with a smooth surface and a nearly homogeneous cross section were manufactured for both suspensions with a dff of 44% or higher.     

Thermoplastic 3D Printing—An Additive Manufacturing Method for Producing Dense Ceramics

In our new approach—thermoplastic 3D printing—a high‐filled ceramic suspension based on thermoplastic binder systems is used to produce dense ceramic components by additive manufacturing. Alumina (67 vol%) and zirconia (45 vol%) suspensions were prepared by ball milling at a temperature of about 100°C to adjust a low viscosity. After the preparation the suspension solidified at cooling. For the sintered samples (alumina at 1600°C, zirconia at 1500°C), a density of about 99% and higher was obtained. FESEM studies of the samples' cross section showed a homogenous microstructure and a very good bond between the single printed layers.     

Additive Technology for EU Ecolabel Formulations

Currently, Bio -lubricants are still regarded as niche products. Within the global lubricant market, however, the ar-ea of environmentally acceptable fluids represents one of the fast growing markets with an estimated annual growth of more than 6% per year. This growth is supported by various market drivers such as legal regulations, public subsidies and the im-plementation of national or international labeling schemes.With the implementation of the European Ecolabel for lubricants in 2005, a common standard specifying ecological and performance requirements for Bio - lubricants was defined. Applying for the EU Ecolabel requires a comprehensive assess-ment, not only of the final formulation, but also of the additives used. Additives are required to meet specifications for oxi-dation and thermal stability, as well as to impart metal protection (of both steel and yellow metals), thus improving corro-sion protection and wear performance of the formulation. Therefore, it is challenging in terms of formulation technology to develop the right formulation that meets the technical specifications as well as the stringent requirements of the EU - Ecola-bel.The paper describes how, by using ester base fluids and additives currently available in the market, lubricants can be developed to meet the technical and eco - toxicological requirements of the EU - Ecolabel, approaching the performance lev-els of lubricants formulated with traditional base fluids.