Modell zur Analyse des knöchernen Anwachsverhaltens auf bioaktiv beschichteten Implantatoberflächen

Model to analyse the bone on‐growth on bioactive coated implant surfaces Especially on the field of bone regeneration, transient and permanent implants are an important method of therapy in the Orthopaedic Surgery. In this context, bioactive surfaces on metallic implants provide an improved contact to the surrounding bone. The goal of our study was to establish an in‐vitro test system to evaluate the on‐growth of bone‐derived cells on different surface coatings. Therefore, we invented a special kind of clamps made of commercially‐pure (c‐p) titanium and blasted with hydroxyapatite particles followed by electrochemically coating with calcium phosphate (BONIT®‐HA, BONIT®). Definite pieces of human cancellous bone were attached to these clamps, inserted onto tissue culture plates and cultivated in DMEM for ten days. Finally, the contact area between human cancellous bone and the implant surface was analyzed and the spreading of osteoblast‐like cells evaluated by scanning electron microscopy (SEM). A well‐spread morphology of bone cells was observed on the implant surfaces coated with calcium phosphate (CaP). In comparison the clamps without CaP coatings showed only a marginal growth of bone cells on the clamp surface. The presented newly in‐vitro test setup using titanium clamps coated with bioactive layers attached to human cancellous bone represents a well‐functioning model for qualitative evaluation of bone on‐growth.     

The equivalent stress on the critical plane determined by the maximum covariance of normal and shear stresses

The paper presents a new form of the stress criterion of multiaxial random fatigue. The criterion has been defined as a sum of normal and shear stresses with weight coefficients on the critical plane defined as the plane where the maximum covariance between shear and normal stresses occurs. Two forms of the criterion have been proposed.     

Zum Begriff des "oberirdischen Baukörpers" bei der Berechnung der überbauten Grundfläche gem § 32 Abs 2 sbg ROG 1998

Im Anwendungsbereich des sbg ROG 1998 muss die für die Berechnung der Grundfl?chenzahl (§ 32 Abs 2 sbg ROG) ma?gebliche "überbaute Grundfl?che" durch lotrechte Projektion des "oberirdischen Bauk?rpers" auf die Waagrechte ermittelt werden. In der Vollziehungspraxis bestehen – insbesondere im Zusammenhang mit Bauführungen in Hanglagen – verschiedene Rechtsauffassungen darüber, ob ein nicht mehr als 1 m über das angrenzende natürliche Gel?nde hinausragendes Gescho? (iSd § 32 Abs 5 sbg ROG 1998) einen berechnungsrelevanten Teil des oberirdischen Bauk?rpers bildet oder nicht.     

PVD – Eine Erfolgsgeschichte mit Zukunft

PVD – A success story with a future PVD coatings in the range of a few nanometers up to some microns have become state of the art in engineering technology. PVD coatings can be found anywhere in our everday lives. They are used in data storage mediums such as CDs or DVDs. Car or architectural glasses are improved by thermal insulation coatings. A diffusion barrier is achieved via PVD coatings at food packaging. For decorative aspects sham jewelery and accessoires are coated as well as fittings. In the last three decades PVD coatings have been established in a variety of technical applications acquiring wear protection and/or friction reduction. First, coatings for tools have been developed, later on for components as well. So, in the past lots of experiences have been made not only in coating development, but likewise in methodical product design. By contrast, the surface has not yet been regarded as construction element. Here the knowledge is just at the beginning. The achieved performance of coated components can be improved drastically if the tribological system consisting of coating, substrate and intermediate material is designed for one single application with regard to the macro‐ and micro geometry. An exemplary application derived from the collaborative research center (SFB 442) “Environmentally friendly tribosystems” at the RWTH Aachen university is discussed. Results of fundamental research and their way into industrial applications are presented. The research development is reflected with regard to the development of the industrial PVD market. Regarding a process chain for the exemplary application the development method of surface technology is explained beginning with the production up to field testing of a new product.