Experimentelle und numerische Untersuchungen zum mechanischen Verhalten perforierter Aluminium‐Legierungen unter zyklischer Belastung

Experimental and numerical investigation of the mechanical behaviour of perforated aluminium alloys under cyclic loading The stiffness behaviour of perforated aluminium alloys under cyclic loading is examined in relation to the relative density. Different relative densities between 0.93 and 0.62 could be realized by modification of the hole spacing of the regular square penetration pattern. Unloading experiments were carried out for the determination of the stiffness change. The decrease of the gradient of the un‐ and reloading curves with increasing plastic deformation could be measured. The pore formation was verified exemplarily by using Scanning Electron Microscopy. The quantitative influence of a changing cell structure (size and shape) on the measured stiffness reduction was estimated by means of the Finite Element Method.     

Non‐linear viscoplastic polycrystalline intermediate modelling for texture evolution in FCC metals: compression test

In this paper, we report predicted results for texture evolution in FCC metals under uniaxial compression test. These results are computed using a newly developed nonlinear rigid viscoplastic crystal plasticity model based on an intermediate interaction law. This interaction law is formulated by the minimization of a normalized error function which combines the local fields’ deviations, from the macroscopic ones, obtained by the classical upper bound (Taylor) and lower bound (Sachs) models. This interaction law leads to results lying between the upper and lower bound approaches by simply varying a scalar weight function ϕ (0 < ϕ < 1). A simple interaction law based on the linear mixture of the fields from the Taylor and Sachs models is also used. The results from these both the linear and nonlinear intermediate approaches are shown in terms of texture evolution under uniaxial compression. These results are discussed in comparison with the well known experimental textures in compressed FCC metals. Finally, we show that the linear intermediate approach yields fairly acceptable texture predictions under compression and that the fully non‐linear approach predicts much better results.     

Grenzflächenpressung von Eisenwerkstoffen und Leichtmetallen unter kontinuierlicher Beanspruchung

Limiting surface pressure under continued pressure of ferrous and lightweight metals In this article the results of tests examining the limiting surface pressure of ferrous and light weight metals are presented. The tests were carried out under consistent conditions using a standardised test procedure.     

The generation of nanocolloidal wear from stainless steel and titanium alloy and its toxic effects in a monocyte cell culture model

This study addresses the aspect of submicron‐sized / nanocolloidal wear comparing stainless steel (316L) and titanium alloy (TiAl6V4) for their toxic and inflammatory potentials. Wear was generated in a tribometer using the disc‐on‐pin‐method with pin and disc submerged in a sterile cell culture medium setting. The wear medium was separated according to Stokes' law into a fraction smaller 200 nm (nanocolloids) and a fraction greater 200 nm (particles). Vitality and inflammatory potential was measured in a cell culture model employing murine macrophages (J774). Cells were incubated with increasing concentrations (12.5, 25 and 50vol%) of either wear medium (particles and nanocolloids) from 316L and TiAl6V4. Vitality was measured by MTT assay and inflammatory reactions were quantified by TNF‐α ELISA. Nanocolloids from stainless steel and titanium induced strong, dose dependant toxic effects in the MTT assay while particles did not affect vitality in a dose dependant manner. The inflammatory response remained unaltered in all four groups. We conclude that interactions between soluble metallic wear and proteins forming nanocolloidal wear should be considered when conduction experiments addressing the aspect of biocompatibility in metallic implant materials.