Background: Nowadays, hip cups are being used in a wide range of design versions and in an increasing number of units. Their development is progressing steadily. In contrast to conventional methods of manufacturing acetabular cups, additive methods play an increasingly central role in the development progress. Method: A series of eight modified cups were developed on the basis of a standard press-fit cup with a pole flattening and in a reduced version. The surface structures consist of repetitive open-pore load-bearing textural elements aligned right-angled to the cup surface. We used three different types of unit cells (twisted, combined and combined open structures) for constructing of the surface structure. All cups were manufactured using selective laser melting (SLM) of titanium powder (Ti6Al4V). To evaluate the primary stability of the press fit cups in the artificial bone cavity, pull-out and lever-out tests were conducted. All tests were carried out under exact fit conditions. The closed-cell polyurethane (PU) foam, which was used as an artificial bone cavity, was characterized mechanically in order to preempt any potential impact on the test results. Results and conclusions: The pull-out forces as well as the lever moments of the examined cups differ significantly depending on the elementary cells used. The best results in pull-out forces and lever-out moments are shown by the press-fit cups with a combined structure. The results for the assessment of primary stability are related to the geometry used (unit cell), the dimensions of the unit cell, and the volume and porosity responsible for the press fit. Corresponding functional relationships could be identified. The findings show that the implementation of reduced cups in a press-fit design makes sense as part of the development work.

Viscosity functions of particle-filled polymer melts are shifted to higher values in comparison with those of the unfilled polymer melts. This increase is affected by a number of factors such as the volume content, size, size distribution and the aspect ratio of the suspended particles. If interparticle interactions occur, which include the formation and breaking of agglomerates as well as the migration and rotation of particles during flow, the extent of the viscosity increase of suspensions also depends on the applied shear stress. Filler with a high aspect ratio, such as fibrous and plate-like particles, exhibits a strong tendency for interparticle interactions even at low volumetric concentrations. However, depending on the polymer matrix, spherical particles can exhibit a range of negligible interparticle interactions at low filler volume concentrations. Non-negligible interactions occur at higher filler concentrations. On the basis of the generalized interaction function, which considers the transition from negligibly interparticle interactions to the domain of non-negligibly interactions, the flow behavior of particle-filled polymer melts can be estimated. The subject of this chapter is the application of the generalized interaction function for the characterization of the flow behavior of particle-filled polyolefin melts.