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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.beyond the current state of the art, for example in the field of orthopedics, is an interesting task for development engineers. Due to their outstanding mechanical and biocompatible properties, titanium and titanium alloys, in addition to other materials, are at the center of development work [5][6][7].Of major interest is the implementation of open-porous structures in orthopedic implants. These structural elements provide excellent conditions to fulfil structural and functional requirements. Open-porous structures meet the mechanical requirements regarding surface quality as well as those regarding design conditions [8][9][10]. In addition, such structures offer a potential for solving the problems of different stiffnesses between human bone and full implants [11,12]. As a result of their geometry, open-pore structures offer the cells good conditions for nutrient supply, and consequently, the possibility to grow well into the pores. Characteristic features of open-pore structures like pore size and distribution as well as connectivity affect biological processes like cell migration and proliferation and as a result the regeneration process [3,13].The applications of open-porous and load-bearing structures in orthopedic ap...

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Abstract. This study focuses on the effects of volume fraction, size and geometry of different fillers on interparticle interactions in low-density polyethylene (LDPE) melts. For this purpose, the rheological properties of LDPE filled with various fillers have been investigated by means of high pressure capillary rheometry in consideration of different particle sizes. It has been shown that interparticle interactions vary depending on volume fraction of the fillers. Furthermore the aspect ratio of the particles has a great impact on tendency of particles to interact with one another. While fibrous and flake shaped particles have a great tendency to interact with one another, spherical particles, depending on the particle size, exhibit a transition from negligible to non-negligible interactions. It has been shown that on the basis of a generalized interaction function, that considers the transition from negligibly interactions to the domain of pronounced interactions, interparticle interactions can be taken into account mathematically for describing the flow behaviour of particle filled LDPE melts.

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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.