Untersuchungen zur Dauerfestigkeit carbonitrierter Proben aus den Einsatzstählen 18CrNiMo7‐6und 20MnCr5

The endurance limit of carbonitrided specimens of 18CrNiMo7‐6 and 20MnCr5 case hardening steels were examined under bending conditions. Four variants were manufactured differing in heat treatment and surface conditions. Besides conventional gas carburised variants, carbonitrided specimens with a low and a raised nitrogen content of 0.2 and 0.45% at the surface as well as a carbonitrided and ground variant were examined. The specimens were tested with stress ratios R = –1 and 0. Depending on the nitrogen content cyclic loading evokes compressive residual stresses at the specimens' surfaces, caused by elastic‐plastic deformation. Specimens of the ground variant show additionally a decrease of the residual austenite content when cycled. The induced compressive residual stresses are substantially responsible for high endurance limits at both stress ratios and are the key for understanding the beneficial effect of carbonitriding in this regard.     

Fertigung einer universellen Hüftprothesenpfanne mittels Hochdruckblechumformung

In recent years, the use of hip prostheses has become a routine procedure. The use of total hip replacement has evolved in recent years to a routine procedure. Despite this experience, it always comes back to complications. Especially the migration or loosening of the acetabular component because of the artificial load adaptive bone remodeling is still a current problem. This is due to the changing mechanical situation after the implantation of the prosthesis. Another problem is the high bone loss during implantation, which complicates a revision of the prosthesis. One solution is the use of patient‐specific prostheses. So far, the use of these prostheses is limited due to the time‐consuming and cost‐intensive production. The overall objective of the presented project in this publication is the development and establishment of an innovative concept for the production of patient‐specific hip prosthesis made of titanium plates by sheet metal forming. The idea of this concept involves the development of a two‐stage process. First of all a standardized hip prosthesis is made by high‐pressure sheet metal forming and then individually in the second step. This publication contains the derivation of the standard prosthesis. For this purpose, a design methodology was generated, based on the so‐called agglomerative clustering. In addition, presents the results of the numerical preliminary design of the first stage of the process and the tool developed concept in the course of this paper.