Dauerschwingfestigkeit bei hohen Mittelspannungen

FKM 1999
Booklet No. 246
Project No. 210

Abstract:

Numerous components are subjected to high static loads, with additional dynamic loads of smaller amplitude to be endured. The technical regulations, which are based on the nominal stress concept, limit the upper stress by means of the static calculation against a yield strength. Regardless of how it is defined, this represents a very conservative design limit. For this reason, the strength verification of components in mechanical engineering and vehicle construction in the area of high medium stresses is currently carried out experimentally. A reliable calculation method is not available. In the new version of the FKM guideline, the proof stress limit has been increased by a factor of 10 on the basis of a number of experimental findings. Based on an extensive test program on the materials X 22 CrMoV 12 1 and GGG 40, the influence of tensile stresses on the fatigue strength and on the cyclic material behaviour is investigated. In a total of 16 series of tests, the fatigue strength of differently notched specimens at different stress ratios under axial loading is determined using the staircase method. The results of the fatigue strength tests are Haigh diagrams for both materials, which cover a wide range for the different shape numbers. The experimental investigations are rounded off by tests with interspersed basic load cycles that simulate the start-up and shut-down processes of machinery. In addition to the investigations on fatigue behavior, the cyclic creep behavior is determined. In the accompanying theoretical investigations, an approach is developed to describe the cyclic creep as a function of the number of cycles and load. The model is implemented in the finite element program ABAQUS and successfully tested on the investigated sample geometries. On this basis, a design proposal is presented which superimposes the fatigue damage and the creep damage. The comparison of calculations with this partial damage model and tests shows good agreement. With the results presented, it is possible to estimate the stress amplitude that can be sustained at high medium stresses for metallic materials, so that a design is possible in the areas not covered by the technical regulations. The aim of the project was thus achieved. 148 pages incl. pictures and tables 01.07.1996 30.06.1998 BMWi / AiF-No. 10682 Institute for Mechanical Plant Engineering and Structural Durability (IMAB) Clausthal University of Technology (TUC) Head:
Prof. Dr.-Ing. H. Zenner Dipl.-Ing. S. Narberhaus (IMAB) Dr.-Ing. H. Kern, Siemens KWU, Mülheim Prof. Dr.-Ing. H. Kipphan, Heidelberger Druckmaschinen, Heidelberg