Kritéria nízkocyklové únavy pro víceosé namáhání materiálu

Abstract

Dissertation deals with the criteria of low-cycle fatigue and the design of fatigue parameters. Because fatigue affects approximately eighty to ninety percent of structures or machine parts, the topic of fatigue is very relevant. Ignorance of fatigue processes can lead to large economic or environmental losses and, finally, the safety aspect of the structure is compromised.

The first part of the work describes the current situation in low-cycle fatigue of the material. Describes selected criteria of low-cycle fatigue. This is followed by fatigue tests of the material AA2124-T851, which is an aluminum alloy widely used mainly in the aerospace industry. Thanks to the fatigue experiments performed on eight deformation paths, the fatigue criteria were verified. Chapter 5 describes all the results. The experimental part is very important for the subsequent evaluation of the examined criteria.

The middle passage is devoted to the identification of fatigue parameters for the area of low-cycle fatigue. All findings were brought to life in the Matlab software environment and the constants were evaluated for the investigated aluminum alloy. The developed application allows to generate constants for any material and provides several outputs that help the user to present his results in the form of graphs or tables.

The next section is devoted to the implementation of selected fatigue criteria into Python software. The Fatigue Library has been developed for many years at the Department of Applied Mechanics of the University of Mining - Technical University of Ostrava, so this environment was chosen. Utilities were created for all criteria and everything was subsequently evaluated on AA2124-T851. The final part deals with the energy Jiang criterion, on which modifications were made leading to a better prediction of material life.