Mismatch Effect Influence on the HCF Resistance of High Strength Steels and Their GMA Welded Joints

Abstract

The objective of this article is to present the newest results of our complex research work related to the high cycle fatigue (HCF) resistance of advanced high strength steels. HCF tests were performed on two strength categories (690 and 960 MPa) including quenched and tempered and thermo-mechanical types. During the HCF tests base materials and their gas metal arc welded joints were investigated at different mismatch conditions (matching, undermatching, overmatching). Measured and analyzed data about base materials and welded joints were compared and discussed. Statistical approach was applied during the preparation and the evaluation of the investigations, which increased their reliability. The parameters of the HCF design curves were calculated based on the Japanese method (JSME S 002-1981) which uses 14 specimens. During the evaluation the results were compared with each other and with literary data. According to the presented examinations the HCF resistance of the base materials is more advantageous than the welded joints. Both the steel production process and the mismatch effect have an influence on the HCF resistance, depending on the strength category and the steel type. The thermo-mechanically treated steel indicated better fatigue resistance than the quenched and tempered one of the same category.