FATIGUE CRACK GROWTH IN TWO DUAL-PHASE STEELS USED IN AUTOMOTIVE WHEELS DISCS

摘要

In this paper, fatigue crack growth has been studied in two dual-phase steels used in the automotive industry, with 8.8% to 12.5% of martensite volumetric fraction. The thickness of the specimens was 3.95 mm. C(T) specimens were used in this study. The differentiation of the steels links with its chemical composition: one of the steels possessed chromium while the other steel possessed silicon as an alloy element. Besides the chemical composition, anisotropy (L-T and T-L specimens) of the materials and the effect of R stress ratio (0.3 and 0.6) in the resistance to fatigue were verified. Results showed that the two steels present a similar behavior in fatigue crack growth resistance. It was not noticed significant effect of anisotropy in both steels, while an increase of R ratio increased the growth rates and decreased the value of △K_(th) of the materials.