PSI - Issue 76

Vladimír Chmelko et al. / Procedia Structural Integrity 76 (2026) 131–137

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The fatigue properties of a material with a given chemical composition are influenced by the state of its microstructure [9, 10]. In general, the state of the microstructure is the result of the metallurgical process of material production and its subsequent heat treatment. The microstructure of metallic materials can only be changed and influenced locally as a result of technological operations in the production of individual components of the structure. Forging, machining or rolling can change the microstructure of surface layers. Components made from rolled sheets are specific. In these cases, the microstructure can also be influenced by the technological processes of material cutting. Laser cutting affects the microstructure at the cut edge of the sheet differently than punching or water jet cutting. This article is devoted to the analysis of the fatigue properties of steel sheets after laser cutting and mechanical punching.

Nomenclature YS yield stress

TS tensile strength HV Vickers hardness

2. Materials Three types of steel sheets, designated S355, S500, and S700, were analyzed in this experimental study. All three materials have very similar chemical compositions, as documented by spectral analysis in Table 1. Table 1 . Chemical composition of investigated stell plates. C Mn Si Cu Al Cr Ti Ni S355 0.156 0.533 0.026 0.035 0.03 0.028 0.016 0.011 S500MC 0.131 1.179 0.057 0.01 0.03 0.029 0.045 0.008 S700 0.178 2.5 0.020 0.017 0.022 0.057 0.098 0.04 These are low-carbon steels with a single significant additive element, Mn, which is present in the highest percentage in S700 steel. The chemical composition corresponds to the microstructure visible after standard preparation by fine grinding, polishing, and etching by nital is documented in Fig. 1.

a/

b/

c/

Fig. 1. Microstructure of steel plates:a/ S355; b/) S500; c/ S700.