PSI - Issue 58

Włodzimierz Dudziński et al. / Procedia Structural Integrity 58 (2024) 54 – 60 W. Dudzi ń ski et al. / Structural Integrity Procedia 00 (2019) 000–000

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pattern. Such a structure is a result of the cooling after hot processing. Definitely such structure is not recommended for currying structures parts under high load since Widmanstätten pattern is sensitive to initiation and propagation of the fatigue fracture. There is incompatibility of the microstructure with certificate of the material used to manufacture axle. According to material certificate, axle was made from steel grade 40HM. It should be material after heat treatment (hardening and tempering) to hardness 235-241 HB (highly-tempered martensite).

Fig. 5. Fatigue fracture with well visible slip lines in two different sections. The arrow indicates the fatigue origin point.

Fig. 6. Section parallel to shaft axis with area of cross section change, where the fatigue origin point was located. Lines show chord and dimensions of the pit due to edge fillet with radius 0,84 mm.

4. FEM Analysis Due to the nature of the damage, a strength numerical analysis was performed. The goal was to define equivalent stress level in notches, where crack was initiated. The loads were adopted according to the PN-G47000-2 standard