PSI - Issue 58

M.R.A. Rahim et al. / Procedia Structural Integrity 58 (2024) 9–16 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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to the microstructure M4, represented in light green. From the plotted graph, the microstructure M4, required 6,477 cycles, while the microstructures M1 to M3 required an average of 4,310 cycles for the first crack segment to appear. The number of grains for both microstructural morphologies is the same, with 199 grains in the microstructure model measuring 0.3 mm × 0.3 mm, as in Fig. 1(c). Abaqus volume measurements revealed that the average grain size for both microstructure types was 25.85 μm.

Fig. 3. The accumulated number of cycles between irregular microstructures with inhomogeneous (Average M1 to M3) and with homogeneous (M4) grain shapes, respectively, at stress amplitude 425 MPa.

Fig. 3 shows that the number of cycles for fatigue crack initiation for the microstructure M4 ends after 17,356 cycles. The microstructures M1 to M3 demonstrate less fatigue resistance, requiring 15,201 cycles until the fatigue crack initiation ends. This leads to a 13.24% greater fatigue resistance for the investigated homogeneous microstructures in comparison to the inhomogeneous microstructure morphology.

Fig. 4. (a) Irregular microstructure M1 at fatigue crack initiation end, (b) The situation of a grain before crack nucleation, (c) crack nucleation happens, (d) crack elongates through the grain.