PSI - Issue 39

Szymon Derda et al. / Procedia Structural Integrity 39 (2022) 441–449 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 5 Specimen C2F10 fracture showing initiation region and fatigue propagation direction

5.2 Fatigue life In Fig. 6 the maximum stress in the tantalum layer was plotted against the fatigue life. The data were presented in the stress range between 300 – 480 MPa and fatigue life range of 30 000 – 2 000 000 cycles. For each case, a linear regression line was calculated. Additionally, uncertainties of stress levels were assessed and put as error bars. Uncertainty evaluation was performed with the use of a total differential method (with declared errors of variables: Young’s modulus ΔE = 2% of the nominal value, force ΔF a = 0.5% of the measured value, specimen thickness Δt = 0.05 mm, a width of each layer Δw = 0.05 mm).

Fig. 6. Fatigue life curves for both regarded materials

Even though the Case 2 material performs slightly better in the considered stress range, the difference fits within the uncertainty of the stress level assessment. As a consequence, both data sets could be interpreted as one with no