PSI - Issue 57

Lucas Carneiro Araujo et al. / Procedia Structural Integrity 57 (2024) 144–151 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

150

7

= 0

= 0

/

/

(a)

( )

Fig. 3. SWT mod prediction and experimental data of specimens with a micro hole, (a) uniaxial and combined in-phase and (b) combined out-of phase data. = − ×100% (10) Table 3. Fatigue strengths of AISI 4140 steel from √ parameter model. Loadings Mean EI % Maximum EI % Smooth specimen Uniaxial and combined in-phase 14.87 44.48 Combined out-of-phase 2.75 4.45 Specimen with micro hole Uniaxial and combined in-phase 3.88 18.65 Combined out-of-phase 0 0 All loads 5.38 44.48 5. Conclusions In this study, a novel multiaxial fatigue model based on the √ parameter was introduced. The modified Smith-Watson and Topper parameter, incorporating the maximum principal stress and the amplitude of the principal stresses obtained using the Maximum Variance Method, was found to be easy to calibrate without the need for fatigue testing, as it does not rely on material constants. The fatigue limit used in the model was calculated based on the √ parameter, eliminating the need for additional tests. The proposed model was evaluated using experimental data from a high-strength steel known to be sensitive to small defects. The specimens were tested under two conditions: smooth, without artificially introduced defects, and with a superficial micro hole. Different loading conditions were applied during testing. The accuracy of the model's predictions was assessed using an error index compared to the experimental data. The model demonstrated high accuracy, with a mean error below 6% and a maximum error below 45%. Larger errors exceeding 15% were only observed for one specific loading condition among the various conditions tested. Overall, the new multiaxial fatigue model yielded satisfactory results when compared to the data obtained from AISI 4140 steel under various loading conditions, considering both the estimated maximum non-metallic inclusion and the superficial micro hole present in the specimens.