PSI - Issue 34

D. Rigon et al. / Procedia Structural Integrity 34 (2021) 154–159 D. Rigon and G. Meneghetti / Structural Integrity Procedia 00 (2021) 000–000

158

5

16.0

CM materials CM materials CM materials & AM R ≈ 0 R = -1 CM & AM R ≈ 0.5

14.0

12.0

10.0

6.0 ΔK th,LC,est [MPa√m] 8.0

4.0

2.0

2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0

ΔK th,LC,exp [MPa√m]

Fig. 3. ΔK th,LC,est versus ΔK th,LC,exp for R=-1 (Eq.2), R=0 (Eq.3) and R=0.5 (Eq.4).

3. Conclusions A summary of recent investigations by the authors has been presented regarding an empirical bi-parametric equations aimed at estimating the threshold stress intensity factor range of long cracks ΔK th,LC for different load ratios. The proposed model is applicable to wrought as well as additively manufactured metals and it is based on two material parameters, namely Vickers hardness (HV) and a material-dependent microstructural length ( l ). The four parameters of the model have been first calibrated for R=-1 by fitting appropriate experimental data taken from the technical literature and later on it has been extended to R = 0 and R = 0.5 by determining dedicated coefficients for each load ratio. The empirical model proved to estimate ΔK th,LC within an error band of ±20% for a quite wide range of wrought and additively manufactured metals. The proposed empirical model may be effectively used in fracture mechanics based models for fatigue design, when a first approximation approach is needed to estimate ΔK th,LC , in absence of experimental data obtained from the relevant standardized tests. References Atzori B, Lazzarin P, Meneghetti G (2003) Fracture mechanics and notch sensitivity. Fatigue Fract Eng Mater Struct 26:257–267. Atzori B, Lazzarin P, Meneghetti G (2005) A unified treatment of the mode I fatigue limit of components containing notches or defects. Int J Fract 133:61–87. Bartosiewicz L, Krause AR, Segupta A, Putatunda SK (1993) Application of a new model for fatigue threshold in a structural st eel weldment. Eng Fract Mech 45:463–477. Braun M, Mayer E, Kryukov I, et al (2021) Fatigue strength of PBF -LB/M and wrought 316L stainless steel: effect of post-treatment and cyclic mean stress. Fatigue Fract Eng Mater Struct. Carneiro L, Jalalahmadi B, Ashtekar A, Jiang Y (2019) Cyclic deformation and fatigue behavior of additively manufactured 17–4 PH stainless steel. Int J Fatigue 123:22–30. Chapetti MD (2011) A simple model to predict the very high cycle fatigue resistance of steels. Int J Fatigue 33:833–841. Chern AH, Nandwana P, Yuan T, et al (2019) A review on the fatigue behavior of Ti-6Al-4V fabricated by electron beam melting additive manufacturing. Int J Fatigue 119:173–184. El Haddad MH, Smith KN, Topper TH (1979a) Fatigue Crack Propagation of Short Cracks. J Eng Mater Technol 101:42. El Haddad MH, Topper TH, Smith KN (1979b) Prediction of non propagating cracks. Eng Fract Mech 11:573–584. Herold H, Streitenberger M, Zinke M, et al (2000) An experimental and theoretical approach for an estimation of DeltaKth. Fat igue Fract Eng Mater Struct 23:805–812. Kan WH, Nadot Y, Foley M, et al (2019) Factors that af fect the properties of additively-manufactured AlSi10Mg: Porosity versus microstructure. Addit Manuf 29:100805. Lewandowski JJ, Seifi M (2016) Metal Additive Manufacturing: A Review of Mechanical Properties. Annu Rev Mater Res 46:151–186. Li P, Warner DH, Fatemi A, Phan N (2016) Critical assessment of the fatigue performance of additively manufactured Ti-6Al-4V and perspective for future research. Int J Fatigue 85:130–143. Llorca J, Sanchez-Galvez V (1987) Fatigue threshold determination in high strength cold drawn eutectoid steel wires. Eng Fract Mech 26:869–882