PSI - Issue 17

Radomila Konečná et al. / Procedia Structural Integrity 17 (2019) 138 – 145 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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The fatigue results for the as-built horizontal double notched specimens of SLM Inconel 718 by Witkin et al. (2018) are compared to the fatigue results of the as-built Type A+ and Type A- miniature specimens in Fig. 8. The three sets of data share the slope of the S/N curves but are slightly shifted one with respect to the others. In this case, however, the fatigue strength of about 150 MPa for the doubly-notched specimens is very close to the response of the Type A- miniature specimen (the specimen with the down-skin notch) while the Type A+ specimen data are unequivocally better.

Fig. 7. Comparison of double notched tensile plate of Witkin et al. (2018) and the two miniature bending specimens used here.

Fig. 8 Notched fatigue behavior of horizontal double notched plates vs. Type A+ and Type A- miniature specimens.

4. Conclusions This study was aimed at the experimental investigation of fatigue notch sensitivity of as-built SLM Inconel 718 in the presence of different surface orientations with respect to the build direction using the test methodology recently introduced by Nicoletto (2017). The main conclusions are the following: - The test methodology using miniature fatigue specimens efficiently provided original insight into the dependence of the fatigue behavior on the directionality of the notch fabrication by SLM processing. - Of the four directional specimens investigated and shown in Fig. 2, Type A- showed the worst notch fatigue performance, Type B the best and Type C and Type A+ intermediate notch fatigue performances.