**6. Conclusions**

In this study, four types of notched specimens were investigated under monotonic testing. Loading path was pure tension and pure torsion. In addition, the specimen without notches was investigated by a tensile test. The specimens were made from stainless steel 316L, produced by selective laser melting technology in the "as printed" state. A DIC measurement was used to gather data during testing and for postprocessing.

The main insights can be listed as:


Regarding the comparison of experimental and FEM analysis results under torsion, it was found that the FEM-Mises and FEM-Hill behaved basically identically within the whole examined twist range, capturing the experimental response well, mainly in the nonlinear part. This implies that the reduction of tensile yield strength in the printing direction in the FEM-Hill did not have the influence on the material response under torsional loading in this case. Nevertheless, further studies are needed to fully capture, understand, and address the torsional behavior and printing direction influence on the

response during the torsional loading. The nonlinear isotropic hardening model with Hill yield condition gives acceptable results under given multiaxial stress states. Under monotonic loading, the nonlinear isotropic hardening model is equivalent to Chaboche kinematic hardening model with two back-stress parts when the second back-stress part is linear. Therefore, a good correlation can also be expected for the Chaboche model (in monotonic loading cases).

It should also be noted that the vertically printed specimens used in this study were not heat treated in any way, such as annealing to remove internal stress. This can also affect the results, of course, especially in the case of horizontally printed specimens. However, to maintain a high yield stress of the material, it is advisable to choose a gentle heat treatment that preserves the fine-grained microstructure of the material. The following study deals with the comparison of experiments on notched specimens in the "as printed" state and is finally modified by machining. Attention is paid to the adherence of the specimen geometry and surface roughness [32]. In the field of numerical modeling, numerical procedures capturing ductile failure on "as printed" specimens and comparison with conventionally produced specimens with the inclusion of small punch tests are used [33].

**Author Contributions:** Conceptualization, M.K., M.P., and R.H.; methodology, R.H.; software, D.K.; validation, F.F., R.H., and D.K.; formal analysis, D.K.; investigation, M.K., R.H., M.P., L.K., F.F., and D.K.; data curation, R.H. and F.F.; writing—original draft preparation, M.K., L.K., R.K., and D.K.; writing—review and editing, R.H.; visualization, J.K.; supervision, R.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by The Ministry of Education, Youth and Sports from the Specific Research Project (SP2020/23), by the Czech Science Foundation (GACR), grant No. 19-03282S, by The Technology Agency of the Czech Republic, project No. TN01000024, and has been done in connection with the DMS project reg. no. CZ.02.1.01/0.0/17\_049/0008407, financed by Structural Funds of the European Union.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author. The data are not publicly available due to: All data are presented in the form of graphs in this article.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

#### **References**


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