PSI - Issue 14

Anigani Sudarshan Reddy et al. / Procedia Structural Integrity 14 (2019) 449–466 Author name / Structural Integrity Procedia 00 (2018) 000–000

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the case of all the small scale test samples were well within the gauge sections as shown in the insert in Figure 13 (a i) in the as printed and heat treated condition. The difference (  ) between the small scale test specimen and the regular test specimen (small scale – regular) is tabulated for all the three properties, 0.2% YS, UTS and %elongation, as listed in Table 7. In the Table 7, the magnitude of “minus (-)” indicates that the small scale tested values are lower than the regular test specimens, while “plus (+)” refers to a higher value in the small scale test data as compared to the regular specimen data. The 0.2% YS and UTS of all the monolithic DMLS samples are having a Δ of less than 30 MPa between the small scale and regular specimens in the as printed condition. Except for Ti6Al4V and UTS of IN718, where a  of 90-100 MPa less is observed, which may be due to residual stress built up is more or due to stresses induced in wire cutting of small scale specimens. After heat treatment all the monolithic DMLS samples showed Δ of less than 30 MPa between the small scale and regular specimens which is an indication that the residual stresses induced in the as printed are relieved. In addition, microstructure tends to dictate properties after heat treatment. The %elongation of all the monolithic DMLS samples are more or less the same between the small scale and regular test specimens. The standard deviations of small scale specimens and regular specimens are well within the 40 MPa for 0.2% YS and UTS and 1 2% for %elongation in both the as printed and heat treated condition. The Δ of small scale and regular specimens are well within the standard deviations, which establishes that small scale testing is a viable test method for additive manufacturing.

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Fig. 12. Schematic showing comparison of Load Vs displacement curves of DMLS alloys both in the as printed and heat treated condition (along the build direction) (a) IN718, (b) CoCrMo, (c) Maraging steel (d) SS316L and (e)Ti6Al4V