PSI - Issue 18

5

Dan Ioan Stoia et al. / Procedia Structural Integrity 18 (2019) 163–169 Dan Ioan Stoia, Liviu, Marsavina/ Structural Integrity Procedia 00 (2019) 000–000

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In Fig. 3 (a) and (b), the relative errors in XY plane are presented. Both the error values and the tendency according to the orientation angle are similar. However, due to the physical size of the beam (beam spot) and the real curing zone that the laser is generating on powder bed, the smaller part’s dimension, the greater error is. The relative error from Fig. 3 (c) is considerable higher and corresponds to the Z direction (direction of growing). Beside the larger error values, a clear linear tendency of error growing with orientation angle can be observed. The density was computed using the weight of individual samples and their volumes computed based on linear dimensions. A clear tendency (Fig. 3 d) of decreasing the parts densities when the orientation angle increases can be observed. Taking into account that sinterization process was conducted on X and Y directions alternatively in every layer, a reasonable explanation can be found in overlapping at 0 deg. of the direction of powder deposition and the part’s longitudinal direction. 3.2. Mechanical properties Force-displacement curves represented up to the breaking point are presented in Fig. 4 and 5, for non-notch and notch samples respectively. The bending curves of non-notched samples indicate differences in the elastic zones and also different fracture forces and breaking energies. The samples oriented at 0 angle exhibits higher E modulus and higher maximum force. Similar, in the case of notched samples, the larger fracture force was recorded for 0 angle. In the table 2, the properties obtained for E bend , σ bend , and K IC are presented as average values with standard deviations for all samples and according to the orientation angle.

(a) (c) Fig. 4. Force displacement curves of non-notched samples: a) 0 deg. orientation; b) 45 deg. orientation; c) 90 deg. orientation (b)

(a) (c) Fig. 5. Force displacement curves of notched samples: a) 0 deg. orientation; b) 45 deg. orientation; c) 90 deg. orientation (b)