PSI - Issue 34

J. Gil et al. / Procedia Structural Integrity 34 (2021) 6–12

10

J. Gil et al. / Structural Integrity Procedia 00 (2019) 000–000

5

Table 1. Process parameters of the prism and benchmark bridge.

Component

Laser

Layer

Scan

Laser

Hatch

speed (mm s − 1 )

power (W)

thickness (mm)

diameter (mm)

space (mm)

Prism

400 200

0.04 0.03

860 950

0.175 0.175

0.095 0.110

Benchmark

Approach #1 Approach #2 Experimental

Approach #1 Approach #2 Experimental

600

600

400

400

σ xx (MPa)

σ yy (MPa)

200

200

10

20

30

40

10

20

30

40

x (mm)

x (mm)

Fig. 4. Longitudinal stress in the prism’s top face.

Fig. 5. Transverse stress in the prism’s top face.

4. Results

4.1. Prism’s residual stresses

In the initial analysis of the prism’s residual stresses, five points were accounted for in the top face of the prism, situated along the y = 0, z = 20 mm line. Both longitudinal ( σ xx ) and transverse ( σ yy ) stresses were analysed, and the results are shown in Figures 4 and 5, respectively. The discrepancy between the approaches is evident: the first ap proach greatly overestimates residual stresses; a second intuitive observation is the symmetry the results display along the y axis at x = 25mm, coordinate at which one of the three symmetry planes is situated. This symmetry is expected, considering the first approaches’ formulation disregards the scanning trajectory, and no orthotropic properties were introduced. The benchmark bridge’s measurements were performed between the 1 . 0 × 5 . 0 × 0 . 5mm ledges situated in the top part of the component; the results are shown in Figures 6-7. Compressive stresses were measured in the experimental case, which is unusual as tensile residual stresses are usually developed in the last deposited layers, due to the rapid cooling they are subjected to while being prevented from thermally shrinking by the already deposited bottom layers. Both approaches were unable to accurately depict the experimental results, with the exception the longitudinal stresses σ xx within the 25 ≤ x ≤ 55mm interval. This may be due to the small ledge’s printing process inducing compressive stresses in the physical component that were not correctly captured in the simulation. 4.2. Benchmark bridge’s residual stresses

4.3. Benchmark bridge’s deflection

The deflection simulation is achieved by relaxing the contact formulation between the nodes along the substrate component interface in a progressive manner. This enables the component to deform according to the residual stress