PSI - Issue 71

Ravi Prakash et al. / Procedia Structural Integrity 71 (2025) 325–332

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build directions, respectively. There was a cooling time of 24 seconds after the deposition of each track had been adopted.

Fig. 1. Geometric configuration of the build/substrate system used for thermo-mechanical modelling.

Table 1. Process parameters utilized for printing the part onto the substrate across various cases. Case Power-P (W) Scan velocity-v (mm/s) Track count (per plane) Track width (mm) Layer height (mm)

Laser beam spot diameter (mm)

Heat input -P/v (J/mm)

I

500 500

5

2 2 2 2

2 2 2 2

0.9 0.9 0.9 0.9

2 2 2 2

100

II

20

25

III IV

2000 2000

5

400 100

20

Fig. 2. Laser scanning pattern for (a) odd-numbered layers and (b) even-numbered layers

3. Materials and methodology Several crucial presumptions were established in order to faithfully mimic the LPBF process during thermal modelling and mechanical analysis. The model's surface was considered flat and finite, with both the build and substrate materials treated as uniform and isotropic. The laser heat source's highly restricted and collimated beam formed a narrow melting channel in the scan direction. In order to record a sharp temperature gradient, an adaptive meshing with a DC3D8-type element was used along the whole geometry. Accordingly, as can be seen in Fig. 3, a coarse mesh (2 × 2 mm²) with adaptive meshing was utilized for the substrate portion, and 0.5 × 0.5 × 0.5 mm³ of fine mesh was placed over the build part, which is in close proximity to the laser. Thermal boundary conditions were established to account for heat losses through convection, radiation and conduction. However, the model did not include the effects of vaporization and changes in elemental composition. The density of the material (Ti-alloy) was assumed to remain constant in both its solid and liquid states, with a coefficient of convective and radiative heat transfer as 25 W/m²/℃ and 0.6, respectively, applied to its surfaces (Kumar & Nagamani Jaya, 2023). The non -linear heat conduction equation (Kumar et al., 2024) based on Fourier analysis in three dimensions was employed to calculate the time-temperature history across the entire solution domain given by Eq. 1. ( )+ ( )+ ( )+ℎ = ( − ) (1)