How do you model thermal behavior in metal additive manufacturing processes like LPBF?

Laser Powder Bed Fusion (LPBF) thermal modeling challenges: extreme heating/cooling rates (10⁵-10⁷ K/s), small melt pool (~100μm), multiple scales (μm powder to cm part), phase changes (melting, solidification, solid-state), and process-microstructure-property linkages. Modeling approaches: Analytical models (Rosenthal solution for moving point source provides initial estimates); Part-scale FEM (coarse mesh, layer-by-layer activation, homogenized properties, 'inherent strain' for distortion); Meso-scale (resolved scan tracks, temperature-dependent properties, latent heat via enthalpy method); Micro-scale (powder-scale discrete element + CFD for melt pool dynamics, Marangoni convection, keyholing). Key phenomena: surface heat loss via convection (h~10-20 W/m²-K in inert gas) and radiation, thermal cycling causing residual stress, re-melting of previous layers affecting microstructure. Calibration against thermocouple data, melt pool dimensions from high-speed imaging, and residual stress measurements. Used for process parameter optimization, support structure design, and distortion compensation.