This thesis, [3], presents a micromechanically motivated framework for simulating Laser Powder Bed Fusion (PBF-LB), a well-known additive manufacturing (AM) technique used to fabricate metal components, among others. In PBF-LB, a laser selectively melts powder to construct parts layer by layer, offering freedom in terms of geometry, material combinations, and customisation. However, the process involves complex thermomechanical and metallurgical phenomena due to the rapid heating and cooling cycles involved. Overall, these can lead to defects such as residual stresses, warping and porosity. Accurately predicting such defects requires physically grounded models that capture the underlying multiphysics. To address these challenges, the first part of this thesis focuses on developing a thermodynamically consistent, physically based material model founded on minimising the free energy density. This model captures the essential phase transitions that occur in PBF-LB, namely powder melting and re-solidification. It is initially applied to validate its physical accuracy in the small-scale simulation of single melt tracks, [1]. The second part introduces a multiscale simulation strategy that couples the detailed phase transformation model with the inherent strain (IS) method. This is to meet the computational demands of full-part simulations. This approach balances fidelity and efficiency, enabling the simulation of residual stresses and deformations in entire components while maintaining critical physical accuracy, [2]. The proposed framework is implemented in a fully coupled thermomechanical setting using the commercial finite element software Abaqus. By integrating micromechanical insight with scalable numerical methods, this thesis makes a valuable contribution to the simulation of PBF-LB processes, making them more accurate and computationally feasible, and ultimately supporting the development of more reliable and optimised AM components. REFERENCES [1] Noll et al., A computational phase transformation model for selective laser melting processes, Comput. Mech. (2020) 66:1321-1342. doi:10.1007/ s00466-020-01903-4 [2] Noll et al., A micromechanically motivated multiscaleapproach for laser powder bed fusion processes, Addit. Manuf. (2022) 60:10327. doi: 10.1016/j.addma.2022.103277 [3] Noll, I. Thermomechanical Modelling and Simulation of Laser Powder Bed Fusion Processes, Dissertation, TU Dortmund University (2023). doi:0.17877/DE290R-24330