The complexity of additive manufacturing (AM) methods, such as powder bed fusion - laser beam (PBF-LB), demands a depth of understanding to ensure robust and predictable AM production. The resolution of this problem requires modeling and simulation efforts on different length scales in an experimental validation framework, where the simulation results are compared with the corresponding experimental results. The general modeling approach is to develop a high-fidelity modeling concept on a mesoscale that can predict a homogenized local stress response, interpreted as a local inherent strain at different geometrical locations. In the next step, these local inherent values are mapped onto a grid that covers the entire component and the distributed inherent strain analysis can be resolved. A key part of the development of the mesoscale model is the material model. Inspired by Noll et al [1], phase transformations, characterized by mass fractions of powder, melt and solid phases, are modeled as viscous dissipative variables. Driven by thermodynamically motivated stresses, the mass fractions are evolving along with the constraints of mass conservation and the irreversible mass fraction of the powder phase. Applied loading scenarios lead to the evolution of phases and strains due to the response of elastic powder, viscoelastic melt, and elastic-plastic solid phase. The material model is implemented as a meso-scale process model with a moving heat source modeled as a volumetric heat flux. Melt pool monitoring and temperature measurements are utilized for calibration of parameters for the Goldak double ellipsoidal heat source model [2]. Experiments such as synchrotron and microstucture characterization are used for model validation related to the prediction of meltpool size and shape, as well as the residual stress state on the meso scale. REFERENCES [1] I. Noll, T. Bartel and A. Menzel, "A computational phase transformation model for selective laser melting processes", Computational Mechanics 66:1321–1342 (2020). [2] J. Goldak, A. Chakravarti, and M. Bibby, A new finite element model for welding heat sources. Metallurgical Transactions B, 15:299-305 (1984)