Master of Science (M.S.), University of Dayton, 2020, Electro-Optics

This work explores new capabilities of recently emerged adaptive multi-beam laser power sources to optimally shape laser power spatial distribution at powder material during metallic laser powder bed fusion additive manufacturing. Conventional laser additive manufacturing (LAM) systems use a highly localized laser beam for powder material melting resulting in strong temperature gradients inside the heat affected zone (HAZ) leading to formation of columnar material grain structure having highly anisotropic mechanical properties. Beam shaping with multi-beam laser power source provides opportunities for on demand and location-specific altering grain structure from columnar to equiaxed resulting in more isotropic mechanical properties of LAM fabricated parts. In this work we perform numerical simulations of theLAM process using a reduced complexity analytical heat transfer solution in order to optimize multi-beam configurations leading to the desired transitioning from columnar to equiaxed grain morphology. The beam shaping optimization was performed using a stochastic parallel gradient descent optimization of the introduced performance metrics. The results demonstrate the possibility to significantly increase the fraction of equiaxed grains in the solidified powder material using optimal positioning and laser power control of multiple laser focal spots during LAM.

Committee: Mikhail Vorontsov (Committee Chair); Chenlong Zhao (Committee Member); Victor Kulikov (Committee Member) Subjects: Optics