{"690953":{"#nid":"690953","#data":{"type":"event","title":"PhD Defense by Ruoqi (Rosie) Gao","body":[{"value":"\u003Cp\u003E\u003Cstrong\u003ERuoqi (Rosie) Gao\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EAdvisor: Hamid Garmestani\u003C\/p\u003E\u003Cp\u003EWill defend a doctoral dissertation entitled,\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EAn Integrated Process\u2013Texture\u2013Property\u2013Residual Stress Modeling Framework for Laser Powder Bed Fusion of Ti-6Al-4V, with Experimental Microstructural Characterization\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EOn\u003C\/p\u003E\u003Cp\u003EWednesday, July 8th, 2026 at 9:00 AM, EST\u003C\/p\u003E\u003Cp\u003EAt\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EPrice Gilbert Memorial Library, Room 4222\u0026nbsp;(Dissertation Defense Room)\u003C\/p\u003E\u003Cp\u003Eand virtually via Zoom:\u003C\/p\u003E\u003Cp\u003EZoom Meeting ID: 825 911 3860\u003C\/p\u003E\u003Cp\u003EPasscode: 662031\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EAbstract\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003ELaser powder bed fusion (LPBF) enables near-net-shape manufacture of geometrically complex Ti-6Al-4V components, but its steep thermal gradients and rapid, cyclic solidification generate non-equilibrium microstructures, strong crystallographic texture, and large residual stresses that limit dimensional accuracy and structural reliability. Residual-stress models that resolve crystallographic anisotropy are computationally costly, while the fast analytical models suited to surveying process space typically assume isotropic elasticity and isotropic (von Mises) yield \u2014 neglecting the elastic and plastic anisotropy that process-induced texture imparts. This dissertation addresses this gap through complementary modeling and experimental studies of LPBF Ti-6Al-4V, unified by the process\u2013structure\u2013property\u2013residual stress chain.\u003C\/p\u003E\u003Cp\u003EThe modeling work assembles a computationally efficient, physics-based forward chain. A semi-analytical thermal model represents the laser as a moving single-ellipsoidal volumetric source, linearizes the temperature-dependent heat equation through the Kirchhoff transformation, and incorporates latent heat to predict the steady-state melt-pool geometry, reproducing width and depth across ten experimental single-track cases to within 3.3% and 2.8% on average. The predicted thermal field drives a two-phase texture model that generates the prior-\u03b2 solidification texture by competitive columnar growth, applies the inter-layer scan rotation, and transforms to \u03b1\u2032 through the twelve Burgers variants, reproducing the characteristic\u0026nbsp;\u27e8100\u27e9\u2225BD prior-\u03b2 fiber and the scattered \u03b1\u2032 texture against two datasets. The reconstructed textures are homogenized by elastic and visco-plastic self-consistent schemes into effective orthotropic elastic constants and Hill yield-stress ratios, which show the build direction to be both the stiffest (E\u2083\/E\u2081 \u2248 1.1) and the strongest. Incorporating these texture-derived properties into an analytical residual-stress model predicts that texture does not simply scale residual stress but redistributes it, lowering the transverse and raising the along-scan component.\u003C\/p\u003E\u003Cp\u003EThe experimental work characterizes as-built LPBF Ti-6Al-4V across a deliberate scan-speed and hatch-spacing process window, combining electron backscatter diffraction, porosity analysis, microhardness, and depth-resolved residual-stress measurement on common material. Increasing scan speed monotonically refines the prior-\u03b2 grain structure and weakens texture, while lath morphology and retained \u03b2 fraction vary non-monotonically and lack-of-fusion porosity emerges at the highest speed. The dataset documents how these features co-evolve across the window and frames the open questions a definitive microstructure\u2013residual-stress linkage must resolve.\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ECommittee\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EProf. Hamid Garmestani - School of Materials Science and Engineering\u003C\/p\u003E\u003Cp\u003EProf. Preet Singh - School of Materials Science and Engineering\u003C\/p\u003E\u003Cp\u003EProf. Aaron Stebner - School of Materials Science and Engineering\u003C\/p\u003E\u003Cp\u003EProf. Steven Y. Liang - School of Mechanical Engineering\u003C\/p\u003E\u003Cp\u003EProf. Sa\u00efd Ahzi - Faculty of Physics and Engineering, \u003Cem\u003EUniversit\u00e9 de Strasbourg\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E","summary":"","format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003E\u003Cstrong\u003EAn Integrated Process\u2013Texture\u2013Property\u2013Residual Stress Modeling Framework for Laser Powder Bed Fusion of Ti-6Al-4V, with Experimental Microstructural Characterization\u003C\/strong\u003E\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"An Integrated Process\u2013Texture\u2013Property\u2013Residual Stress Modeling Framework for Laser Powder Bed Fusion of Ti-6Al-4V, with Experimental Microstructural Characterization"}],"uid":"27707","created_gmt":"2026-06-26 18:53:00","changed_gmt":"2026-06-26 18:53:34","author":"Tatianna Richardson","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2026-07-08T09:00:00-04:00","event_time_end":"2026-07-08T11:00:00-04:00","event_time_end_last":"2026-07-08T11:00:00-04:00","gmt_time_start":"2026-07-08 13:00:00","gmt_time_end":"2026-07-08 15:00:00","gmt_time_end_last":"2026-07-08 15:00:00","rrule":null,"timezone":"America\/New_York"},"location":"Price Gilbert Memorial Library, Room 4222 (Dissertation Defense Room) ","extras":[],"groups":[{"id":"221981","name":"Graduate Studies"}],"categories":[],"keywords":[{"id":"100811","name":"Phd Defense"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[{"id":"1788","name":"Other\/Miscellaneous"}],"invited_audience":[{"id":"78771","name":"Public"}],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[],"email":[],"slides":[],"orientation":[],"userdata":""}}}