OBJECTIVE: INTEGRATION OF PROCESS MICROSTRUCTURAL EVOLUTION AND MATERIAL PROPERTY THREE LEVELS OF ADVANCED PHYSICAL MODELS AS A HOLISTIC COMPUTATIONAL TOOL FOR SELF-REACTING FSW PROCESS. THE MODEL INPUTS MATERIAL PROCESS PARAMETERS ALONG WITH TOOL GEOMETRY AND OUTPUTS WELD MICROSTRUCTURE AND PERFORMANCE.APPROACH: (1)DEVELOP A MICROSTRUCTURE INTEGRATED MATERIAL CONSTITUTIVE MODEL(2)DEVELOP A HYBRID FLUID DYNAMICS-SOLID MECHANICS PROCESS MODEL (3)COMBINE PRECIPITATE EVOLUTION AND STRUCTURE-PROPERTY RELATIONSHIPS WITH THE PROCESS MODEL TO PREDICT WELD STRENGTH (4)VALIDATE MODELS WITH IN SITU PROCESS MONITORING MULTI-SCALE WELD CHARACTERIZATION AND MECHANICAL TESTING POTENTIAL IMPACTS:(1)FUNDAMENTALLY TRANSFORM THE FSW WELD PROCESS DEVELOPMENT ROUTE USING PHYSICS BASED MODELS(2)FOUNDATION FOR AN INTEGRATED SOFTWARE WIDELY USABLE BY PROCESS DEVELOPMENT ENGINEERS (3)SIGNIFICANTLY INVIGORATE APPLICATION OF INTEGRATED COMPUTATIONAL MATERIAL ENGINEERING (ICME) IN SOLID STATE MANUFACTURING PROCESSES