CAREER: Thermomechanical Response and Fatigue Performance of Surface Layers Engineered by Finish Machining: In-situ Characterization and Digital Process Twin

Project Summary Finishing operations are crucial in modern advanced manufacturing, as they impart functionally relevant surface integrity metrics (e.g., residual stresses and surface finish) and component quality characteristics such as fatigue life. However, a fundamental knowledge gap of the response of metals to finishing-specific thermo-mechanical loads and associated fatigue life performance has hindered the realization of a ‘Smart Finishing’ paradigm. In order to study the process-specific thermo-mechanical response of advanced engineering materials during finishing operations, as well as grain-scale strain localization during low cycle fatigue testing, the PI recently developed a state-of-the-art in-situ characterization testbed (3 patents pending, >$300k investment). The testbed setup has been demonstrated to achieve more than an order of magnitude improvement in spatial and temporal resolution of optical sub-surface nanometer-scale displacement field measurements. High quality in-situ data will be leveraged for rapid calibration of modular Digital Process Twin (DPT) models of finishing operations using well-established (pre-trained) machine learning algorithms. The PI’s DPT models have been preliminarily validated to accurately predict machining-induced residual stresses, while being 4-5 orders of magnitude faster than currently used (numerical/FEM) models. DPT modules can be combined and re-configured to address a variety of physical domains and length scales, required to predict the impact of dynamic process variables (e.g., progressive tool-wear) on relevant quality metrics (e.g., component fatigue life) for a broad range of material systems. Proposed major aims are: (1) Perform advanced in-situ measurements of finishing-specific material response.; (2) Develop Digital Process Twin models of process-induced quality in finishing operations; (3) Recruit and train a diverse workforce in theory and practice of Smart Finishing.; and (4) Establishment of an academia/industry collaborative working group (future IUCRC consortium) for In-situ Characterization of Process-specific Material Response. Intellectual Merit This CAREER proposal will lay the foundation for a long-term research and education program in process-specific characterization and efficient modeling of fatigue life induced by finishing processes. Using an advanced in-situ experimental technique designed specifically for study of finishing processes and grain-level strain localization during fatigue crack initiation, this research explores the fundamental questions of ‘what is the process-specific thermo-mechanical response of workpiece materials during finishing processes’. In-situ characterized data will be leverage to calibrate models of process-induced surface integrity and associated fatigue life performance. While currently available models are either empirical or brute-force numerical formulations dealing with chip formation mechanics, our efficient and modular Digital Process Twin (DPT) approach specifically considers sub-surface material response. By combining state of the art experimental characterization with an efficient DPT paradigm, this CAREER proposal will lay the groundwork for a fundamental paradigm shift towards “Smart Finishing” with a projected economic impact of hundreds of millions of dollars. To achieve this ambitious goal, the proposed effort leverages strong collaboration with key regional and national manufacturing industry stakeholders, including the Kentucky Association of Manufacturers, two regional Tier 1 suppliers, and four major aerospace OEMs (GE, Rolls Royce, Lockheed Martin, and Pratt & Whitney/Raytheon). Broader Impacts This project will have two major broader impacts: First, this project will broaden participation of women, persons with disabilities and underrepresented minorities through collaboration with the Society of Women Engineers (SWE) to recruit female and underrepresented minority students for the proposed study. An undergraduate and a PhD student will work on this project and participate in mentorships with aerospace industry partners. Second, this project will establish novel infrastructure for research and education. The PI has assembled a strong team of four major aerospace OEMs, as well as key regional manufacturing stakeholders, who will help inform the proposed research and education as an industrial advisory board. Through annual virtual (Zoom/Teams) workshops, short courses and consortium activity, the PI will further refine his CAREER roadmap by systematically identifying and addressing key industry needs for both research (i.e., technical gaps) and education (i.e., workforce/skill gaps) and begin to lay the groundwork for a long-term collaborative IUCRC effort.