- Ph.D., Welding Engineering, The Ohio State University, 2019
- M.S., Welding Engineering, The Ohio State University, 2017
- B.S., Welding Engineering, The Ohio State University, 2016
- American Welding Society (AWS) D101 Committee on Procedure and Performance Qualification
- AWS B2 Subcommittee on Chromium-Molybdenum Steel Piping
Dr. Stewart specializes in welding engineering, joining and heat-treating processes, metallurgy, failure analysis, non-destructive evaluation, and corrosion. He has extensive experience with a variety of analytical techniques including optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD).
Dr. Stewart also has experience with computational modelling and simulation, specifically finite element analysis (FEA) of heat transfer in welding processes and modelling thermophysical properties of various alloys.
Prior to joining Exponent Dr. Stewart was a Graduate Research Associate at The Ohio State University, completing his Ph.D. in 2019. His doctoral thesis examined the impact of temper bead welding on the tempering response in Grade 22 steel, a 2.25Cr-1Mo steel used in oil & gas piping and nuclear power applications. Temper bead welding is a technique that utilizes heat input from the welding process to temper brittle microstructures that form in the heat-affected zone (HAZ) that would require a post-weld heat treatment (PWHT) to remedy.
Dr. Stewart developed a methodology for quantifying the tempering response in low alloy steels that allowed the hardness distribution in the HAZ to be predicted based on thermal history during the welding process. Additionally, a computational model that can predict thermal histories in the HAZ based on welding process parameters was developed, his model utilized an automated design of experiment (DoE) capability that allowed users to input a range of welding parameters and compare expected hardness distributions for each combination, producing an optimal procedure for the desired outcome.
Dr. Stewart has utilized several welding and weldability techniques throughout his career, including operation of the Gleeble thermal-mechanical simulator, robotic GTAW welding machines, thermocouple instrumentation and data collection, and weldability analysis of Ni-base alloys. In addition, he has experience with a variety of welding processes, including GTAW, GMAW, resistance welding, friction welding, and laser/electron beam welding. He has experience with weld procedure development and qualification for applications in aerospace, oil & gas, and nuclear power generation.