Mechanical Engineering Graduate Seminar Series: Dr. Brad Kinsey - Manipulating Martensite Transformation in Stainless Steel during Incremental Forming

Abstract: Incremental forming (IF) is a rapid prototyping method for sheet metal components where point tools contact the workpiece and deform the material locally into the desired geometry. The flexibility of IF can be used for in-situ mechanical properties alteration, e.g., by controlling deformation-induced martensite phase transformation of austenitic stainless steels. This provides a means to create a heterogeneous material, e.g., patient specific trauma fixation hardware, which needs localized strength at screw locations and overall weight reductions. In this research, several modifications to IF have been implemented to manipulate the martensite transformation of SS304, including double sided (DSIF), superposing a tensile pre-stress on the material during forming, and forming the workpiece into an elastomer die. In addition, the stress triaxiality, equivalent plastic strain, and temperature have been altered in the IF process, all of which are known to affect the martensite transformation kinetics. Numerical simulations have been conducted to understand the effect of these process parameters on the final part geometry (accounting for springback) and plastic strain. The test geometry used in these experiments is a truncated square pyramid, with the martensite measured using magnetic induction. The martensite transformation in the formed wall of the workpiece was varied from <10%, for a traditional IF process, to >90% by implementing a reforming tool path at the lowest achievable temperature. This demonstrates the potential for a paradigm shift in the design of formed components to create functionally graded materials using IF.

Bio: Brad Kinsey is the Associate Dean for Research in the College of Engineering and Physical Sciences (CEPS) and a Professor in the Mechanical Engineering Department at the University of New Hampshire.  He is also the Project Director of NH BioMade (a $20M/5-year NSF project) and the Director of the UNH Center for Advanced Materials and Manufacturing Innovations (a collection of 25 faculty members across CEPS).  He has published over 175 peer-reviewed articles primarily on the mechanics, materials, and manufacturing innovations of deformation processes. 

Prof. Kinsey received his Bachelor’s degree from the University of Michigan in 1992 and his Master’s and Doctoral degrees from Northwestern University in 1998 and 2001 respectively, all in Mechanical Engineering.  His awards include Fellow status in the American Society of Mechanical Engineers, Fellow status in the Society of Manufacturing Engineers, Associate Member status in CIRP (International Institution for Production Engineering Research), a CAREER Award from US National Science Foundation, the Ralph R. Teetor Award from the Society of Automotive Engineers, and the UNH Assistant Professor of the Year Award.  In 2013, he served as the Department of Energy Representative to the Advanced Manufacturing National Program Office, which coordinates the Manufacturing USA network.