Associate Professor, Department of Mechanical Engineering, Northwestern University
Two of the objectives of manufacturing research conducted at the speaker’s group are 1) to better understand the mechanics of deformation/failure in the forming process and therefore design a forming process that maximizes material usage, and 2) to better detect/understand process variations and therefore have a systematic approach to increase the robustness of a process. These two objectives ultimately require a creation of an integrated system.
In this talk, the mechanics and frictional behavior in micro-forming of metallic parts will be presented first. Microparts are commonly defined as parts or structures with at least two dimensions in the sub-millimeter range which are used extensively in electronics and micromechanical products. We find that microstructure affects the final deformed pin geometry and frictional force. When an extruded pin has only several grains across its dimension, the pin tends to bend in an arbitrary direction. Meanwhile, the frictional force experienced a lower friction coefficient when size reduces.
At the macro-forming case, predictions of wrinkling and tearing failure in sheet metal forming are given through stress-based failure criteria. The severity indices will then be used in a design process which considers uncertainties in the stamping process and inherited variations from prior processes. To effectively and efficiently achieve goals of this digital design analysis, a weighted-three-point method was developed to assess the normal and variances of a stamping process. Once the design was in place, an on-line draw-in sensor was developed to actively monitor the process in addition to conventional force sensors. A closed-loop control system can then be in-placed to achieve a better forming potential and forming consistency.
Depending on the general interest of audience, each of the above mentioned aspects will either be briefly mentioned or be discussed in details.
Professor Jian Cao has been with Northwestern University since she received her Ph.D. degree in Mechanical Engineering from M.I.T. in 1995. During her tenure at Northwestern, she took a one-year leave at General Motors in FY1996 and a two-year leave at the National Science Foundation in FY2004 and 2005 as a program director. Prof. Cao's primary interests are in the mechanics analysis and design of macro/micro metal forming and composite sheet forming processes. Recently, she initiated the World Technology Evaluation Study on Micro-manufacturing, which was co-funded by NSF, ONR, DOE, and NIST. Prof. Cao is a recipient of the General Electric Foundation Professorship, Alcoa Foundation Award, National Science Foundation CAREER award, Society of Automotive Engineers (SAE) Ralph R. Teetor Educational Award, Society of Manufacturing Engineers (SME) Outstanding Young Manufacturing Engineer Award and the Young Investigator Award from the Japan-US Flexible Automation. She is an associate editor for the ASME Journal of Manufacturing Science and Engineering and the ASME Journal of Applied Mechanics, a member of the executive committee of ASME Manufacturing Engineering Division, and an executive board member of SME North America Manufacturing Research Institute.