张俊  (教授)

应赵万华教授、张俊副教授邀请，美国北卡罗来纳大学夏洛特分校（UNCC）机械系副系主任、ASME-Journal of Manufacturing Science and Engineering副主编Tony Schmitz教授和Christine Schmitz编辑顾问将于6月14日至6月17日来访我校交流。来访期间将做系列学术讲座，欢迎感兴趣的老师和学生积极参加。报告安排如下：

 

 

Tony Schmitz biography:

Tony Schmitz received his BS in Mechanical Engineering from Temple University in 1993, his MS in Mechanical Engineering from the University of Florida in 1996, and his PhD in Mechanical Engineering from the University of Florida in 1999. Schmitz completed a post-doctoral appointment at the National Institute of Standards and Technology (NIST) and was then employed as a Mechanical Engineer from 1999-2002. During this time, he was also a lecturer at Johns Hopkins University. Schmitz accepted an appointment in the University of Florida’s Department of Mechanical and Aerospace Engineering (UF MAE) in 2002 and joined the Mechanical Engineering and Engineering Science Department at the University of North Carolina at Charlotte in 2011.

 

His professional recognitions include: UNC Charlotte Lee College of Engineering 2013 Undergraduate Award in Teaching Excellence, 2012 Temple University Alumni Fellow, 2011 Sports Emmy Award (NBC Learn) for the Science of NFL Football video series, 2010 North American Manufacturing Research Institute/Society of Manufacturing Engineers (SME) Outstanding Paper, 2009 UF MAE Teacher of the Year, 2005 SME Outstanding Young Manufacturing Engineer award, 2004 Journal of Tribology Best Paper Award, 2003 Office of Naval Research Young Investigator Award, 2003 National Science Foundation CAREER Award, 1999 Measurement Science and Technology Highly Commended Article, 1999 National Research Council Postdoctoral Research Associateship (NIST), 1999 Temple University Gallery of Success Inductee, 1998 Department of Energy/National Academy of Engineering Integrated Manufacturing Predoctoral Fellowship, and 1994 National Science Foundation Graduate Traineeship. Schmitz also serves as an associate editor for the ASME Journal of Manufacturing Science and Engineering. He is the author of three textbooks and over 100 journal publications.

 

Christine Schmitz biography:

Christine Schmitz is a communications consultant. She holds an MFA in Creative Writing from the University of Florida and a BA in Journalism from Temple University. Her original work in poetry and short fiction has appeared in national and international literary journals. She worked as an English professor at the University of North Carolina at Charlotte, University of Florida, and Santa Fe College. She was also a writer and editor for a New York Times syndicated daily newspaper.

   

Is all chatter bad?

In this presentation, various bifurcations (i.e., dramatic changes in the system behavior) that can occur in milling operations will be described. After a brief introduction to machining dynamics and simulation, descriptions of periodic sampling of milling signals, Poincaré maps, bifurcation diagrams, and stability maps will be provided. Experimental evidence of period-2, 3, 6, 7, and 15 bifurcations in milling, as well as a comparison with predictions from time domain simulation, will then be shown. Finally, the possibility of machining under these period-n bifurcation conditions (chatter) to produce acceptable parts at reduced cost will be discussed.

 

A comparison of two analytical milling stability analyses with time domain simulation

Milling stability may be predicted using analytical or numerical (time domain) techniques. A comparison of predictions between two different analytical solutions and time domain simulation is presented. A numerical score is developed to characterize the accuracy of the analytical methods relative to time domain simulation (which is considered to provide the correct solution). A summary of the analytical stability solutions is also provided.

 

Productivity progression with tool wear in titanium milling

This study presents experimental results for flank wear width, cutting force, temperature, and surface finish with increasing tool wear in titanium (Ti6Al4V) milling. The variation in these process indicators is presented for repeated trials as the wear progresses from a new tool condition to a significantly worn state. Based on the measured force data, cutting force coefficients are determined using a nonlinear optimization algorithm as the tool wears and these coefficients are combined with the structural dynamics to predict the process stability. The achievable chatter-free material removal rate is then computed for both the new and worn tool conditions. In this way, the variation in productivity is related to the wear state. As expected, the productivity reduces with increase wear.

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