Kenneth James Trigger (1910–2001)
Professor Kenneth James Trigger was born on September 6, 1910 in Carsonville, MI. He married Florence (Vickie) Trigger on December 24, 1939. Professor Trigger received his formal education from Michigan State College graduating with an M.S. in Mechanical Engineering in 1935. After obtaining some teaching and research experience at Michigan State University, Swarthmore College, and Lehigh University, Ken joined the Mechanical Engineering Department of the University of Illinois at Urbana-Champaign, IL in 1938 as an Associate with teaching duties in the Machine Tool and Heat Treatment Laboratories. It was here that Ken developed a strong interest in metal cutting and tool materials—an interest that occupied his entire research career that spanned nearly four decades. After serving as an Assistant Professor during World War II, Ken was promoted to Full Professor in 1945. Until his retirement in 1977, Ken taught both undergraduate and graduate courses in mechanical and thermal processing of metals, tool materials—their treatment and properties, and welding and joining of metals. He served as Head of the Industrial Production Division of the Mechanical Engineering Department from 1951–1976.
It may be noted that many metal cutting researchers consider the decade of the 1950’s as the “Golden Age of Metal Cutting.” For the first time metal cutting was being transformed from an art to a science. Professor Trigger played a significant role in this transformation. This was the period when the discussions by various researchers to a technical paper in the ASME Transactions were as significant (both in length and content) as the original paper itself. The discussers were “Who is Who” in the areas of heat transfer, tribology, and machining. A decade before that, namely, in the 1940’s, Gene Merchant of Cincinnati Milling Company in Cincinnati formulated the mechanics of chip formation process for both orthogonal and oblique machining. Around the same time, Rosenthal of MIT introduced the moving coordinate system and addressed the welding problem analytically as a quasi stationary system using the Fourier partial differential equation (PDE) of heat conduction. Herman Blok of the Netherlands introduced the heat partition function between two bodies in relative motion, and Jaeger from Tasmania, Australia introduced the heat source method for solving a wide range of moving heat source problems. Armed with these powerful tools, Ken Trigger and B. T. Chao of the University of Illinois at Urbana Champaign, Loewen and Shaw of MIT, Hahn of Heald Machine Company in Worcester, MA, and many other researchers addressed the thermal problems involved in metal cutting, namely, the temperature distribution due to shear plane heat source and frictional heat source at the chip-tool interface analytically.
Ken Trigger, in active collaboration with B. T. Chao, had addressed a wide range of thermal problems encountered in metal cutting and conducted pioneering research which is still widely used by researchers both in academia and industry. They investigated the performance of controlled contact cutting tools, a precursor to the built-in chip-breakers or chip groove geometry on tool inserts which is now the industry practice to reduce forces, increase productivity, and facilitate chip breaking. They also conducted fundamental studies on tool wear especially on the crater wear and showed by their thermal analysis that the maximum temperature on the tool occurs not at the tool tip but at some distance away. This is the reason for the crater formation on the rake face of the tool. Their approach was both analytical and experimental. This way the theory formulated can be verified experimentally. Ken also conducted research on the temperature measurements in machining using the chip-tool thermocouple concept originally developed by Shore-Herbert-Gottwein but applied to steel workmaterial machined by cemented tungsten carbide tools. Chao and Trigger were the first to point out that heat partition at the chip-tool interface is not a constant but varies along its length. They solved the problem of variable heat partition using an iterative technique and solved it numerically. A continuous stream of publications flowed with such titles as an analytical evaluation of metal cutting temperatures, temperature distribution at tool-chip and tool-work interface in metal cutting, cutting temperature and metal-cutting phenomena, the significance of the thermal number in metal machining, thermo-physical aspects of metal cutting, and temperature distribution at tool flank surface. Their research was mainly sponsored by the Office of Ordnance Research of the U.S. Army and several industries with several industries supplying tool and workmaterials.
Ken (with von Turkovich) also worked on the high-speed cutting relating metallurgical aspects with the mechanical aspects an approach not common to this field. They conducted machining tests with the workpiece temperature from (80 K) to They showed that cutting behavior is influenced by the purity of the workmaterial. Ken also investigated (with von Turkovich and Ramalingam) the relationship between the dynamic shear stress in the shear zone in cutting and the mechanical properties of the workmaterial. Ken published some 30 technical papers mainly in the Transactions of ASME and several articles in handbooks.
Professor Trigger was very active in the American Society of Mechanical Engineers during his entire professional career. He presented an award winning paper to the ASME Student Branch competition in 1933 on the use of alcohol-gasoline (gasohol) mixture as an engine fuel. At that time the problem was to utilize surplus corn as a potential fuel. This is still an interesting topic for research and commercialization in the U.S.
Professor Trigger’s numerous awards include the ASME Blackall Machine Tool and Gage Award (with Professor B. T. Chao) in 1957, Society of Manufacturing Engineers (SME) Frederick W. Taylor Research Medal in 1959; ASME Centennial Medallion in 1980; and ASME William T. Ennor Manufacturing Technology Award (with Professor B. T. Chao) in 1992. He was a Fellow of ASME, Society of Manufacturing Engineers (SME) and the American Society for Metals (ASM Int.). He was also a member of several honor technical societies including Sigma Xi, Phi Kappa Phi, Pi Tau Sigma, Tau Beta Pi, and Sigma Tau. In 1988, the Mechanical and Industrial Engineering Department of the University of Illinois named their machining research laboratory as the Chao-Trigger Machining Laboratory.
His many outstanding students and collaborators include, of course, Professor B. T. Chao of the University of Illinois at Urbana-Champaign with whom he had a lasting collaborative relationship, Professor B. F. von Turkovich of the University of Vermont, and Professor S. Ramalingam of the University of Minnesota, followed by Professor J. T. Black of Auburn University, Professor Klaus Weinmann of Michigan Technological University, and Professor B. Klamecki of the University of Minnesota. There were numerous students of Professor Trigger as well as current researchers at the University of Illinois, namely, Professors R. DeVor and S. Kapoor who respect him immensely for his seminal contributions. Many researchers in the metal cutting field across the world hold Ken Trigger with great respect for his lasting contributions.
The researchers as well as the practitioners in the metal cutting field across the world will dearly miss Ken Trigger, a golden star in the metal cutting galaxy. Ken was a very unassuming and an extremely friendly person especially to young and new researchers in this field. The first time I met Ken, it was as though we knew each other for eons. One would feel at home in his presence and never realize that you are in the company of a giant in the metal cutting field. We offer our condolences to his dear wife, Florence (Vickie), his children and their families including grandchildren, and great grandchildren. I thank Professor B. T. Chao for providing me with some background information that was distributed at Ken’s memorial service. May the soul of the metal cutter par excellence rest in peace.
