the Griffith theory by incorporating a plastic work of fracture in addition to the classical surface energy of crack formation. As part of this work, Irwin defined the fundamental concept of a Stress Intensity Factor and the critical plane-strain stress intensity factor (KIC) which is a material property. He was involved in the development of several standards and led several committees for the American Society for Testing and Materials (ASTM). In 1967, Irwin was recruited to Lehigh University as the Boeing University Professor by long-time collaborator Paul C. Paris, the father of modern methods for predicting crack growth and its control in aircraft structures. Irwin served for five years before reaching mandatory retirement age. In his tenure, he continued his collaboration with Paris, and collaborated with, influenced, or assisted many notable individuals in the fracture mechanics community, including: F. Erdogan on cracks in thin-walled shell structures; A. A. Wells of the British Welding Institute on characterizing fracture in normally ductile steel structures; F. A. McClintock, Massachusetts Institute of Technology and John W. Hutchinson, Harvard University, on the development of fracture mechanics procedures in the presence of substantial ductility; James R. Rice, Harvard University, on developing the J integral approach for characterizing the onset of crack growth in ductile materials; L. B. Freund, Brown University, and M. F. Kanninen, Southwest Research Institute, on the dynamics of inertial limited crack propagation and arrest. After retiring from Lehigh University in 1972, Irwin joined the faculty of the University of Maryland, College Park where he worked in the field of dynamic fracture, specifically concerned with crack arrest and the implications in a loss-of-coolant accident in a nuclear power plant. Memberships and honours Irwin was a member of the America National Academy of Engineering and a Foreign Member of the Royal Society of London. Additionally, he received the following honours:- 1946 - Naval Distinguished Civilian Service Award 1947 - Knox College Alumni Achievement Award 1959 - ASTM Charles B. Dudley Medal 1960 - RESA Award for Applied Research 1961 - Ford Foundation Visiting Professorship, University of Illinois 1966 - ASTM Award of Merit 1966 - American Society of Mechanical Engineers (ASME) Thurston Lecture 1967 - Fellow, ASTM 1969 - University of Illinois Engineering Achievement Award 1969 - U. S. Navy Conrad Award 1969 - Alumni Achievement Award, University of Illinois 1973 - SESA Murray Lectureship Award 1974 - Lehigh University Academic Leadership Award 1974 -