This volume contains the proceedings of the USA-Japan Joint Seminar on "Fracture Mechanics of Ductile and Tough Materials and Its Applications to Energy Related Structures." The seminar was supported jointly by the National Science Foundation of the United States and the Japan Society for the Promotion of Sciences. The seminar was held from November 12th to 16th, 1979, at Hayama, Japan, a picturesque resort town by the beach of Sagami Bay facing Mt. Fugi. The safety and integrity of the engineering structures for energy explora tion, energy production, and energy transportation are of utmost...