The Memorandum discusses the current situation on the inclusion of fracture-toughness testing requirements in specifications for high-strength steels used for military applications. The Memorandum was prepared at the request of The Technical Cooperation Program (TTCP), and contains information from Canadian and British members of that program, as well as U.S. information. Military applications discussed include missile motor cases, aircraft landing gear, gun tubes, armor plate, and hydrofoils. (Author).

The yield strength range for steels from 180 to 210 ksi is currently covered by four weldable alloys of the following nominal chemical analysis: 18%Ni-8%Co-3%Mo maraging steel, 12%Ni-5%Cr-3%Mo maraging steel, 9%Ni-4%Co-0.20%C quenched and tempered (Q and T) steel, and 10%Ni-8%Co-2%Cr-1%Mo-0.10%C Q and T steel. Broad ranges of fracture resistance have been reported for these materials based on various fracture tests, and this report presents information for material selection and design guidance by providing an analysis of the interactions between the metallurgical and mechanical parameters that contribute to the fracture resistance of plate products. Definitions of the interaction between the metallurgical and the mechanical aspects are developed with the use of the Dynamic Tear (DT) test and the Ratio Analysis Diagram (RAD). (Author).