Use of Automated Ball Indentation Testing to Measure Flow Properties and Estimate Fracture Toughness in Metallic Materials

This is the seminal ASTM Special Technical Publication paper that formally introduced the automated, instrumented ABI® system to the materials testing community. Published in 1990, it presents the complete methodology for extracting yield strength, flow curve, and fracture toughness estimates from cyclic ball indentation load-displacement data.

The paper was validated against conventional tensile tests on A212 pressure vessel steel — a material of direct relevance to the nuclear reactor safety community that constituted ASTM's primary audience for this work. The presentation in an ASTM STP meant the work had been peer-reviewed by the ASTM Committee E08 (fatigue and fracture) community, lending it the formal documentation often expected in regulated industries.

This paper established the core data analysis framework that all subsequent ABI® work builds upon: the cyclic loading protocol, the contact mechanics derivation of true stress and true plastic strain from ball indentation data, the Meyer's law-based approach to flow curve extraction, and the Modified Critical Strain Model for fracture toughness estimation.

The publication in ASTM STP 1092 — specifically in the volume addressing automation technology for fatigue and fracture testing — positioned ABI® as part of the broader trend toward automated, computer-controlled materials testing that was transforming the field in the early 1990s.