Nondestructive Monitoring of Structural Materials Using Automated Ball Indentation (ABI®) Technique

This is the landmark independent validation paper for ABI® technology, published in the peer-reviewed journal Nuclear Engineering and Design by Professor K.L. Murty of North Carolina State University and Dr. M.D. Mathew of the Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam, India.

The paper demonstrates ABI® performance across multiple nuclear structural material classes: low-alloy ferritic A36 steel under varying levels of cold-work (used as an analog for radiation hardening and embrittlement), A533B pressure vessel steel weldments from the ORNL Heavy-Section Steel Irradiation series (characterizing base metal / heat-affected zone / weld metal property gradients), cast CF-8 austenitic stainless steel under long-term thermal aging at 673 K, nickel-base superalloy Alloy 625 across aging temperatures from 873 K to 1173 K, and Zircaloy cladding tubes characterized for mechanical anisotropy along the radial, hoop, and axial directions.

The breadth of materials and metallurgical conditions tested — combined with the independence of the researchers (neither NC State nor IGCAR had any commercial interest in ABI®) — makes this the most widely cited multi-material proof of concept for ABI® technology. The paper demonstrated that ABI® accuracy is general across diverse engineering metals.

The study also demonstrated ABI®'s ability to characterize mechanical anisotropy in Zircaloy cladding — a property critical to nuclear fuel performance that cannot be assessed by standard tensile testing of small tube specimens. ABI-derived anisotropy parameters were shown to be in agreement with previously published data from conventional internal pressurization tests.