Background of the Stress-Strain Microprobe® (SSM®) Technology and Its Haggag Test Method (HTM)
Haggag, F.M., "Background of the Stress-Strain Microprobe® (SSM®) Technology and its Haggag Test Method (HTM) known as Automated Ball Indentation (ABI®) Technique," Appendix A, ABI® Services LLC, 2018.
This comprehensive background document covers the complete history and technical basis of the SSM® (Stress-Strain Microprobe®) technology and its Haggag Test Method (HTM), also known as the Automated Ball Indentation (ABI®) technique.
The document establishes the technology's timeline: commercial laboratory equipment available since 1991, the portable/in-situ version receiving the 1996 R&D 100 Award (considered by many researchers as the Nobel Prize of Applied Technology), and the miniature SSM® system introduced in 1999 for enhanced field portability. In 2008, the SSM® technology received the New Pipeline Technology Award (Advanced Technology Category) from Energy TV at the International Pipeline Exposition in Calgary.
The technical core of the document explains the HTM test procedure: progressive indentation with intermediate partial unloadings using a tungsten carbide spherical indenter, with indentation force-depth data collected continuously using a 16-bit data acquisition system. The document details the ultra-precision instrumentation — including a spring-loaded LVDT with repeatability of 0.000004 inch — that enables ABI®'s high accuracy.
Critically, the document presents the precision data from the six-laboratory interlaboratory study (PRCI L52280): across six independent laboratories, the ABI-measured yield strength has a between-laboratory reproducibility coefficient of variation (CV%R) of 1.7%, and the ABI-estimated ultimate strength a CV%R of 2.3%, with progressively larger values for the strength coefficient (3.4%), strain-hardening exponent (6.7%), and uniform ductility (7.8%). These low coefficients of variation for the primary strength properties demonstrate that ABI® results are highly repeatable across operators, laboratories, and instruments.
The document also covers applications beyond pipelines, including automotive frame testing where ABI® measured yield strengths that exceeded specifications — a safety concern because vehicle frames must collapse as designed in head-on collisions to protect occupants.