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LSU researcher presents fracture-fatigue entropy method to predict hydrogen embrittlement in pipe steels
Summary
An LSU engineering professor described laboratory work proposing "fracture-fatigue entropy" (FFE) as a material threshold that could predict fatigue failure accelerated by hydrogen charging, and urged further testing to incorporate the metric into design and codes.
Michael Consari, professor of mechanical engineering at Louisiana State University and director of an NSF center on structural integrity, presented research on hydrogen embrittlement and a proposed engineering metric he called fracture-fatigue entropy (FFE).
Consari said hydrogen embrittlement makes metals less ductile and more prone to sudden fracture, particularly under fluctuating pressure or stress cycles. "Hydrogen embrittlement is a serious material integrity problem," he said, and he likened the effect to "taking a paper clip and you bend it back and forth," where cycling generates damage and reduces life.
The LSU research team tested multiple loading modes (tension-compression, bending, torsion) and tracked a material measure they call FFE. Consari described experiments in which specimens were stopped at a predefined FFE threshold (about 90 percent of the predicted life) and then re-energized; specimens that had reached the threshold failed rapidly when resumed, supporting FFE as a potential life metric.
Consari said hydrogen charging of specimens reduced the material's fatigue capacity substantially in laboratory tests and that the FFE value varied by material. He said FFE is temperature-dependent but that experiments to several temperature ranges showed the parameter remains a useful predictor. He noted Europeans are doing parallel work but that academic results vary across studies.
Why it matters: hydrogen embrittlement can reduce the useful life of steels used in pipelines, tanks and rotating machinery. Consari urged further research, standard test protocols and consideration of FFE in codes so engineers can predict remaining useful life and take preventive maintenance actions before catastrophic failure.
Consari said his group is preparing papers for publication and that NSF-supported work and industry collaborations are underway to expand the dataset and explore practical code adoption.
