Staircase-Like Crack Progression Due to Hydrogen Embrittlement of Cold-Worked Steel Strand

Joseph Rogelio Fernandez

doi:10.18282/ims.v2i1.180

Joseph Rogelio Fernandez Saint Petersburg College

DOI: https://doi.org/10.18282/ims.v2i1.180

Keywords: Mechanical, Creep and stress rupture, Thermomechanical Processing, Failure analysis, Corrosion and wear

Abstract

Stressed carbon steel strand in an ungrouted duct susceptibility to pitting corrosion is low due to surface corrosion, but susceptibility of steel strand to Hydrogen Embrittlement (HE) can increase under those conditions.

The HE will facilitate crack growth within the strand. Various crack propagation mechanisms, such as longitudinal splitting and shear-cracking, have been shown as possible strand failure mechanisms by themselves in strand, but this may not be true in stressed strand in piles that has been embrittled by Hydrogen and without pre-cracking (Cracks initiating from stress concentrations naturally rather than with notching). Concentration measurements were performed to determine the level of Hydrogen involved in the embrittlement.

Results indicate that the fracture mechanism differs from shear cracking or longitudinal splitting alone as previously shown, but is a multi-step process of crack propagation starting perpendicular to stress, followed by variations of inter-lamellae longitudinal splitting at brittle region of lamellae and shear cracking at breaks in the lamellae. This process results in the crack following a “staircase” progression, and finally leading to ductile overload once cross-section has been significantly reduced. This fracture mechanism was also shown to be valid whether the strand was stressed by bending or mult-axially by stressing through a duct.

Author Biography

Joseph Rogelio Fernandez, Saint Petersburg College

Joseph Fernandez was born in Perth Amboy, New Jersey in 1978 and raised in Saint Petersburg, Florida most of his life. He earned a Bachelor of Science Degree in Nuclear Engineering from Purdue University in 2000 and a Master of Science Degree in Material Science and Engineering from University of South Florida in 2011. He worked at Scientech Inc. as a Probabilistic Risk Analysis consultant for about a year working on such nuclear power plants as Cook, Clinton, and San Onofre Nuclear Power Plant. He then moved out west to consult for General Electric as a Probabilistic Risk Analyst for their nuclear power plant project known as Lungmen Unit 4 in Taiwan. He is currently a Project Engineer at Beatriz Corporation as well as an Adjunct Professor in Chemistry at Saint Petersburg College.

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