Strain gradient plasticity-based modeling of hydrogen environment assisted cracking

By E. Mart'inez-Paneda, Christian F. Niordson, Richard P.Gangloff. 2016

160 citations recorded by the source corpus.

Abstract Finite element analysis of stress about a blunt crack tip, emphasizing finite strain and phenomenological and mechanism-based strain gradient plasticity (SGP) formulations, is integrated with electrochemical assessment of occluded-crack tip hydrogen (H) solubility and two H-decohesion models to predict hydrogen environment assisted crack growth properties. SGP elevates crack tip geometrically necessary dislocation density and flow stress, with enhancement declining with increasing alloy strength. Elevated hydrostatic stress promotes high-trapped H concentration for crack tip damage; it is imperative to account for SGP in H cracking models. Predictions of the threshold stress intensity factor and H-diffusion limited Stage II crack growth rate agree with experimental data for a high strength austenitic Ni-Cu superalloy (Monel®K-500) and two modern ultra-high strength martensitic steels (AerMet™100 and Ferrium™M54) stressed in 0.6 M NaCl solution over a range of applied potential. For Monel®K-500, KTH is accurately predicted versus cathodic potential using either classical or gradient-modified formulations; however, Stage II growth rate is best predicted by a SGP description of crack tip stress that justifies a critical distance of 1 μm. For steel, threshold and growth rate are best predicted using high-hydrostatic stress that exceeds 6 to 8 times alloy yield strength and extends 1 μm ahead of the crack tip. This stress is nearly achieved with a three-length phenomenological SGP formulation, but additional stress enhancement is needed, perhaps due to tip geometry or slip-microstructure.

Subfields: Materials Chemistry, Mechanics of Materials, Metals and Alloys

View Paper: https://www.semanticscholar.org/paper/8db510fe24da3d3c7c69bace840d5e596a07f578

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In Materials Chemistry

1. Alireza Golahmar
2. E. Mart'inez-Paneda
3. Christian F. Niordson

In Mechanics of Materials

1. Alireza Golahmar
2. E. Mart'inez-Paneda
3. Christian F. Niordson

In Metals and Alloys

1. Alireza Golahmar
2. E. Mart'inez-Paneda
3. Christian F. Niordson

Citations in the corpus

• A phase field formulation for hydrogen assisted cracking (2018, methodology): “Crack initiation thresholds and growth rates have been computed through dislocation-based methods [2,3], weakest-link approaches [4,5], and, eminently, cohesive zone models [6–10], which can easily incorporate the cohesive strength reduction with hydrogen coverage.”