10.5923.j.mechanics.20140402.03.pdf - International Journal...

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International Journal of Mechanics and Applications 2014, 4(2): 50-57 DOI: 10.5923/j.mechanics.20140402.03 Lifetime Estimation of Chain Plates for Floodgates Working in Seawater by Continuum Fatigue-Creep Damage Theory and Transient Analysis of Diffusion Process of Hydrogen Hak Jin Song * , Sun Jong Jon, Gi Chol Yang, Nam Chol Kim Department of Mechanics of Materials, Kim Chaek University of Technology, Pyongyang, Korea Abstract Numerical estimation of lifetime of chain plates made of 45Cr high strength steel for floodgates working in seawater has been performed by considering fatigue-creep crack initiation and hydrogen assisted crack propagation at the plate. The computational model has been validated by some related experiments on the material. First, tensile test results for the material of chain plates used for 20 years in seawater were compared with the ones for new material. According to the results, yield stress and fracture ductility of the material used for 20 years in seawater are considerably lower than the ones of new material. Second, records of operations of the floodgates were analyzed to estimate real lifetime of the chain plates and some other parameters which are necessary for computational study on the same objects. According to the records of operating history of the floodgates, average lifetime of the chain plates falls within the limit of 18~22 years. Third, lifetime of the chain plates was estimated by continuum fatigue-creep damage theory and transient analysis of the diffusion process of atomic hydrogen in the metallic lattice. Estimated lifetime of the chain plates was a little longer than the real lifetime obtained from the records because of some unexpected conditions. Keywords Stress corrosion cracking, Fatigue-creep damage, Hydrogen embrittlement, Stress-assisted diffusion, Stress concentration, Lifetime 1. Introduction Stress-corrosion cracking (SCC) and hydrogen embrittlement (HE) are related and take main part in environment-assisted cracking, which remain incompletely understood from the view point of mechanics. Accordingly, accurate prediction of the lifetime of engineering components undergoing SCC and HE is necessary in the field of mechanical design, but still remains elusive goal. Considerable theoretical and experimental studies on SCC and HE of high strength steels were carried out for prediction and extension of lifetime of the components working in corrosion environment. There were lots of studies on behavior of hydrogen in the metallic lattice including the studies on adsorption and absorption of hydrogen at the surface of material. Many works have evaluated the diffusion process of hydrogen in the lattice using Fick’s law, and illustrated the results with some related experiments [2, 3, 5]. Some other works have studied degradation process * Corresponding author: [email protected] (Hak Jin Song) Published online at Copyright © 2014 Scientific & Academic Publishing. All Rights Reserved of metals via SCC and HE mechanism, by which mechanical
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