• Journal of the Korea Concrete Institute
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• v.17 no.6 s.90
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• pp.1045-1051
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• 2005

For critical structures and application, where a given reliability must be met, it is necessary to account for uncertainties and variability in material properties, structural parameters affecting the corrosion process, in addition to the statistical and decision uncertainties. This paper presents an approach to the fuzzy arithmetic based modeling of the chloride-induced corrosion of reinforcement in concrete structures that takes into account the uncertainties in the physical models of chloride penetration into concrete and corrosion of steel reinforcement, as well as the uncertainties in the governing parameters, including concrete diffusivity, concrete cover depth, surface chloride concentration and critical chloride level for corrosion initiation. The parameters of the models are regarded as fuzzy numbers with proper membership function adapted to statistical data of the governing parameters and the fuzziness of the corrosion time is determined by the fuzzy arithmetic of interval arithmetic and extension principle

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.6
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• pp.129-139
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• 2008

Due to uncertainty of numerous variables in durability model, a probalistic approach is increasing. Monte Carlo simulation (Level III method) is an easily accessible method, but requires a lot of repeated operations. This paper evaluated the effectiveness of First Order Second Moment method (Level II method), which is more convenient and time saving method than MCS, to predict the corrosion initiation in harbor concrete structure. Mean Value First Order Second Moment method (MV FOSM) and Advanced First Order Second Moment method (AFOSM) are applied to the error function solution of Fick's second law modeling chloride diffusion. Reliability index and failure probability based on MV FOSM and AFOSM are compared with the results by MCS. The comparison showed that AFOSM and MCS predict the similar reliability index and MV FOSM underestimates the probability of corrosion initiation by chloride attack. Also, the sensitivity of variables in durability model to corrosion initiation probability was evaluated on the basis of AFOSM. The results showed that AFOSM is a simple and efficient method to estimate the probability of corrosion initiation in harbor structures.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.24 no.2
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• pp.94-100
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• 1988

Recently with the rapid development in marine and shipbuilding industries such as marine structures, ship, and chemical plants, there occurs much interest in the study of corrosion fatigue characteristics was closed up an important role in mechanical design. In this study, the 5086 Al-Alloy was tested by used of a rotary bending fatigue tester and was investigated under the environments of various specific resistance and air. The specific resistance, as a corrosion environment, was changed 15, 20, 25 and 5000$\Omega$.cm. The corrosion fatigue crack initiation sensitivity was quantitatively inspected for 5086 Al-Alloy in the various specific resistance. The experimental constants of Paris rule were examined in the various specific resistances, and the influences of load and corrosion with affect the crack growth rate were compared with. Main results obtained are as follows: (1) Number of stress cycles to corrosion fatigue crack initiation delaies and corrosion fatigue crack initiation sensitivity decreases with the increasing for the specific resistance. (2) The experimental constant m of Paris rule decreases with the decreasing for specific resistance. Hence the effect of corrosion is more susceptible than that of stress intensity factor. (3) The corrosion fatigue crack of 5086 Aluminium Alloy appears intergranular fracture. (4) Corrosion sensitivity is decreased with the increasing stress intensity factor and is nearly uniform when stress intensity factor is over 40kg.mm super(-3/2)

• Nuclear Engineering and Technology
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• v.53 no.6
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• pp.1909-1923
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• 2021

We experimentally investigated the effects of thermal aging and cold work on the microstructure, mechanical properties, and primary water stress corrosion cracking (PWSCC) initiation time for Alloy 182 welds. The effects of thermal aging and cold work on the PWSCC initiation time of Alloy 182 were modeled based on the plastic energy concept and the PWSCC initiation data of this study and previous reports by considering censored data. Based on the results, it is estimated that the PWSCC resistance of the Alloy 182 weld firstly increases and then decreases with thermal aging time when the applied stress is kept constant.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.829-834
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• 2005

A series of reinforced G109 type specimens was fabricated and pended with a 15 weight percent NaCl solution. Mix design variables included 1) two cement alkalinities (equivalent alkalinities of 0.32 and 1.08), 2) w/c 0.50 and 3) two rebar surface conditions (as-received and wire-brushed). Potential and macro-cell current between top and bottom bars were monitored to determine corrosion initiation time. Once corrosion was initiated, the specimen was ultimately autopsied to perform visual inspection, and the procedure included determination of the number and size of air voids along the top half of the upper steel surface. This size determination was based upon a diameter measurement assuming the air voids to be half spheres or ellipse. The followings were reached based upon the visual inspection of G109 specimens that were autopsied to date. First, voids at the steel-concrete interface facilitated passive film breakdown and onset of localized corrosion. Based upon this, the initiation mechanism probably involved a concentration cell with contiguous concrete coated and bare steel serving as cathodes and anodes, respectively. Second, the corrosion tended to initiate at relatively large voids. Third, specimens with wire-brushed steel had a lower number of voids at the interface for both cement alkalinities, suggesting that air voids preferentially formed on the rough as-received surface compared to the smooth wire brushed one.

• Corrosion Science and Technology
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• v.22 no.1
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• pp.44-54
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• 2023

The rupture disk corrosion test (RDCT) method was recently developed to evaluate stress corrosion cracking (SCC) and was found to have great potential for the real-time detection of SCC initiation in a high temperature and pressure environment, simulating the primary water coolant of pressurized water reactors. However, it is difficult to directly measure the stress applied to a disk specimen, which is an essential factor in SCC initiation. In this work, finite element analysis (FEA) was performed using ABAQUS^TM to calculate the stress and deformation of a disk specimen. To determine the best mesh design for a thin disk specimen, hexahedron, hex-dominated, and tetrahedron models were used in FEA. All models revealed similar dome-shaped deformation behavior of the disk specimen. However, there was a considerable difference in stress distribution in the disk specimens. In the hex-dominated model, the applied stress was calculated to be the maximum at the dome center, whereas the stress was calculated to be the maximum at the dome edge in the hexahedron and tetrahedron models. From a comparison of the FEA results with deformation behavior and SCC location on the disk specimen after RDCT, the most proper FE model was found to be the tetrahedron model.

• Structural Engineering and Mechanics
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• v.84 no.6
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• pp.831-849
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• 2022

One of the most prevalent causes of reinforced concrete (RC) structural deterioration is chloride-induced corrosion. This paper aims to provide a comprehensive insight into the environmental effect of RC's chloride ingress process. The first step is to investigate how relative humidity, temperature, and wind influence chloride ingress into concrete. The probability of initiation time of chloride-induced corrosion is predicted using a probabilistic model that considers these aspects. Parametric analysis is conducted on several factors impacting the corrosion process, including the depth of concrete cover, surface chloride concentration, relative humidity, and temperature to expose environmental features. According to the findings, environmental factors such as surface chloride concentration, relative humidity and temperature substantially impact on the time to corrosion initiation. The long- and short-distance impacts are also examined. The meteorological data from the National Meteorological Center of China are collected and used to analyze the environmental characteristics of the chloride ingress issue for structures along China's coastline. Finally, various recommendations are made for improving durability design against chloride attacks.

• Corrosion Science and Technology
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• v.7 no.5
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• pp.243-251
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• 2008

Magnesium alloys become popular research topic in last decade due to its light weight and relatively high strength-to-weight ratio in the energy aspiration age. Almost all structure materials are supposed to suspend stress. Magnesium is quite sensitive to corrosive environment, and also sensitive to environmental assisted cracking. However, so far we have the limited knowledge about the environmental sensitive cracking of magnesium alloys. The corrosion fatigue (CF) test was conducted. Many factors' effects, like grain size, texture, heat treatment, loading frequency, stress ratio, strain rate, chemical composition of environment, pH value, relative humidity were investigated. The results showed that all these factors had obvious influence on the crack initiation and propagation. Especially the dependence of CF life on pH value and frequency is quite different to the other traditional structural metallic materials. In order to interpret the results, the electrochemistry tests by polarization dynamic curve and electrochemical impedance spectroscopy were conducted with and without stress. The corrosion of magnesium alloys was also studied by in-situ observation in environmental scanning electron microscopy (ESEM). The corrosion rate changed with the wetting time during the initial corrosion process. The pre-charging of hydrogen caused crack initiated at $\beta$ phase, and with the increase of wetting time the crack propagated, implying that hydrogen produced by corrosion reaction participated in the process.

• Computers and Concrete
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• v.13 no.1
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• pp.71-82
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• 2014

Chloride ion ingress is one of the major problems that affect the durability of concrete structures such as bridge decks, concrete pavements, and other structures exposed to harsh saline environments. Therefore, durability based design of concrete structures in severe condition has gained great significance in recent decades and various mathematical models for estimating the service life of rein-forced concrete have been proposed. In spite of comprehensive researches on the corrosion of rein-forced concrete, there are still various controversial concepts in quantitation of durability parameters such as chloride diffusion coefficient and surface chloride content. Effect of environment conditions on the durability of concrete structures is one of the most important issues. Hence, regional investigations are necessary for durability based design and evaluation of the models. Persian Gulf is one of the most aggressive regions of the world because of elevated temperature and humidity as well as high content of chloride ions in seawater. The aim of this study is evaluation of some parameters of durability of RC structures in marine environment from viewpoint of corrosion initiation. For this purpose, some experiments were carried out on the real RC structures and in laboratory. The result showed that various uncertainties in parameters of durability were existed.

• Journal of Ocean Engineering and Technology
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• v.4 no.1
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• pp.88-100
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• 1990

Among the test methods to evaluate stress-corrosion cracking(SCC) on the basis of fracture mechanics, constant displacement(bolt) loading method using modified-WOL specimen is practically convenient. In this test method, compliance formula is generally required to calculate load(consequently $K_{ISCC}$). There are many problems in using the analytic compliance formula to calculate $K_{ISCC}$, so we had proposed the experimental $K_{ISCC}$ evaluation technique in the previous report. This study has employed the slightly altered configuration of modified-WOL specimen made of weldable structural stee(BS360-50D). With these specimens, stress-corrosion tests have been performed in $H_2S$ gas saturated 20% HCl solution. Through the test, the problems as mentioned earlier have been discussed again, and the proposed evaluation technique has been verified. And the stress-corrosion cracks and hydrogen blisters have been investigated in the initiation step with the aids of metallurgical micrographs, SEM fractographs, and EPMA analysis. The inclusions segregated in the mid-thickness region traps hydrogen to produce the hydrogen blistering. The applied or residual stress does not contribute the occurrence of the blister. Hydrogen absorbed into the mid-thickness region is consumed to produce the blistering so that stress-corrosion crack could hardly be detected at that region. The stress-corrosion cracks initiate from the inclusions and propagate in radial pattern. And the initiation site is remote from the crack tip and is inclined from the crack plane, which is assumed to be caused by the triaxial stress and the amount of the absorbed hydrogen.