• Corrosion Science and Technology
• /
• v.7 no.5
• /
• pp.296-299
• /
• 2008

High order statistical parameters were evaluated using the electrochemical noise data collected during corrosion of type 430 stainless steel coupled to a inert, platinum electrode in 3.5% NaCl solution. High order statistical parameters are shown to predict uniform corrosion properly. However, Localization index, skewness of current, kurtosis and skewness of potential are capable of predicting pitting corrosion only when the transients are large with long life time. Of the high order statistical parameters evaluated, kurtosis of current is found to be the most sensitive parameter for detecting uniform and pitting corrosion.

• Advances in concrete construction
• /
• v.7 no.1
• /
• pp.11-22
• /
• 2019

A comprehensive assessing approach for durability of reinforced concrete structures dealing with the corrosion process of rebar subjected to the attack of aggressive agent from environment was proposed in this paper. Corrosion of rebar was suggested in the form of combination of global corrosion and pitting. Firstly, for the purposed of considering the influence of rebar's radius, a type of Plane Corrosion Model (PCM) based on uniform corrosion of rebar was introduced. By means of FE simulation approach, global corrosion process of rebar regarding PCM and LCM (Linear Corrosion Model) was regressed and compared according to the data from Laboratoire $Mat{\acute{e}}riaux$ et $Durabilit{\acute{e}}$ des Constructions (LMDC). Secondly, pitting factor model of rebar in general descend law with corrosion degree was introduced in terms of existing experimental data. Finally, with the comprehensive numerical simulation, the durability of an existing arch bridge was studied in depth in deterministic way, including diffusion process and sectional strength of typical cross section of arch, crossbeam and deck slab. Evolution of structural capacity considering life-cycle rehabilitation strategy indicated the degradation law of durability of reinforced arch bridges.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.25 no.2
• /
• pp.87-104
• /
• 1989

Recently, with the tendency of more lightening, high-strength and high-speed in the marine industries such as marine structures, ships and chemical plants, the use of the aluminium Alloy is rapidly enlarge and there occurs much interest in the study of corrosion fatigue crack characteristics. In this paper, the initiation of surface crack and the propagation characteristics on the base metal and weld zone of 5086-H116 Aluminium Alloy Plate which is one of the Al-Mg serious alloy(A5000serious) used most when building the special vessels, were investigated by the plane bending corrosion fatigue under the environments of marine, air and applying cathodic protection. The effects of various specific resistances on the initiation, propagation behavior of corrosion fatigue crack and corrosion fatigue life in the base metal and heat affected zone were examined and its corrosion sensitivity was quantitatively obtained. The effects of corrosion on the crack depth in relation to the uniform surface crack length were also investigated. Also, the structural, mechanical and electro-chemical characteristics of the metal at the weld zone were inspected to verify the reasons of crack propagation behavior in the corrosion fatigue fracture. In addition, the effect of cathodic protection in the fracture surface of weld zone was examined fractographically by Scanning Electron Microscope(S.E.M.). The main results obtained are as follows; (1) The initial corrosion fatigue crack sensitibity under specific resistance of 25Ω.cm% show 2.22 in the base metal and 19.6 in the HEZ, and the sensitivity decreases as specific resistance increases (2) By removing reinforcement of weldment, the initiation and propagation of corrosion crack in the HAZ are delayed, and corrosion fatigue life increases. (3) As specific resistance decreases, the sensitivity difference of corrosion fatigue life in the base metal and HAZ is more susceptible than that of intial corrosion fatigue crack. (4) Experimental constant, m(Paris' rule) in the marine environment is in the range of about 3.69 to 4.26, and as specific resistance increases, thje magnitude of experimental constant, also increases and the effect by corrosion decreases. (5) Comparing surface crack length with crack depth, the crack depth toward the thickness of specimen in air is more deeply propagated than that in corrosion environment. (6) The propagation particulars of corrosion fatigue crack for HAZ under initial stress intensity factor range of $\Delta$k sub(li) =27.2kgf.mm super(-3/2) and stress ratio of R=0 shows the retardative phenomenon of crack propagation by the plastic deformation at crack tip. (7) Number of stress cycles to corrosion fatigue crack initiation of the base metal and the welding heat affected zone are delayed by the cathodic protection under the natural sea water. The cathodic protection effect for corrosion fatigue crack initiation is eminent when the protection potential is -1100 mV(SCE). (8) When the protection potential E=-1100 mV(SCE), the corrosion fatigue crack propagation of welding heat affected zone is more rapid than that of the case without protection, because of the microfissure caused by welding heat cycle.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2007.04a
• /
• pp.3-17
• /
• 2007

This paper provides an introduction to life-span simulation and numerical approach to support the performance design processes of reinforced concrete structures. An integrated computational system is proposed for life-span simulation of reinforced concrete. Conservation of moisture, carbon dioxide, oxygen, chloride, calcium and momentum is solved with hydration, carbonation, corrosion, ion dissolution. damage evolution and their thermodynamic/mechanical equilibrium. Coupled analysis of mass transport and damage mechanics associated with steel corrosion is presented for structural performance assessment of reinforced concrete. Multi-scale modeling of micro-pore formation and transport phenomena of moisture and ions are mutually linked for predicting the corrosion of reinforcement and volumetric changes. The interaction of crack propagation with corroded gel migration can also be simulated. Two finite element codes. multi-chemo physical simulation code (DuCOM) and nonlinear dynamic code of structural reinforced concrete (COM3) were combined together to form the integrated simulation system. This computational system was verified by the laboratory scale and large scale experiments of damaged reinforced concrete members under static loads, and has been applied to safety and serviceability assessment of existing structures. Based on the damage details predicted by the nonlinear finite element analytical system, the life-span-cost of RC structures including the original construction costs and the repairing costs for possible damage during the service life can be evaluated for design purpose.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.4
• /
• pp.2401-2406
• /
• 2015

Pipelines are used by large heavy industries to deliver various types of fluids. Since this is important to maintain the performance of large systems, it is necessary to accurately predict remaining life of the corroded pipeline. However, predicting the remaining life is difficult due to uncertainties in the associated variables, such as geometries, material properties, corrosion rate, etc. In this paper, a statistical method for predicting corrosion remaining life is proposed using Bayesian inference. To accomplish this, pipeline failure probability was calculated using prior information about pipeline failure pressure according to elapsed time, and the given experimental data based on Bayes' rule. The corrosion remaining life was calculated as the elapsed time with 10 % failure probability. Using 10 and 50 samples generated from random variables affecting the corrosion of the pipe, the pipeline failure probability was estimated, after which the estimated remaining useful life was compared with the assumed true remaining useful life.

• Earthquakes and Structures
• /
• v.25 no.1
• /
• pp.69-78
• /
• 2023

Life-cycle performance analysis of a reinforced concrete box section bridge was generated. Moreover, Monte Carlo simulation with important sampling (IS) was used to simulate the bridge material and load uncertainties. The bridge deterioration model was generated with the basic probabilistic principles and updated according to the measurement data. A genetic algorithm (GA) with the response surface model (RSM) was used to determine the deterioration rate. The importance of health monitoring systems to sustain the bridge to give services economically and reliably and the advantages of fiber-optic sensors for SHM applications were discussed in detail. This study showed that the most effective loss of strength in reinforced concrete box section bridges is corrosion of the reinforcements. Due to reinforcement corrosion, the use of the bridge, which was examined, could not meet the desired strength performance in 25 years, and the need for reinforcement. In addition, it has been determined that long-term health monitoring systems are an essential approach for bridges to provide safe and economical service. Moreover the use of fiber optic sensors has many advantages because of the ability of the sensors to be resistant to environmental conditions and to make sensitive measurements.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.14 no.3
• /
• pp.88-94
• /
• 2006

The compressive residual stress, which is induced by shot peening process, has the effect of increasing the intrinsic fatigue strength of surface and therefore would be beneficial in reducing the probability of fatigue damage. However, the effect of shot peening in corrosion environment was not known. In this study, investigated is the effect of shot peening on corrosion fatigue crack growth of SAE 5155 steel immersed in 6% $FeCl_3$ solution and corrosion characteristics with considering fracture mechanics. The results of the experimental study corrosion fatigue characteristics of SAE 5155 are as follows; the fatigue crack growth rate of the shot peening material was lower than that of the non-peening material. And fatigue life shows more improvement in the shot peening material than in non-peening material. This is due to the compressive residual stress of surface increases resistance of corrosion fatigue crack propagation. It is assumed that the shot peening process improve corrosive resistance and mechanical property.

• Proceedings of the KSR Conference
• /
• 2004.10a
• /
• pp.663-667
• /
• 2004

Underframes of rolling stock structure are made of hot rolled steel of SS400 or SM490A. While these underframe steels are designed to satisfy the mechanical requirements, their corrosion behavior also should taken into account. Underframes are coated to prevent corrosion, but they are often defected by external factors to result in local corrosion which may cause the weakness of mechanical strength. Thus, the corrosion of underframe steels was examined through atmospheric corrosion test to estimate service life and safety.

• Journal of Korean Society of Water and Wastewater
• /
• v.21 no.6
• /
• pp.689-699
• /
• 2007

The accurate estimation of water pipe deterioration is indispensable to prevent pipe breakage and manage in advance. In this study, corrosion of water pipe is adopted, which is relatively underestimated although it takes most part of deteriorating pipeline. Predicting corrosion rate and corrosion depth of a pipe can make an increase the life span of the pipeline, which is laid under the ground according to characteristics of soil and water corrosion. For the purpose, mathematical models that can presume nominal depth through estimation of pit corrosion and corrosion rate is introduced. As comparison of results with conventional methods in other foreign countries, it is evaluated that the external corrosion depth is estimated less than the models, proposed by other researchers and the internal corrosion rate was processed faster than the external corrosion rate.

• Corrosion Science and Technology
• /
• v.20 no.4
• /
• pp.169-174
• /
• 2021

In this study, performance tests, a field evaluation, and a life cycle cost (LCC) analysis for high performance coating systems were conducted to prepare a plan to reduce the cost of maintenance coating and contribute to the service life extension of steel bridges by applying high performance coatings to steel bridges that will be constructed in the future. From the deterioration models based on the field evaluation for chlorinated rubber and urethane topcoat systems, which have been applied often, the mean service lives were derived as 20.8 and 26.6 years, respectively. For the other coating systems that have not been applied in practice, the coordination factors were differentially applied with evaluation items. The most durable coating system was predicted to be thermal spray coating (TSC) primer/epoxy intermediate coat/fluoride resin topcoat, with a predicted value as long as 42.2 years. The LCC analysis indicates that partial application of high performance coating, such as TSC and fluoride resin, to specific parts vulnerable to corrosion and ultraviolet ray (UV) is more advantageous than the use of general coating systems.