• Korean Journal of Acupuncture
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• 제29권2호
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• pp.216-223
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• 2012

Objectives : Electroacupuncture is widely used because of its diverse curative influence. However, its electrical safety is not guaranteed when applied on the human body. Therefore, in this study, we did research on the corrosiveness of electroacupuncture when applied on the body fluid. Methods : We did research using acupuncture needles which were made of STS304 or STS316 and which were coated or not coated in silicone. They were 0.25 mm in diameter and 40 mm in length. We immersed them to the depth of about 1cm in Hank's Solution and gave a stimulus in 120 Hz for 60 minutes. Then, we measured the pH of Hank's solution and mass of needles and observed their shape. Results : Acupuncture needles which were made of STS304 corroded more easily than those which were made of STS316 when they were applied on the human body. Acupuncture needles which were coated in silicone corroded much more easily than those which were not coated in silicone when they were applied on the body fluid. Conclusions : In this study, we did research on the corrosiveness of electroacupuncture when it is applied on the body fluid using several acupuncture needles. We made a conclusion that when acupuncture needles were applied on the body fluid, the coated one made of STS304 corrodes more easily than the uncoated one made of STS316. We hope that additional further researches on the effect of the corrosiveness of an acupuncture needle will be carried out.

• Corrosion Science and Technology
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• 제21권5호
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• pp.418-421
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• 2022

Stir-accelerated corrosion test of a high chromium cast iron was attempted in 0.1 mol dm^-3 H₂SO₄ + 0.05 mol dm^-3 HCl + 10 wt% SiC solution for 48 h at room temperature or at 45 ℃. The high chromium cast iron was composed of 2.8 wt% C and 27 wt% Cr and balanced with Fe. The high chromium cast iron was positioned into a 500 mL beaker with stirring of the solution at 1050 rpm using a magnetic hot plate. The corrosion rate was increased by agitating the solution. In addition, the corroded depth of the high chromium cast iron surface was increased by agitating the solution. The surface morphology of the high chromium cast iron after the stir-accelerated corrosion test revealed that a dendritic austenite phase partially remained in the corroded region after agitating the solution, indicating that solution movement during agitating could accelerate the corrosion rate of the high chromium cast iron.

• Journal of Mechanical Science and Technology
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• 제16권7호
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• pp.889-895
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• 2002

This paper presents the effect of external corrosion, material properties, operation condition and design thickness in pipeline on failure prediction using a failure probability model. The predicted failure assessment for the simulated corrosion defects discovered in corroded pipeline is compared with that determined by ANSI/ASME B31G code and a modified B31G method. The effects of environmental, operational, and random design variables such as defect depth, pipe diameter, defect length, fluid pressure, corrosion rate, material yield stress and pipe thickness on the failure probability are systematically studied using a failure probability model for the corrosion pipeline.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.351-356
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• 2001

A potential loss of structural integrity due to aging of nuclear piping may have a significant effect on the safety of nuclear power plants. In particular, failures due to the erosion and corrosion defects are a major concern. As a result, there is a need to assess the remaining strength of pipe with erosion/corrosion defects. In this paper, a limit load solution for the eroded and corroded SA106 Grade B pipes subjected by internal pressure is developed. based in 3-D finite element analyses, considering a wide range of the shape of pipeline, flaw depth and axial flaw length parametrically.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 추계학술대회 논문집(I)
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• pp.31-37
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• 2002

Rail cars are subject to vibration, impact and wear which can cause severe defects leading to a fatal accident. Thus, they are designed and manufactured in consideration of such factors influencing their service lifetime. Under-frames are composed of steel and support most of load imposed on the car. Steel is very sensitive to corrosive environment and corroded even in a normal service condition. Regular maintenance can Protect steel Parts from corrosion by painting. However, an exposure of defect point to corrosive agents can make corrosion proceed to a considerable depth, which may cause the structure to remain under safety standard. It is necessary to understand corrosion behavior of rail cars in order to estimate unexpected accidents by corrosion.

• 한국재료학회지
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• 제8권3호
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• pp.268-273
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• 1998

Zircaloy-4 합금판재에 230-250ppm의 수소를 장입시키고 $400^{\circ}C$에서 72시간동안 균질하게 수소화물을 형성시킨후 $350^{\circ}C$의 static autoclave를 이용하여 여러 가지 농도의 LiOH 부식용액조건에서 부식시험을 수행하였다. 부식평가는 시간에 따른 무게증가의 변화로서 측정하였고, 시편의 미세구조는 광학현미경과 주사전자현미경을 사용하여 관찰하였다. 부식시험 후 형성된 산화막에서의 H와 Li의 분포를 확인하기 위해 secondary ion mass spectrometry(SIMS)를 이용해 각 원소의 분포를 두께방향에서 측정하였다. 여러 가지 농도의 LiOH 수용액조건에서 Li+ 이온의 용액농도가 30ppm 이상으로 증가하면 합금의 부식은 급격히 가속화되었다. 이것은 $Li^{+}$가 산화막 내의 $Zr^{4+}$ 자리를 치환함에 따라 산소공공이 증가로 산화반응이 증가되고, 이로 인해 형성되는 수소화물의 양이 증가하기 때문이다. LiOH용액조건에서 부식시험 전에 시편 내에 수소를 장입시켜 수소화물을 형성시키면 수소를 장입하지 않은 시편보다 부식이 더 빨리 가속되지만, 시험기간이 길어지면 오히려 수소를 미리 장입시키지 않은 시편의 부식속도가 더 빨라진다. 이것은 부식시험 전에 수소를 시편에 미리 장입을 시키면 이때 형성된 수소화물에 의해 초기에 부식이 빨리 가속되지만 이미 고용도 이상의 수소가 금속 내부에 존재하므로 부식과정 중에 생기는 수소가 금속의 내부로 확산되어 들어오는 것이 억제되어 부식속도가 둔화되는 것으로 생각된다.

• 한국구조물진단유지관리공학회 논문집
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• 제21권3호
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• pp.19-26
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• 2017

콘크리트는 다공성 건설재료이며, 매립된 철근의 부식은 내구성 및 안전성에 큰 영향을 미친다. 본 연구는 비파괴 검사인 반전위측정값과 생성된 부식량과의 상관성을 피복두께, 물-시멘트비를 고려하여 도출하는 것이다. 이를 위해, 3가지 수준의 물-시멘트비와 4가지 수준의 피복두께를 가진 시멘트 모르타르 시편이 제조되었으며, 3가지 수준의 촉진부식기간을 고려하여 부식량 및 반전위를 측정하였다. 습윤상태에서는 반전위가 크게 증가하였으며, 부식량과 촉진기간은 선형적인 관계를 가지고 있었다. 부식량이 증가할수록, 피복두께가 감소할수록, 물-시멘트비가 증가할수록 반전위는 증가하였다. 전체의 반전위 측정값을 부식량과 비교할 경우 0.67의 낮은 결정계수를 가지고 있었으나 부식량(촉진기간)을 고려하여 3가지 수준을 고려할 경우 0.90이상의 높은 결정계수를 가지고 있었다. 실내조건과 같이 온도가 일정하고 포화상태일 경우, 측정된 반전위는 부식량과 선형적인 상관성을 가지고 있었으며, 피복두께, 물-시멘트비, 철근직경, HCP의 측정범위를 알 수 있다면, 매립된 철근의 부식량을 예측할 수 있다고 판단된다.

• Advances in concrete construction
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• 제7권1호
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• pp.11-22
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• 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.

• 품질경영학회지
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• 제48권4호
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• pp.597-608
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• 2020

Purpose: The purpose of this paper is to present a probability distribution of the burst pressure of API 5L X65 pipes for the reliability assessment of corroded gas pipelines. Methods: Corrosion is a major cause of weakening the residual strength of the pipe. The mean residual strength on the corrosion defect can be obtained using the burst pressure code. However, in order to obtain the pipe reliability, a probability distribution of the burst pressure should be provided. This study is concerned with estimating the burst pressure distribution using Monte Carlo simulation. A response surface method is employed to represent the distribution parameter as a model of the corrosion defect size. Results: The experimental results suggest that the normal or Weibull distribution should be suitable as the probability distribution of the burst pressure. In particular, it was shown that the probability distribution parameters can be well predicted by using the depth and length of the corrosion defect. Conclusion: Given a corrosion defect on the pipe, its corresponding burst pressure distribution can be provided at instant. Subsequently, a reliability assessment of the pipe is conducted as well.

• Corrosion Science and Technology
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• 제22권4호
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• pp.252-256
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• 2023

The galvanostatic polarization technique was used to accelerate corrosion in high chromium cast iron (HCCI) immersed in a simulated slurry solution of 0.1 mol dm^-3 H₂SO₄, 0.05 mol dm^-3 HCl, and 10 wt% SiC. The HCCI contained 27 wt% of Cr and 2.8 wt% of C, and its microstructure mainly comprised austenitic and carbide phases. A two-electrode system using a dense carbon rod and the HCCI sample was employed for the galvanostatic polarization by applying an anodic current for 24 hours. The corrosion rate increased upon applying the anodic current, but the increase was not significant, particularly for current densities higher than 10 µA cm^-2. Following polarization, the corrosion morphology revealed that the anodic current accelerated surface corrosion in the HCCI; however while the depth of the corroded area increased, the increase was not substantial. The propagation behavior of the anodic current and its impact on corrosion were further discussed.