Non-destructive Evaluation Method for Service Lifetime of Chloroprene Rubber Compound Using Hardness

( Kwang-hwa Park ),( Chan-gu Lee ),( Joon-hyung Park ),( Kyung-ho Chung ) 한국고무학회 2021 엘라스토머 및 콤포지트 Vol.56 No.3

Evaluating service lives of rubber materials at certain temperatures requires a destructive method (typically using elongation at break). In this study, a non-destructive method based on hardness change rate was proposed for evaluating the service life of chloroprene rubber (CR). Compared to the destructive method, this non-destructive method ensures homogeneity of CR specimens and requires a small number of samples. Thermal accelerated degradation test was conducted on the CR specimens at 55, 70, 85, 100, and 125℃, and the tensile strength, elongation at break, and hardness were measured. The results of the experiment were compared to those of the accelerated life evaluation method proposed in this study. Comparing the analyzed lives in the high temperature region (70, 85, 100, and 125℃), the difference between the service lives for the destructive method (using the elongation at break) and non-destructive method (using the hardness) was approximately 0.1 year. Therefore, it was confirmed that the proposed non-destructive evaluation method based on hardness changes can evaluate the actual life of CR under thermally accelerated degradation conditions.

Destructive and Non-destructive Tests of Bamboo Oriented Strand Board under Various Shelling Ratios and Resin Contents

( Sena Maulana ),( Yuarsa Gumelar ),( Adesna Fatrawana ),( Muhammad Iqbal Maulana ),( Wahyu Hidayat ),( Ihak Sumardi ),( Nyoman Jaya Wistara ),( Seung Hwan Lee ),( Nam Hun Kim ),( Fauzi Febrianto ) 한국목재공학회 2019 목재공학 Vol.47 No.4

The objectives of this study were to evaluate the effects of shelling ratio and resin content on the properties of bamboo oriented strand board (BOSB) from betung (Dendrocalamus asper) and to determine the correlation between the results of dynamic and static bending tests. Strands were steam-treated at 126 ºC for 1 h under 0.14 MPa pressure and followed by washing with 1% NaOH solution. Three-layer BOSB with the core layer perpendicular to the surface was formed with shelling ratios (face:core ratio) of 30:70; 40:60; 50:50; 60:40 and binded with 7% and 8% of phenol formaldehyde (PF) resin with the addition of 1% of wax. The evaluation of physical and mechanical properties of BOSB was conducted in accordance with the JIS A 5908:2003 standard and the results were compared with CSA 0437.0 standard for commercial OSB (Grade O-1). Non-destructive testing was conducted using Metriguard Model 239A Stress Wave Timer which has a wave propagation time from 1 to 9,999 μs and a resolution of 1 μs. BOSB with 8% resin content showed better physical and mechanical properties than those with 7% resin content. The increase of the face layer ratio improved the strength of BOSB in parallel direction to the grain. The results suggested that shelling ratio of 50:50 could be used as a simple way to reduce PF resin requirements from 8% to 7% and to meet the requirements of CSA 0437.0 standard. The results of non-destructive and destructive tests showed a strong correlation, suggesting that non-destructive test can be used to estimate the bending properties of BOSB.

RFI 공정 부품 비파괴검사용 표준 기공률 시편 제조 방법 및 기공률에 따른 기계적 물성 영향에 대한 연구

한성현,이정완,김정수,김영민,김위대,엄문광 한국복합재료학회 2019 Composites research Vol.32 No.6

The RFI process is an OoA process that fiber mats and resin films are laminated and cured in a vacuum bag. In case that resin film is insufficient to fill empty space in fibers, it makes void defect in composites and this void decrease mechanical properties of the composites. For this reason, non-destructive testing is usually used to evaluate void of manufactured composites. So, in this study, a manufacturing method of standard void specimens, which are able to be used as references in non-destructive testing, was proposed by controlling resin film thickness in the RFI process. Also, a fiber compaction test was proposed as a method to set the resin film thicknesses depending on target voids of manufacturing panels. The target void panels of 0%, 2%, and 4% were made by the proposed methods, and signal attenuation depending on void was measured by non-destructive testing and image analysis. In addition, voids of specimens for tensile, in-plane, short beam and compressive tests were estimated by signal attenuation, and mechanical properties were evaluated depending on the voids. RFI 공정은 진공백 내부에 섬유 매트와 수지 필름을 적층하여 성형하는 OoA 공정이다. 외부에서 따로 주입되는 수지가 없기 때문에 수지 필름의 양이 섬유가 필요로 하는 양보다 적은 경우 복합재 내부에 기공 결함이 발생하며 기계적 물성이 저하된다. 이러한 이유로 제작한 복합재를 실용화하기 위해서 비파괴검사를 이용한 기공 예측이 필수적으로 요구된다. 따라서 본 연구에서는 RFI 공정에서 비파괴검사 시 기준으로 사용할 수 있는 표준 기공률 시편을 제조하는 방법을 제시하였다. 표준 기공률 시편 제작 방법으로 수지 필름 두께를 조절하는 방법을 사용하였으며, 목표 기공률별 수지 필름 두께를 설정하기 위한 방법으로 섬유 압착 실험을 제시하였다. 수지 필름 두께 조절을 통하여 0%, 2%, 4%의 목표 기공률 패널을 제작했고 비파괴시험과 기공률 측정을 통하여 기공률에 따른 비파괴검사 신호 감쇠를 측정했다. 또한 인장, 면내전단, 숏빔, 압축 시편의 신호 감쇠를 통하여 기공률을 추정하였고, 기공률에 따른 기계적 물성을 평가하였다.

조기강도 콘크리트의 압축강도 추정을 위한 비파괴검사 실험식의 제안

이태규 ( Tae-gyu Lee ),강연우 ( Yeon-woo Kang ),최형길 ( Hyeong-gil Choi ),최경철 ( Gyeong-choel Choe ),김규용 ( Gyu-yong Kim ) 한국건축시공학회 2016 한국건축시공학회지 Vol.16 No.3

현장에서는 콘크리트 공사시 거푸집 탈형작업을 위한 다양한 기술들이 활용되고 있다. 그중에서 콘크리트의 압축강도추정을 위한 비파괴 시험방법에는 다양한 방법들이 제시되고 있지만, 일반적으로 타격법(반발경도법이라 칭함)과 비타격법(초음파법이라 칭함)을 활용한 시험방법이 주로 활용된다. 비파괴시험에 의한 압축강도의 추정은 경험 값에 의한 방정식에 의하여 계산할 수 있으며 다양한 식들이 제시되고 있으나, 초기재령에서 조기강도가 발현되는 콘크리트에 대한 데이터는 적은 편으로 기존의 강도추정식에 의한 압축강도의 계산에는 한계점이 있을 수 있다. 본 연구에서는 현장에서 주로 활용되는 조기탈형용 콘크리트의 배합을 활용하여 소형 공시체 및 Mock-up 시험체의 파괴 및 비파괴검사를 수행하였으며, 기존 비파괴검사 추정식을 통한 강도결과 값을 분석하였다. 실험결과, 기존 연구의 비파괴시험에 의한 제안식을 활용한 압축강도 추정값은 파괴시험방법에 비하여 하회하는 경향으로 70% 이하의 값을 나타냈으며, 초음파속도에 의한 신뢰성은 강도가 높아질수록 낮아지는것으로 확인되었다. 본 연구의 범위에서 조기강도 발현 콘크리트의 강도추정에 있어 기존식의 활용의 한계점이 있을것으로 분석되어, 24~60MPa의 콘크리트를 대상으로 반발경도법 및 초음파속도법에 의한 추정식을 제안하였다. In construction field, it used various technique for concrete formwork. Part of them, non-destructive test has been conducted to estimate a compressive strength of concrete easily such as rebound method and ultrasonic pulse velocity method etc. Former research has recommend proposed equation based on experimental data to investigate strength of concrete but it was sometimes deferent actual value of that from in field because of the few of data in case of early strength concrete. In this study, an experiment was conducted to analyze strength properties for early strength concrete using cylinder mold and 1,000mm×1,000mm×200mm rectangular specimen. And compressive strength of concrete was tested by non-destructive test, and calculated by the equation proposed former research. As a result, the non-destructive test results showed approximately 70 percent of the failure test value for all conditions, and worse reliability was obtained for high strength concrete samples when the ultrasonic pulse velocity method was used. Based on the scope of this study, the experimental equation for estimating compressive strength of early strength concrete from 24MPa to 60MPa was proposed.

국방 비파괴검사 분야 디지털 방사선투과시험 적용 연구

박경환,이민희,김선진,박순우,이남례 한국산학기술학회 2023 한국산학기술학회논문지 Vol.24 No.11

The utilization of digital non-destructive testing in the private sector is increasing with its commercialization. Accordingly, the need for non-destructive testing using digital radiography has recently increased in the defense field. On the other hand, its use in the defense field is very limited because of the absence of domestic and defense standards for applying digital radiography. In developed countries, such as Europe and the United States, research related to establishing standards for digital radiography is being actively conducted, and its application to the civil and military fields is expanding. In Korea, however, there is a lack of verification of the suitability of digital non-destructive testing. This study reviewed the requirements for digital radiography required by international standards and performed a suitability assessment. The results of this research are expected to contribute to increasing the usability of domestic digital radiography and can be used to establish standards for digital non-destructive testing methods.

허프 변환과 최소제곱법을 이용한 세라믹 영상에서의 결함 검출

홍동진(Dong-Jin Hong),차의영(Eui-Young Cha) 한국컴퓨터정보학회 2015 韓國컴퓨터情報學會論文誌 Vol.20 No.10

In this paper, we suggest a method of detecting defects by applying Hough transform and least squares on ceramic images obtained from non-destructive testing. In the ceramic images obtained from non-destructive testing, the background area, where the defect does not exist, commonly show gradual change of luminosity in vertical direction. In order to extract the background area which is going to be used in the detection of defects, Hough transform is performed to rotate the ceramic image in a way that the direction of overall luminosity change lies in the vertical direction as much as possible. Least squares are then applied on the rotated image to approximate the contrast value of the background area. The extracted background area is used for extracting defects from the ceramic images. In this paper we applied this method on ceramic images acquired from non-destructive testing. It was confirmed that extracted background area could be effectively applied for searching the section where the defect exists and detecting the defect.

유도탄 신뢰성평가 분야 중성자 비파괴검사 기법 적용 연구

박경환(Gyeong Hwan Park),김종열(Jongyul Kim),문명국(Myung Kook Moon),이남례(Namrye Lee) 한국산학기술학회 2023 한국산학기술학회논문지 Vol.24 No.9

유도탄은 장기간 저장되는 고가의 무기체계로서 1번의 사용으로 임무를 다하는 특성을 가지며, 주로 20년이상 군에서 운용되기 때문에 유도탄에 대한 사용가능성, 신뢰성, 안전성 등을 평가하고 관리하는 것은 매우 중요한 업무이다. 유도탄의 수명을 좌우하는 주요 부품들은 1회 사용 시 재사용이 불가능한 One-Shot Device이며, 이러한 부품들의 신뢰성평가 방법에는 비파괴 검사가 주로 활용된다. 비파괴검사란 무기체계에 영향을 주지 않고 검사하는 방법으로서, 재료에 파괴나 손상을 주지 않기 때문에 고가의 무기체계 검사에 주로 활용된다. 비파괴검사에는 방사선, 누설, 초음파등 다양한 검사방법이 존재하며, 유도탄 비파괴검사에는 주로 X-선 이용한 방사선 투과검사가 활용된다. 그러나 X-선의 경우 원자번호가 높은 물질로 구성된 부품에 대한 투과력이 낮아, 내부결함 검사에 제한이 있는 경우가 자주 발생한다. 이러한 X-선검사의 단점을 보완할 수 있는 비파괴검사 방법이 바로 중성자 투과검사이다. 중성자 투과검사는 X-선과 달리 원자번호가 높은 물질에 대한 투과력이 강한 반면, 물과 같이 가벼운 물질에 대한 투과성은 낮은 특성을 가진다. 본 연구에서는 유도탄 신뢰성평가 분야에 중성자 비파괴검사 기술을 적용하기 위한 연구들을 수행하였으며, 기존 X-선 검사 결과를 비교분석하여 향후 중성자와 X-선을 융합한 디지털 트윈기술의 활용 필요성을 검토하였다. A guided missile is an expensive weapon system stored for an extended period that can fulfill its mission with a single use. Evaluating and managing the usability, reliability, and safety of guided missiles is vital because the military has operated them for more than 20 years. The main parts that determine the lifespan of a guided missile are One-shot Devices that cannot be reused. Non-destructive testing is a method of inspecting a weapon system without destruction or damage. Accordingly, non-destructive testing is used mainly to evaluate the reliability of expensive weapon system inspections. Various types of non-destructive inspection methods are available, such as radiographic inspection, leak inspection, and ultrasonic inspection, and radiographic inspection using X-rays is used mainly for the non-destructive inspection of guided missiles. On the other hand, in the case of radiographic inspection using X-rays, internal defect inspection is often limited to parts composed of materials with high atomic numbers. The neutron transmission inspection method is a non-destructive inspection method that can compensate for the disadvantages of X-ray inspection. Unlike x-rays, neutrons have high penetrating power for materials with high atomic numbers and low penetrating power for materials with low atomic numbers, such as water. In this study, studies were conducted to apply neutron non-destructive testing technology to a missile reliability evaluation, and a comparative analysis was performed with the existing X-ray test results.

균열 탐지기술 및 최근 연구 동향

배석인,김지환 한국항공우주학회 2013 한국항공우주학회 학술발표회 논문집 Vol.2013 No.11

항공기 정비작업에서 구조적 손상과 정비의 범위를 설정하는 것은 매우 중요한 일이다. NDT(Non-destructive testing)는 이러한 정비작업을 가장 효율적이게 하는 방법으로 결함을 탐측하는 유용한 방법이다. 이는 항공기와 부분품에 대한 균열과 부식 등 까지 탐측해낼 수 있으므로 첨단 기술산업에 널리 쓰이고 있다. 현재 NDT 기술은 5 가지 대표적인 방법이 주류를 이루고 있다. 이와 아울러 요즘에는 이상의 기술외에도 많은 기법이 개발/발전되고 있다. 이러한 기술은 각각의 장/단점 및 한계를 가지고 있기 때문에 적합한 기법을 선정하여 수행하는 것이 NDT 기법의 신뢰성과 안전도를 높일 수 있다. 이를 바탕으로 향후 자동검사장비와 고성능센서의 개발을 통해 더욱더 진보될 것으로 사료된다. In aircraft maintenance program, it is important to inspect the structural damage and assess the limitation of the repair. NDT(Non-destructive testing) is the most effective method of inspection and also the only way to check defects. And the method can detect cracks or any other defect in the aircraft structure and engine components et al, thus it is widely used in advanced aerospace industry. Further, NDT is dominated by big five techniques such as penetrant test, ultrasonics, radiography, eddy current and magnetic particle test. Nowadays, other advanced methods have been developed. In this report, various NDT methods have been reviewed and discussed in detail. These techniques have many advantages and at the same time also has its own disadvantages. Indeed, each method contains some limitations to evaluate and characterize defects. Only with appropriate applications of non-destructive testing techniques can bring the reliability and safety. NDT industry is to be more advanced by development of automatic test equipment and high-performance sensors in the future.

Detection of Subsurface Defects in Metal Materials Using Infrared Thermography; Image Processing and Finite Element Modeling

Ranjit, Shrestha,Kim, Won Tae The Korean Society for Nondestructive Testing 2014 한국비파괴검사학회지 Vol.34 No.2

Infrared thermography is an emerging approach to non-contact, non-intrusive, and non-destructive inspection of various solid materials such as metals, composites, and semiconductors for industrial and research interests. In this study, data processing was applied to infrared thermography measurements to detect defects in metals that were widely used in industrial fields. When analyzing experimental data from infrared thermographic testing, raw images were often not appropriate. Thus, various data analysis methods were used at the pre-processing and processing levels in data processing programs for quantitative analysis of defect detection and characterization; these increased the infrared non-destructive testing capabilities since subtle defects signature became apparent. A 3D finite element simulation was performed to verify and analyze the data obtained from both the experiment and the image processing techniques.

충격공진시험을 이용한 다양한 공극률을 가진 투수성 아스팔트 혼합물의 동탄성계수 변화 측정에 관한 연구

장병관,양성린,문성호 한국도로학회 2013 한국도로학회논문집 Vol.15 No.3

PURPOSES: This study is to evaluate the dynamic modulus changes of permeable asphalt mixtures by using non-destructive impact testing method and to compare the dynamic moduli of permeable asphalt mixtures through repeated freezing and thawing conditions. METHODS: For the study, non-destructive impact testing method is used in order to obtain dynamic modulus of asphalt specimen and to confirm the change of dynamic modulus before and after freezing and thawing conditions. RESULTS : This study has shown that the dynamic moduli of asphalt concrete specimens consisting of 10%, 15% and 20% porosity are reduced by 11.851%, 1.9564%, 24.593% after freezing and thawing cycles. CONCLUSIONS : Non-destructive impact testing method is very useful and has repeatability. Specimen with 15% porosity has high durability than others.