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.

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.

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.

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.

비파괴 기법을 이용한 록볼트의 건전도 평가(Ⅰ)-이론 및 적용성 평가-

이종섭,이인모,이용준,엄태원,한신인 사단법인 한국터널지하공간학회 2006 한국터널지하공간학회논문집 Vol.8 No.1

The purpose of this study is to describe the Non-Destructive Testing(NDT) of the rockbolt and investigate the applicability of the NDT methods to estimate the integrity of the rockbolt. To examine the rockbolt integrity including rockbolt itself and grouting material, two methods are adopted: numerical and experimental methods. In the numerical method, the numerical code DISPERSE is used to analyze the dispersion of the rockbolt. The dispersion curve shows the effects of the thickness and stiffness of grouted materials on the embedded rockbolt. Therefore, the optimal frequency for the integrity test of the rockbolt is obtained: 20∼120kHz in L(1,0) mode. In the experimental methods, destructive and non-destructive tests are carried out in a laboratory. In the non-destructive test, the low frequency mode generated by an impact and the high frequency mode generated by an ultrasonic transducer seem to characterize the rockbolt condition readily. The experimental results show that the guided waves attenuate more significantly when the stiffness of the grouted material increases and/or the zone of the defect increases. Meanwhile, the ultimate capacity of rockbolt was evaluated through the pull-out tests and is compared to the NDT results. This study demonstrates that the NDT is a valuable tool for the rockbolt integrity evaluation. 본 연구의 목적은 록볼트의 건전도를 평가하기 위하여 록볼트의 비파괴시험을 기술하고 비파괴시험의 적용성을 조사하는 것이다. 록볼트 자체와 그라우팅제를 포함한 록볼트의 건전도를 평가하기 위하여, 수치해석 및 실험적 방법을 이용한 두가지 방법이 적용되었다. 수치해석 방법에서는, 분석은 “DISPERSE” 프로그램을 이용하여 록볼트의 분산선도를 해석하였다. 분산선도 곡선은 지중근입되어 있는 록볼트에 대한 그라우팅제의 두께와 강성에 대한 영향을 보여준다. 이로 부터 록볼트의 건전도 시험을 위한 최적의 주파수를 추정할 수 있으며, 그 결과 L(1,0) 모드에서 20~120kHz가 최적의 주파수로 산정되었다. 실험적 방법에서는 실험실에서 시료를 제작하여 파괴 및 비파괴시험을 실시하였다. 비파괴 실험에서는 타격을 이용한 저주파수 모드와 초음파 트랜스듀서를 이용한 고주파수 모드를 통하여 록볼트의 상태를 조사할 수 있다. 실험실에서 수행된 비파괴실험으로부터, 유도파는 주변의 그라우팅제의 강도가 증가하거나 (또는 증가하고) 결함부 영역이 증가할 때 감쇠가 커짐을 알 수 있었다. 그리고 인발시험으로부터 록볼트의 극한지지력을 추정하였다. 본 연구는 록볼트의 건전도 평가에 비파괴시험이 매우 유용한 방법임을 보여준다.

도로시설물 적용 앵커볼트 결함 검출을 위한 비파괴(Ultrasonic) 검사기법 적용에 대한 연구

서동우(Dong-Woo Seo),김재환(Jaehwan Kim),이진혁(Jin-Hyuk Lee),조한민(Han-Min Cho),박상기(Sangki Park),김민수(Min-Soo Kim) 한국방재안전학회 2022 한국방재안전학회 논문집 Vol.15 No.4

국내의 앵커볼트 일반 비파괴 검사법은 육안검사와 타음검사를 적용하고 있으나, 육안검사는 기초에 포함된 부분이나 너트 및 베이스플레이트가 설치된 부분에서 앵커볼트의 부식이나 피로균열 등을 확인하는 것이 어렵다. 타음검사는 주변 환경과 개인차에 의한 영향을 받기 때문에 객관적인 조사가 어려운 것이 현실이므로 이러한 결함을 정량적으로 추정할 수 있는 비파괴 검사 기술개발이 필요하다. 국내 도로시설물 앵커볼트의 점검은 육안조사를 수행하고 있으며, 교량받침, 낙교방지시설 등의 앵커볼트 중요도가 높으므로 기존 점검방법과 함께 비파괴검사 기술을 개발하여 앵커볼트의 예방정비를 통해 교량 수명연장에 기여할 필요가 있다. 본 기술 개발을 통해 현재 수행하고 있지 않은 앵커볼트의 비파괴검사를 수행함으로 도로시설물 앵커볼트의 선제적/능동적 유지관리가 가능한 기술로 연구개발 및 실용화가 시급하다. 본 논문에서는 비파괴 검사 기법 중 초음파탐상법(Ultrasonic test)을 적용하여 부식, 균열 등 앵커볼트의 결함 검출 가능성 및 실뢰도를 실험적으로 검증하였다. 기술 개발이 완성되면 검사 신뢰성 향상 원천기술 확보로 앵커볼트에 대한 선제적/능동적 유지관리의 실현이 가능할 것으로 기대된다. The general non-destructive inspection method for anchor bolts in Korea applies visual inspection and hammering inspection, but it is difficult to check corrosion or fatigue cracks of anchor bolts in the part included in the foundation or in the part where the nut and base plate are installed. In reality, objective investigation is difficult because inspection is affected by the surrounding environment and individual differences, so it is necessary to develop non-destructive inspection technology that can quantitatively estimate these defects. Inspection of the anchor bolts of domestic road facilities is carried out by visual inspection, and since the importance of anchor bolts such as bridge bearings and fall prevention facilities is high, the life span of bridges is extended through preventive maintenance by developing non-destructive testing technology along with existing inspection methods. Through the development of this technology, non-destructive testing of anchor bolts is performed and as a technology capable of preemptive/active maintenance of anchor bolts for road facilities, practical use is urgently needed. In this paper, the possibility of detecting defects in anchor bolts such as corrosion and cracks and reliability were experimentally verified by applying the ultrasonic test among non-destructive inspection techniques. When the technology development is completed, it is expected that it will be possible to realize preemptive/active maintenance of anchor bolts by securing source technology for improving inspection reliability.

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.

비파괴시험 자료를 적용한 콘크리트 기준강도의 통계적 추정

백인열 ( In Yeol Paik ) 한국안전학회(구 한국산업안전학회) 2015 한국안전학회지 Vol.30 No.1

The aim of the paper is to introduce the statistical definition of the specified compressive strength of the concrete to be used for safety evaluation of the existing structure in domestic practice and to present the practical method to obtain the specified strength by utilizing the non-destructive test data as well as the limited number of core test data. The statistical definition of the specified compressive strength of concrete in the design codes is reviewed and the consistent formulations to statistically estimate the specifiedstrength for assessment are described. In order to prevent estimating an unrealistically small value of the specified strength due to limited number of data, it is proposed that the information from the non-destructive test data is combined to that of the minimum core test data. The the sample mean, standard deviation and total number of concrete test are obtained from combined test data. The proposed procedures are applied to an example test data composed of the artificial numerical values and the actual evaluation data collected from the bridge assessment reports. The calculation results show that the proposed statistical estimation procedures yield reasonable values of the specified strength for assessment by applying the non-destructive test data in addition to the limited number of core test data

Estimation of Present-Day Strength of Concrete for a 40-year-old Building from Non-destructive Tests: A Case Study

Soubhagya Karmakar,Dauji Saha,Kshirsagar Sandeep Shankar,Satish Kumar Saini,Bhargava Kapilesh,Mahapatra Kamalendu 아시아콘크리트학회 2021 Journal of Asian Concrete Federation Vol.7 No.2

Assessment of the present health of existing concrete structures is necessary, particularly for enhancing the life of the infrastructure facilities reaching the end of their design life. The codes stipulate establishment of sitespecific correlation expressions to estimate the compressive strength of concrete from indirect non-destructive tests (NDT) such as rebound hammer or ultrasonic pulse velocity tests. However, in certain circumstances, requisite number of partially destructive (core) tests required for establishing the site-specific equations might not be feasible. In such scenario, selection of a suitable correlation expression from literature has to be performed in a rational way, as discussed in this article with a case study of a 40-year-old concrete building. From the study, it has been observed that for the limited number of direct tests, the Indian code stipulation resulted in higher characteristic strength of concrete as compared to the parametric estimation, which can be attributed to the assumption of Normal distribution and code stipulated (conservative) standard deviation value. In case of the indirect estimation cases, the parametric characteristic strength was pretty close to the corresponding non-parametric values indicating that the fitted distributions represented the strength values very well. Recommendations for the suitable correlation expression from literature applicable for estimation of equivalent strength from NDT for the structure, recommendation for characteristic compressive strength of concrete and the suggestions for accounting for the inaccuracies in estimated strength in subsequent structural re-analysis have been provided from the results of the study.

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.