• Journal of the Korean Wood Science and Technology
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• 제33권5호통권133호
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• pp.21-28
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• 2005

For the proper conservation of wooden cultural properties, non-destructive evaluation (NDE) method, which can be used to quantitatively evaluate the internal state of wood members, are needed. In this study, an ultrasonic CT system composed of portable devices was attempted, and the capacity of this system was verified by reconstructing the CT images for two phantoms and two artificially defected specimens. Results from this study showed that the sizes of detected defects were enlarged and the shapes were distorted on the CT images. Also, the positions were shifted somewhat toward the surface of specimen, which is regarded due to the anisotropic property of wood. Compared to the filtered back-projection method, SIRT (simultaneous iterative reconstruction technique) method was determined to be more efficient as the algorithm of image reconstruction for wood. A new ultrasonic CT system is thought to be used as a NDE method for wood. However wood characteristics and wave diffraction within wood made it difficult to accurately evaluate the size, shape and position of defects. To improve the quality of CT image of wood, more research including the relationship between wood and ultrasound is needed, and wood properties should be taken into consideration on the image reconstruction algorithm.

• Journal of the Korean Wood Science and Technology
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• 제31권6호
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• pp.45-54
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• 2003

The density and strength of wood is affected by degradations and defects, such as voids and knots. Old wooden structures such as traditional cultural properties have been deteriorated by these types of defects. They were evaluated by a visual observation that is difficult to evaluate the inner deterioration in structures. In this study, three nondestructive testing techniques were investigated to detect the wooden structural members. Ultrasonic stress wave tests, drilling resistance tests and visual inspections were used to examine the structural wood members. Patterns of Resistograph using by drilling resistance tests could indicate the features of internal wood such as voids, knots, decay, fungi, and so on. The technique just like as ultrasonic stress wave tests, however, difficult to detect exactly area where small amounts of internal deterioration in logs are. In spite of results of ultrasonic stress wave test, the internal deterioration of wooden structural members could be evaluated by the relationship between ultrasonic stress wave tests and drilling resistance tests.

• 한국가구학회지
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• 제24권3호
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• pp.302-308
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• 2013

To collection of field data for development of maintenance manual of Han-ok, we investigated defects which occurred in members of Han-ok by field investigation. The noticeable defects were wood cracks, gaps that developed between wood pillar and wall or wood window frame and tenon joints. The most common biological defect was blue stain which was created in log. The mold generation was observed on exterior wood and wall which get wet by precipitation. The gaps between members of Han-ok pointed out as defect that is urgently improved by residents of Han-ok. The reason is mainly due to poor of insulation in winter by bad confidentiality. The maintenance work of defect such as gap was conducted personally. As a result, the repair parts were ugly for unfamiliar repair work.

• Journal of the Korean Wood Science and Technology
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• 제36권1호
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• pp.61-68
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• 2008

초음파 시험기를 이용하여 목재의 파단형상이 초음파의 속도에 미치는 영향과 송수신단자의 위치 변화를 통한 효율적인 결점부위 탐색방법을 검토하였다. 파단의 방향에 따른 초음파 속도는 송수신 단자와 평행방향의 파단에서는 영향을 미치지 않고 수직방향 파단에서만 영향을 주었다. 이는 초음파의 진행 경로에 결점부위가 위치하지 않을시 결점을 파악하지 못하는 단점을 보였다. 또한, 초음파의 진행방향과 수직으로 파단이 되었더라도 초음파가 진행되는 직선상에 파단부위가 존재하는 경우에만 파단여부를 확인할 수 있었다. 결점부위 판별 방법은 송수신 단자를 시편 양끝부분에 서로 엇갈리게(한쪽은 상단부에 반대편은 하단부에 위치) 위치시켰을 때 파단 존재여부가 확인되었다. 일정구간의 파단을 확인한 후 두 송수신 단자를 폭 방향으로 마주보게 위치시켜 구간별로 이동시키며 탐색하면 결점부위가 정밀하게 판별되었다.

• Journal of the Korean Wood Science and Technology
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• 제29권2호
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• pp.91-99
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• 2001

목재산업에서 생산성과 품질 향상을 위해서는 공정의 자동화가 절실히 요구되고 있다. 화상처리시스템의 현장 적용성 개선을 위해 국산 소나무와 상수리나무 및 서어나무를 대상으로 옹이, 할렬, 수피 등과 같은 주요 결함들을 인식해내는 알고리듬을 개발하였다. 목재가공공정에서 컨베이어 위를 이동하고 있는 목재를 가상하여 제재목의 규격과 목제품의 품질에 영향을 주는 표면결함들을 대상으로 그 형태와 크기 및 위치를 인식할 수 있는 화상 처리기술을 개발하였다. 화상처리를 이용하여 결함으로 인식된 각 라벨에 대해 8가지의 특성을 개발, 결함인식의 기준으로 사용하였으며, 8가지 특성을 이용하여 수종별 결함 추출의 제한 조건을 마련한 후 필터링을 실시하여 실제 결함과 결함으로 인정되지 않는 라벨을 구분하였다. 또한 수종별로 가장 효과적인 기준의 적용절차를 밝히므로써 결함 인식의 오차를 줄이는 한편, 처리대상 수종에 대한 유연성을 확보하고자 하였다. 한편, 컨베이어를 이동하고 있는 목재의 규격이나 표면상태에 관련된 모든 자료들이 database의 형태로 작성되도록 하여 이후 실제 산업현장에 대한 적용 가능성을 타진하고자 하였다. 그 결과 소나무와 상수리나무 표변에 존재하는 옹이의 오인률은 1% 이하로 매우 우수하였으며, 상수리나무의 할렬과 서어나무의 수피에 대한 오인률도 13% 이하로 낮출 수 있었다.

• Journal of the Korean Wood Science and Technology
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• 제42권5호
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• pp.516-522
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• 2014

Old architectural wood materials damaged by a fire were evaluated on the basis of wood species and scanning electron microscopy (SEM) observation of wood tissues in combination with energy dispersive X-ray spectroscopy (EDXS) analysis. Results of SEM observation showed that tracheid wall thickness of burned parts was very thin compared with undamaged and sound wood, and tylosoid in the resin canals disappeared after the exposure to fire. SEM-EDXS analysis indicated that carbon and oxygen peaks occurred in the original energy band, and the carbon peak was higher than that of the oxygen in the burned part. A computerized tomography was also undertaken to investigate the carbonization layer formed by fire and possible internal defects.

• Journal of the Korean Wood Science and Technology
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• 제41권2호
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• pp.164-172
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• 2013

The purpose of this research was development of quantitative ultrasonic test methodology for detecting internal defects in members of ancient wooden building. Connection part between wooden members and/or contacted or hidden part by wall of ceiling or other construction materials make it hard to apply direct way of ultrasonic test. So indirect way of ultrasonic test needed to be applied. Test methodology with newly developed prototype of ultrasonic system was proposed. Homogeneous material with polypropylene was also tested for establishing the criterion. Results showed that TOF(time of flight)-energy and pulse length were found out to be proper ultrasonic parameters for predicting depth of defect in wood different from polypropylene. It was not possible to directly apply prediction equation derived from polypropylene. Newly established prediction equation shows coefficient of determination of 0.73 for wood. Finally, defect of replaced rafter members was predicted with the coefficient of determination of 0.32. Various aspects of ultrasound propagation in wood including anisotropy need to be carefully considered to raise up the prediction accuracy.

• Journal of the Korean Wood Science and Technology
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• 제29권3호
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• pp.21-26
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• 2001

Acquisition of precise information on drying characteristics of wood is indispensable for the improvement of drying schedules and wood quality. Recognition of the exact moisture content at which drying defects such as checks occur during drying with given drying conditions may be essential to reduce drying losses. In this study an image-processing system was combined with a laboratory-scale wood dry kiln for experiments and the surface of tree disk of black locust (Robinia pseudoacacia L.) was monitored to investigate the behavior of check formation over all the drying process. This system showed good potential for improving drying schedules and wood product quality.

• Journal of the Korean Wood Science and Technology
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• 제29권2호
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• pp.100-108
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• 2001

제재목으로부터 얻을 수 있는 부재(部材)(parts)의 수율을 미리 예측할 수 있다면 최고의 수율 보장이 가능한 방법으로 재단할 수 있으므로 목재산업의 생산성을 크게 향상시킬 수 있다. 특히, 옹이와 같은 결점들이 많이 포함되어 있는 국산 중소경재의 경우 수율 예측을 통한 재단최적화는 매우 필요한 공정이 아닐 수 없다. 본 연구에서는 국산 상수리나무와 소나무를 대상으로 제재목 database를 구축하여 다중 종절우선 공정 모형에 적용함으로써 국산재의 가공효율을 탐색하는 동시에 최고의 수율이 보장되는 재단 방법을 제시하고자 하였다.

• Journal of the Korean Wood Science and Technology
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• 제49권5호
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• pp.471-481
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• 2021

This study investigated the hygroscopicity and UV deterioration characteristics of 3 domestic and 4 imported woods using natural oil, stain, and varnish paints. In terms of hygroscopicity, it was found that the hygroscopicity of the painted wood was lower than that of the unpainted wood, and that as the number of coatings increased, the hygroscopicity decreased. In terms of anti-absorption, oil-based chemical paints showed higher resistance than water-based paints, and natural oils showed results comparable to oil-based paints. As for the UV deterioration, the amount of color change of the painted wood was lower than that of the unpainted wood, and there was no significant difference according to the number of times of painting. The amount of color change was found to be low in oil-based paints and hardwoods. Through this study, we confirmed effective moisture blocking and small color changes during painting using paints, and it is believed that wood can be protected from internal and external defects through selective and efficient painting based on data for excellent painting performance.