바이올린용 소재의 진동모드 해석에 관한 연구 -제2보. 소재 연륜폭 및 절삭방향이 브릿지의 공진주파수에 미치는 영향

정우양,Chung Woo-Yang 한국가구학회 2005 한국가구학회지 Vol.16 No.1

European maple is famous for the optimum solid wood for making bridge which is the most important part in violin acoustics. This study was carried out to investigate the variation of main features, i. e. annual ring width and cutting direction of costly imported violin bridge blanks and to examine the effect of these features of the blanks on the vibrational characteristics of bridge blanks. Imported violin bridge blanks had somewhat large variation in major macroscopical and physical properties and there was little relationship between annual ring density and weight of maple blanks. Resonant frequency of violin bridge blanks had some positive correlation with weight, however, damping having negative relationship with frequency was seldom affected by any physical properties of the maple blanks. Deviation from the radial cutting of tail side(ray direction from top toward feet on the edge of bridge blank) lowered the resonant frequency. Consequently, weight and ray direction should be taken for the critical quality decisive factors(QDF) of incoming bridge blanks by not only inspectors also luthiers who tune the bridge by shaping and are responsible for the final timbre quality of this complicate instrument.

家具用 中密度纖維板의 壓縮 粘彈性에 關한 硏究 ( II ) - 利用 含水率別 크리이프 및 應力弛緩 擧動 變化 -

정우양(Woo Yang Chung) 한국가구학회 1991 한국가구학회지 Vol.2 No.2

This experiment was carried out to examine the domestic MDF as substitute for the imported MDF and the long term service performance of furniture made of MDF by investigating the creep and stress relaxation behavior of both MDF at 3-staged moisture content level under significant loading level according to each physical properties and fiber element mixture as composition of the composite.<br/> Main results are as follows:<br/> Domestic MDF constructed with incomplete tracheid cell, wood fiber and even bark has lower specific gravity, internal bonding strength and MOR and has higher vapor and water absorption causing higher thickness swelling due to probably lower effective resin content or packing degree than the imported MDF of which the main composition is tracheid cell. So the former has not shown the material homogeneity as homogeneous continuum, normal creep and sound relaxation behavior as composite.<br/> Moisture content has great influence on the viscoelasticity of MDF as a wood-fiber based material. Intermediate MC maintain the internal resistant strngth of MDF but low MC causing micro crack and high MC causing fiber loosening showed significant lessening the load resistivity of the board. esp. domestic MDF

Dowel 직경과 Hole 내경 차이가 소재 및 목질재료로부터의 dowel 인발력에 미치는 영향

정우양(Woo Yang Chung) 한국가구학회 1990 한국가구학회지 Vol.1 No.1

Wooden dowel is widely used in most furniture manufacturing plants with mass production system. This study and experiment were carried out to get the more detail information on the dowel and designed to investigate the effect of dowel-hole diameter difference on the withdrawal strength in each direction of solid woods (lauan and rubber wood) and wood composites (MDF. PB and plywood).<br/> Spiral grooved ramin dowels with the range of 9.85mm to 10.15mm diameter were inserted into 10mm dia. pilot hole and tensioned by Universal testing matchine to compare the withdrawal strength. The main results were as following:<br/> 1. In general. withdrawal strength from solid wood exceeded those from wood composites regardless of the size of dowel and withdrawal strength from side grain surface restraining the withdrawing was higher than those from end grain surface in solid.<br/> 2. Rubber wood Joint strength deceased with increase of diameter of spiral grooved dowel but lauan with somewhat lower density showed the highest with drawal strength when the diameter of dowel was the largest. vice versa.<br/> 3. In wood composite jointing. the withdrawal strength from face alse exceeded those from edge in all types of boards.<br/> 4. MDF showed the highest withdrawal strength at the minimum dowel-hole diameter difference both from side and edge surface.<br/> 5. Particleboard has inherent weak point of internal delamination during dowel inserting and service. so we need not to make larger dowel than pilot hole.<br/> 6. Plywood showed somewhat different joint characteristics from other composites and had the highest withdrawal strength with slender dowel(9.85mm) similar to rubber wood.

음향환경과 목재과학

정우양 ( Woo Yang Chung ),강욱 ( Wook Kang ) 한국목재공학회 2003 목재공학 Vol.31 No.2

바이올린 브릿지의 음향적 특성 및 SDM 시뮬레이션에 관한 연구

정우양(Woo Yang Chung),박선행(Sun Haeng Park) 한국가구학회 2001 한국가구학회지 Vol.12 No.1

Violin bridge blank cut from maple wood with good quality has typical pattern of the radial direction in the side edge with minimal dispersion. This experimental study was designed and carried out to examine the effect of the physical and macroscopical characteristics on the compressive creep of violin bridge blank which had been imported from European manufacturer. This research arose from the idea that the maple solid wood with heterogeneous wood density and ray direction in the side edge would have uneven prological property of violin bridge blank which is supposed to be pressed by the tension of strings. Experimentally, the compressive creep of bridge blank became smaller with the higher density of imported maple \OOd and showed clear density-dependence for the duration of load under the string tension of 5 kgf. Every bridge blank showed the behavior of primary creep stage(stress stabilization) having logarithmic regression creep curve with high correlation coefficient under the designed stress level. Even though the relationship between compressive creep and ray direction on the side edge of bridge was not so clear contrary to expectation, we could conclude that wood density and ray direction should be the quality decisive factors affecting the acoustical characteristics and perfomance of the bridge, the core member of violin-family bow instruments.<br/> Keywords: violin, bridge, blank, wood density, maple, ray diretion, resonant frequency, string tension, annual ring density, compressive creep behavior<br/>

Studies on the Vibrational Modal Analysis of Solid Woods for making the Violin - Part 2. The effects of coating materials on the resonant frequency of European spruce and maple

정우양(Woo Yang Chung),박선행(Sun Haeng Park) 한국가구학회 2000 한국가구학회지 Vol.11 No.2

일반적으로 도막의 剛性은 목재의 剛性에 비해 낮으므로 도장된 소재의 강성이 백골재에 비해 낮아질 것으로 짐작할 수 있으므로 본 연구에서는 바이올린용 소재인 유럽산 가문비나무와 단풍나무에 투명래커와 전전통옻칠을 도포한 후, 진동모드를 해석하고 공진주파수를 비교함으로써 수종별 도료 종류에 따른 음향특성의 변화양상을 분석하고자 하였다 .<br/> 분석결과 , 도장전후의 기본진동모드는 동일하였고 양 수종 공히 도료의 종류에 관계없이 도장재의 공진주파수의 감소가 확인되었으며 가문비나무의 경우 , 모드가 증가할수록 주파수 減少幅이 증가하였으나 옻칠이 투명래커에 비해 그 감소폭이 적었다. 단풍나무의 경우에도 상위 보드에서 더 큰 자파수 감소를 나따냈지만 옻칠과 투명래커의 주파수 감소폭이 일정치 않았다.<br/> It was thought that the stiffness of a coated specimen became lower than that of the solid wood because the stiffness of the dried film of coating material is lower than that of the solid wood. The authors were trying to compare the effect of lacquer varnish and rhus lacquer on the resonant frequency of the solid woods for the violin, spruce and maple. Vibration modal shape of coated specimens were same to those of solid woods, but the frequency became lower at each mode as were expected regardless of coat. Frequency decrement of coated specimen was getting larger at upper mode in both European violin woods, however, rhus lacquer coated spruce specimens were less affected than lacquer varnish coated specimens.<br/> Key words: violin, spruce, maple, modal analysis, resonant frequency, cutting direction, lacquer varnish, rhus lacquer<br/>

건식 열처리에 의한 죽재의 변색 특성 및 日光堅牢度 비교 연구

정우양(Woo Yang Chung) 한국가구학회 2021 한국가구학회지 Vol.32 No.4

The eco-material, bamboo is famous for its sustainable growth and high carbon reserving capacity which has been used for various crafts and hygienic tools. This study was carried out to analyze the safe coloration and lasting possibility of three domestic bamboo species, i.e. Wangdae (P. bambusoides), Maengjonjuk (P. pubescens), Somdae (P. nigra var. henonsis). Intrinsic color characteristics of dried culm of Wangdae is the most light (highest L-value) and Somdae showed the highest b-value (high chroma, yellowness). Three bamboos revealed common response to heat treatment showing more distinct L-value change than those of a-value and b-value comparatively. So the lightness was chosen as the index of heat reaction in this study. The decrease of L-value of Wangdae due to heat was noticeable from 140°C and showed drastic darkening at 200°C for 30min. Maenjonjuk reacted slowly showing the darkening in 30min treatment, while Somdae showed quick response in short treatment (15 min) at each temperature. Therefore the author concluded that Wangdae and Somdae were suitable for short heat treatment in bamboo coloration and high temperature (200°C) was recommendable for high level darkening regardless bamboo species. Light fastness of heat treated bamboo culm were strengthened with increase the temperature and duration of heat treatment with three bamboos commomly. Consequently, author got the important information on the coloration and fastness for the utilization of domestic bamboo species.

학문생태계 환경변화와 목재공학의 대응전략

정우양 ( Woo Yang Chung ) 한국목재공학회 2019 한국목재공학회 학술발표논문집 Vol.2019 No.2

약 45억년 동안 크고작은 빙하기를 지나면서 5차례의 大滅種(mass extinction)을 겪으면서도 지구생태계의 생물들은 나름대로의 적응을 통해 끊임없이 진화해왔다. 이미 국내의 학문생태계도 급격한 학령인구 감소, 철학부재의 국가주도적 학술진흥정책, 약탈 학술지의 범람 등 미증유의 환경변화에 직면하고 있다. 50년전인 1970년에 모태였던 임학과로부터 비로소 학문적 독자성을 선언한 목재공학계도 예외는 아니어서 냉엄한 학문생태계에서의 생존을 위해 변신과 부침을 거듭해왔다, ‘임산공학’으로 대표되는 목재공학분야는 임산가공학과로 시작하여 국립 10개 대학과 사립 5개 대학에서 임학과의 재결합, 조경학과의 융합, 환경이나 인테리어 등을 표방하며 때로는 피동적으로 때로는 능동적으로 나름의 생존전략을 펼쳐왔다. 한편 산림청과 국가연구기관인 산림과학원도 예외는 아니어서 정권의 취향에 따라 인원감축, 조직개편 등 구조 조정의 외풍을 피하지 못하였으며, 이 과정에서 배태된 부작용 및 내부불만 등으로 인해 학연산 관련정책 조정자로서의 원활한 역할을 수행하지 못하고 있다. 이러한 어려운 환경하에서 수준높은 학술대회개최 및 학술지 발간, 활발한 국제교류를 통해 목재공학의 지속적 발전기반을 제공해야하는 학회는 그 역할과 소임이 막중하다 볼 수 있다. 각 대학의 학과 및 연구기관은 보다 전략적이고 합리적인 의사결정을 통해 구성원의 역량을 통합함으로서 험난한 학문적 생태환경을 극복해 나가야 할 것이다. 대학 및 연구기관의 연구자들은 목재만이 지니는 강점을 기반으로 자신의 전공과 주변의 연관학문들과의 주도적으로 융합을 통해 격변하는 학문생태계에서의 생존능력을 키워나가야 할 것이다. 즉 미래학자들이 주창하는 오락(Entertainment), 건강(Health-care), 환경(Environment), 에너지(Energy) 분야에서의 목재공학 및 목재과학의 우월적 아이덴티티를 극대화함으로써 적자만이 생존할 수 있는 학문생태계에서의 지속가능성을 제고해 나가여 할 것이다.

기후변화에 대응하는 국가 정책 및 국내 가구산업의 발전 전략

정우양(Woo Yang Chung) 한국가구학회 2019 한국가구학회지 Vol.30 No.2

This paper was written to suggest the developmental strategy of furniture industry under the circumstance of climate change by reviewing the policy to reduce the greenhouse gas emisssion in Korea. It can be esteemed for the Korea government to insist on the systematical policy making and rational management to lessen the gas emission as the responsible member of international society. Especially the ministry of environment enhance the image of Korea as the positive country corresponding the climate change by implementing the mitigation actions with appropriate policies and financial support. Korea executed primordially the emissions trading scheme (ETS) in Asia and unveiled the three year operating report to install the framework to reduce the national greenhouse gas inventory to fulfill the goal of 37% reduction of the BAU gas emission until 2030. And let the small and medium business join the national greenhouse gas reduction effort by the Greenhouse gas/Energy Management by Object (GEMBO) program. Standing out the carbon storage function of wooden furniture as the medium lived HWP with half life of 30 years, the management of furniture industry can make the business strategy to improve the image as eco-friendly tool and to maximize the value of wooden furniture from designing to serving in consumers’ living space.

유럽産 바이올린用材의 比重과 年輪幅이 素材의 音響的 성질에 미치는 영향

정우양(Woo Yang Chung),홍병화(Byung Wha Hong) 한국가구학회 1999 한국가구학회지 Vol.10 No.1

This study was carried out to analyze the relationship between basic physical properties and acoustical characteristics of imported violin wood and to offer the information on raw material procurement and incoming-material quality control to domestic violin makers which have purchased most raw materials from European exporting countries at high expense.<br/> Equilibrium moisture content of European spruce with lower specific gravity after the prolonged storage was rather higher than that of European maple with higher specific gravity.<br/> The specific gravity of spruce increased with decreasing annual ring width, however, that of maple decreased with decreasing ring width due to the relatively smaller portion of latewood in narrower annual ring. Increasement in specific gravity enhanced the dynamic Young's modulus of both wood species, but influenced the vibration energy loss by internal friction differently between two species. For dynamic MOE, qurater-sawn spruce was higher than the flat-sawn, but maple showed the reverse directional characteristics.<br/> Consequently, it would be well for violin makers to establish the standard for materials and quality control system to assure the quality of their violin products.<br/> Keywords : Violin, Acoustics, Quality control, Specific gravity, Annual ring width, Resonance frequency, Internal friction. European spruce, European maple<br/>