五种桉树木材的吸声性能

本文以广西东门林场的人工林尾叶桉(Eucalyptusurophylla),尾巨桉(EucalyptusurophyllaE.grandis),尾园桉(E.urophyllaE.tereticornis),尾赤桉(E.urophyllaE.camaldulensis)和大花序桉(E.cloeziana)木材为主要材料,用驻波管法测试了五种桉树木材的吸声系数,比较了这些桉树木材的吸声性能,结果显示五种桉树木材的吸声系数在频率1000赫兹之内变化不大,之后随频率的增加吸声系数也在增加。在频率200至2000赫兹范围内,五种桉树木材的吸声系数差异不显著,在低频区域,尾叶桉的吸声性能较好。在所测试的声波频率范围内,桉木弦锯板的吸声系数高于径锯板;0.5厘米厚的锯材的吸声性能好于1.0厘米厚的锯材;因此,桉木板材的种类和板材的厚度影响其吸声性能,但五种桉树木材的吸声性能差异不显著。图2表4参6。     

麦秸/聚氨酯复合人造板的工艺对其吸声系数的影响研究

通过变化麦秸和聚氨酯的比例、麦秸/聚氨酯复合人造板的密度、以及发泡温度,研究了麦秸/聚氨酯复合人造板在不同的声波频率下的吸声系数。试验结果表明:在不同的声波频率下,发泡温度的高低对麦秸/聚氨酯复合人造板的吸声系数有不同的影响;麦秸/聚氨酯复合人造板的密度与其吸声系数的大小关系密切;在声波频率为250～4 000Hz区域内,麦秸和聚氨酯的比例对麦秸/聚氨酯复合人造板的吸声系数影响较大。     

仿生木材结构穿孔纤维板吸声性能

以中密度纤维板为基材,通过设计穿孔结构及打孔方式,达到拓宽木质穿孔板吸声频带和提高声学性能的目的.利用分层加工工艺制备了带侧孔结构的穿孔纤维板,采用阻抗管传递函数法对穿孔纤维板吸声性能进行了测试.通过正交试验方法,研究了主孔直径、穿孔率、倾斜角度对穿孔纤维板吸声性能的影响,并获得了较优的制备工艺,随后利用控制变量法研究...     

日本改善住宅楼板隔音的研究进展

随着人们生活水平的提高，对居住环境隔音性能也提出了越来越高的要求。近年来日本在改善住宅隔音性能方面的研究非常活跃，并取得了很大进展。本文仅就其中关于改善较难隔绝的楼板撞击声性能方面的研究作简要介绍。我国国情虽然与日本不同，但其研究成果对于改善混凝土住宅的隔音性能也有一定参考价值。     

吸声保温玉米秸秆穰板制备及性能研究

以疏解后的玉米秸秆穰丝为基材,异氰酸酯为胶黏剂,均匀组坯后经热压制备成吸声保温玉米秸秆穰板。通过单因素试验分别探究了施胶量、热压温度板材密度、厚度对玉米秸秆穰板吸声、导热和压缩性能的影响。结果表明:综合板材的性能和生产成本,优化工艺为施胶量2%、热压温度140℃、密度0.10 g/cm3,所得板材吸声性能达到GB/T 16731—1997的Ⅲ级标准,压缩强度满足GB/T 25975—2010中的要求,属高效保温材料。     

丛生竹地板与毛竹地板吸声性能比较

以国产毛竹地板和印度丛生竹为原料制造的丛生竹地板为主要材料,用驻波管法测试了两种竹地板的吸声系数,比较了它们的吸声性能.结果显示:丛生竹地板的吸声性能好于毛竹地板,丛生竹地板和毛竹地板的平均吸声系数分别为0.231和0.213.在低频段(f≤1 000 Hz),毛竹地板的低频吸声特性优于丛生竹地板;在中高频段(1 000 Hz相似文献   

THE EFFECT OF WOOD SURFACE ROUGHNESS OF DIFFERENT SPECIES OF TREES ON WOOD COLOR IN WORKING OPERATION

Woodsurfaceroughnessisthemicrogeometrypropertycomposedbyalittlespacingandpeak-tovalley.Generallythesurfaceroughnesswascomposedbytheworkingmethodandotherfactorst123.Woodsurfaceroughnesswasnotonlyanimportantindexwhichmeasuredthesur-facesmoothextentofwoodproductandtheworkingqualitybutalsothewoodsur-fitceroughnessaffectedwoodsurfacefeel--lngandpsychologicalfeeling[3'4,lo,ll:.Th,'quantitativesurftlceproPertyparametersweretheimportantpartwhichmarkedthewoodsurfacevisualpsycho1ogicalmagni-tude,whichha…     

几种树种木材制造石膏刨花板的适应性

本文论述了挪威云杉、山杨、白桦和柞木及山杨、白桦、柞木的混合刨花制造石膏刨花板的适应性。结果表明,在工艺参数相同的情况下,木材密度越大的树种制成的板材强度越低,挪威云杉板强度最大,山杨板次之,柞木板极低。挪威云杉和山杨是制造石膏刨花板的优质树种。改变木膏比、刨花体积和对刨花进行水抽提均没有使白桦和柞木制成合格的石膏刨花板。混合刨花干扰石膏刨花板的凝固时间,致使板子强度低劣,在生产中应予避免。     

A THEORY OF DETERMINING MASS TRANSFERPARAMETERS FOR WOOD PARTICLE MATERIALS

INTRoD[JCTIONTllcrcsearcI1OI1tl1ctI1c111opl1}'sIcalprop-crtiesofl1catandl11asstransfcrproccsscsi11``oodparticlcl11atcrlalsisratllcrlll11ltcdcur-rcntI}O11l}afct`papcrssofarasconccn1slllnybclbund(Slla11g.19(j()).Ho\tc\cr'tl1cullll,attol1a11dtI1cproductionof\"oodcl1ipa11dx`oodslla\lngctc.Asra\`matcrlals(Sl1ang*I()9l)forpulpandpapcr'paniclcboards'\\'oodfucl(Martalcna.l988)ort\'oodpaFticlc111atc-rialhascdcom6ositcproductsarcincrcasil1goxcrtllcx"orldTllccfficicnttechnolog1caIllandlil1gofth…     

Evaluation of surface smoothness by laser displacement sensor 1: effect of wood species

The best methods for determining surface roughness in an industrial environment are of the noncontact variety, with reproduction of the profile. The objective of this work was to compare the roughness profile obtained by a contact stylus with a commercial laser displacement sensor (LDS). Measurements were done using 15 wood species with different densities and colors, based on which special triangle profiles were prepared. The accuracy of the laser sensor was examined by statistical analysis of roughness parameters measured from the profiles. Experimental results show that LDS profiles were imitated correctly. However, LDS accuracy depends on the scanned wood properties (density and color), installation position of the sensor, and profile shape. It was found that evaluation of dark and high-density wooden surfaces was imperfect.Part of this work was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, April 2000; and at the 51st Annual Meeting of the Japan Wood Research Society, Tokyo, April 2001     

THE EFFECT OF HEAT TREATMENT ON DIFFERENT SPECIES WOOD COLOUR

Woodisnaturalmaterial,naturegivewoodsurfacecolor,g]oss,grain,qualitysenseetc-,whichconsititutedwoodaesthet-icfeeling.Forthisreson,peoplealwaysusedwide]ywoodtomakefurnitureanddecorating,andstlldiedonthequntitativetestingofwoodsurfacevisualphysicalmagnitude.tl-8jTreeswereprocessedoperationbyaseriesofworkingprocesstoformthewoodsurfacewhichwesawandtouchedonfur-nitureanddecorating.Inthesekindsofworkingprocess,whetherthevisualphysi-calmagnitudeofwoodsurfacehadvaria-tionsorthisvariationschangedwoodna…     

Water absorption of boron-treated and heat-modified wood

Heat treatments change the chemical and physical properties of wood and dimensional stability and hygroscopicity are affected as a result of modifications of wood cell components. This study evaluated the water absorption of wood specimens treated with boron compounds followed by heat treatment. Sugi (Cryptomeria japonica D. Don) sapwood specimens treated with either boric acid (BA) or disodium octoborate tetrahydrate (DOT) solutions were heat-modified at either 180° or 220°C for 2 or 4 h. Carbohydrate composition and water absorption of the specimens were then measured and compared with those of untreated and unheated specimens. Wood carbohydrates were significantly degraded in the specimens after heat treatment. The heat treatment evidently decreased the water absorption and the heat-modified specimens absorbed less water than unheated specimens. The higher the treatment temperature and the longer the treatment time, the lower the amount of absorbed water. The boron-treated and heat-modified specimens, however, showed increased water absorption due to the hygroscopic properties of BA and DOT.     

Effects of wood species on degradation rates and bacterial communities in a small-scale biodegradation system for garbage using wood matrices

Simulated organic waste was biodegraded in a laboratory-scale machine using matrices prepared from four wood species to investigate the effects of wood species on the degradation rate and the bacterial community. The degradation rate, estimated by measuring weight loss and CO₂ evolution, was found to be equal among the four wood species. Changes in viable cell counts and microbial communities over time were examined. Viable cell counts were also similar among the wood species, but initial bacterial communities differed owing to differences in wood species, although these communities became similar with time. The sensitivity of isolates to wood extractives was examined using paper discs. The extractive-insensitive bacteria species were dominant at the initial stage of biodegradation. However, occupancy of sensitive bacteria increased with time. It was thought that antibacterial extractives were degraded or inactivated after some time.Part of this report was presented at the 50th annual meeting of the Japan Wood Research Society, Kyoto. Japan, April 2000     

Correlation between charring rate and oxygen permeability for 12 different wood species

The charring rates of 12 different wood species originating from Europe and the tropics with densities ranging from 350 to 750kg/m³ were investigated to obtain clues on their fire resistance behavior. This was done by measuring the thickness of the charred layer after a 30-min exposure to the standard fire ISO 834-1. No correlation was observed between charring rate and density. In search of another physical property that could be used as an indicator of fire resistance, the oxygen permeabilities of the selected wood types were measured. A strong correlation between oxygen permeability perpendicular to the wood fiber direction and charring rate was found, which is quite straightforward given that oxygen is the necessary component to enable smoldering and ignition, both affecting the charring rate. It seems that oxygen permeability is potentially more suitable as a parameter to evaluate the fire resistance of char-sensitive wooden constructions, rather than density. No general preference of the tree ring orientation from 0° (tangential) to 45° and 90° (radial) was found for these measurements. The publication of this article was made possible by an Emachu Research Fund. The authors are grateful for the fund.     

火炬松材性变异及优良种源选择研究

对火炬松不同种源材性变异分析表明,基本密度具有明显的倾群性。美国西南沿海一带各种源基本密度较大,但种源间材性差异不显著,而种源内差异显著;生长与材性相互独立,可以进行生长与材性联合选择。选用生长、材性、适应性及抗性四类１１个数量指标进行主分量和聚类分析,为北亚热带地区选择了不同材种栽植的６个优良种源。     

Effects of five additive materials on mechanical and dimensional properties of wood cement-bonded boards

There is a growing desire to improve the properties and use of nonwood plant materials as supplements to wood materials for wood cement-bonded boards (WCBs). This study was conducted to determine the comparative properties of WCBs containing various amounts of discontinuous inorganic fiber materials, such as alkali-resistant glass fiber, normal glass fiber, mineral wool, and nonwood plant materials such as retted flax straw and wheat straw particles. Tested cement-bonded boards were made at wood/additive compositions of 100/0, 90/10, 80/20, 70/30, 60/40, and 50/50 (weight percentages). Seventy-eight laboratory-scale WCBs were produced. Various board properties, such as the modulus of rupture (MOR), internal bonding strength (IB), water absorption (WA), thickness swelling (TS), and linear expansion (LE), were studied. The test results showed that three types of discontinuous inorganic fiber used as reinforcing materials in composites significantly enhanced and modified the performance of WCBs. The mechanical properties and dimensional stability of cement-bonded board were significantly improved with increasing amounts of the additives. MOR and IB were increased; and WA, TS, and LE of boards were reduced by combination with the inorganic fiber materials. The results also indicated that combination with retted flax straw particles only slightly increased the MOR of boards, and wheat straw particles led to marked decreases in all the mechanical properties and the dimensional stability of WCBs.Part of this report was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, April 2000     

Utilization of wood biomass residues from fruit tree branches,evergreen hardwood shrubs,and Greek fir wood as raw materials for particleboard production. Part B. Hygroscopic properties and formaldehyde content

This paper investigates the basic hygroscopic properties and formaldehyde content (FC) of particleboards produced with wood biomass from fruit tree branches and evergreen hardwood shrubs as substitute raw materials for fir particles. One-layer laboratory particleboards with two distinct target densities (0.63 g/cm³ and 0.69 g/cm³) were produced using various mixtures of the above materials. Industrially produced wood particles were also used for comparison purposes. The results showed that the replacement of fir wood (FW) by evergreen hardwood material significantly upgraded board's quality in terms of thickness swelling (TS) and water absorption (WA) (except boards with density of 0.63 g/cm³) after immersion in water for 24 h and residual swelling (RS) after reconditioning. The contribution of branch-wood (BW) particles in the production of FW boards with density of 0.63 g/cm³ induced increase of TS, WA, and RS while for boards with density of 0.69 g/cm³ did not result to significant changes except for RS. In terms of FC, boards made of BW and evergreen hardwood showed significantly lower FC compared to those produced by FW and industrial particles.     

Effect of annual rings on abrasive wear property of wood

In this study we investigated the abrasive wear property of Douglas fir (Pseudostuga menziesii Franco) on abrasive paper using test specimens with various dimensions and annual ring widths. The effect of the annual rings on the abrasive wear property of Douglas fir was clarified from the relation with the compression strength of the wood specimens. The dispersion of the wear coefficient, which was calculated as the wear volume divided by the friction distance and the load applied to the friction surface, varied when there were fewer than approximately three annual rings in the specimen, as did the compression strength. As clarified from these results, it was found that the effect of the annual rings on the abrasive wear and compression properties of Douglas fir is closely related to the earlywood/ latewood ratio.Part of this report was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, April 2000     

Effect of stocking on juvenile wood stiffness for three <Emphasis Type="Italic">Eucalyptus</Emphasis> species

The effects of stocking on wood stiffness (MoE) for three Eucalyptus species are quantified using a 6-year-old trial established in New South Wales, Australia. An acoustic time-of-flight tool measured the velocity between two probes in the outerwood, from which the stiffness was estimated. Four stocking levels (714, 1,250, 1,667 and 3,333 sph) were examined. Stiffness varied significantly between all species, with E. cloeziana showing the highest stiffness (14.2–15.7 GPa), followed by E. pilularis (12.2–13.5 GPa) and E. dunnii (10.7–12.6 GPa). There was a stiffness increase (around 11%) between 714 and 1,250 stems/ha for all species but thereafter differences between stockings were not always significant. Trees were also assessed for basic density, dbh, total height, crown area, green crown height and stem slenderness (height/dbh). Only stem slenderness had a significant association (0.41 ± 0.17) with stiffness. These findings suggest that, where stiffness is a priority, forest managers could reduce establishment costs with low stockings (around 1,250 stems/ha).