实木家具的拆装式结构实现路径探究

遵循结构合理、体积缩小、组装方便、外形美观的设计原则,从拆装式节点实现形式、整体结构拆装方式二个维度系统阐述了实木家具拆装结构实现路径,并对榫自锁可拆式、连接件可拆式两种实木家具拆装式节点形式及椅类、桌台类、柜类、床类家具的整体结构可拆装方式进行了详细介绍,以期为实木家具的结构优化及平板化包装提供思路。     

实木家具斜角接合结构的可拆装设计与评估北大核心

以现代实木家具中常见的45°斜角接合结构为研究对象,以实现斜角接合结构可拆装,提高其接合强度为目的,分析了现有斜角接合结构的特征与不足,提出一种通过五金连接件与分体榫相结合的45°斜角可拆装改良方案;采用有限元分析方法,从应力分布角度对现有节点和改良节点进行对比分析;通过力学试验方法测试了两种结构的抗弯力学性能。结果表明:改良方案的极限承载力平均值比现有方案高18.7%,通过有限元分析方法获得的节点应力云图与试验中试件的破坏形式具有较好的一致性。改良方案实现了斜角接合节点的可拆装,提高了实木家具斜角接合节点的强度,为后续进一步开发实木家具隐藏式五金连接件及榫卯外观下的节点可拆装设计提供了依据及实现方法。     

有限元法在实木榫接合家具结构设计中的应用

文中从实木榫接合家具节点、构件和整体框架3个层面，总结、分析有限元法在实木榫接合家具结构设计中的应用现状，并对该领域存在的主要问题及未来研究趋势进行了阐释。目前主要存在以下问题:1）未形成系统性的有限元分析方法，不同研究者之间存在较大差异；2）分析准确度不高，大多研究仅为有限元软件的模拟分析，缺乏试验验证；3）未建立合理的榫接合节点有限元模型，通常将榫接合节点视为刚性节点处理。未来研究可围绕以下几方面开展:1）榫接合节点有限元模型的建立方法及简化方法；2）实木榫接合家具疲劳寿命的有限元分析方法；3）基于有限元法的实木榫接合家具结构优化设计方法；4）二次开发，在有限元分析软件的基础上，建立实木榫接合家具结构设计模块；5）实木榫接合家具智能设计与制造系统开发。将有限元法应用于实木榫接合家具的结构设计中，将有助于实木榫接合家具的结构优化设计、智能设计与制造。     

现代板木家具新型接合结构设计

通过分析家具设计的时代背景,提出可拆装结构的家具将是未来家具发展方向之一。可拆装板木家具设计的关键在于板材部件和接合方式的设计,通过具体实例的分析和展示,以期为拆装式板木家具发展起到抛砖引玉的作用。     

基于拆装式结构的定制木楼梯扶手结构研究

通过对定制木楼梯扶手特点的分析,明确了可拆装定制木楼梯扶手设计的关键在于扶手部件接合方式的设计,并结合木楼梯在定制家具生产过程中存在的局限性,总结出基于拆装式结构的定制木楼梯扶手结构的设计原则。通过实际案例,对可拆装结构的定制木楼梯扶手设计进行具体分析。将可拆装的理念与定制木楼梯扶手结构相结合,以期满足现代家具定制化生产需求,同时克服了现有木楼梯接合方式安全性和美观性不强的缺陷,为现代家具结构设计与定制生产提供新思路。     

竹集成材用于榫卯家具的CMF评价及力学强度分析北大核心

以竹集成材为载体,通过用户感知觉、设计美学、力学强度3方面评价竹集成材作为榫卯家具用材的适用性。在竹集成材用于榫卯家具的用户感知觉、设计美学评价方面,参考CMF设计方法,将竹集成材色彩特性、材料特性、表面处理加工工艺3方面作为评价内容。以家具腿、扶手等部位常应用的T型榫接合构件为例,通过测试9组不同榫头尺寸配合的竹集成材T型榫接合试件的抗弯强度,计算得到其破坏弯矩,评价榫卯家具的力学强度,探究竹集成材家具榫卯节点力学抗弯强度及榫卯尺寸配合的影响规律。结果表明:竹集成材能够满足用户情感需求,符合榫卯家具设计审美,符合榫卯家具力学强度要求,适用于现代榫卯家具的设计与制造。基于对竹集成材用于榫卯家具的适用性评价,提出线形设计、榫卯减量化设计、可拆装榫卯设计3种符合现代加工生产、设计审美及情感需求的竹集成材榫卯家具设计策略,为榫卯家具的现代化转译设计和缓解木材资源供给压力提供方法。     

椭圆榫接口标准化研究与创新设计

基于现有实木家具构件椭圆榫接合形式,对其进行了评估与创新设计。依据家具产品的标准化原则,设计出一种"台阶式"椭圆榫,并对其制造工艺及接合方式进行探究。结果表明,"台阶式"椭圆榫较常规椭圆榫接口具有高加工效率及较低加工成本等优势。     

圆竹家具新型接合结构设计研究

选择以圆竹家具接合方式作为切入点,从设计开始进行改革,在设计中引入了绿色设计、量产化、可拆装化等概念,并且通过运用借鉴、移植等方法,设计出了4种新型的圆竹家具接合方式,为拆装化的圆竹家具现代化生产提供了新的思路。     

木框斜角榫接合性能研究

在木家具结构设计中,特别是具有中国传统家具风格的实木家具结构设计中,木框角部斜角榫接合强度是人们既关注又无法回避的问题。抗拉强度和抗弯强度是衡量木框斜角榫接合性能高低的两个重要指标。笔者对三种常用的、易于机械加工的斜角榫接合试件的强度(抗拉强度,抗弯强度)进行了实验测定,并从各个方面对其进行比较、分析。研究结果表明:斜角榫接合形式,胶黏剂种类,加压时间等各个因子都不同程度地影响着木框角部接合的整体结构性能。单肩斜角明榫接合效果最好。     

速生松木家具几种节点接合方式的强度比较研究

以南方速生脱脂马尾松松木为基材,以"L"型和"T"型构件为基本构件形式,采用力学实验方法 ,对理想使用状态——即在外力垂直荷载匀速加载的作用下使构件节点发生破坏或变形,测试构件节点破坏强度值及其破坏或变形形式。实验针对8种不同框架节点接合方式(贯通直角单榫接合、不贯通直角暗榫接合、双圆榫接合、倒刺螺母连接件接合、双圆榫与倒刺螺母共同接合、三件式偏心连接件接合,以及45°双圆榫斜角接合和45°不贯通榫斜角接合)的接合强度进行测定。实验结果表明:(1)对于直角连接构件,采用贯通直角单榫接合时的节点接合强度最大;双圆榫与倒刺螺母共同连接的节点接合强度次之;然后强度值从高到低依次为双圆榫接合、倒刺螺母螺杆连接件接合、不贯通直角单榫接合,接合强度最小的是偏心连接件接合;(2)对于45°斜角连接构件,采用45°不贯通榫斜角接合的节点强度大于45°双圆榫斜角接合的节点强度;(3)在相同条件下,"T"型实木构件的节点接合强度总体上大于"L"型实木构件的节点接合强度。研究表明:节点处的基本构件形式("L"型或"T"型)、角部构件的连接形式(直角构件或斜角构件),以及节点的接合方式等都不同程度地影响着马尾松松木家具框架节点的接合强度。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。