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1.
Strength performance of mortise and loose-tenon furniture joints under uniaxial bending moment 总被引：2，自引：0，他引：2
We determined the effects of adhesive type and loose tenon dimensions （length and thickness） on bending strength of T-shaped mor- tise and loose-tenon joints. Polyvinyl acetate （PVAc） and two-component polyurethane （PU） adhesives were used to construct joint specimens. The bending moment capacity of joints increased significantly with increased length and thickness of the loose tenon. Bending moment capacity of joints constructed with PU adhesive was approximately 13% higher than for joints constructed with PVAc adhesive. We developed a predictive equation as a function of adhesive type and loose tenon dimensions to estimate the strength of the joints constructed of oriental beech （Fagus orientalis L.） under uniaxial bending load. 相似文献
2.
基于Abaqus有限元分析,对不同榫长的实木榫卯连接梁柱节点和榫长为75 mm的不同层数的正交胶合木(CLT)榫卯连接梁柱节点进行数值模拟,分析其受力状态并提取荷载-位移曲线,与使用金属连接件连接的梁柱节点承载力进行对比,探究将榫卯连接应用在现代木结构中的理论依据。研究表明:竖向荷载作用下,榫长75 mm的榫卯连接梁柱节点承载能力处于M8和M10螺栓连接梁柱节点的理论承载力之间;当榫长增大时,节点的最大承载力逐渐提高,榫长150 mm的榫卯节点承载力已经略微超过M12螺栓连接时的理论承载强度,说明榫卯连接梁柱节点在承载能力上可以满足现代木结构建筑的使用要求。由于榫卯节点的承载力主要受到顺纹抗压强度的影响,因此相比于实木连接榫卯节点,CLT榫卯节点的承载力无显著提高。 相似文献
3.
Andrea Frangi Marco Bertocchi Sebastian Clau? Peter Niemz 《Wood Science and Technology》2012,46(5):793-812
Finger joints are commonly used to produce engineered wood products like glued laminated timber beams. Although comprehensive research has been conducted on the structural behaviour of finger joints at ambient temperature, there is very little information about the structural behaviour at elevated temperature. A comprehensive research project on the fire resistance of bonded timber elements is currently ongoing at the ETH Zurich. The aim of the research project is the development of simplified design models for the fire resistance of bonded structural timber elements taking into account the behaviour of the adhesive used at elevated temperature. The paper presents the results of a first series of tensile and bending tests on specimens with finger joints pre-heated in an oven. The tests were carried out with different adhesives that fulfil current approval criteria for the use in load-bearing timber components. The results showed substantial differences in temperature dependant strength reduction and failure between the different adhesives tested. Thus, the structural behaviour of finger joints at elevated temperature is strongly influenced by the behaviour of the adhesive used for bonding and may govern the fire design of engineered wood products like glued laminated timber beams. 相似文献
4.
Finite element analysis of stress and strain distributions in mortise and loose tenon furniture joints 总被引：1，自引：0，他引：1
We studied the effect of loose tenon dimensions on stress and strain distributions in T-shaped mortise and loose tenon （M＆amp;LT） furni-ture joints under uniaxial bending loads, and determined the effects of loose tenon length （30, 45, 60, and 90 mm） and loose tenon thickness （6 and 8 mm） on bending moment capacity of M＆amp;LT joints constructed with polyvinyl acetate （PVAc） adhesive. Stress and strain distributions in joint elements were then estimated for each joint using ANSYS finite element （FE） software. The bending moment capacity of joints increased significantly with thickness and length of the tenon. Based on the FE analysis results, under uniaxial bending, the highest shear stress values were obtained in the middle parts of the tenon, while the highest shear elastic strain values were estimated in glue lines between the tenon sur-faces and walls of the mortise. Shear stress and shear elastic strain values in joint elements generally increased with tenon dimensions and corre-sponding bending moment capacities. There was consistency between predicted maximum shear stress values and failure modes of the joints. 相似文献
5.
J. Smardzewski 《Wood Science and Technology》2002,36(3):213-227
Gluing of wood is among the most effective methods for the permanent joining of furniture elements or building woodwork manufactured
from wood. Technological errors occurring during the preparation process of the glue material may lead to variations in the
strength of adhesive/wood joints. The purpose of the described research project was to investigate the effect of the heterogeneity
of the glue bond on the distribution of tangential stresses in furniture joints, especially the effect of gas cavities, faulty
glue bonds and glue outflows on the distribution of tangential stresses in adhesive bonded overlap, cross and angle wood joints.
Using developed numerical models, it was shown that shear stresses in bonds of cross and angle joints reach their maximum
values in corners of joints. The torsion center of cross joints is situated in the geometrical center of the bond, while in
angle joints – it is found half-way through the length of one of the perpendicular edges of the joint. It was also proven
that gas cavities present in the glue bond contribute to increased stresses in the neighbourhood of the source of heterogeneity.
This phenomenon initiates a process of de-cohesion and, hence, reduces the overall strength of the joint. Faulty gluing, similar
to gas cavities, constitutes a potential source of stress-breaking processes and reduces the strength of joints. On the other
hand, glue outflows present in wood bonds increase their strength by expanding the initiation threshold of fractures even
in situations where technological heterogeneity of the glue bond occurs. In furniture constructions as well as in large-size
building woodwork constructions or, wherever grace and elegance of the finished product is of lesser importance, glue outflows
can be treated as a positive and desirable phenomenon.
Received 13 March 1999 相似文献
6.
采用铜氨(胺)季铵盐(ACQ-D)防腐剂处理马尾松木材,以水性高分子异氰酸酯(API)、聚氨酯(PUR)和间苯二酚-苯酚-甲醛树脂(RPF)为胶黏剂制备防腐材胶合试样,研究胶黏剂种类和防腐剂处理浓度对马尾松胶合强度的影响。结果表明:API、PUR、RPF适用于ACQ处理马尾松的胶合,平均剪切强度和木破率均达到GB/T 26899—2011《结构用集成材》要求。胶黏剂种类对防腐材胶合强度有显著影响,表现为PUR和RPF的剪切强度优于API。与未处理材相比,ACQ处理对API胶合有负面影响,对PUR胶合有增强效应,对RPF胶合没有显著影响。在ACQ浓度为0.1%～1.0%范围内,胶合强度没有显著变化。 相似文献
7.
D. Mannes S. Sanabria M. Funk R. Wimmer K. Kranitz P. Niemz 《Wood Science and Technology》2014,48(3):591-609
In this work, the sorption and moisture diffusion behaviour of historically relevant glutin-based adhesives (i.e. bone glue, hide glue, fish glue) is characterized. The adhesive’s sorption isotherms were assessed on thin film samples revealing fundamental differences between the glutin-based adhesives and the synthetic reference adhesive (polyurethane). Furthermore, the water vapour diffusion parallel to the fibre was examined by means of neutron imaging on bonded two-layer samples of Norway spruce wood. In contrast to previous studies using neutron imaging, a new evaluation approach is presented, which allows for nonzero initial moisture conditions and takes into account and compensates for the geometry changes in the sample caused by swelling and shrinkage, thus allowing for a characterization of the diffusion behaviour within the glue line. The diffusion coefficients determined with neutron imaging were interpreted in terms of a theoretical model which takes into account the glue line microstructure. Although the diffusion coefficients were on average larger values for the glutin-based adhesives compared to the reference polyurethane adhesive, the significant variation observed in the sorption measurement is not reflected. This can partially be ascribed to excessive penetration of the adhesives into the wood substrate in fibre direction, which impedes a continuous adhesive layer. Furthermore, deformation and densification of the wood structure was assessed in the vicinity of the adhesive joint. This effect can be ascribed to the surface roughness, which results in very high local stresses leading to buckling and deformation of the tracheids. This situation is similar to that found for adhesive joints in or close to the fibre direction such as finger or butt joints. 相似文献
8.
Application of cure-accelerated phenol-formaldehyde (PF) adhesives for three-layer medium density fiberboard (MDF) manufacture 总被引：3，自引：0，他引：3
This study was conducted to optimize hot pressing time and adhesive content for the manufacture of three-layer medium density
fiberboard (MDF) through the cure acceleration of phenol-formaldehyde (PF) adhesives by adding three carbonates (propylene
carbonate, sodium carbonate, and potassium carbonate) in the core layer. Carbonate type, carbonate level, PF resin content,
and hot pressing time were evaluated on the basis of the performance of MDF panels prepared. The application of cure-accelerated
PF adhesives by the addition of propylene carbonate reduced both PF resin content and total hot pressing time by 38% and 29%,
respectively, for the manufacture of quality three-layer MDF panels (19.1 mm thickness) under the hot-pressing temperature
of 205 °C. The optimum concentration of propylene carbonate for cure acceleration of PF resin was found to be 3 wt% by weight
based on the resin solids. Bending properties, on one hand, were independent of carbonate type and level, and complied with
the minimum requirements by ANSI. Internal bond (IB) strength, on the other hand, was closely related with carbonate types
and level used.
Received 13 March 1999 相似文献
9.
Summary This paper describes a modelling approach to predict the behaviour of an elementary thin timber bolted joint. The application
concerns principally joints with steel side members; bolts have a constant 12 mm diameter with two ratios of end distance
to bolt diameter and two bolt clearances. The behaviour of the bolted joints is characterized by a double non linearity; the
first one is due to the contact area evolution between the bolt and the hole of the jointed elements. The second one is owing
to the evolution of plasticity on the wood. A spring element compatible with isoparametric plane finite elements represents
the contact evolution. The elastic-plastic wood is provided with a plastic flow rule according to the Tsa? criterion. This
study allows an investigation on the parameters characterizing the Tsa? criterion, particularly F12 which represents the interaction between the principal axis of orthotropy. A two-dimensional model is used. It permits the
assessment of the clearance bolt, joint dimensions, wood plasticity and wood grain angle effect on the joint behaviour. The
wood grain angle has a non negligible effect on the plastic strains distribution and it can create a parasite loading because
the joint tends to rotate even for an axial loading. The results showed a good agreement between experimental values given
by some authors and numerically-predicted stresses on the joint. So, the applications concern a two-dimensional joint with
anisotropic plastic material. The generalization in the three-dimensional modelling is desirable to take into account the
interaction between the wood and a metallic fastener in thick joints with different geometric characteristics. 相似文献
10.
Ryuya Takanashi Kei Sawata Yoshihisa Sasaki Akio Koizumi 《Journal of Wood Science》2017,63(2):192-198
Nailed timber joints are widely used in timber structures, and their deterioration may cause significant damage. We investigated the withdrawal strength of joints using steel wire nails in specimens exposed to a brown-rot fungus. We also examined the effects of nail corrosion on withdrawal strength, because high humidity conditions accelerate not only wood decay but also the corrosion of nails. We found that nail corrosion increased the withdrawal strength. The ratios of withdrawal strength of nailed joints with rusted nails to that of joints with a minimally rusted nails were 1.47 and 1.56 in joints nailed in radial and tangential directions to annual rings, respectively. Withdrawal strength, excluding the effects of nail corrosion, had a negative correlation with mass loss and Pilodyn-pin-penetration-depth-ratio. We estimated the withdrawal strength of the nailed joint with decayed wood and rusted nails by multiplying the values from the empirical formula (obtained from mass loss and Pilodyn-pin-penetration-depth-ratio) by 1.47 and 1.56 for joints nailed in radial and tangential direction to annual rings, respectively. 相似文献
11.
《Wood material science & engineering》2013,8(4):185-189
Abstract One of the main disadvantages of wood is hygroscopicity resulting from its polar character. The sorption–desorption of water causes unwanted swelling and shrinkage in wood. Thermal modification substantially reduces this inconvenient feature. Unfortunately, the same chemical changes that reduce water sorption alter the polar character of the material and result in poorer wetting of thermally treated wood by waterborne adhesives. Gluability of thermally modified beech (Fagus silvatica L.) and birch (Betula pubescens Ehrh.) wood with two commercial amino resins, melamine–urea–formaldehyde (MUF) and melamine–formaldehyde (MF), and a two-component polyurethane (PUR) adhesive was investigated. Both wood species were modified according to two temperature regimes: 160°C and 190°C. Shear strengths of the joints were then determined according to EN 205:2003 standard. The results showed that thermally modified beech and birch wood can be effectively glued not only with commercially available PUR adhesives, but also with aqueous MF and MUF resins. The resultant shear strengths of the joints were limited by the strength of the thermally modified substrate. 相似文献
12.
Antonio Pantaleo Domenico Ferri Achille Pellerano 《Wood material science & engineering》2016,11(1):25-35
The research focuses on the assessment of the performances of glued laminated wood corner joints for outdoor window profiles applications, proposing a methodology to appreciate the strength of 90° tenon mortise corner joints. The rationale relies on the potential damage (i.e. breaking of the frame) that can be caused by poor glueing processes and/or typology of adhesives. There is a number of standards for assessment of wood-adhesive bonds for outdoor windows; however, there is a lack of specific standards related to glueing assessment for outdoor wood frames, which can take into account all the factors influencing the glueing quality. The proposed methodology was tested on red oak window profiles. A commercially available polyvinyl acetate-based adhesive was used for corner joints. Bending strength of 90° tenon mortise corner joints was measured and compared with maximum admissible loads on the frame to limit its deformations within admissible ranges. The test results show that the 90° tenon mortise corner joints strength exceeds the admissible load to preserve the functionality of the frame. In order to appreciate the influence of conditioning processes on adhesion, shear strength tests of the flatwise glued joint samples (bond lines of lamellae) were carried out after different conditioning processes. 相似文献
13.
14.
The strength prediction of adhesively bonded timber joints is difficult due to the anisotropic and brittle nature of the adherends, the complex stress distribution as well as the uncertainties regarding the associated material resistance. This paper describes a probabilistic method for the strength prediction of balanced double lap timber joints. The method considers the statistical variation and the size effect in the strength of timber using a Weibull statistical function. The design method presents an explanation for the increased resistance of local zones subjected to high stress peaks as it takes into account not only the magnitude of the stress distributions, but also the volume over which they act. The predicted joint strengths are slightly underestimated compared with the experimental results due to inaccurate upper tail modelling of the material strength by the Weibull statistical distribution. The probabilistic method provides reasonable results for brittle joint failure and has immediate application in the design of adhesively bonded timber joints. 相似文献
15.
《Wood material science & engineering》2013,8(2):88-98
ABSTRACTA glued-in rods' connection is generally constituted by a group of steel bars bonded by an adhesive into timber elements. In the past, most of the research focused on single-rod connections, in order to exploit the maximum resistance of the connection without accounting for interaction among bars or splitting failure in the timber member due to close edge distances or spacing between bars. Such interaction problems arise when dealing with multiple rods, thus requiring specific investigation to fully understand the behavior of the connection as a whole and to determine its capacity. In both cases, existing test procedures determine bond strength in specific geometrical configuration. The paper aims to determine the pull-out strength of single and multiple axially loaded steel rods bonded in glulam parallel to the grain differentiating the adhesive failure from the other failure modes. After an initial review of typical applications and existing design procedures, test results on single rod with confined or unconfined test setup on single rod at different embedment depths are presented and discussed, indicating that the confinement has a negligible influence on the pull-out capacity. Subsequently, interaction between bars is investigated by a specific unconfined configuration. The accounted parameters are the embedment depth of the bars, the dimensions of the timber section, and the spacing between bars. Results are discussed and compared with three-dimensional numerical simulations. Both experimental and numerical results suggest that the critical value at which the transition from pull-out to timber-related failure is observed depends on the mechanical properties of the timber and on the properties of the adhesive, such that a single value of spacing should not be provided in design standard if the full capacity of the adhesive is to be exploited. 相似文献
16.
浅谈木材用胶粘剂的发展 总被引：3，自引：0，他引：3
介绍了胶粘剂的概念、组成、种类以及人造板工业中用得最多的三种胶粘剂：脲醛树脂、酚醛树脂和三聚氰胺树脂，阐明了天然胶的复苏情况和生物技术利用在木材胶粘剂的现状，并对木材胶粘剂的发展趋势进行了展望。 相似文献
17.
Ali Awaludin Takuro Hirai Toshiro Hayashikawa Yoshihisa Sasaki Akio Oikawa 《Journal of Wood Science》2008,54(2):114-120
The adoption of a concept similar to the prestressing technique used in laminated wood decks of bridge structures might increase
the initial stiffness or ultimate resistance of dowel-type timber joints by applying pretension to their bolts. This study
investigated the effect of pretension in bolts on hysteretic responses and ultimate properties of moment-carrying timber joints
with steel side plates. A pretension of 20 kN that yielded a prestress level of 1600 kPa or about 90% of the allowable long-term
end-bearing strength of spruce species was applied to the bolts of prestressed joints. The superiority of the prestressed
joint over the non-pre-stressed joint was proved by very high hysteretic damping, equivalent viscous damping ratio, and cyclic
stiffness. At any given rotation level, hysteretic damping reduction and moment resistance decrement due to continuously reversed
loads were found to be small because bolt pretensioning minimized the pinching effect. This study showed that the hysteresis
loop of the prestressed joint can be obtained by adding the frictional hysteresis loop due to pretension force into the hysteresis
loop of the non-pre-stressed joint. Despite a great increase of initial stiffness, only slight increments in ductility coefficient
and ultimate moment resistance were found in the prestressed joint. 相似文献
18.
采用高强度玻璃纤维对竹环氧集成材进行改性试验。结果表明:当采用热压压力为1.4 MPa、玻璃纤维均布密度为7.5 mm/根、热压时间为1.0 min/mm(厚)、热压温度为145℃的生产工艺,环氧集成材压缩强度最佳;当采用热压压力为1.4 MPa、玻璃纤维均布密度为5.0 mm/根、热压时间为1.2 min/mm(厚)、热压温度140℃的生产工艺,环氧集成材层间剪切性能最佳。 相似文献
19.
Bending moment resistance of dowel corner joints in case-type furniture under diagonal compression load 总被引：1，自引：0，他引：1
We investigated bending moment resistance under diagonal compression load of corner doweled joints with plywood members. Joint members were made of 11-ply hardwood plywood of 19 mm thickness. Dowels were fabricated of Beech and Hornbeam species. Their diameters(6, 8 and 10 mm) and depths of penetration(9, 13 and 17 mm) in joint members were chosen variables in our experiment. By increasing the connector's diameter from 6 to 8 mm, the bending moment resistance under diagonal compressive load was increased, while it decreased when the diameter was increased from 8 to 10 mm. The bending moment resistance under diagonal compressive load was increased by increasing the dowel's depth of penetration. Joints made with dowels of Beech had higher resistance than dowels of Hornbeam. Highest resisting moment(45.18 N·m) was recorded for joints assembled with 8 mm Beech dowels penetrating 17 mm into joint members Lowest resisting moment(13.35 N·m) was recorded for joints assembled with 6 mm Hornbeam dowels and penetrating 9 mm into joint members. 相似文献
20.
用ＵＦ、ＭＵＦ胶制作三种松木胶合板，分别就单板厚度、涂胶量及抽提物含量对胶合性能的影响，松木与柳安混合树种组坯、特殊添加剂对改善胶合性能的作用进行了研究。结果表明：除了老挝松边材ＭＵＦ胶合板以外，１．５和２．０ｍｍ厚的单板胶合强度均达到或超过日本ＪＡＳ普通胶合板的要求。合板胶合强度随单板厚度增加而下降，在一定范围内增加涂胶量可以提高合板胶合强度，混合组坯及施加特殊添加剂具有改善松木单板胶合性能的作用。 相似文献