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1.
《Wood material science & engineering》2013,8(3):188-197
Abstract Joints are generally the weakest part of furniture and they are primary cause of failure. To ensure durability and performance of furniture, it is important for a designer to understand the stresses acting on the joints for preparing suitable design and specification of a furniture. Since each type of joint is unique in construction, it is important to know their strength, when subjected to various stresses namely shear, bending, and tensile, by testing the joints. Since there is no established test method for joints, this study was carried out to categorize joints based on their shape, identify the stresses acting over them and develop test methods for testing furniture joints in three modes namely shear, bending, and tension, which are required for designing joints of any furniture and also provide means of comparing strength of different types of joints. Different types of furniture joints were taken for the study and were classified based on their shapes such as L-shaped, T-shaped, straight, and corner joints. Six types of jigs (one type for bending, two types for shear, and three types for tension) were designed and developed for testing the joints, in such a way that any type of joint can be tested in three modes, i.e., bending, shear, and tension using a universal testing machine. The criteria for section of jigs for performing tests on joints, based on their shape and stresses acting on a particular joint, were reported. Tests were carried out using all the six type of jigs to check the suitability of jigs and test methods developed in the study. 相似文献
2.
Takuro Hirai Takeyoshi Uematsu Yoshihisa Sasaki Masahiko Toda 《Journal of Wood Science》2013,59(6):477-483
In this study, dynamic tests of nailed plywood-timber joints are conducted under a band-limited white-noise wave using a uniaxial hydraulic shaking table. The principal results are as follows: dynamic responses of nailed plywood-timber joints under a band-limited white-noise wave are reasonably related to the static load-slip relationships and the dynamic responses under harmonic waves of them. When nailed plywood-timber joints are shaken under a composite wave of wide frequency range, they resonate transitionally with one of the frequency components one after another decreasing their equivalent resonant frequencies along their static load-slip curves. Nailed plywood-timber joints are in danger of ultimate failures even though the input maximum accelerations do not exceed their damage limits, if they are shaken for long times with or without intermittences. In this case, nailed plywood-timber joints are prone to fail in low-cyclic bending fatigue failure of nails. Nailed plywood-timber joints, on the other hand, are prone to fail in typical static failure modes when they are shaken under strong input maximum accelerations equivalent to their ultimate limits. 相似文献
3.
Anna Pousette 《Journal of Wood Science》2006,52(4):358-362
Joints in traditional wooden stairs can be constructed in many different ways. Connections between tread and string are commonly
made with tenons and screw joints. It is often hard to know which joint rigidity should be used in calculations. To study
this type of stair, a total of 12 small straight stairs with three steps each were tested. The stairs were loaded and the
deformation was measured. Modeling of the stairs with a finite element program was also performed, using linear elastic models
in the analysis. The conclusion derived from the study is that the tested tread-to-string connections are not very rigid.
Tolerances and accuracy of manufacture of the stair parts are important for the behavior of the joints. Comprehensive knowledge
about stair joints can be used for development of new cost-effective and reliable design tools for stairs. In a computer program
for stair design based on beam elements, the treads in this type of staircase should, according to this study, preferably
be calculated as being hinged to the string, or else the rigidity of the joint should be a function of joint parameters. 相似文献
4.
5.
The beams and columns in Chinese ancient wooden buildings were connected with mortise–tenon joints, which are semi-rigid due to the friction and squeezing deformation between mortise and tenon. In this paper, a friction constitutive model for the friction behavior between mortise and tenon was proposed based on the modern frictional theory. A series of surface topography and hardness tests were conducted to obtain some parameters used in the friction constitutive model. A finite element (FE) model of a Chinese ancient wooden frame with mortise–tenon joints under reversed cyclic loading was performed based on the proposed friction constitutive model, and a FE model using a constant friction coefficient was also carried out. Experimental results were used to validate the results modeled by the two models, and better agreement of the proposed model was observed. 相似文献
6.
通过对欧式木窗推台铣床主轴的模态分析,研究了该主轴的在实际应用中会发生的几个临界频率及在激振频率下发生的位移量。经过计算验证了该主轴的实用性,并对提高主轴单元动态性能提出了相应的措施。 相似文献
7.
Pseudodynamic (PSD) lateral loading tests were conducted on conventional post and beam timber frames with plywood-sheathed
shear walls to validate the dynamic model of wall panels, each with an opening of a different configuration. The lateral forces
were applied step by step at the top of the wooden frames by the computer-controlled actuator, and the displacement response
for the next step was computed on the basis of the input accelerogram of the 1940 El Centro earthquake scaled up to 0.4g. The test results were compared with those of the lumped mass time-history earthquake response analysis using the hysteresis
model with pinching. The results of the dynamic analysis with this global model consisting of the envelope curves, unloading
and reloading with pinching agreed well with the experimental results of the PSD tests of this type of earthquake record.
Some parametric studies may be necessary, however, to validate the model with different earthquake records. The hysteretical
parameters obtained in this study showed similar values for each of the wall panels with different opening configurations.
This makes it possible to use the model and parameters for the plywood-sheathed shear walls to estimate the dynamic behavior
of entire structures without conducting expensive PSD tests or shaking table tests. 相似文献
8.
The purpose of this study was to investigate the toxicity of combustion gases from burning wooden materials. The toxicant index and mice exposure experiment were used to evaluate the toxicity index. The time taken to incapacitate mice under the impact of burning 19 solid wood species and 7 kinds of plywood were investigated. The results showed that the toxicity index of burning solid wood ranged from 1.5 to 2.5, and its main toxicant was CO2. The toxicant index of burning plywood was higher, ranging from 3.0 to 6.0, and its main toxicity was NOx. A good correlation was observed between the time taken to incapacitate mice (Xs) and the weight loss rate of burning solid wood. When the concentration of CO was higher than 1% in the exposure chamber, the mice stopped their activity within 2min. The time taken to incapacitate mice (Xs) and the minimum concentration of O2 in the exposure chamber could be represented by a positive linear regression formula. The concentrations of O2 and CO2 exhibited a positive effect and the concentration of CO had a negative effect on the Xs values of mice.Part of this paper was presented at the 52nd Annual Meeting of the Japan Wood Research Society, Gifu, April 2002 相似文献
9.
Takafumi Nakagawa Masamitsu Ohta Takahiro Tsuchimoto Naohito Kawai 《Journal of Wood Science》2010,56(4):284-292
In this study, we developed a new analysis method that enables numerical simulations of the collapse process of real-size
wooden houses and evaluated the accuracy thereof by carrying out numerical simulations by shaking table tests. The distinct
element method was adopted as the basic theory of our numerical analysis. This research is the first approach in which the
extended distinct element method was used for Japanese timber post-and-beam construction. The size of the analysis model is
a 5.5 m × 5.5 m, two-story real-size wooden house. The three analytical models were developed in terms of the strength of
exterior mortar walls. The simulation results were compared with the shaking table test results. One of the collapsing processes
of the numerical simulation corresponds well to the experiment results. Assessment of the possibility of collapse for real-size
wooden houses was determined to be possible using our newly developed numerical analysis method. 相似文献
10.
The crack initiation and propagation of multiplybolted joints subjected to lateral forces perpendicular to the grain were analyzed. Two types of bolted joint were subjected to lateral loads perpendicular to the grain. One had joints of two bolts aligned with the wood grain (type H), and the other had joints of two or three bolts aligned perpendicular to the grain (type V). The crack initiation and propagation were analyzed by means of the average stress method (ASM) and linear elastic fracture mechanics (LEFM), respectively. The maximum loads calculated by LEFM agreed comparatively well with the experimental results, and it was proved that the LEFM was an appropriate tool to analyze the fracture of multiply-bolted joints subjected to a force perpendicular to the grain. It was also found that the multiply-bolted joints failed with the fracture of the wood before the joints yielded, and that it caused a considerable decrease of the maximum loads. The reduction of strength should be considered in the design of multiply-bolted joints subjected to lateral forces perpendicular to the grain.Part of this work was presented at the annual meeting of the Architectural Institute of Japan, Hikone, September 1996 相似文献
11.
Pseudodynamic (PSD) tests were conducted on plywood-sheathed conventional Japanese three-dimensional (3D) wooden structures.
Lateral load was applied to the edge beam of specimen structures to generate eccentricity loading. Specimens were based on
a combination of shear walls with openings in the loading direction and horizontal diaphragms with different shear stiffness.
The principle deformation of the horizontal diaphragm was torsion for rigid diaphragms and shear deformation for flexible
diaphragms. Lumped-mass time-history earthquake response analysis was conducted on the tested structures, and additional calculations
were conducted on structures with different eccentricity rates. Dynamic analyses were conducted by varying the masses and
the resistance of the walls in the loading direction. The simulated peak displacement response in the loading plane agreed
comparatively well with the PSD test results. The maximum displacement response on changing the wall resistant ratio showed
almost the same tendency as that obtained by changing the mass ratio up to an eccentricity rate of 0.3; however, the maximum
displacement response increased markedly beyond an eccentricity rate of 0.4. It was proved that the lumped-mass 3D model proposed
in this study was appropriate for conducting a parameter study on the 3D dynamic behavior of timber structures. 相似文献
12.
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
13.
Motoi Yasumura Takahisa Kamada Yutaka Imura Motoi Uesugi Laurent Daudeville 《Journal of Wood Science》2006,52(1):69-74
Pseudodynamic (PSD) tests were conducted on two-level timber structures with plywood-sheathed shear walls, which each had
an opening of different configuration, to study the effects of the mechanical properties of the first and second levels on
the earthquake response of the structure. The specimens had two-level conventional post and beam frames that were 3 m wide,
3 m deep, and 6 m high with plywood sheathings nailed on one face of the structure. The first and second levels had different
opening configurations of window, door, or slit. Lateral forces were applied at the top of the first and second levels, calculating
step by step the next displacement based on the North-South (NS) components of the 1940 El Centro earthquake. The test results
were compared with those of the time-history earthquake response analysis using the lumped mass model and hysteresis model
presented in the companion article (part I). The experimental and simulated results showed that the simulation by means of
the lumped mass time-history earthquake response analysis predicted quite well the response of the first level, but tended
to underestimate the response of the second level, and that the PSD tests of an individual wall system with the mass supported
by that particular wall generally show a conservative estimate of the response. 相似文献
14.
Romualdas Juknys Algirdas Augustaitis Jone Venclovienė Almontas Kliučius Adomas Vitas Edmundas Bartkevičius Nerijus Jurkonis 《European Journal of Forest Research》2014,133(4):713-724
Long-term investigations of Scots pine (Pinus sylvestris L.) growth were carried out in the vicinity of one of the biggest air pollution sources in Lithuania—mineral fertilizers plant “Achema.” It is detected that initial stages of the dynamic tree response to the external stress factors in the polluted environment with an increased quantity of nitrogen compounds have started with a stimulation stage, followed by a gradual transition to a depression of growth. The recovery of the damaged stands took place along with the reduced environmental pollution, and the overdraft of the “normal” annual increment was a characteristic feature of all the investigated stands. This phase is still continuing for the most damaged stands. A very high individual variability of the tree growth response to the environmental impact is a characteristic feature of the damaged Scots pine stands. The homeostatic mechanisms of the survived trees stipulated reaching approximately the same or even higher growth rate as prior to the depression period, and the tree growth rate before the depression period can serve as the most powerful predictor of tree growth recovery capacity under the reduced environmental pollution. Crown defoliation is the next most important predictor of individual tree recovery capacity. Lower stand density and lower competition cause higher recovery capacity of damaged trees. The conclusion is made that a reduction in the environmental pollution on the local and regional scale and especially a decrease in emissions and deposition of sulfur and nitrogen compounds caused the recovery of damaged forests. These trends should be taken into account while analyzing and modeling forest dynamics. Interaction of environmental pollution and climatic factors is very important for the response of tree growth to the environmental stressors. 相似文献
15.
In this study heartwood from a Chinese fir [Cunninghamia lanceolata (Lamb.) Hook] plantation was treated using a high-temperature drying (HTD) method at 115°C, a low-temperature drying (LTD)
method at 65°C, and freeze vacuum drying (FVD), respectively. The dynamic viscoelastic properties of dried wood specimens
were investigated. The measurements were carried out at a temperature range of −120 to 250°C at four different frequencies
(1, 2, 5, and 10 Hz) using dynamic mechanical analysis (DMA). We have drawn the following conclusions: 1) the storage modulus
E′ and loss modulus E″ are the highest for HTD wood and the lowest for FVD wood; 2) three relaxation processes were detected in HTD and LTD wood,
attributed to the micro-Brownian motion of cell wall polymers in the non-crystalline region, the oscillations of the torso
of cell wall polymers, and the motions of the methyl groups of cell wall polymers in the non-crystalline region in a decreasing
order of temperatures at which they occurred; and 3) in FVD wood, four relaxation processes were observed. A newly added relaxation
is attributed to the micro-Brownian motions of lignin molecules. This study suggests that both the HTD and the LTD methods
restrict the micro-Brownian motion of lignin molecules somewhat by the cross-linking of chains due to their heating history.
__________
Translated from Journal of Beijing Forestry University, 2008, 30(3): 96–100 [译自: 北京林业大学学报] 相似文献
16.
Sadegh Maleki Akbar Rostampsour Haftkhani Mosayeb Dalvand Mehdi Faezipour Mehdi Tajvidi 《林业研究》2012,23(3):481-490
We determined the effects of the penetration depth and spline material and composite material type as well as joining method on bending moment resistance under diagonal compression and tension in common wood panel structures. Composite materials were laminated medium density fiberboard (MDF) and particle board. Joining methods were buttand miter types. Spline materials were high density fiber board (HDF).The penetration depths of plywood, wood (Carpinus betolus) and splinewere 8, 11 and 14 mm. The results showed that in both diagonal compression and tension, MDF joints are stronger than particle board joints,and the bending moment resistance under compression is higher compared with that in tension. The highest bending moment resistance under tension was shown in MDF, butt joined using plywood spline with 8 mm penetration depth, whereas under compression bending moment resistance was seen in MDF, miter joined with the HDF spline of 14 mm penetration depth. 相似文献
17.
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
18.
The performance of plywood-sheathed shear walls is determined at the plywood-to-timber joints. In joints with dowel-type fasteners, such as nails and screws, the fastener is fractured under reversed cyclic loading (e.g., seismic force), reducing the ductility of the joint. The fracture is caused by low-cycle fatigue due to the reversed cyclic bending of the fastener. Therefore, evaluating the fatigue life is important for estimating the ultimate displacement. The main objective of this study is to estimate the ultimate displacement of the joints and to enable load–displacement calculation of single shear joints under reversed cyclic displacement when bending fatigue failure of the fastener occurs. Single shear tests were conducted under different loading protocols, and the damage performances of the fasteners were determined by subjecting them to reversed cyclic bending tests. Based on the results, the failure lifetimes of joints with dowel-type fasteners were estimated. In addition, the fracture mechanism of these dowel-type fasteners was elucidated. CN50-type nails and wood screws with dimensions of 4.1?×?38 and 4.5?×?50 mm were used as fasteners. The single shear tests showed that the smaller the displacements per cycle, the lower are the ultimate displacement and ductilities of the joints. Moreover, load–displacement relationship up to fastener failure can be approximately estimated by combining the yield model and failure lifetime. 相似文献
19.
Germar Eisenacher Robert Scheidemann Martin Neumann Bernhard Droste Holger Völzke 《Wood Science and Technology》2013,47(2):369-380
An extensive series of large deformation crushing tests with spruce wood specimens was conducted. Material orientation, lateral constraint and loading rate were varied. Regarding material orientation, a reduction in the softening effect and the general force level was observed with a higher fiber-load angle. A comparison with characteristics gained by application of Hankinson’s formula showed discrepancies in compression strength and the beginning of the hardening effect. Lateral constraint of the specimens caused a multiaxial stress state in the specimens, which was quantified with the applied measuring method. Further, a higher force level compared to specimens without lateral constraint and significant hardening effect at large deformations resulted. Thus, the influence of a multiaxial stress state on the force level could be determined. An increase in the loading rate led to higher force levels at any displacement value and material orientation. 相似文献