Tenon Joints Research Articles

3D Printing Application in Wood Furniture Components Assembling.

Additive manufacturing (AM) is used in many fields and is a method used to replace wood components or wood-jointed furniture components in the furniture industry. Replacing wood joints by 3D printed connectors would be an advantage, considering the fact that during the process of assembling furniture, the execution technology of the joints is difficult, time-consuming, and labor-intensive. Advanced technology of AM applied in furniture manufacturing helps the designers to create new concepts of product design, with no limits of shape, number of joints, color, or size. The diversity of 3D printers and AM technologies provides the selection of materials in relation with the applicability of the 3D printed object. In this respect, the objective of the present research is to design a 3D printed connector to be used for jointing three chair components, namely the leg and two stretchers made from larch (Larix decidua Mill.) wood, and to use reinforced polylactic acid (PLA) fiberglass (20 wt. %) filament for 3D printing this connector using AM with fused filament fabrication (FFF) technology. The design of the connector, the possibility of using this type of material, and the deposition method of filament were investigated in this research. For this purpose, several evaluation methods were applied: microscopic investigation with 50×, 100×, and 200× magnifications, both of the filament and of the 3D printed connector; mechanical testing of corner joint formed with the help of connector between chair leg and the two stretchers; and a microscopic investigation of the connectors’ defects that occurred after applying the compression and tensile loads on the diagonal direction of the L-type joint. The microscopic investigation of the composite filament revealed the agglomerations of glass fibers into the core matrix and areas where the distribution of the reinforcements was poor. The heterogeneous structure of the filament and the defects highlighted in the 3D printed connectors by the microscopic investigation contributed to the mechanical behavior of L-type connecting joints. The bending moments resulting from compression and tensile tests of the 3D printed connectors were compared to the results recorded after testing, under the same conditions, the normal mortise–tenon joint used to assemble the abovementioned chair components. The larch wood strength influenced the mechanical results and the conclusions of the microscopic investigations, as well as the analysis of the broken connectors after testing recommended the change of connector design and filament deposition direction.

Diagonal Tension Performance of Impregnated Woodworking Corner Joints

In this study, the effects were examined of wood species, processing types and processing time on diagonal tension performance of woodworking corner joint with double tenon and mortise. Test samples were prepared by using Scots pine (Pinus sylvestris Lipsky), sessile oak (Quercus petreae Lipsky) and black locust (Robinia pseudoacacia L.). Poly vinyl acetate (PVAc) adhesive was used to join the tenon and mortise corner joints. The samples were impregnated by using the method of immersion for 20 and 40 min with a mixture of wax / linseed oil (3 % paraffin, 10 % linseed oil, 87 % white spirit) and Imersol-Aqua. The test of diagonal compression was used to test 120 samples. In this study, the minimum strength decrease of around 68 % was obtained for Scots pine impregnated with Imersol-Aqua for 40 min and the highest strength increase of around 10 % was obtained for sessile oak samples impregnated with Imersol-Aqua for 40 min. The highest diagonal tension performance of 879.734 N·m was obtained for oak samples impregnated with Imersol-Aqua for 40 min., the lowest diagonal tension performance of 189.111 N·m was obtained for Scots pine samples impregnated with Imersol-Aqua for 40 min.

Multiaxial thermo-mechanical fatigue life prediction based on notch local stress-strain estimation considering temperature change

The modified incremental multiaxial Neuber rule by considering the temperature change was firstly proposed, which combined with the Chaboche viscoplastic constitutive model to approximately compute the notch local stress and strain under multiaxial thermo-mechanical loading. Based on the proposed method, a life prediction method that can take into account fatigue, oxidation, and creep damage was developed, which can quickly predict notch fatigue failure lifetime under variable amplitude multiaxial thermo-mechanical loading. The proposed method was verified by the coupled thermal-structural nonlinear FEA and the experimental life results for the tenon joint structure specimens under eight thermo-mechanical loading paths. The comparison of computed and analyzed stress-strain history showed that a good agreement can be obtained. Comparing with experimental life data, all predicted lives fall in a 2-factor scatter band.

The importance of the mortice and tenon joint on the zygomatic arch in reduction malarplasty-a retrospective study

The aim of this study was to compare two kinds of reduction malarplasty in terms of their bony consolidation. Patients that underwent reduction malarplasty were reviewed retrospectively. The medial movement of the zygomatic body and the zygomatic arch as well as the complications and satisfaction of patients were investigated. The surgical procedure entailed a classical or modified L-shaped osteotomy through intraoral and sideburn approaches. Two groups were distinguished, those for whom a mortice and tenon joint was formed on the zygomatic arch (Group I), and those that formed end-to-end bone contact (Group II). All the cases in Group I showed an improved facial contour with sufficient bone contact. A larger medial movement of the zygomatic arch was observed in Group I (4.54 ± 0.41 mm) than in Group II (2.72 ± 0.29 mm) (P = 0.016). More bone malunion was observed in six cases of Group II (P = 0.030) and four required a second operation. In conclusion, this study indicates that the mortice and tenon approach is preferable when the priority is bony consolidation.

Research on seismic performance of traditional Chinese hall-style timber buildings in the Song and Yuan dynasties (960\u20131368 AD): a case study of the main hall of Baoguo Temple

The hall-style timber frame built in the Song and Yuan dynasties (960–1368 AD) is one of the most important structural prototypes of the traditional timber architecture in East Asia. The current research, through a typical case of the main hall of Baoguo Temple in Ningbo, China, aims to present an accurate and effective seismic performance evaluation method applicable to hall-style timber structures without time–cost expenditure. To obtain more realistic seismic response of hall-style timber frame, a simplified numerical model of the main hall of Baoguo Temple is established based on in situ measurements and low-cycle reversed loading tests results of mortise–tenon joints, moreover, nonlinear static pushover analysis has been performed to quantify the seismic performance levels under five loading conditions. The generalized force–deformation relationship of the timber plastic hinges is modified regarding to the moment–rotation curves of four special mortise–tenon joints. The seismic behaviour of global hall-style timber frame is evaluated through capacity spectrum method and verified by time history analysis, local failure mechanisms are evaluated by the occurrence sequence of plastic hinges. Finally, a performance-based assessment method adequate for the traditional hall-style timber architectures has been proposed with comparison to the current codes. The results have shown that the structural stiffness of the width-direction is less than that of the depth direction due to the asymmetrical configuration of the timber frame, and the building can maintain a stable state under large lateral displacement before collapsing. The inter-storey drift angles of the building under peak ground accelerations of 0.1 g, 0.2 g, and 0.3 g are less than the suggested ultimate values in the current local codes, however, the main hall represents to be more vulnerable to damage when suffer seismic action along the width-direction. This research can provide a reference for seismic performance evaluation and preventive conservation of ancient hall-style timber architectural heritage.

Finite element comparative analysis on the influence of new commercial development on subway station structure

The newly added commercial projects can effectively connect the subway station with the original commercial ones, and their constructions and breaking holes for the station exterior wall have an impact on the adjacent station structure. The risk analysis of the renovation construction is necessary for the insurance of the station safe operation. Combined with the renovation commercial project, Finite Element methods are adopted to simulate the construction process and the influences on the adjacent station structure are evaluated. The maximum lateral displacement of the station exterior wall for two three-dimensional models are 3.7 mm and 3.8 mm, respectively. The maximum lateral displacement and maximum vertical displacement of the station structure by two-dimensional model are 4.1 mm and 5.2 mm, respectively, and the bending moment and shear force of the station exterior wall increase by 4%. Considering the restriction effect of the transverse wall in two three-dimensional models, the maximum bending moment of the station exterior wall has a small difference and is smaller than that of two-dimensional model, and the opening width of the outer wall of the station is 0.2 mm. The force between piles for two three-dimensional models is close and the construction has little influence on the tenon joint.

Effect of the Reinforced Plastic Clamp Fitting on the Bending Strength of the Spruce T-Type Loose Tenon Joints

This article presents the bending strength and flexural properties of the glued T-type spruce loose tenon construction joints with and without reinforced plastic clamp fitting. Construction joints are designed according to Eurocode 5. The samples are made from European spruce (Picea abies Karst.) C24 class construction material with relative wood moisture 18% and relative wood density 410 kg/m3. Samples are assembled with water/high temperature resistant polyurethane adhesive and polyvinyl acetate dispersion adhesive. The total number of samples is 48. The sample width is 95mm and thickness is 45mm. Samples were subjected to moisture, weight controls and 48h stored in the climate chamber before practical bending load test. T-type loose tenon joint construction samples with reinforced plastic clamp fittings glued with polyurethane adhesive under bending load are 2.6% stronger and 13.8% less flexural then without reinforced plastic clamp fittings. T-type loose tenon joint construction samples with reinforced plastic clamp fittings glued with polyvinyl acetate dispersion adhesive under bending load are 9.7% weaker and 20% less flexural then without reinforced plastic clamp fittings. The accuracy of the developed bending strength, deformability and elasticity modulus of the examined construction joints was verified positively by experimental studies.

Study of the mechanical behaviour and damage characteristics of three new types of joints for fabricated rectangular tunnels using a numerical approach

Joints are the weakest parts of prefabricated tunnels, and it is important to consider the material nonlinearities, mechanical properties and complex behaviours of joints in structural design. Based on existing joints, this paper proposes the design of three new types of joints for fabricated rectangular tunnels, including self-weight mortise and tenon joints, bolt mortise and tenon joints and steel plate mortise and tenon joints. To explore the mechanical behaviour and damage characteristics of these new joints, three-dimensional finite element numerical models are established with a plastic damage model to reflect the nonlinear mechanical characteristics of each component of the joint. The results of the numerical analysis are compared with experimental data, verifying the validity of the process. Then, the compressive and bending capacity, steel reinforcement bar stress and concrete damage characteristics of rectangular tunnel joints under different combinations of axial loads and displacement loads are defined. It is indicated that the mortise and tenon joint type significantly affects the damage evolution process of the concrete at these joints. Among the three joint types, the bolt mortise and tenon joint has the largest damage area of concrete and, consequently, the most damage elements due to its reasonable joint structure. Hence, from the perspective of the mechanical performance of the structure, the bolt mortise and tenon joint provides the largest flexural bearing capacity and structural safety, followed by the steel plate mortise and tenon joint. The self-weight mortise and tenon joint has the smallest flexural bearing capacity, but it is the simplest joint proposed and is easier to construct than the other two joints.

Innovative design of modern mortise and tenon structure under the concept of green reduction

In the furniture industry, some traditional Chinese mortise and tenon joints are not suitable for the current requirements for carbon reduction and environmental protection of furniture products. This article aims to explore new ideas and new methods of modern mortise and tenon structure design. The reduction principle in the green design concept is introduced for the furniture modern mortise and tenon structure design. Based on modern furniture, a systematic analysis of the modern mortise and tenon structure design is carried out. Additionally, this review discusses the method of applying the reduction principle in modern tenon and tenon structure design in the context of green design. The development status and trend of modern mortise and tenon structure design is summarized and an innovative design practice of modern mortise and tenon structure is carried out. The combination of green design and furniture design has important practical significance in a modern context.

Innovative design of modern mortise and tenon structure under the concept of green reduction

In the furniture industry, some traditional Chinese mortise and tenon joints are not suitable for the current requirements for carbon reduction and environmental protection of furniture products. This article aims to explore new ideas and new methods of modern mortise and tenon structure design. The reduction principle in the green design concept is introduced for the furniture modern mortise and tenon structure design. Based on modern furniture, a systematic analysis of the modern mortise and tenon structure design is carried out. Additionally, this review discusses the method of applying the reduction principle in modern tenon and tenon structure design in the context of green design. The development status and trend of modern mortise and tenon structure design is summarized and an innovative design practice of modern mortise and tenon structure is carried out. The combination of green design and furniture design has important practical significance in a modern context.

Mechanical performance of pre-fabricated metal dovetail connections for Cross-Laminated Timber (CLT) structures

The performance of Cross-Laminated Timber (CLT) structures is usually dominated by their connections. In this paper, a prefabricated connection, named metal dovetail connection, was proposed for CLT structures. Such connections were inspired by traditional mortise and tenon joints, and can provide quick assembly for orthogonally adjacent CLT wall panels. Monotonic and cyclic loading tests were performed to investigate the withdrawal, push-down, and shear behavior of the proposed metal dovetail connection. The failure modes of the connection are reported, and the load resisting parameters (i.e., stiffness, load resisting capacity, ductility) were derived and compared. The connection strength was further predicted through analytical approaches, and the overstrength factors were evaluated. The overstrength factors of the connection were respectively 1.86 and 1.54 under push-down and shear loading scenarios.

MOCCA

We present a computational framework for modeling and optimizing complex assemblies using cone joints. Cone joints are integral joints that generalize traditional single-direction joints such as mortise and tenon joints to support a general cone of directions for assembly. This additional motion flexibility not just reduces the risk of deadlocking for complex joint arrangements, but also simplifies the assembly process, in particular for automatic assembly by robots. On the other hand, compared to planar contacts, cone joints restrict relative part movement for improved structural stability. Cone joints can be realized in the form of curved contacts between associated parts, which have demonstrated good mechanical properties such as reduced stress concentration. To find the best trade-off between assemblability and stability, we propose an optimization approach that first determines the optimal motion cone for each part contact and subsequently derives a geometric realization of each joint to match this motion cone. We demonstrate that our approach can optimize cone joints for assemblies with a variety of geometric forms, and highlight several application examples.

Multiresin Additive Manufacturing Process for Printing a Complete Denture and an Analysis of Accuracy.

A complete denture, consisting of teeth and a gum base, is a standard device used to restore masticatory and esthetic functions in patients with complete edentulism. The different colors and mechanical properties for teeth and the gum base mean a complete denture is manufactured using two materials with different mechanical properties. This study proposes a method to make a complete denture using a laboratory-developed, multiresin additive manufacturing (MRAM) system with two resins and different mechanical properties. A tenon joint is used to create the bottom of the teeth that fit into the gum base, ensuring automatic alignment and higher bending strength. The mechanical properties, material waste, fabrication time, and effect of the tenon joint on the bending strength of a complete denture printed using the MRAM system are compared with the values for a computer-aided design and computer-aided manufacturing (CAD/CAM) system. Experimental results show that the printed denture is manufactured 3 times faster and produces 14 times less material waste, but is 35.08% less inaccurate than one produced using a CAD/CAM system. The proposed tenon joint increases the bending strength by 31.94%. The MRAM system is applicable for printing a complete denture.

Verification of the shear performance of mortise and tenon joints with top and bottom notches at the beam end

Shear experiments on mortise and tenon joints with top and bottom notches in the beam end were conducted with the length of the tenon as a variable. In addition, material experiments were performed to investigate the structural performance of the fracture modes of the joint. The experimental results show that when the lower notch at the beam end experiences splitting, the shear forces were identical for different tenon lengths and did not decrease. In addition, the deformation performance of the joint up to yielding was largely due to the compressive deformation perpendicular to the grain of the wood on the sides of the tenon. Based on the theory of the calculation method of the splitting strength of a notched beam, a formula for the splitting strength when the end of the beam is moment-resisting was proposed. It was confirmed that the proposed formula could estimate the shear force that caused the splitting fracture of the lower notch. In addition, the increase in shear force after the lower notch experienced splitting fracture was due to the increase in clamping force of the beam end due to rotational deformation.

RESEARCH ON ASEISMIC BEHAVIOR OF STRAIGHT TENON JOINTS REINFORCED BY SMA STRINGS IN ANCIENT TIMBER BUILDINGS

The semi-rigid mortise-tenon joints in the wooden structures of ancient buildings are often destroyed before beams and columns under major earthquakes, which are the important positions for reinforcement and protection. A new type of shape memory alloy (SMA) preventive reinforcement device is designed, and low-cyclic loading tests are carried out on five reinforced joints and one unreinforced joint. The failure modes, moment-rotation relationship, strength degradation, stiffness degradation, energy dissipation, self–centering ability and deformation capacity of the joints reinforced by SMA strings with different numbers and different pretension strains are studied. A calculation method for bending capacity of straight tenon joints reinforced by SMA strings is established. The results show that the bending capacity of the joints after SMA reinforcement is improved. The maximum bending capacity of the reinforced joint is 1.49 times that of the unreinforced joint. Compared with the unreinforced joint, the strength degradation of the reinforced joints is not serious, which indicates that the SMA strings can still continue to provide the bending capacity for the joints when the rotation is large. The maximum rotational stiffness of the reinforced joint is 2.24 times that of the unreinforced joint. With the increase of the rotation of joints, the energy dissipation of unreinforced joint gradually decreases, however the energy dissipation of reinforced joints increases first and then decreases. At the same rotation, the relative residual deformation decreases with the increase of numbers and of pretension strains of SMA strings, and the self-centering ability is enhanced. The results of research can provide a reference for the preventive conservation of the mortise-tenon joints in ancient timber structures.

NUMERICAL STUDY ON EFFECTS OF TENON SIZES ON WITHDRAWAL LOAD CAPACITY OF MORTISE AND TENON JOINT

The effect of tenon length and tenon width on withdrawal load capacity of mortise and tenon (M-T) joint was studied based on the finite element method (FEM), and the relationship of withdrawal load capacity relating to tenon length and tenon width was regressed using response surface method. The results showed that the tenon length and tenon width had remarkable effects on withdrawal load capacity of M-T joint T-shaped sample. The effect of tenon length on withdrawal load capacity was greater than tenon width. The regression equation used to predict the withdrawal load capacity was capable of optimizing the tenon sizes of M-T joint with R-square of 0.926. Using FEM can get more knowledge of M-T joint visually, and reduce the costs of materials and time of experiments.

Evaluating Design of Mortise and Tenon Furniture Joints Under Bending Loads by Lower Tolerance

This study aimed to estimate the design value for mortise and tenon joints. In this respect, the design value for static load tests was determined using lower tolerance limit methods. A lower tolerance limit value at 0.99/0.99 confidence/proportional level was chosen as a design value (199.05 N.m) to secure higher joint reliability in a furniture frame. A side frame of a simple wooden chair was theoretically analyzed to obtain internal forces acting on joints, whereas the load of 1000 N was applied in the vertical direction on the top of the front leg. A full-frame chair with mortise and tenon joints would not be overstressed when a chair is under static load while not exceeding 2000 N. By applying this method, all chairs should survive static load up to 2000 N. While performing cyclic front-to-back load test, all tested chairs met the American Library Association requirements for light-duty service load, specified for household chairs. This study demonstrates that a joint failure could be prevented under expected loads specified by the standard if the joint design value is known.

Experimental study on the reinforcement methods and lateral resistance of mortise-tenon jointed traditional timber frames

In order to study the lateral resistance of reinforced traditional Chinese timber frames with mortise-tenon connections, three cyclic tests were conducted on one-bay mortise-tenon jointed traditional timber frames. Three reinforcement methods, i.e., steel angle strengthening, wood brace, and Timu, were studied. Seismic performances were evaluated according to the experimental phenomena and the test results. The failure mode, hysteresis curves, skeleton curves, curves of stiffness degradation, and energy dissipation capacity of the three specimens were analyzed based on the tests. The test results showed that the wood frames had good deformability. The stiffness degradation of the timber frame was severe at the initial loading stage; however, the degradation rate tended to decrease after the initial stage. In addition, the energy dissipation increased as the lateral displacement increased. The wooden frames with mortise tenon joints strengthened by steel angle, wood brace, and Timu can achieve good aseismic results. The study can provide a theoretical basis for seismic design and reinforcing methods of traditional timber structures.

Normal contact performance of mortise and tenon joint: theoretical analysis and numerical simulation

This article aims to investigate the contact characteristics of mortise and tenon (M&T) joints in the traditional timber structures. In particular, the normal embedded compressive contact between contact surfaces of M&T joint was investigated. Based on basic contact theory and contact characteristics between mortise and tenon, a normal elasto-plastic contact model, which can reflect the real normal contact behavior of M&T joints in traditional wooden structures, was proposed. Coulomb friction contact was utilized to describe the tangential slipping characteristics of the contact surfaces. Micro-morphology scanning tests of wood samples with different roughness were carried out to determine the parameters involved in the normal contact model. The normal contact model subroutine of M&T joint was compiled by FORTRAN language, implemented into ABAQUS through user-defined interface (UINTER). Then the proposed model was verified by shear tests of wood contact surfaces considering different normal pressures. Finally, a finite element model (FEM) of straight tenon joint subjected to cyclic reversed loading, based on the proposed normal elasto-plastic contact model, was developed, and a FEM considering normal “hard contact” between the contact surfaces, was also performed. The simulation results were validated by the experimental results. Results showed that the user-defined normal elasto-plastic contact FEM was more in line with the actual force state and mechanical behavior of M&T joints, which can more accurately predict the failure modes and simulate the hysteretic behavior of M&T joints, compared to the FEM considering normal “hard contact” of the contact surfaces.

Seismic Performance Evaluation of a Roof Structure of a Historic Chinese Timber Frame Building

ABSTRACT This paper presents a finite element modeling method for a prediction of lateral resistance and seismic response of the roof structure of a historic Chinese timber frame building. Force-displacement relationships of straight tenon joints, Mantou tenon joints, and Dougong bracket sets are calibrated by experimental results. In-plane and out-of-plane resistance analyses have been carried out, and force-displacement relationships and stress contributions are obtained. Acceleration and displacement responses are attained and adopted for the seismic performance evaluation of the historic roof structure. Results show that the overall in-plane and out-of-plane hysteresis performances of the roof are poor and energy dissipation abilities are weak. The seismic responses of measuring nodes are close under the same seismic excitation. As the seismic excitation increases, peak responses of all measuring nodes increase. Dougong brackets and mortise-tenon connections dissipate large seismic energy under strong excitation, and seismic responses (acceleration and displacement responses) of the roof structure are significantly reduced. The maximum drift angles of the entire roof truss are found to approach 1/2500 rad, demonstrating that the roof structure has good integrity.