In this paper, the stress and strain analysis of the frontal parallel joints with two different 3D printed connectors is performed. The connectors were made of PLA material and were bonded to wooden parts (spruce) with a one component polyurethane adhesive. The test was carried out to determine mechanical properties of the joints at the point of failure and proportional limit. Analytical calculations were used to determine: the effective modulus of elasticity of the joints, the normal stress of joint parts and the deflections at two directions. Numerical stress and strain analyses were performed with finite method software. The results show that the ratio between the effective modulus of elasticity of joint and the modulus of elasticity of spruce wood is 0,71 for connector without inner wall and 0,61 for connector with inner wall. The ratio between the appropriate values of the stress and deflection at the point of failure for connector with and without inner wall is approximately 0,80 and also between the appropriate values of the stress and deflection at the point of proportional limit is 0,90. The results also indicate that the analytical and numerical calculations gave reasonable estimates of mechanical behaviour of the joints.

UDK: 630*81:674.031.632.2(497.6 Kladanj)            582.632.2:674.038.17(497.6 Kladanj) There are many factors that affect appearance and spreading of the red heart in beech stands. Therefore, this research presents an analysis of site quality class and taxation elements (diameter at the breast height, height of the tree and age of the tree) influence on the participation and distribution of the red heart in the forest compartments 107. M.U. „Gosteljaˮ - (II- quality class) and 47. M.U. „Srednja Drinjačaˮ - (III- quality class). The appearance of the red heart on the beech trees considering on the site quality class was researched, as well as the red heart appearance frequency in dependence on the tree diameter at the breast height and age of the tree, size and distribution of the red heart in the longitudinal and transverse direction. The results of research showed that the number of trees with the red heart and the length of the technical roundwood with the red heart increase with increase of diameter at the breast height (age of the tree). As well, it was established that the appearance frequency of the trees with red heart considering the diameter at the breast height (the age of the tree) was larger on the stands belonging low quality site classes. The site quality class affects the distribution of the red heart at the thicker beech trees in the longitudinal direction, while at the thinner and trees of medium diameter, the influence of site quality class on the distribution of the red heart is not expressed in great extent. Larger diameters of the red heart in average have beech trees on the low quality site classes.

Abstract This paper presents a stiffness analysis of a statically indeterminate wood-chair side-frame. Numerical calculations are carried out with a ‘linear elastic model’ for orthotropic materials. The mathematical model is solved by a ‘finite element method’. The matrix analysis of structure is carried out by a ‘direct stiffness method’. The frame joints are assumed to be ideally rigid and also as semi-rigid. Horizontal displacement of the top point of the back post is calculated for the most frequently used type of loading for the structure. The results of the calculation indicate that chair side frame becomes stiffer as the position of the stretcher is lowered and/or the stretcher cross section is increased. The results revealed that stiffness of joints in a frame had a considerable impact on the structure deflection. A satisfactory agreement was found between the numerical results and the results obtained by direct stiffness method.

Abstract This paper presents numerical analysis of the effects of tenon length on flexibility of mortise and tenon joints. Numerical calculations are carried out with a linear elastic model for orthotropic material. The mathematical model is solved by a finite element method. The results of the calculation indicate that a mortise and tenon joint becomes stiffer as tenon length increases. A satisfactory agreement was found between the experimental data taken from literature and the obtained results, thus confirming the conclusions made. Rotation stiffness was determined and also used in the structural analysis of a simple furniture frame. The results revealed that stiffness of joints in a frame had a considerable impact on the structure deflection.

The FV method was originally developed for fluid flow, heat and mass transfer calculations (Patankar, 1980), and later generalized for stress analysis in isotropic linear and non-linear bodies (Demirdžic & Muzaferija, 1994; Demirdžic et al., 1997; Demirdžic & Martinovic, 1993). For the purpose of the stress analysis in the wood, the method is modified to take into account the anisotropic nature of the wood and influence of the moisture content and the temperature on the deformation and stresses (Horman, 1999). Also, performance of the wood is found to be very sensitive to the moisture content and the temperature. Thus, it is of a great importance to be able to predict behavior of such materials under different hygrothermo-mechanical loads. In order to demonstrate the methods capabilities, a transient analysis of fields of temperature, moisture, and stresses and displacement in the wood subjected to hygro-thermal or mechanical loads is performed.

This paper presents numerical analysis of stress and strain conditions of a three-dimensional furniture skeleton construction and its joints. The fi nite volume method is used in the calculation. Orthotropy of the wood material is accounted for by approximating it with an isotropic material whose elastic modulus and Poisson’s ratio are calculated by employing the least-square method. The displacement of the edge point for the loaded joint was also determined experimentally. The agreement of results of the calculation and experimental data can be considered satisfactory. The numerical results presented in this paper also provided an opportunity for identifi cation of the region with the largest load and strain in the complex chair skeleton construction, which is one of the most complex pieces of furniture.

This paper presents a numerical method (the finite volume method) for analysing stress and strain in wood as a solid body. The method is very simple and easy to use. It starts from an integral form of the equations governing momentum, heat and mass balance. Second-order in both time and space finite volume discretisation is performed using the corresponding constitutive relations, resulting in a set of algebraic equations, which are then solved by an efficient segregated iterative procedure. In order to demonstrate the method’s possibilities, stress and deformation are analysed in a loaded chair and in wood samples during the process of wood drying and steaming.