Finite element simulations of the loading and deformation of plywood seat shells
Modern 3D modelling software reduces the need for a large number of prototypes, means fewer product-development cycles and lower costs (time/cost), as well as improving the quality of furniture designs. However, the mechanical testing of final products is still required in order to confirm the simulation results. In this study the theoretical behaviors of different plywood seating shells (using the SolidWorks® FEM simulation software) were compared with the real results obtained using tests to measure the deformation of the backrest. The deviations of the actual deformation from the simulation were significant for the different shells and increased with loading above the elastic deformation limit of the material. It was concluded that the SolidWorks® simulation software could be effectively used in the calculation of the component displacements, strains, and stresses of seat designs subject to internal and external loads.
Finite element modelling versus reality for birch chairs
When chairs and other furniture are designed the work is mostly founded on handicraft experience. Calculations based on solid mechanics theory are almost never used in order to find out optimal solutions for different wood members, or the structure as a whole. We have therefore studied a simple chair, made of birch, where the emphasis is laid on its ability to carry different loads. Using the method of finite elements we have predicted the strain and stress at different points on the chair structure. Further, we have manufactured the chair and exposed it to the same load pattern as used in the finite element calculations. The strain has been monitored and compared to the calculated value at the points of most interest. The result shows that part of the calculations corresponded fairly well with the monitored values but also that much work still remains in order to totally predict the accurate structural behaviour for such a simple frame as a chair. Probably, some of the discrepancies depend on the wood material which exhibits so different response for stress in different directions.ZusammenfassungStühle und andere Möbel werden meist aufgrund von Erfahrungswerten konstruiert. Berechnungen aufgrund einer mechanischen Theorie werden nur selten benutzt, um optimale Lösungen für die Konstruktion zu finden. Wir haben daher einen einfachen Stuhl aus Birkenholz untersucht, der für unterschiedliche Lasten konstruiert war. Zunächst haben wir mit Hilfe der FE-Methode die Kraft- und Spannungsverteilung an verschiedenen Strukturelementen vorausberechnet; dann haben wir einen entsprechenden Stuhl hergestellt, mit den gleichen Lasten wie in der Berechnung belastet und die Spannungswerte gemessen. Ein Teil der gemessenen Werte stimmte einigermaßen mit den simulierten überein. Doch es zeigte sich, daß noch einige Forschungsarbeit nötig ist, um das Verhalten einer so einfachen Strutur wie eines Stuhles genau zu verstehen. Einige Widersprüche sind wohl auch durch die Holzstruktur bedingt, die in unterschiedlicher Weise auf Belastung in verschiedenen Richtungen reagiert.
Strength properties of L-profiled furniture joints constructed with laminated wooden panels
This study analyzed the effects of L-profiled corner joint design on maximum load-carrying capacity of case furniture. For massive panels material (Red Pine), two test groups were formed using Polyvinyl Acetate (PVAc), Desmodur-VTKA (Polymarine) and Purocal (polyurethane-based) adhesive types. First group test samples were prepared using L-profiled corner joint and second group test samples were prepared without using these. Both test samples were prepared using dowel joints. Maximum loadcarrying capacity values obtained after diagonal compression and tension tests on test samples were analyzed. The evaluations indicated that the load carrying capacity of the test samples prepared by using L-profiled corner joints was four times greater than that of other group.