Stress and Strain Analysis of Plywood Seat Shell/Analiza naprezanja i deformacije furnirskog otpreska sjedala

In this paper, the stress and strain analysis of common laminated wood seat shell is performed. Experimental stiffness evaluation is conducted by measuring displacement of the point on the backrest, and experimental stress analysis is carried out by tensometric measuring at the critical transition area from the seat to the backrest. Finite element analysis is carried out layer by layer with a "2D linear elastic model" for orthotropic materials. Good matching is found between numerical and experimental results of displacement. It is also shown that the results of the principal stress in the measurement points of the seat shell compare favourably with experimental data. The applied in-plane stress analysis of each individual veneer is not applicable for interlaminar stress calculations that are a significant factor in curved forms of laminated wood. Curved forms of laminated wood products require more complex numerical analysis, but the method can be used to achieve approximate data in early phase of product design. Keywords: laminated wood, seat shell, tensometric measuring, strain gauges, stress, strain, FEM U radu je provedena analiza naprezanja i deformacija uobicajenog otpreska sjedala. Eksperimentalna procjena krutosti napravljena je mjerenjem pomaka tocke na naslonu sjedala, a eksperimentalna analiza naprezanja obavljena je tenzometrijskim mjerenjem na kriticnom prijelazu izmedu sjedala i naslona. Analiza metodom konacnih elemenata provedena je sloj po sloj 2D linearnim elasticnim modelom za ortotropne materijale. Dobivena je dobra podudarnost racunskih i eksperimentalnih rezultata pomaka. Takoder je potvrdeno da su rezultati glavnog naprezanja u mjernim tockama furnirskog otpreska sjedala usporedivi s eksperimentalnim podatcima. Odabrana analiza naprezanja u ravnini svakoga pojedinacnog furnira nije primjenjiva za izracun interlaminarnih naprezanja, koja su vazan cimbenik zakrivljenog oblika uslojenog drva. Naime, takvi oblici uslojenog drva zahtijevaju slozeniju racunsku analizu, no metoda se moze primijeniti za postizanje pribliznih podataka u ranoj fazi projektiranja proizvoda. Kljucne rijeci: uslojeno drvo, otpresak sjedala, tenzometrija, davac pomaka, naprezanje, deformacija, FEM