有限要素法

To study the rupture mechanics and condition of woods and wooden sheet materials, stress distributions in these materials must be examined. However, for the complicated shape of specimens and load condition, it is practically difficult to bring light on detailed stress distributions in various specimens experimentally. Though the Moiré method and the photo-elastic method for these stress analysis are used experimentally, clear fringes to be able to analyze are difficult to be obtained. In order to solve such problems, the mathematical and physical approximate methods must be used. Recently, the electronic computers make these numerical methods possible. The former reminds us of the finite difference method and the latter, of the finite element method. The author attempted to solve these problems approximately by means of the finite element method. The computer programs were designed to be able to vary the subdivision sizes by merely changing the data cards and a few parts of a main program, so that the influence of the subdivision sizes on the accuracy of the approximation could be discussed easily (an example of the flow chart and of the program in FORTRAN is shown in Fig. 4 and Appendix, respectively). Hereby, the influence of the variation of the subdivision sizes on the convergence into the exact solution was clarified (Figs. 9 and 10). It was ascertained that the satisfactory solutions are obtained, using this numerical analysis. Moreover, an example of the experimental results was compared with the results computed with the elastic constants of hardboard (Fig. 11). In this result, the satisfactory agreements were recognized. In this paper, the applications of the finite element method to the partial compression problems, as shown in Figs. 1 and 2, of isotropic plates in the elastic area were attempted, and a few examples of the numerical computation were given (Figs. 5～8). If assuming woods and plywoods as the rectangular orthotropic materials approximately, it will be suspected that the numerical analysis for these orthotropic materials and the elastic-plastic analysis can be solved approximately by the above method.