Proportional limit of wood obtained from a load-time diagram during an impact bending test

We transferred the linear part of a load-deflection diagram from an impact bending test of wood into a load-time diagram. In addition, we proposed a method to obtain the proportional limit from the load-time diagram. Japanese cedar (Cryptomeria japonica D. Don), hondo spruce (Picea yezoensis Carr. var.hondoensis Rehd.), hiba arbor-vitae (Thujopsis dolabrata Sieb. et Zucc.), Japanese red pine (Pinus densiflora Sieb. et Zucc.), paulownia (Paulownia tomentosa Steud.), Manchurian ash (Fraxinus mandshurica Rupr.), and Japanese evergreen oak (Quercus acuta Thunb.) were used in this study. The dimensions of each specimen were 115mm (L) * 7mm (R) * 7mm (T). The results were as follows: (1) The linear region of the load-deflection diagram in the impact bending test could be transferred with sufficient accuracy to a load-time diagram using a sine function. (2) Approximating the load-time diagram by a linear equation was useful for obtaining the proportional limit.