ANALYSIS OF THE WOOD SLICING MECHANISM ALONG THE GRAIN .2. THE TRANSITIVE CONDITION OF FRACTURE TYPE FROM ADVANCED CHECK TO BENDING RUPTURE

In wood slicing along the grain, it is important to know the transitiv e conditions of fracture types from an advanced check to the bending r upture of the veneer. For this purpose, we developed some theories, an d examined them experimentally using cantilever-shaped model specimens . We supposed an advanced check or the bending rupture would occur und er the following conditions: 1. An advanced check occurs when the stra in energy release rate, (GI), reaches its critical value, (G(IC)). 2. Bending rupture occurs when the stress at the slit tip reaches the ben ding strength. We predicted the fracture type at each slit (cantilever ) length by employing the calculated result which gave a smaller load between these two conditions. When the slit length is short, the theor etical load which is required to cause the advanced check is smaller t han that of the breaking in bending. We predicted that checks would de velop in these ranges. When the slit length is long, the theoretical l oad of breaking in bending becomes smaller than that of the checking. We predicted that bending rupture would be predominant in these ranges . It was confirmed that the above-mentioned predictions of the fractur e types agreed with the experimental results. Our theories proved to b e very useful in predicting the slit length at which the fracture type would change.