Conditions and origin of the critical grain size effect on the abrasive wear of woods.
To study the critical grain size effect, abrasive wear tests during wood sanding were made on 11 species of wood, 4 softwoods (Metasequoia glyptostroboides, Chamaecyparis pisifera, Cryptomeria japonica and Chamaecyparis nootkatensis) and 7 hardwoods (Ochroma lagopus [Ochroma pyramidale], Shorea sp., Cercidiphyllum japonicum, Magnolia obovata [Magnolia hypoleuca], Prunus sargentii, Betula maximowicziana and Quercus myrsinaefolia). The critical grain size effect of abrasive wear for woods appeared at small applied surface pressures during the wear, but disappeared at greater pressures. The greater the density and the yield stress of the woods, the greater were the boundary values of the applied surface pressures which showed whether or not the critical grain size effect appeared. Moreover, it was suggested that the relationship Pc = αδy + β, where α = 0.0016-0.0017, β = ±0.015, existed between the boundary value of the applied surface pressure Pc and the yield stress δy. The wear rate, obtained under the conditions of Pc, had constant values for all tested species. At the grain size d of abrasive paper greater than 100 µm, the constant value of wear rate was about 4 mm3/m.