Abstract: [Objective] Reasonable micro-pit surface texture has been proved to improve the friction between birch and cemented carbide surfaces and to reduce the friction coefficient. The aims of this study are to discuss the influences of wood moisture content, the direction of wood section and fiber, and the speed of motion on the coefficient of friction, and provide reference and guidance for designing more reasonable texture forms.[Method] Ash and pine were selected as the research objects, the influences of wood moisture content, wood section and fiber direction and sliding speed on the friction coefficient of different micro-pits structures were assessed and compared.[Result] Compared with the non micro-pits texture surface, it was found that when the diameter of the pit is 60 μm and the moisture content is 67%±3%, the friction coefficient showed the largest decrease.The friction coefficient on the surface of the ash decreased from 0.151 to 0.091, and decreased extent reached 39.7%, and the friction coefficient decreased from 0.241 to 0.164, with a 32.0% drop on the surface of pine. The difference among the directions of wood fiber on the radial section has little effect on the friction coefficient. On the cross section, the smaller the pit diameter, the higher the friction coefficient was obtained. The influences of sliding speed on friction coefficient exhibited a great relationship with the wood moisture content during friction process. The coefficient of surface friction decreased with the increase of sliding speed, the friction coefficient curve with d=60 μm declined more obviously when the moisture content with green condition showed higher than that of surface with no micro-texture. The friction coefficient of the plane surface was reduced from 0.160 to 0.134, the decrease extent was 16.3%, and the friction coefficient of the surface with micro-texture (d=60 μm) reduced from 0.124 to 0.071, the decrease extent was 42.7%.[Conclusion] The wood moisture content has a great influence on the friction coefficient between micro-pit surface texture and wood, and the free water in wood can reduce the friction coefficient between cemented carbide and wood surface. The smaller the diameter of micro-pits, the greater the average change rate of contact angle, and the higher surface spreading speed were obtained,moreover,the friction was improved better.

Key words: wood, cutting, friction, the coefficient of friction, micro-texture