Recent progress in research on the cutting processes of wood. A review COST Action E35 2004–2008: Wood machining – micromechanics and fracture

Abstract

Recent progress in research on the cutting processes of wood is presented, particularly in regard to new methods of accomplishing an increase in volume recovery by sawmills. The suitability of modern fracture mechanics was demonstrated for the estimation of the cutting power for saws in which kerfs are different from saws used in cutting tests, and whereby the data of sawn material – such as the specific work of surface formation (toughness) and the shear yield stress – were determined. Cutting tests were carried out on the modern frame sawing machine (sash gang saw) for narrow-kerf sawing with the hybrid dynamically balanced driving system and elliptical teeth trajectory movement.

Effect of the Drying Method of Pine and Beech Wood on Fracture Toughness and Shear Yield Stress

“…The average cutting power P c was calculated as the difference of the mean total power P T and the average idle power P i [ 41 , 46 ], as expressed in Equation (3): …”

“…on the energetic effects corresponding directly to the cutting process. The average cutting power in a working stroke P cw was calculated as in Equation (4), following the works [ 41 , 46 ]: …”

“…It is important to notice that the value of chip acceleration power P ac is calculated globally for the sawing process and is not directly related to the number of working teeth. As the contribution of P ac on the overall cutting power P cT is negligible [ 41 , 46 ], it is not considered in analyses performed for the needs of this research.…”

“…However, assuring an appropriate sharpness of the tool, component ❹ can be ignored, especially at the initial phase of the tool use. Summarizing, the following assumptions were made for the needs of this research: only freshly sharpened blades were used in cutting tests: component ❹ of Equation (5) = 0; chip acceleration power P ac is omitted: component ❸ of Equation (5) = 0; values of the shear angle Φ c were calculated following the approach of Merchant [ 46 ], considering specific cutting zone geometry as well as coefficient of friction. This procedure is valid when deviations in the shear angle assigned to inherent material properties can be neglected for larger values of uncut chip thicknesses, as used in this experiment; the value of friction coefficient µ = 0.6 was adopted following the work of Glass and Zielinka [ 49 ]; the effect of lateral forces on the power consumption can be omitted when cutting in straight direction and with minimal saw deviation [ 50 ].…”

“…values of the shear angle Φ c were calculated following the approach of Merchant [ 46 ], considering specific cutting zone geometry as well as coefficient of friction. This procedure is valid when deviations in the shear angle assigned to inherent material properties can be neglected for larger values of uncut chip thicknesses, as used in this experiment;…”