Experimental Determination of Delimbing Forces and Deformations in Hardwood Harvesting

Abstract

Delimbing is the process used to cut the branches off the trunk during tree processing by forest harvester. This process can be described as chipless cutting of green wood at a feed speed of 3 to 7 ms-1.This work aims to identify the parameters influencing the efficiency of the delimbing process. To this end, the main parameters are defined, and different experimental tests are presented. The first experiment was conducted using a dynamometric pendulum that can reach cutting speeds of 10 ms-1. A Digital Image Correlation method was used in order to compute the deformation field in the branch. The deformation fields observed are consistent with previous studies in the literature. The second experimental device was a slow speed test bench. It uses a hydraulic actuator to translate the knife through the branch while measuring force and displacement. Tests were conducted, varying the diameter of branches, to analyze its effect on the cutting force. Proportionality between branch area and cutting forces were verified, and empirical coefficients were obtained for both speeds.