Institute of Engineering，Beijing Forestry University
[Objectives]To avoid the damage of timber caused by the feeding rolls during forest harvesting, a new technique which the Double-V-Wings Honeycomb (DVWH) in the feeding roll was an important object to be studied in the research. The most significant exploration was to deduce the mechanism of undermining in its cell structure parameters to logging woods. [Methods]Primarily, the research method was based on the classical content of theoretical mechanics by constructing a theoretical model of the three parameters of the DVWH structure and the yield strength to conduct experiments. In the experiment, a quasi-static speed compression experiment was performed on the honeycomb structure in the Y direction. The experiment used nylon material as the experimental material. The elastic model quantity of nylon material is 1600MPa and the test data was collected by DIC technology at a compression speed of 1mm/min. Then the next experiment mainly adopted the method of low-speed impact simulation experiment, which was carried out under the condition of 2m/s. Studying the influence of cell structure parameters on the equivalent stress and energy absorption effect of DVWH under this condition.The optimal cell parameters were selected by orthogonal experiment. At this time, the test simulation timber round bar was hit to the feed roller at a speed of V=2m/s through the experiment and the flange of the feeding roll needs to be fixed. After the experiment, according to the pixel-based physical length measurement method for each graphic, the relative increase percentage of the contact area between the simulated log and the feeding roller with different structural parameters was obtained. Furthermore, the purpose of studying the coupling relationship between the cell structure parameters of the feeding roller and the contact area of the log was realized.[Results]In the experiment, the maximum displacement of the DVWH negative Poisson's ratio structure after being compressed by 5 mm in the Y direction was 2.908 mm and the maximum strain was 0.0134. At the same time, the performance under quasi-static compression conditions verified the theoretical formula of yield strength. Under low-speed impact conditions, the equivalent stress in the Y direction of the DVWH structure increased with the increase of the angle θ1 and the thickness t, and increased with the decrease of the angle θ2. The peak value of kinetic energy increases with the increase of the thickness t and the angle θ1, and the change of angle θ2 had no obvious effect on the peak value of kinetic energy. In addition, the total internal energy absorption decreased with the increase of its parameter angle θ2 and increased with the increase of its parameter thickness t. The rule of changes in angle θ1 was less obvious. After selecting polyurethane as the material for roller drive applications, the orthogonal test method was used to select the optimal parameters in the θ1, θ2, t interval to increase the contact area between the feeding roller and the log by 14.5%~26%. In addition, specific cell structure parameters could be selected according to the requirements of specific working conditions, and the log damage area of the honeycomb structure feed roller in forestry production could be predicted.[Conclusions]The structural parameter thickness t was an important index that affects the compaction strain of the DVWH structure with negative Poisson's ratio. By changing the materials selected for the negative Poisson's ratio structure and the size parameters of the DVWH negative Poisson's ratio structure, the contact area between the feeding roller and the wood was improved and the pressure on the log can be reduced. The results of this study are inspiring and helpful to reduce the damage of felled wood.