Test And Vibration Characteristic Study On The Cutting Performance Of The Special Salix-psammophila Chipper

There are abundant sandy shrub resources in the western area of Inner Mongolia,especially the Salix-psammophila.Using the Salix-psammophila to produce man-made board has become an important way for increasing the local farmers' income.Till now,the domestic drum chipper is widly used to cutting the sandy shrub.However,there are some problems for the drum chipper such as the low pressure of the feeding mechanism,the difficulty of cutting off the salix top,the low production efficiency and the serious power mismatch in the process of cutting the salix psammophila.Therefore,the BX215S-type Salix-psammohila test chipper with the floating roller feeding mechanism was designed and manufactured by the research group.This mechanism matched with the domestic drum chipper to cutting the salix,which increased the production efficiency and chip quality to a great extent.Aiming at the existing problems such as big power consumption,intensive vibration and big impact of the modified Salix-Psammophila chipper,it is very urgent to carry out the cutting performance and vibration measurement for its main working parts.This achievement will play a significant role in further investigating the cutting force and vibration effects on the chipping qualities and using the Salix Psammophila chipper efficiently and reasonably in the future.Therefore,the cutting performance measurement has been carried out.The response surface methodology in Design Expert was also adopted to investigate how the cutting parameters influence the cutting force and chip quality.The multi-point vibration measurement systems for its main working parts such as the cutting mechanism and feeding mechanism under the unloaded and working conditions have been constructed.At the same time,the static structural analysis and pre-stress modal analysis have been realized in ANSYS Workbench.The main research conclusions were illustrated in details as follows.1?The Design Expert was used to design the orthogonal experiment.According to the determined factors,the regression equations of the main cutting force,the normal cutting force,the axial cutting force and the rate of the qualified chips have been constructed.Their reliablility has been verified by using the variance analysis.Meanwhile,the response surface methodology was used to analyze how each cutting parameter as well as their interaction influences each cutting force and the rate of the qualified chip.As far as the main cutting force is concerned,the highly significant factor is the moisture content.The primary and secondary sequence of each factor is the moisture content,the interaction between the salix diameter and moisture content,feeding content,the salix diameter and the interaction between the feeding content and moisture content.The other factors are all insignificant.As far as the normal cutting force is concerned,the primary and secondary sequence of each factor is the feeding content,the interaction between the feeding content and the moisture content,the interaction between the salix diameter and the moisture content,the moisture content,the interaction between the feeding content and the salix diameter.As far as the axial cutting force is concerned,the primary and secondary sequence of each factor is the rotational speed of the knife roller,the salix diameter,the interacton between the rotational speed of the feedng roller and the moisture content.As far as the rate of the qualified chip is concerned,the the primary and secondary sequence of each factor is the rotational speed of the knife roller,the rotational speed of the feeding roller,the interaction between the rotational speed of the knife roller and the rotational speed of the feeding roller,the moisture content.2?As is shown from the cutting force measurement,the axial cutting force does exist and it is approaching to the normal cutting force.One of the reasons generating the axial cutting force is the friction force caused by the ralative motion of the salix in the extrusion of the fixed knife.The other is the unbanlanced vibration of the knife roller.3?As is shown from the vibration measurement analysis in the time domain and frequency domain,the vibration accelerations of the cutting mechanism and feeding mechanism under the working condition are obviously higher than those under the unloaded condition and more affected by the rotational speed of the knife roller and feeding roller,feeding quantity,moisture content and the root diameter of the Salix Psammophila.The suggested rotational speed of the knife roller is 900r/min in the actual production.Especially,when the rotation speed of the feeding roller comes up to 80r/min,the main working parts such as the cutting mechanism and feeding mechanism vibrated dramatically.4?The three dimentional body of the cutting mechanism is built in Soild Works and imported to ANSYS Workbench.Its static structural analysis and prestress modal analysis at the maximum designed rotational speed of 1320r/min and designed cutting force of 21.6k N as well as the maximum working rotational speed of 1000r/min and working cutting force of 15.8k N are carried out respectively.As is shown from the static structural analysis,the stress and strain concentration zones of the whole cutting mechanism locate in the adjacent area between the knife roller and the axis as well as the cutting edge of the knife under both conditions.As is shown from the first eight-order prestress modal analysis,the maximum deformation concentrated on the knife edge and the outer surface of the knife roller when the cutting mechanism is working at its first-order natural frequency.With the natural frequency increasing,the internal strain is also increasing?When the natural frequency comes up to its third or fourth order natural frequency,the cutting mechanism begins to swing up and down or left and right along with the radial direction.When the natural frequency comes up to eighth or ninth order natural frequency,the torsional deformation of the cutting mechanism appears.The modal deformations under both working conditions are similar.The stress and strain at the maximum working rotational speed and cutting force are obviously lower than those at the maximum designed rotational speed and cutting force.This shows that the cutting mechanism runs stably under the normal working condition.