| Mechanical rock breaking has the advantages of continuous rock breaking,high rock breaking efficiency,safe and reliable operation,and easy to realize automatic control.It is widely used in tunnel excavation and coal mining.However,with the increase of rock hardness,the current rock breaking equipment generally has the problems of insufficient rock breaking capacity,serious cutter tooth wear and low rock breaking efficiency.Aiming at this problem,in order to improve the mechanical rock breaking capacity and reduce energy consumption,this paper makes a comparative analysis of conventional cutting and vibration cutting:Firstly,based on the analysis of the principle of cutting and rock breaking,this paper takes the milling rotor as the research object,and establishes the kinematics and dynamics model of cutting tool.Through the analysis of kinematics modeling,the speed of vibration cutting tool will fluctuate sharply compared with conventional cutting tool.The increase of vibration cutting speed depends on amplitude A and frequency f,and the maximum increment is 2?f A.Based on the macro crushing form of rock,the influence of the quality of rock breaking tool on cutting force is considered,and the mechanical model of rock cutting is established with momentum theorem.From the cutting mechanics model,it is found that the cutting force will decrease with the increase of milling rotor mass in a certain range.From the mechanical analysis of rock breaking by vibration,it is concluded that vibration cutting can make the cutting force fluctuate sharply and provide more cutting force.Secondly,the rock cutting model is established in the discrete element software PFC3D5.0,and the simulation tests of rock breaking by conventional cutting and vibration cutting are carried out respectively.The cutting force and specific energy consumption are mainly compared and analyzed.Finally,the undetermined parameters in the theoretical mechanical model are determined through the indoor cutting rock breaking test,and the theoretical model is verified.There are some errors between the calculated values and the results of the theoretical model,but the variation rules of the two are the same.The failure reason of vibration cutting test is analyzed,and the structure of vibration cutting test bench is redesigned.The results show that vibration cutting can enhance the ability of rock breaking and reduce energy consumption.Through the simulation analysis,it is found that the vibration direction is the tangent direction of the tool path,which has the best rock breaking effect,and the cutting force peak value and the necessary energy consumption are lower than other directions;In this paper,there is an optimum frequency of vibration cutting,which is about 58 Hz,Considering the rock breaking capacity and specific energy consumption,the amplitude should be 1.5mm-2.0mm.When the vibration frequency is 58 Hz,the amplitude is 2 mm and the cutting direction is tangent to the tool tip trajectory,the peak value of tangential force in vibration cutting is about10% lower than that in conventional cutting,When the rotation speed is less than 14 rad/s,the specific energy consumption is about 5% lower than that of conventional cutting. |
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