Study On Mechanism Of High-speed Centrifugal And Low Stress Cutting Of Metal Bar

In industrial production,most parts of the processing began in the blank,and then after sheet metal,lofting or programming,CNC cutting and other processes,the production of metal parts into a single part.With the progress of industrial technology,the cutting method,especially the metal bar material cutting method becomes varied.Low stress cutting is a new way of cutting with low energy consumption,less material waste,which has caused the industry's attention gradually.However,the existing low-stress cutting process is slow,the cross-section quality is not high,and it is difficult to meet the needs of large-scale industrial production.In order to improve the efficiency and cross-section quality of metal bar,this paper presents a high-speed centrifugal and low-stress cutting method by means of circumferential no-gap loading.The crack initiation mechanism of the V-shaped groove at the cutting process is analyzed,including the crack tip stress field,and the stress field calculation formula of the crack tip and the stress intensity factor K_I and K_II is also obtained.The energy release of the crack,crack threshold rate criterion and the fissure angle of the bar are presented in this paper.The stress concentration factor formula of the V-shaped groove which is bottom radius 0.3mm-0.5mm and the error range is within 5%.According to the mechanism of crack initiation,the formula of bar loading force and crack propagation rate is established.On this basis,a critical stability curve is obtained,and the crack tip is extended to the maximum extent and applied to the cutting process.Based on the high speed centrifugal low stress cutting method,a new-type of cutting machine is designed,which is high speed centrifugal low stress cutting machine.The main parts and institutions of the cutting machine are designed,and the force structure,drive shaft and tension mechanism are also checked.The three-dimensional model of the cutting machine is established and the loading process is simulated by Adams software.The peak value of the alternating load value on the bar is above 2500N,which provides the data support for the cutting test.The control system with high-speed centrifugal low-stress cutting machine is designed,and the host computer,PLC and inverter selection are chosen.The proposed variable frequency loading curves are inserted into the PLC program.The design of the touch screen control interface program is achieved,which mainly includes the frequency curve editing,and the host computer and PLC,PLC and inverter communication.It is easy to call a variety of frequency curve used in the next material and to achieve the monitoring process.A high-speed centrifugal low-stress cutting test platform is built and 45 steel bars are tested.In the course of the experiment,an evaluation method of cropping mass is proposed,which combines the data of the cutting time,the instantaneous area and the height of the instantaneous zone.The four variable frequency loading curves designed in the experiment are compared with the critical stability curves obtained in this paper.Compared the prior blanking machine,the cropping results show that the cutting time of the new cutting machine designed in this paper is obviously reduced from 10-20s to 5s.Using the critical stability curve for cutting the quality of the block has improved significantly.