2018 年 12 巻 7 号 p. JAMDSM0120
Aiming at that the instability of the loading force in the low-stress cropping causes the poor quality of the bar cross-section, a precision cropping system with hydraulic compensation and variable loading arm is proposed. The working principle of the cropping method is introduced. The stability of the loading force acting on the bar during the blanking process is analyzed, a method for evaluating the stability of the loading force is proposed and on this basis the fixed speed of the main shaft is determined to be 1000r/min. The research results show that the stability of the loading force is improved by applying the reasonable hydraulic compensation force. With the help of stress concentration coefficient and stress intensity factor, the required critical loading force before and after the crack initiation at the V-shaped notch tip is obtained and it is determined that the best loading arm after crack initiation is 24.7mm. Based on it, the abrupt change problem of the critical loading force before and after the crack initiation is further solved. The experimental results also show that the high quality cross-section can be obtained by the proposed cropping method.