Investigation of co-induced crack initiation process by prestressed slotting and rotating-bending in low-stress cropping

Considering that the current low-stress cropping method for large-diameter metal bar has the disadvantages of large cutting force and drastic change of loading force, a new low-stress cropping method is proposed based on the co-induced crack initiation by rotating-bending and slotting. Based on the strength theory and fatigue damage theory, the dynamic bending cutting model is established, proving that the prestressed bending action reduces the slotted cutting and cracking forces. The formula of main cutting force during slotting considering rotation speed under the prestressed action is obtained by establishing simulation model combined with the experimental platform of the prestressed rotating-bending cutting and cracking process. Three types of initiation crack are proposed, and the reasonable process parameters for effective connection of slotting and ideal crack initiation type are obtained. The experimental results of 45 steel bar show that the cutting force is reduced to only 75.79% of the traditional cutting slotting, and the crack initiation force is reduced to only 1.88% of the traditional shearing force. Similarly, the test results of Q235 steel, 6061 aluminum alloy, and 304 austenitic stainless steel also show that the cutting force of prestressed slotting is reduced and the slotting and cracking connection can be realized, which can meet the requirements of low-stress slotting and cracking of the bar with large diameter. Graphical abstract Investigation of co-induced crack initiation process by prestressed slotting and rotating-bending in low-stress cropping