Experimental investigation of the effect of the circumferential loading of a rotary striking action cropping system

Abstract

The current paper reports the results of an experimental investigation into the effect of the circumferential loading on the quality of the billet cross-section and cropping time during a novel bar-cropping process. The new precision bar-cropping process technique uses a continuous circumferential strike on a metal bar with a pre-machined V-shaped notch. According to the relationship between loading mode and crack propagation, several different control curves of strike frequency versus time and stroke versus time were designed and applied in order to analyse how to improve the quality of the cropped billets and decrease the cropping time. The experimental results indicate that the ideal control mode is the combination of a linear decrement in the strike frequency—time curve and a linear increment in the stroke—time curve during the rotary strike cropping, by which higher cross-section quality and shorter cropping time may be achieved. Moreover, a new assessment method is proposed for the purpose of evaluating the cross-section of the cropped billet.

Research on hydraulic compensation and variable loading arm for a new-type low-stress cropping system

“…Zhao et al (Hua et al, 2006) (Zhao et al, 2007) proposed a low-stress cropping method with the variable-frequency vibration based on fatigue fracture mechanism and studied the method for heat stress prefabricating ideal crack at the bottom of V-shaped notch. Tang et al (Tang et al, 2010) proposed a new-type precision cropping system with controllable multiple pneumatic cylinders and radial impact, as well as built the calculating formula of the maximum load and the initial frequency. Zhang et al (Zhang et al, 2015) proposed a precision cropping system with high-speed and centrifugal action and analyzed the influence of the geometric parameters of the V-shaped notch on the cropping time.…”

New controllable and near net bar fine-cropping system

“…Some new different lowstress bar fine-cropping methods have been proposed based on the stress concentration in the last two decades. 4,[12][13][14][15][16] Although some of the disadvantages have been improved in some extent, the cross-section quality and the efficiency are still required to be improved indeed. Besides, due to lack of the correct and appropriate cropping mechanism, the optimal cropping load control strategy of the existing low-stress fine-cropping methods still remains unclear.…”

Investigation on the Crack Initiation of V-Shaped Notch Tip in Precision Cropping

“…At the present time, the common cropping method in industry is to shear bar directly with the common die, and this process is plagued with a big shearing force, a bad cross-section, a short lifetime die, and noise. Therefore, a new type of low stress cropping method was proposed and gradually used in industrial practice [1][2][3]. In the low stress cropping, the annular V-shaped notch on the surface circumference of metal bar is processed in advance and it skillfully utilizes the crack technology and the fatigue loading to make the crack checking and propagating along the prefabricated V-shape notch section for shearing the bar.…”