New Technology and Experimental Research on Thick-Walled Tube Fatigue Impact Loading Precision Separation

• Published in: Metals (Basel ) 2022-05, Vol.12 (5), p.837
• Main Authors: Zhao, Ren-Feng, Gao, Wei-Cheng, Zhang, Dong-Ya, Xiao, Xu-Dong, Liu, Yan-Wei, Pan, Run-Ze
• Format: Article
• Language: English
• Subjects: control curve; Crack initiation; Crack propagation; Efficiency; Fatigue cracks; Fatigue failure; Impact loads; Load; Metal fatigue; Microcracks; New technology; Propagation; Quality assessment; Raw materials; repeated impact load; Repeated loading; Sawing; Separation; Steel tubes; Stress concentration; stress concentration effect; Thick walls; thick-walled tube
• ISSN: 2075-4701; 2075-4701
• DOI: 10.3390/met12050837

Traditional separation methods for thick-walled metal tubes include turning and sawing, which suffer from wasted raw material and low efficiency. In view of this, this paper proposes a new process of using impact load to promote crack generation and tube separation. Based on the principles of radial repeated impact load, stress concentration effect and fatigue fracture, the rapid initiation and stable expansion of tube fatigue crack are promoted. In addition, the crack initiation mechanism of the tube V-notch root cracks under radial repeated load when the tube is in a restrained state. For the experimental study of the GCr15 steel tube, a multistep decline frequency time tube separation control curve with an initial frequency from 4 Hz to 31 Hz and termination frequency from 1 Hz to 8.5 Hz was designed, and the precision tube separation device is loaded by pneumatic fatigue shock to achieve tube precision separation. In addition, a tube fracture quality evaluation method is proposed. According to the test results, the stress concentration effect of V-notch can significantly reduce the average stress in the process of tube fatigue separation and accelerate the generation of microcracks. Under the continuous action of repeated impact load, the loading method of multistep decline can effectively control the rapid crack initiation and stable expansion of the GCr15 tube V-notch root crack. Moreover, the tube final fracture region has relatively small defects, which can obtain good fracture quality.