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Numerical and experimental investigations on Mannesmann effect of nickel‑based superalloy

Zhang Zhe, Liu Dong, Man Tongchi, Li Nan, Yang Yanhui, Pang Yuhua, Wang Jianguo

Archives of Civil and Mechanical Engineering

2022

Vol. 22, no. 3

art. no. e133

The preparation of nickel-based superalloy tubes by rotary tube piercing (RTP) process is still difficult due to the Mannesmann effect (central cracking phenomenon) has not been clarified. The combinations of numerical analysis and experiment verifications method were adopted in the study. The critical parameters for central cracking were determined by experiments. It was found that the evolution process of central cracking for nickel-based superalloy includes voids nucleation, growth and aggregation. Based on the obtained critical parameters, the evolutions of stress, strain, strain rate, temperature and damage were discussed by numerical simulation. By comparing the experiment results and simulation results, the Normalized Cockcroft and Latham (NCL) model was determined as the most suitable model. Considering the influences of temperature and strain rate on the damage threshold, the NCL model of Inconel 718 alloy was established by high-temperature tensile test. Based on the above results, it is found that the maximum shear stress promotes the plastic deformation, which provides necessary conditions for the generation of defects, and the maximum principal stress induces the generation of voids and expansion of micro-cracks, which directly leads to the central cracking. The essence of central cracking is ductile fracture under tensile stress.

Explorative study of rotary tube piercing process for producing titanium alloy thick-walled tubes with bi-modal microstructure

Zhang Z., Liu D., Yang Y., Pang Y., Wang J., Wang H.

Archives of Civil and Mechanical Engineering

2018

Vol. 18, no. 4

1451--1463

In order to solve the existing problems in the manufacturing of titanium alloy thick-walled tubes (TATWs), an innovative plastic forming method for the preparation of TATWs using rotary tube piercing (RTP) process was studied. In this paper, the advantages and basic principles of the RTP process were described. A new finite element model is established to study the effect of the thermal parameters on the RTP process of TATWs. Based on the control variable method, two key problems of rolling block and severe temperature rise in the RTP process were all solved, and the TATWs with bi-modal microstructure were produced by the self-developed piercing mill. In addition, the microstructure uniformity of the pierced tube was analyzed. Based on the experimental and numerical investigations, it's found that the RTP process is a viable process for manufacturing TATWs with bi-modal microstructure.