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In the die-less spinning of the conical part, the forming state changes during the spinning process and depends on the forming parameters, which has a critical effect on the forming quality of the spun part. In this paper, a criterion of the forming states is established, and its dependence on the forming parameters is investigated. It is found that the formed wall thickness changes during die-less spinning. According to the formed wall thickness variation degree, three forming states are defined: shear spinning state ( t f = t 0 s i n α , where t 0 and t f are the initial and formed wall thicknesses, respectively, and α is half-cone angel), the conventional spinning state ( t f > 0.9 t 0 ), and transition state between the shear and conventional spinning states ( t 0 s i n α < t f ≤ 0.9 t 0 ). The distribution of stress and strain in three forming states is obviously different. The die-less spinning always proceeds in the sequence of shear spinning state, transition state, and conventional spinning state. The initial forming state may be any one of them, which is mainly determined by the diameters of the blank and general mandrel. Thus, the quantitative dependence of initial forming state on the diameters of blank and general mandrel is further analyzed, and a criterion for the initial forming state is correspondingly established. In addition, the influence of forming parameters, including the blank parameters, mold parameters, and process parameters, on the criterion for the initial forming state in die-less spinning is revealed. This paper could improve the understanding of the deformation mechanism in die-less spinning. [ABSTRACT FROM AUTHOR]

The deformation characteristics of GH3128 were explored via tension experiments in the temperature region of 1023-1173 K and strain rate range of 0.001-1 s−1. The stress decreased as the temperature increased and the strain rate decreased. The obtained strain–stress curves were classified into two types: hardening and hardening–softening curves. To realise the unified prediction of the two types of stress–strain curves, a modified Johnson-Cook (JC)-Zerilli-Armstrong (ZA) constitutive model was established based on the deformation characteristics, in which the modified JC and ZA models were used to express the work-hardening and softening sections, respectively. At the same time, the peak strain was described as a function of lnZ to separate the work-hardening and softening sections. The comparison results suggest that the JC-ZA constitutive model can precisely express flow behaviour. In addition, a hot processing map for the GH3128 alloy was developed. The results showed that the high-energy dissipation region was mainly concentrated in the domain with a lower strain rate and higher temperature, where the instability domains were not included. The optimised working region was determined to be 1098-1173 K and 0.001-0.3 s−1. Microstructural observations showed that the main deformation mechanism of the stable regions was dynamic recovery (DRV), with a small amount of dynamic recrystallisation (DRX). These studies provided a theoretical basis for the processing design of GH3128 alloy components. [ABSTRACT FROM AUTHOR]

Multi-pass conventional spinning is the preferable forming technology for the forming of thin-walled conical part with curved surface (TCPCS) in aerospace field. In multi-pass conventional spinning, the design of roller path is a critical problem due to its sensitive effect on the deformation mode and forming defect during spinning process. However, at present, the roller path is still mainly designed based on experience and trial and error, which seriously restricts the high-performance spinning of TCPCS. In this work, a new quantitative method based on circumferential strain distribution was developed for the roller path design in multi-pass conventional spinning of TCPCS. In this method, the total required circumferential strain for the forming of final TCPCS by conventional spinning was firstly determined. Then, the spinning passes number was obtained through dividing the total required circumferential strain by the ultimate circumferential strain producing the spinning instability. As for the roller path profile in each pass, it is divided into two sections and determined, respectively, i.e., the attaching mandrel section and the preforming section. The attaching mandrel section presents the same profile of mandrel. The profile of preforming section is determined point by point by distributing the rest of circumferential strain to produce the final TCPCS. The point-by-point distributed circumferential strain is half of the the total required circumferential strain in the initial stage until it reaches the half of the ultimate circumferential strain, and then, it will keep the half of the ultimate circumferential strain to the end. The proposed new method of roller path design was validated by finite element simulation, where well spinning stability, wall thickness distribution and roundness were obtained. This method provides a quantitative, high-efficient and universal way for the roller path design in conventional spinning of TCPCS. [ABSTRACT FROM AUTHOR]