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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]

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]