Numerical Simulation and Experimental Study On Non-Axisymmetric Spinning With a Groove At The Middle of The Tube

Spinning is widely used in aerospace and automobile industries, and non-axisymmetric spinning is developing with the increasing demand of irregular shape forming. Based on this, an avoidance groove at the middle of the tube (AGMT) which has potential application value in aircraft structure weight reduction is proposed and formed by using non-axisymmetric die-less spinning. The roller path is analyzed. The relationship between radial displacement of roller and the rotation angle of the tube is deduced. Based on the roller path, 3D finite element model is established. Then, the AGMT spinning experiment is carried out to verify the simulation results. The maximum deviation between the simulation and experimental results is less than 15%. It is indicated that the 3D finite element model established in this study is reliable and the method for the AGMT forming is feasible. The wall thickness and strain-stress distributions are analyzed. The severe wall thicken and thinning occur in the transition zones, so more attention should be paid to these positions. The depth of the groove has great impact on the forming quality. Deeper groove results in distortion and larger wall thickness difference. The research laid a foundation for the further development and optimization of the AGMT spinning.

A method based on circumferential strain distribution for roller path design in conventional spinning of thin-walled conical part with curved surface

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 were obtained through dividing the total required circumferential strain by the ultimate circumferential strain producing the spinning instability ( ε θult ). 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 performing 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 { ε θni } to produce the final TCPCS. The point-by-point distributed circumferential strain is half of the { ε θni } at the initial stage until reaches the half of ε θult , then it will keep the half of ε θult 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.

Forming Mechanism of Asymmetric Cylinder With Oblique–Straight Flange Spinning

The asymmetric cylinder with oblique–straight flange spinning has the potential to become a production process for this shape of the aerospace part. This complex shaped part was attempted to be formed by synchronous multipass spinning from a blank disk of 6061-O aluminum alloy with 1.15-mm thickness. The working principle of synchronous multipass spinning focuses on the fact that the radial and axial positions of the roller are synchronized with the spindle rotation to form the roller path. The roller path was calculated by dispersing a pass set into numerous points. The dimensional space between two points from the corresponding curves in a single-pass set was integrated into the trajectory around the circumference. Here, a pass set is the path along which the roller propagates in the two-dimensional space defined by the radial and axial directions. This shape was confirmed to be spun, and the formation mechanism of this spinning process was investigated. Contrastive experiments with paired arcs and pairs of straight lines as roller paths were performed on a spinning machine. The working condition of the cylinder wall with pairs of straight lines roller path was broken because of the higher pull resistance from the remaining part of the flange. The working condition of the flange of the paired arcs follows the law of shear spinning approximately that the cylinder wall forming does not comply. Suitable metal distributions for the flange and an appropriate force state for the cylinder wall are realized by the paired arcs roller path in the spinning process to form the asymmetric cylinder with oblique–straight flange. This provides a theoretical basis for the spinning of the asymmetric cylinder with the oblique–straight flange.