Marginal-restraint mandrel-free spinning process for thin-walled ellipsoidal heads

Marginal-restraint mandrel-free spinning is an advanced technology for manufacturing ellipsoidal heads with large diameter-thickness ratios. Nevertheless, the spinning-induced residual stress, which greatly influences the in-service performance of spun heads, should be removed. In this study, the effects of annealing on the residual-stress relaxation behavior of 5052H32 aluminum alloy spun heads were investigated. It is found that the residual stress first rapidly decreases and then remains steady with the increase in annealing time at the tested annealing temperatures. The relaxation of the residual stress becomes increasingly obvious with the increase in annealing temperature. When the annealing temperature is less than 220 °C, there are no obvious changes in grain size. Moreover, the spinning-induced dislocations are consumed by the static recovery behavior, which decreases the residual stress during annealing. When the annealing temperature is approximately 300 °C, the broken grains transform into equiaxed grains. In addition, static recrystallization and recovery behaviors occur simultaneously to promote the relaxation of the residual stress. Considering the different stress relaxation mechanisms, a model based on the Zener-Wert-Avrami equation was established to predict the residual-stress relaxation behavior. Finally, the optimized annealing temperature and time were approximately 300 °C and 30 min, respectively.

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“…1a. A detailed spinning process has been reported previously [34,35]. A two-pass spinning process was used in this study.…”

Section: Materials and Experiments 21 Spun Heads And Annealing Schemementioning

confidence: 99%

“…In Refs. [34,35], the spinning parameters have been optimized to improve the forming accuracy and microstructures of ellipsoidal heads. However, the spinning-induced residual stress still significantly influences the in-service performance of spun heads.…”

Section: Introductionmentioning

confidence: 99%

Residual-stress relaxation mechanism and model description of 5052H32 Al alloy spun ellipsoidal heads during annealing treatment

et al. 2021

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“…Fig. 1 Marginal-restraint mandrel-free shear-expansion compound spinning [27] For large thin-walled heads, when the above marginal-restraint mandrel-free shearexpansion compound spin forming is adopted, the contour shows the following characteristics.…”

Section: Introductionmentioning

confidence: 99%

Research on marginal-restraint mandrel-free spinning of large thin-walled aluminum alloy heads with large bottom reserves

Zhu¹,

Huang²,

Li³

et al. 2023

Preprint

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The marginal-restraint mandrel-free spinning method can solve the problem of instability when spin-forming thin-walled head blanks. However, when shear-expansion compound forming is adopted for a large diameter head, the sinking phenomenon that occurs during the expansion spinning stage makes it impossible to accurately form the head. Through finite element simulation, it is found that the smaller the roller fillet radius is, the smaller the feed ratio, and the larger the angle is between passes, the more obvious the sinking phenomenon and the worse the forming accuracy. It is further revealed that the mechanism of the sinking phenomenon is shear deformation in addition to expansion deformation in the expansion spinning stage. To solve the sinking problem, this paper proposes a marginal-restraint mandrel-free spinning method with a large bottom reserve. Research shows that a larger roller fillet radius and more passes can improve the contour accuracy of the head by using the cylindrical roller structure. Finally, it is verified that the new spinning method can achieve accurate forming of large thin-walled aluminum alloy heads with a diameter of 2250 mm and a forming angle of 60°.

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“…The destabilization and cracking problems are difficult to suppress for both molded spinning and the center-restraint mandrel-free spinning process, especially for the thin-walled blanks with large diameter-to-thickness ratios. To address these issues, a marginal-restraint mandrel-free spinning method is proposed [27][28][29][30][31][32][33][34]. As shown in Figure 3, the blank is fixed circumferentially to the cylindrical support fixture with a press plate to achieve the marginal restraint, and it rotates on the spinning machine's table with the cylindrical support fixture.…”

Section: Introductionmentioning

confidence: 99%

A Two-Step Marginal-Restraint Mandrel-Free Spinning Method for Accuracy in Forming Large, Special-Shaped Aluminum Alloy Tank Domes

Zhu

Huang

et al. 2023

Metals

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The special-shaped tank dome of a launch vehicle is a large, thin-walled, curved structure that is difficult to form using the conventional center-restraint spinning method. This study proposes a two-step marginal-restraint mandrel-free spinning method for forming large domes. The finite element analysis results indicate that a larger roller fillet radius and larger feed ratios lead to a larger upper convex angle and the minimum thickness value for the bottom contour. This study explored the impact of shape parameter variations on the upper convexity and transition rounding angle on forming accuracy. The results show that the convexity of the bottom of the special-shaped domes increases with a larger roller fillet radius and larger feed ratios while the overall height decreases. The forming accuracy is adversely affected by larger transition rounding angles and smaller upper convexities. For the accurate forming of domes, the mutual coupling influence during two-step forming should be considered, and a suitable process and suitable trajectory compensation parameters must be carefully selected. Finally, the study verified that a two-step marginal-restraint mandrel-free spinning method with a 10 mm roller fillet radius, a 2 mm/r feed ratio, and the corresponding trajectory compensation can achieve the precise forming of 2250 mm thin-walled special-shaped domes.

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Marginal-restraint mandrel-free spinning process for thin-walled ellipsoidal heads

Cited by 11 publications

References 35 publications

Residual-stress relaxation mechanism and model description of 5052H32 Al alloy spun ellipsoidal heads during annealing treatment

Residual-stress relaxation mechanism and model description of 5052H32 Al alloy spun ellipsoidal heads during annealing treatment

Research on marginal-restraint mandrel-free spinning of large thin-walled aluminum alloy heads with large bottom reserves

A Two-Step Marginal-Restraint Mandrel-Free Spinning Method for Accuracy in Forming Large, Special-Shaped Aluminum Alloy Tank Domes

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