Abstract
Uniform-contact stretch forming based on loading at multi-position (UC-SF) was designed to substitute for conventional stretch forming (C-SF) in the manufacturing of qualified three-dimensional surface parts of a specified shape. Since the integral rigid clamps are replaced by discrete clamps, the sheet metal can be bent in a transverse direction (perpendicular to the stretching direction), and the sheet metal can be automatically warped to the die surface during the loading process. In this paper, finite element numerical simulations were performed to research the contact state evolution and its effect on forming precision by two kinds of loading modes (UC-SF and C-SF). The evolutions of contact state for spherical and saddle-shaped parts were analyzed in different steps, and the results reflect that, in UC-SF, the contact region of curved surface parts is gradually extended in a long strip, and the effective formed regions of the final parts can be in contact with the die surface. However, in C-SF, it is difficult for the final parts to be completely in contact with the die surface, especially spherical parts of a large curvature. Moreover, it is found that the noncontact region of the saddle-shaped part is susceptible to wrinkling in C-SF. Conversely, in UC-SF, the sheet metal can be constrained by contact with a die surface, such that the noncontact region and wrinkle defect disappear and high-precision parts are formed. Finally, stretch forming experiments were carried out and the perfect curved surface part was formed; thus, the experimental results verify the feasibility and effectiveness of UC-SF.
Highlights
The stretch forming process, as a significant method to form three-dimensional curved surface parts, has been applied in various industries; for example, the aerospace industry, high-speed train manufacturing, and modern architecture. [1,2,3]
By comparing the contact state evolutions in two kinds of loading modes, it can be observed curved of large curvatures as an example, numerical that Taking when the is surface appliedparts to form three-dimensional surface parts, the simulations sheet metalwere can performed in UC-SF, and the effect of contact state evolution on forming precision of sheet simultaneously be in contact with the die surface in a transverse direction, and the contact region is metal was9,extended compared and analyzed
The results of thespherical relevant study in this paper are summarized as follows: 1. In order for the effective formed region of the sheet metal to simultaneously be in contact with the die surface, uniform-contact stretch forming based on loading at multi-positions was designed
Summary
The stretch forming process, as a significant method to form three-dimensional curved surface parts, has been applied in various industries; for example, the aerospace industry, high-speed train manufacturing, and modern architecture. [1,2,3]. Method of loading trajectory for method of loading for longitudinal stretch forming wasand developed and discussed and longitudinal stretchtrajectory forming was developed and discussed [11], the sectional profile in [11], optimal the sectional state profile in extended optimal deformation waslocations extendedoftothe define the spatial locations deformation was to define thestate spatial discrete clamps He [12]of etthe al. 1b, is 1b, a new to form of discrete clamps grasped at both ofsheet the sheet metal, as shown in Figure is amethod new method to three-dimensional curved surface parts. Influence of contact state evolution on forming precision of curved surface parts. The formed curved surface parts by improving state between the sheet metal and thehigh-quality die. Formed high-quality parts with large curvature can satisfy the practical demands of modern society
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