Papers by Author: Lian Fa Yang

Abstract: Forming accuracy is one of the important indicators to evaluate the forming quality of a tubular part by tube hydroforming. However, shape asymmetry on cross-section of tubular part produced by hydroforming with radial crushing (THFRC) inevitably appears due to the friction between the die and the part. In this paper, a circular tube is formed into a square cross-section one by THFRC under the various loading paths and the influence of friction on the forming accuracy of cross-section of the bulged parts is analyzed by using numerical simulation. The results show that the larger the tube is expended to, the lower the forming accuracy is under the identical coefficients of friction (COF); the larger the COF value is, the lower the forming accuracy is under a constant maximum hydraulic pressure. In a word, a reasonable loading path and a low COF value can observably improve the forming accuracy of the bulged tube.

Abstract: Hollow parts with variable cross-section are widely used in the area of automotive and aerospace industries due to their excellent properties. Wrinkling is one of the most common forms of instability in the process of manufacturing the parts. The minimum curvature of the cross-section profile of bugled workpieces is proposed in this paper to as a wrinkling indicator to characterize the form and extent of the wrinkle. The wrinkle distribution of 1Cr13Mn9Ni1N stainless steel tube in hydroforming with radial crushing under linear and constant hydraulic pressures is analyzed and the influence of the bulging methods on the wrinkling is investigated via finite element simulation. The results indicate that wrinkling under constant hydraulic pressure is more obvious than that under linear one, wrinkling in hydroforming with radial crushing is more serious than that in free hydro-bugling, wrinkling on the cross-section away from the middle cross-section is more distinct and the wrinkling on the side edge is obvious than that on the bottom of the bugled workpiece.