Hydroforming

About: Hydroforming is a research topic. Over the lifetime, 2796 publications have been published within this topic receiving 26293 citations. The topic is also known as: Bulge forming.

Apparatus and method for opening and closing stacked hydroforming dies

Abstract: A hydroforming apparatus for concurrently performing two or more hydroforming operations includes a frame that is sized to support hydroforming dies in a stacked relationship. Each of the dies includes a pair of cooperating die sections having respective recesses that define a die cavity. Guide pins and actuating cylinders, attached to platens on which the die section are supported, move in coordination with a ram and assist in moving die sections that are distant from the ram. When the die cavities are opened, hollow tubular blanks are inserted between the spaced apart die sections of the first and second die. Next, the ram and the support mechanism move such that the pairs of cooperating die sections of the first and second dies engage one another. End feed cylinders are then moved laterally into engagement with the end the tubular blanks to facilitate the filling thereof with a hydroforming fluid. The pressure of the fluid within the tubular blanks is then increased to expand such a magnitude that the tubular blanks are expanded outwardly into conformance with the respective die cavities. Thus, the hydroforming apparatus is capable of performing two or more hydroforming operations concurrently to decrease the overall amount of operation cycle time and to increase overall productivity.

Investigation on the effect of through thickness normal stress on forming limit at elevated temperature by using modified M-K model

Abstract: The formability can be improved in warm/hot sheet hydroforming due to two important factors of temperature and through thickness normal stress. An extension of the M-K model was presented in this paper with the liquid pressure induced through thickness normal stress taken into account. The through thickness normal stress was introduced by using the general form of the Hill48 criterion. The combined effect of temperature and through thickness normal stress on the increase of FLD0 is achieved by applying a proposed temperature dependent constitutive equation for 5A06 aluminum alloy (a Chinese designation of Al-Mg alloy, corresponding to the ASTM designation of 5056 aluminum alloy) into the M-K approach. The Newton–Raphson method is used in the numerical procedure and it is proved to be stable and correct. The yield loci show a significant dependence on temperature and through thickness normal stress. Both size shrinking caused by the elevated temperature and location shifting due to the increasing thickness normal stress of the yield loci are observed. Comparison of the experimental FLDs of AISI-1012 low carbon steel (an AISI designation of steel) at plane stress and room temperature, STKM-11A steel (a Japanese designation of Steel Tube Kozo Machine) for tube hydroforming at room temperature and 5A90 aluminum alloy (a Chinese designation of Al-Li alloy) at plane stress and elevated temperature with the theoretical results show good agreements. The effect of key parameters, such as inhomogeneity factor f0, n value, m value and initial thickness T0, grain size d, initial surface roughness R0, show a strong dependence on FLDs and increase of FLD0. The increase of FLD0 is formulized in a full quadratic form, which is a function of temperature and through thickness normal stress. The left quadrant of FLD was determined by the cylindrical warm hydromechanical cup deep drawing, which shows a good accordance with the predicted results by using the modified M-K model.

Thickness distribution of a hydroformed Y-shape tube

Abstract: The process of hydroforming a Y-shape tube was investigated through numerical simulation and experiments. Characteristics of three different forming stages were studied. Thickness distribution of these three stages and the thickness of typical location that varies with internal pressure during forming process were analyzed when the calibration pressure was 136 MPa. It is shown that thickness distribution of the leftward fillet transition region is the thickest, rightward takes the second place, the top of the protrusion is the thinnest after forming. The influence of different calibration pressures on the thickness distribution was studied through numerical simulation. It is indicated from the simulation results that with the increase of calibration pressure, the biggest thickening rate is not obviously changed; however, the highest thinning rate increased significantly.