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.

Analysis of the effects of tool and process parameters in hydrodynamic deep drawing assisted by radial pressure

Abstract: Among the various techniques of sheet hydroforming, hydrodynamic deep drawing assisted by radial pressure (HDDRP) has showed good results to shape parts with uniform thickness distribution and high drawing ratio. In this paper, improving formability of the parts in HDDRP is taken into consideration and the effects of some geometrical parameters such as the die profile radius and the gap between the die and the blank holder, and some process parameters such as pressure path and friction coefficient are investigated on thickness distribution of cylindrical cups and punch force. The pressure path has a great effect on the formability. The results showed that increasing the maximum pressure reduces part thinning in the critical regions. Increasing the pressure above a certain value does not have a significant effect on the part forming, but it increases the punch force. The most appropriate pressure path for forming the part studied in this paper is 27 MPa. Furthermore, thinning of the part and maximum punch force decreases by decreasing the friction between the sheet and blank holder. Moreover, increasing the friction coefficient between the punch and sheet to a certain value (0.2) improves forming condition that results in decreasing thinning of the part. Increasing the friction coefficient more than this value does not have a significant effect on forming the part. Friction between the punch and the sheet does not affect the maximum punch force. The results also illustrated that by increasing the gap between the blank holder and the die to 1.2 mm which is more than the thickness of the sheet, thickness reduction of the part and maximum punch force decreases. Increasing the gap above this value does not have a significant effect on ease of sheet flow and improving part formability.

An approach to improve thickness distribution and corner filling of copper tubes during hydro-forming processes

Abstract: In hydroforming, the general technique employed to overcome the problem of die corner filling consist in increasing the maximum fluid pressure during the forming process. This technique, in other hand, leads to other difficulties such as thinning and rupturing of the final work piece. In this paper, a new technique has been suggested in order to produce a part with complete filled corners. In this approach, two moveable bushes have been used. So, the workpiece moves driven by both bushes simultaneously. In the first stage, system pressure increases until a maximum of 15 MPa, providing aninitial tube bulge. The results showed that the pressure in this stage have to be limited to 17 MPa to avoid fracture. In a second stage, bushes are moved keeping the constant initial pressure. The punches act simultaneously at the die extremities. Results show that the friction between part and die decreases during the forming process significantly. Also, by using this technique it is possible to produce a part with reasonable uniform thickness distribution. Other outcomes of applying this method are the lower pressures required to manufacture a workpiece with complete filled corners with no wrinkling.

3D ultrasonic imaging and contour detection in sheet metal hydroforming

Abstract: The paper describes an ultrasonic imaging system with a low number of transducers in a sparse 2D array for contour detection of specularly reflecting sheet metals in a hydroforming process. Image reconstruction is performed with a SAFT (synthetic aperture focussing technique) algorithm as a first step. Within the SAFT image, the contour of the metal sheet can be detected in a second step. Experiments and results are presented for a linear 1D aperture with 2D and a 2D aperture with 3D imaging capabilities, respectively. Contour detection results in contours with an axial reconstruction error of less than 1 mm for complex shaped 2D objects. Simple 3D objects have been imaged as well. Besides this, a modified approach (angle weighted SAFT, AW-SAFT) is presented to work around the lack of SNR under special conditions caused by specular reflections. Gaps in the contours can be "filled up" and poorly imaged parts of the contours can be amplified with this approach, whereas noise is reduced.

Exploring Liquid Impact Forming Technology of the Thin-Walled Tubes

Abstract: In order to realize the objective of lightweight manufacturing, the forming methods of thin-walled tubes are studied in this paper. Liquid impact forming, a compound forming technique of thin-walled tube using stamping and hydroforming processes, is presented in order to reduce the forming difficulty and increase the forming efficiency. A simple experimental tooling, including stamping device and tube hydroforming apparatus is developed. Forming experiments of stamping and liquid impact forming processes in rectangular cross-section dies are performed for 304 stainless steel tubes. The results of experiments show that the liquid impact forming technology is feasible, and it will be widely applied in the future.

Device for hydroforming metal elements

Abstract: A hydroforming device includes a top die and a bottom die, set between which is a metal element to be formed and which are pressed against one another during a hydroforming process. A relative movement of the two dies between the open condition and the closed condition is controlled by a hydraulic cylinder. The opening of the two dies during the hydroforming process, when the forming cavity is filled with liquid at a high pressure, is prevented by applying on the two dies a force generated by means of two wedge-shaped members, which are horizontally mobile, controlled by respective actuator means and having inclined surfaces in contact with corresponding inclined surfaces of a vertically mobile member. The mobile member and the hydraulic cylinder are set operatively in series between one and the same die of the two dies and the base of the hydroforming cell. On the opposite side, the two dies rest against a top cross member of the fixed structure of the hydroforming cell, which is rigidly connected to the base by means of two shoulders so that the vertical forces that are generated during the hydroforming process are discharged on the shoulders, which are subject to tensile stress.