Showing papers on "Hydroforming published in 2005"

Loading path optimization of tube hydroforming process

Abstract: Optimization methods along with finite element simulations were utilized to determine the optimum loading paths for closed-die and T-joint tube hydroforming processes. The objective was to produce a part with minimum thickness variation while keeping the maximum effective stress below the material ultimate stress during the forming process. In the closed-die hydroforming, the intent was also to conform the tube to the die shape whereas in the T-joint design, maximum T-branch height was sought. It is shown that utilization of optimized loading paths yields a better conformance of the part to the die shape or leads to a higher bulge height. Finite element simulations also revealed that, in an optimized loading path, the majority of the axial feed needs to be provided after the tube material yields under the applied internal pressure. These results were validated by conducting experiments on aluminum tubes where a good correlation between the experimental results and simulations were obtained.

Friction tests in tube hydroforming

Abstract: The objective of this paper is to propose a friction test method to evaluate the performance of different kinds of lubricants and determine their coefficients of friction in tube hydroforming processes. A self-designed apparatus is used to conduct the experiments of friction tests. The coefficient of friction between the tube and the die at the guiding zone is determined. The effects of the internal pressure and the axial feeding velocity on the friction forces and coefficients of friction for various lubricants are discussed. From the experimental results, it is known that MoS2 corresponding to a coefficient of friction of 0.018 is the best lubricant among the evaluated lubricants during tube hydroforming processes.

Hydroforming method and apparatus

Abstract: PROBLEM TO BE SOLVED: To provide a hydroforming method capable of swelling a part of a hollow work to be hydroformed to be large outwardly without being affected by the thickness of the workpiece, and preventing occurrence of any wrinkles or thickness reduction, and favorable in the aspect of the equipment cost. SOLUTION: In the hydroforming method, a hollow workpiece 1 is arranged in a hydroforming die K, and a part of the workpiece 1 is swollen outwardly by applying the axial compressive force while applying the hydraulic pressure inside the workpiece 1. The hydroforming die K is split into partial dies 10b, 11b in contact with the workpiece 1, and permanent dies 10a, 11a other than the partial dies. The hydroforming is performed while oscillating the partial dies 10b, 11b in the axial direction of the workpiece 1. COPYRIGHT: (C)2007,JPO&INPIT

Methods of and apparatus for forming hollow metal articles

Abstract: In hydroforming of hollow metal articles in a die, such as pressure-ram-forming procedures, a method of decreasing cycle time of the forming process, while ensuring acceptable product properties and avoiding failures, by modeling the process using finite element analysis to establish a pressure-time history that optimizes the forming operation and applies failure limits to selected variables such as minimum wall thickness or maximum strain rate, and transferring this pressure-time history to a computer controlling the forming process. Thermocouple and/or continuity sensors are incorporated into the die wall and connected to the computer so as to provide active feedback from the die to the control of the process.

Development of a Moderate Temperature Bending Process for Magnesium Alloy Extrusions

Abstract: An appropriate temperature (150-200°C) bending process has been developed for AZ31 and AM30 magnesium alloy tubes, and the optimum bending process parameters were obtained using a Design of Experiments (DOE) method. The development of this process was one of the key factors for use of magnesium tubes in automotive components for vehicle weight reduction. The tensile properties and deformation microstructure of magnesium alloys at elevated temperatures indicated that temperature of 150-200°C which might be suitable for hydroforming and other forming processes.

A process for the manufacture of a hybrid element comprising a metal skin

Abstract: Hybrid metal-plastics elements are habitually manufactured by casting/moulding the resin into the rear side of a pressed metal shell. According to the invention, the hybrid element comprising an outer metal skin is manufactured in one step consisting of injection moulding, using the molten injection moulding material as the hydraulic fluid for hydroforming the shell.

Study of Hydroforming Lubricants with Overbased Sulfonates and Friction Modifiers

Abstract: Due to the high cost of hydroforming equipment, attempts have been made to model this process using bench testing. While tensile and twist compression tests have yielded promising results, they do not simulate any single metal forming process. In this study we investigated the use of expansion zone, guiding zone, and twist-compression tests to simulate hydroforming processes and evaluated various overbased sulfonates and organic friction modifiers performance. The amorphous overbased magnesium sulfonate improved the performance of the hydroforming oil in the expansion zone and provided no harm in the guiding zone, while the crystalline overbased calcium sulfonate provided no harm in the expansion zone and improved performance in the guiding zone. It was found that the friction modifiers tested display an antagonism, where, as the expansion zone performance increased, the guiding zone performance decreased. Additionally, we found in twist-compression testing that the initial coefficient of friction displayed a small correlation with the guiding zone test (from r = 0.26–0.47), while the failure time displayed a small correlation with the expansion zone test (r = 0.36–0.40).

Numerical Investigation into the Effects of Bending Boost and Hydroforming End-Feed on the Hydroformability of DP600 Tube

Abstract: The work presented in this paper utilizes advanced FE models of the pre-bending and hydroforming process to investigate the effect of bending boost and hydroforming end-feed on the hydroformability of a tube. A model of a rotary-draw tube bender was used to simulate pre-bending of DP600 tube after which models of hydroforming of the pre-bent tube were run with various levels of end-feed. By varying bending boost from low (LB), medium (MB) and high (HB), consistent trends in the strain and thickness distribution within the pre-bent tubes were observed. Three end-feed levels were simulated and showed that an increase in end-feed improved formability during hydroforming. The sensitivity of the models to bending boost was shown.

Quick change assembly for hydroforming punches

Abstract: A punch assembly used with a hydroforming die includes a punch cylinder for mounting to the hydroforming die and having a movable rod. The punch assembly also includes a punch for piercing an opening in a tubular member disposed in the hydroforming die. The punch assembly further includes a quick change assembly interconnecting the rod of the punch cylinder and the punch for allowing the punch to be removably attached to the punch cylinder.

Combination of hydroforming and joining

Abstract: Manufacturing of complex tubular workpieces often requires medium-based forming processes. Because of the inaccessibility to the inside of the parts, joining of attached parts and part handling are difficult. Loss of accuracy during thermal joining is another disadvantage. A new method of spot-joining by forming is a combination of hydroforming and clinching or hydroforming and self-pierce riveting. In contrast to the standard method the clinching or self-pierce riveting is done without die. A high pressure fluid undertakes the task of the die during joining. This die-less procedure also extends the range of applications to areas which are not covered by standard techniques. By integrating joining into the hydroforming process, assembly processes can be shortened. In order to exploit velocity dependent material properties, for example increase in formability and decrease of spring back, self-pierce riveting during the hydroforming process by means of impulse load has also been researched among other conventional quasi-static force transmissions. Numeric simulations were used for the theoretical description of the procedure. One goal of the simulations is the characterisation of the most influential parameters on the process as a function of the material properties, tool kinematics/-geometry and of the friction conditions. The simulation results permit not only the characterisation of the process, but also the theoretical predetermination of optimal joining parameters for various material and geometry combinations with fewer experiments.