Showing papers on "Hydroforming published in 2003"

A prediction of bursting failure in tube hydroforming processes based on ductile fracture criterion

Abstract: Bursting is an irrecoverable failure mode in tube hydroforming, in contrast with buckling and wrinkling. To predict bursting failure in the hydroforming processes, Oyane's ductile fracture criterion is introduced and evaluated from the results of stress and strain productions obtained from finite element analysis. The region of fracture initiation and the bursting pressures are predicted and compared with a series of experimental results. It is shown that the material parameters used in the criterion can be obtained from the forming limit diagram. From the simulation results of tube bulging, the prediction of the bursting failure based on the ductile fracture criterion was demonstrated to be reasonable. This approach can be extended to a wide range of practical tube hydroforming processes.

Stator of a moineau-pump

Abstract: A Moineau stator includes a tube (10) having lobes (3) arranged in a configuration which is adapted to interact with a rotor and formed through a hydroforming process.

Front end module

Abstract: A front end module is described, wherein the module includes a plastic component connected to a metallic substrate The metallic substrate can be formed by hydroforming and shaped into a substantially unitary member The plastic component is then molded about the metallic substrate and simultaneously forms connections thereto at discrete locations along the length of the metallic substrate

Technology of sheet hydroforming with a movable female die

Abstract: An improved sheet hydroforming process is proposed and investigated experimentally and numerically. A movable female die keeps in contact with the deformed area of the sheet blank so that further deformation of the deformed area is restricted. Under the sealing, the sheet blank under the flange can be drawn in. So the hydroformed part has less thinning than the hydrobulge formed part only, and the limit drawing ratio of the sheet can be remarkably improved. This process is especially suitable for forming of small batch production of sheet metal parts with complicated shapes. The female die can be replaced with other female die of various shapes, and can also be made of very cheap materials such as plaster and hard wood instead of metal when the part number is very small. Thus complex-shaped sheet parts can be formed with less expensive tool systems. In this paper, the hydroforming processes of part A (without a movable die) and part B (with a movable die) were investigated by experiment and by elastoplastic FEM. The effects of various process parameters on the deformation of the sheet blanks were investigated. The forming conditions affecting wrinkling and rupture have been analyzed. The effects of friction and contacting force acting on the experimental results are also discussed.

A comparative study of implicit and explicit FEM for the wrinkling prediction in the hydroforming process

Abstract: The recent application of tube hydroforming in the automotive industry demands finite element analysis, since it is rapidly being used as an effective tool for the evaluation and optimisation of the design of hydroforming dies and processes. In this paper, attention is paid to the comparison of an implicit and an explicit FEM widely used for the hydroforming process. The influences of time scaling and mass scaling, which have been commonly used in order to save computational time in the explicit method, are especially investigated. The comparisons focus on the predictability of wrinkling and stress with various scaling factors in the explicit method. Through verifications with experimental results, a useful guideline in determining the scaling factors is proposed.

Tribological Issues in the Tube Hydroforming Process—Selection of a Lubricant for Robust Process Conditions for an Automotive Structural Frame Part

Abstract: In this paper, an overall review of tribological issues in the tube hydroforming process is presented. Guidelines for the selection of lubricants under the hydroforming process conditions are summarized following a description of existing testing methods and apparatus. A methodology of combined experiments and FEA was presented to determine the coefficient of friction in the hydroforming process in addition to selecting a proper lubricant for a given part and process design. Experimental results showed that thickness of the final part at critical regions, amount of axial feeding and axial force are strong indicators of lubricant performance whereas effect of lubrication on the part flatness, corner radius formation and box dimensions are found to be negligible. @DOI: 10.1115/1.1580526#

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.

Analysis and finite element simulation of tube expansion in a rectangular cross-sectional die

Abstract: The objectives of this paper are to propose a simple analytical expression, which can be used easily in a manufacturing plant to estimate the forming pressure, and to explore the plastic deformation behaviour of the tubes during the hydraulic expansion process in a rectangular cross-sectional die. At first, when considering the sticking condition, analytical expressions using the thin-walled and thick-walled theorems are proposed to determine the forming pressures needed to hydroform a circular tube into a rectangular cross-section with a desired corner radius. Then a series of finite element simulations of tube expansion are carried out to compare the simulation results of forming pressures with those from the proposed analytical expressions. The flow pattern of the tube during hydraulic expansion in a rectangular die is also examined. The effects of the friction coefficient between the die and the tube upon the thickness variations at certain positions during expansion and the thickness distribu...

Investigation of T-Shape Tube Hydroforming with Finite Element Method

Abstract: In this paper, the finite element method is used to investigate the cold hydroforming process of a T-shape tube. A series of simulations on hydraulic expansion, axial feeding and the counterforce of the tubes was carried out using the program DEFORM-3D. The influences of the process parameters such as the internal pressure, the fillet radius, and counterforce on the minimum wall thickness of formed tube are examined. A suitable range of the process parameters for producing an acceptable T-shape tube that fulfils the industrial demand was also found.

Hydroform process and hydroform product

Abstract: When hydroforming a steel pipe, a tubular deformation assisting member made of an incompressible material softer than the steel pipe is fitted on the outer peripheral surface of the steel pipe. The deformation assisting member is attached at least to an area corresponding to a projection provided at the inner surface of the die assembly, the projection being earliest brought into contact with the outer peripheral surface of the steel pipe during hydroforming. When hydroforming the steel pipe, the material of the deformation assisting member plastically flows near corner portions at which the deformation assisting member is brought into contact with the projection.

Method and apparatus for forming a structural member

Abstract: A method of forming a structural member includes hydroforming the blank (15) to form a hydroformed member (12) and finishing the hydroformed member by positioning the wall of the hydroformed member between a die surface (32) and an electromagnetic discharging element (16) having a non-circular cross-section, and actuating the electromagnetic discharging element so that the metallic wall of the hydroformed member presses against the die surface.

Method and apparatus for forming a threaded hole in a hydroformed part

Abstract: Method and apparatus are disclosed wherein a required threaded hole is formed in a hydroformed part with a single tool while the part remains in a hydroforming die cavity. In forming the threaded hole, a hole is first pierced in the wall of the part and then an annular region of the part extending about the hole is extruded inwardly to form an integral tubular neck defining a hole of predetermined depth. The hole is then expanded in a sizing operation to a diameter determined by the required thread to be formed therein by material displacement and the required thread is then formed in the wall of the hole in a material displacing manner.

Reliability Analysis of the Tube Hydroforming Process Based on Forming Limit Diagram

Abstract: Tube hydroforming has become an increasingly attractive manufacturing process in automotive industry due to it having several advantages over alternative methods. The forming limit diagram has been extensively used in metal forming as the criteria of formability. A method to assess the probability of failure of the process based on reliability theory and the forming limit diagram is proposed in this paper. The tube hydroforming process is affected by many parameters such as geometry, material properties, and process conditions. Finite element simulation was used to predict the relationship between the strain and these parameters, and a numerical method was applied to get the statistical distribution of the strain. Based on the forming limit band in the forming limit diagram, the reliability of the forming process can be evaluated. A tube hydroforming process of free bulging is then introduced as an example to illustrate the approach. The results show this reliability evaluation technique to be an innovative approach for product designers and process engineers to avoid failure during tube hydroforming.Copyright © 2003 by ASME