Showing papers on "Hydroforming published in 2002"

Prediction of forming limits and parameters in the tube hydroforming process

Abstract: Determination of process limits and parameters for hydroforming was conducted applying widely known plasticity, membrane and thin-thick walled tube theories. Analytical predictions were compared with experimental findings. Simple but useful analytical models to predict buckling, wrinkling and bursting as well as axial force, internal pressure, counter force and thinning in tube hydroforming were verified with experimental results.

Comparison of Implicit and Explicit Finite-Element Methods for the Hydroforming Process of an Automobile Lower Arm

Abstract: Tubular hydroforming has recently attracted increased attention in the automotive industry and the finite-element analysis is an effective tool for evaluation and optimisation of the design of hydroforming dies and processes. In this paper, a comparison is made of an implicit and an explicit finite-element method, widely used for the hydroforming process. The influence of time scaling and mass scaling, which have been commonly used in order to save computational time, in an explicit method, for the hydroforming simulation of an automotive lower arm, are investigated. The comparisons focus on the accuracy of the predicted geometrical shape and the stress in the explicit method with various scaling factors.

Ring Hoop Tension Test (RHTT): A Test for Transverse Tensile Properties of Tubular Materials

Abstract: Tube hydroforming has been receiving increasing attention, particularly for making automotive components. In this process, tubular metal pats are formed within a die cavity by forcing pressurized fluid inside so that the part expands into its final shape in a die. Process control requires an improved knowledge of mechanical properties in the transverse direction of tubular products. Several laboratory tests have been used to evaluate tube properties. One test method that has been used for zirconium alloy cladding tubes in the nuclear industry is the ring test, in which an expansion force is applied from inside the ring by separating two die inserts. In the present work, this test method is adapted to determine the hoop stress-strain curve of tubular materials. The new protocol allows measurement of the tensile properties without altering those properties in specimen preparation, which occurs using the conventional flattened strip tensile test. This paper presents the new test and data analysis procedure, along with typical data for a commercial steel hydroforming tube.

Method of hydroforming articles and the articles formed thereby

Abstract: A hydroformable frame element is formed from the combination of at least two elements The at least two elements are designed with a partially overlapping region, with an annular space defined within the overlapping region The annular space is filled with adhesive, which is then cured to bond the at least two elements together The adhesive bond is designed to withstand the stresses caused by the hydroforming operation and to retain its strength so that the hydroformed article is then usable as a vehicular frame element

Application of two dimensional (2D) FEA for the tube hydroforming process

Abstract: Use of FEM in the metal forming process has been a proven analysis tool. Two-dimensional FEA for simplified sections can help to reduce time and cost in part, tooling and process design in tube hydroforming technology as it is a relatively new process, and the existing experience and knowledge base is not as broad as with other forming processes. Some case studies are presented to demonstrate the use of two-dimensional FEA in the hydroforming process. Upon verification through comparison of FEA predictions with experimental results, further planned simulations are conducted to generate simple design rules on geometrical and process parameters.

Manufacture of an automobile lower arm by hydroforming

Abstract: An automobile lower arm has been fabricated in a prototype form by hydroforming with the aids of numerical analysis and experiments. For the numerical process design, a program called HydroFORM-3D developed here on the basis of a rigid–plastic model, has been applied to the lower arm hydroforming. The friction calculation between die and workpiece has been dealt with carefully by introducing a new scheme in three-dimensional surface integration. To accomplish successful hydroforming process design, thorough investigation on the proper combination of process parameters such as internal hydraulic pressure, axial feeding and tool geometry has been performed. Results obtained from numerical simulation for a lower arm in the hydroforming process are compared with a series of experiments. The comparison shows that the numerical analysis successfully provides the manufacturing information on the lower arm hydroforming, and it predicts the geometrical deformation and the thinning.

Apparatus for performing a hydroforming operation

Abstract: A hydroforming apparatus includes upper and lower platens that are connected together by tie rods extending through respective compression tubes. An upper die section is carried on the upper platen by a generally C-shaped suspension arm, while a lower die section is carried on the lower platen. The upper and lower die sections have recessed areas formed therein that define a die cavity. Lift assemblies are provided on the lateral ends of the hydroforming apparatus for selectively elevating the lower die section upwardly into engagement with the upper die section. When the lower die section is elevated by the lift assemblies, a workpiece is enclosed within the die cavity. A bolster is then moved between the hydroforming die and the lower platen. A cylinder array containing a plurality of pistons is next hydraulically actuated so as to securely clamp the hydroforming die between the cylinder array and the lower platen. While the cylinder array is actuated, pressurized fluid is supplied within the workpiece, deforming it into conformance with the die cavity.

Method of manufacturing structural components from tube blanks of variable wall thickness

Abstract: A method for forming a tubular structural member includes the steps of cold forming a tube blank (10) to have a longitudinally variable but circumferentially constant wall thickness (t1, t2, t3) and forming the blank into the desired structural member (90). Preferably, the forming step involves hydroforming.

Punch for piercing and sealing hydroformed parts

Abstract: A punch for piercing and sealing hydroforming parts has a roll forming surface that produces an internal rolled edge portion in a formed part immediately following the punch piercing the part wherein the rolled edge portion acts to effect a tight high pressure seal between the part and the punch as the punch continues to form a required hole in the part. The roll-forming surface extends either partially or completely about the punch in determining the extent of the rolled edge portion in the part that it produces and is located between an end portion that effects the piercing operation and a larger finishing portion that completes the formation of the required hole.

Hydroforming process and apparatus for the same

Abstract: Providing a method of hydroforming a tube where the hydroformed diameter is less than the tube length and a hydroforming die having two or more die members having an internal shape same as the tube shape and an internal cavity having the desired formed shape. Where the said die members are movable to an opened and closed position such that the tube is placed inside the die members cavities and the tube ends are sealed and hydraulic pressure source is connected to the interior of the tube and thereby expanding the tube so as to conform to the shape of the said die members cavities. And where the directions of opening and closing of the said die members are in the direction of the said tube axis such that the amount of force necessary to hold the die members in a closed position during said step of expanding, is kept to a minimum.

Method of fabricating a gas tank

Abstract: A method of making a gas tank includes hydroforming two halves and welding the halves together Two types of welds are used in welding the two halves together, tack welds for holding the two halves together, and stitch welds to complete the welding of the two halves Additional steps are taken prior to the finishing stitch welds Reinforcement is added where necessary Double tanks, for both gasoline and oil, are also fabricated by essentially the same method steps

Metallic sheet hydroforming method, forming die, and formed part

Abstract: A sheet hydroforming method is disclosed wherein two stacked metallic sheets are clamped between a pair of upper and lower dies 10, 11 and a fluid is introduced and pressurized between mating surfaces of the metallic sheets, causing the metallic sheets to bulge into a space defined by die cavities 10 b and 11 b A thru-hole 11 d for introducing the fluid is formed in one of the dies so as to lead to a holding surface of the die, while a pierced hole for introducing the fluid is formed in one of the metallic sheets in a portion of the one metallic sheet which portion is in contact with a holding surface 10 a ( 10 b) of one of the dies, the pierced hole being positioned with the thru-hole 11 d, then the fluid is introduced in a pressurized state between mating surfaces of the metallic sheets from the thru-hole through the pierced hole, thereby causing the metallic sheets to bulge According to this method, a pressurized fluid can be introduced between the mating surfaces of blanks easily without leakage of the fluid Not only the efficiency of the sheet hydroforming method but also the dent resistance of a formed part can be improved