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The primary motivation that drives the popularity of tube hydroforming, particularly in the automotive structural industry is the anticipation and expectation of significant savings compared to established methods, like stamping and welding. These potential savings can be divided into 6 main categories. They are capital (facilities and equipment), tooling and part costs, as well as, weight reduction, assembly simplification and performance improvement. Careful and knowledgeable consideration of these factors with the goal of achieving the best balance should lead to choosing the most advantageous manufacturing option. Overemphasis on one factor may lead to disappointing results in some of the others. This paper concentrates on the 1st 3 categories examining the impact of design decisions on overall cost. Due to the ‘newness’ of hydroforming, the possibility that design decisions made with partial knowledge may build in extra cost is higher.

Freely expand sections of a hydroformed part has gained a great deal of prominence in the burgeoning hydroforming industry. A number of misconceptions have arisen concerning what can be achieved in various forming situations and the cost of accomplishing them. This paper focuses on part cross section expansion and objectively discusses 5 different techniques. These are hydroexpansion without end feeding, hydroexpansion with end feeding, mechanical preforming, hydraulic preforming and elastomeric bulge forming. The 1st two happen in the hydroforming die while the 3rd, 4th and 5th occur prior to placement in this die. Careful analysis of the following factors can lead to choosing the ‘best’ option. Those that require consideration are demands on the material, material type, expansion size and position relative to any bends, amount of wall thinning and process robustness.

To simplify the number of design options that are available, decisions are often made early on to follow a particular system or set of design rules. This often builds in design compromises and extra costs that those involved either do not realize or have to live with because they are committed to the ‘system’. This thorough, relatively objective consideration of the relevant factors should lead to the technically best way to make a part with the most design flexibility and least cost for the part being analyzed.

Tube hydroforming is a technology that is new to many and proving it's merits as a viable and often superior alternative to welding tubular assemblies from stampings. This paper discusses how pressure sequence and high pressure hydroforming techniques work, how two functionally similar parts made by its respective technology compare and the dimensional stability of parts made with pressure sequence hydroforming. Data comparing the 2 processes show a substantial benefit when using pressure sequence hydroforming considering processing steps, hydroforming equipment, energy consumption, cycle time and floor space requirements. PSH dimensional stability compares very well with welded assemblies. High pressure dimensional data is unavailable which prevents comparison. Comparisons using specific information that has only recently become available should be interesting and valuable to anyone wanting to learn more about this emerging industry and technology.

The rapidly developing hydroforming industry has become almost a mainstream technology for the manufacture of automotive structural components. Technical information and claims are often incomplete, unspecific and unsupported by production experience and data. This paper contains data accumulated from a hydroforming process that has been in high volume production for 8 years. An objective presentation, explanation and discussion of this information gives a unique view of what is being done at present. It should act as an authoritative reference point against which dimensional capability claims can be judged.

The need for lighter, stronger, more rigid vehicle structures will increasingly require complex hydroformed structural tubes to increase strength, and decrease weight, cost and part count. This effort will increase the use of high strength, low alloy (HSLA) steel, in place of SAE 1006/1008 or 1010 steel. Traditional hydroforming techniques require the higher elongation of the latter materials. An alternative tube hydroforming process has been developed to successfully use these, and HSLA grades from 310 (945XF) to 552 (980XF) MPa minimum yield stress. This paper concentrates on hydroforming steel with a focus on HSLA. It will demonstrate to automotive designers available features such as local section expansion and reduction, hole piercing, achievable cross sectional shapes and the relationship between tube size, corner radii, and wall thickness.