As tubular hydroforming becomes a competitive process for the mass production of automotive parts, a tube's material properties must be consistent. To predict variations in material properties, many tube producers use the uniaxial tensile test. Because the specimens for the tensile test are collected before a tube is bent and welded, they are not always accurate. To predict variations in tube property accurately, it should be tested under a biaxial state of stress.

It's difficult to overemphasize the importance of cross section expansion when you're talking about successful and innovative hydroforming of steel tubing. Overemphasizing one aspect of the tube hydroforming design process can take attention away from others and result in less than optimal design....

Comparing and correlating two tests, a common bench test (twist compression) and a straight-tube corner-fill test, simulate hydroforming to find the coefficient of friction.

A new type of hydroforming press was recently developed for sheet applications. The new press incorporates data acquisition and control features for research purposes. Current press frame designs for tube and sheet forming are uneconomic for large forces. This press achieves a clamping force of 100 mN, which is absorbed by a single cast frame with a circumferential pretensioning system.

Design flexibility is something that all automotive designers want, but too often they lack a thorough understanding of what that means—what aspects of design flexibility apply to a certain part and their effect on cost. A methodology often is adopted when (or even before) a part development...

This article discusses tests that are used to evaluate flow stress in tube and why the uniaxial test is not suitable for this application. It discusses a bulge test, which stresses the tube biaxially, including tooling, software, and analysis tools for evaluating stresses.

This article discusses an approach to predicting failure in hydroforming prebent aluminum tubes. While strains are well researched for stamping sheet, this type of knowledge is lacking for hydroforming tubular components. Because the strains are different—prebent hydroformed tubular parts experience stress in the axial direction during bending, then in the circumferential direction during hydroforming—new methods for predicting failures are necessary. Researching these methods adds to the knowledge base of hydroforming, helping the technology gain further acceptance in manfacturing.

The bending characteristics of a tube depend on the material it is made of. Exceeding the allowable limits of this deformation results in unusable parts. The author relates his company's examination and comparison of the bending of two different seamless, extruded tubes: aluminum alloy and steel.

This article relates how a Florida-based company used hydroforming to produce titanium housings for implantable pumps for a Massachusetts-based manufacturer.

T-shapes and Y-shapes are the most commonly hydroformed exhaust system components for automobiles. This article reports on the investigation into the metal flow in Y-shape hydroforming by the Engineering Research Center for Net Shape Manufacturing (ERC/NSM) at The Ohio State University, which conducted several experiments using the tooling available at the SPS research center in Aalen, Germany.

This article examines two transitions that are occurring in the automotive industry—the change from stamping to hydroforming, and the substitution of aluminum where steel was used previously.

Hydroforming the parts in a vehicle structure can be of immense benefit on several counts, as a review of a recent project at the author's company can attest.

You can use several strategies for starting a hydroforming operation on a limited budget. Review your alternatives for selecting a press, fluid intensification system, and developing the tooling necessary for your operation before you take the plunge.