Cold form titanium with hot forming performance: Call for partners

If you've worked with Titanium, you know that cold working it comes with some real restrictions.  What if it didn't have to be that way?

Ultrasonic-assisted forming has been studied since the 1950s, with industrial application in wire drawing and tube bending since the early 1970s. It's carried out by applying vibration to forming dies during deformation using frequencies in the kilohertz range and displacements in the micrometer range. A large body of research has documented several notable effects which are summarized below:

• Reduction in forming stress of more than 75%

• 10-15% increased LDR in deep drawing

• 23% force reduction in extrusion

• 60% friction reduction in wire drawing

• Significantly improved surface finish

• Energy reduction of 99% compared to hot forming

U.S. Army Aviation Research

The U.S. Army Aviation Research and Development Command (AVRADCOM) published a paper in 1981 titled Ultrasonic Cold Forming of Aircraft Sheet Materials.  This report documented significant improvements in bending and drawing, achieving plasticity in Ti 6Al-4V that allowed forming a 60 degree bend for a helicopter main rotor blade in one step.  It was impossible to replicate this operation for comparison without ultrasonic vibration, as the material simply cracked when no vibration was applied. The following excerpt from this paper (page 1) highlights several of the challenges involved with titanium sheet forming:

"This type of cold forming could have a decided impact on the fabrication of helicopters. The cost effectiveness of the process would be reflected almost immediately in the production of various sheet metal shapes, and in particular the nosecap of the helicopter rotor blade. In this program, ultrasonic activation was examined as a technique to minimize incipient cracks, reduce springback, improve repeatability of the blade geometry, and maintain high fatigue strength."

...

"Most rotor blades presently in service throughout the world use metallic sheet that has been hot formed for the leading edge erosion-resistant nosecap. Ordinarily the nosecap is stainless steel, titanium alloy, or nickel. These materials are expensive, and the forming is usually a slow, costly process, sometimes involving high temperatures which degrade the surfaces. For example, the forming of titanium alloy sheet material into aeronautical surfaces is usually accomplished at 1400-1600º F. Expensive chemical agent and cleaning procedures are required to restore the titanium surfaces after such heating.

Titanium also exhibits springback during the sheet forming process. This springback involves elastic recovery of the material, which is usually a function of the elastic strain present in the total deformation. Many attempts have been made to describe the forming process theoretically and to accurately predict springback for a variety of materials under forming conditions. If sufficient stress is applied to exceed the elastic limit and eliminate springback, the metal has a tendency to crack.

Ultrasonic cold forming would minimize the required cleaning procedures, and would be expected to reduce springback reduce incipient cracking, improve the repeatability of blade geometry, and maintain high fatigue strengths."

This research represented the first of three planned phases for this project.  Unfortunately the project did not proceed to the second phase, as at the same time, composites had advanced to the point that they fulfilled the AVRADCOM's desired application.  

Current research

​In the nearly 45 years that have passed since this report was published, composites have made enormous advancements, with further research into ultrasonic forming largely left to academia. At the same time, composites are now well-understood enough that we can determine that there is still an application for forming titanium, as hot-forming of titanium is still in use today. While some of these applications may be frozen designs, there is still value in building a titanium cold-forming capability. For a relatively low implementation cost this capability can greatly expand the possible applications of titanium sheet forming.

A comprehensive, recent paper from Shao, Li, & Zhan discusses many of the advancements, results and challenges associated with industrialization of this technology. Chief amongst these is a need for ultrasonic equipment, including both ultrasonic transducers and generators with intelligent online feedback.

Expertise in ultrasonic-assisted cold forming titanium

I have experience with several ultrasonic manufacturing applications including ultrasonic-assisted extrusion, punching, upsetting, and polymer welding, as well as experience in the Terfenol-D transducer design that was used to provide bulk motion for several of these experiments. The results of this work have been published in several peer-reviewed scholarly articles, culminating in my PhD thesis.

A commonly-stated concern regarding the development of an ultrasonic transducer system is sensitivity to resonance given that a forming system's frequency response will shift throughout the course of a forming process. This concern is alleviated by using a Terfenol-D transducer which can provide effective output levels over a broad range of frequencies. While this design has a higher initial cost than a comparable piezoelectric system, it is also capable of withstanding higher forming forces and is also not susceptible to material degradation over time, making it much better suited to long production runs in high duty cycle applications.

An off-the-shelf Terfenol-D ultrasonic transducer system suitable for applications up to approximately 0.1 inch thickness fits in an envelope roughly the size of a Pringles can, making it easy to retrofit to existing equipment. Custom ultrasonic transducers for other applications can be made by Etrema Products.

Ready to Transform Titanium Forming?

Aerospace, medical and defense innovators: The future of titanium cold forming is within reach. Big W Engineering Solutions invites you to partner in advancing ultrasonic-assisted forming—unlocking dramatic reductions in forming stress, improved plasticity, and superior surface finishes. Let’s move beyond the limitations of hot forming and costly post-processing. Collaborate with us to develop and implement next-generation titanium forming solutions that deliver performance, repeatability, and cost savings.

Join us in shaping the next era of titanium manufacturing. Contact Big W Engineering Solutions or book a free discovery call today to explore partnership opportunities and drive real progress in your industry.