Hot Stretch Forming of a Titanium Alloy Component for Aeronautic: Mechanical and Modeling

Abstract

The development of Hot Stretch Forming (HSF) by the Cyril Bath Company was in response to airframe designers needing to use Titanium airframe components in new commercial aircraft. Many of the airframe component structures are designed to fit against the inside radius of the fuselage curvature. By combining traditional stretch forming technology with hot titanium forming techniques, the HSF guarantees a saving in material and machining time, which are two serious cost issues for today’s aircraft manufacturers. In addition, the process allows for consistent quality in a productively efficient manner, assuring the sustainable attainment of delivery and build schedules. The HSF is an innovative process on the cutting edge of the technologies, so focused research is needed in order to better understand this technology and develop new applications for this process. in this paper the HSF process is investigated: the machine and the different steps that characterized the process were described and the results of a preliminary experimental campaign was discussed focusing the attention on the metallurgical aspect. Moreover a modeling of the process was executed in order to study the stresses and strains undergone by the material among the deformation.

An Experimental Study of the Tension-Compression Asymmetry of Extruded Ti-6.5Al-2Zr-1Mo-1V under Quasi-Static Conditions at High Temperature

“…Titanium and its alloys for their high corrosion resistance, excellent mechanical properties and relatively light weight are widely used in aerospace materials [1][2][3][4]. Additionally, unlike aluminum alloys, they have similar thermal expansion coefficients and outstanding electrochemical compatibility with carbon fiber reinforced plastics (CFRP) [5,6]. Titanium alloys are highly desirable for use in contoured airframe structures with complex curvatures, such as the frame and reinforced frames of a cabin door, see in Figure 1 [7].…”

Formability and microstructure evolution mechanisms of Ti6Al4V alloy during a novel hot stamping process

“…However, the forming of complexshaped components from titanium alloys is time, energy and cost intensive. The aircraft industry currently uses methods such as superplastic forming [2], superplastic forming with diffusion bonding [3], hot stretch forming [4], creep forming [5], hot gas-pressure forming [6] or isothermal hot forming [7,8] to produce complex-shaped components. However, these techniques usually require a very high temperature, slow strain rate and simultaneous heating of tools and sheet during the process.…”

Hot stretch forming of titanium sheet by resistance heating

“…[1] These components are typical extrude shape, which used to be made with aluminum and be formed by stretching at room temperature. [2] But titanium alloys are difficult to form due to their poor formability and large springback at room temperature. In order to improve the formability and decrease the springback, hot forming is used to form the titanium panels of aircraft.…”

“…Because bulkheads are usually slender members with curvature and forming quality of these components directly affects the assembly precision, the aerodynamic shape and the service life of aircraft, bulkheads with high quality need to be obtained. [5] Fig.1 Process procedure of electrically assisted hot stretch forming [2] A.Astarita et al studied metallurgical aspect of hot stretch forming by microstructure experiment and the stress and strains by establishing a finite element model of Ti-6Al-4 extrusion in DEFORM. [2] The residual stresses after stretch bending and creep forming period were predicted.…”

“…[5] Fig.1 Process procedure of electrically assisted hot stretch forming [2] A.Astarita et al studied metallurgical aspect of hot stretch forming by microstructure experiment and the stress and strains by establishing a finite element model of Ti-6Al-4 extrusion in DEFORM. [2] The residual stresses after stretch bending and creep forming period were predicted. A lower stress distribution was in the middle of the extrusion while a contrary trend occurred on the side because of the effect of the clamps.…”