Papers by Keyword: SPF/DB

Abstract: This study proposes a novel method of manufacturing composite vibration-damping steel sheet with Zn-22Al superplastic alloy using friction stir forming (FSF). Trials of mechanical interlocking of steel sheet with Zn-22Al superplastic alloy using FSF were carried out on a modified milling machine. The results are discussed in terms of residual microstructures and mechanical properties. We concluded that cladding steel sheet with Zn-22Al superplastic alloy using FSF results in superplastic forming and diffusion bonding.

Abstract: Titanium is difficult to fabricate into complex aircraft configurations. There is several elevated temperature forming techniques that are available to produce titanium components for aircraft, two of which will be discussed here: Superplastic Forming (SPF) and hot forming. SPF is used when complex shapes are required, for example, tight radii, and uses a tool that contains the required configuration and seals around the periphery so inert gas pressure can be used to form the material. Since SPF is a process where the material is stretched, the part is not a uniform thickness when completed. A variation of the process combines SPF with diffusion bonding (SPF/DB) of two or more pieces of titanium together to produce integrally stiffened structure containing very few fasteners. The hot forming process uses matched metal tools, offset by the thickness of the starting material, are used to form the part contour at elevated temperature. The required part geometry usually contains no sharp features that have to be formed. Since the material is free to move as the die is closed, the part is fairly uniform in thickness when completed.

Abstract: In the past, engine aft fairing heat shields have typically been titanium castings. With a current single aisle airplane, these components were converted to sheet metal titanium 6Al-4V details fabricated by hot forming or Superplastic Forming (SPF). This conversion saved approximately 20% in both cost and weight per airplane. When heat shields for a twin aisle airplane were being developed, the engineers were interested in a sheet metal version of their heat shields hoping to achieve similar savings. However, the twin aisle configuration was different from the single aisle and did not allow the details to be simple pieces of formed sheet metal. Instead, these twin aisle heat shields are assemblies of details containing SPF components as well as Superplastically Formed and Diffusion Bonded (SPF/DB) panels. Some of the heat shield components are fabricated using the world's first applications of fine grain 6Al-4V titanium, which was developed to SPF at 775°C, covered by a U.S. patent [1], instead of 900°C, which is used for standard grain material. The SPF/DB technology being used contains innovative process developments that are covered by several patent applications [2-4]. The twin aisle heat shield assemblies were estimated to save approximately 15% in both cost and weight per airplane. Actual weight measurements of the first assembly showed an additional 5% savings over the calculated weight per engine resulting in a total weight savings of approximately 20% per airplane compared to titanium castings.