Papers by Keyword: Blow Forming

Abstract: Superplastic forming has been known for the ideal process for manufacturing complex parts. Also, diffusion bonding can give a higher design flexibility, which allows a better performance with a lower overall manufacturing cost. Fine grained INCONEL 718 alloy sheet has been known to show superplastic behavior with the combination of high strength and corrosion resistance at the elevated temperatures. In the present study, high temperature deformation characteristic of INCONEL 718 sheet with 15m was investigated firstly. Then, blow forming process with cylindrical cavity was tried. Also, best diffusion brazing and bonding condition was tried to be defined in terms of temperature, pressure and time. Bonding strength was characterized by using lap shear type test and interface observation. Characteristics of deformation and diffusion bonding at high temperature were influenced greatly with grain size while Nb precipitate also played an important role.

Abstract: It is known that the stiffened cylinder structure supports external pressure loads inaerospace and marine application subjected to hydrostatic pressure. For relatively low temperature,aluminum or composite cylinder can be appropriate, but at higher temperature, titanium or steel alloymust be considered. Nickel based alloys show excellent corrosion resistance and elevated temperaturemechanical strength so that these alloys are now successfully utilized for aerospace and engineapplication. This paper provides innovative

Abstract: Blow forming technology has been used to produce glass and plastic components with easy and simple process. In order to apply this technology to metallic system, relatively high formability of material and elevated temperature are required. Since the blow forming temperature is quite high for metallic system, the main difficulty is to obtain adequate mold material which can sustain pressure difference between inside and outside of the tool. The present study demonstrates blow forming process with IN718 and steel can be applied to manufacturing of combustion chamber in liquid propellant rocket engine with complex shape. The result shows that the developed technology to process design of high temperature blow forming by the finite element method can be applied for near net shape forming of a combustion chamber of liquid rocket engine and a cone-shaped chamber extension part with cooling channels.

Abstract: Blow forming accompanied with superplasticity makes possible the forming of complex parts, which cannot be formed by cold press forming. The conventional superplastic AA5083 alloy ‘ALNOVI-1’ developed by the Furukawa-Sky Aluminum Corp. shows high superplasticity because of its fine grain and is widely used for blow forming. However, for mass production of components, an Al-Mg alloy with finer-sized grains is needed. In this research, the newly developed high Mn version of the Al-Mg alloy ‘ALNOVI-U’ is used, and this material possesses grains finer than those of the conventional AA5083 alloy. The effects of finer grain size on the blow formability at high strain rates over 10^-2/s and the properties of the resulting moldings were studied.

Abstract: Blow forming process of plastic sheets is simple and easy to realize, thus, it is widely used for plastic thin-wall parts. In the practical production, an effective method is needed for the preliminary set-up of process parameters in order to achieve accurate control of thickness distribution. Thus, a finite element method (FEM) code is used to simulate blow forming process. For better description of complex material theological characteristics, a physically based viscoelastic model (VUMAT forms Buckley model) to model the complex constitutive behavior is used. Nonlinear FE analyses using ABAQUS were carried out to simulate the blow forming process of plastic cups. The actual values at different locations show a satisfactory agreement with the simulation results: as a matter of fact the error along the cell mid-section did not exceed 0.02 mm on average, corresponding to 5% of the initial thickness, thus the FE model this paper can meet the requirements of the engineering practice.

Abstract: The objective of this study is to fabricate lightweight structural panels and pressurized tanks by blow forming of solid-state bonded Ti-6Al-4V sheets. The solid-state bonding process was conducted in selective areas of the sheets and gas pressure was applied to the core sheet in order to form center cells. The microstructure of bonded region shows no indication of any discontinuous or heterogeneous microstructure at interface. It is shown that the blow forming of a lightweight sandwich structural panel and a sphere vessel was successfully performed with solid-state bonded multiple sheets of titanium alloy. The result of configuration and thickness distribution measurement indicate that the FEM analysis can predict the forming behavior during blow forming process of solid-state bonded sheets.

Abstract: Titanium alloys have been widely used in aeronautics and aerospace industries due to their high strength, good corrosion resistance and low density. Since many aerospace vehicle systems require high performance lightweight pressurized vessel for storage of propellant, nitrogen, oxygen, or other medium, the titanium alloy is one of the excellent candidates for this purpose. Conventionally spin forming and TIG welding process have been applied to manufacture titanium spherical vessel. In this work, an innovational method of blow forming and solid state bonding technology has been developed to save manufacturing cost and reduce weight of titanium vessel. High temperature behavior of titanium alloy was characterized and according to this result, solid state bonding process was established with demonstration of manufacturing spherical and hollow cylinder pressure vessel. The optimum condition for solid state bonding of this alloy was obtained by applying hydrostatic pressure of 4MPa at 1148K for 1 hour. For blow forming, the pressure profile was developed using MARC software and the maximum pressure of 30MPa was applied. The structural integrity of the vessel was demonstrated by performing a hydraulic pressurization test.

Abstract: Superplastic forming characteristics of AZ31 Mg alloy recycled by solid-state process were investigated. Cylindrical scraps and machined chips were recycled by hot extrusion and hot rolling in air. As a result of tensile test, elongation to failure of the specimens recycled from small and large cylindrical scraps was almost the same as that of the rolled specimen from a virgin ingot. On the other hand, the specimen from machined chips had much lower elongation at elevated temperatures. The oxygen concentration of the specimen recycled from machined chips showed about 60 times higher value compared with that of the other specimens. In superplastic forming tests, the specimen from small and large cylindrical scraps exhibited excellent formability similar to the rolled specimen from a virgin ingot. However, the specimen from machined chips showed poor formability. Thus, oxide contamination adversely affected the formability of recycled Mg alloy.

Abstract: Blow forming characteristics of 5083 Al alloy and AZ31 Mg alloy recycled by solid state recycling were investigated. Scraps with different volume were recycled by hot extrusion and hot rolling in air. Oxide layers, which were contaminants from scrap surface, were distributed parallel to the extrusion direction in the recycled specimens. In the blow-forming test, the specimen from smaller scraps exhibited lower formability. The oxygen concentration in the recycled specimens was approximately proportional to the total surface area of scraps in the recycled specimen per unit volume. The low formability of the recycled specimens is likely to be attributed to contamination level of oxide.