Incremental Sheet Hydro-Forming (ISHF) is a hybrid process of Incremental Sheet Forming (ISF) and Sheet Hydro-Forming (SHF). In the ISHF process, a single ball tool moves over one side of the surface of the sheet and hydraulic support is provided in another by using the pressurized hydraulic fluid. In the current research, an attempt has been made to achieve high forming angles using ISHF. The forming strategy, multi-stage & multi-step (MSMS), has been proposed to improve the formability in ISHF. The MSMS has resulted in the improvement in the formability and forming angle achieved is
. The primary issue, identified in MSMS forming strategy, is the failure of the product due to thinning of the sheet. To address the failure of the sheet due to thinning, a modified version of MSMS was proposed. This modified version of MSMS has shown tremendous improvement in the formability of the ISHF. The forming angle upto
has been successfully achieved using the modified version of MSMS. Analytical models have been developed for MSMS forming strategy and for the modified version of MSMS forming strategy. The experimental results are closely the same as predicted by analytical models.
Multistage depressed collectors (MDCs) play a vital role in efficiency enhancement of traveling-wave tubes for various strategic and communication applications. Design of a highly efficient MDC is no longer a tough challenge due to the availability of large number of efficient numerical simulation tools. However, still an established technique for the development of such MDCs to address their thermal as well as high-voltage breakdown issues has not been published. In this paper, we have exercised different development techniques in the light of specified meritorious aspects with respect to actual dimensional accuracies, thermal dissipation, and high-voltage withstanding capability. We have made use of an analytical method to estimate the proper braze alloy quantity and holding time during brazing operation to ensure optimum brazing, thereby, yielding minimum thermal impedance and improved high-voltage breakdown strength.Index Terms-Analytical model, brazing quality, high-voltage breakdown, multistage depressed collectors (MDCs), thermal dissipation, traveling-wave tube (TWT).
Incremental sheet forming (ISF) process is a flexible manufacturing process to produce complex 3D products at reasonable manufacturing cost. In addition to a single point, incremental sheet forming pressure has been applied to the back side of sheet surface in order to provide support to the sheet surface and improve process efficiency. In the current work, a comparative analysis of ISF & pressure assisted ISF process through CAE simulation have been done to predict the forming forces, energy requirements, effective stresses, etc. The forming forces in ISF as well as pressure-assisted ISF is very low when as compared to forming forces in traditional forming processes. The pressure-induced ductility hasresulted in the reduction of forming forces with pressure assisted ISF. The energy required in pressure assisted ISF is slightly higher than the ISF process. An increment in effective stresses is observed in pressure assisted ISF, which is a due application of force on both sides of the sheet. However, these stresses are local and very small when as compared to traditional forming processes.
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