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The article presents a study on the use of Photon Doppler Velocimetry (PVD) in the analysis of electromagnetic metal forming. The study shows how PVD works with a dynamic ring expansion test experiment to the measure the tensile stress-strain relations at high strain rate as well as examine the compaction behavior of powdered materials. It suggests that PVD provide improved estimates of material constitutive behavior as well as experimentally measured data to evaluate numerical models.

Reactive infiltration of precursor ceramics (e.g., the formation of an alumina-aluminum composite by reaction of silica in liquid aluminum) is a low-cost and versatile method of creating materials with interpenetrating co-continuous ceramic and metal phases. By controlling the composition and microstructure of the precursor and the composition of the reaction bath, one can control the structure and properties of the resulting material. This paper summarizes preliminary attempts to use these routes to create next-generation materials for automotive brake rotors. Two types of materials were tested. The first is a two-level composite of a co-continuous alumina-aluminum structure that surrounds SiC particles that provide thermal conductivity. For higher-temperature use, the aluminum alloy is replaced with aluminum-bronze. Both materials show friction and wear properties similar to cast iron, but with half the density and better thermal conductivity. [ABSTRACT FROM AUTHOR]

Abstract: High velocity deformation can be quite effective in increasing the forming limits of metal sheets as well as effectively treating some other common metal forming problems, such as wrinkling and distortion. This study examines the high velocity formability of cold rolled sheet steel as developed in impact with a curved punch. To study forming over large areas, a steel sheet sample was electromagnetically launched, at a shaped punch at velocities of 50–220m/s, using a flat spiral electromagnetic coil and an aluminum driver sheet. Estimates of impact velocity were obtained with the help of a high-speed camera. It was observed that the impact velocity of the samples increased nearly linearly with the energy of launch. The failure strains of all the steels were dramatically increased beyond those obtained in tensile tests as expected from the forming limit diagram. The forming limits of steels with both very low and high quasi-static ductility were similar in high velocity forming. Formability seemed to depend largely on local boundary conditions as dictated by the punch/tool geometry used. The strain distribution obtained depended on the shape of the punch used for impact. Thus it appears that in high velocity impact, the quasi-static ductility of the material is not of primary importance to the material''s formability. At high velocities, high strains to failure can be obtained with steels having very low quasi-static ductilities. Based on these observations, one may be able to develop forming operations that take advantage of this dramatic improvement in formability. This could enable the use of high-strength low-cost materials in a number of complex components. [Copyright &y& Elsevier]

Abstract: Forming, cutting and welding of metal by impulse has significant advantages, in that short time scales change the fundamental nature of the forming process and short duration impulses can enable much lighter and more agile equipment because large static forces do not need to be resisted. Impulse forming is most commonly executed using electromagnetic forming. However, the application of electromagnetic forming is limited at high energies and large numbers of operations by the availability of long-lived electromagnetic coils (or actuators, as they are sometimes referred to). Low-cost, disposable actuators have been suggested as one method to counteract this issue. Here we propose the use of low-cost foils or wires that are intentionally vaporized by a pulsed electric current, in order to create an intense mechanical impulse. Applications including cutting, forming, and dimensional calibration are demonstrated and discussed. The available literature that could provide design guidance is reviewed. A simple cutting and welding experiment using a vaporizing aluminum foil is demonstrated. Further experiments study the expansion of simple copper tubes using the impulse developed from copper and aluminum wires that are vaporized using capacitor bank discharge with nominal charged voltages between 3.4 and 6.7kV, and peak currents between 60 and 150kA delivered with rise times on the order of 20μs. This gives some guidance on how forming operations may be designed and, opens possible areas for further research. [Copyright &y& Elsevier]