Method for metal working using high pressure fluid pulses

Abstract

Methods and apparatus employing an ultra high-pressure fluid pulse to perform metal working operations, including joining and cold working. In one application, an ultra high-pressure fluid pulse is directed into a hollow rivet that is seated within an orifice formed in two metal sheets, causing the fastener to expand outwardly, in an interference fit with the orifice that joins the metal sheets together. The ultra high-pressure fluid pulse can alternatively be applied to the metal sheets to plastically deform them into a cavity to form a clinch fastener joint. Further, the ultra high-pressure fluid pulse is usable to plastically deform the interface between stacked metal sheets or other components into surface features that are provided on one of the sheets, to form a mechanical interlock. Metal or ceramic powders placed between the metal sheets can be used to cause melting of the surfaces of the sheets at their interface upon the application of an ultra high-pressure fluid pulse, thus welding the sheets together with a tack weld. An ultra high-pressure fluid pulse can also be used to cold work an orifice in a metal component, thereby increasing the fatigue life around the orifice by introducing a residual compressive stress in a thin surface layer of the metal. An ultra high-pressure fluid pulse generator includes a fast acting valve that opens to enable an ultra high-pressure pulse to pass through a nozzle. A tapered fluid channel in the nozzle can substantially accelerate the ultra high-pressure fluid pulse.