Title of Invention

A METHOD AND APPARATUS FOR CARRYING OUT OIL JET PEENING

Abstract

A METHOD AND APPARATUS FOR CARRYING OUT OIL JET PEENING An apparatus for carrying out oil jet peening comprising a tank for the oil to be used for peening; a high pressure pump, a pressure relief valve, bypass needle valve, pressure gauge and check valve; an electric motor coupled to the pump, the inlet port of the pump being connected to a filter and the pressurised oil emerging from the pump being distributed to the check valve and pressure relief valve, the check valve stopping the return flow of pressurised oil to the pump, the outlet port of the check valve being connected to the nozzle of the peening unit.

Full Text

This invention relates to a method and apparatus for carrying out oil jet peening. Many machine components experience fatigue loading in service and mostly Ml due to fatigue related mechanisms. It has long been recognized that the introduction of carefully controlled compressive residual stress field is one potential means of increasing resistance to fatigue. Beneficial compressive residual stress field can be induced by shot peening. laser shock peening, and ultrasonic peening. The net improvement of fatigue life associated with shot peening is decreased due to the surface irregularities caused by the shots. In addition controlling the process parameters tor the best effect is difficult in the shot peening operation. This invention relates to a novel method of surface peening by a high pressure oil jet for the introduction of compressive residual stresses. The proposed oil jet peening has the advanatges over other peening processes, namely, of reduced erosion and better surface finish. Also better accessibility to remote areas of the peening surface as compared to shot peening is a further advantage of this invention. The method of surface peening according to this invention comprises the impingement of a high pressure oil jet on the part of the surface of the workpiece to be peened, such that the oil droplets in the jet generate a pressure distribution producing high impact pressures causing local plastic deformation at the spot of impact, thus producing compressive residual stress at the surface, and the nozzle in a linear direction at a predetermined oil pressure and jet velocity across the surface to be peened. The apparatus for carrying out the method, according to this invention, comprises a tank for the oil to be used for peening; a high pressure pump, a pressure relief valve, bypass needle valve, pressure gauge and check valve; an electric motor coupled to the pump, the inlet port of the pump being connected to a filter and the pressurised oil emerging from the pump being distributed to the check valve and pressure relief valve, the check valve stopping the return flow of pressurised oil to the pump, the outlet port of the check valve being connected to the nozzle of the peening unit. This invention will now be described with reference to the single Figure in the accompanying drawings which illustrate, by way of example, and not by way of limitation, one of possible embodiments of the apparatus proposed herein. The embodiment aforesaid will be seen to comprise a tank T for containing the oil O to be used for the peening operation. A high pressure pump, such as, a radial piston pump R, a pressure relief valve P, bypass needle valve B, pressure gauge G and check valve C are also provided. The pressure relief valve P relieves the system of any excessive pressure of the oil in the lines. The bypass needle valve B controls the flow rate of oil. The pump is driven by an electric motor. The inlet port I of the pump is connected to a filter Fl provided for the oil tank T for filtering the oil O drawn by the pump and the pressurised oil emerging at the outlet port £ of the pump being distributed to the check valve C and pressure relief valve P, the check valve stopping the return flow of pressurised oil to the pump, the outlet port of the check valve being connected to the nozzle N of the peening unit The pressure relief valve P controls the oil pressure in the hydraulic system while the pressure gauge G indicates the pressure in the said system. The nozzle N can be moved at differernt velocities which can be precisely controlled using a personal computer. The work table on which the work piece W is placed can be moved in steps of a minimum 0.025mm. The tray T below the work piece W collects the spent oil which is taken back to the tank T thrc ugh a filter F2. The jet of oil emerging from the nozzle N is indicated by J. The total system is covered to prevent dust particles entering into the peening zone. No erosion cavities were observed in the high yield strength AA6063-T6 alloy. The developed oil jet peening is capable of producing 100%coverage in single pass. Oil jet pening process induces compressive residual stress and sub surface work hardening without much change the surface topography. The size of indents formed is lower than that formed in conventional shot peening process. The process seems to be promising alternative tor other peening processes with reduced erosion and a better surface finish. The terms and expressions herein are of description and not of limitation, since various other embodimnts of this invention are possible without departing from the scope and ambit thereof.

Documents:

779-che-2006-claims.pdf

779-che-2006-correspondence-others.pdf

779-che-2006-description-complete.pdf

779-che-2006-drawings.pdf

779-che-2006-form 1.pdf

779-che-2006-form 26.pdf