Method of and apparatus for water-jet peening

• US 5,305,361 A
• Filed: 01/25/1993
• Issued: 04/19/1994
• Est. Priority Date: 01/24/1992
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Mochizuki, Masahito, Kurosawa, Koichi, Uraki, Keiichi, Enomoto, Kunio, Saito, Hideyo, Otaka, Masahiro, Tamai, Yasumasa, Tsujimura, Hiroshi
• Primary Examiner(s): Wasil, Daniel D.
• Application Number:
  US08/008,718
• Time in Patent Office: 449 Days
• Field of Search: 376/316, 376/310, 376/305, 376/277, 376/249, 239/4, 239/102.2, 134/1, 134/34, 134/22.12, 134/167 R, 299/17
• US Class Current: 376/316
• CPC Class Codes: B05B 15/62 Arrangements for supporting spraying apparatus, e.g. suction cups
• CPC Class Codes: B05B 17/0615 spray being produced at the free surface of the liquid or other fluent material in a container and subjected to the vibrations
• CPC Class Codes: C21D 7/06 by shot-peening or the like
• CPC Class Codes: G21C 19/00 Arrangements for treating, for handling, or for facilitating the handling of, fuel or other materials which are used within the reactor, e.g. within its pressure vessel
• CPC Class Codes: Y02E 30/30 Nuclear fission reactors

Abstract

A water jet peening method in which a pressurized water jet flow containing cavities is jetted through a nozzle having a velocity increasing orifice portion and a horn-like jetting hole formed continuously with the velocity increasing orifice portion to impinge against a surface of a metallic material immersed in water and to cause the cavities to collapse at the surface of the metallic member, and a tensile plastic deformation is caused in a surface layer of the metallic material by a local high pressure generated by the impingement and the collapse so that a residual tensile stress in the surface of the metallic member is reduced. In this method, the nozzle is vibrated so that vibration-induced cavities are formed in the vicinity of a nozzle wall surface, and the vibration-induced cavities are caused to impinge against the surface of the metallic member by the pressurized water jet flow containing cavities. It is thereby possible to promote the generation of cavities even in a case where pure water existing in a nuclear reactor and scant of nuclei from which cavities will be generated is used in peening of an internal structual member of the reactor.

Claims

1. A water jet peening method including the steps of:

forming a water jet flow of a predetermined velocity containing cavities through a nozzle having a velocity increasing orifice portion and a horn-like jetting hole formed continuously with said velocity increasing orifice portion;

vibrating said nozzle by applying a vibration to said nozzle so that vibration induced cavities are formed in a vicinity of a nozzle wall surface;

impinging said water jet flow against a surface of a metallic material immersed in water;

causing said vibration-induced cavities to impinge against the surface of said metallic member by said pressurized water jet flow containing cavities; and

causing said cavities to collapse at the surface of said metallic member wherein there is caused a tensile plastic deformation in a surface layer of said metallic material by a local cavity collapsing pressure so that a residual tensile stress in the surface of said metallic member is reduced.

2. A water jet peening method according to claim 1, wherein said nozzle is vibrated in one of a direction along the water jet flow and a direction perpendicular to the water jet flow.

12. A water jet peening method according to claim 1, wherein said nozzle is vibrated in one of a direction along a water jet flow and a direction perpendicular to said water jet flow.

3. A water jet peening apparatus for peening a metallic material placed on a mount base in a water tank by water jetting, said apparatus comprising:

pressurized fluid generation means for generating a pressurized fluid;

pressurized fluid supply means for supplying said pressurized fluid to a nozzle;

said nozzle connected to said pressurized fluid generating means and said pressurized fluid supply means, said nozzle for providing said pressurized fluid as a water jet;

a peening gun having a vibrator for vibrating said nozzle;

a three dimensional traveling means for making said peening gun travel three-dimensionally;

high-pressure fluid control means for controlling a pressure and a flow rate of said pressurized fluid;

vibrator control means for generating a frequency signal for operating said vibrator and for controlling a frequency, waveform and amplitude of said vibrator; and

peening gun control means for three-dimensionally controlling said peening gun to control a distance, direction and velocity of said nozzle with respect to said metallic material.

4. A water jet peening apparatus according to claim 3, wherein said nozzle is attached to said peening gun through one of a vibrator for causing longitudinal vibration and a vibrator for causing lateral vibration, said nozzle having a velocity increasing orifice portion and a horn-like jetting hole formed continuously with said velocity increasing orifice portion, said nozzle for use in water.

5. A water jet peening apparatus comprising:

a pressure pump for generating a pressurized fluid;

a pressurized hose for supplying said pressurized fluid to a nozzle;

a water jet control panel for controlling said pressure pump and a pressure and flow rate of said pressurized fluid;

a vibrator control panel having a frequency- and waveform-variable frequency oscillator and an amplifier, for controlling a frequency, waveform and amplitude of a vibrator;

a peening arm having at one end a coupler for engagement with a vibrating mechanism and being engaged at said one end with said pressurized hose, and having at another end a peening gun having said nozzle;

a three-axis drive table for making said peening arm travel three-dimensionally;

a water tank having a mount table on which a metallic member is mounted; and

a general controller for controlling a distance between said nozzle and a surface of said metallic member, and a direction and velocity of three-dimensional traveling of said nozzle.

6. A water jet peening apparatus according to claim 5, wherein said nozzle is attached to said peening gun through one of a vibrator for causing longitudinal vibration and a vibrator for causing lateral vibration, said nozzle having a velocity increasing orifice portion and a horn-like jetting hole formed continuously with said velocity increasing orifice portion, said nozzle for use in water.

7. A water jet peening apparatus according to claim 5, wherein said peening arm comprises a flexing peening arm having a joint such as to be able to flex through a selected angle at an intermediate position on a pressurized flexible hose engagement portion, and said apparatus further comprises a peening control panel having a function of controlling a flexing angle of said peening arm and angular velocity of said flexing angle.

8. A water jet peening apparatus for peening an internal structural member of a nuclear reactor, comprising:

a swivel carriage placed on an upper surface of a flange of a pressure vessel of said nuclear reactor having a core evacuated by removing an upper cover of said pressure vessel and by successively dismounting a steam drier, a steam separator and fuel channels, said swivel carriage being radially movable on said pressure vessel;

a radially-movable carriage mounted on an upper surface of said swivel carriage, said radially-movable carriage being radially movable on said pressure vessel;

a mast suspended from said radially-movable carriage, formed of a plurality of sections and extendible in a vertical direction; and

a flexible peening arm attached to a lowermost section of said mast through a coupler;

wherein a pressurized water jet flow of reactor core water ejected from a pressurized vibration nozzle of said peening arm is jetted to a surface of said internal structural member to reduce residual tensile stress therein.

9. A water jet peening apparatus according to claim 8, wherein each peening arm of a plurality of said peening arms is provided with a peening gun having a guide roller, said peening guns being attached to a lowermost end of said mast through a coupler so as to be able to open and close like an umbrella.

10. A water jet peening apparatus according to claim 8, wherein said nozzle is attached to said peening gun through one of a vibrator for causing longitudinal vibration and a vibrator for causing lateral vibration, said nozzle having a velocity increasing orifice portion and a horn-like jetting hole formed continuously with said velocity increasing orifice portion, said nozzle for use in water.

11. A water jet peening method of using tensile plastic deformation to reduce residual tensile stress in a surface layer of a metal, said method including the steps of:

forming a pressurized water jet flow through a nozzle having a velocity increasing orifice portion and a horn-like jetting hole formed continuously with said velocity increasing orifice portion, and impinging said water jet flow against a surface of a metallic material immersed in water;

vibrating said nozzle by applying frequency vibration to said nozzle so that vibration-induced cavities are formed in a vicinity of a nozzle wall surface; and

directing said vibration-induced cavities ti impinge against said surface of said metallic member by said pressurized water jet flow containing cavities, and causing the cavities to collapse at the surface of said metallic member to induce a tensile plastic deformation in a surface layer of said metallic material by a local cavity collapsing pressure generated so that a residual tensile stress in a surface of said metallic member is reduced.