Repetitive pressure-pulse apparatus and method for cavitation damage research

Abstract

An apparatus for inducing cavitation at a surface of a specimen includes a cavitation chamber, a window extending through the wall of the chamber to an area outside the chamber, a test specimen positioned within the chamber, and a cavitation media inside the chamber and in contact with the surface of the specimen. A laser light source is disposed outside the chamber, and is operable to provide a laser beam through the window and into the cavitation media. The laser light source generates a shock wave in the cavitation media, the shock wave causing cavitation at the surface of the specimen.

1 . An apparatus for inducing cavitation at a surface of a specimen comprising:
 a body having a wall defining an internal chamber, said wall defining a window extending through said wall from said internal chamber to an area outside said body;   a specimen holder for positioning the specimen within said internal chamber so that the surface of the specimen is facing said internal chamber;   cavitation media inside said internal chamber and in contact with the surface of the specimen; and   a laser light source disposed in said area outside said body, said laser light source operable to provide a laser beam through said window and into said cavitation media.   
     
     
         2 . The apparatus as recited in  claim 1 , wherein said laser light source generates a short duration laser pulse that enters said internal chamber through said window and generates a shock wave in said cavitation media, said shock wave causing cavitation at the surface of the specimen. 
     
     
         3 . The apparatus as recited in  claim 1 , wherein said wall that defines said internal chamber includes an interior surface that is concave elliptical shaped. 
     
     
         4 . The apparatus as recited in  claim 3 , wherein said wall that defines said internal chamber includes an interior surface that is concave spherical shaped. 
     
     
         5 . The apparatus as recited in  claim 1 , wherein said cavitation media is deionized water. 
     
     
         6 . The apparatus as recited in  claim 1  wherein said wall defining said chamber includes a top and a bottom opposite said top, said window defined in said top, said specimen positioned on said bottom, said window focusing said laser light source at a position within said chamber between said window and said test specimen. 
     
     
         7 . The apparatus as recited in  claim 1  including wave collector positioned within said internal chamber, said wave collector defining a secondary internal chamber, said test specimen positioned within said secondary internal chamber. 
     
     
         8 . The apparatus as recited in  claim 7  wherein said wave collector defines a wave collector window extending between said internal chamber and said secondary internal chamber, said wave collector window generally aligned with said window in said wall defining said internal chamber to enable said laser beam to pass through said window and said wave collector window. 
     
     
         9 . The apparatus as recited in  claim 8  wherein said secondary chamber includes a surface that is concave elliptical shaped. 
     
     
         10 . The apparatus as recited in  claim 8  wherein said secondary chamber includes a surface that is concave spherical shaped. 
     
     
         11 . The apparatus as recited in  claim 8  wherein said wall defining said chamber includes a top, a bottom opposite said top, and a sidewall extending between said top and said bottom, said window defined in said top, said wave collector extending into said chamber from said sidewall. 
     
     
         12 . A method for generating cavitation, comprising:
 providing a cavitation media;   providing a test specimen proximate said cavitation media; and   directing a laser beam into said cavitation media to initiate laser optical breakdown in said cavitation media, producing a shock wave propagating through said media and creating cavitation damage on a surface of said test specimen.   
     
     
         13 . The method of  claim 12  wherein said laser is a pulsed laser. 
     
     
         14 . The method of  claim 13  wherein said laser has a wavelength within a broad spectrum from the visible to the near infrared and pulse lengths varying from nanosecond to millisecond ranges. 
     
     
         15 . The method of  claim 14  wherein said cavitation media is deionized water. 
     
     
         16 . The method of  claim 12  wherein said cavitation media is held in a cavitation chamber, said cavitation chamber including a window extending between said cavitation chamber and an area outside said chamber, wherein a laser light source is provided outside of said chamber, and said laser light source is operated to direct said laser beam through said window and into said chamber. 
     
     
         17 . The method of  claim 16  wherein said window is a quartz window, said window focusing said laser beam at a predetermined position within said chamber. 
     
     
         18 . The method of  claim 16  including providing a wave collector within said cavitation chamber, said wave collector defining a secondary chamber having an interior surface with a predetermined shape, said wave collector defining at least one opening extending into said secondary chamber, said at least one opening aligned with said window, said test specimen positioned within said secondary chamber. 
     
     
         19 . The method of  claim 16  including measuring at least of the surface temperature of said test specimen, the temperature of said cavitation media, and the pressure within said cavitation chamber as said laser beam is directed into said cavitation chamber. 
     
     
         20 . An apparatus for generating cavitation, comprising:
 a cavitation unit including a wall defining an interior chamber, said cavitation unit including a fluid flow inlet and a fluid flow outlet enabling fluid flow through said interior chamber;   a window extending through said wall;   a cavitation media within said interior chamber, said cavitation media in fluid communication with said fluid flow inlet and said fluid flow outlet such that said cavitation media can be circulated through said interior chamber through said inlet and said outlet;   a test specimen positioned within said interior chamber; and   a laser light source positioned outside of said interior chamber to direct a laser beam through said window and into said interior chamber; said window capable of focusing said laser at a location between said window and said test specimen.