Method and apparatus for peening with liquid propelled shot

Abstract

Systems and methods for generating beneficial residual stresses in a material by impacting the surface of the material with particles that are softer than the material to be peened (“target material”). Shock waves emanate through the target material from the soft particle impacts to generate residual stresses without significantly deforming the surface of the target material. A high pressure liquid is accelerated through a peening nozzle to generate a high-speed liquid jet that is used to accelerate the soft particles that impact the surface of the target material.

What is claimed is: 
     
         1 . A peening system for increasing residual stresses in a target material, the peening system comprising:
 a liquid pump configured for pressurizing a liquid;   a solid particles storage container configured for storing a quantity of solid particles;   a peening head comprising:
 a liquid input port couplable with the liquid pump configured for receiving the pressurized liquid from the liquid pump; 
 a solid particles input port couplable with the solid particles storage container configured for receiving the solid particles from the solid particle storage container; 
 a liquid nozzle coupled to the liquid input port and configured for accelerating the pressurized liquid into a high velocity liquid jet; 
 a mixing chamber coupled to the liquid nozzle and the solid particles input port, such that the solid particles are combined with the high velocity liquid jet and accelerated thereby in the mixing chamber; and 
 an output nozzle coupled to the mixing chamber configured to accelerate the velocity of the liquid jet and solid particles mixture to permit the solid particles to impact a surface of the target material disposed at a stand-off distance from the output nozzle. 
   
     
     
         2 . The peening system of  claim 1 , wherein the liquid is housed in the liquid pump and comprises liquid water. 
     
     
         3 . The peening system of  claim 1 , wherein the liquid is housed in the liquid pump and comprises a cryogenic liquid. 
     
     
         4 . The peening system of  claim 1 , further comprising a robotic manipulator coupled to at least one of the peening head and the target material configured to selectively provide relative motion between the peening head and the target material in order to impart solid particle impacts over a desired area of the surface of the target material. 
     
     
         5 . The peening system of  claim 4 , further comprising a computer control unit operative to selectively control the movement of the robotic manipulator according to pre-programmed instructions. 
     
     
         6 . The peening system of  claim 1 , wherein the solid particles have a hardness that is less than the hardness of the target material. 
     
     
         7 . The peening system of  claim 1 , wherein the solid particles have a hardness equal to or less than 75% of the hardness of the target material. 
     
     
         8 . The peening system of  claim 1 , wherein the solid particles are made from a polymer material 
     
     
         9 . The peening system of  claim 8 , wherein the solid particles are made from rubber, acrylic, Viton®, or polyethylene. 
     
     
         10 . The peening system of  claim 1 , wherein the solid particles are made from brass, copper, lead, or aluminum. 
     
     
         11 . The peening system of  claim 1 , wherein the solid particles are made from an organic material. 
     
     
         12 . The peening system of  claim 11 , wherein the solid particles are made from corn husks or nut shells. 
     
     
         13 . The peening system of  claim 1 , wherein the mixing chamber is configured to draw the solid particles from the solid particles storage container into the mixing chamber by a vacuum created by the high velocity liquid jet passing therethrough. 
     
     
         14 . The peening system of  claim 1 , wherein the solid particles are accelerated by the high velocity liquid jet such that the solid particles impact the surface of the target material with a sufficient velocity to generate residual stress in the target material. 
     
     
         15 . The peening system of  claim 1 , further comprising a first conduit operative to couple the liquid pump with the liquid input port of the peening head and a second conduit operative to couple the solid particles storage container with the solid particles input port of the peening head. 
     
     
         16 . The peening system of  claim 1 , wherein the solid particles have a largest dimension that is between 0.025 mm and 1 mm. 
     
     
         17 . The peening system of  claim 1 , further comprising a control valve coupled to the solid particles storage container operative to regulate the mass flow rate of the solid particles flowing from the solid particles storage container to the solid particles input port. 
     
     
         18 . The peening system of  claim 17 , further comprising a computer control unit operatively coupled to the control valve configured to selectively control the operation of the control valve. 
     
     
         19 . The peening system of  claim 1 , wherein the liquid pump is configured to pressurize the liquid to a pressure greater than 10,000 pounds per square inch (PSI). 
     
     
         20 . The peening system of  claim 1 , further comprising a robotic manipulator coupled to at least one of the peening head and the target material configured to selectively provide relative motion between the peening head and the target material in order to impart solid particle impacts over a desired area of the surface of the target material, wherein the robotic manipulator is configured to maintain the stand-off distance between ⅛ of an inch and 15 inches. 
     
     
         21 . The peening system of  claim 1 , wherein the solid particles are accelerated such that the solid particles impact the surface of the target material at a velocity of at least 300 meters per second. 
     
     
         22 . A peening system for increasing residual stresses in a target material, the peening system comprising:
 a liquid pump configured for pressurizing a liquid to a pressure of at least 10,000 pounds per square inch (PSI);   a solid particles storage container configured for storing a quantity of solid particles having a hardness of no more than 75% of the hardness of the target material;   a peening head comprising:
 a liquid input port couplable with the liquid pump configured for receiving the liquid from the liquid pump; 
 a solid particles input port couplable with the solid particles storage container configured for receiving the solid particles from the solid particle storage container; 
 a liquid nozzle coupled to the liquid input port and configured for accelerating the liquid into a high velocity liquid jet; 
 a mixing chamber coupled to the liquid nozzle and the solid particles input port such that the solid particles are combined with the high velocity liquid jet and accelerated thereby in the mixing chamber, the mixing chamber being configured to draw the solid particles into the mixing chamber by a vacuum created by the high velocity liquid jet passing therethrough; and 
 an output nozzle coupled to the mixing chamber configured to accelerate the velocity of the liquid and the soft particles to permit the solid particles to impact a surface of the target material disposed at a stand-off distance from the output nozzle. 
   
     
     
         23 . A method of peening a target material to increase beneficial residual stresses therein, the method comprising:
 providing a quantity of solid particles;   pressurizing a liquid;   forming a high velocity liquid jet from the pressurized liquid; and   accelerating the solid particles using the high velocity liquid jet such that the solid particles impact a surface of the target material to increase beneficial residual stresses therein.   
     
     
         24 . The method of  claim 23 , where the liquid comprises liquid water. 
     
     
         25 . The method of  claim 23 , where the liquid comprises a cryogenic liquid. 
     
     
         26 . The method of  claim 23 , wherein the solid particles are accelerated within a peening head, the method further comprising selectively moving at least one of the peening head and the target material relative to each other to impart solid particle impacts over a desired area of the surface of the target material. 
     
     
         27 . The method of  claim 26 , wherein the selectively moving is performed by a programmable robotic manipulator. 
     
     
         28 . The method of  claim 23 , wherein the solid particles have a hardness equal to or less than 75% of the hardness of the target material. 
     
     
         29 . The method of  claim 23 , wherein the solid particles are made from a polymer material, metal material, or organic material. 
     
     
         30 . The method of  claim 23 , wherein accelerating the solid particles comprises drawing the solid particles into a mixing chamber by a vacuum created by the high velocity liquid jet passing therethrough. 
     
     
         31 . The method of  claim 23 , wherein the solid particles have a largest dimension that is between 0.025 mm and 12 mm. 
     
     
         32 . The method of  claim 23 , further comprising selectively regulating a mass flow rate of the solid particles prior to being accelerated by the high velocity liquid jet. 
     
     
         33 . The method of  claim 23 , wherein pressurizing the liquid comprises raising the pressure of the liquid to a pressure greater than 10,000 pounds per square inch (PSI). 
     
     
         34 . The method of  claim 23 , wherein accelerating the solid particles comprises accelerating the solid particles to a velocity of at least 300 meters per second.