Mitigation of stress corrosion and fatigue by surface conditioning

Abstract

Method and apparatus for surface conditioning a metal surface typically having irregular surface contours, by rubbing the metal surface with a surface conditioning device having a plurality of bristles which contact the metal surface during the rubbing and effect tensile stress reduction or degraded layer removal in the metal surface.

1 . A method of conditioning a metal surface, comprising rubbing the metal surface with a surface conditioning means comprising a plurality of bristles which contact said metal surface during said rubbing and effect tensile stress reduction. 
   
   
       2 . Method as in  claim 1  wherein said tensile stress is reduced below the metal surface. 
   
   
       3 . Method as in  claim 1  wherein said tensile stress is reduced to compressive stress. 
   
   
       4 . Method as in  claim 1  wherein said tensile stress is a residual stress not loaded externally. 
   
   
       5 . Method as in  claim 1  wherein said plurality of bristles are in the form of a cylindrical brush. 
   
   
       6 . Method as in  claim 5  wherein said cylindrical brush is helical or circular. 
   
   
       7 . Method as in  claim 1  wherein said plurality of bristles are mounted on a plate member. 
   
   
       8 . Method as in  claim 1  wherein said plurality of bristles are mounted on a radiused member and have a contoured brush surface such that a contour of the metal surface essentially corresponds to tshe contoured brush surface. 
   
   
       9 . Method an in  claim 1  wherein an abrasive material is embedded in said bristles. 
   
   
       10 . Method an in  claim 1  wherein an abrasive material is coated on said bristles. 
   
   
       11 . Method as in  claim 10  wherein said abrasive material is adhered to the bristles with an adhesive. 
   
   
       12 . Method as in  claim 10  wherein said abrasive material is applied as a wet slurry to the bristles. 
   
   
       13 . Method as in  claim 9  wherein said abrasive material is selected from the group consisting of aluminum oxide, silicon carbide, silicon nitride, zirconium, and synthetic diamond. 
   
   
       14 . Method as in  claim 10  wherein said abrasive material is selected from the group consisting of aluminum oxide, silicon carbide, silicon nitride, zirconium, and synthetic diamond. 
   
   
       15 . Method as in  claim 1  wherein said surface to be conditioned is wetted by a coolant fluid. 
   
   
       16 . Method as in  claim 1  wherein said surface to be conditioned is submerged in a coolant fluid. 
   
   
       17 . Method as in  claim 15  wherein said coolant fluid is water. 
   
   
       18 . Method as in  claim 16  wherein said coolant fluid is water. 
   
   
       19 . Method as in  claim 1  wherein said surface conditioning means includes an electric, hydraulic, or pneumatic motor to effect movement of said bristles. 
   
   
       20 . Method as in  claim 1  wherein said metal surface is first rubbed with bristles coated or embedded with a coarser abrasive, followed by one or more further rubbing steps with bristles coated or embedded with a finer abrasive. 
   
   
       21 . Method as in  claim 1  wherein said surface conditioning improves surface micro-geometry smoothness, eliminates degraded surface composition or microstructure, removes micro-cracked or corroded surface layer, removes cold-worked surface layer, removes fatigue-damaged surface layer, and improves surface residual stress. 
   
   
       22 . A method of conditioning a metal surface, comprising rubbing the metal surface with a surface conditioning means comprising a plurality of bristles which contact said metal surface during said rubbing and effect degraded layer removal in the metal surface. 
   
   
       23 . Method as in  claim 22  wherein said degraded layer removal is cold work or environmental degradation. 
   
   
       24 . A surface treatment tool for conditioning a surface, comprising:
 a first motor operatively connected to an abrasive element having an external surface, for driving said abrasive element in frictional engagement with a surface to be treated;   a clamping element for mounting the tool to an anchor;   a second motor operatively connected to a extension-retraction system for effecting movement of said abrasive element towards and away from said surface to be treated.   
   
   
       25 . Tool as in  claim 24  wherein said abrasive element is a brush. 
   
   
       26 . Tool as in  claim 25  wherein said brush comprises bristles in a helical configuration. 
   
   
       27 . Tool as in  claim 24  further comprising a motor operatively connected to said abrasive element for causing lateral movement of said element across and in contact with said surface to be treated. 
   
   
       28 . A surface treatment tool for conditioning a surface, comprising:
 a first motor operatively connected to an abrasive element for driving said abrasive element in frictional engagement with a surface to be treated;   a clamping element for mounting the tool to an anchor;   a second motor operatively connected to said abrasive element for causing lateral movement of said abrasive element across said surface to be treated;   a tilting system for causing angular tilting the abrasive element from a non-tilted to a tilted orientation relative to the anchor to permit said abrasive element to follow changes in orientation of the surface to be treated.   
   
   
       29 . Tool as in  claim 28  wherein said abrasive element comprises a circular bristle brush plate member mounted on a turntable. 
   
   
       30 . A surface treatment tool for conditioning a surface, comprising:
 a first motor operatively connected to an abrasive element for driving said abrasive element in frictional engagement with a surface to be treated;   a clamping element for mounting the tool to an anchor;   a second motor operatively connected to a gearing arrangement for effecting translational movement of said abrasive element across the surface to be treated;   a third motor operatively connected to said abrasive element for effecting movement of said abrasive element towards and away from said surface to be treated.   
   
   
       31 . Tool as in  claim 30  wherein said abrasive element comprises a plurality of bristles. 
   
   
       32 . Tool as in  claim 31  wherein said bristles are fabricated from a plastics or rubber material. 
   
   
       33 . Tool as in  claim 31  wherein an abrasive material is embedded in said bristles. 
   
   
       34 . Tool as in  claim 31  wherein an abrasive material is coated on said bristles. 
   
   
       35 . Tool as in  claim 33  wherein said abrasive material is adhered to the bristles with an adhesive. 
   
   
       36 . Tool as in  claim 34  wherein said abrasive material is selected from the group consisting of aluminum oxide, silicon carbide, silicon nitride, zirconium, and synthetic diamond. 
   
   
       37 . Tool as in  claim 34  wherein said abrasive material is selected from the group consisting of aluminum oxide, silicon carbide, silicon nitride, zirconium, and synthetic diamond.