System and method for monitoring laser shock processing

Abstract

A method and system for monitoring laser shock peening of a work piece. A line spectrum is obtained from radiation emitted by a plasma produced by a laser shock peening process. The shape of the line spectrum about its emission peak is compared to a defined line shape to verify proper operation of the laser shock peening process. The line shape may be a Lorentzian line shape corresponding to a desired line shape. The line shape may a Gaussian line shape corresponding to an undesired line shape. The system can also detect the failure mode that occurs when the opaque layer is broken through by detecting the plasma spectral component produced by the work piece material, along with the plasma produced by the opaque layer.

1 - 26 . (canceled)  
   
   
       27 . A laser shock peening system, comprising: 
 a pulsed laser operable to direct a pulsed laser beam toward an opaque layer disposed on a surface of a work piece;    a spectrometer operable to produce a line spectrum of radiation emitted by a plasma produced by the pulsed laser during a shock peening process;    a spectrum analyzer operable to compare line broadening of the line spectrum about an emission peak with line broadening about a peak in a defined line shape; and    a process control system configured to control, based upon the comparison, the laser shock peening system to alter at least one of laser energy, laser beam diameter at a work piece, rise time, or pulse width of a laser beam produced by the laser to produce a plasma.    
   
   
       28 . The system as recited in  claim 27 , wherein the defined line shape comprises a curve fit of the line spectrum of radiation emitted by a plasma produced by the pulsed laser.  
   
   
       29 . The system as recited in  claim 28 , wherein the spectrum analyzer is operable to produce the curve fit of the line spectrum of radiation emitted by a plasma produced by the pulsed laser.  
   
   
       30 . The system as recited in  claim 29 , wherein the spectrum analyzer is operable to produce a graphical representation of the line spectrum and the curve fit of the line spectrum.  
   
   
       31 . The system as recited in  claim 30 , wherein the curve fit is a Lorentzian curve fit.  
   
   
       32 . The system as recited in  claim 30 , wherein the curve fit is a Gaussian curve fit.  
   
   
       33 . The system as recited in  claim 29 , wherein the sprectrum analyzer is operable to utilize a regression technique to relate the line spectrum to the curve fit of the line spectrum in a mathematical form.  
   
   
       34 . The system as recited in  claim 33 , wherein the process control system is operable to adjust or stop operation of the laser shock peening system when the spectrum analyzer establishes that line broadening of the line spectrum about an emission peak differs by a defined amount from line broadening about the peak in the defined line shape.  
   
   
       35 . The system as recited in  claim 27 , further comprising: 
 a camera operable to convert the spectrum produced by the spectrometer to a signal representative of the spectrum, wherein the signal representative of the spectrum is coupled to the spectrum analyzer.    
   
   
       36 . The system as recited in  claim 27 , comprising a system for providing or adjusting a layer of water over the opaque layer disposed on the surface of the work piece.  
   
   
       37 . The method as recited in  claim 27 , wherein the spectrum analyzer is operable to produce a Lorentzian and a Gaussian curve fit of the line spectrum of radiation emitted by a plasma produced by the pulsed laser and to compare the Lorentzian and Gaussian curve fits.  
   
   
       38 . The method as recited in  claim 37 , wherein the spectrum analyzer is operable to establish a coefficient of multiple determination of the Lorentzian curve fit and the Gaussian curve fit.  
   
   
       39 . The method as recited in  claim 38 , wherein the spectrum analyzer is operable to alter a laser peening system operating parameter when the coefficient of multiple determination of the Lorentzian curve fit does not exceed the coefficient of multiple determination of the Gaussian curve fit by a desired amount.  
   
   
       40 . A laser shock peening process monitoring system, comprising: 
 means for imaging radiation emitted by laser induced plasma produced by the laser shock peening process    means for producing a line spectrum around an emission peak of the radiation emitted by the laser induced plasma, and    means for verifying proper operation of the laser peening process based on broadening of the line spectrum about the emission peak of the radiation emitted by the laser induced plasma.    
   
   
       41 . A laser shock peening system, comprising: 
 a pulsed laser operable to direct a pulsed laser beam toward an opaque layer disposed on a surface of a work piece;    a spectrometer operable to produce a line spectrum of radiation emitted by a plasma produced by the pulsed laser;    a spectrum analyzer operable to compare line broadening of the line spectrum about an emission peak with line broadening about a peak in a defined line shape; and    a process control system configured to control, based upon the comparison, the laser shock peening system to alter a parameter of the laser to produce a plasma.    
   
   
       42 . The system as recited in  claim 41 , wherein the process control system alters laser energy based upon the comparison.  
   
   
       43 . The system as recited in  claim 41 , wherein the process control system alters laser beam diameter at a work piece based upon the comparison.  
   
   
       44 . The system as recited in  claim 41 , wherein the process control system alters rise time based upon the comparison.  
   
   
       45 . The system as recited in  claim 41 , wherein the process control system alters pulse width of a laser beam produced by the laser based upon the comparison.  
   
   
       46 . The system as recited in  claim 41 , wherein the defined line shape comprises a curve fit of the line spectrum of radiation emitted by a plasma produced by the pulsed laser.