Laser shock peening quality assurance by acoustic analysis

A method for quality control testing of a laser shock peening process of production workpieces, said method comprising the following steps:

• (a) laser shock peening a surface of the production workpiece by firing a plurality of laser beam pulses from a laser shock peening apparatus on a surface of the production workpiece and forming a plurality of corresponding plasmas, each one of the plasmas for each one of the pulses having a duration in which the plasma causes a region to form beneath the surface, the region having deep compressive residual stresses imparted by the laser shock peening process,
• (b) measuring airborne and workpiece-borne acoustic signals for each of the laser beam pulses during a period of time during the duration of each corresponding one of the plasmas, wherein the workpiece-borne acoustic signal is measured with an acoustic transducer mounted to the workpiece which detects acoustic signals though the workpiece and the airborne acoustic signal is measured with a microphone spaced located away from the workpiece and which detects airborne acoustic signals,
• (c) calculating airborne and workpiece-borne acoustic energy parameter values for each of the corresponding acoustic signals,
• (d) calculating airborne and workpiece-borne statistical function values of the workpiece based on the acoustic energy parameter values, and
• (e) comparing the airborne and workpiece-borne statistical function values to corresponding pass or fail criteria for quality assurance of the laser shock peening process for accepting or rejecting the workpiece.