Abstract: A method of controlling the application of laser peening overlays on the surface of a workpiece to reduce the variability of shock waves generated therein, comprises applying an energy-absorbing overlay to a portion of the surface of a workpiece, measuring the thickness of the energy-absorbing overlay in at least one location on the energy-absorbing overlay, applying a transparent overlay material over the energy-absorbing overlay, measuring the thickness of the transparent overlay in at least one location on the transparent overlay, determining if the measured values for each overlay is within a specified range, and directing a pulse of coherent energy to the workpiece to create a shock wave therein when the measured values are within the specified range.

Abstract: A laser shock processing treatment is employed to condition the mating surfaces of various fastener elements, such as screws, bolts, splines, keys, and keyways. In a screw, for example, the threaded surface is laser shock processed to form laser shock processed surfaces at the thread root portion of the screw. Regions of compressive residual stresses imparted by laser shock processing are thereby formed and extend into the screw body from the laser shock processed surfaces. In a keyway, for example, the keyway surface is laser shock processed to form laser shock processed surfaces within the keyway. Regions of compressive residual stresses imparted by laser shock processing are thereby formed and extend into the keyway body from the laser shock processed surfaces. The compressive residual stress regions enhance the rigidity and torsional stiffness of the fastener elements and improve their fatigue properties.

Abstract: A laser shock processing treatment enables a selectively adjustable and customized compressive residual stress distribution profile to be developed within a workpiece by tailoring the size and shape of the laser beam spots. One peening operation applies to the workpiece a first pattern having relatively large laser beam spots and then applies a second pattern having relatively small laser beam spots. The composite use of such small and large beam spots enables the stress distribution profile to be tailored to the part specifications. The large beam spots maximize the depth of compressive residual stress in the part, while the small beam spots optimize the surface compressive residual stresses of the part. The use of small spot beam patterns allows untreated or improperly processed areas to be laser peened.

Abstract: A laser gain medium and a method of manufacturing a laser medium, such as a laser rod, or slab for use in high-powered laser peening systems. A laser medium and method reduces stress risers along the surface of the amplifier medium by grit blasting, polishing, etching, annealing, and by eliminating platinum inclusions within the laser glass.

Abstract: Articles produced by laser shock processing exhibit various compressive residual stress distribution profiles. A gas turbine engine airfoil includes an asymmetrical stress profile formed through the thickness of its thin section. The articles include plural laser shock peened surfaces and plural regions having deep compressive residual stresses imparted by laser shock peening extending into the article from the laser peened surfaces. One article includes at least one set of simultaneously formed, adjacent non-overlapping laser shock peened surfaces. Another article includes at least one set of opposing laser shock peened surfaces formed at different times at opposite sides of the article. Another article includes at least one set of opposing laser shock peened surfaces formed simultaneously at opposite sides of the article using laser beams having different pulse lengths.

Abstract: A method and apparatus for increasing the effectiveness and efficiency of laser shock processing of a solid material. The method includes applying an energy absorbing coating to a portion of the surface of a solid material, applying an ultraviolet curable resin to the coated portion of the surface of the solid material, applying an ultraviolet light to the curable resin to form a pellicle over the energy absorbing coating on the surface of the solid material, and applying a transparent overlay to the pellicular portion of the solid material. A pulse of coherent laser energy is directed to the coated portion of the solid material to create a shockwave. After the pulse of coherent energy is directed to the solid material, a high-speed jet of fluid may be directed to the coated portion of the solid material to remove the remaining coating from the solid material.

Abstract: An image processing system for monitoring a laser peening process includes a laser peening system having a workpiece positioner and a system controller. A video camera is utilized for forming an electronic image of at least a portion of a workpiece. An image processing computer is connected to the video camera, and the laser peening controller includes a program to determine a position of the workpiece.

Abstract: A method and apparatus for increasing the effectiveness and efficiency of laser shock processing of a solid material. The method includes applying an energy absorbing coating to a portion of the surface of a solid material, applying an ultraviolet curable resin to the coated portion of the surface of the solid material, applying an ultraviolet light to the curable resin to form a pellicle over the energy absorbing coating on the surface of the solid material, and applying a transparent overlay to the pellicular portion of the solid material. A pulse of coherent laser energy is directed to the coated portion of the solid material to create a shockwave. After the pulse of coherent energy is directed to the solid material, a high-speed jet of fluid may be directed to the coated portion of the solid material to remove the remaining coating from the solid material.

Abstract: Various laser shock processing methods are provided to establish selective compressive residual stress distribution profiles within a workpiece. An asymmetrical stress distribution profile may be formed through the thickness of a thin section of a gas turbine engine airfoil. One method involves simultaneously irradiating a workpiece with a set of laser beams to form a corresponding set of adjacent non-overlapping laser shock peened surfaces, enabling the shockwaves to encounter one another. Additionally, opposite sides of the workpiece may be irradiated at different times to form opposing laser shock peened surfaces, enabling the shockwaves to meet at a location apart from the midplane. Furthermore, opposite sides of the workpiece may be irradiated simultaneously using laser beams having different pulse lengths to form opposing laser shock peened surfaces. Moreover, opposite sides of the workpiece may be irradiated simultaneously to form a set of laterally offset laser shock peened surfaces.

Abstract: The present invention enables the processing head to locate itself precisely on the surface of the structure being processed, and to then reposition itself correctly for the next laser spot. Further, the present invention will complete processing a laser peened area, the area including a multiplicity of spots arranged in a specific pattern, and correctly laser peen each spot in the area under control of a controller including control linkages with the laser.

Abstract: A method of controlling the application of laser peening overlays on the surface of a workpiece to reduce the variability of shock waves generated therein, comprises applying an energy-absorbing overlay to a portion of the surface of a workpiece, measuring the thickness of the energy-absorbing overlay in at least one location on the energy-absorbing overlay, applying a transparent overlay material over the energy-absorbing overlay, measuring the thickness of the transparent overlay in at least one location on the transparent overlay, determining if the measured values for each overlay is within a specified range, and directing a pulse of coherent energy to the workpiece to create a shock wave therein when the measured values are within the specified range.

Abstract: The invention, in another form thereof, comprises a method of laser shock peening the surface of a solid material with or without the use of a transparent overlay material. An energy absorbing coating is applied to a portion of the surface of a solid material. An ultraviolet-curable resin coating is applied to the energy absorbing coating and the curable resin is exposed to an ultraviolet light and forms a pellicle over the energy absorbing coating. A pulse of coherent energy is directed to the energy absorbing coating of the solid material to create a shock wave.

Abstract: A laser processing method for processing a hidden surface of a workpiece, the hidden surface being disposed within a recess having an opening. The method includes inserting a reflective member into the recess and directing a pulse of coherent energy to reflect off of said reflective member and impact the hidden surface of a workpiece to create a shock wave. Alteratively a surface of the recess may be modified to laser shock process the hidden surface. In one particular embodiment, the reflective member is specifically shaped toprovide diction of a pulse of coherent energy to a hidden surface so that a substantially uniform energy density is applied to the hidden surface. In an additional embodiment, the method is optimized for preventing damage to the reflective member. In one particular embodiment, the reflective member is composed of a fluid.

Abstract: A method and apparatus for quality control of laser shock processing. The method includes measuring emissions and characteristics of a workpiece when subjected to a pulse of coherent energy from a laser. These empirically measured emissions and characteristics of the workpiece are correlated to theoretical shock pressure, residual stress profile, or fatigue life of the workpiece. The apparatus may include a radiometer or acoustic detection device for measuring these characteristics.

Abstract: A method of controlling the application of laser peening overlays on the surface of a workpiece to reduce the variability of shock waves generated therein, comprises applying an energy-absorbing overlay to a portion of the surface of a workpiece, measuring the thickness of the energy-absorbing overlay in at least one location on the energy-absorbing overlay, applying a transparent overlay material over the energy-absorbing overlay, measuring the thickness of the transparent overlay in at least one location on the transparent overlay, determining if the measured values for each overlay is within a specified range, and directing a pulse of coherent energy to the workpiece to create a shock wave therein when the measured values are within the specified range.

Abstract: An apparatus for measuring the strength of a pressure pulse created from a laser peening device. The apparatus is reusable, and includes a pressure-sensitive medium, a back-up disk, and a cap, all disposed within a housing having a removable lid. All components of the apparatus are replaceable, thereby allowing an operator to utilize the apparatus more than once despite the harsh environment of laser peening.

Abstract: An exfoliation corrosion detection method which enables rapid detection and evaluation of hidden exfoliation corrosion on aircraft with related cost savings. Pressure exerted on the surface by the laser created plasma generates a pressure pulse or shock wave that propagates into the part. When the stress in the shock wave is above the dynamic elastic limit of the material, the surface material yields plastically. This plastic strain creates compressive residual stresses in the surface, thereby enabling detection of exfoliation corrosion, if present.

Abstract: A method of controlling the application of laser peening overlays on the surface of a workpiece to reduce the variability of shock waves generated therein, comprises applying an energy-absorbing overlay to a portion of the surface of a workpiece, measuring the thickness of the energy-absorbing overlay in at least one location on the energy-absorbing overlay, applying a transparent overlay material over the energy-absorbing overlay, measuring the thickness of the transparent overlay in at least one location on the transparent overlay, determining if the measured values for each overlay is within a specified range, and directing a pulse of coherent energy to the workpiece to create a shock wave therein when the measured values are within the specified range.

Abstract: An apparatus and method for providing a substantially debris-free laser beam path for use during laser shock processing. The method and apparatus include a system for removing debris from the laser beam path and a system for preventing debris from entering the laser beam path.

Abstract: A method of testing the operation of a laser peening system includes providing a sensor in a possible laser beam path, applying a transparent overlay material to the sensor, directing a pulse of coherent energy to the sensor through the transparent overlay material to create a shock wave, and determining a characteristic of the created shock wave with the sensor.