Electric heating – Metal heating – By arc
Reexamination Certificate
2002-09-13
2004-11-16
Heinrich, Samuel M. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121680, C219S121780
Reexamination Certificate
active
06818854
ABSTRACT:
BACKGROUND
1. Field of Endeavor
The present invention relates to laser peening and more particularly to laser peening with fiber optic delivery.
2. State of Technology
U.S. Pat. No. 5,131,957 to Harold M. Epstein for material properties, issued Jul. 21, 1992 provides background information, “The interaction of a pulsed laser beam with the surface of a material gives rise to a pressure pulse (shock wave) that propagates into the material and changes its properties. In the case of metals, for example, the changes in properties are caused by the introduction of cold work that increases the hardness and strength of the material. By appropriate tailoring of the peak pressure and width of the shock wave, it is possible to enhance selected material properties, such as fatigue strength, and at the same time not adversely affect other properties, such as corrosion resistance. It is possible also to shock process a finished piece of material without disturbing its surface, where a thin sacrificial layer of overlay material has been attached intimately onto the surface of the workpiece.”
U.S. Pat. No. 5,911,891 to Jeff L. Dulaney, et al. for laser shock peening with tailored multiple laser beams, issued Jun. 15, 1990 provides background information, “Method of changing the residual compressive stresses of an area of a workpiece by tailoring multiple laser beams applied to the workpiece. In one embodiment, a relatively long duration laser pulse is applied to the workpiece followed by a relatively short duration laser pulse. Other tailoring embodiments used to increase the total residual compressive stress of workpieces include blending two laser pulses, or splicing them utilizing a first short sliced-type beam combined with a relatively long duration, high powered gaussian laser beam pulse. A third embodiment utilizes two or more laser beams or pulses of different wavelengths.”
U.S. Pat. No. 6,410,884 to Lloyd Hackel and Harris Fritz for contour forming of metals by laser peening issued Jun. 25, 2002 provides background information, “Improving the strength of metals by cold working undoubtedly was discovered early in civilization, as ancient man hammered out his weapons and tools. Since the 1950s, shot peening has been used as a means to improve the fatigue properties of metals. Another method of shock processing involves the use of high explosive materials in contact with the metal surface. The use of high intensity laser outputs for the generation of mechanical shock waves to treat the surfaces of metals has been well known since the 1970s. The laser shock process can be used to generate compressive stresses in the metal surfaces adding strength and resistance to corrosive failure.”
SUMMARY
Features and advantages of the present invention will become apparent from the following description. Applicants are providing this description, which includes drawings and examples of specific embodiments, to give a broad representation of the invention. Various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this description and by practice of the invention. The scope of the invention is not intended to be limited to the particular forms disclosed and the invention covers all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the claims.
The present invention provides a system for processing a workpiece using a laser unit. The laser unit produces at least one laser pulse. A laser processing system is used to process the workpiece using the at least one laser pulse. A fiber optic cable system is used for transmitting the at least one laser pulse from the laser system to the laser processing unit. In one embodiment a multiplicity of individual lasers are used and the fiber optic cable system includes a corresponding multiplicity of individual optical fibers for transmitting the at least one laser pulse. In one embodiment the laser system is an array of low pulse energy but high repetition rate lasers. In one embodiment the laser system produces a laser beam. A fiber optic bundle is used for delivering the laser beam to the workpiece. In one embodiment the laser system uses water to cover at least a portion of the workpiece. In one embodiment the workpiece is under the water. In one embodiment the laser processing unit is a laser peening system. In one embodiment the laser peening system uses water to cover at least a portion of the workpiece. In one embodiment the workpiece is under the water. In one embodiment the laser peening system uses a laser pulse of green wavelength. In one embodiment the laser pulse of green wavelength is used to laser peen the workpiece under the water.
The invention is susceptible to modifications and alternative forms. Specific embodiments are shown by way of example. It is to be understood that the invention is not limited to the particular forms disclosed. The invention covers all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the claims.
REFERENCES:
patent: 4937421 (1990-06-01), Ortiz et al.
patent: 5131957 (1992-07-01), Epstein et al.
patent: 5333077 (1994-07-01), Legar et al.
patent: 5436990 (1995-07-01), Head et al.
patent: 5617492 (1997-04-01), Beach et al.
patent: 5911891 (1999-06-01), Dulaney et al.
patent: 5978407 (1999-11-01), Chang et al.
patent: 6064035 (2000-05-01), Toller et al.
patent: 6078022 (2000-06-01), Dulaney et al.
patent: 6127649 (2000-10-01), Toller et al.
patent: 6198069 (2001-03-01), Hackel et al.
patent: 6288358 (2001-09-01), Dulaney et al.
patent: 6410884 (2002-06-01), Hackel et al.
Sano, Y., et al., “Development and Application of Laser Peening System to Prevent Stress Corrosion Cracking of Reactor Core Shroud,” ICONE-8441, Proceedings of ICONE 8, 8thInt'l Conference on Nuclear Engineering, Apr. 2-6, 2000, Baltimore, MD, USA, pp. 1-10.
Fabbro, R. et al., “Physics and Applications of Laser-Shock Processing,” Journal of Laser Applications, vol. 10, No. 6, Dec. 1998, pp. 265-279.
Sano, Y., et al., “Residual Stress Improvement Mechanism on Metal Material by Underwater Laser Irradiaiton,” Kaz Transpacific, vol. 42, No. 6, (2000), pp. 93-99.
Ault Earl R.
Friedman Herbert W.
Scheibner Karl F.
Heinrich Samuel M.
Scott Eddie E.
The Regents of the University of California
Thompson Alan H.
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