Laser shock peening, also known as “laser peening” and “LSP,” is a substitute or complementary process for traditional shot peening that uses cold working to produce a deep (e.g., more than 1 mm) compressive residual stress layer and modify mechanical properties of materials by impacting the material with enough force to create plastic deformation. Laser peening uses amplified high energy laser pulses (e.g., pulse widths of 10-25 ns with repetition rates up to 200 Hz) to generate a plasma plume and cause a rapid rise of pressure on the surface of a part.
As the shockwave travels into the part, some of the energy of the shockwave is absorbed during the plastic deformation of the part material. Plastic deformation is also known as cold working. Laser peening typically uses a laser pulse width of about 8 nanoseconds (ns) to about 40 ns. A typical spot diameter for a laser beam in laser peening is about 1.0 mm to about 8.0 mm. Fluence is the measure of energy delivered per unit area. In laser peening applications, fluence is typically over 100 J/cm2. Power density must be greater than the Hugoniot elastic limit (HEL) of the material to induce plastic deformation and the associated compressive residual stress. Although the HEL for some materials is as low as about 3 GW/cm2, the typical power densities used for laser peening are typically in the 6 GW/cm2 to 12 GW/cm2 range.
Laser peening can be used to form the shape of a part. The compressive stress pattern, location, and depth can be controlled to generate specific shapes of parts. However, laser peen forming can be an inefficient method for shaping a part because determining the location of laser peening application, as well as the laser peening parameters (e.g., pulse width, spot diameter, fluence, and power density), to produce the desired shape and/or surface contour of the part is often time intensive.
What is needed is a system and method for efficient shaping of a part using laser peen forming.
In one aspect, a method for imparting a predetermined surface contour to a part is provided, the method comprising: identifying a compressive residual stress profile for providing the part with the predetermined surface contour; and laser peening a surface of the part in a treatment mode predetermined with reference to the identified compressive residual stress profile, thereby inducing plastic deformation in the part and thereby imparting a predetermined surface contour to the part that is a different surface contour than the part had prior to the laser peening.
In another aspect, a method for laser peen forming a part to induce a predetermined surface contour is provided, the method comprising: providing a part to be laser peen formed; developing a finite element model of the part; performing a finite element analysis on the model to determine a compressive residual stress profile for providing the part with the predetermined surface contour; laser peening a surface of the part in a treatment mode predetermined with reference to the identified compressive residual stress profile; and measuring the laser peen formed part and verifying imparting of the predetermined surface contour.
In another aspect, a method for laser peen correcting a non-conforming part is provided, the method comprising: providing a non-conforming part to be laser peen corrected; measuring the non-conforming part to determine the degree and location of the part non-conformity; developing a finite element model of the non-conforming part; performing a finite element analysis on the model to determine a compressive residual stress profile to bring the part into conformance; laser peening a surface of the non-conforming part in a treatment mode predetermined with reference to the identified compressive residual stress profile; and measuring the laser peen corrected part and verifying conformance of the part.
The accompanying figures, which are incorporated in and constitute a part of the specification, illustrate various example systems and are used merely to illustrate various example aspects. In the figures, like elements bear like reference numerals.
With reference to
Apparatus 100 may include a DPSSL oscillator 102, a modulator 104, and an amplifier 106. DPSSL oscillator 102 may be configured to produce and output a pulsed laser beam 108 to modulator 104, which may modify pulsed laser beam 108 and output a modified beam 110 to amplifier 106. Apparatus 100 may also include an optical filter 112, an optical isolator 114, and a waveplate 116. Optical filter 112 may further modify beam 110 from modulator 104 and output a modified beam 118 toward amplifier 106.
Apparatus 100 may also include a second optical isolator 120, a beam delivery device 122, and a laser peening cell 124. Optical isolator 120 may pass a modified and amplified beam 126 from amplifier 106 to beam delivery device 122, which may deliver modified and amplified beam 126 to laser peening cell 124 containing target part 101. Alternatively, optical isolator 120 may pass modified and amplified beam 126 from amplifier 106 to beam delivery device 122, which may deliver modified and amplified beam 126 directly to target part 101.
Any laser peening system capable of delivering a laser beam having the parameters described herein is contemplated for use in the present application. Nonlimiting example laser peening systems may include those manufactured by LSP Technologies, Inc. under the Procudo® brand, such as for example, those described in one or more of U.S. Pat. Nos. 10,819,079 and 9,744,618 and PCT Patent Application Publication Nos. WO2022/019906A1 and WO2021/183402A1.
Laser peening can be used to peen form the shape of the part. The compressive stress pattern, location, and depth can be controlled to generate specific shapes/surface contours of parts. The compressive stress pattern, location, and depth form a compressive residual stress profile. A predetermined surface contour can be imparted to a part by identifying a compressive residual stress profile for providing the part with the predetermined surface contour, and by inducing plastic deformation in the part by laser peening the part in a treatment mode predetermined with reference to the identified compressive residual stress profile.
Determining the location(s) on part 400 to apply laser peening includes modeling part 400 using finite element modeling, comprising a plurality of elements 402. Finite element analysis software may be used to identify the compressive residual stress profile to be applied to obtain the predetermined shape and/or surface contour of part 400, based upon the finite element model. Finite element analysis software may be used to identify the laser peening parameters (e.g., laser beam energy, pulse width, rise time, spot diameter, spot area, spot overlap, or spot shape), to produce the desired shape and/or surface contour of part 400 after laser peening application, based upon the finite element model. Laser peening parameters (e.g., laser beam energy, pulse width, rise time, spot diameter, spot area, spot overlap, or spot shape) form a treatment mode.
Following determination of the compressive residual stress profile to be applied to obtain the predetermined shape and/or surface contour of part 400, a formed modeled part 420 (illustrated in
A first compressive residual stress profile is applied to a first side of a preformed example modeled part 400 via a first treatment mode. A second compressive residual stress profile is applied to a second side of preformed example modeled part 400 via a second treatment mode. The imparted surface contours are different surface contours than part 400 had prior to the laser peening. The result is a formed example modeled part 420 including a plurality of elements 422. Part 420 is a post-laser peen formed part, having a predetermined shape and/or surface contour as established with respect to preformed part 400.
The compressive residual stress profiles are then applied, in reality, to the physically existing part that is modeled as modeled part 400, at the location of elements 404, using the treatment modes. The post-laser peen formed part is measured to verify whether it accurately assumed the predetermined shape and/or surface contour.
Following determination of the compressive residual stress profile to be applied to obtain the predetermined shape and/or surface contour of part 500, a formed modeled part 520 (illustrated in
The compressive residual stress profiles are then applied, in reality, to the physically existing part that is modeled as modeled part 500, at the location of elements 504, using the treatment modes. The post-laser peen formed part is measured to verify whether it accurately assumed the predetermined shape and/or surface contour.
Following determination of the compressive residual stress profile to be applied to obtain the predetermined shape and/or surface contour of part 600, a formed modeled part 620 (illustrated in
The compressive residual stress profiles are then applied, in reality, to the physically existing part that is modeled as modeled part 600, at the location of elements 604, using the treatment modes. The post-laser peen formed part is measured to verify whether it accurately assumed the predetermined shape and/or surface contour.
Following determination of the compressive residual stress profile to be applied to obtain the predetermined shape and/or surface contour of part 700, a formed modeled part 720 (illustrated in
The compressive residual stress profiles are then applied, in reality, to the physically existing part that is modeled as modeled part 700, at the location of peen forming elements 704, using the treatment modes. The post-laser peen formed part is measured to verify whether it accurately assumed the predetermined shape and/or surface contour.
In another aspect, compressive residual stress profiles may be applied, in reality, to a physically existing part that is constrained to a form. This constraint is an elastic constraint. The part is constrained to the form prior to laser peening the surface of the part. Accordingly, an existing part, constrained (elastic constraint) to a form is provided and modeled as modeled part 400, 500, 600, 700. Compressive residual stress profiles are developed, and then applied, in reality, to the physically existing part that is constrained to a form, at the location of elements 404, 504, 604, 704. The application of the compressive residual stress profile “locks in” the elastic constraint, causing the physically exiting part to remain in its shaped contour. The post-laser peen formed part is removed from the form and measured to verify whether it accurately assumed the predetermined shape and/or surface contour.
Modeled shaft 810 may be modeled after an existing non-conforming (out-of-specification) cam shaft. Modeled shaft 810 includes an elongated portion 816 and an eccentric lobe 818. Modeled shaft 810 includes a plurality of elements 812. As illustrated in
Finite element analysis software may be used to identify the compressive residual stress profile to be applied to modeled shaft 810 to obtain the predetermined correction of modeled shaft 810, based upon the finite element model. The compressive residual stress profile to be applied to modeled shaft 810 is designed to bring modeled shaft 810 into specification. Finite element analysis software may be used to identify the laser peening parameters (e.g., laser beam energy, pulse width, rise time, spot diameter, spot area, spot overlap, or spot shape) to produce the corrected modeled shaft 810 after laser peening application, based upon the finite element model. Laser peening parameters (e.g., laser beam energy, pulse width, rise time, spot diameter, spot area, spot overlap, or spot shape) form a treatment mode.
Following determination of the compressive residual stress profile to be applied to correct shaft 810, a corrected modeled shaft 830 (illustrated in
The compressive residual stress profiles are then applied, in reality, to the physically existing shaft that is modeled as modeled shaft 810, at the location of elements 814, using the treatment modes. The post-laser peen formed shaft is measured to verify whether it accurately assumed the predetermined shape and/or surface contour.
In the case of one examination of actual, physical cam shafts, the predicted (modeled) runout without corrective laser peening was 0.052 mm (0.002 in.). The average measured runout of eight cam shafts, without corrective laser peening, was 0.05 mm (0.002 in.). After the application of corrective laser peening, the predicted (modeled) runout in the cam shafts was 0.004 mm (0.0001 in.). The average measured runout of twenty-four cam shafts, following application of corrective laser peening, was less than 0.01 mm (0.0004 in.), which was the maximum runout permitted pursuant to the specification of that particular cam shaft design.
Modeled frame element 910 may be modeled after an existing non-conforming (out-of-specification) frame element. Modeled frame element 910 includes an elongated central portion 916 and two lateral portions 918 extending from elongated central portion 916. Modeled frame element 910 includes a plurality of finite elements 912 generated during finite element modeling. As illustrated in
Finite element analysis software may be used to identify the compressive residual stress profile to be applied to modeled frame element 910 to obtain the predetermined correction of modeled frame element 910, based upon the finite element model. The compressive residual stress profile to be applied to modeled frame element 910 is designed to bring modeled frame element 910 into specification. Finite element analysis software may be used to identify the laser peening parameters (e.g., laser beam energy, pulse width, rise time, spot diameter, spot area, spot overlap, or spot shape), to produce the corrected modeled frame element 910 after laser peening application, based upon the finite element model. Laser peening parameters (e.g., laser beam energy, pulse width, rise time, spot diameter, spot area, spot overlap, or spot shape) form a treatment mode.
Following determination of the compressive residual stress profile to be applied to correct frame element 910, a corrected modeled frame element 930 (illustrated in
The compressive residual stress profiles are then applied, in reality, to the physical existing frame element that is modeled as modeled frame element 910, at the location of the peen forming elements, using the treatment modes. The post-laser peen formed frame element is measured to verify whether it accurately assumed the predetermined shape and/or surface contour.
Modeled turbine blade 1010 may be modeled after an existing non-conforming (out-of-specification) turbine blade. Modeled turbine blade 1010 includes a plurality of elements 1012. Modeled turbine blade 1010 is out-of-specification, and as such, modeled turbine blade 1010 is measured to determine the degree and location of non-conformity.
Finite element analysis software may be used to identify the compressive residual stress profile to be applied to modeled turbine blade 1010 to obtain the predetermined correction of modeled turbine blade 1010, based upon the finite element model. The compressive residual stress profile to be applied to modeled turbine blade 1010 is designed to bring modeled turbine blade 1010 into specification. Finite element analysis software may be used to identify the laser peening parameters (e.g., laser beam energy, pulse width, rise time, spot diameter, spot area, spot overlap, or spot shape) necessary to produce the corrected modeled turbine blade 1010 after laser peening application, based upon the finite element model. Laser peening parameters (e.g., laser beam energy, pulse width, rise time, spot diameter, spot area, spot overlap, or spot shape) form a treatment mode.
Following determination of the compressive residual stress profile to be applied to correct turbine blade 1010, a corrected modeled turbine blade 1030 (illustrated in
The compressive residual stress profiles are then applied, in reality, to the physically existing turbine blade that is modeled as modeled turbine blade 1010, at the location of peen forming elements 1014, using the treatment modes. The post-laser peen formed turbine blade is measured to verify whether it accurately assumed the predetermined shape and/or surface contour.
In another aspect, compressive residual stress profiles may be applied, in reality, to a physically existing non-conforming part that is constrained to a form. This constraint is an elastic constraint. The non-conforming part is constrained to the form prior to laser peening the surface of the part. Accordingly, an existing part, constrained (elastic constraint) to a form is provided and modeled as modeled part (e.g., modeled shaft 810, modeled frame element 910, or modeled turbine blade 1010. Compressive residual stress profiles are developed, and then applied, in reality, to the physically existing part that is constrained to a form, at the location of elements 814, 1014. The application of the compressive residual stress profile “locks in” the elastic constraint, causing the physically exiting part to remain in its shaped contour. The post-laser peen formed part is removed from the form and measured to verify whether it accurately assumed the predetermined shape and/or surface contour.
The predetermined surface contour imparted to the part may be planar. The predetermined surface contour imparted to the part may be non-planar.
To the extent that the term “includes” or “including” is used in the specification or the claims, it is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term “or” is employed (e.g., A or B) it is intended to mean “A or B or both.” When the applicants intend to indicate “only A or B but not both” then the term “only A or B but not both” will be employed. Thus, use of the term “or” herein is the inclusive, and not the exclusive use. See Bryan A. Garner, A Dictionary of Modern Legal Usage 624 (2d. Ed. 1995). Also, to the extent that the terms “in” or “into” are used in the specification or the claims, it is intended to additionally mean “on” or “onto.” To the extent that the term “substantially” is used in the specification or the claims, it is intended to take into consideration the degree of precision available in manufacturing. To the extent that the term “selectively” is used in the specification or the claims, it is intended to refer to a condition of a component wherein a user of the apparatus may activate or deactivate the feature or function of the component as is necessary or desired in use of the apparatus. To the extent that the term “operatively connected” is used in the specification or the claims, it is intended to mean that the identified components are connected in a way to perform a designated function. As used in the specification and the claims, the singular forms “a,” “an,” and “the” include the plural. Finally, where the term “about” is used in conjunction with a number, it is intended to include ±10% of the number. In other words, “about 10” may mean from 9 to 11.
As stated above, while the present application has been illustrated by the description of embodiments and aspects thereof, and while the embodiments and aspects have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art, having the benefit of the present application. Therefore, the application, in its broader aspects, is not limited to the specific details, illustrative examples shown, or any apparatus referred to. Departures may be made from such details, examples, and apparatuses without departing from the spirit or scope of the general inventive concept.
This application is a continuation-in-part of U.S. patent application Ser. No. 15/484,184, filed on Apr. 11, 2017, which claims priority to U.S. Provisional Patent Application No. 62/320,694, filed on Apr. 11, 2016, each of which is incorporated by reference herein in its entirety.
Number | Date | Country | |
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62320694 | Apr 2016 | US |
Number | Date | Country | |
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Parent | 15484184 | Apr 2017 | US |
Child | 17695716 | US |