CN108546818B - Single-side laser shot peening strengthening method for thin-wall structural member - Google Patents
Single-side laser shot peening strengthening method for thin-wall structural member Download PDFInfo
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- CN108546818B CN108546818B CN201810515226.3A CN201810515226A CN108546818B CN 108546818 B CN108546818 B CN 108546818B CN 201810515226 A CN201810515226 A CN 201810515226A CN 108546818 B CN108546818 B CN 108546818B
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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Abstract
The invention provides a single-side laser shot peening strengthening method of a thin-wall structural member, which comprises the following steps: s1, performing thickness analysis on the thin-wall structural part, and screening N characteristic thickness values; s2, determining the optimal spot size of each thickness of the thin-wall structural member; s3, determining a laser shot blasting path of the thin-wall structural member; s4, performing laser peening on the thin-wall structural member by the laser peening path of the step S3; when the thin-wall structural part is an equal-thickness thin-wall structural part, N is 1; when the thin-wall structural part is a variable-thickness thin-wall structural part, N is more than or equal to 2. Compared with the prior art, the invention has the following beneficial effects: 1. deformation control is realized only through optimization of process parameters without an external clamp or a gasket, so that the universality of the method is improved; 2. residual compressive stress can be obtained on both sides of the thin-wall structure only through single-side laser shot peening strengthening, and the applicability to strengthening of complex structures is improved.
Description
Technical Field
The invention relates to the field of mechanical manufacturing, in particular to a thin-wall structure single-side laser shot peening strengthening process method which is used for realizing deformation control while performing single-side laser shot peening strengthening on variable-thickness thin-wall structures such as blade edges of turbine blades of aero-engines only through optimization of process parameters without using an external clamp or a gasket.
Background
In the service process of the aircraft engine, the blade edge of the blade is easily affected by foreign object damage and high cycle fatigue to generate fatigue failure. The laser shot peening strengthening technology is an effective method for strengthening the surface of the blade of the aero-engine and improving the anti-fatigue and anti-foreign body impact damage performance of the blade, and has very important significance for prolonging the service life of the blade and improving the operation reliability of the aero-engine. However, the thickness of the blade edge of the blade is only 0.4-0.6 mm, the blade edge is a typical variable thickness thin-wall structural member, deformation of the blade edge is always accompanied when the blade edge is subjected to laser shot peening strengthening, and the deformation can greatly affect the aerodynamic performance of the blade, so a laser shot peening strengthening process method of the variable thickness thin-wall structure needs to be established, and the torsional deformation of the variable thickness thin-wall structure is reduced while the strengthening is realized.
The existing solution is to control the deformation by double-sided laser shock. The double-side impact is divided into double-side synchronous and double-side asynchronous, the double-side synchronous impact has no deformation theoretically because of symmetrical load, but because stress waves are superposed in the middle of a sample, the risk of generating internal cracks exists, and the complexity of an optical path and the difficulty of control are increased because of the requirement of the double-side synchronous impact. The double-side asynchronous impact has no problem of stress wave superposition, can effectively control deformation for a flat plate, but has the problem of uncontrollable deformation for some twisted blades. Moreover, for workpieces such as blisks that have some shielding from each other, the optical path is not fully accessible, making it more difficult to achieve double-sided impact. Therefore, the invention provides a process method for single-side laser shot peening.
The invention of application No. 201310224538.6 discloses a method and apparatus for laser shock of aircraft turbine blades by designing flexible clamps and shims to match the shape of the blade to suppress distortion, and optimizing process parameters to achieve distortion control. However, the invention needs to design the clamp separately for the blades with different shapes, the system is complex, and the universality is not enough. In addition, the invention with application number 201310040844.4 discloses a combination method and device for laser shock treatment of engine blades, which achieves the purpose of improving the fatigue life of the blades by increasing the gentle transition area between the strengthened area and the non-strengthened area through controlling the residual stress field of the blades, and the invention does not relate to the control of the blade deformation. In addition, the turbine blade leading edge double-sided asynchronous laser shock peening method disclosed by the invention with the application number of 201710065831.0 and the turbine blade leading edge double-sided synchronous laser shock peening method disclosed by the invention with the application number of 201710065820.2 both realize deformation control in a double-sided laser shock peening mode, but the double-sided optical path system increases the complexity of the system structure and the programming difficulty, and for workpieces with optical path interference structures such as an integral blade disc, an additional light guide system needs to be designed to realize double-sided laser shock peening. In addition, the invention with the application number of EP02250594.5 discloses a double-side synchronous laser peening method for a blisk, which performs double-side laser peening strengthening on a blade by using an elliptical spot shape through two beams of obliquely incident lasers and adjusting the pose of the blisk, but the method also has the problems of complicated structure and difficult programming control.
In summary, none of the conventional laser peening methods for forming a thick and thin-walled structure such as a turbine blade edge of an aircraft engine has a deformation control method for one-sided laser peening that is completely optimized by process parameters without using an external jig. Therefore, a deformation control method suitable for laser peening strengthening of a variable thickness thin-walled structure is needed.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a thin-wall structure single-side laser shot peening strengthening process method, which can realize deformation control while strengthening thin-wall structures such as the blade edge of a turbine blade of an aircraft engine and the like only through optimization of process parameters and single-side laser shot peening without an external clamp or a gasket.
The invention is realized by the following technical scheme:
the invention provides a thin-wall structure single-side laser shot peening strengthening method, which comprises the following steps:
s1, performing thickness analysis on the thin-wall structural part, and screening N characteristic thickness values;
s2, determining the optimal spot size of the thin-wall structural part at different thicknesses;
s3, determining a laser shot blasting path of the thin-wall structural member;
s4, performing laser peening on the thin-wall structural member by the laser peening path of the step S3;
when the thin-wall structural part is an equal-thickness thin-wall structural part, N is 1; when the thin-wall structural part is a variable-thickness thin-wall structural part, N is more than or equal to 2.
Preferably, the thickness analysis method comprises: and (3) performing thickness analysis on the three-dimensional digital model of the thin-wall structural part or performing thickness measurement on the solid part by using a thickness gauge.
As a preferred scheme, the method for determining the optimal spot size comprises the following steps:
selecting a knife edge test piece with single thickness, performing unilateral laser shot peening strengthening without passing through the light spot size, and obtaining a displacement change curve of the end part of the knife edge test piece according to the laser shot peening strengthening with different light spot sizes, wherein the intersection point of the change curve and a zero displacement line is the optimal light spot size corresponding to the thickness.
Preferably, the knife edge test piece comprises a test piece main body and a first step part integrally formed with the test piece main body, two side surfaces of the test piece main body are respectively provided with a pressing plate, the upper surface of each pressing plate is flush with the upper surface of the first step part to form a second step part, the thickness of the first step part is 3-4 times of that of the test piece main body, and the two step parts ensure that the maximum deformation point of the knife edge test piece is at a knife tip without a step surface.
Preferably, the method for determining the laser peening path comprises:
and fitting the N characteristic thickness values and the corresponding optimal spot sizes into a curve d (f) (t), and performing single-side laser shot peening strengthening on all strengthening areas according to the optimal spot sizes corresponding to different thickness values, wherein d is the optimal spot size, and t is the thickness value of an impact point.
Compared with the prior art, the invention has the following beneficial effects:
1. deformation control is realized only through optimization of process parameters without an external clamp or a gasket, so that the universality of the method is improved;
2. residual compressive stress can be obtained on both sides of the thin-wall structure only through single-side laser shot peening strengthening, so that the applicability to strengthening of complex structures is improved;
3. the knife edge test piece constrained at two sides concentrates the maximum deformation of the laser shot peening strengthened test piece on the knife edge, so that the measurement is convenient, and the processing difficulty and the experiment cost are reduced by a single-side bolt tightening mode;
4. the common thin-wall structural material is TC4 or TC17 titanium alloy, and the optimal spot size is determined by experiments without repeating the characteristic thickness and the corresponding material of the obtained optimal spot size;
5. those skilled in the art generally recognize that spot size only affects the efficiency of laser peening, and optimization of process parameters is often done by varying the pulse energy. The invention determines the non-deformable balance point by reducing the size of the light spot, and solves the technical problem that the light spot with the diameter of 4mm can not find the non-deformable balance point by changing the pulse energy.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a schematic diagram of a knife edge test piece and a shot blasting path measurement path provided by the invention;
FIG. 2 is a top view of a knife edge test piece used in the present invention;
FIG. 3 is a side view of a knife-edge test piece used in the present invention;
FIG. 4 shows that the thickness of TC4 titanium alloy test piece of 0.5mm in the invention is 7.96GW/cm2A relation curve of deformation and spot size after power density laser shot peening;
FIG. 5 shows that the thickness of TC4 titanium alloy test piece of 0.5mm in the invention is 7.96GW/cm2A relation curve of residual stress and spot size after power density laser shot peening;
FIG. 6 is a graph of the optimal spot size versus impact point thickness in the present invention;
FIG. 7 is a schematic view of the spot size and laser peening path of the present invention;
in the figure: 1. light spots; 2. a shot blasting path; 3. a shot blasting region; 4. pressing a plate; 5. a bolt; 6. a nut; 7. a deformation measurement path; 8. a first step portion; 9. a specimen body.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.
Fig. 1 is a schematic diagram of a knife edge test piece and a shot blasting path measurement path provided by the invention, the knife edge test piece comprises a test piece main body 9 and a first step part 8 integrally formed with the test piece main body 9, two side surfaces of the test piece main body 9 are respectively fixedly provided with a pressing plate 4 through a bolt 5 and a nut 6, the upper surface of the pressing plate 4 is flush with the upper surface of the first step part 8 to form a second step part, the thickness of the first step part 8 is 3-4 times of that of the test piece main body 9, and the two step parts ensure that the maximum deformation point of the knife edge test piece is at a knife tip without a step surface.
The shot blasting area 3 is close to the edge end point, the shot blasting path 2 is from inside to outside, and the shape of the light spot 1 is circular. And measuring the edge test piece before and after shot peening according to the deformation measuring path 7, and obtaining the end displacement by taking the step surface as a reference. The embodiment of the device aims to realize that the thin-wall structure is subjected to single-side laser shot peening strengthening, and the residual compressive stress on two sides of a workpiece is ensured, and meanwhile, the workpiece is hardly deformed.
Fig. 2 to 3 are schematic structural diagrams of a knife edge test piece used in the invention, the test piece is a thin-wall test piece with uniform thickness and with step bodies on two sides, the knife edge thickness selects a single characteristic thickness value, the step surface is used as a boundary constraint and measurement reference, and the height of the step surface is 3 to 4 times greater than that of the knife edge part.
The workflow of the example is as follows:
step 1: and (3) carrying out thickness analysis on the three-dimensional model of the workpiece by UG software, uniformly selecting 100 points on the surface of the workpiece to obtain 100 thickness values, and screening out the maximum value, the minimum value and the value with the highest occurrence frequency as three characteristic thickness values (such as 0.4mm, 0.5mm and 0.6 mm).
Step 2: three thickness knife edge test pieces were prepared, 10 each. For one of the test piece sets with a thickness (e.g., 0.5mm), the thickness is constant (e.g., 7.96 GW/cm)2) Under the condition of the pulse power density, the diameter of a through hole of the special diaphragm is changed, the test piece is subjected to laser shot blasting reinforcement by using four spot sizes (such as the diameters of 0.6mm, 0.8mm, 1.0mm and 1.2mm) to obtain corresponding deformation values, the corresponding deformation values are connected into a curve, and the intersection point of the curve and a zero displacement line is the optimal spot size (such as the diameter of 1.03mm) under the thickness, as shown in fig. 4. The residual stress measurements on both sides of the knife-edge test piece after single-sided laser peening with different spot sizes are shown in fig. 5.
The above process is repeated for two additional test piece sets of thickness (e.g., 0.4mm and 0.6mm) to obtain two additional corresponding optimal spot size values (e.g., 0.79mm and 1.25mm diameters).
And step 3: the three characteristic thickness values and the corresponding optimal spot size are fit to a curve d ═ f (t), as shown in fig. 6. And performing single-side laser shot peening on all the strengthened regions according to the optimal spot sizes corresponding to different thickness values, as shown in fig. 7.
Wherein d is the optimal spot size, and t is the thickness value of the impact point.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.
Claims (4)
1. A single-side laser shot peening strengthening method of a thin-wall structural member is characterized by comprising the following steps:
s1, performing thickness analysis on the thin-wall structural part, and screening N characteristic thickness values;
s2, determining the optimal spot size of each thickness of the thin-wall structural member; the method for determining the optimal spot size comprises the following steps: selecting a knife edge test piece with a single thickness, performing unilateral laser shot peening strengthening of different spot sizes, and obtaining a displacement change curve of the end part of the knife edge test piece according to the laser shot peening strengthening of different spot sizes, wherein the intersection point of the change curve and a zero displacement line is the optimal spot size corresponding to the thickness;
s3, determining a laser shot blasting path of the thin-wall structural member;
s4, performing laser peening on the thin-wall structural member by the laser peening path of the step S3;
when the thin-wall structural part is an equal-thickness thin-wall structural part, N is 1; when the thin-wall structural part is a variable-thickness thin-wall structural part, N is more than or equal to 2.
2. The method of single-sided laser peening strengthening of a thin-walled structural member of claim 1, wherein the thickness analysis method is: and (3) performing thickness analysis on the three-dimensional digital model part of the thin-wall structural part or performing thickness measurement on the solid part by using a thickness gauge.
3. The method for single-sided laser peening strengthening of a thin-walled structural member as claimed in claim 1, wherein the knife-edge test piece includes a test piece main body and a first step portion integrally formed with the test piece main body, a pressing plate is provided on each of both side surfaces of the test piece main body, an upper surface of the pressing plate is flush with an upper surface of the first step portion to form a second step portion, and a thickness of the first step portion is 3 to 4 times of a thickness of the test piece main body.
4. The method for single-sided laser peening strengthening of a thin-walled structural member according to claim 1, wherein the laser peening path is determined by:
and fitting the N characteristic thickness values and the corresponding optimal spot sizes into a curve d (f) (t), and performing single-side laser shot peening strengthening on all strengthening areas according to the optimal spot sizes corresponding to different thickness values, wherein d is the optimal spot size, and t is the thickness value of an impact point.
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