Gear surface laser strengthening method, gear and laser strengthening device

Abstract

The invention relates to the technical field of material strengthening treatment, in particular to a gear surface laser strengthening method, a gear and a laser strengthening device. The method comprises the following steps that an obtained gear to be strengthened is divided into a plurality of areas to be strengthened, and the areas at least comprise a first area to be strengthened with the deformation smaller than a preset threshold value and a second area to be strengthened with the deformation larger than the preset threshold value during laser shock strengthening under the same condition; the divided first to-be-strengthened area and the divided second to-be-strengthened area are subjected to laser shock strengthening separately according to a preset first parameter set and a preset second parameter set; wherein the preset parameters of the first parameter group and the second parameter group comprise laser energy, laser pulse width and laser spot parameters, and each parameter value of the first parameter group is correspondingly greater than each parameter value of the second parameter group; the gear surface is subjected to laser strengthening through the gear surface laser strengthening method, and uniformity regulation and control of gear surface residual stress can be achieved to a certain extent.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material strengthening treatment, in particular to a gear surface laser strengthening method, a gear and a laser strengthening device. BACKGROUND

[0002] Gear transmission has the characteristics of high efficiency, compact structure, reliable work and stable transmission ratio, and is widely used in the field of mechanical transmission. Fatigue failure of stress concentration position of gear is one of the main forms of gear failure. Fatigue problem seriously affects the transmission efficiency and service life of gear. Under the premise of not changing the material system and structure design, surface strengthening technology is often used to improve the stress concentration of gear surface layer and solve the fatigue problem. Laser shock peening technology performs well in this regard. The technology is to generate plasma by high-energy laser beam acting on the surface of the material, and to preform residual compressive stress in a deep range by the action of plasma shock wave force, so as to inhibit crack propagation and prolong the service life of gear.

[0003] The existing laser strengthening method generally only impacts the gear surface by high-energy laser for strengthening, but the gear after being strengthened by high-energy laser has a large deformation in some areas, which reduces the precision of the gear. SUMMARY

[0004] In view of the above shortcomings of the prior art, the purpose of the present application is to provide a gear surface laser strengthening method, a gear and a laser strengthening device. The gear surface laser strengthening method can reduce the deformation of the gear surface after laser strengthening, and further improve the problem of uneven distribution of residual stress on the gear surface layer.

[0005] To achieve the above-mentioned purpose and other related purposes, the present application provides a gear surface laser strengthening method, comprising:

[0006] The obtained gear to be strengthened is divided into a plurality of regions to be strengthened, at least including a first region to be strengthened with a deformation less than a preset threshold value and a second region to be strengthened with a deformation greater than or equal to the preset threshold value under the same condition of laser shock peening;

[0007] The first region to be strengthened and the second region to be strengthened are respectively subjected to laser shock peening according to the first parameter group and the second parameter group;

[0008] The parameters of the first parameter group and the second parameter group include laser energy, laser pulse width and laser spot parameters, the parameter values of the first parameter group are all greater than the parameter values of the second parameter group, the laser energy of the first parameter group is in the order of joule, and the laser energy of the second parameter group is in the order of millijoule.

[0009] As an embodiment of the present application, the step of dividing the obtained gear to be strengthened into a plurality of regions to be strengthened at least includes a first region to be strengthened, in which the deformation is less than a preset threshold value, and a second region to be strengthened, in which the deformation is greater than the preset threshold value, when laser shock peening is performed under the same conditions,

[0010] The first region to be strengthened is a root region of the gear to be strengthened, and the second region to be strengthened is a tooth surface region of the gear to be strengthened and an edge region of the gear to be strengthened.

[0011] As an embodiment of the present application, in the step of performing laser shock peening on the divided first region to be strengthened and second region to be strengthened according to a preset first parameter group and a preset second parameter group, respectively, the values of some parameters in the first parameter group or the second parameter group are determined by at least one of the following steps:

[0012] The laser power density is determined according to the material properties of the gear;

[0013] The laser spot size for peening the root region is determined according to the shape and size of the root fillet region;

[0014] The laser energy is compensated according to the spot distortion degree of the tooth surface region to be peened, so that the power density of the tooth surface region to be peened is constant in each laser peening.

[0015] As an embodiment of the present application, in the step of performing laser shock peening on the divided first region to be strengthened and second region to be strengthened according to a preset first parameter group and a preset second parameter group, respectively:

[0016] The laser energy value of the first parameter group is greater than 1 J, the laser pulse width value is greater than 15 ns, and the laser spot diameter is greater than 1 mm; the laser energy value of the second parameter group is less than 100 mJ, the laser pulse width value is less than 10 ns, and the laser spot diameter is less than 0.5 mm.

[0017] As an embodiment of the present application, in the step of performing laser shock peening on the divided first region to be strengthened and second region to be strengthened according to a preset first parameter group and a preset second parameter group, respectively:

[0018] The laser energy value of the first parameter group ranges from 5 J to 12 J, the laser pulse width value ranges from 18 ns to 20 ns, and the laser spot diameter ranges from 2 mm to 5 mm;

[0019] The laser energy value of the second parameter group ranges from 30 mJ to 100 mJ, the laser pulse width value ranges from 8 ns to 10 ns, and the laser spot diameter ranges from 0.3 mm to 0.5 mm.

[0020] As an embodiment of the present application, the step of performing laser shock peening on the divided first and second to-be-strengthened regions according to the preset first and second parameter sets respectively further comprises the following steps:

[0021] The first to-be-strengthened region is subjected to shock peening according to a laser wavelength of 1064 nm;

[0022] The second to-be-strengthened region is subjected to shock peening according to a laser wavelength of 532 nm;

[0023] And / or the first and second to-be-strengthened regions are subjected to shock peening according to an overlap rate in the range of 50% to 80%.

[0024] As an embodiment of the present application, the step of performing laser shock peening on the divided first and second to-be-strengthened regions according to the preset first and second parameter sets respectively further comprises the following steps:

[0025] During the laser shock peening process on the to-be-strengthened region, the surface of the to-be-strengthened region is free of an absorption protective layer, and a constraint layer is formed on the surface of the to-be-strengthened region.

[0026] As an embodiment of the present application, the step of performing laser shock peening on the divided first and second to-be-strengthened regions according to the preset first and second parameter sets respectively further comprises the following steps:

[0027] Obtaining the profile parameters of the to-be-strengthened gear;

[0028] Determining the incidence angle of laser on different to-be-strengthened regions according to the profile parameters of the to-be-strengthened gear;

[0029] Wherein, the to-be-strengthened root region is strengthened by means of laser vertical impact; the to-be-strengthened tooth surface region and the to-be-strengthened edge region are strengthened by means of laser oblique impact, and interference is not generated.

[0030] To achieve the above object and other related objects, the present application provides a gear manufactured by the gear surface laser strengthening method.

[0031] To achieve the above object and other related objects, the present application provides a laser strengthening device comprising a memory and a processor, wherein the memory stores a computer program, and the processor invokes the computer program in the memory to implement the gear surface laser strengthening method.

[0032] In summary, the method is based on the deformation sensitivity of different regions of the gear during laser shock peening, and the J-level (J-level) and mJ-level laser peening processes are used for different regions, which are fundamentally different in principle, equipment and effect, rather than simply adjusting the parameters of the same process:

[0033] For deformation sensitive regions (such as tooth surface and edge), an mJ-level laser peening process is used. This process is based on the principle of laser and material interaction with small energy and small spot, and uses a special device with mJ-level energy output. The strengthening influence layer is relatively shallow, but it can form residual compressive stress near the surface, which is not less than or even higher than that of the J-level strengthening. At the same time, due to the shallow influence layer, the deformation during laser shock can be effectively inhibited, and the size deviation of the easily deformed region can be significantly reduced.

[0034] For deformation insensitive regions (such as tooth root), a J-level laser peening process is used. This process is based on large energy and large spot laser shock, and uses a special device with J-level energy output, which can significantly enhance the plastic deformation effect on the material inside, form a super-deep residual compressive stress layer, and effectively improve the bending fatigue limit and reduce the crack propagation rate of the tooth root region.

[0035] Therefore, by differentiating the selection of two essentially different strengthening processes, the size deviation of the deformation sensitive region is effectively reduced under the premise of ensuring the strengthening effect of the residual compressive stress near the surface of the gear (without sacrificing or even improving), rather than simply reducing the laser energy parameters (such as reducing from 6J to 3J) to sacrifice the surface residual compressive stress in exchange for deformation reduction. The uniformity of the surface residual compressive stress distribution of the gear is fundamentally improved, and the strengthening effect and size precision are considered. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0037] Figure 1 The flow chart of the gear surface laser peening method in an embodiment of the present application;

[0038] Figure 2 The schematic diagram of laser shock peening on the tooth root region according to the first parameter set in an embodiment of the present application;

[0039] Figure 3 The schematic diagram of laser shock peening on the tooth surface region and / or edge region according to the second parameter set in an embodiment of the present application;

[0040] Figure 4 Figure 6 shows the test results of the deformation of each gear after the gears 2# and 3# are respectively strengthened according to the corresponding parameter sets in an embodiment of the present application;

[0041] Figure 5 Figure 7 shows the residual stress distribution of each gear after the gears 2# and 3# are respectively strengthened according to the corresponding parameter sets in an embodiment of the present application;

[0042] Figure 6 Figure 8 shows the simulation stress distribution of the gear after the tooth root area and the tooth surface area of the gear 3# are respectively strengthened according to the corresponding parameter sets in an embodiment of the present application, but the edge area is not strengthened;

[0043] Figure 7 Figure 9 shows the simulation stress distribution of the gear 3# after the tooth root area, the tooth surface area and the edge area of the gear 3# are respectively strengthened according to the corresponding parameter sets in an embodiment of the present application;

[0044] Element number explanation: the gear to be strengthened 10, the laser impact point 101, the tooth root area 11, the tooth surface area 12, the edge area 13, the water nozzle robot 2, the water constraint layer 21, the laser strengthening device 3, the reflecting mirror 31, the focusing mirror 31, the laser beam 33. DETAILED DESCRIPTION

[0045] The present application can also be embodied in a different specific form, and the various details of the application can be modified in various obvious ways without departing from the spirit of the application. It should be noted that the following examples and features in the examples can be combined with each other in the case of no conflict. It should also be understood that the terms used in the embodiments of the present application are used to describe specific specific embodiments, but not to limit the protection scope of the present application. The test methods in the following examples are not specified, and are usually carried out according to the conventional conditions or the conditions recommended by the manufacturers.

[0046] When the embodiments give numerical ranges, it should be understood that, unless otherwise stated by the present application, each numerical range of two endpoints and any numerical value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present application are used by the skilled person in the art and the description of the present application, and any method, equipment and material of the prior art similar or equivalent to the method, equipment and material described in the embodiments of the present application can be used to realize the present application.

[0047] Following, the advantages and effects of the present application can be easily understood by persons skilled in the art from the disclosure of this description. The present application can also be implemented or applied by other different specific embodiments, and the details in the description can be modified or changed based on different views and applications without departing from the spirit of the present application.

[0048] Please refer to Figures 1-7 It is to be noted that the drawings provided in the embodiments only schematically illustrate the basic concepts of the present application, and the drawings only show the components related to the present application rather than the number, shape and size of the components during actual implementation. The actual implementation of each component can be arbitrarily changed in terms of shape, number and ratio, and the component layout can also be more complex.

[0049] The residual compressive stress generated by laser shock peening is achieved by plastic deformation caused by the propagation of plasma shock waves in the material. Laser pulse width, spot diameter, etc. will affect the propagation distance of the shock wave, thereby affecting the depth of the residual compressive stress layer. Under the same power density, the longer the pulse width, the longer the laser acts on the surface of the metal material, the longer the propagation distance of the shock wave, and the deeper the residual compressive stress; the larger the spot diameter, the smaller the attenuation rate of the shock wave generated when propagating in the material, the greater the propagation distance and the depth of the residual compressive stress layer. However, in the process of laser shock peening of the gear, a deeper affected layer will bring a larger deformation, so that the surface layer residual stress distribution is uneven after subsequent grinding, and due to the influence of the gear structure, the deformation degree of the gear tooth surface area 12 is more than twice that of the gear root area 11 after high-energy strengthening.

[0050] Before the improvement of the present case, the traditional laser shock peening technology often uses a large energy (>1 J), a large spot (>1 mm), and a long pulse width (>15 ns) strengthening process to strengthen the gear root area 11 and the gear tooth surface area 12, to generate residual compressive stress and improve the bending fatigue resistance and contact fatigue resistance of the gear. However, the surface layer residual compressive stress distribution of the gear is not uniform after the process, on the one hand, the gear deforms greatly after the large energy process, especially in the gear tooth surface area 12, and the deformation degree often exceeds the size tolerance range. At the same time, due to the complex structure of the gear, it is difficult to apply the absorbing protective layer during the laser shock peening process, and the subsequent grinding process needs to be carried out without the absorbing protective layer. The gear deformation is too large, so that the grinding depth is inconsistent, resulting in uneven residual stress distribution; on the other hand, only the gear tooth surface area 12 and the gear root area 11 are strengthened, which causes tensile stress in the gear edge area 13 during the stress balancing process, and the bending fatigue cracks of the gear often occur in the edge area 13. The uneven stress distribution after strengthening seriously reduces the improvement effect of the fatigue resistance of the gear; it should be understood that the above content is a problem before the improvement of the present case, but it is not known and discovered by the public.

[0051] Based on the above problems, the present application provides a gear surface laser strengthening method combining large energy and small energy, so as to control the deformation problem caused by gear strengthening, and provides a perfect process flow including a gear edge area 13 supplementary strengthening process, so as to ensure the uniformity of gear surface layer residual stress regulation and improve the fatigue resistance of the gear.

[0052] As shown in Figures 1-3 The present application provides a gear surface laser strengthening method, comprising:

[0053] The obtained gear to be strengthened 10 is divided into a plurality of areas to be strengthened, at least including a first area to be strengthened with a deformation less than a preset threshold value and a second area to be strengthened with a deformation greater than or equal to the preset threshold value under the same condition of laser shock strengthening;

[0054] The first area to be strengthened and the second area to be strengthened are respectively subjected to laser shock strengthening according to a preset first parameter group and a preset second parameter group;

[0055] The parameters of the preset first parameter group and the preset second parameter group include laser energy, laser pulse width and laser spot parameters, each parameter value of the first parameter group is greater than each parameter value of the second parameter group, the laser energy of the first parameter group is in the order of joule, and the laser energy of the second parameter group is in the order of millijoule.

[0056] It should be noted that the partitioned reinforcement is implemented according to the deformation sensitivity difference of different regions of the gear, and not only the first to be reinforced region with a deformation less than a preset threshold, the second to be reinforced region with a deformation greater than the preset threshold, the third to be reinforced region, the fourth to be reinforced region or the fifth to be reinforced region with a deformation between the first to be reinforced region and the second to be reinforced region, the sixth to be reinforced region with a deformation less than the first to be reinforced region and the seventh to be reinforced region with a deformation greater than the second to be reinforced region can be divided. Among them, the laser shock peening under the same condition refers to the deformation of each position of the gear under laser shock when the initial process parameters are consistent (such as uniformly using energy 5J, spot 3mm, pulse width 15ns). The deformation is measured by finite element simulation or pre-experiment. The preset threshold can be set according to the gear accuracy grade, for example, 10%-80% of the size tolerance. The first to be reinforced region corresponds to the regions such as the gear root, the second to be reinforced region corresponds to the regions such as the tooth surface, the edge, the edge chamfer and the like which are easy to deform, the first parameter group (large parameter) is suitable for the first to be reinforced region (gear root), and a combination of high energy (>5J), long pulse width (>15ns) and large spot (>2mm) is adopted; the second parameter group (small parameter) is suitable for the second to be reinforced region (tooth surface / edge), and a combination of low energy (<1J), short pulse width (<10ns) and small spot (<1mm) is adopted. The "each parameter value corresponds to greater than" in the parameter group refers to the independent satisfaction of the size relationship of energy, pulse width and spot (such as energy E1>E2, pulse width τ1>τ2, spot d1>d2), and the specific values can be determined by material constitutive model or orthogonal test optimization.

[0057] There are essential differences between millijoule-level laser strengthening and joule-level laser strengthening in core process parameters, action principle, equipment adaptation and strengthening effect. The joule-level laser strengthening generally adopts process parameters of energy >1J, pulse width >15ns, spot diameter >1mm and wavelength 1064nm, and a special laser equipment adapted to the wavelength. The principle is to make the plasma shock wave propagate to the deep layer of the material by means of the long action time of long pulse width laser and the low attenuation characteristics of the shock wave to the large spot, and then form a relatively deep residual compressive stress layer, which can effectively improve the bending fatigue resistance of the deformation insensitive regions such as gear root, but easily lead to large deformation of the gear (especially the tooth surface); while the millijoule-level laser strengthening generally adopts process parameters of energy <100mJ, pulse width <10ns, spot diameter <0.5mm and wavelength 532nm, and a special laser equipment adapted to the wavelength. Although the propagation distance of the shock wave is limited due to the low energy level and short pulse width, the strengthening influence layer is shallow, but through the control of the same power density as the joule-level process, a residual compressive stress peak not less than or even higher than the joule-level can be formed in the near surface of the material, and the gear deformation can be greatly reduced, which not only meets the strengthening needs of the deformation sensitive regions such as the tooth surface, but also can precisely cover the edge chamfer size by means of the small spot, avoiding the collapse of the edge and improving the stress concentration.

[0058] The conventional gear laser shock peening adopts a single parameter, and the residual compressive stress layer is shallow in the tooth root high load area due to insufficient energy, and excessive deformation is caused in the thin wall area of the tooth surface due to excessive energy. The method divides the to-be-strengthened gear 10 into multiple to-be-strengthened areas, and differentiates the high deformation risk area (tooth surface) and the low deformation risk area (tooth root) for strengthening, thereby avoiding performance imbalance caused by the same parameters.

[0059] As shown in Figures 1-3 As an optional embodiment of the present application, the step of dividing the obtained to-be-strengthened gear 10 into multiple to-be-strengthened areas at least includes the steps of:

[0060] The first to-be-strengthened area includes the tooth root area 11 of the to-be-strengthened gear 10; and the second to-be-strengthened area includes the tooth surface area 12 of the to-be-strengthened gear 10 and the edge area 13 of the to-be-strengthened gear 10.

[0061] It should be noted that the first to-be-strengthened area (tooth root area 11) refers to the maximum bending stress action area of the gear under load, which covers the tooth root fillet and the adjacent transition curved surface; for example, it is divided according to the high strain gradient area determined by the tooth root stress concentration coefficient, the statistical distribution of bending fatigue crack initiation position, and finite element analysis. In addition, the tooth root area 11 can also be extended to the area below the tooth root by 1 / 4 tooth height or other areas with smaller deformation; the second to-be-strengthened area (tooth surface and edge area 13) includes the tooth surface contact stress action zone and the tooth end edge stress balance zone. The tooth surface area 12 covers the envelope surface of the meshing point trajectory, and the edge area 13 refers to the chamfer transition zone at both ends of the tooth width direction. In addition, the tooth surface can also be strengthened in zones (node area / tooth top area with different parameters); the edge can also be strengthened in multiple layers (chamfer surface + edge line double path).

[0062] As shown in Figures 1-3 As an optional embodiment of the present application, in the step of differentiating the first to-be-strengthened area and the second to-be-strengthened area according to the preset first parameter group and the second parameter group for laser shock peening, the following at least one step is used to determine the parameter values in the preset first parameter group or the second parameter group:

[0063] Determine the laser power density according to the material properties of the gear;

[0064] Determine the laser spot size for impact strengthening the tooth root area 11 according to the shape and size of the tooth root area 11 (tooth root fillet area);

[0065] According to the spot distortion degree of the impact strengthened tooth surface area 12, compensate the laser energy so that the power density of each laser impact strengthening tooth surface area 12 is unchanged.

[0066] It should be noted that the tooth surface area 12 and the edge area 13 are generally inclined to impact, and the laser inclination angle is minimized based on the criterion of no interference. The energy value adjustment of the tooth surface area 12 is aimed at the spot elliptical phenomenon caused by inclined impact, and the actual power density is maintained constant through energy compensation. The compensation can be realized through online monitoring of the spot morphology or pre-stored angle-energy mapping table. The present case improves the stress continuity of the tooth root, makes the residual compressive stress distribution of the fillet area uniform, avoids the initiation of bending fatigue cracks caused by stress fault, improves the stability of the tooth surface strengthening, controls the stress distribution difference under different inclination angles within a predetermined range, solves the problem of uneven strengthening layer depth caused by angle change in traditional process, and eliminates the stress concentration in the edge line area through edge strengthening, thereby greatly improving the fatigue life.

[0067] As shown in Figures 1-3 As an optional embodiment of the present case, the first and second to-be-strengthened areas are respectively subjected to laser impact strengthening according to the first and second preset parameter groups in the steps of:

[0068] The laser energy value of the first parameter group is greater than 1 J, the laser pulse width value is greater than 15 ns, and the laser spot diameter is greater than 1 mm; the laser energy value of the second parameter group is less than 100 mJ, the laser pulse width value is less than 10 ns, and the laser spot diameter is less than 0.5 mm.

[0069] It should be noted that the first parameter group is adapted to the strengthening requirement of the tooth root area 11, and its large energy and long pulse width characteristics drive the shock wave to propagate to the deep layer. The second parameter group is aimed at the tooth surface and edge area 13, and small energy and short pulse width inhibit mechanical deformation. The above-mentioned parameter limitation of the present case breaks through the technical bottleneck of the traditional technology. For example, the deformation amount of the tooth surface caused by the traditional single parameter is significantly greater than that of the tooth root (> 2 times), and the integrity of the stress layer is destroyed after grinding; the structure collapse of the edge area 13 caused by excessive impact strength; the above-mentioned parameter limitation of the present case has the following effects. The second parameter group makes the deformation amount of the tooth surface area 12 converge to the deformation level of the tooth root, improves the overall deformation uniformity, and guarantees the machining precision in the subsequent process. In addition, the laser strengthening corresponding to the second parameter group with small spot and small energy can avoid the collapse of the edge area 13.

[0070] As shown in Figures 1-3 As an optional embodiment of the present case, the first and second to-be-strengthened areas are respectively subjected to laser impact strengthening according to the first and second preset parameter groups in the steps of:

[0071] The laser energy value of the first parameter group is in the range of 5-12 J, the laser pulse width value is in the range of 18-20 ns, and the laser spot diameter is in the range of 2-5 mm;

[0072] The laser energy value range of the second parameter group is 30-100 mJ, the laser pulse width value range is 8-10 ns, and the laser spot diameter range is 0.3-0.5 mm.

[0073] It should be noted that the first parameter group (5-12 J, 18-20 ns, 2-5 mm) is aimed at the deep reinforcement requirement of the root area 11, and the lower limit of the energy 5 J ensures that the shock wave breaks through the material yield threshold, and the upper limit 12 J inhibits excessive plastic deformation; the pulse width 18-20 ns matches the stress wave propagation attenuation period in the gear steel; the spot 2-5 mm covers the tooth root fillet curvature; the power density ranges corresponding to the energy, spot and pulse width of the two parameter groups correspond to the lower limit of the threshold of plastic deformation of the material and the upper limit of the threshold of avoiding excessive deformation, which are applicable to the first parameter group and the second parameter group, and the parameter power density of the first parameter group and the second parameter group is close.

[0074] As shown in Figures 1-3 As an optional embodiment of the present case, the first and second to-be-reinforced areas divided according to the preset first and second parameter groups in the step of laser shock peening respectively further include the following steps:

[0075] The first to-be-reinforced area is subjected to shock reinforcement according to a laser wavelength of 1064 nm;

[0076] The second to-be-reinforced area is subjected to shock reinforcement according to a laser wavelength of 532 nm;

[0077] And / or the first and second to-be-reinforced areas are subjected to shock reinforcement according to an overlap rate in the range of 50%-80%.

[0078] It should be noted that the first to-be-reinforced area corresponds to the gear tooth root area 11, and is subjected to reinforcement by using a 1064 nm wavelength laser. It should be understood that other near-infrared wavelength (such as 1054 nm, 1070 nm) solid-state lasers of the same type can also be used as long as the physical mechanism of deep plastic deformation is met. The second to-be-reinforced area covers the tooth surface and edge area 13, and is subjected to reinforcement by using a 532 nm wavelength laser (green light band). It should be understood that visible light band lasers (such as 515 nm, 355 nm) can also be used. The overlap rate 50%-80% is a key parameter for controlling the uniformity of laser impact coverage. This range ensures the continuity of the residual stress field through overlapping scanning paths, the lower limit avoids non-reinforced gaps, and the upper limit prevents excessive deformation. The present case can implement a differentiated overlap rate in different zones (such as 70%-80% for the tooth root and 50%-60% for the tooth surface), and can also implement a dynamic adjustable overlap rate system.

[0079] As shown in Figures 1-3As shown, in an optional embodiment of this case, the step of distinguishing and performing laser shock strengthening on the first and second regions to be strengthened according to preset first and second parameter groups respectively further includes the following steps:

[0080] In the laser shock strengthening process of the area to be strengthened, the surface of the area to be strengthened has no absorption protective layer, and a constraint layer is formed on the surface of the area to be strengthened.

[0081] It should be noted that, generally, the outer side of the area to be strengthened in this case is without an absorbent protective layer. Of course, an absorbent protective layer can be added if there is a special need. In this case, "no absorbent protective layer" means that the surface of the gear tooth root, tooth surface, and edge area 13 is not coated with traditional black tape / black paint / aluminum foil, etc. The constraint layer formed on the surface of the area to be strengthened means that it continuously covers the surface of the laser action area. The shock wave pressure is increased through inertial constraint. For example, a water constraint layer 21 is formed by spraying a water curtain onto the area to be strengthened by a water nozzle robot 2. In this case, because there is no absorbent protective layer, the bonding gap problem in the area of ​​abrupt curvature change of the tooth surface is eliminated, avoiding uneven energy absorption caused by local film peeling, and ensuring the continuity of residual stress distribution from the source. The water constraint layer 21 can flow and cover the tooth root transition surface to ensure the uniformity of shock wave pressure.

[0082] like Figures 1-3 As shown, in an optional embodiment of this case, before the step of distinguishing and performing laser shock strengthening on the divided first and second regions to be strengthened according to preset first and second parameter groups respectively, the following steps are also included:

[0083] Obtain the profile parameters of the gear 10 to be strengthened;

[0084] The incident angle of the laser on different areas to be strengthened is determined based on the profile parameters of the gear 10 to be strengthened.

[0085] Among them, the tooth root region 11 to be strengthened is strengthened by vertical laser impact; the tooth surface region 12 and the edge region 13 to be strengthened are strengthened by inclined laser impact, with the aim of not causing interference.

[0086] It should be noted that the profile parameters such as gear modulus, tooth height, pressure angle and other geometric parameters, or the three-dimensional model of the gear; the minimum non-interference incident angle is calculated by the gear modulus, tooth height, pressure angle and other geometric parameters, in addition, the tooth profile topology can also be reconstructed by three-dimensional point cloud scanning; or parameterized template matching (such as ISO1328 standard tooth profile library), or machine learning to predict the interference critical angle. The tooth root region 11 vertical impact refers to the angle between the laser beam axis and the tooth root surface normal ≤ 5°, or dynamic normal tracking (real-time pose adjustment of six-axis robot), or curved surface adaptive clamp (gear rotation around the tooth root curvature center) for dynamic adjustment. The tooth surface / edge oblique impact is based on the premise of avoiding interference, that is, the laser path avoids the obstruction of adjacent teeth.

[0087] In the present case, the tooth root vertical impact can improve the uniformity of the tooth root deep layer stress distribution and improve the bending fatigue limit; the tooth surface oblique impact maintains the power density stability under the premise of avoiding obstacles, effectively improves the tooth surface near-surface stress uniformity, and prolongs the contact fatigue life; the incident angle precalculation method based on the profile parameters tends to zero interference risk, and the equipment collision rate is reduced.

[0088] The present application provides a gear manufactured by the gear surface laser strengthening method, so that the gear manufactured by the method is also within the protection scope of the present application.

[0089] The present application provides a laser strengthening device, comprising a memory and a processor, the memory stores a computer program, and the processor calls the computer program in the memory to realize the gear surface laser strengthening method according to any one of claims 1 to 8.

[0090] The memory includes at least one type of readable storage medium, including flash memory, mobile hard disk, multimedia card, card-type memory (such as SD or DX memory, etc.), magnetic memory, disk, optical disk, etc. The memory can be an internal storage unit of an electronic device in some embodiments, such as a mobile hard disk of the electronic device. The memory can also be an external storage device of an electronic device in other embodiments, such as a plug-in mobile hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the electronic device. Further, the memory can include both the internal storage unit and the external storage device of the electronic device. The memory can be used not only to store application software and various data installed on the electronic device, such as the code of the gear surface laser strengthening method program, but also to temporarily store data that has been output or will be output.

[0091] The processor in some embodiments can be composed of integrated circuits, for example, can be composed of a single packaged integrated circuit, or can be composed of multiple packaged integrated circuits of the same function or different functions, including one or more combinations of central processing units (CPUs), microprocessors, digital processing chips, graphics processors, and various control chips. The processor is the control unit of the electronic device, which connects various components of the entire electronic device through various interfaces and lines, executes programs or modules stored in the memory (such as executing the gear surface laser strengthening method program), and calls data stored in the memory to execute various functions of the electronic device and process data.

[0092] The processor executes the operating system of the electronic device and various installed application programs. The processor executes the application programs to implement the steps in the above-mentioned gear surface laser strengthening method embodiments, such as Figure 1 The steps shown.

[0093] For example, the computer program can be divided into one or more modules, which are stored in the memory and executed by the processor to complete the present application. The one or more modules can be a series of computer program instruction segments that can complete a specific function, which are used to describe the execution process of the computer program in the electronic device.

[0094] Based on the purpose of improving the uniformity of gear surface layer residual stress regulation, the present application proposes a gear partition strengthening method. The tooth root area 11 position with small deformation is strengthened by large energy (>1J), large spot (>1mm), and long pulse width (>15ns) process to ensure the strengthening effect. The tooth surface area 12 position with large deformation is strengthened by small energy (<100mJ), small spot (<0.5mm), and short pulse width (<10ns) process to reduce deformation. At the same time, the edge area 13 position is supplemented by small energy (<100mJ), small spot (<0.5mm), and short pulse width (<10ns) process to improve the stress concentration of the edge area 13 region. At the same time, the small energy process can also avoid the collapse of the edge area 13 during impact.

[0095] Embodiment one:

[0096] Step one: obtain the three-dimensional model of the gear to be strengthened 10, determine the impact angle of the tooth root area 11, the tooth surface area 12, and the edge area 13, and avoid interference on the laser incidence path.

[0097] Step two: laser shock peening of the root area 11 according to a high-energy process, the constraint layer being water, without an absorbing protective layer; the peening parameters being: laser wavelength 1064 nm, pulse width 18-20 ns, laser energy 5-12 J, spot diameter 2-5 mm, and overlap rate 50%-80%.

[0098] Step three: laser shock peening of the tooth surface area 12 using a low-energy process, the constraint layer being water, without an absorbing protective layer; the peening parameters of the low-energy process being: laser wavelength 532 nm, pulse width 8-10 ns, laser energy 30-100 mJ, spot diameter 0.3-0.5 mm, and overlap rate 50%-80%.

[0099] Step four: supplementary peening of the edge area 13 using a low-energy process, the constraint layer being water, without an absorbing protective layer; the peening parameters of the low-energy process being: laser wavelength 532 nm, pulse width 8-10 ns, laser energy 30-100 mJ, spot diameter 0.3-0.5 mm, and overlap rate 50%-80%.

[0100] Example two:

[0101] Step one: obtain a three-dimensional model of the gear 10 to be peened, determine the laser incidence angle according to the gear shape and size, vertically impact the root area 11, and obliquely impact the tooth surface area 12 and the edge area 13, and minimize the laser incidence angle based on the criterion of no interference.

[0102] Step two: use a laser shock peening device with a wavelength of 1064 nm and a pulse width of 18-20 ns to perform high-energy laser shock peening on the root area 11; the process parameter determination process includes: determining the laser power density, overlap rate, and peening times based on the material properties of the gear 10 to be peened, and using a flat sample of the same material to perform a laser peening pre-experiment, and optimizing the process parameters based on the residual stress test results; determine the spot size based on the shape and size of the root area 11, and minimize the spot distortion at the fillet position of the root area 11; the parameter range is: laser energy 5-12 J, spot diameter 2-5 mm, and overlap rate 50%-80%; based on the process parameters determined by the above method, no absorbing protective layer is pasted, and laser shock peening is performed on the root area 11.

[0103] Step three: the laser shock peening equipment with wavelength 532 nm and pulse width 8-10 ns is used to perform small energy laser shock peening treatment on the tooth surface area 12, and the process parameter determination method is the same as that in step two, wherein the energy needs to be increased correspondingly to ensure that the power density remains unchanged due to the distortion of the light spot caused by the oblique impact; the parameter range is: laser energy 30-100 mJ, light spot diameter 0.3-0.5 mm, and overlap rate 50%-80%; according to the determined process parameters, no absorption protective layer is pasted, and the laser shock peening processing is performed on the tooth surface area 12.

[0104] Step four: the laser shock peening equipment with wavelength 532 nm and pulse width 8-10 ns is used to perform small energy laser shock peening treatment on the edge area 13, and the process parameter determination method is the same as that in step three, wherein the light spot size needs to be determined considering the chamfer size of the edge area 13 to ensure that the light spot can completely cover; the parameter range is: laser energy 30-100 mJ, light spot diameter 0.3-0.5 mm, and overlap rate 50%-80%; according to the determined process parameters, no absorption protective layer is pasted, and the laser shock peening processing is performed on the edge area 13.

[0105] As shown in Figures 4-7 , the effect verification is as follows:

[0106] Three 16Cr3NiWMoVNbE carburized gears are selected for laser shock peening test, wherein 1# gear is not subjected to laser shock peening, 2# gear is subjected to large energy strengthening process, and the strengthening parameters are: laser wavelength 1064 nm, pulse width 20 ns, laser energy 4 J, light spot diameter 2 mm, and overlap rate 75%. 3# gear is subjected to large / small energy partition strengthening process, the root area 11 is subjected to large energy process strengthening, and the strengthening parameters are consistent with those of 2# gear; the tooth surface area 12 is subjected to small energy process strengthening, and the power density is equal to that of the large energy process, and the strengthening parameters are: laser wavelength 532 nm, pulse width 10 ns, laser energy 80 mJ, light spot diameter 0.4 mm, and overlap rate 75%; the edge area 13 is subjected to small energy process strengthening, and the parameters are consistent with those of the tooth surface area 12. The deformation degree, hardness and residual stress distribution of 2# and 3# gears are compared as shown in Figures 4-5 . The results show that, compared with large energy strengthening, the deformation degree of the tooth surface area 12 after large / small energy partition strengthening process decreases by 58%, the deformation degrees of the root area 11 and the tooth surface area 12 are similar, and the overall deformation degree is uniform. The residual compressive stress influence layer of the root area 11 is relatively deep, which improves the bending fatigue performance of the gear; although the influence layer of the tooth surface area 12 is relatively shallow, the near-surface residual compressive stress peak value is relatively high, which improves the contact fatigue performance of the gear.

[0107] The stress distribution of the edge area 13 of 3# gear is simulated and analyzed, and the results are as follows: Figures 6-7As shown, it can be seen that the position of the edge region 13 is supplemented by impact strengthening, which can effectively improve the stress concentration of the edge region 13 and reduce the fatigue crack initiation.

[0108] The above embodiments only illustrate the principles and effects of the present application, and are not intended to limit the present application. Any modification or change made by any person skilled in the art without departing from the spirit and scope of the present application shall be covered by the claims of the present application.

Claims

1. A method of laser hardening a gear surface, characterized by, The method comprises the steps of: dividing the obtained gear to be strengthened into a plurality of regions to be strengthened, at least including a first region to be strengthened, in which the deformation is less than a preset threshold value, and a second region to be strengthened, in which the deformation is greater than or equal to the preset threshold value, when laser shock peening is performed under the same conditions; performing laser shock peening on the divided first region to be strengthened and the second region to be strengthened according to a preset first parameter group and a preset second parameter group, respectively; wherein the parameters of the preset first parameter group and the preset second parameter group each include laser energy, laser pulse width, and laser spot parameters, each parameter value of the first parameter group is greater than each parameter value of the second parameter group, and the laser energy of the first parameter group is in the joule level, and the laser energy of the second parameter group is in the millijoule level.

2. The gear surface laser hardening method according to claim 1, characterized in that, In the step of dividing the obtained gear to be strengthened into a plurality of regions to be strengthened, at least including a first region to be strengthened, in which the deformation is less than a preset threshold value, and a second region to be strengthened, in which the deformation is greater than or equal to the preset threshold value, when laser shock peening is performed under the same conditions, the first region to be strengthened includes a root region of the gear to be strengthened, and the second region to be strengthened includes a tooth surface region of the gear to be strengthened and an edge region of the gear to be strengthened.

3. The gear surface laser hardening method according to claim 2, characterized in that, In the step of performing laser shock peening on the divided first region to be strengthened and the second region to be strengthened according to a preset first parameter group and a preset second parameter group, respectively, the following at least one step is used to determine part of the parameter values in the preset first parameter group or the preset second parameter group: determining the laser power density according to the material properties of the gear; determining the laser spot size for the impact-strengthened root region according to the shape and size of the root fillet region; compensating for the laser energy according to the degree of spot distortion of the impact-strengthened tooth surface region, so that the power density of each laser impact on the tooth surface region is unchanged.

4. The gear surface laser strengthening method according to claim 1, characterized by, In the step of performing laser shock peening on the divided first region to be strengthened and the second region to be strengthened according to a preset first parameter group and a preset second parameter group, respectively: the laser energy value of the first parameter group is greater than 1 J, the laser pulse width value is greater than 15 ns, and the laser spot diameter is greater than 1 mm; the laser energy value of the second parameter group is less than 100 mJ, the laser pulse width value is less than 10 ns, and the laser spot diameter is less than 0.5 mm.

5. The gear surface laser strengthening method according to claim 1, characterized by, In the step of performing laser shock peening on the divided first region to be strengthened and the second region to be strengthened according to a preset first parameter group and a preset second parameter group, respectively: the laser energy value of the first parameter group ranges from 5 J to 12 J, the laser pulse width value ranges from 18 ns to 20 ns, and the laser spot diameter ranges from 2 mm to 5 mm; the laser energy value of the second parameter group ranges from 30 mJ to 100 mJ, the laser pulse width value ranges from 8 ns to 10 ns, and the laser spot diameter ranges from 0.3 mm to 0.5 mm.

6. The gear surface laser strengthening method according to claim 1, characterized by, In the step of performing laser shock peening on the divided first region to be strengthened and the second region to be strengthened according to a preset first parameter group and a preset second parameter group, respectively, the following steps are further included: performing impact strengthening on the first region to be strengthened according to a laser wavelength of 1064 nm; performing impact strengthening on the second region to be strengthened according to a laser wavelength of 532 nm; and / or the first and second areas to be strengthened are impact-strengthened according to a lap rate in the range of 50% to 80%.

7. The gear surface laser strengthening method according to claim 1, characterized by, The step of laser impact-strengthening the divided first and second areas to be strengthened according to the preset first and second parameter sets respectively further comprises the following steps: During the laser impact-strengthening process of the areas to be strengthened, the surface of the areas to be strengthened is free of an absorption protective layer, and a constraint layer is formed on the surface of the areas to be strengthened.

8. The gear surface laser strengthening method according to claim 1, characterized by, The step of laser impact-strengthening the divided first and second areas to be strengthened according to the preset first and second parameter sets respectively further comprises the following steps: Obtaining the profile parameters of the gear to be strengthened; Determining the incidence angle of the laser on different areas to be strengthened according to the profile parameters of the gear to be strengthened; The tooth root area to be strengthened is strengthened by laser vertical impact, and the tooth surface area and the edge area to be strengthened are strengthened by laser oblique impact, so as to not produce interference.

9. A gear wheel, characterized by The gear is manufactured by the gear surface laser strengthening method of any one of claims 1 to 8.

10. A laser strengthening apparatus, characterized by, A computer program product comprising a memory and a processor, wherein the memory stores a computer program, and the processor invokes the computer program in the memory to implement the gear surface laser strengthening method of any one of claims 1 to 8.

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