Shot peening strengthening quality evaluation method for few leaf springs

Abstract

The invention provides a shot peening strengthening quality evaluation method for few leaf springs. The shot peening strengthening quality evaluation method for the few leaf springs comprises the steps that first shot peening operation is conducted on the surfaces of at least two target leaf springs, and at least two primary shot peening leaf springs are obtained; performing residual stress detection on one of the primary shot blasting steel plate springs to obtain first residual stress field data information; second shot blasting operation is conducted on the surface of the other first shot blasting steel plate spring, and a second shot blasting steel plate spring is obtained; performing residual stress detection on the secondary shot peening steel plate spring to obtain second residual stress field data information; based on the first residual stress field data information and the second residual stress field data information, stress change data information of the target steel plate spring after the second shot blasting operation is determined; and when it is determined that the stress change data information meets the preset evaluation condition, it is determined that the shot peening strengthening quality of the target steel plate spring meets the requirement.

Description

Technical Field

[0001] The invention relates to the technical field of leaf springs, and in particular to a quality evaluation method for shot peening of a few leaf springs. Background Art

[0002] The development of automobile leaf springs has evolved from more leaf springs to fewer leaf springs to fewer leaf springs. Under the trend of lightweight automobiles, the design requirements have led to the development of automobile leaf spring steel towards high strength, high elastic resistance reduction, high fatigue life and high purity. At present, foreign automobile companies have used single-leaf leaf springs. Fewer leaf springs have higher reliability than more leaf springs. The shot peening process of leaf springs has a very large effect on their reliability. After shot peening, the surface layer of the fewer leaf springs is required to reach a higher compressive stress value, the transition from the surface to the maximum compressive stress is smooth, and the surface compressive stress is evenly distributed. This requires a composite shot peening process. The composite shot peening process can be achieved through multiple shot peening, but there is a lack of an effective evaluation method for whether the composite shot peening process can achieve the best shot peening effect. Summary of the invention

[0003] The main purpose of the present invention is to provide a method for evaluating the quality of shot peening of a few-piece leaf spring, so as to solve the problem in the prior art of lacking an effective evaluation method for whether the composite shot peening process can achieve the best shot peening effect.

[0004] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a method for evaluating the quality of shot peening of a small leaf spring is provided. The method for evaluating the quality of shot peening of a small leaf spring comprises: performing a first shot peening operation on the surface of at least two target leaf springs to obtain at least two first shot peened leaf springs; performing residual stress detection on one of the first shot peened leaf springs to obtain first residual stress field data information; performing a second shot peening operation on the surface of another first shot peened leaf spring to obtain a second shot peened leaf spring; performing residual stress detection on the second shot peened leaf spring to obtain second residual stress field data information; based on the first residual stress field data information and the second residual stress field data information, determining the stress change data information of the target leaf spring after the second shot peening operation; when it is determined that the stress change data information meets the preset evaluation conditions, determining that the shot peening quality of the target leaf spring meets the requirements.

[0005] Further, residual stress detection is performed on one of the shot peened leaf springs to obtain first residual stress field data information, including: residual stress detection is performed on the surface of the first target leaf spring to obtain first residual stress field data information, and the first residual stress field data information at least includes: a first surface residual compressive stress value, a first maximum residual compressive stress value, a depth value of the first maximum residual compressive stress from the surface, and a first residual compressive stress field depth value.

[0006] Furthermore, performing residual stress detection on one of the shot-peened leaf springs also includes: chemically corroding the surface of the shot-peened leaf spring using a stripping method to obtain a sub-surface of the target leaf spring; performing residual stress detection on the sub-surface of the first target leaf spring to obtain a first surface residual compressive stress value, and stopping the detection after the first surface residual compressive stress value is a positive value.

[0007] Furthermore, residual stress detection is performed on the secondary shot peening leaf spring to obtain second residual stress field data information, including: residual stress detection is performed on the surface of the secondary shot peening leaf spring to obtain second residual stress field data information, and the second residual stress field data information at least includes: a second surface residual compressive stress value, a second maximum residual compressive stress value, a depth value of the second maximum residual compressive stress from the surface, and a second residual compressive stress field depth value.

[0008] Furthermore, residual stress detection is performed on the secondary shot peened leaf spring, including: chemically corroding the surface of the secondary shot peened leaf spring using a stripping method to obtain a secondary surface of the target leaf spring; performing residual stress detection on the secondary surface of the secondary shot peened leaf spring to obtain a secondary surface residual compressive stress value, and stopping detection after the secondary surface residual compressive stress value is a positive value.

[0009] Further, based on the first residual stress field data information and the second residual stress field data information, the stress change data information of the target leaf spring after the second shot peening operation is determined, including: based on the first surface residual compressive stress value and the second surface residual compressive stress value, determining the surface residual compressive stress change data information of the stress change data information of the target leaf spring after the second shot peening operation, the surface residual compressive stress change data information is a value obtained by increasing the second surface residual compressive stress value compared to the first surface residual compressive stress value; based on half of the depth value of the first maximum residual compressive stress from the surface and half of the depth value of the second maximum residual compressive stress from the surface, determining 1 / 2Zc stress change data information of the stress change data information of the target leaf spring after the second shot peening operation, the 1 / 2Zc stress change data information is a value obtained by increasing the depth value of the second maximum residual compressive stress from the surface compared to the depth value of the first maximum residual compressive stress from the surface.

[0010] Further, when it is determined that the stress change data information satisfies preset evaluation conditions, it is determined that the shot peening quality of the target leaf spring meets the requirements, and the preset evaluation conditions include at least: a surface residual compressive stress index value, a 1 / 2Zc stress index value, where Zc is the depth of the maximum residual compressive stress from the surface, including: when it is determined that the surface residual compressive stress change data information is greater than or equal to the surface residual compressive stress index value, and the 1 / 2Zc stress change data information is greater than or equal to the 1 / 2Zc stress index value, the shot peening effect meets the requirements.

[0011] Furthermore, when it is determined that the stress change data information meets the preset evaluation conditions, it is determined that the shot peening quality of the target leaf spring meets the requirements, and then it also includes: when it is determined that the surface residual compressive stress change data information is less than the surface residual compressive stress index value, and the 1 / 2Zc stress change data information is less than the 1 / 2Zc stress index value, adjusting the intensity of the second shot peening.

[0012] Furthermore, a first shot peening operation is performed on the surface of at least two target leaf springs to obtain at least two single shot peened leaf springs, which includes: quenching, medium temperature tempering, and surface decarburization of the leaf spring sample to obtain the target leaf spring.

[0013] Further, when it is determined that the stress change data information satisfies the preset evaluation conditions, it is determined that the shot peening quality of the target leaf spring meets the requirements, which then includes: obtaining the strengthening process parameters of the first shot peening operation and the strengthening process parameters of the second shot peening operation; and detecting whether the surface roughness of the first shot peened leaf spring and the surface roughness of the second shot peened leaf spring meet the requirements.

[0014] By applying the technical solution of the present invention, the residual compressive stress on the surface of the leaf spring is increased through two shot peening processes. The residual compressive stress increases the fatigue fracture resistance and enhances the reliability. The two-step composite shot peening constrains the residual stress field data information, so that the residual compressive stress distribution from the surface to the maximum residual compressive stress point is uniform and gentle, so that the shot peening effect is optimized and the service life of the single leaf spring is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0016] Figure 1 A schematic flow chart of a first embodiment of a method for evaluating the quality of shot peening of a leaf spring with a small number of leaves according to the present invention is shown;

[0017] Figure 2 A schematic flow chart of a second embodiment of a method for evaluating the quality of shot peening of a leaf spring with a small number of leaves according to the present invention is shown. DETAILED DESCRIPTION

[0018] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0019] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0020] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0021] Now, exemplary embodiments according to the present application will be described in more detail with reference to the accompanying drawings. However, these exemplary embodiments may be implemented in a variety of different forms and should not be construed as being limited to the embodiments described herein. It should be understood that these embodiments are provided to make the disclosure of the present application thorough and complete, and to fully convey the concepts of these exemplary embodiments to those of ordinary skill in the art. In the accompanying drawings, for the sake of clarity, the thickness of the layers and regions may be enlarged, and the same reference numerals are used to represent the same devices, and thus their descriptions will be omitted.

[0022] It should be noted that shot peening is a process in which a high-speed shot stream is ejected onto the surface of a material and causes cyclic plastic deformation of the surface layer. After shot peening, a residual stress field is introduced into the surface and surface layer of the material and a plastic deformation structure is formed. A reasonable shot peening process can improve the life and reliability of leaf springs.

[0023] After the leaf spring is shot peened, the surface layer is required to reach a higher compressive stress value, the transition from the surface to the maximum compressive stress is gentle, and the surface compressive stress is evenly distributed. This requires a composite shot peening process. The first shot peening obtains a sufficiently high residual compressive stress and a sufficiently deep residual compressive stress field; the second shot peening adjusts and improves the residual compressive stress distribution from the surface of the outer layer to the peak value. The composite shot peening process can be achieved through multiple shot peening. This patent describes a residual stress field evaluation method that reasonably uses two shot peenings to achieve the best shot peening effect.

[0024] Combination Figure 1 As shown, according to a specific embodiment of the present invention, a method for evaluating the shot peening quality of a small number of leaf springs is provided.

[0025] Specifically, Figure 1 As shown in the figure, the quality evaluation method of shot peening of leaf springs includes:

[0026] Step S10: performing a first shot peening operation on the surfaces of at least two target leaf springs to obtain at least two first shot peened leaf springs.

[0027] Two leaf springs are prestressed and clamped on a fixture for the first pass of shot peening to obtain the first pass shot peening strength value of the single shot peening leaf spring. The effect of the first pass of shot peening is to make the maximum compressive stress reach the specified technical requirements through the appropriate shot peening intensity.

[0028] Among them, shot peening intensity is affected by factors including shot type, shot diameter and hardness, shot velocity and flow rate, spray angle and time, distance from nozzle to part surface, etc. Shot peening intensity is achieved through Almen test piece according to shot peening saturation test requirements.

[0029] It should be noted that the Almen test piece is a standard specimen used to characterize the effect of shot peening. The material is SAE1070 spring steel. When the test piece is impacted by a projectile, the surface layer undergoes plastic deformation, which causes the test piece to bend spherically toward the spray surface. The distance between the specific reference plane that cuts into the sphere and the highest point of the sphere is called the arc height. Saturation is defined as the earliest point reached on the curve. After exceeding this point, the increase in arc height will not exceed 10% when the strengthening time is doubled. The saturation curve is drawn based on a series of continuous shot strengthening of the Almen test piece fixed on the strengthening machine, the measured and recorded arc height values, and the location of the saturation point is confirmed. When the first strengthening time (T) is increased by 2 times (2T), the Almen arc height value increases by less than 10%. This means that the strengthening time to reach saturation = T. Saturation confirms the actual strength value obtained by strengthening a certain part of the part under specific machine settings.

[0030] Step S12: Perform residual stress detection on one of the shot peened leaf springs to obtain first residual stress field data information.

[0031] The above-mentioned first residual stress field data information at least includes: a first surface residual compressive stress value, a first maximum residual compressive stress value, a depth value of the first maximum residual compressive stress from the surface, and a first residual compressive stress field depth value.

[0032] Step S14: performing a second shot peening operation on the surface of another first shot peened leaf spring to obtain a second shot peened leaf spring.

[0033] The second shot peening operation is used to adjust the surface compressive stress distribution state to meet the optimal use conditions.

[0034] Step S16: Perform residual stress detection on the secondary shot peening leaf spring to obtain second residual stress field data information.

[0035] The above-mentioned second residual stress field data information at least includes: a second surface residual compressive stress value, a second maximum residual compressive stress value, a depth value of the second maximum residual compressive stress from the surface, and a second residual compressive stress field depth value.

[0036] Step S18: Based on the first residual stress field data information and the second residual stress field data information, determine the stress change data information of the target leaf spring after the second shot peening operation.

[0037] Step S20: When it is determined that the stress change data information satisfies the preset evaluation conditions, it is determined that the shot peening quality of the target leaf spring meets the requirements.

[0038] The residual compressive stress on the surface of the leaf spring is increased through two shot peening processes. The residual compressive stress increases the fatigue fracture resistance and enhances the reliability. The two-step composite shot peening constrains the residual stress field data information, making the residual compressive stress distribution from the surface to the maximum residual compressive stress point uniform and gentle, so that the shot peening effect is optimized and the service life of the single leaf spring is increased.

[0039] Further, step S12: performing residual stress detection on one of the shot peened leaf springs to obtain first residual stress field data information, including:

[0040] Step S121: Perform residual stress detection on the surface of the first target leaf spring to obtain first residual stress field data information, wherein the first residual stress field data information at least includes: a first surface residual compressive stress value, a first maximum residual compressive stress value, a depth value of the first maximum residual compressive stress from the surface, and a first residual compressive stress field depth value.

[0041] In step S121, the residual stress is specifically measured by the X-ray diffraction method, and samples are taken at the specified position for detection, and the residual stress is measured by the X-ray diffraction method. The principle is to use monochromatic X-rays to be incident on the crystal. If the X-rays with a diffraction angle of 2θ, a crystal plane distance d, and a wavelength of λ satisfy the Bragg equation 2dsinθ=λ, diffraction occurs. When the component is subjected to external stress or there is residual stress inside, the strain generated by the crystal plane spacing is ε=△d / d=-△θcotθ and the strain amounts in different directions are different, which causes the diffraction spectrum to shift with the incident angle. The peak displacement can be measured to determine the strain in the direction of the normal line of the crystal plane, and then the stress is calculated according to elastic mechanics. Measure the residual stress on the surface of the leaf spring.

[0042] Further, step S12: performing residual stress detection on one of the shot peened leaf springs, further comprising:

[0043] Step S122: chemically corrode the surface of the shot-peened leaf spring using a delamination method to obtain a secondary surface of the target leaf spring.

[0044] Step S123: Perform residual stress detection on the secondary surface of the first target leaf spring to obtain a first surface residual compressive stress value, and stop the detection after the first surface residual compressive stress value is a positive value.

[0045] Through steps S122-S123, the subsurface residual stress is measured by the stripping method. Specifically, the stripping method is implemented by chemical corrosion, and a chemical reagent with a certain formula is used to chemically corrode the local surface of the specimen to achieve the purpose of removing the surface layer of the specimen to a certain depth. The test is stopped when the first surface residual compressive stress value is positive.

[0046] Further, step S16: performing residual stress detection on the secondary shot peening leaf spring to obtain second residual stress field data information, including:

[0047] Step S161: Perform residual stress detection on the surface of the secondary shot peening leaf spring to obtain second residual stress field data information, which at least includes: a second surface residual compressive stress value, a second maximum residual compressive stress value, a depth value of the second maximum residual compressive stress from the surface, and a second residual compressive stress field depth value.

[0048] Similarly, the residual stress is measured by X-ray diffraction method, samples are taken at specified positions for detection, and the residual stress is measured by X-ray diffraction method.

[0049] Further, step S16: performing residual stress detection on the secondary shot peening leaf spring also includes:

[0050] Step S162: chemically corrode the surface of the secondary shot peened leaf spring using a peeling method to obtain a secondary surface of the target leaf spring.

[0051] Step S163: Perform residual stress detection on the secondary surface of the secondary shot peened leaf spring to obtain a secondary surface residual compressive stress value, and stop the detection after the secondary surface residual compressive stress value is a positive value.

[0052] Similarly, the stripping method is used to measure the subsurface residual stress. Specifically, it is achieved by chemical corrosion stripping, using a certain formula of chemical reagents to chemically corrode the local surface of the specimen to achieve the purpose of removing a certain depth of the surface layer of the specimen. The test is stopped when the second surface residual compressive stress value is positive.

[0053] like Figure 2 As shown, step S18: based on the first residual stress field data information and the second residual stress field data information, determining the stress change data information of the target leaf spring after the second shot peening operation, including:

[0054] Step S181: Based on the first surface residual compressive stress value and the second surface residual compressive stress value, determine the surface residual compressive stress change data information of the stress change data information of the target leaf spring after the second shot peening operation, the surface residual compressive stress change data information being a value obtained by increasing the second surface residual compressive stress value compared to the first surface residual compressive stress value.

[0055] Step S182: Based on the depth value of the first maximum residual compressive stress from the surface and the depth value of the second maximum residual compressive stress from the surface, determine the 1 / 2Zc stress change data of the stress change data of the target leaf spring after the second shot peening operation, the 1 / 2Zc stress change data being a value obtained by increasing the depth value of the second maximum residual compressive stress from the surface compared to the depth value of the first maximum residual compressive stress from the surface.

[0056] Further, step S20: when it is determined that the stress change data information meets the preset evaluation conditions, it is determined that the shot peening quality of the target leaf spring meets the requirements, and the preset evaluation conditions at least include: a surface residual compressive stress index value, a 1 / 2Zc stress index value, and Zc is the depth of the maximum residual compressive stress from the surface, including:

[0057] Step S201: When it is determined that the surface residual compressive stress change data information is greater than or equal to the surface residual compressive stress index value, and the 1 / 2Zc stress change data information is greater than or equal to the 1 / 2Zc stress index value, the shot peening strengthening effect meets the requirements.

[0058] Specifically, the surface residual compressive stress index value is 10%, and the 1 / 2Zc stress index value is 5%.

[0059] Further, step S20: when it is determined that the stress change data information meets the preset evaluation conditions, it is determined that the shot peening quality of the target leaf spring meets the requirements, and then it also includes:

[0060] Step S22: When it is determined that the surface residual compressive stress change data information is less than the surface residual compressive stress index value, and the 1 / 2Zc stress change data information is less than the 1 / 2Zc stress index value, the intensity of the second shot peening is adjusted.

[0061] Further, step S10: performing a first shot peening operation on the surfaces of at least two target leaf springs to obtain at least two first shot peened leaf springs, which includes:

[0062] Step S08: The leaf spring sample is subjected to quenching, medium-temperature tempering, and surface decarburization to obtain a target leaf spring.

[0063] Specifically, the leaf spring samples are processed by quenching + medium-temperature tempering process. The metallographic inspection requires that the matrix forms a tempered troostite structure, the surface decarburization layer is less than 0.15mm, there is no complete decarburization, and the surface hardness reaches 45-50HRC through the Rockwell hardness test.

[0064] Further, step S20: when it is determined that the stress change data information meets the preset evaluation condition, it is determined that the shot peening quality of the target leaf spring meets the requirements, and then includes:

[0065] Step S24: obtaining strengthening process parameters of the first shot peening operation and strengthening process parameters of the second shot peening operation;

[0066] Step S26: Check whether the surface roughness of the primary shot peening leaf spring and the surface roughness of the secondary shot peening leaf spring meet the requirements.

[0067] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0068] The present invention discloses an evaluation method for the residual compressive stress field of a single-piece steel leaf spring after composite shot peening. A composite strengthening shot peening process is adopted for a single-piece steel leaf spring, that is, the first shot peening is required to obtain a sufficiently high residual compressive stress and a sufficiently deep residual compressive stress field; the second shot peening is required to adjust and improve the residual compressive stress distribution from the surface of the outer layer to the peak value. Then, the residual stress of the two shot peening effects is detected by X-ray diffraction method, and the two positions of the surface and the subsurface are evaluated. It is required that the surface compressive stress value after the second shot peening is increased by ≥10% compared with the surface compressive stress value after the first shot peening; it is required that the residual compressive stress value at the 1 / 2Zc1 position after the second shot peening is increased by ≥5% compared with the residual compressive stress value after the first shot peening. Surface metallographic structure, surface hardness, and surface roughness requirements. The surface metallographic structure and surface hardness requirements are achieved through heat treatment, and the residual stress field and surface roughness requirements are achieved through shot peening. By stipulating four factors affecting surface integrity - surface microstructure parameters, mechanical properties parameters, residual stress parameters and process technology requirements for surface stress concentration, the optimal performance indicators of leaf spring parts can be achieved.

[0069] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0070] In addition to the above, it should be noted that "one embodiment", "another embodiment", "embodiment", etc. mentioned in this specification refer to the specific features, structures or characteristics described in conjunction with the embodiment included in at least one embodiment generally described in this application. The same expression appearing in multiple places in the specification does not necessarily refer to the same embodiment. Further, when describing a specific feature, structure or characteristic in conjunction with any embodiment, it is claimed that the realization of such feature, structure or characteristic in conjunction with other embodiments also falls within the scope of the present invention.

[0071] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for evaluating the quality of shot peening of a small leaf spring, characterized in that: include: Performing a first shot peening operation on the surfaces of at least two target leaf springs to obtain at least two once shot peened leaf springs; Performing residual stress detection on one of the once shot peened leaf springs to obtain first residual stress field data information; performing a second shot peening operation on the surface of another of the first shot peened leaf springs to obtain a second shot peened leaf spring; Performing residual stress detection on the secondary shot peening leaf spring to obtain second residual stress field data information; Determining stress change data information of the target leaf spring after the second shot peening operation based on the first residual stress field data information and the second residual stress field data information; When it is determined that the stress change data information satisfies a preset evaluation condition, it is determined that the shot peening quality of the target leaf spring meets the requirements.

2. The shot peening quality evaluation method for a small-piece leaf spring according to claim 1, characterized in that: Performing residual stress detection on one of the once shot peened leaf springs to obtain first residual stress field data information includes: Residual stress detection is performed on the surface of the first target leaf spring to obtain the first residual stress field data information, which at least includes: a first surface residual compressive stress value, a first maximum residual compressive stress value, a depth value of the first maximum residual compressive stress from the surface, and a first residual compressive stress field depth value.

3. The shot peening quality evaluation method for a small-piece leaf spring according to claim 2, characterized in that: Performing residual stress detection on one of the once shot peened leaf springs also includes: chemically corroding the surface of the primary shot peened leaf spring by a peeling method to obtain a secondary surface of the target leaf spring; A residual stress test is performed on the secondary surface of the first target leaf spring to obtain a first surface residual compressive stress value, and the test is stopped after the first surface residual compressive stress value becomes a positive value.

4. The shot peening quality evaluation method for a small leaf spring according to claim 2, characterized in that: Performing residual stress detection on the secondary shot peening leaf spring to obtain second residual stress field data information includes: Residual stress detection is performed on the surface of the secondary shot peening leaf spring to obtain the second residual stress field data information, which at least includes: a second surface residual compressive stress value, a second maximum residual compressive stress value, a depth value of the second maximum residual compressive stress from the surface, and a second residual compressive stress field depth value.

5. The shot peening quality evaluation method for a small-piece leaf spring according to claim 4, characterized in that: The residual stress detection of the secondary shot peening leaf spring also includes: chemically corroding the surface of the secondary shot peened leaf spring by a peeling method to obtain a secondary surface of the target leaf spring; The secondary surface of the secondary shot peening leaf spring is tested for residual stress to obtain a secondary surface residual compressive stress value, and the test is stopped after the secondary surface residual compressive stress value becomes a positive value.

6. The shot peening quality evaluation method for a small leaf spring according to claim 4, characterized in that: Determining stress change data information of the target leaf spring after the second shot peening operation based on the first residual stress field data information and the second residual stress field data information includes: Based on the first surface residual compressive stress value and the second surface residual compressive stress value, determining the surface residual compressive stress change data information of the stress change data information of the target leaf spring after the second shot peening operation, wherein the surface residual compressive stress change data information is a value in which the second surface residual compressive stress value is increased compared to the first surface residual compressive stress value; Based on one-half of the depth value of the first maximum residual compressive stress from the surface and one-half of the depth value of the second maximum residual compressive stress from the surface, 1 / 2Zc stress change data information of the stress change data information of the target leaf spring after the second shot peening operation is determined, and the 1 / 2Zc stress change data information is a value obtained by increasing the depth value of one-half of the second maximum residual compressive stress from the surface compared to the depth value of one-half of the first maximum residual compressive stress from the surface.

7. The shot peening quality evaluation method for a small leaf spring according to claim 6, characterized in that: In the case where it is determined that the stress change data information meets the preset evaluation conditions, it is determined that the shot peening quality of the target leaf spring meets the requirements, and the preset evaluation conditions at least include: a surface residual compressive stress index value, a 1 / 2Zc stress index value, where Zc is the depth of the maximum residual compressive stress from the surface, including: When it is determined that the surface residual compressive stress change data information is greater than or equal to the surface residual compressive stress index value, and the 1 / 2Zc stress change data information is greater than or equal to the 1 / 2Zc stress index value, the shot peening strengthening effect meets the requirements.

8. The shot peening quality evaluation method for a small leaf spring according to claim 7, characterized in that: In the case where it is determined that the stress change data information meets the preset evaluation conditions, it is determined that the shot peening quality of the target leaf spring meets the requirements, and then it also includes: When it is determined that the surface residual compressive stress change data information is less than the surface residual compressive stress index value, and the 1 / 2Zc stress change data information is less than the 1 / 2Zc stress index value, the intensity of the second shot peening is adjusted.

9. The shot peening quality evaluation method for a small leaf spring according to claim 1, characterized in that: The first shot peening operation is performed on the surface of at least two target leaf springs to obtain at least two first shot peened leaf springs, which comprises: The target leaf spring is obtained by subjecting the leaf spring sample to quenching, medium-temperature tempering and surface decarburization.

10. The shot peening quality evaluation method for a small leaf spring according to claim 1, characterized in that: When it is determined that the value of the second residual stress field data information improved compared with the first residual stress field data information satisfies the residual compressive stress field evaluation index value, the shot peening strengthening effect meets the requirements, including: Obtaining strengthening process parameters of a first shot peening operation and strengthening process parameters of a second shot peening operation; Check whether the surface roughness of the primary shot peening leaf spring and the surface roughness of the secondary shot peening leaf spring meet the requirements.

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