Simulation- and Experiment-Based Method for Calculating Shot Peening Coverage

Abstract

The present invention discloses a method for calculating shot peening coverage based on simulation and experiment. The parameters determined after shot peening intensity are used as the input parameters of the shot peening equipment. Based on the shot peening flow rate, the spray gun moving speed, and the shot peening area, combined with the crater diameter, the coverage rate after shot peening treatment of titanium alloy specimens under different shot peening parameters can be calculated. The minimum coverage rate should be ensured to be less than or equal to 100%, and it is verified with the standard pictures of 83% and 98% coverage rates of shot peening. Based on this, the coverage rates under other groups of shot peening parameters are calculated. The present invention discloses a method for calculating shot peening coverage based on simulation and experiment, which can quickly calculate the shot peening coverage under specific shot peening processing parameters, and the shot peening coverage can be accurate to the order of magnitude of single digits, rather than the previous descriptive expressions such as greater than 100%. It provides an accurate expression method and technical support for the research on the effect and optimization of the shot peening process.

Description

Technical Field

[0001] The present invention relates to the field of mechanical manufacturing and strengthening processing. More specifically, the present invention relates to a calculation of shot peening coverage based on simulation and experiment. Background Art

[0002] Shot peening coverage, i.e., shot peening surface coverage rate, is the ratio of the area occupied by shot peening pits on the surface of the part being peened to the total surface area of the peened surface, expressed as a percentage. Usually, a coverage rate of 98% is used as the criterion for 100% determination. On this basis, the shot peening time is multiplied by 1.25 times as the complete shot peening coverage time, i.e., the coverage rate is 100%.

[0003] Objective drawbacks of the prior art: The general parameters of shot peening strengthening processing are shot peening intensity and coverage rate. The shot peening intensity can be determined based on the Almen strip and the input amount of the shot peening strengthening equipment; however, the shot peening coverage rate cannot be simply determined after the shot peening intensity is determined.

[0004] Currently, the surface coverage rate of less than 100% of the specimen or part is determined by visual method, that is, methods such as a magnifying glass of 10 times or more (including 10 times), endoscope, fluorescent liquid or fluorescent pen, and polyvinyl chloride film are used to detect the surface coverage rate pattern and compare it with Figure 4 the standard pattern of different surface coverage rates of the shot peening specimen shown in to judge its coverage rate. If the coverage rate is greater than 100%, the shot peening pits overlap each other, and the visual method cannot judge the specific coverage rate value, and only estimation based on experience can be used, with low accuracy.

[0005] Even if the coverage rate of 100% is determined, different coverage rates can only be achieved by adjusting the shot peening strengthening time; if other shot peening equipment input parameters (such as air pressure, flow rate, etc.) are changed, the specific parameters for a coverage rate of 100% need to be re-determined, and then further iteration is required to obtain the required coverage rate value, and the procedure is cumbersome and complex. Summary of the Invention

[0006] An object of the present invention is to solve at least the above problems and / or defects and provide at least the advantages described hereinafter.

[0007] To achieve these objects and other advantages of the present invention, a calculation method of shot peening coverage based on simulation and experiment is provided. The parameters after the shot peening intensity is determined are used as the input parameters of the shot peening strengthening equipment. Based on the shot peening flow rate, the spray gun moving speed, and the shot peening area, and combined with the crater diameter, the coverage rate after shot peening treatment of titanium alloy specimens under different shot peening parameters can be calculated, where the minimum coverage rate should be guaranteed to be less than or equal to 100%, and it is verified with the standard pictures of shot peening coverage rates of 83% and 98%, and the coverage rates under other groups of shot peening parameters are calculated based on this.

[0008] Preferably, the shot peening coverage rate C under the set parameters is calculated by the ratio of the total area of the shot impact craters to the area of the machined surface of the test piece by the spray gun in the following formula over a period of time:

[0009]

[0010] In the above formula, S is the total mass of all the shots, V is the mass of a single shot, r is the radius of the crater, k is the effective coefficient, and the effective coefficient refers to the proportion of the shots hitting the machined surface of the test piece. Ft is the correction coefficient, and the correction coefficient is a coefficient fitted by comparing with the standard pictures of 83% and 98% coverage rates in HB / Z 26-2011;

[0011] The radius r of the crater is obtained by establishing a three-dimensional finite element model of the shot peening strengthening process using finite element analysis software.

[0012] Preferably, the total mass S of all the shots is obtained by the following formula:

[0013]

[0014] In the above formula, q is the shot flow rate and v is the moving speed of the spray gun;

[0015] The mass V of a single shot is obtained by the following formula:

[0016]

[0017] In the above formula, R is the radius of the shot and ρ is the density of the shot.

[0018] Preferably, the three-dimensional finite element model is used to simulate and verify a single shot. During the verification, the impact simulation is completed by loading the average velocity Vs of the shot obtained by the following formula onto the shot:

[0019]

[0020] In the above formula, p is the shot peening pressure, d is the diameter of the shot, and q is the shot flow rate.

[0021] Preferably, based on the radius r of the crater calculated by the three-dimensional finite element model, the shot peening coverage rate obtained by the shot peening coverage rate C calculation formula can be verified;

[0022] Preferably, the verification method is as follows:

[0023] S1. Shot peening strengthening processing is performed on the test piece by programming two sets of input parameters of the shot peening strengthening equipment that can obtain saturated shot peening strength as input quantities;

[0024] S2. The surface of the test piece after shot peening is observed using an electronic magnifying glass to obtain the corresponding electron photo of the coverage rate;

[0025] S3. Compare the electronic photos of the coverage rate with the standard pictures of 83% and 98% coverage rates in HB / Z 26 - 2011;

[0026] S4. According to the coverage rate calculation formula of shot peening coverage rate, compare the calculated coverage rate pictures and the electronic photos of the coverage rate with the standard pictures of 83% and 98% coverage rates in HB / Z 26 - 2011 respectively to verify the accuracy of the calculated coverage rate pictures.

[0027] The present invention has at least the following beneficial effects: The present invention can quickly calculate the shot peening coverage rate under specific shot peening processing parameters, and the shot peening coverage rate can be accurate to the order of single digits, rather than the previous descriptive expressions such as greater than 100%. It provides an accurate expression method and technical support for the research on the effect and process optimization of shot peening strengthening.

[0028] Other advantages, objectives and features of the present invention will be partially reflected by the following description, and partially will also be understood by those skilled in the art through the research and practice of the present invention. Brief Description of the Drawings

[0029] Figure 1 It is a schematic diagram for calculating the coverage rate of a straight spray gun;

[0030] Figure 2 It is a schematic diagram for calculating the coverage rate of a rotating spray gun;

[0031] Figure 3 It is a schematic diagram for verifying the coverage rate of the present invention;

[0032] Figure 4 It is the standard pattern of the morphology of different surface coverage rates of shot peening specimens in the prior art. Detailed Embodiment

[0033] The following further describes the present invention in detail with reference to the drawings, so that those skilled in the art can implement it according to the description in the specification.

[0034] In order to overcome the deficiencies of low calculation accuracy and complex and cumbersome procedures in the existing calculation of shot peening coverage rate, this project combines shot peening simulation and tests, proposes a method for quickly and accurately calculating the shot peening coverage rate, and has passed the test verification, providing technical support for shot peening strengthening research.

[0035] 1. Coverage Rate Calculation

[0036] The shot peening coverage rate refers to the percentage of the area occupied by the shot peening marks on the surface of the part after shot peening strengthening to the total area. Usually, the surface coverage rate of shot peening strengthening on the metal surface should reach or exceed 100%, that is, the shot peening strengthening must at least reach the saturation state.

[0037] The input parameters of the shot peening equipment used in this project are all the parameters determined after the shot peening intensity. According to the shot peening flow rate, the moving speed of the spray gun, and the shot peening area, combined with the crater diameter, the coverage rate of the titanium alloy specimens after shot peening under different shot peening parameters can be calculated. The minimum coverage rate should be ensured to be less than or equal to 100%, and it is verified with the standard pictures of 83% and 98% coverage rates in the shot peening standard HB / Z 26-2011. Based on this, the coverage rates under other groups of shot peening parameters are calculated.

[0038] The shot peening equipment is a non-standard equipment. In order to strengthen various parts, the spray guns are also designed into different types. Among them, the typical representatives are the straight spray gun and the rotary spray gun.

[0039] For the straight spray gun, as Figure 1 shown, the spray gun A keeps a fixed distance from the Almen strip B. The spray gun moves through from one side of the processed surface C of the strip at a certain speed, and the shot flow D hits the Almen strip from the muzzle of the spray gun. Figure 1 The red arrow in

[0040] For the rotary spray gun, as Figure 2 shown, the spray gun E keeps a fixed distance from the Almen strip F. While the spray gun rotates, it moves through from one side of the processed surface G of the strip at a certain speed, and the shot flow H impacts the Almen strip in the tangential direction of the spray gun. Figure 2 The red arrow in

[0041] By calculating the ratio of the total area of the shot impact craters to the area of the processed surface of the strip within the time period when the spray gun passes, the coverage rate under the set parameters can be obtained. The calculation method is shown in formula (1).

[0042]

[0043] Among them, the total mass of all the shots is

[0044]

[0045] The mass of a single shot is

[0046]

[0047] In the formula: C—the shot peening coverage rate;

[0048] q—the shot flow rate;

[0049] v—the moving speed of the spray gun;

[0050] r—the radius of the crater;

[0051] k—the effective coefficient, which refers to the proportion of the shots hitting the processed surface of the specimen and is related to the distance h between the muzzle of the spray gun and the processed surface;

[0052] Ft - Correction factor, the coefficient fitted by comparing with the standard pictures of 83% and 98% coverage;

[0053] R - Projectile radius;

[0054] ρ - Projectile density.

[0055] Based on the coverage calculation formula (1), combined with the crater radius r, the coverage under the input parameters of each shot peening equipment can be calculated.

[0056] 2. Single-projectile simulation

[0057] In this project, the large finite element analysis software Abaqus is used to establish a three-dimensional finite element model of the shot peening process to obtain the crater radius r required for calculating the shot peening coverage. When the projectile impacts the specimen surface at a certain jet velocity during shot peening, in Abaqus, the jetting process of the projectile on the specimen surface under the impact load is simulated by defining the initial velocity of the projectile, thereby generating an impact load on the specimen surface. In actual shot peening tests, pneumatic shot peening equipment is used, and the jetting velocity of the projectile is mainly affected by factors such as projectile diameter, projectile flow rate, shot peening pressure, and projectile material. Therefore, it is necessary to convert the relevant coefficients in the actual shot peening process into the average projectile velocity required in the finite element simulation. This project adopts the empirical formula for the average projectile velocity shown in Equation (4), which can calculate the average projectile velocity through three parameters: projectile diameter, projectile flow rate, and shot peening pressure.

[0058]

[0059] In the formula: Vs - Projectile velocity (m / s);

[0060] p - Shot peening pressure (MPa);

[0061] d - Projectile diameter (mm);

[0062] q - Projectile flow rate (kg / min).

[0063] The three-dimensional finite element model of the shot peening process is a basic impact simulation. When modeling, the calculated average projectile velocity is loaded onto the projectile, and the modeling process will not be elaborated here in detail.

[0064] Combined with the analysis results of the three-dimensional finite element model, the crater diameter can be calculated in the plastic deformation area of the projectile impact area.

[0065] 3. Verification of shot peening coverage calculation

[0066] Based on the crater radius r calculated during the single-projectile simulation, the shot peening coverage calculation based on Equation (1) can be verified.

[0067] Taking shot peening with a rotating spray gun as an example, two sets of input parameters of shot peening equipment that can obtain saturated shot peening intensity are planned as input variables, and the specimens are subjected to shot peening. The surface of the specimen after shot peening is observed using an electronic magnifying glass. The coverage electron photos are compared with the pictures in the standard, and at the same time, its coverage is calculated according to the formula. The comparison is as Figure 3 shown. It can be seen that the calculated value of the coverage is very similar to the standard.

[0068] According to the calculation formula of the present invention, the coverage under different input parameters of different shot peening equipment for different metal materials can be calculated. This calculation method can be used to determine the scientificity of the parameters in shot peening research

[0069] The above solution is only an illustration of a preferred example, but is not limited thereto. When implementing the present invention, appropriate substitutions and / or modifications can be made according to the needs of the user.

[0070] The number of devices and the processing scale described here are used to simplify the description of the present invention. The application, modification, and variation of the present invention are obvious to those skilled in the art.

[0071] Although the embodiments of the present invention have been disclosed above, it is not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily achieved. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the examples shown and described here.

Claims

1. A shot peening coverage calculation method based on simulation and experiment, characterized in that: The parameters after the shot peening intensity is determined are used as the input parameters of the shot peening equipment. Based on the shot peening flow rate, the moving speed of the spray gun and the shot peening area, the coverage rate of the titanium alloy specimens after shot peening under different shot peening parameters is calculated in combination with the crater diameter. The coverage rate of the standard shot peening parameters of 83% and 98% is verified, and the coverage rate of other groups of shot peening parameters is calculated based on this. Shot peening coverage under set parameters C It is calculated by the ratio of the total area of ​​the crater impacted by the projectile during the spray gun passing time period to the area of ​​the test piece processing surface: In the above formula, S is the total projectile mass, V is the mass of a single projectile, r is the crater radius, k is the effective coefficient, which refers to the proportion of the projectile hitting the processed surface of the specimen. Ft is a correction factor, which is a coefficient obtained by comparing and fitting with the standard images of 83% and 98% coverage in HB / Z 26-2011; The crater radius r The three-dimensional finite element model of the shot peening process was established using finite element analysis software; Total projectile mass S Obtained by the following formula: In the above formula, q is the pellet flow rate, v is the moving speed of the spray gun; The mass of a single projectile V Obtained by the following formula: In the above formula, R is the projectile radius, ρ is the density of the projectile.

2. The shot peening coverage calculation method based on simulation and experiment as claimed in claim 1, characterized in that: The three-dimensional finite element model is used to simulate and verify a single projectile. During the verification, the average velocity of the projectile is obtained by the following formula Vs Load onto the projectile to complete the impact simulation: In the above formula, p is the shot peening pressure, d is the projectile diameter, q The pellet flow rate 。 3. The shot peening coverage calculation method based on simulation and experiment as claimed in claim 1, characterized in that: The shot peening coverage calculated by the shot peening coverage formula C is verified based on the crater radius r calculated based on the three-dimensional finite element model.

4. The shot peening coverage calculation method based on simulation and experiment as claimed in claim 3, characterized in that: The verification method is: S1. Shot peening is performed on the test piece by planning two sets of shot peening equipment input parameters that can obtain saturated shot peening intensity as input quantities; S2. Observe the surface of the test piece after shot peening using an electronic magnifying glass to obtain an electronic photograph of the corresponding coverage; S3. Compare the coverage electronic photo with the 83% and 98% coverage standard photos in HB / Z 26-2011; S4. Calculate the coverage rate according to shot peening coverage rate formula C, and compare the calculated coverage rate picture and coverage rate electronic photo with the 83% and 98% coverage rate standard pictures in HB / Z 26-2011 respectively to verify the accuracy of the calculated coverage rate picture.

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