CN113642175B - Shot peening deformation numerical simulation method considering coverage rate and path - Google Patents

Abstract

The invention discloses a shot peening deformation numerical simulation method considering coverage rate and paths, which comprises the following steps: calculating a single shot impact model, a number of shots and shot coordinates, calculating a multi-shot impact model and a part deformation prediction model, firstly, establishing the single shot impact model, then calculating the number of shots and the shot coordinates meeting the coverage rate requirement according to the obtained diameter of a pit, secondly, establishing the multi-shot model to obtain a depth-stress curve, thirdly, establishing the part deformation prediction model, endowing a stress value to the part to obtain part deformation, then establishing a new part model, endowing a temperature gradient field to the part, changing the expansion rate of a material to enable the deformation of the part under the temperature gradient field to be similar to that under the stress field, and finally endowing the part with the temperature gradient field according to a path to obtain the deformation of the part under a specific shot blasting path. The invention considers the influence of coverage rate and shot blasting path on the deformation of the part, and in practice, the optimization of process parameters can play a guiding role.

Description

A numerical simulation method for shot peening deformation considering coverage rate and path

Technical field

The invention relates to the technical field of shot peening deformation, in particular to a numerical simulation method of shot peening deformation that takes into account coverage and path.

Background technique

Shot peening is a surface strengthening technology that sprays the surface of the workpiece with a high-speed moving shot stream, causing uneven plastic deformation on the surface of the workpiece and forming a residual compressive stress layer of a certain depth, which can effectively improve the fatigue life of the part and is suitable for Available in various shapes and sizes, they are widely used in various fields such as automobiles and aviation. As an important structural part of the aircraft fuselage, aviation thin-walled structural parts have poor stiffness. After shot peening, the components are prone to deformation, which has a greater impact on the accuracy of the parts. The deformation of parts caused by shot peening is related to many factors, including the material properties of the parts being sprayed, the distance and angle between the shot peening machine's nozzle and the workpiece surface, as well as the size of the projectile, the impact speed of the projectile, the material of the projectile, the angle of incidence and the coverage It is related to parameters such as rate and shot peening path.

In actual shot peening operations, a large number of shot peening parameters need to be debugged, and experimental measurement of deformation is expensive and time-consuming. Conducting numerical simulations before actual operations and using numerical simulations for parameter optimization can significantly reduce the number of experiments, thereby improving the efficiency of parameter optimization and saving production costs. The most widely used method at present is to calculate the impact of each projectile in sequence to obtain the workpiece deformation caused by the impact of a large number of projectiles. However, when performing numerical simulations of shot peening on actual parts, the number of projectiles required for the actual part is huge. The computational complexity and cost of the simulation process are unacceptable.

Contents of the invention

The technical problem solved by the present invention is to provide a numerical simulation method for shot peening deformation that considers coverage rate and path, solves the numerical simulation problem of shot peening deformation of large-size parts, and considers the effects of coverage rate and shot peening path on deformation. Influence.

The technical solution of the present invention is:

In order to solve the above technical problems, the present invention provides a numerical simulation method for shot peening deformation considering coverage rate and path, which includes the following steps:

The first step is to convert the shot peening process parameters into the velocity of the projectile according to the empirical formula. The empirical formula is as follows:

In the formula, V _s is the projectile velocity, P _s is the injection pressure of the shot peening machine, D _s is the projectile diameter, is the projectile flow rate;

In the second step, obtain the Johnson-Cook material parameters of the part and establish a single projectile impact model in Abaqus. The speed of the projectile is calculated from the empirical formula in the first step. The target material of the single projectile impact model has a side length of A cube block 5 times the diameter of the projectile;

The third step is to extract the displacement of the target impact area along the layer depth direction in the single projectile impact model, and take the distance between two points where the displacement along the layer depth direction is zero as the diameter of the crater;

The fourth step is to calculate the number of projectiles required to meet the coverage requirements. In Matlab, divide the target surface into equal parts along the length direction and width direction perpendicular to the depth direction. The length direction is divided into m parts, that is, the length direction contains m. +1 node, the width direction is divided into n parts, that is, the width direction contains n+1 nodes. After generating a total of N=(m+1)×(n+1) nodes, Matlab is used to randomly generate projectiles above the target. Sphere center coordinates, the generated projectile will not overlap with the generated projectile spatial position after the randomly generated projectile center space coordinates are satisfied;

The fifth step is to calculate the impact point of the projectile on the target according to the speed direction of the projectile, and calculate the distance from each node to the impact point of all projectile centers. If the minimum distance from a node to the impact point of all projectile centers is less than the crater radius, then the node is in the shot peening area. The number of all nodes in the shot peening area is recorded as M, then the coverage rate C=M/N×100%. If the coverage rate C is less than the coverage rate requirement, increase the number of projectiles. number until C is greater than or equal to the required coverage, record the number of projectiles and the spatial coordinates of each projectile at this time;

The sixth step, in order to reduce the random error of the simulation results, use MATLAB to generate random coordinates that meet the coverage requirements multiple times, record each generation result, and find the average number of required projectiles for multiple solutions. , select the group of projectile coordinates closest to the average number as the solution result;

In the seventh step, take the projectile coordinate results solved in the sixth step and establish a model of multiple projectiles impacting the target in ABAQUS;

The eighth step is to extract the depth-stress curve in the length direction and width direction of the target in the multi-projectile impact model, and record the stress, transition from positive value to negative value, and depth at a certain point closer to zero value as the impact of shot peening depth;

The ninth step is to establish a part deformation prediction model, without considering the shot peening path, and assign stress to the part at one time to obtain the deformation of the part without considering the path, especially the deformation value of a certain feature point of the part of concern;

The tenth step is to establish a new finite element model of the part and establish a temperature gradient field. The coverage range of the temperature gradient field is the shot peening area. The depth direction is from the surface of the part affected by shot peening to the depth affected by shot peening. The temperature of other parts of the part is set to 25°C. The maximum temperature value of the temperature gradient field is arbitrary, but not greater than the melting point of the material. The minimum temperature value of the temperature gradient field is 25°C.

The eleventh step is to remove the temperature field after a period of time. At this time, the part will undergo plastic deformation under the action of the temperature field. The fixed gradient temperature field remains unchanged, changing the expansion coefficient of the material, causing the part to deform. When the deformation amount of the part, especially When the difference between the deformation value of a certain characteristic point of the part concerned and the deformation value under stress conditions is within an acceptable range, record the expansion coefficient of the part at this time;

In the twelfth step, establish a new finite element model of the part, assign the expansion coefficient obtained in the eleventh step to the part material, and assign the equivalent temperature field to the part in sequence according to the shot peening path. After a period of time, remove it. The width of the temperature gradient field given by the path is equal to the width of the shot peening narrow band, and the deformation of the part under different shot peening path conditions is obtained, especially the deformation value of a certain characteristic point of the part of concern.

The beneficial effect of the present invention is that: taking into account the influence of coverage rate and shot peening path on the deformation of parts, the deformation effects of parts under different coverage rates or different shot peening paths can be compared, thereby formulating a more appropriate shot peening process plan, and the steps In the eleventh step, the material expansion rate has a monotonic relationship with the deformation value of the part. By changing the expansion rate, the deformation amount of the part can be easily realized, especially the deformation value of a certain feature point of the part of concern and the deformation value under the stress condition. When the difference is within the acceptable range.

Description of drawings

Figure 1 is a flow chart of a numerical simulation method for shot peening deformation considering coverage and path provided by an embodiment of the present invention;

Figure 2 is a calculation flow chart to meet coverage requirements;

Figure 3 is a flow chart for randomly generating projectile center coordinates.

Detailed ways

Contents not described in detail in the specification of the present invention are well-known technologies to those skilled in the art.

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

Referring to Figure 1, there is shown a flow chart of a numerical simulation method for shot peening deformation considering coverage and path provided by an embodiment of the present invention. As shown in Figure 1, the numerical simulation method includes the following steps:

The first step is to convert the shot peening process parameters into the velocity of the projectile according to the empirical formula. The empirical formula is as follows:

In the formula, V _s is the projectile velocity, P _s is the injection pressure of the shot peening machine, D _s is the projectile diameter, is the projectile flow rate;

In the second step, obtain the Johnson-Cook material parameters of the part and establish a single projectile impact model in Abaqus. The speed of the projectile is calculated from the empirical formula in the first step. The target material of the single projectile impact model has a side length of A cube block 5 times the diameter of the projectile;

The third step is to extract the displacement of the target impact area along the layer depth direction in the single projectile impact model, and take the distance between two points where the displacement along the layer depth direction is zero as the diameter of the crater;

The fourth step is as shown in the coverage calculation flow chart in Figure 2. Calculate the number of projectiles required to meet the coverage requirements. In Matlab, divide the target surface into equal parts along the length and width directions perpendicular to the depth direction. The length direction is divided into m parts, that is, the length direction contains m+1 nodes, and the width direction is divided into n parts, that is, the width direction contains n+1 nodes, generating a total of N=(m+1)×(n+1) After the node, Matlab is used to randomly generate the coordinates of the projectile center above the target. The flow chart of the random generation of the projectile center coordinates is shown in Figure 3. The randomly generated projectile center coordinates satisfy the generated projectile and the generated projectile. Projectiles do not overlap in space position;

The fifth step is to calculate the impact point of the projectile on the target according to the speed direction of the projectile, and calculate the distance from each node to the impact point of all projectile centers. If the minimum distance from a node to the impact point of all projectile centers is less than the crater radius, then the node is in the shot peening area. Record the number of nodes in the shot peening area as M, then the coverage rate C = M/N × 100%. If the coverage rate C is less than the coverage rate requirement, increase the number of projectiles. number until C is greater than or equal to the required coverage, record the number of projectiles and the spatial coordinates of each projectile at this time;

The sixth step, in order to reduce the random error of the simulation results, use MATLAB to generate random coordinates that meet the coverage requirements multiple times, record each generation result, and find the average number of required projectiles for multiple solutions. , select the group of projectile coordinates closest to the average number as the solution result;

In the seventh step, take the projectile coordinate results solved in the sixth step and establish a model of multiple projectiles impacting the target in ABAQUS;

The eighth step is to extract the depth-stress curve in the length direction and width direction of the target in the multi-projectile impact model, and record the stress, transition from positive value to negative value, and depth at a certain point closer to zero value as the impact of shot peening depth;

The ninth step is to establish a part deformation prediction model, without considering the shot peening path, and assign stress to the part at one time to obtain the deformation of the part without considering the path, especially the deformation value of a certain feature point of the part of concern;

In the tenth step, establish a new finite element model of the part and establish a temperature gradient field. The coverage range of the temperature gradient field is the shot peening area. The depth direction is from the surface of the part affected by shot peening to the depth affected by shot peening. The temperature of other parts of the part is set to 25°C. The maximum temperature value of the temperature gradient field is arbitrary, but not greater than the melting point of the material. The minimum temperature value of the temperature gradient field is 25°C.

The eleventh step is to remove the temperature field after a period of time. At this time, the part will undergo plastic deformation under the action of the temperature field. The fixed gradient temperature field remains unchanged, changing the expansion coefficient of the material, causing the part to deform. When the deformation amount of the part, especially When the difference between the deformation value of a certain characteristic point of the part concerned and the deformation value under stress conditions is within an acceptable range, record the expansion coefficient of the part at this time;

In the twelfth step, establish a new finite element model of the part, assign the expansion coefficient obtained in the eleventh step to the part material, and assign the equivalent temperature field to the part in sequence according to the shot peening path. After a period of time, remove it. The width of the temperature gradient field given by the path is equal to the width of the shot peening narrow band, and the deformation of the part under different shot peening path conditions is obtained, especially the deformation value of a certain characteristic point of the part of concern.

Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art will understand that various changes, modifications, and substitutions can be made to these embodiments without departing from the principles and spirit of the invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (2)

1. A shot peening deformation numerical simulation method considering coverage rate and path includes: the method comprises the steps of calculating the number of shots and the coordinates of the shots meeting the coverage rate requirement, calculating a multi-shot impact model and a part deformation prediction model, firstly, establishing the single-shot impact model, converting the shot speed in the single-shot impact model through an empirical formula, then, calculating the number of shots and the coordinates of the shots meeting the coverage rate requirement according to the diameter of a pit obtained by the single-shot impact model, secondly, establishing the multi-shot model to obtain a depth-stress curve, thirdly, establishing the part deformation prediction model, endowing a stress value to a part to obtain part deformation, secondly, establishing a new part model, endowing a temperature gradient field to the part, changing the material expansion rate to enable the deformation of the part under the temperature gradient field to be similar to that of the part under the stress field, and finally endowing a temperature gradient field to the part according to a path to obtain the deformation of the part under a specific shot blasting path.

2. The numerical simulation method according to claim 1, wherein: the method comprises the following steps:

the first step, converting shot blasting process parameters into shot velocity according to an empirical formula, wherein the empirical formula is as follows:

wherein V is _s To the speed of the projectile, P _s For the shot-blasting machine injection pressure, D _s In order to obtain the diameter of the bullet,is the flow rate of the projectile;

secondly, acquiring Johnson-Cook material parameters of a part, and establishing a single-pellet impact model in Abaqus, wherein the speed of a pellet is obtained by conversion of an empirical formula in the first step, and the target material of the single-pellet impact model is a cube block with the side length being 5 times the diameter of the pellet;

thirdly, extracting displacement of a target impact area in the single shot impact model along the depth direction, and taking the distance between two points, which is zero in the displacement along the depth direction, as the diameter of a pit;

fourthly, calculating the number of the shots required for meeting the coverage rate requirement, dividing the surface of the target material in Matlab along the length direction and the width direction which are perpendicular to the depth direction, wherein the length direction is divided into m parts, namely the length direction contains m+1 nodes, the width direction is divided into N parts, namely the width direction contains n+1 nodes, N= (m+1) x (n+1) nodes are generated altogether, then, the Matlab is utilized to randomly generate the spherical center coordinates of the shots above the target material, and the shots generated after the spherical center space coordinates of the randomly generated shots meet the space positions of the generated shots are not overlapped;

fifthly, calculating the falling points of the shots on the target according to the speed direction of the shots, calculating the distance from each node to all the shot center falling points, if the minimum value of the distance from a certain node to all the shot center falling points is smaller than the radius of a shot pit, the node is positioned in a shot blasting area, the number of the nodes positioned in the shot blasting area is marked as M, the coverage rate C=M/N multiplied by 100%, if the coverage rate C is smaller than the coverage rate requirement, the number of the shots is increased until C is larger than or equal to the required coverage rate, and recording the number of the shots and the space coordinates of each shot at the moment;

sixth, in order to reduce random errors of simulation results, MATLAB is utilized to generate random coordinates meeting coverage rate requirements for multiple times, the generated results are recorded each time, the average value of the required number of shots solved for multiple times is calculated, and a group of shot coordinates closest to the average value is selected as a solving result;

seventh, taking the pellet coordinate result solved in the sixth step, and establishing a model of the impact of multiple pellets on the target in ABAQUS;

eighth, extracting depth-stress curves in the length direction and the width direction of the target in the multi-shot impact model, and recording stress, transition from a positive value to a negative value, and taking the depth of a certain point approaching to a zero value as shot blasting influence depth;

ninth, a part deformation prediction model is established, a shot blasting path is not considered, stress is given to the part at one time, and the deformation of the part under the condition that the path is not considered, particularly the deformation value of a certain characteristic point of the concerned part, is obtained;

a tenth step of establishing a new part finite element model, and establishing a temperature gradient field, wherein the coverage area of the temperature gradient field is a shot blasting area, the depth direction is from the shot blasting surface of the part to the shot blasting influence depth, the temperature of other parts of the part is set to 25 ℃, the maximum temperature value of the temperature gradient field is arbitrary but not greater than the melting point of a material, and the minimum temperature value of the temperature gradient field is set to 25 ℃;

eleventh, after a period of time, removing the temperature field, wherein the part is plastically deformed under the action of the temperature field, the gradient temperature field is fixed, the expansion coefficient of the material is changed, the part is deformed, and when the deformation amount of the part, particularly the difference value between the deformation value of a certain characteristic point of the concerned part and the deformation value under the stress condition is within an acceptable range, the expansion coefficient of the part is recorded;

and twelfth, establishing a new part finite element model, endowing the expansion coefficient obtained in the eleventh step to a part material, endowing the equivalent temperature field to the part sequentially according to the path sequence of shot blasting, and removing after a period of time, wherein the width of the temperature gradient field endowed according to the path is equal to the width of a shot blasting narrow band, so as to obtain the deformation of the part under different shot blasting path conditions, in particular the deformation value of a certain characteristic point of the concerned part.