An inverse simulation method for obtaining an initial unfolding model for shot peening forming process

Abstract

The present disclosure provides an inverse simulation method for obtaining an initial unfolding model for a shot peening forming process, which includes generating a body model and constructing a consistent Almen strip model based on the actual digital model of a target forming part by using computer software, applying a stress field to the Almen strip model in a finite element simulation software to perform simulation deformation calculation, continuously adjusting the magnitude of the stress field until the calculated deformation is consistent with the deformation of the Almen strip after a shot peening forming test under selected shot peening process parameters, thereby determining the corresponding equivalent induced stress field model, then performing an inversion operation on the equivalent induced stress field model to obtain a reverse stress field, and applying it to the body model according to the planned process path to perform inverse simulation calculation, so as to obtain the initial unfolding model, and obtaining a shot peening process plan matching the unfolding model based on the shot peening process parameters corresponding to the application path and the stress field.

Description

Technical Field

[0001] The present invention relates to the field of mechanical manufacturing, mainly to the field of shot peening forming, and particularly to a reverse simulation method for obtaining an initial unfolded model for a shot peening forming process. Background Art

[0002] In the shot peening forming process, obtaining a flattened model corresponding to a target formed part is a crucial step for subsequent planning of the shot peening process plan. Currently, it is mainly simply obtained by the "one-step method" in numerical simulation.

[0003] However, the flattening based on the "one-step method" ignores the extension effect brought by the process, especially for a process like shot peening forming that relies on material extension to achieve deformation. Practice has proved that the flattening without considering the shot peening forming process is often inaccurate. For example, after obtaining the initial unfolded digital model by the "one-step method" and machining it, and then conducting a shot peening forming test according to the planned process path and parameters, the actual part often has a larger outer dimension than the target value due to material shot peening extension, and even some key features are misaligned, resulting in inability to assemble. Subsequently, the initial unfolded model after flattening treatment still needs to be corrected by trial and error, which is time-consuming and laborious.

[0004] Moreover, for the shot peening forming process, the process parameters and process path of shot peening will directly affect the forming effect of the part. At the same time, the flattening of the part is often interrelated with the planning of the shot peening process parameters and the shot peening process path, that is, the flattening result needs to be corrected based on the extension under a certain shot peening process, and the determination of the shot peening process parameters and the process path needs to be planned based on an effective flattened blank.

[0005] Therefore, the existing methods, due to separating the shot peening process parameters and the process path from the flattening of the part, cannot obtain an accurate initial unfolded model for the shot peening forming process, and are inefficient, time-consuming and laborious. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the problems that the existing methods for the shot peening forming process are difficult to obtain an accurate and reliable initial unfolded model and are too inefficient, and a new reverse simulation method for obtaining an initial unfolded model for the shot peening forming process is proposed.

[0007] The present invention solves the above technical problems through the following technical solutions:

[0008] Specifically, the present invention provides a reverse simulation method for obtaining an initial unfolded model for a shot peening forming process, characterized in that the reverse simulation method includes:

[0009] Based on the digital model of the target formed part, using computer software to generate the body model of the target formed part;

[0010] Use computer software to generate an Almen strip-like model consistent with the body model of the target formed part, and apply a stress field to the Almen strip-like model in finite element simulation software to perform simulation deformation calculations. Among them, continuously adjust the size of the stress field model until the calculated deformation is consistent with the deformation of the Almen strip after shot peening forming test under the selected shot peening process parameters, thereby determining the equivalent induced stress field model corresponding to the selected shot peening process parameters;

[0011] Use finite element simulation software to perform an inversion operation on the equivalent induced stress field model to obtain a reverse stress field, and apply the reverse stress field to the body model of the target formed part according to the process path planned based on the shape and size of the target formed part, the selected shot peening process parameters, and experience to perform reverse simulation calculations, so as to obtain an initial unfolding model.

[0012] The reverse simulation method for obtaining an initial unfolding model for shot peening forming process provided by the present invention comprehensively considers the shape and size of the designed target formed part, the selected process parameters, and engineering experience, and can efficiently and accurately obtain an initial unfolding model through reverse simulation for use in subsequent machining and shot peening forming processes. Moreover, this method is different from the existing methods for obtaining an initial unfolding model. It does not simply flatten the target formed part directly based on experience, but comprehensively considers engineering experience, shot peening path, shot peening process parameters, and their equivalent induced stress, and fully takes into account the stretching effect during the shot peening forming process, thereby ensuring that an accurate initial unfolding model can be obtained.

[0013] In addition, this method abstracts the shot peening process parameters into an equivalent induced stress model and verifies it through the simulation and test of the Almen strip-like specimen, which further ensures the effectiveness and reliability of the obtained stress model and initial unfolding model. At the same time, the actual data of the shot peening process parameters can be correspondingly adjusted according to the adjusted equivalent induced stress model, so as to obtain the optimal shot peening process parameters.

[0014] According to an embodiment of the present invention, the reverse simulation method further includes performing mesh element division on the body model of the target formed part, and then applying the reverse stress field to the body model of the target formed part according to the planned process path to perform reverse simulation calculations. This method uses mesh division to promote simulation calculations, and by adjusting the size of the divided mesh elements, it can effectively balance the contradictory relationship between the granularity, accuracy, and simulation calculation amount of the simulation calculations.

[0015] According to an embodiment of the present invention, the reverse simulation method further includes using finite element simulation software to perform plane fitting based on the dimension data of the initial unfolding model to calculate the variance value between the dimension data and the fitting plane, and determining the initial unfolding model obtained when the variance value is within a preset range as a valid initial unfolding model.

[0016] According to the actual flatness requirement of the unfolding model, the method can further verify the validity of the obtained initial unfolding model by means of plane fitting. Specifically, the feasibility of the initial unfolding model is determined by the variance value between the dimension data and the ideal fitting plane. If the variance value is too large, it indicates that the obtained initial unfolding model is not flat enough, and thus it is considered invalid and cannot be effectively utilized further. Here, the variance value can be the average value of the variance values of all dimension data and the fitting plane.

[0017] According to an embodiment of the present invention, the dimension data includes the node position data of each grid unit in the initial unfolding model, where the node position data is the product of the node coordinate value data and the node weight factor.

[0018] According to an embodiment of the present invention, the node weight factor is positively correlated with the thickness value corresponding to its grid unit. The reverse simulation method comprehensively considers the engineering experience that in actual engineering practice, the forming accuracy of the thick plate area of the part is often required to be higher than that of the thin area. Based on engineering requirements, by adding a weight factor and making the thicker the plate, the greater the weight it occupies, that is, by making the node weight factor positively correlated with the thickness value corresponding to its grid unit, the theoretical simulation calculation is combined with actual engineering experience to ensure that the simulation does not deviate from reality, thereby further ensuring the accuracy of the obtained initial unfolding model.

[0019] According to an embodiment of the present invention, the planned process path includes multiple shot peening process paths, and the reverse simulation method further includes, for each shot peening process path, applying the reverse stress field to the body model of the target formed part according to the shot peening process path to perform reverse simulation calculation, so as to obtain multiple initial unfolding models. The reverse simulation method comprehensively considers actual engineering experience, analyzes the influence of the shot peening process path on the shot peening forming effect by obtaining multiple initial unfolding models corresponding to multiple shot peening process paths, and thereby obtains the optimal shot peening process parameters and shot peening process path.

[0020] According to an embodiment of the present invention, the reverse simulation method further includes sequentially performing plane fitting on multiple initial unfolding models to calculate the corresponding multiple variance values, determining the variance value that is within the preset range and the smallest by comparison, and then obtaining the optimal shot peening process parameters and shot peening process path according to the determined smallest variance value.

[0021] According to an embodiment of the present invention, the reverse simulation method further includes continuously adjusting the equivalent induced stress field model, the planned process path, and / or the mesh element size when the variance value exceeds a preset range until the variance value is within the preset range, so that the shot peening process parameters can be determined according to the adjusted equivalent induced stress field model.

[0022] The reverse simulation method determines the equivalent induced stress field and the shot peening process path, then divides the mesh elements of the body model of the target formed part, and then takes the inverse of the equivalent induced stress field and applies the inverted stress field to the body model of the target formed part after mesh element division, thereby constructing a reverse simulation finite element model that can be calculated and adjusted. In this way, by adjusting the elements in the reverse simulation finite element model, such as the equivalent induced stress field model, the process path, and / or the mesh element size, the reverse simulation finite element model of the model can be adjusted, so as to obtain an effective initial unfolding model obtained through simulation calculation. At the same time, the appropriate shot peening process parameters and shot peening process path can be determined through the adjusted equivalent induced stress field and process path.

[0023] According to an embodiment of the present invention, the reverse simulation method further includes applying a certain load around the planned process path to the initial unfolding model obtained by reverse simulation calculation to flatten the initial unfolding model.

[0024] According to an embodiment of the present invention, the reverse simulation method further includes machining according to the size of the obtained initial unfolding model to manufacture an initial unfolding blank that can be used for the shot peening forming process.

[0025] On the basis of conforming to the common knowledge in the art, the above preferred embodiments can be combined arbitrarily to obtain the preferred embodiments of the present invention.

[0026] The positive and progressive effects of the above embodiments of the present invention are as follows:

[0027] 1. This method can obtain an accurate, effective, and reliable initial unfolding model, and at the same time can determine the optimal shot peening process parameters and shot peening process path that match the unfolding model, so that a flattened blank can be machined and the target formed part can be shot peened and formed according to the process parameters and path that match the unfolding model;

[0028] 2. This method comprehensively considers the theoretical simulation model and practical engineering experience, takes the shot peening process parameters and shot peening process path into account in the process of obtaining the initial unfolding model, and designs a weight factor to participate in the simulation calculation and verification according to the difference in the forming effect of different thickness regions, so as to improve the accuracy and reliability of the initial unfolding model obtained by simulation calculation;

[0029] 3. This method can ensure the accuracy of the obtained initial unfolding model by establishing an equivalent induced stress field model of shot peening process parameters and verifying the established equivalent induced stress field with Almen-like strips. Meanwhile, it is convenient for users to find the optimized shot peening process parameters and shot peening process path more quickly and accurately, thus effectively improving the efficiency of the shot peening forming process. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 FIG. shows a flowchart of a reverse simulation method for obtaining an initial unfolding model for a shot peening forming process according to a preferred embodiment of the present invention.

[0031] Figure 2A FIG. shows a schematic diagram of an equivalent induced stress field model constructed by the reverse simulation method according to a preferred embodiment of the present invention.

[0032] Figure 2B FIG. shows a schematic diagram of the inverted equivalent induced stress field model constructed by the reverse simulation method according to a preferred embodiment of the present invention.

[0033] Figure 3A FIG. shows a schematic diagram of the body model of the target formed part in the reverse simulation method according to a preferred embodiment of the present invention.

[0034] Figure 3B FIG. shows a schematic diagram of the initial unfolding model obtained by the reverse simulation method according to a preferred embodiment of the present invention.

[0035] Figure 4A FIG. shows a schematic diagram of the body model of the target formed part generated by the reverse simulation method according to a preferred embodiment of the present invention.

[0036] Figure 4B FIG. shows a schematic diagram of applying a reverse stress field according to the planned process path by the reverse simulation method according to a preferred embodiment of the present invention.

[0037] Figure 4C FIG. shows a schematic diagram of the initial unfolding model obtained by the reverse simulation method according to a preferred embodiment of the present invention.

[0038] Figure 5 FIG. shows a flowchart of a reverse simulation method according to another preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0039] To make the objectives, technical solutions, and advantages of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings showing multiple embodiments according to this application. It should be understood that all other embodiments obtained by those of ordinary skill in the art based on the embodiments described in this application without creative efforts will fall within the scope of protection of this application.

[0040] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms "including", "having", etc. in the description and claims of this application and the above description of the accompanying drawings are open-ended terms. Therefore, "including", "having", for example, one or more steps, has one or more steps, but is not limited to only having these one or more steps.

[0041] In the shot peening forming process, the process parameters of shot peening forming (e.g., shot peening speed, shot type, shot peening pressure, shot flow rate) and the shot peening process path will directly affect the forming effect of the part. At present, the shot peening process parameters and process path planning for complex parts are mainly determined manually based on engineering experience. In order to systematically analyze the shot peening process parameters and process path, based on existing research, the finite element method can be combined, and by constructing an equivalent induced stress field of the shot peening process parameters, the expansion effect of shot peening forming can be introduced into the part model, so that the finite element model of the part generates corresponding deformation, and then compared with the actual target model to determine whether the process parameters or process path are reasonable and effective.

[0042] Generally speaking, the model obtained by process developers is the model of the final target part, and the model of the target part often has a complex curved shape. When planning the shot peening process parameters and process path for the target part, a reliable flattened blank needs to be obtained first, and then the process planning is carried out based on the flattened blank. At present, the "one-step method" of the finite element method is mainly used in the industry for blank flattening.

[0043] However, the "one-step method" is a pure geometric flattening method, that is, the curved panel is "pressed" flat, and the flattened part model is used as the initial blank, and then the shot peening parameters and process path are planned. The flattening based on the "one-step method" ignores the extension effect brought by the process, especially for the shot peening forming process that relies on material extension to achieve deformation. This kind of flattening without considering the process is often inaccurate, and subsequent corrections to the flattened parts still need to be carried out by trial and error, which is time-consuming and laborious. Moreover, for shot peening forming, part flattening and process planning are often interrelated, that is, the flattening result needs to be corrected based on the extension under a certain process, and the determination of process parameters and process path needs to be planned based on an effective flattened blank.

[0044] Therefore, there are the following two obvious problems in the current shot peening forming process and simulation process.

[0045] 1. Currently, the traditional flattening method is adopted, and an accurate flattening model associated with the shot peening forming process cannot be obtained. The current simulation analysis of shot peening forming is mainly "forward simulation". The so-called "forward simulation" mainly means that according to the given flat blank model, an equivalent induced stress field is applied to the surface of the flat blank model, so that the flat blank model generates an expansion effect similar to shot peening forming, so that the model deforms, and further analysis can be carried out.

[0046] However, the "forward simulation" method requires a reliable flattened flat model to be provided in advance, and how to obtain the model of the reliable flat blank itself is one of the difficulties of the shot peening forming process. At present, in the industry, in addition to relying on process experience, a feasible method is to use finite element software (such as hyperform) for "one-step" flattening. However, the "one-step" flattening method is only a simple geometric flattening, completely ignoring the "extension effect" of the part after shot peening, and even more ignoring that the "extension effect" will make the size of the part after shot peening larger than that before shot peening. Therefore, the initial unfolded model obtained by this method lacks engineering significance to a certain extent.

[0047] 2. The currently adopted "forward simulation" method cannot provide an evaluation standard that can be quickly quantified for the simulation results after shot peening forming, that is, it is impossible to quickly evaluate whether the simulation results after deformation are correct and effective in the simulation software, and thus it is also impossible to judge the effectiveness of flattening. Taking the "forward simulation" shot peening forming process proposed above as an example, after simulation calculation, the geometric shape of the part manufactured according to the simulation results needs to be compared and analyzed with the model of the target part. Since the model shapes of the parts are different, it is very difficult to propose a unified method to measure the matching degree between the shapes of different parts obtained under different simulation schemes and the part models. Moreover, it is basically infeasible to further realize the automatic iterative optimization analysis of the process based on the evaluation results.

[0048] Therefore, at least for the above technical problems, the present invention provides a reverse simulation method for obtaining an initial unfolded model for the shot peening forming process, which can effectively solve the determination of shot peening process parameters and the flattening of the model based on the process parameters, that is, obtain the initial unfolded model at the same time. Through this reverse simulation method, the automatic screening and planning of the shot peening forming process plan can be realized, and at the same time, an initial unfolded model matching the process plan can be obtained. Moreover, by using the automatically screened and planned shot peening forming process plan to perform shot peening forming on the obtained initial unfolded model, the target formed part can be obtained.

[0049] Generally speaking, the main concept of the reverse simulation method for obtaining the initial unfolding model used in the shot peening forming process includes: establishing a corresponding model based on the target part, loading a reverse equivalent induced stress field onto the target part model, causing the material at the loading location to undergo corresponding reverse deformation, and gradually flattening the originally curved part under this effect. In actual operation, according to the model generated under a certain shot peening process parameter during the previous analysis process, without changing the equivalent induced stress field model, reverse it, that is, change the compressive stress to tensile stress and the tensile stress to compressive stress. In this way, after applying the reverse stress field, it will generate deformation in the opposite direction to the initial equivalent induced stress field, thereby realizing the shrinkage effect of the target formed part. At the same time, the area where the reverse equivalent induced stress field is applied is the actual shot peening area, and the planned process path is the actual process path. In addition, based on the shrinkage effect of the surface material achieved after reversing the stress field, the extension correction of the flattened initial unfolding model can be obtained.

[0050] Specifically, as Figure 1 shown, the reverse simulation method for obtaining the initial unfolding model used in the shot peening forming process according to the preferred embodiment of the present invention includes:

[0051] Step 1: Based on the actual digital model of the target formed part, use computer software to generate the body model of the target formed part;

[0052] Step 2: Use computer software to generate an Almen strip-like model consistent with the material constitutive of the part, and apply the stress field to the Almen strip-like model in the finite element simulation software to perform simulation deformation calculation. Among them, the stress field corresponds to specific shot peening process parameters. During this period, continuously correct the stress field model until the calculated deformation is consistent with the deformation of the Almen strip after shot peening forming test under the corresponding selected shot peening process parameters, thereby determining the equivalent induced stress field model corresponding to the selected shot peening process parameters;

[0053] Step 3: Use the finite element simulation software to perform a reverse operation on the equivalent induced stress field model to obtain a reverse stress field, and apply the reverse stress field to the part body model according to the process path planned based on the shape of the target formed part and the selected shot peening process parameters and according to experience to perform reverse simulation calculation, thereby obtaining the initial unfolding model.

[0054] In Step 1, the actual digital model of the target formed part can be directly used to quickly convert it into the body model of the target formed part in the finite element simulation software for further simulation calculation.

[0055] In Step 2, the equivalent induced stress field model can usually be expressed as a polynomial function varying along the thickness h of the part, which can be expressed by the following formula (1):

[0056]

[0057]

[0058]

[0059] Among them, p i and q j respectively represent the elements to be fitted in the polynomial, and m and n are the number of terms of p i and q j . p i and q j have a certain mapping relationship with the shot peening process parameters such as shot flow rate, shot peening pressure, and shot peening distance in the shot peening process, specifically expressed as Formula (2) and Formula (3), where is the shot flow rate, p is the shot peening pressure, and d is the shot peening distance.

[0060] During the simulation process, from the shot peened surface layer along the thickness direction downwards, its equivalent induced stress field model is generally a "compression - tension" model. Since the equivalent induced stress field model of the shot peening process parameters is obtained through explicit analysis, the mesh nodes around the affected area generally restrict the movement of the nodes. Therefore, from the thickness direction, the overall stress field state shown by the "compression - tension" stress field model is a "compression" stress state. If the "compression - tension" stress field model with the overall "compression" stress state is imported into the mesh model with a 0 stress state, then the overall stress state shown by the mesh model is a "compression" stress state. When the mesh model has no restraint, it will release the internal stress by the way of "elongating", thus showing the phenomenon of "the part getting longer". In this way, the obtained result also conforms to the phenomenon of part elongation existing in the shot peening process.

[0061] In Step 2, assume that the body model of the given target formed part is as Figure 3A shown, and the overall length of the model is 1 m. Before the simulation, first complete the construction of the equivalent induced stress field model under different process parameters according to the method described above. At the same time, pre - verify the effectiveness and reliability of the equivalent induced stress field according to the Almen strip or even the test pieces at the typical part level. The verified equivalent induced stress field model is as Figure 2A shown.

[0062] Then, in Step 3, perform an inversion operation on the verified equivalent induced stress field, that is, the tensile stress becomes compressive stress and the compressive stress becomes tensile stress, to obtain as Figure 2BThe reverse equivalent induced stress field model shown. Preferably, the reverse simulation method further includes first dividing the mesh elements of the part body model, and then applying the reverse stress field to the part body model according to the planned process path for reverse simulation calculation, and its specific process is described below.

[0063] Specifically, an inversion operation is performed on the original equivalent induced stress model, that is, the "compression-tension" stress model, that is, the formula (1) is inverted. The inverted stress field model can be represented by σ in formula (4). ind At this time, the "compression-tension" stress model becomes a "tension-compression" stress model, and the overall performance of the "tension-compression" stress model is a "tension" stress state. When imported into the mesh model in the 0 stress state, the phenomenon of "part shortening" will occur.

[0064]

[0065] Exemplarily, the length of the target formed part model is 1m. Considering the ductility of shot peening forming, the initial unfolded model (i.e., the flat blank model) after reverse simulation calculation is as Figure 3B shown, with a total length of 0.95m. A flat blank part of 0.95m is machined according to the initial unfolded model. After shot peening forming of this flat blank part, not only is the outer shape of the flat blank part consistent with the target part, but the total length after shot peening extension also exactly reaches 1m, and at this time, the theoretically most perfect shot peening forming result is achieved.

[0066] Furthermore, the reverse simulation method can also include using finite element simulation software to calculate the variance value between the size data and the fitting plane by performing plane fitting according to the size data of the initial unfolded model. The initial unfolded model obtained when the variance value is within the preset range is determined as a valid initial unfolded model, where the size data can include the node position data of each mesh element in the initial unfolded model. After the simulation calculation is completed to obtain the initial unfolded model, the node coordinate values of all elements of the model and the thickness values at their corresponding element positions can be obtained. All the node coordinate values are fitted into a plane. After obtaining the plane equation by fitting, the corresponding variance value σ will be obtained, and this variance σ can be used to characterize the flatness of the initial unfolded model after "flattening". The lower the variance σ, the flatter it indicates.

[0067] And among them, the node position data of each grid cell is the product of its node coordinate value data and the node weight factor, where the node weight factor is positively correlated with the thickness value corresponding to its grid cell. During the fitting process, the specific correlation relationship between the weight of the node coordinate value and the thickness value corresponding to that node can be determined according to the actual engineering requirements. For example, the weight can be determined according to the square of the thickness. As for the specific functional representation relationship between the weight factor and the thickness, it can be decided according to the actual on-site requirements.

[0068] The reason for adopting the weight factor is that in actual engineering practice, it is found that the forming accuracy of the thick area of the part is often required to be higher than that of the thin area. Therefore, based on this engineering requirement, the following weight factor can be considered, that is, the thicker the board, the greater the weight it occupies. This weight-based flatness evaluation method is to obtain the coordinate values of the grid cell nodes in all initial unfolding models after the simulation calculation is completed, perform weight-based plane fitting on these points, and finally evaluate the flatness of the "flattened" part through the fitting variance, thereby obtaining an effective initial unfolding model.

[0069] Meanwhile, when the variance value exceeds the preset range, continuously adjust the equivalent induced stress field model, the planned process path, and / or the grid cell size until the variance value is within the preset range, so that the shot peening process parameters can be determined according to the adjusted equivalent induced stress field model.

[0070] Optionally, the planned process path can include multiple shot peening process paths, and the reverse simulation method further includes, for each shot peening process path, as Figure 4A - 4C shown, applying the reverse stress field F to the part body model as Figure 4A shown to perform reverse simulation calculation to obtain the initial unfolding model as Figure 4C shown, so as to obtain multiple initial unfolding models. At this time, the reverse simulation method further includes sequentially performing plane fitting on the multiple initial unfolding models to calculate the corresponding multiple variance values, determining the variance value that is within the preset range and the smallest through comparison, and then obtaining the optimal shot peening process parameters and shot peening process path according to the determined smallest variance value.

[0071] Alternatively, as Figure 5As shown, the reverse simulation method according to the preferred embodiment of the present invention may further include generating a candidate process plan according to the process planning, where the process plan includes an equivalent induced stress field model, a planned process path plan, etc.; constructing a finite element mesh model for the target part, and according to the generated candidate process plan, establishing a corresponding finite element reverse simulation model by taking the inverse operation of the equivalent induced stress field; for these planned candidate process plans, performing iterative simulation analysis on the basis of the constructed finite element model, and the result of each analysis will feedback a variance value of plane fitting; according to the variance values of many plans, selecting the optimal combination of process parameters and shot peening process path; based on the selected optimal combination of process parameters and shot peening process path plan, obtaining the unfolding result of the corresponding target formed part.

[0072] Moreover, when the variance value does not meet the preset range, adjust the finite element reverse simulation model until the variance value is within the preset range. Preferably, around the planned process path, apply a certain load to the initial unfolding model obtained by reverse simulation calculation to flatten the initial unfolding model, so as to prevent the deformation of the area without the applied stress field from affecting the calculation structure. Complementarily, considering that in the actual shot peening forming process, the forming accuracy of the thick area is more important than that of the thin area. In the actual process, the thin area can be leveled by applying a certain standard external load, thereby avoiding the influence of the thin area on the variance value calculation.

[0073] The flattened model obtained under the reverse equivalent induced stress field is the initial unfolding model, the process parameters corresponding to the reverse equivalent induced stress field are the actual shot peening process parameters, the stress field application process path is the actual shot peening process path, and the flattened model is the flattened model corresponding to the shot peening parameters and the shot peening process path. The reverse simulation method in the present invention obtains the flattened model considering process extension and the corresponding process plan through reverse simulation, so as to obtain an accurate and effective shot peening forming result.

[0074] Based on the empirical analysis of the geometric shape of the target formed part, the reverse simulation method can obtain the initial shot peening process path, and then apply the reverse equivalent induced stress field to the body model of the target formed part according to the planned shot peening process path. As the simulation iterative calculation progresses, the model will gradually tend to be flat and finally tend to a flat plate. Due to the shrinkage effect after the application of the reverse equivalent induced stress field, the length of the part will also shorten after being flattened. In the case where the equivalent induced stress field model has no error and the shot peening process path is exactly the optimal trajectory, machining can be carried out according to the size of the obtained initial unfolding model to manufacture the original part provided for the shot peening forming process, and the part can obtain the target formed part after being processed by the shot peening forming process.

[0075] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that these are only examples. The protection scope of the present invention is defined by the appended claims. Without departing from the principles and essence of the present invention, those skilled in the art can make various changes or modifications to these embodiments, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. An inverse simulation method for obtaining an initial unfolding model for a shot peening forming process, characterized in that, The reverse simulation method includes the following steps: Based on the actual digital model of the target formed part, use computer software to generate the body model of the target formed part; Use the computer software to generate an Almen strip-like model consistent with the body model of the target formed part, and apply a stress field to the Almen strip-like model in the finite element simulation software for simulation deformation calculation. Among them, continuously adjust the magnitude of the stress field until the calculated deformation is consistent with the deformation of the Almen strip after the shot peening forming test under the selected shot peening process parameters, thereby determining the equivalent induced stress field model corresponding to the selected shot peening process parameters; Use the finite element simulation software to perform an inversion operation on the equivalent induced stress field model to obtain a reverse stress field, and apply the reverse stress field to the body model of the target formed part according to the process path planned based on the shape and size of the target formed part, the selected shot peening process parameters, and experience for reverse simulation calculation, so as to obtain an initial unfolded model.

2. The reverse simulation method according to claim 1, wherein The reverse simulation method further includes: Perform mesh element division on the body model of the target formed part, and then apply the reverse stress field to the body model of the target formed part after mesh element division according to the planned process path for reverse simulation calculation.

3. The reverse simulation method according to claim 2, wherein The reverse simulation method further includes: In the finite element simulation software, perform plane fitting according to the size data of the initial unfolded model to obtain the variance value between the size data and the fitting plane. Among them, when the variance value is within a preset range, the obtained initial unfolded model is determined as a valid initial unfolded model.

4. The reverse simulation method according to claim 3, wherein The size data includes the node position data of each mesh element in the initial unfolded model, where the node position data is the product of the node coordinate value data and the node weight factor.

5. The reverse simulation method according to claim 4, characterized in that The node weight factor is positively correlated with the thickness value corresponding to its mesh element.

6. The reverse simulation method according to claim 3, wherein The planned process path includes multiple shot peening process paths, and the reverse simulation method further includes: For each shot peening process path, apply the reverse stress field to the body model of the target formed part after mesh element division according to the shot peening process path for reverse simulation calculation, so as to obtain multiple initial unfolded models.

7. The reverse simulation method according to claim 6, characterized in that, The reverse simulation method further includes: Perform plane fitting on the multiple initial unfolded models in sequence to calculate the corresponding multiple variance values, determine the variance value that is within the preset range and is the smallest through comparison, and then obtain the optimal shot peening process parameters and shot peening process path according to the determined smallest variance value.

8. The reverse simulation method according to claim 3, characterized in that The reverse simulation method further includes: When the variance value exceeds the preset range, continuously adjust the equivalent induced stress field model, the planned process path, and / or the mesh element size until the variance value is within the preset range, so that the shot peening process parameters can be determined according to the adjusted equivalent induced stress field model.

9. The reverse simulation method according to claim 1, wherein The reverse simulation method further includes: Apply a certain load around the planned process path to the initial unfolded model obtained by reverse simulation calculation to flatten the initial unfolded model.

10. The reverse simulation method according to any one of the preceding claims 1 to 9, characterized in that, The reverse simulation method further includes: Machining is performed according to the dimensions of the obtained initial unfolding model to manufacture an initial flattened blank that can provide an initial flattened blank for shot peening forming.

Images