A deformation prediction method for a weakly rigid pure copper planar component under time-varying multi-factors

Abstract

The present invention discloses a deformation prediction method for a weakly rigid pure copper planar component under time-varying multi-factors, comprising the following steps: S1. Establish a prediction method for stress-induced deformation during the processing of a pure copper planar component. Through rolling numerical simulation, a stress-deformation simulation model of a weakly rigid pure iron curved surface component is established for simulation to obtain an initial internal stress field. Then, the internal stress is regulated through heat treatment, and finally, the birth and death elements are used for the material removal process to obtain the influence of the internal stress evolution on deformation; S2. Alternately remove the material allowance on the upper and lower surfaces of the planar component in the simulation model to simulate the entire process of actual turning processing; S3. Explore the deformation forms of the pure copper planar component during processing under two machining methods of constant linear velocity cutting and constant rotational speed cutting, and further explore the influence law of cutting parameters on the deformation of the pure copper planar component in the precision machining stage; S4. Analyze the deformation amount under the action of vacuum adsorption clamping and the magnitude of the residual stress generated on the workpiece surface due to clamping.

Description

Technical Field

[0001] The present invention belongs to the technical field of precision machining, and particularly relates to a method for predicting deformation of a weak-rigidity pure copper planar component under time-varying multi-factors. Background Art

[0002] In modern manufacturing technology, the precision machining of weak-rigidity materials faces many challenges, especially for materials such as pure copper planar components with significant plastic deformation characteristics. Traditional machining methods often struggle to balance material removal efficiency and the shape accuracy of the final workpiece. Therefore, there is an urgent need to develop new deformation prediction and control technologies to achieve high-precision and high-stability machining effects.

[0003] When machining the pure copper surface, first through multiple passes of rolling, as the number of rolling passes increases, the stress amplitude increases. After recrystallization annealing, its stress amplitude is reduced. Through quenching, the internal stress is made uniform in the plane and symmetric along the depth direction. After stress relief annealing, the stress amplitude after quenching is reduced. During the machining process, multiple passes of heat treatment are used to control the internal stress of the material. However, there is still a large internal stress in the machining deformation of this heat treatment, which needs to be controlled.

[0004] Due to the poor rigidity of pure copper thin-walled components with a large diameter-thickness ratio, they are prone to large deformation under the action of a non-uniform machining stress field. Combining the influence law of cutting speed on the machining deformation of pure copper planar components, it can be known that the machining deformation under constant rotational speed is distributed in a central-symmetric ring shape, and the position of its deformation extreme value is related to the position of the cutting-in point. In the precision machining stage, the maximum deformation amount generated by machining residual stress is much smaller than the machining deformation caused by internal stress. In the case of constant linear speed machining, the deformation is basically uniformly distributed, but there is inevitably a local depression at the center of the workpiece due to non-constant speed machining. Therefore, reasonably planning the maximum limiting rotational speed during constant linear speed machining is the key factor in coordinating the overall deformation of the workpiece. The constant linear speed machining method is more likely to obtain better machining accuracy compared to the constant rotational speed machining method. The machining deformation decreases with the increase of the spindle speed, increases with the increase of the cutting depth, and increases with the increase of the feed rate. In order to effectively control the machining deformation of weak-rigidity pure copper planar and pure iron curved surface components, it is necessary to control the stress state of the target component throughout the manufacturing cycle. Therefore, reducing the machining residual stress introduced by cutting can effectively improve the surface shape accuracy of pure copper planar and pure iron curved surface components.

[0005] Due to the initial surface shape error of the weakly rigid planar component, there is a certain clearance between the workpiece and the fixture. When the vacuum chuck is used for clamping, the workpiece is mainly subjected to a load perpendicular to the thin-walled component, causing the workpiece to bend and deform. Since the clearance between the workpiece and the fixture is generally in the range of several micrometers to dozens of micrometers, the deflection of the thin-walled planar component caused by the vacuum clamping force is much less than 1 / 5 of the plate thickness, and it can be analyzed as a small deflection bending problem of thin plates in elastic mechanics. It can be known the deformation amount of the workpiece under different vacuum adsorption effects and the magnitude of the residual stress generated on the workpiece surface due to clamping. The thickness h of the workpiece will affect the bending stiffness D of the workpiece, and thus affect the deformation amount of the workpiece. The clamping deformation increases with the increase of the clamping stress, showing a linear relationship; the clamping deformation decreases with the increase of the workpiece thickness and gradually tends to be stable, showing an exponential relationship; the clamping deformation increases with the increase of the suction hole diameter and the suction groove width, and the growth rate gradually increases; the clamping deformation and the positions of the suction holes and suction grooves are in a non-linear relationship, and it is easier to obtain a smaller clamping deformation when the positions of the suction holes and suction grooves are close to the outer edge of the workpiece. Although vacuum adsorption clamping is stable and reliable, the initial surface shape error is difficult to eliminate through subsequent processing, and there is also the problem of excessive deformation after unloading. In the final stage of precision machining, vacuum adsorption clamping has been difficult to meet the machining accuracy requirements. Summary of the Invention

[0006] The object of the present invention is to solve the above problems, and provide a method for predicting the deformation of a weakly rigid pure copper planar component under the action of time-varying multi-factors with high efficiency and high stability by establishing a comprehensive stress model to analyze the influence of factors such as internal stress, machining residual stress and clamping stress on deformation, and combining numerical simulation and experimental verification.

[0007] To solve the above technical problems, the technical solution of the present invention is: a method for predicting the deformation of a weakly rigid pure copper planar component under time-varying multi-factors, including the following steps:

[0008] S1. Establish a prediction method for the deformation induced by internal stress in the machining process of the pure copper planar component. Through rolling numerical simulation, a stress-deformation simulation model of the weakly rigid pure iron curved surface component is established for simulation. The initial internal stress field is obtained by simulation, and then the internal stress is regulated through heat treatment. Finally, the birth and death elements are used for the material removal process to obtain the influence of the internal stress evolution on the deformation.

[0009] S2. Considering the turning machining process in the actual cutting of the planar component, the material allowance on the upper and lower surfaces of the planar component is alternately removed in the simulation model to simulate the entire process of the actual turning machining.

[0010] S3. Establish a machining residual stress prediction model, combine the influence law of the cutting speed on the machining deformation of the pure copper planar component, explore the machining deformation forms of the pure copper planar component under two machining methods of constant linear speed cutting and constant rotational speed cutting, and further explore the influence law of the cutting parameters on the deformation of the pure copper planar component in the precision machining stage.

[0011] S4. Establish a vacuum clamping stress and deformation prediction model to analyze the deformation amount under the action of vacuum adsorption clamping and the magnitude of the residual stress generated on the workpiece surface due to clamping.

[0012] Furthermore, the initial internal stress field obtained in step S1 is based on stress reconstruction and annealing simulation to obtain the internal stress field of the pure copper planar component, and the stress loading under refined meshes is achieved through a mapping algorithm.

[0013] Furthermore, in step S1, the material removal process using birth and death elements is based on the established stress and deformation simulation model of the weakly rigid pure iron curved surface component. The element birth and death technology is used to simulate the real material removal process, and the internal stress and the evolution law of deformation under the action of internal stress during the material removal process of the planar component are obtained.

[0014] Furthermore, the heat treatment for regulating internal stress in step S1 is to control the internal stress of the material by using multi-pass heat treatment during the machining process of the pure copper planar component. Heat treatment is required after rough machining and semi-finishing.

[0015] Furthermore, the internal stress of the pure copper material is regulated by a process combining cryogenic treatment and annealing. The cryogenic treatment is arranged between two heat treatments.

[0016] Furthermore, the optimization method of cutting parameters in step S3 is an optimization method of cutting parameters for minimizing machining residual stress. A sample set is established based on finite stress detection data, and a mapping relationship is constructed using the support vector regression method, which greatly improves the calculation efficiency.

[0017] Furthermore, the vacuum clamping stress and deformation prediction model in step S4 is based on a low-stress clamping strategy of local bonding clamping. Multi-point bonding fixation is achieved by using hot-melt adhesive through the local bonding method to reduce the deformation of the workpiece after machining.

[0018] The beneficial effects of the present invention are as follows: The deformation prediction method for a weakly rigid pure copper planar component under time-varying multi-factors provided by the present invention can effectively predict and control the deformation of the weakly rigid pure copper planar component under the action of time-varying multi-factors, improve the machining accuracy and stability, reduce the deformation during the machining process, is applicable to the field of precision machining, and has a wide application prospect. Description of the Drawings

[0019] Figure 1 It is a schematic diagram of the influence of the stress evolution of a pure copper planar component during the full manufacturing cycle on its deformation in the deformation prediction method for a weakly rigid pure copper planar component under time-varying multi-factors of the present invention;

[0020] Figure 2 It is a schematic diagram of the internal stress field of the pure copper planar component of the present invention;

[0021] Figure 3 This is the stress evolution process in the pure copper planar component of the present invention;

[0022] Figure 4 This is the deformation evolution process under the action of internal stress in the pure copper curved component of the present invention;

[0023] Figure 5 This is the machining deformation distribution caused by the machining residual stress of the present invention;

[0024] Figure 6 This is the influence of the cutting parameters of the present invention on the machining deformation;

[0025] Figure 7 This is the schematic diagram of vacuum adsorption and local point bonding clamping for the thin-walled planar part of the present invention. Detailed implementation manners

[0026] The following further describes the present invention in conjunction with the accompanying drawings and specific embodiments:

[0027] As Figures 1 to 7 shown, a deformation prediction method for a time-varying multi-factor weak-rigidity pure copper planar component provided by the present invention includes the following steps:

[0028] S1. Establish a prediction method for stress-induced deformation in the machining process of a pure copper planar component. Through rolling numerical simulation, a stress-deformation simulation model of a weak-rigidity pure copper curved component is established for simulation. The initial internal stress field is obtained through simulation, and then the internal stress is regulated by heat treatment. Finally, the birth and death element method is used for the material removal process to obtain the influence of internal stress evolution on deformation.

[0029] In this step, the initial internal stress field is obtained based on stress reconstruction and annealing simulation of the pure copper planar component, and stress loading under refined meshes is achieved through a mapping algorithm.

[0030] In this step, the birth and death element method for the material removal process is based on the established stress-deformation simulation model of the weak-rigidity pure iron curved component. The element birth and death technique is used to simulate the real material removal process to obtain the internal stress and the deformation evolution law under the action of internal stress during the material removal process of the planar component. As Figure 2 shown, Figure 2 This is the internal stress state when the plate thickness of the planar component is 3.6 mm.

[0031] In this step, the heat treatment for regulating internal stress is to control the internal stress of the material by adopting multi-pass heat treatment during the machining process of the pure copper planar component. Heat treatment is required after rough machining and semi-finishing.

[0032] The internal stress of the pure copper material is regulated by a process combining cryogenic treatment and annealing. The cryogenic treatment is arranged between two heat treatments.

[0033] Regarding the selection of process parameters for the existing cryogenic and high-temperature aging composite treatment, the influence brought by the single cryogenic treatment is very small, and it is generally combined with other heat treatment processes. Therefore, the present invention adopts the process of combining cryogenic treatment and annealing to regulate the internal stress of pure copper materials. The cryogenic treatment is arranged between two heat treatments. The conditions of the heat treatment remain constant, and annealing is carried out at 973K for 2H, followed by furnace cooling. The heat treatment process is carried out in a non-vacuum furnace. However, the conditions of the cryogenic treatment will change. The low-temperature treatment is carried out under the domestic equipment SL-500. The L9(43) orthogonal test table of four factors and three levels is used to design the experiment. The cryogenic temperature, holding time, and heating and cooling rates of the workpiece are used as control variables, and the internal stress of the specimen after cold / heat treatment is used as the response characteristic. The temperature range of the low-temperature treatment is 77-193K, the holding time is 8-24h, the cooling rate is 2-6k / min, and the tempering rate is 0.5-2k / min. Through the end face turning experiment method, the machining deformation laws caused by the internal stress of the test pieces with a thickness of 1.2mm after annealing at 300°C for 72 hours and after the combined action of annealing at 300°C and cryogenic treatment are compared and studied. The test shows that the cutting deformation of the test pieces with cryogenic composite treatment is much lower than that of the test pieces with only annealing treatment.

[0034] S2. Considering the turning-over machining process in the actual cutting of plane components, the material allowance on the upper and lower surfaces of the plane component is alternately removed in the simulation model to simulate the entire process of the real turning-over machining.

[0035] As Figure 3 and Figure 4 shown, in this embodiment, the material allowance on the upper and lower surfaces of the plane component is alternately removed in the simulation model to simulate the entire process of the real turning-over machining, and the plane component is finally thinned from a plate thickness of 3.6mm to 2.4mm. The change in the internal stress state during the turning-over machining process of the component and the deformation change under the action of the internal stress during the turning-over machining process of the pure copper plane component.

[0036] Figure 3 In (a), it represents the internal stress state diagram of the pure copper plane component with a plate thickness of 3.2mm, (b) represents the internal stress state diagram of the pure copper plane component with a plate thickness of 2.8mm, and (c) represents the internal stress state diagram of the pure copper plane component with a plate thickness of 2.4mm.

[0037] Figure 4 In (a), it represents the internal stress state diagram of the pure copper curved surface component with a plate thickness of 3.2mm, (b) represents the internal stress state diagram of the pure copper curved surface component with a plate thickness of 2.8mm, and (c) represents the internal stress state diagram of the pure copper curved surface component with a plate thickness of 2.4mm.

[0038] S3. Establish a prediction model for machining residual stress. Combining the influence law of cutting speed on the machining deformation of pure copper planar components, explore the machining deformation forms of pure copper planar components under two machining methods of constant linear speed cutting and constant rotational speed cutting, and further explore the influence law of cutting parameters on the deformation of pure copper planar components in the precision machining stage.

[0039] The optimization method of cutting parameters in step S3 is an optimization method of cutting parameters for minimizing machining residual stress. A sample set is established based on limited stress detection data, and a mapping relationship is constructed using the support vector regression method, greatly improving the calculation efficiency.

[0040] S4. Establish a prediction model for vacuum clamping stress deformation, and analyze the deformation amount under the action of vacuum adsorption clamping and the magnitude of residual stress generated on the workpiece surface due to clamping.

[0041] The vacuum clamping stress deformation prediction model in step S4 is a low-stress clamping strategy based on local bonding clamping. Through the local bonding method, hot melt adhesive is used to achieve multi-point bonding and fixation, reducing the deformation of the workpiece after machining.

[0042] Through the subroutine SIGINI in ABAQUS, considering the variable cutting speed cutting process in the full-region machining of pure copper planar components, combined with the established prediction model for machining residual stress of pure copper materials, the variable machining residual stress field in the full-region machining process of pure copper planar components is reconstructed based on two-dimensional linear interpolation, and the above variable machining residual stress field is applied to the pure copper planar component as the initial condition. By analyzing the displacement of the nodes on the upper surface of the workpiece under the action of the equivalent stress field, the machined surface shape of the pure copper planar component under the action of machining residual stress is obtained. As Figure 5 and Figure 6 shown, it shows that the machining deformation under constant rotational speed is distributed in a central symmetric ring shape, and the position of its deformation extreme value is related to the position of the cutting-in point. In the precision machining stage, the maximum deformation amount generated by machining residual stress is much smaller than the machining deformation caused by internal stress. The machining deformation under constant linear speed is basically uniformly distributed, but there is inevitably a local depression at the center of the workpiece due to non-constant speed machining. Therefore, reasonably planning the maximum limited rotational speed during constant linear speed machining is the key factor to coordinate the overall deformation of the workpiece. And the constant linear speed machining method is more likely to obtain better machining accuracy than the constant rotational speed machining method. The machining deformation decreases with the increase of the spindle speed, increases with the increase of the cutting depth, and increases with the increase of the feed rate.

[0043] Figure 5 In, (a) represents the machining deformation distribution diagram under constant rotational speed, and (b) represents the machining deformation distribution diagram under constant linear speed. Figure 6 In (a) represents the influence curve diagram of the spindle speed on the deformation, (b) represents the influence curve diagram of the cutting depth on the deformation, and (c) represents the influence diagram of the feed rate on the deformation.

[0044] For the semi-finishing stage where machining residual stress is dominant, first determine the range of cutting parameters, and then apply the support vector regression algorithm to establish non-linear models of surface residual stress in the cutting and feed directions with respect to cutting speed, feed rate, and cutting depth. The specific process is as follows: Divide the input-response data set into a fitting group and a validation group, and normalize the values of each cutting parameter and the surface residual stress in the cutting and feed directions to the interval [-1, 1]; Iteratively optimize the parameters in the support vector regression model; Based on the obtained parameters, establish a support vector regression (SVR) model of surface residual stress in the cutting and feed directions; Use the validation data set to evaluate the prediction accuracy of the SVR models in the cutting and feed directions. Based on the established SVR models of surface residual stress in the cutting and feed directions, with the goal of minimizing surface residual stress, use the improved particle swarm algorithm to obtain the optimal cutting process parameters.

[0045] For the deformation prediction of vacuum clamping stress of weakly rigid planar components, the deflection of thin-walled planar parts caused by the vacuum clamping force is much less than 1 / 5 of the plate thickness, and it can be analyzed as a small deflection bending problem of thin plates in elastic mechanics. According to the straight normal assumption, mid-surface displacement assumption, and no extrusion assumption in the plate proposed by Kirchhoff, the small deflection bending displacement components of the thin plate can be calculated. Then, by comprehensively using the geometric equation and physical equation, the stress components can be obtained; Simplify the stress components on the side surface of the plate to the mid-surface to obtain the distributed bending moment, torque, and distributed shear force acting on the mid-line of the side surface of the plate; According to the equilibrium conditions of the microelement, write the equilibrium differential equation expressed by internal force components by writing the equilibrium equation of forces in the z direction and the moment equilibrium equations about the x-axis and y-axis respectively; According to the above mechanical model, the deformation amount of the workpiece under different vacuum adsorption effects and the magnitude of the residual stress generated on the workpiece surface due to clamping can be calculated. The size of the workpiece thickness h will affect the flexural rigidity D of the workpiece, and thus affect the deformation amount of the workpiece. The calculation results show that the clamping deformation increases linearly with the increase of the clamping stress; The clamping deformation decreases with the increase of the workpiece thickness and gradually tends to be stable, showing an exponential relationship; The clamping deformation increases with the increase of the suction hole diameter and suction groove width, and the growth rate gradually increases; The clamping deformation and the positions of the suction holes and suction grooves have a non-linear relationship. When the positions of the suction holes and suction grooves are close to the outer edge of the workpiece, it is easier to obtain smaller clamping deformation.

[0046] Such as Figure 7As shown, the local bonding method uses hot melt adhesive to achieve multi-point bonding and fixation. Most of the components are in a free state, and the surface shape can be corrected through subsequent processing. Moreover, the unbalanced stress caused by material removal is redistributed during the processing. Therefore, the deformation after unloading is small, making it suitable for the final allowance removal stage of precision machining. Combining with the deformation control method of the dot matrix type low-stress clamping fixture, the small allowance thinning of the pure copper planar component is carried out. The laser interferometer (measurement accuracy of 0.03μm) is used to measure the machining surface shape accuracy. Among them, the machining surface shape accuracy is 3.9μm, and the clamping surface shape accuracy is 5.5μm. The test results show that compared with the traditional vacuum clamping, the proposed local bonding strategy effectively improves the machining surface shape accuracy of the pure copper planar component.

[0047] Those of ordinary skill in the art will realize that the embodiments described herein are to assist the reader in understanding the principles of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific deformations and combinations without departing from the essence of the present invention based on the technical revelations disclosed in the present invention, and these deformations and combinations are still within the protection scope of the present invention.

Claims

1. A method for predicting deformation of weak rigid pure copper planar components under time-varying multi-factors, characterized in that: The following steps are involved: S1. Establish a prediction method for internal stress-induced deformation during the processing of pure copper flat components. Use rolling numerical simulation to establish a stress-deformation simulation model for weakly rigid pure iron curved components. Simulate to obtain the initial internal stress field. Then, adjust the internal stress through heat treatment. Finally, use the birth-death unit to remove the material and obtain the influence of internal stress evolution on deformation. S2. Considering the flipping process in the actual cutting of the planar component, the material residue on the upper and lower surfaces of the planar component is removed alternately in the simulation model to simulate the entire process of the real flipping process; S3. Establish a prediction model for residual stress during machining, combine the influence of cutting speed on the machining deformation of pure copper plane components, explore the deformation forms of pure copper plane components under two machining modes: constant linear speed cutting and constant rotation speed cutting, and further explore the influence of cutting parameters on the deformation of pure copper plane components during precision machining; S4. Establish a vacuum clamping stress-deformation prediction model to analyze the deformation under vacuum adsorption clamping and the residual stress generated on the workpiece surface due to clamping.

2. The method for predicting deformation of a weakly rigid pure copper plane component under time-varying multiple factors according to claim 1 is characterized in that: The initial internal stress field obtained in step S1 is obtained based on stress reconstruction and annealing simulation to obtain the internal stress field of the pure copper plane component, and stress loading under refined grid is achieved through mapping algorithm.

3. The method for predicting deformation of a weakly rigid pure copper plane component under time-varying multiple factors according to claim 1 is characterized in that: The material removal process using birth and death units in step S1 is based on an established stress and deformation simulation model for weakly rigid pure iron curved surface components. The unit birth and death technology is used to simulate the actual material removal process to obtain the internal stress during the material removal process of the planar component and the deformation evolution law under the action of the internal stress.

4. The method for predicting deformation of a weakly rigid pure copper plane component under time-varying multiple factors according to claim 1 is characterized in that: The heat treatment in step S1 to regulate internal stress is to use multiple heat treatments to control the internal stress of the material during the processing of the pure copper plane component. Heat treatment is required after rough processing and semi-finishing processing.

5. The method for predicting deformation of a weakly rigid pure copper plane component under time-varying multiple factors according to claim 4 is characterized in that: The internal stress is regulated by a process of deep cooling combined with annealing to regulate the internal stress of the pure copper material, wherein the deep cooling process is arranged to be carried out between two heat treatments.

6. The method for predicting deformation of a weakly rigid pure copper plane component under time-varying multiple factors according to claim 1 is characterized in that: The cutting parameter optimization method in step S3 is a cutting parameter optimization method for minimum machining residual stress. A sample set is established based on finite stress detection data, and a mapping relationship is constructed using support vector regression, which greatly improves calculation efficiency.

7. The method for predicting deformation of a weakly rigid pure copper plane component under time-varying multiple factors according to claim 1 is characterized in that: The vacuum clamping stress deformation prediction model in step S4 is a low-stress clamping strategy based on local bonding clamping, which uses hot melt adhesive to achieve multi-point bonding fixation through local bonding method to reduce the deformation of the workpiece after processing.

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