Deformation prediction method for weak-rigidity pure copper plane component under time-varying multiple factors

Abstract

The invention discloses a deformation prediction method for a weak-rigidity pure copper plane component under time-varying multiple factors, and the method comprises the following steps: S1, building a prediction method for internal stress induced deformation of a pure copper plane component in a machining process, building a stress deformation simulation model of a weak-rigidity pure iron curved surface component through a rolling value for simulation, and obtaining an initial internal stress field through simulation; regulating internal stress through heat treatment, and finally removing the material by adopting a life-death unit to obtain the influence of internal stress evolution on deformation; s2, alternately removing material margins on the upper surface and the lower surface of the plane component in the simulation model, and simulating the whole process of real turn-over processing; s3, building and exploring the machining deformation form of the pure copper plane component under the two machining modes of constant linear speed cutting and constant rotating speed cutting, and further exploring the influence rule of cutting parameters on deformation of the pure copper plane component in the precision machining stage; and S4, the deformation amount under the vacuum adsorption clamping effect and the residual stress generated on the surface of the workpiece due to clamping are analyzed.

Description

Technical Field

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

[0002] In modern manufacturing technology, precision machining of weak rigid materials faces many challenges, especially for pure copper flat components, which have significant plastic deformation characteristics. Traditional machining methods often find it difficult to balance material removal efficiency and final workpiece shape accuracy. Therefore, it is urgent to develop new deformation prediction and control technologies to achieve high-precision and high-stability machining results.

[0003] When processing the surface of pure copper, it is first rolled through multiple passes. As the number of rolling passes increases, the stress amplitude increases. After recrystallization annealing, the stress amplitude is reduced. Through quenching, the internal stress is uniform in the surface and symmetrical along the depth direction. Then, stress relief annealing is performed to reduce the stress amplitude after quenching. During the processing, multiple heat treatments are used to control the internal stress of the material. This heat treatment processing deformation still has large internal stress, which needs to be controlled.

[0004] Since the thin-walled pure copper components with large diameter-to-thickness ratio have poor rigidity, they are prone to large deformation under the action of non-uniform processing stress field. Combined with the influence of cutting speed on the processing deformation of pure copper plane components, it can be seen that the constant speed processing deformation is centrally symmetrical and annularly distributed, and the position of its deformation extreme value is related to the position of the entry point. In the precision machining stage, the maximum deformation caused by the machining residual stress is much smaller than the machining deformation caused by the internal stress. The machining deformation is basically uniformly distributed in constant line speed, but the center of the workpiece inevitably has local depression due to non-constant speed machining. Therefore, the reasonable planning of the maximum limited speed during constant line speed machining is the key factor in coordinating the overall deformation of the workpiece. The constant line speed machining method is easier to obtain better machining accuracy than the constant 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 speed. In order to effectively control the machining deformation of weak rigid pure copper plane 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 machining surface accuracy of pure copper plane and pure iron curved surface components.

[0005] Due to the initial surface error of the weak rigid plane component, there is a certain gap between the workpiece and the fixture. When the vacuum suction cup is clamped, the workpiece is mainly subjected to the load perpendicular to the thin-walled component and causes the workpiece to bend and deform. Since the gap between the workpiece and the fixture is generally several microns to tens of microns, the deflection of the thin-walled plane part caused by the vacuum clamping force is much less than 1 / 5 of the plate thickness, which can be analyzed as a thin plate small deflection bending problem in elastic mechanics. It can be seen that the deformation of the workpiece under different vacuum adsorption and the residual stress generated on the surface of the workpiece due to clamping, the thickness h of the workpiece will affect the bending stiffness D of the workpiece, and then affect the deformation 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 is nonlinear with the suction hole and suction groove position. When the suction hole and suction groove are close to the outer edge of the workpiece, it is easier to obtain a smaller clamping deformation. Although vacuum adsorption clamping is stable and reliable, the initial surface shape error is difficult to eliminate through subsequent processing. There is also the problem of excessive deformation after unloading. In the final stage of precision machining, vacuum adsorption clamping can hardly meet the machining accuracy requirements. Summary of the invention

[0006] The purpose of the present invention is to solve the above problems and to provide a deformation prediction method for weakly rigid pure copper planar components under time-varying multi-factor effects by establishing a comprehensive stress model, analyzing the influence of internal stress, processing residual stress and clamping stress on deformation, and combining numerical simulation with experimental verification to achieve high efficiency and high stability.

[0007] In order to solve the above technical problems, the technical solution of the present invention is: a method for predicting deformation of a weak rigid pure copper plane component under time-varying multiple factors, comprising the following steps:

[0008] 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.

[0009] 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;

[0010] 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;

[0011] 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.

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

[0013] Furthermore, the material removal process using the birth and death unit in step S1 is based on the established stress and deformation simulation model of weakly rigid pure iron curved surface components, and 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.

[0014] Furthermore, 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 planar component, and heat treatment is required after rough processing and semi-finishing processing.

[0015] Furthermore, the internal stress is regulated by a process of deep cooling and annealing combined to regulate the internal stress of the pure copper material, and the deep cooling process is arranged to be carried out between two heat treatments.

[0016] Furthermore, the optimization method for cutting parameters in step S3 is a cutting parameter optimization method for minimum machining residual stress, which establishes a sample set based on finite stress detection data and uses support vector regression method to construct a mapping relationship, thereby greatly improving calculation efficiency.

[0017] Furthermore, 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.

[0018] The beneficial effects of the present invention are as follows: a deformation prediction method for weak rigidity pure copper planar components under time-varying multi-factors provided by the present invention can effectively predict and control the deformation of weak rigidity pure copper planar components under the action of time-varying multi-factors, improve processing accuracy and stability, reduce deformation during processing, is suitable for the field of precision processing, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the influence of stress evolution on deformation of a pure copper plane component during the whole manufacturing cycle in a deformation prediction method of a weak rigid pure copper plane component under time-varying multiple factors of the present invention;

[0020] Figure 2 Schematic diagram of the internal stress field of the pure copper plane component of the present invention;

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

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

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

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

[0025] Figure 7 It is a schematic diagram of vacuum adsorption and local point bonding clamping of thin-walled flat parts of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments:

[0027] like Figures 1 to 7 As shown, the present invention provides a method for predicting deformation of a weak rigid pure copper plane component under time-varying multiple factors, comprising the following steps:

[0028] 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 copper curved components. Simulate to obtain the initial internal stress field. Then adjust the internal stress through heat treatment. Finally, use the life-and-death unit to remove the material and 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 to obtain the internal stress field of the pure copper plane component, and the stress loading under the refined grid is realized through the mapping algorithm.

[0030] In this step, the material removal process using birth and death units is based on the established stress and deformation simulation model of weak rigid pure iron curved surface components. The unit birth and death technology is used to simulate the real material removal process, and the internal stress and deformation evolution law under the action of internal stress in the material removal process of the plane component are obtained. Figure 2 As shown, Figure 2 This is the internal stress state of the planar component when the plate thickness is 3.6mm.

[0031] The heat treatment in this step to regulate internal stress is to use multiple heat treatments to control the internal stress of the material during the processing of pure copper planar components. Heat treatment is required after rough processing and semi-finishing processing.

[0032] The internal stress is regulated by a composite process of deep cooling and annealing to regulate the internal stress of pure copper materials. The deep cooling process is arranged between two heat treatments.

[0033] The existing process parameter selection of deep cooling and high temperature aging composite treatment, the influence of deep cooling treatment alone is very small, and it is generally combined with other heat treatment processes. Therefore, the present invention adopts a deep cooling and annealing composite process to regulate the internal stress of pure copper materials. The deep cooling process is arranged between two heat treatments. The conditions of the heat treatment are constant. Both are annealed at 973K for 2H, and then cooled with the furnace. The heat treatment process is carried out in a non-vacuum furnace. The conditions of deep cooling treatment will change. The low temperature treatment is carried out under the domestic equipment SL-500. The four-factor three-level orthogonal test table L9 (43) is used to design the experiment. The deep cooling temperature, holding time and heating and cooling rate of the workpiece are used as control variables. The internal stress of the specimen after cold / heat treatment is used as the response characteristic. The temperature range of 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 turning test method, the machining deformation law caused by the internal stress of the material of the test piece with a thickness of 1.2mm was compared and studied after annealing at 300℃ for 72 hours and after annealing at 300℃ and cryogenic treatment. The test shows that the cutting deformation of the test piece treated with cryogenic treatment is much lower than the machining deformation of annealing treatment only.

[0034] S2. Considering the flipping process in the actual cutting of planar components, the material residues on the upper and lower surfaces of the planar components are removed alternately in the simulation model to simulate the entire process of real flipping.

[0035] like Figure 3 and Figure 4 As shown, this embodiment alternately removes the material excess on the upper and lower surfaces of the planar component in the simulation model, simulates the entire process of real flipping processing, and finally thins the planar component from a plate thickness of 3.6 mm to 2.4 mm. The changes in the internal stress state of the component during the flipping process are consistent with the deformation changes under the action of internal stress during the flipping process of the pure copper planar component.

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

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

[0038] S3. A machining residual stress prediction model is established. Combined with the influence of cutting speed on the machining deformation of pure copper planar components, the machining deformation forms of pure copper planar components under two machining methods, constant linear speed cutting and constant rotation speed cutting, are explored. Furthermore, the influence of cutting parameters on the deformation of pure copper planar components during the precision machining stage is explored.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] Through the subroutine SIGINI in ABAQUS, the variable cutting speed cutting process in the full-area machining of pure copper planar components is considered. Combined with the established pure copper material machining residual stress prediction model, the variable machining residual stress field in the full-area 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 components as the initial condition. By analyzing the displacement of the upper surface nodes of the workpiece under the action of the equivalent stress field, the machining surface shape of the pure copper planar component under the action of the machining residual stress is obtained. Figure 5 and Figure 6 As shown in the figure, it shows that the constant speed machining deformation is distributed in a centrally symmetrical annular shape, and the position of the deformation extreme value is related to the position of the entry point. In the precision machining stage, the maximum deformation caused by the machining residual stress is much smaller than the machining deformation caused by the internal stress. The constant line speed machining deformation is basically uniformly distributed, but the center of the workpiece inevitably has a local depression due to non-constant speed machining. Therefore, the reasonable planning of the maximum limited speed during constant line speed machining is the key factor in coordinating the overall deformation of the workpiece. And the constant line speed machining method is easier to obtain better machining accuracy than the constant 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 speed.

[0043] Figure 5 In the figure, (a) shows the deformation distribution diagram of constant rotation speed machining, and (b) shows the deformation distribution diagram of constant line speed machining. Figure 6 (a) shows the influence of spindle speed on deformation, (b) shows the influence of cutting depth on deformation, and (c) shows the influence of feed rate on deformation.

[0044] For the semi-finishing stage dominated by machining residual stress, the cutting parameter range is first determined, and then the support vector regression algorithm is applied to establish the nonlinear model of surface residual stress in cutting and feed directions with respect to cutting speed, feed rate and cutting depth. The specific process is as follows: the input-response data set is divided into a fitting group and a validation group, and the values ​​of each cutting parameter and surface residual stress in cutting and feed directions are normalized to the interval [-1,1]; the parameters in the support vector regression model are iteratively optimized; based on the obtained parameters, a support vector regression (SVR) model of surface residual stress in cutting and feed directions is established; the validation data set is used to evaluate the prediction accuracy of the SVR model in cutting and feed directions. Based on the established SVR model of surface residual stress in cutting and feed directions, the optimal cutting process parameters are obtained by using an improved particle swarm algorithm with the goal of minimizing the surface residual stress.

[0045] For the deformation prediction of vacuum clamping stress of weak rigid planar components, the deflection of thin-walled planar parts caused by vacuum clamping force is much less than 1 / 5 of the plate thickness, which can be analyzed as a thin plate small deflection bending problem in elastic mechanics. According to the straight normal line assumption, mid-plane displacement assumption, and no extrusion assumption in the plate proposed by Kirchhoff, the small deflection bending displacement component of the thin plate can be calculated, and then the stress component can be obtained by combining geometric equations and physical equations; the stress component on the side of the plate is simplified to the mid-plane, and the distributed bending moment, torque and distributed shear force on the side of the plate acting on the midline of the side of the plate are obtained; according to the equilibrium conditions of the microelement, the equilibrium equations of the force in the z direction and the moment equilibrium equations about the x-axis and the y-axis are written respectively, and the equilibrium differential equations expressed by the internal force components are obtained; according to the above mechanical model, the deformation of the workpiece under different vacuum adsorption and the residual stress generated on the surface of the workpiece due to clamping can be calculated. The thickness h of the workpiece will affect the bending stiffness D of the workpiece, and then affect the deformation of the workpiece. The calculation results show that the clamping deformation increases with the increase of clamping stress, which is a linear relationship; the clamping deformation decreases with the increase of workpiece thickness, and gradually tends to be stable, which is an exponential relationship; the clamping deformation increases with the increase of suction hole diameter and suction groove width, and the growth rate gradually increases; the clamping deformation has a nonlinear relationship with the position of suction hole and suction groove, and it is easier to obtain a smaller clamping deformation when the suction hole and suction groove are close to the outer edge of the workpiece.

[0046] like Figure 7As shown in the figure, 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. The unbalanced stress caused by material removal is redistributed during the processing process, so the deformation is small after unloading, which is suitable for the final excess removal stage of precision processing. Combined with the deformation control method of the dot matrix low-stress clamping fixture, the pure copper plane component is thinned with a small excess. The surface shape accuracy of the processing is measured by a laser interferometer (measurement accuracy 0.03μm), of which the surface shape accuracy of the processing surface is 3.9μm and the surface shape accuracy of the clamping surface is 5.5μm. The test results show that compared with the traditional vacuum clamping, the proposed local bonding strategy effectively improves the surface shape accuracy of the pure copper plane component.

[0047] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations 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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