CN113351891A - Local bonding clamping method for reducing turning deformation of disc-like plane component - Google Patents

Local bonding clamping method for reducing turning deformation of disc-like plane component Download PDF

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CN113351891A
CN113351891A CN202110616113.4A CN202110616113A CN113351891A CN 113351891 A CN113351891 A CN 113351891A CN 202110616113 A CN202110616113 A CN 202110616113A CN 113351891 A CN113351891 A CN 113351891A
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bonding
cutting
unit
planar member
plane
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CN113351891B (en
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孙玉文
闫舒洋
孙辉
齐书韬
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Dalian University of Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B5/00—Turning-machines or devices specially adapted for particular work; Accessories specially adapted therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B25/00—Accessories or auxiliary equipment for turning-machines
    • B23B25/06—Measuring, gauging, or adjusting equipment on turning-machines for setting-on, feeding, controlling, or monitoring the cutting tools or work
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
    • B23Q3/00—Devices holding, supporting, or positioning work or tools, of a kind normally removable from the machine
    • B23Q3/02—Devices holding, supporting, or positioning work or tools, of a kind normally removable from the machine for mounting on a work-table, tool-slide, or analogous part
    • B23Q3/06—Work-clamping means
    • B23Q3/08—Work-clamping means other than mechanically-actuated
    • B23Q3/084—Work-clamping means other than mechanically-actuated using adhesive means

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Abstract

The invention belongs to the technical field of turning and clamping of plane members, and discloses a local bonding and clamping method for reducing turning deformation of a disc-like plane member, which comprises the steps of firstly determining the number of bonding points according to the given radius of a dot matrix bonding unit and the stress balance condition of the plane member, and initializing the positions of the bonding points; establishing a multi-cutting simulation model of the planar member, further applying an initial internal stress field, and locally constraining the target member according to the determined position of the bonding point; on the basis, determining a removed grid set by adopting a non-uniform material removal technology, submitting calculation and determining a processed planar member surface shape PV value; and finally, optimizing the position of the bonding point based on a genetic algorithm by taking the minimum processing deformation as a target until the optimal position sequence of the bonding point matrix is finally obtained. The invention adopts a local dot matrix bonding clamping mode, thereby not only reducing the clamping deformation of the plane component, but also effectively reducing the stress deformation caused by the turning process, and obviously improving the processing precision of the plane component.

Description

Local bonding clamping method for reducing turning deformation of disc-like plane component
Technical Field
The invention belongs to the technical field of turning and clamping of plane members, and particularly relates to a local bonding method for reducing machining deformation of a disc-type plane member.
Background
The surface shape precision of some disc thin-wall plane components in the fields of information electronics, energy power and the like is often extremely high, but the disc thin-wall plane components are easy to deform under the action of stress due to large diameter-thickness ratio and poor rigidity, so that the difficulty of ensuring the precision in turning is extremely high. Although the machining stress layer can be greatly reduced by adopting an ultra-precise single-point diamond lathe for micron cutting, and the deformation problem of the thin-wall plane piece under the action of the machining stress is improved, the clamping stress and the internal stress of the piece still exist and run through the whole machining period. The clamping form not only directly influences the clamping deformation of the component, but also changes the stress release mode in the component processing process, and further influences the stress deformation distribution after the thin-wall plane component is processed.
At present, a vacuum adsorption clamping method is often adopted to replace a traditional mechanical clamping method so as to solve the problems of large clamping deformation, easy damage to components and the like caused in the clamping process of thin-wall planar components. The vacuum adsorption method firmly presses the component on the surface of the clamp through the pressure difference between the vacuum cavity in the clamp body and the atmosphere, and has the advantage of reliable clamping. However, as the thickness of the planar member is reduced, the stress deformation of the member is increased, and the accuracy of the surface shape is also deteriorated. Under the condition that the clamping surface has surface shape errors, although the clamping surface can be forced to be flattened under the action of vacuum adsorption force, the plane component is restrained to be elastically restored after unloading, so that the surface shape errors of the clamping surface are reflected to the processing surface. At the moment, strong correlation exists between the machining surface precision of the plane component and the clamping surface precision, and the machining deformation can not be converged in a turnover machining mode. Furthermore, under the strong constraint of the adsorption force, the unbalanced stress induced by material removal cannot be released during processing. After the constraint unloading is finished, the accumulated unbalanced stress is released completely, and the internal stress is rebalanced to generate large stress deformation. At the moment, the clamping deformation and the stress deformation jointly restrict the machining precision of the thin-wall plane component under the vacuum adsorption clamping condition.
In addition, the bonding method is applied to the polishing process of the optical element, mainly fixing the workpiece on a fixture to reduce clamping deformation, and generally bonding the positioning surface integrally. The literature 'bonding and holding deformation in polishing and processing of the ultrathin quartz plate' (optical precision engineering, 2019, 27 (11): 128-135) researches the influence of the curing sequence of the adhesive on the clamping deformation of the ultrathin quartz plate, but does not relate to the optimal selection problem of the number and the position of the bonding units. At present, the bonding method is not applied in turning, and particularly, a local bonding strategy aiming at reducing the turning deformation under the action of factors such as internal stress of parts, clamping and the like is not seen.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a local bonding and clamping method for a turning process of a plane member, which aims to solve the problem of overlarge processing deformation when a disc-type plane member is processed by adopting the existing clamping scheme.
The technical scheme adopted by the invention for solving the problems is as follows:
a local bonding and clamping method for reducing turning deformation of a disc-like plane member is characterized in that the number of bonding points is determined according to the given radius of a dot matrix bonding unit and the stress balance condition of the plane member, and the positions of the bonding points are initialized; establishing a multi-cutting simulation model of the planar member, further applying an initial internal stress field, and locally constraining the target member according to the determined position of the bonding point; on the basis, determining a removed grid set by adopting a non-uniform material removal technology, submitting calculation and determining a processed planar member surface shape PV value; and finally, optimizing the position of the bonding point based on a genetic algorithm by taking the minimum processing deformation as a target until finally obtaining the optimal position sequence of the bonding point matrix.
The method comprises the following specific steps:
the machining method comprises the following steps that firstly, the planar member is subjected to the combined action of cutting force and gravity in the machining process. In order to ensure the bonding reliability of the planar member, the bonding force and the bonding torque provided by the bonding wax need to meet the requirements of force balance and torque balance of the planar member. The bonding units in the selected local bonding scheme are all circular in shape and are configured according to planesThe range of the radius r of the bonding unit is selected from 2.5mm to 7.5mm according to the geometrical size of the piece. Therefore, the minimum number of the adhesive points N satisfying the balance of the cutting force in the horizontal directionhThis can be found from the following relationship:
Figure BDA0003097605150000031
wherein w is the shear strength of the bonding wax, FfFeed resistance for turning, fsThe safety factor is.
Different from the horizontal stress condition of the plane member, the stress condition of the plane member in the vertical direction can be slightly different from the bed structure. When the processing machine tool is of a front-mounted tool rest structure, the main cutting force borne by the workpiece is opposite to the gravity direction of the workpiece when the main shaft rotates forwards, and the minimum number N of the bonding points which meet the requirement of cutting force balance in the vertical directionvqThis can be found by the following equation:
Figure BDA0003097605150000032
wherein R is the radius of the disc-like planar member, t is the thickness of the planar member, ρ is the material density of the member, and FcThe main cutting force is the turning work.
When the machine tool is of a rear-mounted tool rest structure, the main cutting force borne by the workpiece is the same as the gravity direction of the workpiece when the main shaft rotates forwards, and the minimum number N of the bonding points which meet the requirement of cutting stress balance in the vertical direction at the momentvhThis can be found by the following equation:
Figure BDA0003097605150000033
due to NvhIs constantly greater than NvqThus selecting NvhNumber N of minimum adhesion points satisfying vertical force balancevIn which N isv＝Nvh. Further, according to
Figure BDA0003097605150000034
And initially selecting the number N of the bonding points meeting the stress balance condition of the planar member.
And secondly, defining the center of the circle of the bottom surface of the workpiece as the origin (0,0,0) of the coordinate system under the coordinate system of the machine tool, wherein the height in the Z direction is 0 because the bonding unit is positioned on the bottom surface of the workpiece. The bond site location is expressed in polar coordinates as (R)i，θi) Wherein 0. ltoreq.Ri≤R-r,0≤θi≦ 2 π, followed by initialization of bond site location combinations. In order to ensure the clamping stability of the workpiece, the circumferential moment generated by the shearing force between the workpiece and the adhesive layer needs to satisfy the following relation:
Figure BDA0003097605150000041
when the circumferential moment applied to the plane member conforms to the relationship, the bonding position sequence is directly output
Figure BDA0003097605150000042
Otherwise, a new bonding point (R) is randomly generatedn+1，θn+1) The bonding point is added to the bonding position sequence and the N +1 operation is performed to update the number of bonding points, and this operation is repeated until equation (4) is satisfied. Setting the maximum number of bonding points Nmax1.1 to 1.8 times of the initial selection number of the bonding points, if the number N of the bonding points is larger than a preset number threshold NmaxAnd (4) if the condition of the formula (4) is not met, stopping iteration, judging that the position sequence of the group of bonding points is unreasonable, reinitializing the position sequence of the bonding points, and executing the subsequent operation in the step two until a bonding point position combination meeting the clamping stability of the plane member is obtained.
And step three, carrying out parametric modeling on the planar member by applying a Python secondary development technology, finishing the setting of simulation parameters such as geometric characteristics, material properties and the like of the planar member in finite element software Abaqus, and locally constraining the processing and positioning surface of the planar member at the position sequence of the bonding point determined in the step two. Dividing the planar member into a cutting layer and a base layer in a thickness direction, and performing local mesh refinement on the cutting layer, wherein the mesh type is an eight-node reduced integral hexahedral cell C3D 8R. And reconstructing the initial internal stress field after the mesh refinement based on a shape function interpolation method, and then loading the initial internal stress field into a finite element analysis model.
Step four, because the unbalanced stress induced by material removal is gradually released in the form of component deformation in the cutting process, although the moving track of the tool is a straight line parallel to the positioning surface of the workpiece, the actual cutting depth of the tool at each processing position is different, and the method belongs to the non-uniform material removal process. And (4) judging whether the unit is removed in the cutting process according to the axial relative position between the integral point of the deformed grid unit and the cutting plane by combining a unit life-death technology. Specifically, for the ith cut, the kth cell E in the jth layer of the gridkContains 8 nodes n in totalkd(d-0, 1 …, 7), the initial axial coordinate for each node is represented as Nczkd(d ═ 0,1 …, 7). Node n at the i-th cuttingkdThe actual Z-direction coordinate of the node is the accumulation of the initial axial coordinate of the node and the axial deformation of the node after the i-1 th cutting. Therefore, an odb result file generated after the i-1 th cutting simulation is read in, the initial Z-direction coordinate and the axial deformation value of the corresponding node are extracted, and the unit E is used for the i-th cuttingkActual axial position coordinates Ecz of the equivalent integration pointskCan be calculated by equation (5).
Figure BDA0003097605150000051
In the formula
Figure BDA0003097605150000052
Represents the grid node n after the i-1 cuttingkdSince the workpiece is not deformed at the first cutting, the axial deformation of (2) is not generated
Figure BDA0003097605150000053
Satisfy the equation
Figure BDA0003097605150000054
Traverse and calculate the j-th gridIf the calculation result is higher than the axial height of the ith cutting plane, the judgment unit is killed in the ith cutting process, and the unit numbers are stored in the grid set which is removed in the ith cutting process
Figure BDA0003097605150000055
In (1). On the other hand, the judgment unit "survives" in the ith cut, and stores the unit number in the grid set not removed in the ith cut
Figure BDA0003097605150000056
In (1). Determining the removed unit set layer by layer according to the above calculation process until all grids included in the ith cutting are traversed, and then killing the set
Figure BDA0003097605150000057
And submitting the calculation to the ith simulation until the corresponding grid unit is completed. Will be provided with
Figure BDA0003097605150000058
The unit number in (1) is directly stored in the removed unit number set ExcIn a middle, and
Figure BDA0003097605150000059
the set of unremoved cells included in (b) will participate in performing subsequent simulation operations as part of the material to be removed in the (i + 1) th cut. And circularly executing the operation in the step four until the simulation calculation of the multiple feed cutting is completed.
Step five, after the simulation of multiple feed cutting is finished, assembling ExcAll units "killed" in each pass cut simulation are included. Number set E of all cells of grid refinement layerxAnd set ExcDifference set E ofxuRepresenting a collection of unremoved cells of the refinement layer. Traverse set ExcAnd superposing the initial Z-direction coordinate of the unit node in the set and the axial deformation corresponding to the node, wherein the minimum value of the calculation result represents the lowest point Z of the surface of the planar member after the cutting is finishedmin. Traverse set ExuCalculatingThe real axial position of the unit node in the set, and the maximum value of the result represents the highest point Z of the surface of the planar member after the cutting is finishedmaxThe PV value of the profile of the planar member can be determined by Zmax-ZminAnd (6) calculating.
And step six, optimizing the position of a local bonding point by adopting a genetic algorithm by taking the minimum surface PV value of the plane member after multiple-time feed cutting simulation as a target. Setting the maximum iteration number K according to the calculation efficiency requirementmaxThe value range is 200 to 300 generations, and when the iteration number J meets the condition J<KmaxAnd repeating the second step, the third step, the fourth step and the fifth step to generate a new bonding point position combination and calculate the surface PV value of the plane component under the clamping condition. Traversing and comparing the generated bonding point position sequence, judging that position overlapping exists in the bonding sequence if the center distance between the bonding unit i and the bonding unit j meets the condition of the formula (6), and correcting the surface PV value under the unreasonable bonding scheme to be a preset maximum value. And outputting the J-th secondarily-generated bonding point position sequence and the corresponding PV value of the profile, and updating the iteration times according to J + 1. The number of iterations J is equal to KmaxAnd stopping time circulation and finishing the optimization process of the bonding point position.
Figure BDA0003097605150000061
The invention has the beneficial effects that:
the invention provides a local dot-matrix type bonding and clamping method for reducing machining deformation in the turning process of a disc-type plane member, which reduces the turning and clamping deformation, gradually releases unbalanced internal stress induced by material removal in the cutting process, effectively reduces stress deformation caused by the turning of the plane member and improves the machining surface shape precision of the plane member.
Drawings
FIG. 1 is a flow chart for bond site optimization based on minimizing stress deformation of planar members.
Fig. 2 is a schematic view of the forces applied to the disc-like planar member during the machining process.
Fig. 3(a) is a schematic diagram of a cut considering a non-uniform material removal process, and fig. 3(b) is a schematic diagram of a node of a single grid cell.
Fig. 4 is a schematic view showing the state of cells in the mesh of the j-th layer after the i-th cut.
Fig. 5 is a schematic diagram of the state of cells in the integral grid after the cutting simulation of the planar member is completed.
FIG. 6 is an initial internal stress state of a pure copper planar member at a plate thickness of 2.6 mm.
FIG. 7 is an optimized convergence curve of PV values of a pure copper planar member processing profile.
FIG. 8 is a simulation diagram of the machined surface shape of a pure copper planar member.
Detailed Description
The following detailed description of the embodiments of the invention is provided in connection with the accompanying drawings and the claims.
A flow chart of a local bonding method for minimizing stress deformation is shown in fig. 1, and by optimizing the bonding position of a disc-like planar member, the stress deformation of the planar member after processing is reduced, so as to improve the processing surface shape precision of the planar member. The embodiments of the present invention will now be described in detail with reference to the drawings and specific embodiments, it should be noted that the embodiments described herein are only for the purpose of illustrating the present invention and are not to be construed as limiting the present invention.
Step one, as shown in fig. 2, the planar member is subjected to the combined action of cutting force and gravity during the cutting process. In order to ensure the bonding reliability of the planar member, the bonding force and the bonding torque provided by the bonding wax need to meet the requirements of force balance and torque balance of the planar member. The shapes of the bonding units in the selected local bonding scheme are all circular, and the radius r of the unit is selected to be 5 mm. Therefore, the minimum number of the adhesive points N satisfying the balance of the cutting force in the horizontal directionhThis can be found from the following relationship:
Figure BDA0003097605150000071
wherein w is the shear strength of the bonding wax, FfFeed resistance for turning，fsThe safety factor is.
Different from the horizontal stress condition of the plane member, the stress condition of the plane member in the vertical direction can be slightly different from the bed structure.
When the processing machine tool is of a front-mounted tool rest structure, the main cutting force borne by the workpiece is opposite to the gravity direction of the workpiece when the main shaft rotates forwards, and the minimum number N of the bonding points which meet the requirement of cutting force balance in the vertical directionvqThis can be found by the following equation:
Figure BDA0003097605150000072
wherein R is the radius of the disc-like planar member, t is the thickness of the planar member, rho is the material density of the member, and FcThe main cutting force is the turning work.
When the machine tool is of a rear-mounted tool rest structure, the main cutting force borne by the workpiece is the same as the gravity direction of the workpiece when the main shaft rotates forwards, and the minimum number N of the bonding points which meet the requirement of cutting stress balance in the vertical direction at the momentvhThis can be found by the following equation:
Figure BDA0003097605150000081
due to NvhIs constantly greater than NvqThus selecting NvhNumber N of minimum adhesion points satisfying vertical force balancevIn which N isv＝Nvh. Further, according to max (N)v，Nh) And initially selecting the number N of the bonding points meeting the stress balance condition of the planar member.
And secondly, defining the center of the circle of the bottom surface of the workpiece as the origin (0,0,0) of the coordinate system under the coordinate system of the machine tool, wherein the height in the Z direction is 0 because the bonding unit is positioned on the bottom surface of the workpiece. The bond site location is expressed in polar coordinates as (R)i，θi) Wherein 0. ltoreq.Ri≤R-r,0≤θi≦ 2 π, followed by initialization of bond site location combinations. In order to ensure the clamping stability of the workpiece, the circumferential moment generated by the shearing force between the workpiece and the adhesive layer needs to satisfy the following relationComprises the following steps:
Figure BDA0003097605150000082
when the circumferential moment applied to the plane member conforms to the relationship, the bonding position sequence is directly output
Figure BDA0003097605150000083
. Otherwise, a new bonding point (R) is randomly generatedn+1，θn+1) The bonding point is added to the bonding position sequence and the N +1 operation is performed to update the number of bonding points, and this operation is repeated until equation (4) is satisfied. Setting the maximum number of bonding points Nmax1.5 times of the initial selection number of the bonding points, if the number N of the bonding points is greater than the preset number threshold NmaxAnd (4) if the condition of the formula (4) is not met, stopping iteration, judging that the position sequence of the group of bonding points is unreasonable, reinitializing the position sequence of the bonding points, and executing the subsequent operation in the step two until a bonding point position combination meeting the clamping stability of the plane member is obtained.
And step three, carrying out parametric modeling on the planar member by applying a Python secondary development technology, finishing the setting of simulation parameters such as geometric characteristics, material properties and the like of the planar member in finite element software Abaqus, and locally constraining the processing and positioning surface of the planar member at the position sequence of the bonding point determined in the step two. Dividing the planar member into a cutting layer and a base layer in a thickness direction, and performing local mesh refinement on the cutting layer, wherein the mesh type is an eight-node reduced integral hexahedral cell C3D 8R. And reconstructing the initial internal stress field after the mesh refinement based on a shape function interpolation method, and then loading the initial internal stress field into a finite element analysis model.
Step four, as shown in fig. 3(a), since the unbalanced stress induced by material removal is gradually released in the form of deformation of the member during the cutting process, although the tool movement path is a straight line parallel to the workpiece positioning surface, the actual cutting depth of the tool at each processing position is different, and the process belongs to the non-uniform material removal process. Combining with unit life and death technique, according to the integrated value of deformed grid unitAnd the axial relative position between the point and the cutting plane is judged whether the unit is removed in the cutting process. As shown in FIG. 3(b), for the ith cut, the kth cell E in the jth layer gridkContains 8 nodes n in totalkd(d-0, 1 …, 7), the initial axial coordinate for each node is represented as Nczkd(d ═ 0,1 …, 7). Node n at the i-th cuttingkdThe actual Z-direction coordinate of the node is the accumulation of the initial axial coordinate of the node and the axial deformation of the node after the i-1 th cutting. Therefore, an odb result file generated after the i-1 th cutting simulation is read in, the initial Z-direction coordinate and the axial deformation value of the corresponding node are extracted, and the unit E is used for the i-th cuttingkActual axial position coordinates Ecz of the equivalent integration pointskCan be calculated by equation (5).
Figure BDA0003097605150000091
In the formula
Figure BDA0003097605150000092
Represents the grid node n after the i-1 cuttingkdAxial deformation of the workpiece, since the workpiece is not yet deformed at the time of the first cutting, is not yet generated
Figure BDA0003097605150000093
Satisfy the equation
Figure BDA0003097605150000094
Traversing and calculating the actual axial coordinates of all unit integral points in the jth layer of grid, as shown in fig. 4, if the calculation result is higher than the axial height of the ith cutting plane, determining that the unit is killed in the ith cutting process, and storing the unit numbers in the ith cutting removed grid set
Figure BDA0003097605150000095
In (1). Otherwise, the judgment unit survives in the ith cutting process, and the unit number is stored in the grid set which is not removed in the ith cutting
Figure BDA0003097605150000096
In (1). Determining the removed unit set layer by layer according to the above calculation process until all grids included in the ith cutting are traversed, and then killing the set
Figure BDA0003097605150000101
And submitting the calculation to the ith simulation until the corresponding grid unit is completed. Will be provided with
Figure BDA0003097605150000102
The unit number in (1) is directly stored in the removed unit number set ExcIn a middle, and
Figure BDA0003097605150000103
the set of unremoved cells included in (b) will participate in performing subsequent simulation operations as part of the material to be removed in the (i + 1) th cut. And circularly executing the operation in the step four until the simulation calculation of the multiple feed cutting is completed.
Step five, after the simulation of multiple feed cutting is completed, set ExcAll units "killed" in each pass cut simulation are included. Number set E of all cells of grid refinement layerxAnd set ExcDifference set E ofxuRepresenting a collection of unremoved cells of the refinement layer. As shown in fig. 5, the mesh surface generated after the machining simulation is completed and the machining deformation corresponding to the mesh node together affect the final machining surface shape of the planar member. Thus traversing set ExcAnd superposing the initial Z-direction coordinate of the unit node in the set and the axial deformation corresponding to the node, wherein the minimum value of the calculation result represents the lowest point Z of the surface of the planar member after the cutting is finishedmin. Traverse set ExuCalculating the real axial position of the unit node in the set, wherein the maximum value of the result represents the highest point Z of the surface of the planar member after the cutting is finishedmaxThe PV value of the profile of the planar member can be determined by Zmax-ZminAnd (6) calculating.
Step six, aiming at minimizing the surface PV value of the plane component after multiple-feed cutting simulation, adopting inheritanceThe algorithm optimizes the bonding unit position. Setting a maximum number of iterations Kmax230, when the number of iterations J satisfies the condition J<KmaxAnd repeating the second step, the third step, the fourth step and the fifth step to generate a new bonding point position combination and calculate the surface PV value of the plane component under the clamping condition. Traversing the newly generated bonding point position sequence, judging that position overlapping exists in the bonding sequence if the central distance between the bonding unit i and the bonding unit j meets the condition of the formula (6), and correcting the surface PV value under the unreasonable bonding scheme to be a preset maximum value of 500 um. And outputting the J-th secondarily-generated bonding point position sequence and the corresponding PV value of the profile, and updating the iteration number J according to J + 1. The number of iterations J is equal to KmaxAnd stopping time circulation and finishing the position optimization process of the bonding unit.
Figure BDA0003097605150000111
Specifically, a pure copper planar disk having a diameter of 200mm and a thickness of 2.6mm is taken as an example: wherein, a diamond lathe tool is adopted for cutting, the cutting depth is 10 mu m each time, and the cutting is continuously carried out for 5 times. The pure copper plane component is subjected to a main cutting force of less than 5N and a feed resistance of less than 1N under the cutting parameters. The pure copper material has a density of 8980kg/m3 and the shear strength of the used bonding wax is 2.314MPa by using a universal tensile testing machine. And (4) determining the number of the bonding points to be 17 according to the clamping stability judgment model by combining the simulation parameters. FIG. 6 shows the initial stress state of a pure copper plane member at a thickness of 2.6mm, and FIG. 7 shows an optimized convergence curve. Table 1 shows the optimized bonding unit position in the machine coordinate system, and fig. 8 is a simulation diagram of the processing surface shape of the pure copper planar component under the bonding and clamping condition. The result shows that the optimized position of the bonding unit is beneficial to reducing the processing deformation of the plane member under the bonding and clamping condition.
TABLE 1 optimized bonding position combinations
Figure BDA0003097605150000112

Claims (1)

1. A local bonding and clamping method for reducing turning deformation of a disc-like plane member is characterized in that the number of bonding points is determined according to the given radius of a dot matrix bonding unit and the stress balance condition of the plane member, and the positions of the bonding points are initialized; establishing a multi-cutting simulation model of the planar member, further applying an initial internal stress field, and locally constraining the target member according to the determined position of the bonding point; on the basis, determining a removed grid set by adopting a non-uniform material removal technology, submitting calculation and determining a processed planar member surface shape PV value; finally, optimizing the position of the bonding point based on a genetic algorithm by taking the minimum processing deformation as a target until finally obtaining the optimal position sequence of the bonding dot matrix; the method comprises the following specific steps:
the method comprises the following steps that firstly, a plane component is subjected to the combined action of cutting force and gravity in the cutting process; in order to ensure the bonding reliability of the planar member, the bonding force and the bonding torque provided by the bonding wax need to meet the requirements of force balance and torque balance of the planar member; the shapes of the bonding units in the selected local bonding scheme are circular, and the radius r of the bonding units is selected to be 2.5-7.5 mm according to the geometric dimension of the planar member; therefore, the minimum number of the adhesive points N satisfying the balance of the cutting force in the horizontal directionhThe following relationship was used to determine:
Figure FDA0003097605140000011
wherein w is the shear strength of the bonding wax, FfFeed resistance for turning, fsA safety factor is set;
different from the horizontal stress condition of the plane component, the stress condition of the plane component in the vertical direction is slightly different from the structure of the bed;
when the processing machine tool is of a front-mounted tool rest structure, the main cutting force borne by the workpiece is opposite to the gravity direction of the workpiece when the main shaft rotates forwards, and the minimum number N of the bonding points which meet the requirement of cutting force balance in the vertical directionvqThe following equation is used:
Figure FDA0003097605140000012
wherein R is the radius of the disc-like planar member, t is the thickness of the planar member, ρ is the material density of the member, and FcThe main cutting force is the turning processing;
when the machine tool is of a rear-mounted tool rest structure, the main cutting force borne by the workpiece is the same as the gravity direction of the workpiece when the main shaft rotates forwards, and the minimum number N of the bonding points which meet the requirement of cutting stress balance in the vertical direction at the momentvhThe following equation is used: ,
Figure FDA0003097605140000021
due to NvhIs constantly greater than NvqThus selecting NvhNumber N of minimum adhesion points satisfying vertical force balancevIn which N isv＝Nvh(ii) a Further, according to max (N)v，Nh) Primarily selecting the number N of bonding points meeting the stress balance condition of the planar member;
secondly, defining the center of a circle of the bottom surface of the workpiece as the origin (0,0,0) of the coordinate system under the coordinate system of the machine tool, wherein the height in the Z direction is 0 because the bonding unit is positioned on the bottom surface of the workpiece; the bond site location is expressed in polar coordinates as (R)i，θi) Wherein 0. ltoreq.Ri≤R-r，0≤θiInitializing the position combination of the bonding points after the number is less than or equal to 2 pi; in order to ensure the clamping stability of the workpiece, the circumferential moment generated by the shearing force between the workpiece and the adhesive layer needs to satisfy the following relation:
Figure FDA0003097605140000022
when the circumferential moment applied to the plane member conforms to the relationship, the bonding position sequence is directly output
Figure FDA0003097605140000023
Otherwise, a new bonding point (R) is randomly generatedn+1，θn+1) Adding the bonding point into the bonding position sequence, executing an operation of changing the number of the bonding points into N +1, and repeating the operation until the formula (4) is established; setting the maximum number of bonding points Nmax1.1 to 1.8 times of the initial selection number of the bonding points, if the number N of the bonding points is larger than a preset number threshold NmaxIf the condition of the formula (4) is not met, stopping iteration, judging that the position sequence of the group of bonding points is unreasonable, reinitializing the position sequence of the bonding points, and executing the subsequent operation in the second step until obtaining the bonding point position combination meeting the stability of the planar member clamp;
thirdly, carrying out parametric modeling on the planar component by applying a Python secondary development technology, completing the setting of geometric characteristics and material property simulation parameters of the planar component in finite element software Abaqus, and locally constraining the processing and positioning surface of the planar component at the position sequence of the bonding point determined in the second step; dividing the planar member into a cutting layer and a base layer along the thickness direction, and carrying out local grid refinement on the cutting layer, wherein the grid type is an eight-node reduction integral hexahedral unit C3D 8R; reconstructing an initial internal stress field after grid refinement based on a shape function interpolation method, and then loading the initial internal stress field into a finite element analysis model;
step four, because the unbalanced stress induced by material removal is gradually released in the form of component deformation in the cutting process, although the moving track of the cutter is a straight line parallel to the positioning surface of the workpiece, the actual cutting depth of the cutter at each processing position is different, and the method belongs to the non-uniform material removal process; whether the unit is removed in the cutting process is judged according to the axial relative position between the integral point of the deformed grid unit and the cutting plane by combining a unit life and death technology; specifically, for the ith cut, the kth cell E in the jth layer of the gridkContains 8 nodes n in totalkdD is 0,1 …, 7, and the initial axial coordinate for each node is represented as Nczkd(ii) a Node n at the i-th cuttingkdThe actual Z-direction coordinate is the accumulation of the initial axial coordinate of the node and the axial deformation of the node after the i-1 th cutting; thus reading inExtracting initial Z-direction coordinates and axial deformation values of corresponding nodes from an odb result file generated after the ith-1 cutting simulation, and determining a unit E during the ith cuttingkActual axial position coordinates Ecz of the equivalent integration pointskCan be calculated by equation (5):
Figure FDA0003097605140000031
in the formula (I), the compound is shown in the specification,
Figure FDA0003097605140000032
represents the grid node n after the i-1 cuttingkdI is not less than 1, and the workpiece is not deformed during the first cutting, so that the axial deformation of the workpiece is reduced
Figure FDA0003097605140000033
Satisfy the equation
Figure FDA0003097605140000034
Traversing and calculating the actual axial coordinates of all unit integral points in the jth layer of grid, if the calculation result is higher than the axial height of the ith cutting plane, judging that the unit is killed in the ith cutting process, and storing the unit number in the ith cutting removed grid set
Figure FDA0003097605140000035
Performing the following steps; on the other hand, the judgment unit "survives" in the ith cut, and stores the unit number in the grid set not removed in the ith cut
Figure FDA0003097605140000036
Performing the following steps; determining the removed unit set layer by layer according to the above calculation process until all grids included in the ith cutting are traversed, and then killing the set
Figure FDA0003097605140000037
Submitting the calculation to the ith simulation by the corresponding grid unit; will be provided with
Figure FDA0003097605140000038
The unit number in (1) is directly stored in the removed unit number set ExcIn a middle, and
Figure FDA0003097605140000041
the unremoved unit set contained in the (i + 1) th cutting is used as a part of the material to be removed in the (i + 1) th cutting and participates in the execution of the subsequent simulation operation; circularly executing the operation in the step four until the simulation calculation of the multiple feed cutting is completed;
step five, after the simulation of multiple feed cutting is finished, assembling ExcAll units killed in each feed cutting simulation are included; number set E of all cells of grid refinement layerxAnd set ExcDifference set E ofxuRepresenting a set of units of the refinement layer which are not removed; traverse set ExcAnd superposing the initial Z-direction coordinate of the unit node in the set and the axial deformation corresponding to the node, wherein the minimum value of the calculation result represents the lowest point Z of the surface of the planar member after the cutting is finishedmin(ii) a Traverse set ExuCalculating the real axial position of the unit node in the set, wherein the maximum value of the result represents the highest point Z of the surface of the planar member after the cutting is finishedmaxThe PV value of the profile of the planar member passes through Zmax-ZminCalculating to obtain;
step six, optimizing the position of a local bonding point by adopting a genetic algorithm by taking the minimum surface PV value of the plane member after multiple-time feed cutting simulation as a target; setting the maximum iteration number K according to the calculation efficiency requirementmaxThe value range is 200 to 300 generations, and when the iteration number J meets the condition J<KmaxRepeating the second step, the third step, the fourth step and the fifth step to generate a new bonding point position sequence and calculate the surface PV value of the plane component under the clamping condition; traversing and comparing the generated bonding point position sequence, if the center distance between the bonding unit i and the bonding unit j meets the condition of formula (6), judging that the positions in the bonding sequence are overlapped, and if the positions are not overlappedCorrecting the surface PV value under the physical bonding scheme to be a preset maximum value; outputting a bonding point position sequence generated in the J-th sub-optimization mode and a corresponding surface PV value, and updating iteration times J according to the J-J + 1; the number of iterations J is equal to KmaxStopping time circulation and finishing the optimization process of the bonding point position;
Figure FDA0003097605140000042
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