CN113868781A - Grid special processing method based on two-dimensional simulation cutting - Google Patents

Abstract

The invention discloses a grid special processing method based on two-dimensional simulation cutting, which comprises the following steps of establishing a workpiece model and a cutter model in Abaqus drawing software; cutting the workpiece to establish a chip layer; establishing a damage layer; cutting a cutting layer, and making a base line of grid optimization; setting the material parameters of the processed workpiece according to the material characteristics of the processed workpiece; establishing an analysis step; dividing a grid for the workpiece; carrying out meshing on the tool model; setting the contact attribute of the two-dimensional finite element model of the cutter and the two-dimensional finite element model of the workpiece, selecting surface-surface contact, and setting a friction coefficient according to the material of the workpiece to be processed; setting boundary conditions of a workpiece two-dimensional finite element model and a cutter two-dimensional finite element model; and (5) operating the technical model and storing. Compared with the conventional ALE simulation method, the grid special processing method based on two-dimensional simulation cutting has the advantages that the simulation time is reduced by about 25%, the grids in the simulation result are basically regularized, the unit deletion amount is small, and the cutting force output is stable.

Description

Grid special processing method based on two-dimensional simulation cutting

Technical Field

The invention belongs to the technical field of machining, and particularly relates to a grid special processing method based on two-dimensional simulation cutting.

Background

If the research of the metal cutting process only depends on an experimental means, the time and the labor are consumed, and a high-precision experimental instrument and a high-precision detection instrument are required to be equipped as supports. In recent years, with the development of computer technology and software technology, finite element simulation technology is more and more widely applied in the research of cutting process. Through simulation analysis, the analysis cost and time can be reduced. However, cutting simulation belongs to display analysis and belongs to the situation of large deformation of a grid, the simulation speed is limited by the quality of computer hardware, and the simulation speed and the simulation accuracy are improved by adopting a mode of optimizing a model structure and optimizing the grid under the general situation.

The meshing is a core technology in finite element analysis, for a complex model, the meshing occupies most data of the whole finite element analysis pretreatment, and the quality of the meshing directly influences the efficiency and the precision of calculation. The finite element mesh generation method can be divided into five types: the topology decomposition method, the node connection method, the grid template method, the mapping method and the geometric decomposition method can be used for grid division by using different methods according to different conditions. Finite element simulation in an orthogonal cutting process is carried out, geometric models of a cutter and a workpiece are relatively simple, but a metal cutting process is accompanied by plastic large deformation of high temperature, high pressure and high strain rate, a large amount of distortion of grids can be generated, so that a simulation result is inaccurate, simulation time is long, the problem of grid distortion in two-dimensional simulation cutting is solved, and a traditional rectangular grid dividing method adopting an ALE method can generate different phenomena or grid distortion of parts due to the change of material properties, so that special treatment is urgently needed to the grids, the probability of grid distortion is reduced to a certain extent, more accurate simulation results and less simulation time are obtained, and the simulation time can be greatly reduced by reasonably controlling grid density and a grid dividing mode, so that the simulation precision is improved. At present, there are two main methods for processing the grid distortion in the cutting model, namely an ALE method and a method for performing special processing on the chip grid.

Disclosure of Invention

The invention aims to solve the technical problems of grid distortion in two-dimensional simulation cutting and inaccurate simulation result and long simulation time caused by grid distortion in the prior art, and provides a grid special processing method based on two-dimensional simulation cutting.

In order to solve the technical problems, the invention adopts the technical scheme that:

a grid special processing method based on two-dimensional simulation cutting comprises the following steps:

s1: establishing a workpiece model and a tool model in Abaqus drawing software, wherein the workpiece model selects a rectangular workpiece, and the specific tool parameters comprise a front angle gamma₁Setting the cutter as a rigid body, wherein the clearance angle alpha, the arc radius r of the cutter tip, the height g of the cutter and the width h of the cutter are equal;

s2: cutting the workpiece to establish a chip layer and drawing a straight line A₁The straight line is parallel to the upper boundary of the rectangular workpiece and has a distance from the upper boundary of the rectangular workpiece, the division is completed, and the rectangular workpiece is divided by the straight line A₁The upper half area after being divided is a cutting chip layer, and the lower half area is a matrix;

s3: establishing a damage layer, and drawing a straight line B on the basis of the step S2₁The straight line is parallel to the upper boundary of the rectangular workpiece and has a distance b, b from the upper boundary of the rectangular workpiece<a, the straight line A₁To a straight line B₁The area between the two layers is a damaged layer;

s4: cutting a chip layer, making a base line of grid optimization, selecting one point at the lower left corner of the chip layer as a starting point, taking any point of the upper boundary of the rectangular workpiece as an end point, and drawing an oblique line C₁Oblique line C₁At an angle gamma to the left boundary of the chip bed₂In the same manner, a line C is drawn on the right side of the chip layer₁Parallel oblique lines DA slash C₁And slash D as a baseline for mesh optimization;

s5: setting the material parameters of the workpiece to be processed according to the material characteristics of the workpiece to be processed, wherein the material parameters comprise the density, Young modulus, Poisson ratio, melting point, thermal conductivity, thermal expansion coefficient, specific heat, inelastic coefficient and determined cutting amount of the workpiece to be processed, a Johnson-Cook (J-C) constitutive model is selected as a material model, the damage displacement value in the damage evolution is set to be 1-1.5 times of the minimum grid size, the plane stress strain value of the sections of the workpiece and the cutter is set to be 0.3,

wherein σ is the equivalent stress, A is the initial yield stress, B is the material strain strengthening parameter, ε is the equivalent plastic strain, n is the hardening parameter, C is the material strain rate strengthening parameter,&Is equivalent plastic strain rate, epsilon₀Is the reference strain rate of the material, m is the heat softening index of the material, T_mIs melting temperature, T_rIs a reference temperature;

s6: establishing an analysis step, namely adopting a temperature-displacement coupling analysis step to establish an analysis step and outputting parameters such as cutting force parameters, cutting temperature and the like;

s7: dividing grids for a workpiece, wherein a cutter two-dimensional finite element model is set to be a free step algorithm mainly based on a quadrangle, and carrying out grid encryption processing on a contact part of the cutter finite element model and the workpiece finite element model, namely a cutter round angle, and the method specifically comprises the following steps:

s71: entering a Mesh module, setting the environment bar object option at the top as a component, and selecting the edge cloth in the tool box as the workpiece cloth;

s72: pressing shift to select the upper and lower boundaries, the left and right boundaries of the damaged layer and the upper boundary of the matrix of the whole chip layer, selecting the size in a popped local seed dialog box method, inputting c in the approximate unit size, and keeping the default settings of other parameters;

s73: selecting a base line for grid optimization, wherein different kinds of arrangement can change the inclination angle of the grid, and the arrangement is carried out according to the actual condition;

s74: selecting a left boundary and a right boundary of a matrix, selecting single precision according to size and offset in a selection method in a popped local seed dialog box method, inputting d in the minimum size, inputting e in the maximum size, and keeping default settings of other parameters;

s75: selecting a lower boundary of a matrix, selecting f according to the number in a popped local seed dialog box method, inputting the f in the unit number, and keeping default settings of other parameters;

s76: the cutting layer and the damage layer are provided with grids with quadrilateral attributes, the algorithm option is minimized grid transition, the base part adopts a free step algorithm with quadrilateral as a main part, a mapping network is selected to be used in a proper place, the unit type selects temperature-displacement coupling in the Explicit, the linear order, the hourglass control selects relaxation rigidity, and other parameters are kept in default settings;

s77: finally, selecting a part grid in a tool box to divide the whole workpiece grid, wherein the cutting part presents a rhombic inclined grid, the damaged layer part presents a rectangular grid, and the base part presents a quadrilateral irregular grid;

s8: carrying out mesh division on a tool model, setting the tool two-dimensional finite element model as a free step algorithm mainly taking a quadrangle, and carrying out mesh encryption processing on a contact part of the tool finite element model and the workpiece finite element model, namely a tool round angle;

s9: setting the contact attribute of the two-dimensional finite element model of the cutter and the two-dimensional finite element model of the workpiece, selecting surface-surface contact, and setting a friction coefficient according to the material of the workpiece to be processed;

s10: setting boundary conditions of a workpiece two-dimensional finite element model and a cutter two-dimensional finite element model, setting the bottom of a matrix to be completely fixed, setting the left side of a workpiece to be a displacement corner, checking all values to input 0, setting the right side of the workpiece to be the displacement corner, checking U1 to input the value to be 0, setting a feed machining speed f, and setting initial temperature fields of the cutter and the workpiece according to the ambient temperature when the workpiece is machined;

s11: and saving the model. And operating the Abaqus software, and storing the machined workpiece two-dimensional finite element model obtained by the operation result of the Abaqus software.

The invention has the following beneficial effects: under the condition of the same data, compared with an ALE method used by a common grid, the grid division method has the advantages that the simulation time is reduced by about 25%, the grid in the simulation result is basically regularized, the unit deletion amount is small, the cutting force output is stable, and the grid division method can be used as a cutting simulation model.

Drawings

FIG. 1 is a diagram illustrating simulation results of a tilted grid according to the present invention;

FIG. 2 is a diagram illustrating the results of a conventional grid simulation of the present invention;

FIG. 3 is a schematic diagram of the present invention prior to oblique grid processing;

FIG. 4 is a schematic diagram of a conventional grid prior to processing according to the present invention;

FIG. 5 is a graphical representation of simulated cutting force results for the tilted grid of the present invention and a conventional grid;

FIG. 6 is a schematic diagram of the pre-processing of the oblique meshing according to the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific preferred embodiments.

In the description of the present invention, it is to be understood that the terms "left side", "right side", "upper part", "lower part", etc., indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and that "first", "second", etc., do not represent an important degree of the component parts, and thus are not to be construed as limiting the present invention. The specific dimensions used in the present example are only for illustrating the technical solution and do not limit the scope of protection of the present invention.

Example (b):

referring to fig. 1, 3 and 6, a grid special processing method based on two-dimensional simulation cutting comprises the following steps,

s1: establishing a workpiece model and a tool model in Abaqus drawing software, entering an Abaqus drawing environment, selecting a rectangular tool of a drawing tool box, setting the length to be 1mm and the width to be 0.3mm, successfully creating a double-click middle mouse button, establishing the tool model with the size related to the actual tool in the same way, wherein specific tool parameters comprise a front angle gamma₁The angle alpha is 10 degrees, the angle alpha is 7 degrees, the arc radius r of the tool nose is 0.01mm, the height g of the tool is 0.25mm, and the width h is 0.3 mm;

s2: dividing a workpiece to establish a chip layer, selecting a tool-partition in a main menu, selecting a type selection surface in a partition creating dialog box, selecting a Sketch by the method, displaying a 'Sketch partition geometry' by prompt area information at the bottom of a window, entering a drawing view interface, and clicking a creation line in a tool box: end to end, drawing a straight line A₁Clicking the added size in the tool box in parallel with the upper boundary of the rectangular workpiece, wherein the straight line is parallel with the upper boundary of the rectangular workpiece, the distance between the straight line and the upper boundary of the rectangular workpiece is 0.1mm, completing the segmentation, and the rectangular workpiece is marked by a straight line A₁The upper half area after the division is a cutting chip layer, the lower half area is a substrate, and the sketch exits;

s3: establishing a damage layer, creating a partition in the same way on the basis of the step S2, clicking the upper half part of the workpiece which is already partitioned, selecting the upper part to continue segmentation, entering a drawing view interface, and clicking a creation line in a tool box: end to end, drawing a straight line B₁Line B drawn parallel to the upper boundary of a rectangular workpiece, clicking on the added dimensions in the toolbox₁0.09mm from the upper boundary, the division is completed, and the straight line A₁To a straight line B₁The area between the two layers is a damaged layer;

s4: cutting a cutting layer, making a base line of grid optimization, entering a Part module, selecting a splitting surface sketch in a tool box, selecting the cutting layer, entering a drawing view interface, and clicking a creation line in the tool box: end to end, selecting one point at the lower left corner of the chip layer as a starting point and any point at the upper boundary of the rectangular workpiece as an end point, and drawing an oblique line C₁Oblique line C₁At an angle gamma to the left boundary of the chip bed₂At 40 °, the same applies toDrawing a slant line C on the right side of the cutting layer₁Parallel oblique lines D, C₁And the slope D as the baseline for grid optimization, γ₂The size of the alloy is different from the material characteristics, and the embodiment adopts 18Cr2Ni4 WA;

s5: setting the material parameters of the workpiece to be processed according to the material characteristics of the workpiece to be processed, wherein the material parameters comprise the density, Young modulus, Poisson ratio, melting point, thermal conductivity, thermal expansion coefficient, specific heat, inelastic coefficient and determined cutting amount of the workpiece to be processed, a Johnson-Cook (J-C) constitutive model is selected as a material model, the damage displacement value in the damage evolution is set to be 1-1.5 times of the minimum grid size, the plane stress strain value of the sections of the workpiece and a cutter is set to be 0.3,

wherein σ is the equivalent stress, A is the initial yield stress, B is the material strain strengthening parameter, ε is the equivalent plastic strain, n is the hardening parameter, C is the material strain rate strengthening parameter,&Is equivalent plastic strain rate, epsilon₀Is the reference strain rate of the material, m is the heat softening index of the material, T_mIs melting temperature, T_rFor the purpose of the reference temperature, the temperature,

the values of the relevant parameters are shown in Table 1

TABLE 118 Johnson-Cook constitutive model parameters of Cr2Ni4WA

S6: establishing an analysis step, namely adopting a temperature-displacement coupling analysis step to establish an analysis step and outputting parameters such as cutting force parameters, cutting temperature and the like;

s7: dividing grids for a workpiece, wherein a cutter two-dimensional finite element model is set to be a free step algorithm mainly based on a quadrangle, and carrying out grid encryption processing on a contact part of the cutter finite element model and the workpiece finite element model, namely a cutter round angle, and the method specifically comprises the following steps:

s71: entering a Mesh module, setting the environment bar object option at the top as a component, and selecting the edge cloth in the tool box as the workpiece cloth;

s72: pressing shift to select the upper and lower boundaries, the left and right boundaries of the damaged layer and the upper boundary of the matrix of the whole chip layer, selecting the size in a popped local seed dialog box method, inputting 0.005 in the approximate unit size, and keeping the default settings of other parameters;

s73: selecting a base line for grid optimization, wherein different kinds of arrangement can change the inclination angle of the grid, and the arrangement is carried out according to the actual condition;

s74: selecting a left boundary and a right boundary of a matrix, selecting single precision according to size and offset in a selection method in a popped local seed dialog box method, inputting 0.005 in the minimum size and 0.015 in the maximum size, and keeping default settings of other parameters;

s75: selecting a lower boundary of a matrix, selecting 20 units according to the number in a popped local seed dialog box method, and keeping default settings of other parameters;

s76: the cutting layer and the damage layer are provided with grids with quadrilateral attributes, the algorithm option is minimized grid transition, the base part adopts a free step algorithm with quadrilateral as a main part, a mapping network is selected to be used in a proper place, the unit type selects temperature-displacement coupling in the Explicit, the linear order, the hourglass control selects relaxation rigidity, and other parameters are kept in default settings;

s77: finally, selecting a part grid in a tool box to divide the whole workpiece grid, wherein the cutting part presents a rhombic inclined grid, the damaged layer part presents a rectangular grid, and the base part presents a quadrilateral irregular grid;

s8: carrying out mesh division on a tool model, setting the tool two-dimensional finite element model as a free step algorithm mainly taking a quadrangle, and carrying out mesh encryption processing on a contact part of the tool finite element model and the workpiece finite element model, namely a tool round angle;

s9: setting the contact attribute of the two-dimensional finite element model of the cutter and the two-dimensional finite element model of the workpiece, selecting surface-surface contact, and setting a friction coefficient of 0.3 according to the material of the workpiece to be processed;

s10: setting boundary conditions of a workpiece two-dimensional finite element model and a cutter two-dimensional finite element model, setting the bottom of a matrix to be completely fixed, setting the left side of a workpiece to be a displacement corner, checking all values to input 0, setting the right side of the workpiece to be the displacement corner, checking U1 to input values to be 0, setting a feed machining speed to be 1500, and setting an initial temperature field of the cutter and the workpiece to be 20 ℃;

s11: and saving the model. And operating the Abaqus software, and storing the machined workpiece two-dimensional finite element model obtained by the operation result of the Abaqus software.

Comparative example:

referring to figures 2, 4 and 5,

in the case that the ALE method used by the existing common grid is utilized and the parameters are consistent with the parameters of the embodiment, the analyzed results are compared, and the calculation speed of the simulation processing of the inclined grid implemented according to the scheme is reduced by about 25%, and the corresponding result has no large deviation.

Although the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the details of the embodiments, and various equivalent modifications can be made within the technical spirit of the present invention, and the scope of the present invention is also within the scope of the present invention.

Claims (1)

1. A grid special processing method based on two-dimensional simulation cutting is characterized in that: comprises the following steps of,

s1: establishing a workpiece model and a tool model in Abaqus drawing software, wherein the workpiece model selects a rectangular workpiece, and the specific tool parameters comprise a front angle gamma₁Setting the cutter as a rigid body, wherein the clearance angle alpha, the arc radius r of the cutter tip, the height g of the cutter and the width h of the cutter are equal;

s2: segmenting a workpiece to create a layer of swarfDrawing a straight line A₁The straight line is parallel to the upper boundary of the rectangular workpiece and has a distance from the upper boundary of the rectangular workpiece, the division is completed, and the rectangular workpiece is divided by the straight line A₁The upper half area after being divided is a cutting chip layer, and the lower half area is a matrix;

s3: establishing a damage layer, and drawing a straight line B on the basis of the step S2₁The straight line is parallel to the upper boundary of the rectangular workpiece and has a distance b, b from the upper boundary of the rectangular workpiece<a, the straight line A₁To a straight line B₁The area between the two layers is a damaged layer;

s4: cutting a chip layer, making a base line of grid optimization, selecting one point at the lower left corner of the chip layer as a starting point, taking any point of the upper boundary of the rectangular workpiece as an end point, and drawing an oblique line C₁Oblique line C₁At an angle gamma to the left boundary of the chip bed₂In the same manner, a line C is drawn on the right side of the chip layer₁Parallel oblique lines D, C₁And slash D as a baseline for mesh optimization;

s5: setting the material parameters of the workpiece to be processed according to the material characteristics of the workpiece to be processed, wherein the material parameters comprise the density, Young modulus, Poisson ratio, melting point, thermal conductivity, thermal expansion coefficient, specific heat, inelastic coefficient and determined cutting amount of the workpiece to be processed, a Johnson-Cook (J-C) constitutive model is selected as a material model, the damage displacement value in the damage evolution is set to be 1-1.5 times of the minimum grid size, the plane stress strain value of the sections of the workpiece and the cutter is set to be 0.3,

wherein σ is the equivalent stress, A is the initial yield stress, B is the material strain strengthening parameter, ε is the equivalent plastic strain, n is the hardening parameter, C is the material strain rate strengthening parameter,&Is equivalent plastic strain rate, epsilon₀Is the reference strain rate of the material, m is the heat softening index of the material, T_mIs melting temperature, T_rIs a reference temperature;

s6: establishing an analysis step, namely adopting a temperature-displacement coupling analysis step to establish an analysis step and outputting parameters such as cutting force parameters, cutting temperature and the like;

s7: dividing grids for a workpiece, wherein a cutter two-dimensional finite element model is set to be a free step algorithm mainly based on a quadrangle, and carrying out grid encryption processing on a contact part of the cutter finite element model and the workpiece finite element model, namely a cutter round angle, and the method specifically comprises the following steps:

s71: entering a Mesh module, setting the environment bar object option at the top as a component, and selecting the edge cloth in the tool box as the workpiece cloth;

s72: pressing shift to select the upper and lower boundaries, the left and right boundaries of the damaged layer and the upper boundary of the matrix of the whole chip layer, selecting the size in a popped local seed dialog box method, inputting c in the approximate unit size, and keeping the default settings of other parameters;

s73: selecting a base line for grid optimization, wherein different kinds of arrangement can change the inclination angle of the grid, and the arrangement is carried out according to the actual condition;

s74: selecting a left boundary and a right boundary of a matrix, selecting single precision according to size and offset in a selection method in a popped local seed dialog box method, inputting d in the minimum size, inputting e in the maximum size, and keeping default settings of other parameters;

s75: selecting a lower boundary of a matrix, selecting f according to the number in a popped local seed dialog box method, inputting the f in the unit number, and keeping default settings of other parameters;

s76: the cutting layer and the damage layer are provided with grids with quadrilateral attributes, the algorithm option is minimized grid transition, the base part adopts a free step algorithm with quadrilateral as a main part, a mapping network is selected to be used in a proper place, the unit type selects temperature-displacement coupling in the Explicit, the linear order, the hourglass control selects relaxation rigidity, and other parameters are kept in default settings;

s77: finally, selecting a part grid in a tool box to divide the whole workpiece grid, wherein the cutting part presents a rhombic inclined grid, the damaged layer part presents a rectangular grid, and the base part presents a quadrilateral irregular grid;

s8: carrying out mesh division on a tool model, setting the tool two-dimensional finite element model as a free step algorithm mainly taking a quadrangle, and carrying out mesh encryption processing on a contact part of the tool finite element model and the workpiece finite element model, namely a tool round angle;

s9: setting the contact attribute of the two-dimensional finite element model of the cutter and the two-dimensional finite element model of the workpiece, selecting surface-surface contact, and setting a friction coefficient according to the material of the workpiece to be processed;

s10: setting boundary conditions of a workpiece two-dimensional finite element model and a cutter two-dimensional finite element model, setting the bottom of a matrix to be completely fixed, setting the left side of a workpiece to be a displacement corner, checking all values to input 0, setting the right side of the workpiece to be the displacement corner, checking U1 to input the value to be 0, setting a feed machining speed f, and setting initial temperature fields of the cutter and the workpiece according to the ambient temperature when the workpiece is machined;

s11: and saving the model. And operating the Abaqus software, and storing the machined workpiece two-dimensional finite element model obtained by the operation result of the Abaqus software.

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