A method for optimizing workpiece fixtures in grinding thin-walled, slender shafts

Abstract

This invention belongs to the field of mechanical equipment, and particularly relates to an optimization method for workpiece fixtures used in the grinding of thin-walled, slender shafts. Existing workpiece fixtures for grinding thin-walled, slender shafts suffer from low machining accuracy. This invention uses a large aspect ratio thin-walled, slender shaft as the research object, conducting finite element simulation analysis of external cylindrical grinding, and designs a high-precision workpiece fixture with high support rigidity. The optimal support position of the center rest is determined to be the grinding wheel position. After support, the maximum deformation of the workpiece axis is reduced by 82.77%, meeting the machining requirements. When using this clamping and support scheme, the safe expansion of the hydraulic mandrel is 20.94 μm. This solves the problem of low machining accuracy in existing workpiece fixtures used for grinding thin-walled, slender shafts.

Description

Technical Field

[0001] This invention belongs to the field of mechanical equipment, and in particular relates to an optimization method for workpiece fixtures used in the grinding of thin-walled slender shafts. Background Technology

[0002] GH4169 alloy possesses excellent fatigue resistance, radiation resistance, oxidation resistance, corrosion resistance, as well as good comprehensive properties, weldability, and long-term structural stability. It can be used to manufacture components with various complex shapes and has found wide application in the aerospace, nuclear energy, and petroleum industries. Slender shafts are crucial components in aero-engines, primarily used to transmit torque and support transmission parts. However, due to their poor rigidity, slender shafts are highly susceptible to deformation during grinding due to factors such as grinding force, grinding position, clamping forces at both ends, and support methods, making it difficult to guarantee machining accuracy. Therefore, designing a reasonable clamping device is essential. However, verifying the effectiveness of the clamping device through experiments is time-consuming, labor-intensive, and inefficient.

[0003] ABAQUS is a simulation software that can solve the nonlinear problems of nonconvergence in existing workpiece fixture optimization software. It has a fast calculation convergence speed and is easy to operate and use. However, the external cylindrical grinding process involves material nonlinearity and boundary condition nonlinearity, so ABAQUS is suitable for the simulation of external cylindrical grinding. Many scholars have used finite element software to study the grinding process. For example, Ren Xiaoke et al. studied that under a single force load, the main deformations of the model are radial bending deformation and axial elongation deformation, with radial deformation being the dominant deformation. Jiao Haoyue et al. showed that during the self-rotating grinding of YAG crystals, the normal grinding force decreases with the increase of workpiece and grinding wheel rotation speed, and increases with the increase of grinding wheel feed speed. Zhu Chuanmin et al. found that the thermal residual stress caused by grinding heat is the main cause of grinding deformation of thin-walled parts. Wang Kun et al. found that when silicon dioxide abrasives grind nickel-phosphorus alloy workpieces, the grinding depth is mainly determined by the pressure on the abrasive grains, and the grinding force does not change much with the increase of grinding speed. Yin Bo et al.'s research showed that reducing the grinding depth, increasing the grinding wheel speed, and selecting appropriate workpiece speed and feed rate are beneficial for controlling the surface roughness after ultra-precision grinding of tungsten carbide alloys. Yasmine Charfeddine et al. used implicit dynamics to study the processing effect of simultaneous ball grinding and polishing with AISI 4140, and the results showed that this process leads to a surface layer with compressive residual stress reaching several micrometers in thickness. Wan et al. established a thermo-mechanical coupling model of ZrO based on the finite element method, and the results showed that as the abrasive grains gradually penetrate the workpiece during grinding, workpiece deformation and grinding heat increase, with the grinding temperature reaching its maximum when the abrasive grains completely penetrate the workpiece.

[0004] However, for the design of support devices in the machining of slender shaft parts, most existing technologies rely on static simulations, using constant loads to replace grinding forces to derive the support devices. This fails to accurately simulate the grinding process between the grinding wheel and the workpiece, resulting in low machining accuracy when the designed support devices are used in grinding operations. Summary of the Invention

[0005] The purpose of this invention is to address the problem of low machining accuracy in existing workpiece fixtures used for grinding thin-walled, slender shafts. This invention provides an optimized method for workpiece fixtures used in grinding thin-walled, slender shafts, comprising:

[0006] Step 1: Construct the finite element simulation model for machining the first thin-walled slender shaft;

[0007] The workpiece fixture in the first finite element simulation model for machining thin-walled slender shafts includes: hydraulic core expander and mechanical core expander;

[0008] Step 2: Perform finite element simulation based on the finite element simulation model of the first thin-walled slender shaft to obtain the support position of the central support frame;

[0009] Step 3: Based on the support position of the support frame in the workpiece fixture obtained in Step 2 and the first finite element simulation model of thin-walled slender shaft machining obtained in Step 1, construct the second finite element simulation model of thin-walled slender shaft machining.

[0010] The workpiece fixture of the second thin-walled slender shaft machining finite element simulation model includes: a central support frame, a hydraulic expansion core, and a mechanical expansion core;

[0011] Step 4: Perform finite element simulation based on the finite element simulation model of the second thin-walled slender shaft to obtain the safe expansion amount of the hydraulic expansion core;

[0012] Step 5: Construct the actual workpiece fixture based on the support position of the central support frame obtained in Step 2 and the safe expansion amount of the hydraulic expansion core obtained in Step 4;

[0013] The workpiece fixture for grinding thin-walled slender shafts includes: a central support frame, a hydraulic expansion core, and a mechanical expansion core;

[0014] The thin-walled slender shaft is a machined workpiece, and the material of the thin-walled slender shaft is GH4169 alloy;

[0015] The thin-walled slender shaft is a shaft with an aspect ratio (L / D) greater than 10 and a wall thickness to radius ratio less than 0.1, which is a definition known to those skilled in the art.

[0016] The length-to-diameter ratio is the ratio of the length of the shaft to its diameter.

[0017] The beneficial effects of this invention are as follows:

[0018] This paper conducts finite element simulation analysis on the external cylindrical grinding of thin-walled slender shafts with a large length-to-diameter ratio. A high-precision workpiece fixture with high support rigidity is designed, and the optimal support position of the center rest is determined to be the grinding wheel position. After support, the maximum deformation of the workpiece axis is reduced by 82.77%, meeting the machining requirements. When using this clamping and support scheme, the safe expansion of the hydraulic mandrel is 20.94 μm. Single-factor experiments on grinding parameters and workpiece axis deformation are designed. The results show that the feed rate has almost no effect on the workpiece axis deformation, the grinding wheel speed has a very small effect, while the workpiece speed and feed rate have a significant impact, and the workpiece axis deformation is positively correlated with both. This solves the problem of low machining accuracy in existing workpiece fixtures used for grinding thin-walled slender shafts. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the thin-walled slender shaft structure of the present invention;

[0020] Figure 2 These are schematic diagrams of the thin-walled slender shaft finite element model and the grinding wheel finite element model of the present invention;

[0021] Figure 3 This is a schematic diagram of the actual workpiece clamping method and grinding position according to the present invention;

[0022] Figure 4 This is a schematic diagram of the deformation of the axis without a central frame according to the present invention;

[0023] Figure 5 This is a schematic diagram of the mesh division of the central frame model of the present invention;

[0024] Figure 6 This is a schematic diagram of the deformation of the single-center frame support axis of the present invention;

[0025] Figure 7 This is a schematic diagram of the axial support reaction force curve on the inner surface of the left end of the workpiece according to the present invention;

[0026] Figure 8 This is a schematic diagram of the relationship between clamping force and expansion amount in this invention;

[0027] Figure 9 This is a schematic diagram illustrating the influence of the grinding parameters of the present invention on the workpiece axis deformation. Detailed Implementation

[0028] Specific implementation method one: Combining Figure 1 This invention is described.

[0029] Step 1: Construct the finite element simulation model for machining the first thin-walled slender shaft;

[0030] The workpiece fixture in the first finite element simulation model for machining a thin-walled slender shaft includes: a hydraulic core expander and a mechanical core expander;

[0031] Step 2: Perform finite element simulation based on the finite element simulation model of the first thin-walled slender shaft to obtain the support position of the central support frame;

[0032] Step 3: Based on the support position of the support frame in the workpiece fixture obtained in Step 2 and the first finite element simulation model of thin-walled slender shaft machining obtained in Step 1, construct the second finite element simulation model of thin-walled slender shaft machining.

[0033] The workpiece fixture of the second thin-walled slender shaft machining finite element simulation model includes: a central support frame, a hydraulic expansion core, and a mechanical expansion core;

[0034] Step 4: Perform finite element simulation based on the finite element simulation model of the second thin-walled slender shaft to obtain the safe expansion amount of the hydraulic expansion core;

[0035] Step 5: Construct the actual workpiece fixture based on the support position of the central support frame obtained in Step 2 and the safe expansion amount of the hydraulic expansion core obtained in Step 4;

[0036] The workpiece fixture for grinding thin-walled slender shafts includes: a central support frame, a hydraulic expansion core, and a mechanical expansion core;

[0037] The thin-walled slender shaft is a machined workpiece, and the material of the thin-walled slender shaft is GH4169 alloy;

[0038] The thin-walled slender shaft is a shaft with an aspect ratio (L / D) greater than 10 and a wall thickness to radius ratio less than 0.1, which is a definition known to those skilled in the art.

[0039] The length-to-diameter ratio is the ratio of the shaft's length to its diameter.

[0040] Specific Implementation Method Two: The difference between this implementation method and Specific Implementation Method One is that...

[0041] In step one, a finite element simulation model for machining the first thin-walled slender shaft is constructed; the specific process is as follows:

[0042] Step 11: In the ABAQUS finite element software, set the material properties and parameters of the thin-walled slender shaft to obtain the finite element model of the thin-walled slender shaft;

[0043] Steps 1 and 2: Set the grinding wheel parameters in the ABAQUS finite element software to obtain the finite element model of the grinding wheel;

[0044] Step 13: Set the boundary conditions for the thin-walled slender shaft finite element model and the grinding wheel finite element model in the ABAQUS finite element software to obtain the first thin-walled slender shaft machining finite element simulation model.

[0045] A constitutive model is a mathematical model used to describe the deformation behavior, mechanical properties, and internal properties of a material under external forces. It helps us understand the mechanical behavior of materials and predict their performance in engineering by quantitatively describing the relationships between stress, strain, temperature, and time under different loading conditions (such as tension, compression, and shear).

[0046] In materials science, mechanics, and engineering, constitutive models are widely used to analyze the mechanical properties of materials, such as elasticity, plasticity, and viscosity. Different constitutive models are applicable to different types of materials (such as metals, plastics, ceramics, and composites) and different loading conditions. By using these models, engineers and researchers can predict the performance of materials in practical applications, thereby guiding design, manufacturing, and safety assessments.

[0047] The other steps and parameters are the same as in Specific Implementation Method 1.

[0048] Specific Implementation Method Three: The difference between this implementation method and Specific Implementation Method One is that...

[0049] The material of the thin-walled slender shaft in step one is GH4169 alloy;

[0050] The process involves setting the material properties and parameters of the thin-walled slender shaft in the ABAQUS finite element software to obtain the finite element model of the thin-walled slender shaft; the specific steps are as follows:

[0051] Step 111: The Jhonson-Cook constitutive equation is used as the constitutive model for the GH4169 alloy. The Jhonson-Cook constitutive equation is expressed by the following formula:

[0052]

[0053] Where: σ is the yield stress; A is the yield strength of the material; B is the strain hardening constant of the material; C is the strain rate hardening coefficient; n is the strain hardening coefficient; m is the thermal softening coefficient; ε is the equivalent plastic strain; For reference strain rate; T is the strain rate; T is the instantaneous temperature; T m T is the melting point; r Room temperature;

[0054] Step 112: Set the constitutive model parameters of GH4169 alloy in ABAQUS finite element software according to the Jhonson-Cook constitutive equation parameters; and set the mechanical and physical property parameters of GH4169 high-temperature alloy.

[0055] The constitutive model parameters of the GH4169 alloy include: GH4169 alloy yield strength; GH4169 alloy strain hardening constant; GH4169 alloy strain rate strengthening coefficient; GH4169 alloy strain hardening coefficient; GH4169 alloy thermal softening coefficient; GH4169 alloy melting point; T r Room temperature;

[0056] The mechanical and physical properties of the GH4169 high-temperature alloy include: tensile strength, Poisson's ratio, elastic modulus, fracture strength, density, thermal conductivity, and specific heat capacity.

[0057] The JC constitutive model parameters of the GH4169 high-temperature alloy of this invention are shown in Table 1. Specific data ranges can be obtained through experimental measurements or from universities and research institutions in related fields.

[0058] Table 1 JC constitutive model parameters of GH4169 high-temperature alloy

[0059]

[0060] The mechanical and physical properties of GH4169 high-temperature alloy are shown in Table 2. The specific data range can be obtained from experimental measurements or from universities and research institutions in related fields.

[0061] Table 2 Mechanical and physical properties of GH4169 high-temperature alloy

[0062]

[0063] The parameters of the thin-walled slender shaft in step 113 include: shaft length, minimum shaft diameter, and thin-walled slender shaft grid size;

[0064] The grinding wheel parameters in steps one and two include: grinding wheel diameter, grinding wheel thickness, and grinding wheel mesh size.

[0065] The research object of this invention is a thin-walled slender shaft with a large length-to-diameter ratio. The shaft is 1200 mm long and has a minimum diameter of 35 mm. Its length-to-diameter ratio is extremely high, at 34.3. Its structural schematic diagram is shown below. Figure 1 As shown. The grinding wheel has a diameter of 400mm and a thickness of 45mm.

[0066] During simulation analysis, due to the regular shape of the workpiece, the small computational scale of the hexahedral mesh, and its fast convergence speed, the workpiece was divided into hexahedral meshes. Assuming no deformation of the grinding wheel and the breakage and detachment of abrasive grains, the grinding wheel was simplified as a discrete rigid body. Considering both simulation accuracy and computational speed, the mesh sizes for the workpiece and grinding wheel were determined to be 3mm and 10mm, respectively. The finite element models of the workpiece and grinding wheel after mesh generation are as follows: Figure 2 As shown, the specific setup process is well known to those skilled in the art.

[0067] The other steps and parameters are the same as in one of the specific implementation methods one or two.

[0068] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One through Four in that...

[0069] In steps one and three, boundary conditions are set for the thin-walled slender shaft finite element model and the grinding wheel finite element model in the ABAQUS finite element software to construct the first thin-walled slender shaft machining finite element simulation model; the specific process is as follows:

[0070] Step 131: Determine the support method for the left end and the right end of the thin-walled slender shaft in the workpiece fixture; the specific process is as follows:

[0071] The left end of the finite element model of the thin-walled slender shaft is supported by a hydraulic expansion core; this serves as the support method for the left end of the thin-walled slender shaft.

[0072] The right end of the finite element model of the thin-walled slender shaft is supported by a mechanical expansion core; this serves as the support method for the right end of the thin-walled slender shaft.

[0073] The left end of the finite element model of the thin-walled slender shaft is the end with a larger shaft diameter, and the right end of the finite element model of the thin-walled slender shaft is the end with a smaller shaft diameter;

[0074] The left end is a hydraulic expansion core support, extending 100mm into the hole, and the right end is a mechanical expansion core support, extending 100mm into the hole.

[0075] Hydraulic expansion mandrels utilize hydraulic pressure to support thin-walled, slender shafts. The principle is that a hydraulic system applies pressure to the inside of the expansion mandrel, causing it to expand and come into close contact with the inner wall of the thin-walled, slender shaft, thus clamping and supporting the shaft. In a finite element model, this support method can be simulated as a distributed pressure boundary condition, with pressure acting uniformly on the inner wall of the thin-walled, slender shaft, providing a stable supporting force. The advantages of hydraulic expansion mandrels include providing uniform clamping force, reducing localized stress concentration, and making them suitable for supporting thin-walled parts.

[0076] Mechanical expansion mandrels support thin-walled, slender shafts through mechanical structures (such as a nut tightening to drive a cone or spring). In a finite element model, this support method can be simulated by modeling the deformation and contact of the mechanical structure. For example, the interaction between the mechanical expansion mandrel and the shaft can be simulated by defining contact pairs (such as the contact between the inner wall of the thin-walled, slender shaft and the outer surface of the expansion mandrel). The advantages of mechanical expansion mandrels are their simple structure and convenient operation, but the distribution of clamping force may not be as uniform as that of hydraulic expansion mandrels.

[0077] Step 1, 3, 2: Determine the grinding wheel position, grinding method, and grinding process parameters in the machining of thin-walled, slender shafts;

[0078] The specific experimental parameters for this invention are as follows: the grinding wheel position is 256.8 mm from the left end of the shaft. The grinding method is plunge grinding, and the grinding process parameters are shown in Table 3.

[0079] Table 3 Grinding process parameters

[0080]

[0081] Step 133: Based on the support method of the left end of the thin-walled slender shaft, the support method of the right end of the thin-walled slender shaft, the grinding wheel position, the grinding method, and the grinding process parameters in the machining of thin-walled slender shaft, set the boundary conditions of the finite element model of the thin-walled slender shaft and the grinding wheel finite element model in the ABAQUS finite element software, and construct the first finite element simulation model for machining thin-walled slender shaft.

[0082] The specific configuration of this invention is as follows:

[0083] For example, simulating a hydraulically expanded core support on the left end, extending 100mm into the hole, and a mechanically expanded core support on the right end, also extending 100mm into the hole, then for the finite element model of the thin-walled slender shaft, the XYZ directions of displacement freedom are restricted for the 100mm inner hole at the left end, and the XYZ directions of displacement freedom are restricted for the 100mm inner hole at the right end.

[0084] For example, if the x-direction is the machining axis direction of the thin-walled slender shaft, then the rotational degrees of freedom of the thin-walled slender shaft finite element model in the Y-axis and Z-axis directions are restricted, while the thin-walled slender shaft finite element model is given a rotational speed of 50 r / min around the X-axis;

[0085] For example, if gravity is applied during the simulation of machining, then gravity is applied to the entire workpiece in the finite element model of the thin-walled slender shaft.

[0086] For example, to simulate the grinding process between the grinding wheel and the workpiece during machining, the interaction between the grinding wheel and the workpiece is to set up contact simulation for the finite element model of the thin-walled slender shaft and the finite element model of the grinding wheel.

[0087] For example, in simulating machining, the grinding wheel rotates around the spindle. Therefore, the finite element model of the grinding wheel is restricted in terms of translational degrees of freedom in the X and Z directions, and rotational degrees of freedom in the Y and Z directions. Simultaneously, the finite element model of the grinding wheel is given a rotational speed of 1700 r / min around the X-axis and a feed rate of 100 mm / min around the X-axis.

[0088] The other steps and parameters are the same as those in one of the specific implementation methods one to three.

[0089] Specific Implementation Method Five: The difference between this implementation method and Specific Implementation Methods One to Four is that...

[0090] In step two, finite element simulation is performed based on the machining finite element simulation model of the first thin-walled slender shaft to obtain the support position of the central support frame; the specific process is as follows:

[0091] Step 21: Perform finite element simulation based on the finite element simulation model of the first thin-walled slender shaft to obtain the first simulation data;

[0092] The first simulation data is: the coordinate values ​​of each node of the thin-walled slender shaft during the machining process without a central support frame;

[0093] Step 22: Process the first simulation data to obtain the axial deformation data of the thin-walled slender shaft machining process; and find the position of the maximum axial deformation in the axial deformation data of the thin-walled slender shaft machining process, which is used as the support position of the support frame in the workpiece fixture;

[0094] The other steps and parameters are the same as those in one of the specific implementation methods one to four.

[0095] Specific Implementation Method Six: The difference between this implementation method and Specific Implementation Methods One to Five is that...

[0096] In step two, the simulation data of the thin-walled slender shaft machining process is processed to obtain the axial deformation data of the thin-walled slender shaft machining process; expressed by the formula:

[0097]

[0098] In the formula, i is the node number on the cross section, j is the cross section number, and y ij Let y and z be the values ​​of the i-th node on section j, respectively. ij Let m be the z-coordinate of the i-th node on section j. j This represents the total number of nodes on section j. The x-coordinate, y-coordinate, and x-axis coordinates of the center of section j are respectively.

[0099] According to the deformation of the axis without a central support, such as Figure 4Analysis shows that under the influence of gravity and rotational inertia, the workpiece experiences maximum deformation (25.244 μm) at a distance of 335.7036 mm from the left end of the shaft. The deformation at the left end of the ground shaft section is 25.33 μm, and the deformation at the right end is 26.14 μm, failing to meet the runout requirement of 7.6 μm. Since the location of maximum deformation is near the grinding point, the grinding force has a significant impact on the workpiece's axial deformation, thus affecting the support position of the support frame in the workpiece fixture.

[0100] Other steps and parameters are the same as in any of the specific implementation methods one to five.

[0101] Specific Implementation Method Seven: The difference between this implementation method and Specific Implementation Methods One through Six is ​​that...

[0102] In step four, finite element simulation is performed based on the finite element simulation model of the second thin-walled slender shaft to obtain the safe expansion amount of the hydraulic expansion core.

[0103] Step 41: Perform finite element simulation based on the finite element simulation model of the second thin-walled slender shaft to obtain the second simulation data;

[0104] The second simulation data is: the torque value on the left end surface of the thin-walled slender shaft during machining under the condition of a central support frame;

[0105] Because the workpiece experiences significant deformation at the grinding location, a two-point center rest is considered for addition. The simplified dimensional diagram and mesh representation are shown below. Figure 5 As shown.

[0106] The center rest is supported in the grinding position and subjected to full degree of freedom constraints, assuming no friction between the center rest and the workpiece. Two planes of the center rest are tangent to the machined shaft segment, and these two planes, along with the grinding wheel, form a three-point support for the machined shaft segment. The simulation yields the axial deformation diagram under single center rest support, as shown below. Figure 6 As shown.

[0107] according to Figure 6 The analysis results show that, with the center support, the maximum deformation, measuring 4.35 μm, occurs 381 mm from the left end of the shaft. The deformation at the left end of the ground shaft segment is 3.2 μm, and at the right end, it is 3.74 μm, meeting the runout requirement of 7.6 μm. Compared to the absence of center support, the maximum deformation is reduced by 82.77%, and the deformation at the left and right ends of the ground shaft segment is reduced by 87.37% and 85.69%, respectively. Therefore, this support scheme can effectively reduce deflection deformation during workpiece machining.

[0108] The curve of torque M on the inner surface of the left end of the workpiece changing with time, as shown in the figure. Figure 7 As shown. By Figure 7 It can be seen that the maximum value of torque M is 3664.62 kN.

[0109] The support position of the central support frame is the maximum deformation position of the axis obtained in step 22;

[0110] Step 42: Process the second simulation data to obtain the maximum clamping force N of the hydraulic mandrel during the machining of thin-walled slender shafts under the condition of having a central support frame;

[0111] Step 43: Perform static simulation based on the finite element simulation model of the second thin-walled slender shaft machining process to obtain the relationship between the clamping force and expansion amount of the hydraulic mandrel during the machining process with a central support frame; and calculate the safe expansion amount of the hydraulic mandrel based on the maximum clamping force N of the hydraulic mandrel during the machining process with a central support frame obtained in Step 42.

[0112] The other steps and parameters are the same as those in any of the specific implementation methods one to six.

[0113] Specific Implementation Method Eight: The difference between this implementation method and Specific Implementation Methods One to Seven is that...

[0114] In step four, step two, the second simulation data is processed to obtain the safe expansion amount of the hydraulic mandrel during the machining of a thin-walled, slender shaft under the condition of a central support frame. The specific process is as follows:

[0115] Step 421: Extract the maximum value from the second simulation data as the maximum static friction force f of the hydraulic mandrel during the machining of thin-walled slender shafts under the condition of having a central support frame. max ;

[0116] Step 422: Based on the maximum static friction force f of the hydraulic mandrel obtained in Step 421 max The maximum clamping force of the hydraulic mandrel during the machining of a thin-walled, slender shaft under the condition of a central support frame was calculated; expressed by the formula:

[0117] f max =μN (3)

[0118] In the formula, f max ρ is the maximum static friction force (unit: kN); μ is the coefficient of friction, taken as μ = 0.4; N is the maximum clamping force of the hydraulic mandrel (unit: kN).

[0119] The other steps and parameters are the same as those in any of the specific implementation methods one to seven.

[0120] Specific Implementation Method Nine: The difference between this implementation method and Specific Implementation Methods One through Eight is that...

[0121] In step four-three, static simulation is performed based on the finite element simulation model of the second thin-walled slender shaft machining process to obtain the relationship between the clamping force and expansion amount of the hydraulic mandrel during the machining process of the thin-walled slender shaft under the condition of having a central support frame; and the safe expansion amount of the hydraulic mandrel is calculated based on the maximum clamping force N of the hydraulic mandrel during the machining process of the thin-walled slender shaft under the condition of having a central support frame obtained in step four-two; the specific process is as follows:

[0122] Step 431: Set the boundary conditions for the thin-walled slender shaft in the finite element simulation model of the second thin-walled slender shaft machining; obtain the static simulation model of the thin-walled slender shaft under the condition of having a central support frame;

[0123] In step four-three-one, the boundary conditions of the thin-walled slender shaft in the finite element simulation model for machining the second thin-walled slender shaft are set; thus, a static simulation model of the thin-walled slender shaft with a central support frame is obtained; the specific process is as follows:

[0124] The above radial displacements were applied to the inner surface of the left end of the thin-walled slender shaft in the finite element simulation model of the second thin-walled slender shaft machining.

[0125] It restricts the tangential and axial degrees of freedom of movement, as well as the radial, tangential, and axial degrees of freedom of rotation; the inner surface of the right end of the thin-walled, slender shaft is completely fixed;

[0126] Gravity is applied to the thin-walled slender shaft in the finite element simulation model of the second thin-walled slender shaft machining.

[0127] The expansion process is converted into multiple radial displacements. Since the maximum expansion is 0.070 mm, the radial displacement is divided into seven values ​​with a range of 0-0.035 mm and a difference of 0.005 mm between adjacent values.

[0128] The other steps and parameters are the same as those in one of the specific implementation methods one to eight.

[0129] Specific Implementation Method Ten: The difference between this implementation method and Specific Implementation Methods One through Nine is that...

[0130] In step four-three-two, a static simulation is performed based on the static simulation model of the thin-walled slender shaft under the condition of having a central support frame. This simulation yields the relationship between the clamping force and the expansion amount of the hydraulic mandrel during the machining process of the thin-walled slender shaft under the condition of having a central support frame. Furthermore, based on the maximum clamping force N of the hydraulic mandrel during the machining process of the thin-walled slender shaft under the condition of having a central support frame obtained in step four-two, the safe expansion amount of the hydraulic mandrel is calculated. This is expressed by the formula:

[0131] N = 14.9429ε (4)

[0132] In the formula, N is the maximum clamping force of the hydraulic mandrel (unit: kN), and ε is the expansion amount of the hydraulic mandrel (unit: μm).

[0133] This invention uses static simulation to determine the relationship between the expansion amount and clamping force of a hydraulic mandrel. The expansion process is transformed into multiple radial displacements. Since the maximum expansion amount is 0.070 mm, the radial displacements are divided into seven values ​​ranging from 0 to 0.035 mm, with adjacent values ​​differing by 0.005 mm.

[0134] The relationship curve between clamping force and expansion is as follows: Figure 8 As shown.

[0135] Depend on Figure 8 It can be seen that the clamping force and the expansion amount are directly proportional, which can be expressed by equation (4).

[0136] The other steps and parameters are the same as those in any of the specific implementation methods one to nine.

[0137] Based on simulation analysis of specific implementation methods one through ten, this paper illustrates the influence of grinding parameters on workpiece deformation.

[0138] In the external cylindrical grinding process, the main grinding parameters include the grinding wheel speed v. s Workpiece rotation speed v w Feed rate v f 1. Feed rate f. Under the support conditions described in Section 2.2, a single-factor experiment was designed to investigate the deformation of the workpiece after processing with four combinations of grinding parameters. The specific simulation parameters are shown in Table 4.

[0139] Table 4. Grinding parameters for single-factor experiments

[0140]

[0141] In this study: Groups 1, 2, 3, and 4 maintained constant grinding wheel speed, workpiece speed, and feed rate, but increased the feed speed; Groups 1, 5, 6, and 7 maintained constant workpiece speed, feed rate, and feed rate, but decreased the grinding wheel speed; Groups 1, 8, 9, and 10 maintained constant grinding wheel speed, feed rate, and feed rate, but increased the workpiece speed; Groups 1, 11, 12, and 13 maintained constant grinding wheel speed, workpiece speed, and feed rate, but increased the depth of grinding. By modifying the grinding parameters of the simulation model in section 2.2, the maximum deformation of the axis in each group of experiments was obtained through post-processing, thus revealing the influence of each grinding parameter on the workpiece deformation, such as... Figure 9 As shown.

[0142] Depend on Figure 9 Analysis shows that increasing the workpiece rotational speed leads to an increase in the rotational inertial force on the workpiece, thus increasing the axial deformation of the workpiece. Increasing the grinding depth leads to an increase in the pressure exerted by the grinding wheel on the workpiece and an increase in the radial grinding force on the workpiece, thus increasing the axial deformation of the workpiece. Changes in feed rate and grinding wheel speed have almost no effect on the axial deformation of the workpiece.

[0143] The above description is merely of preferred embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention, and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A method for optimizing workpiece fixtures in the grinding of thin-walled, slender shafts, characterized in that, include: Step 1: Construct the finite element simulation model for machining the first thin-walled slender shaft; The workpiece fixture in the first finite element simulation model for machining a thin-walled slender shaft includes: a hydraulic core expander and a mechanical core expander; Step 2: Perform finite element simulation based on the finite element simulation model of the first thin-walled slender shaft to obtain the support position of the central support frame; Step 3: Based on the support position of the support frame in the workpiece fixture obtained in Step 2 and the first finite element simulation model of thin-walled slender shaft machining obtained in Step 1, construct the second finite element simulation model of thin-walled slender shaft machining. The workpiece fixture of the second thin-walled slender shaft machining finite element simulation model includes: a central support frame, a hydraulic expansion core, and a mechanical expansion core; Step 4: Perform finite element simulation based on the machining finite element model of the second thin-walled slender shaft to obtain the safe expansion amount of the hydraulic expansion core; the specific process is as follows: Step 41: Perform finite element simulation based on the finite element simulation model of the second thin-walled slender shaft to obtain the second simulation data; The second simulation data is: the torque value on the left end surface of the thin-walled slender shaft during machining under the condition of a central support frame; The support position of the central support frame is the maximum deformation position of the axis obtained in step 22; Step 42: Process the second simulation data to obtain the maximum clamping force N of the hydraulic mandrel during the machining of thin-walled slender shafts under the condition of having a central support frame; Step 43: Perform static simulation based on the finite element simulation model of the second thin-walled slender shaft machining to obtain the relationship between the clamping force and expansion amount of the hydraulic mandrel during the machining process of the thin-walled slender shaft under the condition of having a central support frame; and calculate the safe expansion amount of the hydraulic mandrel based on the maximum clamping force N of the hydraulic mandrel during the machining process of the thin-walled slender shaft under the condition of having a central support frame obtained in Step 42. Step 5: Construct the actual workpiece fixture based on the support position of the central support frame obtained in Step 2 and the safe expansion amount of the hydraulic expansion core obtained in Step 4.

2. The workpiece fixture optimization method for grinding thin-walled slender shafts according to claim 1, characterized in that, In step one, a finite element simulation model for machining the first thin-walled slender shaft is constructed; the specific process is as follows: Step 11: In the ABAQUS finite element software, set the material properties and parameters of the thin-walled slender shaft to obtain the finite element model of the thin-walled slender shaft; Steps 1 and 2: Set the grinding wheel parameters in the ABAQUS finite element software to obtain the finite element model of the grinding wheel; Step 13: Set the boundary conditions for the thin-walled slender shaft finite element model and the grinding wheel finite element model in the ABAQUS finite element software to obtain the first thin-walled slender shaft machining finite element simulation model.

3. The workpiece fixture optimization method for grinding thin-walled slender shafts according to claim 2, characterized in that, The material of the thin-walled slender shaft in step one is GH4169 alloy; The process involves setting the material properties and parameters of the thin-walled slender shaft in the ABAQUS finite element software to obtain the finite element model of the thin-walled slender shaft; the specific steps are as follows: Step 111: The Jhonson-Cook constitutive equation is used as the constitutive model for the GH4169 alloy. The Jhonson-Cook constitutive equation is expressed by the following formula: Where: σ is the yield stress; A is the yield strength of the material; B is the strain hardening constant of the material; C is the strain rate hardening coefficient; n is the strain hardening coefficient; m is the thermal softening coefficient; ε is the equivalent plastic strain; For reference strain rate; T is the strain rate; T is the instantaneous temperature; T m T is the melting point; r Room temperature; Step 112: Set the constitutive model parameters of GH4169 alloy in ABAQUS finite element software according to the Jhonson-Cook constitutive equation parameters; and set the mechanical and physical property parameters of GH4169 high-temperature alloy. The constitutive model parameters of the GH4169 alloy include: GH4169 alloy yield strength; GH4169 alloy strain hardening constant; GH4169 alloy strain rate strengthening coefficient; GH4169 alloy strain hardening coefficient; GH4169 alloy thermal softening coefficient; GH4169 alloy melting point; T r Room temperature; The mechanical and physical properties of the GH4169 high-temperature alloy include: tensile strength, Poisson's ratio, elastic modulus, fracture strength, density, thermal conductivity, and specific heat capacity. The parameters of the thin-walled slender shaft in step one include: shaft length, minimum shaft diameter, and thin-walled slender shaft grid size; The grinding wheel parameters in steps one and two include: grinding wheel diameter, grinding wheel thickness, and grinding wheel mesh size.

4. The workpiece fixture optimization method for grinding thin-walled slender shafts according to claim 3, characterized in that, In steps one and three, boundary conditions are set for the thin-walled slender shaft finite element model and the grinding wheel finite element model in the ABAQUS finite element software to construct the first thin-walled slender shaft machining finite element simulation model; the specific process is as follows: Step 131: Determine the support method for the left end and the right end of the thin-walled slender shaft in the workpiece fixture; the specific process is as follows: The left end of the finite element model of the thin-walled slender shaft is supported by a hydraulic expansion core; this serves as the support method for the left end of the thin-walled slender shaft. The right end of the finite element model of the thin-walled slender shaft is supported by a mechanical expansion core; this serves as the support method for the right end of the thin-walled slender shaft. Step 1, 3, 2: Determine the grinding wheel position, grinding method, and grinding process parameters in the machining of thin-walled, slender shafts; Step 133: Based on the support methods of the left and right ends of the thin-walled slender shaft, the grinding wheel position, grinding method, and grinding process parameters in the machining of thin-walled slender shafts, set the boundary conditions of the finite element model of the thin-walled slender shaft and the grinding wheel finite element model in the ABAQUS finite element software to construct the first finite element simulation model for the machining of thin-walled slender shafts.

5. A method for optimizing workpiece fixtures in grinding thin-walled slender shafts according to claim 4, characterized in that, In step two, finite element simulation is performed based on the machining finite element simulation model of the first thin-walled slender shaft to obtain the support position of the central support frame; the specific process is as follows: Step 21: Perform finite element simulation based on the finite element simulation model of the first thin-walled slender shaft to obtain the first simulation data; The first simulation data is: the coordinate values ​​of each node of the thin-walled slender shaft during the machining process without a central support frame; Step 22: Process the first simulation data to obtain the axial deformation data of the thin-walled slender shaft machining process; and find the position of the maximum axial deformation in the axial deformation data of the thin-walled slender shaft machining process, which is used as the support position of the support frame in the workpiece fixture.

6. The workpiece fixture optimization method for grinding thin-walled slender shafts according to claim 5, characterized in that, In step two, the simulation data of the thin-walled slender shaft machining process is processed to obtain the axial deformation data of the thin-walled slender shaft machining process; expressed by the formula: In the formula, i is the node number on the cross section, j is the cross section number, and y ij Let y and z represent the coordinates of the i-th node on section j, respectively. ij Let m be the z-coordinate of the i-th node on section j. j This represents the total number of nodes on section j. These are the x-coordinate, y-coordinate, and axis coordinates of the center of section j, respectively.

7. A method for optimizing workpiece fixtures in grinding thin-walled slender shafts according to claim 6, characterized in that, In step four, step two, the second simulation data is processed to obtain the safe expansion amount of the hydraulic mandrel during the machining of a thin-walled, slender shaft under the condition of a central support frame. The specific process is as follows: Step 421: Extract the maximum value from the second simulation data as the maximum static friction force f of the hydraulic mandrel during the machining of thin-walled slender shafts under the condition of having a central support frame. max ; Step 422: Based on the maximum static friction force f of the hydraulic mandrel obtained in Step 421 max The maximum clamping force of the hydraulic mandrel during the machining of a thin-walled, slender shaft under the condition of a central support frame was calculated; expressed by the formula: f max =μN (3) In the formula, f max is the maximum static friction force; μ is the coefficient of friction, taken as μ = 0.4; N is the maximum clamping force of the hydraulic mandrel.

8. A method for optimizing workpiece fixtures in grinding thin-walled slender shafts according to claim 7, characterized in that, In step four, static simulation is performed based on the finite element simulation model of the second thin-walled slender shaft to obtain the relationship between the clamping force and the expansion amount of the hydraulic mandrel during the machining process of the thin-walled slender shaft under the condition of having a central support frame. Based on the maximum clamping force N of the hydraulic mandrel during the machining of thin-walled slender shafts under the condition of having a central support frame obtained in step 42, the safe expansion amount of the hydraulic expansion mandrel is calculated; the specific process is as follows: Step 431: Set the boundary conditions for the thin-walled slender shaft in the finite element simulation model of the second thin-walled slender shaft machining; obtain the static simulation model of the thin-walled slender shaft under the condition of having a central support frame; Step 432: Perform static simulation based on the static simulation model of the thin-walled slender shaft with a central support frame to obtain the relationship between the clamping force and the expansion amount of the hydraulic mandrel during the machining process of the thin-walled slender shaft with a central support frame. Based on the maximum clamping force N of the hydraulic mandrel during the machining of thin-walled slender shafts under the condition of having a central support frame obtained in step 42, the safe expansion amount of the hydraulic expansion mandrel is calculated.

9. A method for optimizing workpiece fixtures in grinding thin-walled slender shafts according to claim 8, characterized in that, In step four, three, two, static simulation is performed based on the static simulation model of the thin-walled slender shaft under the condition of having a central support frame, to obtain the relationship between the clamping force and the expansion amount of the hydraulic mandrel during the machining process of the thin-walled slender shaft under the condition of having a central support frame. Based on the maximum clamping force N of the hydraulic mandrel during the machining of thin-walled slender shafts under the condition of having a central support frame obtained in step 42, the safe expansion amount of the hydraulic expansion mandrel is calculated; expressed by the formula: N = 14.9429ε (4) In the formula, N is the maximum clamping force of the hydraulic mandrel, and ε is the expansion amount of the hydraulic mandrel.

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