Cutting force prediction method based on in-situ laser auxiliary heating orthogonal milling

Abstract

The invention discloses a cutting force prediction method based on in-situ laser auxiliary heating orthogonal milling, and belongs to the technical field of laser auxiliary heating machining.The cutting force prediction method comprises the steps that the instantaneous meshing angle and the instantaneous cutting thickness of milling cutter teeth are obtained; according to the environment temperature and the workpiece temperature, obtained based on the laser temperature finite element model, of the laser irradiation area, the shearing force coefficient and the ploughing force coefficient in the three directions are obtained; establishing a cutting force model of the milling infinitesimal of the milling cutter under the cutter coordinate system O1X1Y1Z1 so as to obtain three-way instantaneous cutting force borne by the milling infinitesimal of the milling cutter; the three-way instantaneous cutting force is converted into a workpiece coordinate system O0X0Y0Z0, integral summation is conducted within the axial cutting depth range of the cutting edge of the milling cutter, and meanwhile, the three-way cutting force borne by the milling cutter under the workpiece coordinate system O0X0Y0Z0 is obtained by combining a laser temperature threshold function. According to the method, the influence of tool wear evolution and workpiece material thermal softening is considered, and the cutting force of in-situ laser auxiliary heating orthogonal milling can be accurately predicted.

Description

Technical Field

[0001] The invention belongs to the technical field of laser assisted heat processing, and in particular relates to a cutting force prediction method based on in-situ laser assisted heat orthogonal milling. Background Art

[0002] In the fields of aerospace, thermodynamics, photonics and optical imaging technology, with the rapid development of these technologies, hard-to-process materials such as hard and brittle materials have become the preferred materials for key components due to their excellent physical properties, especially in applications working in harsh environments. Given the characteristics of these materials that reduce hardness and brittleness at high temperatures, laser-assisted processing technology has become an effective means of processing such difficult-to-process materials, with advantages including material softening, reduced cutting forces, and improved machinability and surface processing quality of difficult-to-process materials.

[0003] According to the different positions of the laser beam, laser assisted heat processing technology can be divided into preheating laser assisted heat processing and in-situ laser assisted heat processing. Since the laser irradiation of preheating laser assisted heat processing is limited to the surface of the workpiece, the underlying material cannot be fully heated, thus limiting its process effect. In contrast, in-situ laser assisted heat processing technology overcomes the limitations of preheating laser assisted heat processing, can adapt to more diverse tool path processing requirements, and can obtain better quality processing results.

[0004] In order to provide theoretical and data support for the optimization of process parameters of in-situ laser assisted heat processing, it is urgent to construct an in-situ laser assisted heat orthogonal milling force model to predict the cutting force of in-situ laser assisted heat orthogonal milling. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a cutting force prediction method based on in-situ laser-assisted heat-assisted orthogonal milling, which takes into account the influence of tool wear evolution and thermal softening of workpiece material, and can accurately predict the cutting force of in-situ laser-assisted heat-assisted orthogonal milling.

[0006] The present invention provides the following technical solutions:

[0007] A cutting force prediction method based on in-situ laser assisted heat orthogonal milling, comprising:

[0008] Based on the milling cutting parameters and the geometric parameters of the tool, the instantaneous meshing angle and the instantaneous cutting thickness of the milling cutter teeth are obtained;

[0009] According to the ambient temperature and the workpiece temperature in the laser irradiation area obtained based on the laser temperature finite element model, the shear force coefficient and the plowing force coefficient in three directions are obtained;

[0010] Based on the instantaneous meshing angle of the milling cutter teeth, the instantaneous cutting thickness, the three-dimensional shear force coefficient and the plowing force coefficient, the cutting force model of the milling cutter milling microelement in the tool coordinate system O1X1Y1Z1 is established to obtain the three-dimensional instantaneous cutting force on the milling cutter milling microelement;

[0011] The three-dimensional instantaneous cutting force is converted to the workpiece coordinate system O0X0Y0Z0, and the integral sum is performed within the axial cutting depth range of the milling cutter cutting edge. At the same time, combined with the laser temperature threshold function, the three-dimensional cutting force exerted on the milling cutter in the workpiece coordinate system O0X0Y0Z0 is obtained.

[0012] Optionally, the instantaneous engagement angle and instantaneous cutting thickness of the milling cutter teeth are obtained based on the milling cutting parameters and the geometric parameters of the tool, wherein the milling cutting parameters include spindle speed, feed rate and axial cutting depth; the geometric parameters of the tool include: milling cutter diameter, milling cutter helix angle, milling cutter rake angle and milling cutter tip arc radius;

[0013] Among them, the instantaneous meshing angle Φ of the hth milling cutter tooth on the milling cutter h for:

[0014]

[0015] The instantaneous cutting thickness h of the hth milling cutter tooth on the milling cutter is:

[0016]

[0017] Among them, f c is the feed rate, z is the total number of milling cutter teeth, n is the milling cutter speed, Φ U1 is the micro-element angle of the first cutting bottom edge, γ is the helix angle of the milling cutter, d is the diameter of the milling cutter, Δz 1j is the axial cutting depth.

[0018] Optionally, based on the instantaneous meshing angle of the milling cutter teeth, the instantaneous cutting thickness, the three-dimensional shear force coefficient and the plowing force coefficient, a cutting force model of the milling cutter milling microelement under the tool coordinate system O1X1Y1Z1 is established to obtain the three-dimensional instantaneous cutting force of the milling cutter milling microelement, wherein the three-dimensional instantaneous cutting force includes: the instantaneous tangential force dF t , instantaneous radial force dF r and instantaneous axial force dF a , the three-way shear force coefficient and plough shear force coefficient include: the shear force coefficient corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force, and the plough shear force coefficient corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force;

[0019] The cutting force model of the milling cutter microelement under the tool coordinate system O1X1Y1Z1 is:

[0020]

[0021] Among them, Φ h is the instantaneous engagement angle of the hth milling cutter tooth on the milling cutter, h j is the instantaneous cutting thickness of the hth milling cutter tooth on the milling cutter, Δz 1j is the axial cutting depth, K tc , K rc , K ac are the shear force coefficients corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force, respectively, K te , K re , K ae are the plowing force coefficients corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force respectively.

[0022] Optionally, the three-dimensional shear force coefficient and the plowing force coefficient are obtained according to the ambient temperature and the workpiece temperature of the laser irradiation area obtained based on the laser temperature finite element model, wherein the three-dimensional shear force coefficient and the plowing force coefficient include: the shear force coefficient corresponding to the instantaneous tangential force, the instantaneous radial force and the instantaneous axial force, and the plowing force coefficient corresponding to the instantaneous tangential force, the instantaneous radial force and the instantaneous axial force;

[0023] Obtain the shear force coefficient corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force. The specific formula is:

[0024]

[0025] Obtain the plow shear force coefficient corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force. The specific formula is:

[0026]

[0027] Among them, K te , K re , K ae are the plow shear force coefficients corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force respectively; K tc , K rc , K ac are the shear force coefficients corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force, τ s is the shear flow stress, is the shear angle, i n is the local tilt angle, β a is the friction angle on the normal plane of the milling cutter microelement, α n The front angle of the milling cutter element, η c is the cutting flow angle, σ p is the normal stress of the milling cutter microelement plow section, τ pis the shear stress of the milling cutter microelement plow section, R0 is the sector radius, θ0, η0 and γ0 are the three angles in the slip line field model.

[0028] Optionally, the shear flow stress τ s for:

[0029]

[0030] Among them, A, B, C, n and m are the Johnson-Cook constitutive parameters of the workpiece material; ε and are the equivalent strain and the equivalent strain rate, is the reference strain rate, T m is the melting point of the workpiece material, T r is the ambient temperature, T s is the temperature of the main shear surface of the cutting edge microelement;

[0031] Cutting edge microelement main shear surface temperature T s for:

[0032]

[0033] Wherein, T is the workpiece temperature in the laser irradiation area, τ0 is the initial pure shear yield strength, ρ is the density of the workpiece material, c is the specific heat capacity of the workpiece material; u0 is the non-uniform coefficient.

[0034] Optionally, the three-dimensional instantaneous cutting force is converted to the workpiece coordinate system O0X0Y0Z0, integrated and summed within the axial cutting depth range of the milling cutter cutting edge, and combined with the laser temperature threshold function to obtain the three-dimensional cutting force exerted on the milling cutter in the workpiece coordinate system O0X0Y0Z0, specifically including:

[0035] Convert the three-dimensional instantaneous cutting force to the workpiece coordinate system O0X0Y0Z0;

[0036]

[0037] in, and are the micro-element cutting forces in the X, Y and Z directions in the workpiece coordinate system, λ is the micro-element motion of the tool coordinate system per unit time in the workpiece coordinate system; dF t 、dF r and dF a are the instantaneous tangential force, instantaneous radial force and instantaneous axial force, respectively, Φ h is the instantaneous engagement angle of the hth milling cutter tooth on the milling cutter;

[0038] The laser temperature threshold function includes the cutting force variation values ​​caused by the workpiece temperature in the laser irradiation area in the X, Y and Z directions of the workpiece coordinate system, specifically:

[0039]

[0040] Among them, F hx 、F hy and F hz are the cutting force changes caused by the workpiece temperature in the laser irradiation area in the X, Y and Z directions of the workpiece coordinate system, T is the workpiece temperature in the laser irradiation area, K th , K rh , K ah , K tf , K rf and K af are the six cutting force coefficients related to the workpiece temperature in the laser irradiation area, which are obtained by fitting the average force coefficient in the tests with different laser powers;

[0041] The three-dimensional cutting force on the milling cutter in the workpiece coordinate system O0X0Y0Z0 includes the cutting forces in the X, Y and Z directions in the workpiece coordinate system, specifically:

[0042]

[0043] in, and are the cutting forces in the X, Y and Z directions in the workpiece coordinate system; z is the total number of milling cutter teeth, Δz 1j is the axial cutting depth.

[0044] Optionally, the three-dimensional shear force coefficient and plowing force coefficient are obtained according to the ambient temperature and the workpiece temperature in the laser irradiation area obtained based on the laser temperature finite element model, including constructing the laser temperature finite element model, and the specific process is:

[0045] The convective heat transfer coefficient of the cutting fluid and the laser absorption rate after adding the cutting fluid are obtained by experimental method;

[0046] Establish a workpiece finite element model based on workpiece size and material parameters;

[0047] Based on the workpiece finite element model, the boundary conditions of convective heat transfer are obtained through the convective heat transfer coefficient, and the laser heat source load is applied on the workpiece surface in combination with the laser absorptivity to establish the laser temperature finite element model.

[0048] Optionally, based on the workpiece finite element model, the boundary conditions of convective heat transfer are obtained through the convective heat transfer coefficient, and a laser heat source load is applied on the workpiece surface in combination with the laser absorptivity to establish a laser temperature finite element model, which specifically includes:

[0049] Define the laser heat source. The equation of the laser heat source is:

[0050]

[0051] Where q(x, y) is the power density of the laser, α is the laser absorptivity, P is the laser power, r0 is the radius of the laser irradiation area, (x, y) is the coordinate of the center of the laser irradiation area on the workpiece surface, τ is the unit time, ω is the laser pulse width, T ω is the laser light emission period;

[0052] Establish the heat conduction equation;

[0053]

[0054] Obtain boundary conditions for convective heat transfer;

[0055]

[0056] Where ρ is the density of the workpiece material, C is the specific heat capacity of the workpiece material, k is the thermal conductivity of the material, and ε n is the emissivity of the workpiece material, σ is the Stefan-Boltzmann constant, is the heat generated per unit volume of the laser irradiation area, T is the workpiece temperature in the laser irradiation area, T0 is the initial temperature of the workpiece, x, y, z are the coordinates of the center of the laser irradiation area in three-dimensional space, and h is the convective heat transfer coefficient.

[0057] A laser temperature finite element model was established by using Abaqus software.

[0058] Optionally, in establishing the workpiece finite element model according to the workpiece size and material parameters, the material parameters include density, constitutive model parameters, latent heat, thermal conductivity, thermal expansion and specific heat capacity.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] (1) The present invention considers the competitive mechanism between the workpiece temperature in the laser irradiation area and the thermal softening of the workpiece material and the evolution of tool wear, introduces a laser temperature threshold function, and realizes the accurate prediction of the in-situ laser assisted heating orthogonal milling force, thereby providing theoretical guidance for the optimization of process parameters and improving applicability.

[0061] (2) The present invention determines the convective heat transfer coefficient and the laser absorptivity through experiments, and combines theoretical calculation and finite element simulation technology when constructing a laser temperature finite element model, thereby improving the prediction accuracy of the workpiece temperature in the laser irradiation area. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It is a flow chart of the cutting force prediction method based on in-situ laser assisted heat orthogonal milling of the present invention;

[0063] Figure 2is a schematic diagram of a convective heat transfer experimental device of the present invention;

[0064] Figure 3 It is a schematic diagram of the laser absorption rate experimental device of the present invention;

[0065] Figure 4 It is a cloud diagram of the workpiece finite element model and the laser temperature finite element model of the present invention;

[0066] Figure 5 is a temperature-time curve diagram of the laser temperature finite element model of the present invention;

[0067] Figure 6 It is a schematic diagram of the cutting edge microelement of the present invention.

[0068] Figure 7 It is a schematic diagram of the three-way cutting force prediction structure given in the second embodiment of the present invention.

[0069] Markings in the figure are: 1 is alumina thermal insulation ceramic, 2 is electric heating plate, 3 is workpiece, 4 is cutting fluid nozzle, 5 is thermocouple, 6 is data acquisition device, 7 is monitoring computer 7, 8 is power controller, and 9 is laser beam. DETAILED DESCRIPTION

[0070] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0071] It should be noted that the term "comprises" and any variations of the term in the specification and claims of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or inherent to these processes, methods, products or apparatus.

[0072] Example 1

[0073] As shown in FIG1 , a cutting force prediction method based on in-situ laser assisted heat orthogonal milling is provided, comprising the following steps (S1-S4):

[0074] Sl: Based on the milling cutting parameters and the geometric parameters of the tool, the instantaneous engagement angle and instantaneous cutting thickness of the milling cutter teeth are obtained.

[0075] Specifically, the cutting parameters of milling include spindle speed, feed rate and axial cutting depth; the geometric parameters of the tool include: milling cutter diameter, milling cutter helix angle, milling cutter rake angle and milling cutter tip arc radius.

[0076] Among them, the instantaneous meshing angle Φ of the hth milling cutter tooth on the milling cutter h for:

[0077]

[0078] The instantaneous cutting thickness h of the hth milling cutter tooth on the milling cutter is:

[0079]

[0080] Among them, f c is the feed rate (mm / min), z is the total number of milling cutter teeth, n is the milling cutter speed (r / min), Φ U1 is the micro-angle of the first cutting edge, γ is the helix angle of the milling cutter (rad), d is the diameter of the milling cutter (mm), Δz 1j is the axial cutting depth.

[0081] Specifically, the first cutting edge micro-angle Φ U1 for:

[0082]

[0083] During the milling process, the effective milling radius of the side edge of the milling cutter is 0~π, so Φ U1 Correct and round, [nτ / 60] is the rounding function, τ is the unit time (s).

[0084] S2: Obtain the three-dimensional shear force coefficient and plowing force coefficient according to the ambient temperature and the workpiece temperature in the laser irradiation area obtained based on the laser temperature finite element model.

[0085] Specifically, step S2 includes the following sub-steps (S21-S24):

[0086] S2l: The convective heat transfer coefficient of the cutting fluid and the laser absorption rate after adding the cutting fluid are obtained through experimental methods.

[0087] Specifically, the experiment is set up according to the calculation principle of the convective heat transfer coefficient and the laser absorptivity, and the convective heat transfer coefficient and the laser absorptivity are calculated in combination with the temperature measured in the experiment.

[0088] Step S21 includes the following sub-steps (S211-S212): S211: Acquisition of convective heat transfer coefficient.

[0089] The convective heat transfer coefficient is obtained by Figure 2 The experimental device shown specifically includes: alumina thermal insulation ceramic 1, electric heating plate 2, workpiece 3, cutting fluid nozzle 4, thermocouple 5, data acquisition device 6, monitoring computer 7 and power controller 8.

[0090] The electric heating plate 2 is made of the same material as the workpiece 3, and is connected to a power controller 8 to control the power of the electric heating plate 2; the alumina insulating ceramic 1 is placed under the electric heating plate 2, the workpiece 3 is placed on the electric heating plate 2, the thermocouple 5 is pasted on the surface of the workpiece 3, and is connected to a data acquisition device 6. After the temperature stabilizes, a monitoring computer 7 is used to collect temperature data; the cutting fluid nozzle 4 is placed at a height of 15 cm from the center of the workpiece. For specific experimental steps, refer to the prior art.

[0091] According to formula (4), the cutting fluid convection heat transfer coefficient h is calculated as:

[0092]

[0093] Among them, P e is the heating power of the heating plate (W), T h is the surface temperature of the workpiece under heating by the electric heating plate (K), T f is the stable surface temperature of the workpiece after adding cutting fluid (K). A is the contact surface area between cutting fluid and workpiece (m 2 ).

[0094] S212: Obtaining laser absorption rate

[0095] The laser absorption rate is obtained by Figure 3 The experimental device shown specifically includes: alumina thermal insulation ceramic 1, workpiece 3, cutting fluid nozzle 4, thermocouple 5, data acquisition device 6, monitoring computer 7, and laser beam 9 emitted by the laser.

[0096] Alumina thermal insulation ceramic 1 is placed under the workpiece 3; thermocouple 5 is pasted on the surface of workpiece 3, 2 mm away from the center of laser beam 9 emitted by the laser, and connected to data acquisition device 6, and temperature data is collected using monitoring computer 7 after the temperature stabilizes; cutting fluid nozzle 4 is placed at a height of 15 cm from the center of the workpiece; specific experimental steps refer to the prior art.

[0097] The laser absorption rate α is calculated according to formula (5):

[0098]

[0099] Wherein, P is the laser power (W), T1 is the temperature without laser after adding cutting fluid (K), and T2 is the stable temperature of laser after adding cutting fluid (K).

[0100] S22: Establish a finite element model of the workpiece according to the workpiece size and material parameters; Figure 4 As shown in (a), Figure 4 (a) is a structural schematic diagram of the workpiece finite element model.

[0101] Specifically, the material parameters include density, constitutive model parameters, latent heat, thermal conductivity, thermal expansion and specific heat capacity; the workpiece finite element model can be generated by Abaqus software.

[0102] S23: Based on the workpiece finite element model, the boundary conditions of convective heat transfer are obtained through the convective heat transfer coefficient, and the laser heat source load is applied on the workpiece surface in combination with the laser absorptivity to establish a laser temperature finite element model.

[0103] Step S23 further includes the following sub-steps (S231-S234).

[0104] S23l: Define the laser heat source. The distribution of the laser heat source density conforms to the Gaussian distribution. The equation of the laser heat source is:

[0105]

[0106] Where q(x, y) is the power density of the laser, α is the laser absorptivity, P is the laser power (W), r0 is the radius of the laser irradiation area (mm), (x, y) is the coordinate of the center of the laser irradiation area on the workpiece surface, τ is the unit time (s), ω is the laser pulse width, and T ω is the laser light emission period.

[0107] S232: Establish heat conduction equation;

[0108]

[0109] S233: Obtaining boundary conditions for convective heat transfer;

[0110]

[0111] Where ρ is the density of the workpiece material, C is the specific heat capacity of the workpiece material, k is the thermal conductivity of the material, and ε n is the emissivity of the workpiece material, σ is the Stefan-Boltzmann constant, is the heat generated per unit volume of the laser irradiation area, T is the workpiece temperature in the laser irradiation area, T0 is the initial temperature of the workpiece, x, y, z are the coordinates of the center of the laser irradiation area in three-dimensional space, and h is the convection heat transfer coefficient of the cutting fluid.

[0112] S234: By using Abaqus software, a laser temperature finite element model is established, such as Figure 4 (b) and Figure 5 As shown, Figure 4 (b) is the cloud diagram of the laser temperature finite element model.

[0113] S24: Obtain three-dimensional shear force coefficients and plowing force coefficients according to the ambient temperature and the workpiece temperature in the laser irradiation area obtained based on the laser temperature finite element model.

[0114] Specifically, the three-dimensional shear force coefficient and ploughing force coefficient include: the shear force coefficient corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force, and the ploughing force coefficient corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force.

[0115] Given ambient temperature T r , and then the workpiece temperature T in the laser irradiation area is obtained through the laser temperature finite element model; considering the softening of the workpiece temperature in the laser irradiation area, the solution method of the three-way shear force coefficient and the three-way plow shear force coefficient is as follows:

[0116] Step S241: Obtain the shear force coefficient corresponding to the instantaneous tangential force, the instantaneous radial force and the instantaneous axial force. The specific formula is:

[0117]

[0118] In the formula, K te , K re , K ae are the plowing force coefficients corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force respectively; τ s is the shear flow stress (MPa), which can be calculated by equation (11) as the laser heating temperature changes. n is the local inclination angle, which is regarded as the milling cutter helix angle γ. η c is the chip flow angle, which is similar to the local inclination angle. a is the friction angle on the normal plane of the milling cutter microelement, α n is the front angle of the milling cutter element, is the shear angle.

[0119] β a is the friction angle on the normal plane of the milling cutter microelement, α n is the front angle of the milling cutter element, The solution formula for the shear angle is:

[0120]

[0121] Among them, μ a is the apparent friction coefficient of the front cutting edge, μ is the sliding friction coefficient, which can be obtained in a single factor experiment by the inverse identification method. τ1 is the shear yield stress of the bonding zone on the front cutting edge, P0 is the normal stress at the tip of the front cutting edge. ξ is an exponential constant.

[0122] Shear flow stress τ s for:

[0123]

[0124] Among them, A, B, C, n and m are the Johnson-Cook constitutive parameters of the workpiece material; ε and are the equivalent strain and the equivalent strain rate, is the reference strain rate, T m is the melting point of the workpiece material (K), T r is the ambient temperature (K), T s is the temperature of the main shear surface of the cutting edge microelement;

[0125] Cutting edge microelement main shear surface temperature T s for:

[0126]

[0127] Where T is the workpiece temperature in the laser irradiation area (K), which is obtained from the laser temperature finite element model. τ0 is the initial pure shear yield strength (MPa), ρ is the density of the material (g / cm 3 ), c is the specific heat capacity of the material (J / kg·K). u0 is the non-uniform coefficient.

[0128] The unequal division coefficient u0 is:

[0129]

[0130] Step S242: According to the Waldorf slip line field model, the plowing force coefficient corresponding to the instantaneous tangential force, the instantaneous radial force and the instantaneous axial force is obtained. The specific formula is:

[0131]

[0132] Among them, K tc , K rc , K ac are the shear force coefficients corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force, σ p is the normal stress of the milling cutter microelement plowing surface (MPa), τ p is the shear stress of the milling cutter microelement plow section (MPa), and the calculation method is shown in formula (15). R0 is the sector radius, and θ0, η0, and γ0 are the angles in the slip line field model.

[0133]

[0134] Among them, r e is the arc radius of the milling cutter edge (mm). ρ0 is the angle in the slip line field model, and μ0 is the friction coefficient of the plow cut surface, which can be obtained in a single factor experiment by the inverse identification method.

[0135] S3: Based on the instantaneous engagement angle, instantaneous cutting thickness, three-dimensional shear force coefficient and plowing force coefficient of the milling cutter teeth, the cutting force model of the milling cutter milling element in the tool coordinate system O1X1Y1Z1 is established to obtain the three-dimensional instantaneous cutting force on the milling cutter milling element.

[0136] The three-way instantaneous cutting force includes: instantaneous tangential force dF t , instantaneous radial force dF r and instantaneous axial force dF a .

[0137] like Figure 6 As shown, Figure 6 (a) is a three-dimensional schematic diagram of the cutting edge microelement. Figure 6 (b) is a plan view of the cutting edge element.

[0138] The cutting force model of the milling cutter microelement under the tool coordinate system O1X1Y1Z1 is:

[0139]

[0140] Among them, Φ j is the instantaneous engagement angle of the hth milling cutter tooth on the milling cutter, h j is the instantaneous cutting thickness of the hth milling cutter tooth on the milling cutter, Δz 1j is the axial cutting depth, K tc , K rc , K ac are the shear force coefficients corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force (N / mm 2 ), K te , K re , K ae are the plowing force coefficients (N / mm) corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force respectively.

[0141] S4: The three-dimensional instantaneous cutting force is converted to the workpiece coordinate system O0X0Y0Z0, and the integral sum is performed within the axial cutting depth range of the milling cutter cutting edge. At the same time, the three-dimensional cutting force of the milling cutter in the workpiece coordinate system O0X0Y0Z0 is obtained by combining the laser temperature threshold function.

[0142] Step S4: specifically includes:

[0143] S41: convert the three-dimensional instantaneous cutting force into the workpiece coordinate system O0X0Y0Z0;

[0144]

[0145] in, and are the micro-element cutting forces in the X, Y and Z directions in the workpiece coordinate system, respectively. λ is the micro-element motion of the tool coordinate system per unit time in the workpiece coordinate system (mm), and its size is λ = f c τ / 60.

[0146] S42: There is a competition mechanism between the thermal softening of the workpiece material and the evolution of tool wear. That is, when the temperature of the workpiece in the laser irradiation area is within the equilibrium temperature, the mechanism of material softening to reduce the cutting force is dominant; on the contrary, the mechanism of increasing the cutting force due to the evolution of tool wear causing chip adhesion is dominant; there is a power threshold range between the temperature of the workpiece in the laser irradiation area and the cutting force, and the trend of the cutting force changes when the threshold is exceeded is reversed.

[0147] The laser temperature threshold function is specifically calculated as follows:

[0148]

[0149] Among them, F hx 、F hy and F hz are the cutting force changes caused by the workpiece temperature in the laser irradiation area in the X, Y and Z directions of the workpiece coordinate system, respectively, and T is the workpiece temperature in the laser irradiation area (K), which is predicted by the finite element model. K th , K rh , K ah , K tf , K rf , K af is the cutting force coefficient related to the workpiece temperature in the laser irradiation area, which is obtained by fitting the average force coefficient method in experiments with different laser powers.

[0150] S43: Axial depth Δz at the milling cutter cutting edge 1j Integrate and sum within the range, and combine with the laser temperature threshold function to obtain the workpiece coordinate system O0X o Three-dimensional cutting forces in Y0Z0.

[0151] Specifically:

[0152]

[0153] in, and They are the cutting forces in the X, Y and Z directions in the workpiece coordinate system, respectively.

[0154] Example 2

[0155] Step 1: Use the convection heat transfer experimental device to conduct the experiment and set the heating power P of the electric heating plate. e , measure the workpiece surface temperature T under the heating state of the electric heating plate hAnd the stable surface temperature T of the workpiece after adding cutting fluid f . Calculate the contact surface area A between the cutting fluid and the workpiece, and calculate the convective heat transfer coefficient h of the cutting fluid.

[0156] Step 2: Use the laser absorption rate experimental device to conduct the experiment, set the laser power P, measure the workpiece temperature T in the non-laser irradiation area after adding the cutting fluid and the laser stable temperature T2 after adding the cutting fluid, and calculate the laser absorption rate α.

[0157] Step 3: Use Abaqus software to establish a finite element model of the workpiece and input the workpiece material parameters into the finite element model: density, constitutive model parameters, latent heat, thermal conductivity, thermal expansion and specific heat capacity.

[0158] Step 4: Based on the workpiece finite element model, the workpiece uses the convection heat transfer coefficient to establish boundary conditions, and the calculated laser absorptivity is substituted into formula (6) to apply the load; a laser temperature finite element model is established to obtain the workpiece temperature T in the laser irradiation area.

[0159] Step 5: Determine cutting parameters: spindle speed n is 2000r / min, feed rate f c The cutting depth of the milling cutter is 70 mm / min and the cutting depth of the milling cutter is Δz. 1j is 0.25mm; determine the milling cutter parameters: the milling cutter diameter d is 20mm, the number of milling cutter teeth z is 2, and the milling cutter helix angle γ is 5°; calculate the instantaneous cutting thickness and the instantaneous engagement angle of the milling cutter teeth.

[0160] Step 6: Substitute the calculated instantaneous cutting thickness and instantaneous meshing angle of the milling cutter teeth and the three-dimensional tangential force coefficient obtained by combining the workpiece temperature T in the laser irradiation area obtained in step 4 into formula (16): the instantaneous tangential force dF in the tool coordinate system O1X1Y1Z1 t , radial force dF r , axial force dF a In the equation, the three-dimensional instantaneous cutting force is obtained.

[0161] Step 7: Convert the three-dimensional instantaneous cutting force to the workpiece coordinate system O0X0Y0Z0 through formula (17);

[0162] Step 8: Combined with the workpiece temperature T in the laser irradiation area obtained in step 4, there is a competition mechanism between the thermal softening of the workpiece material and the evolution of tool wear. At the same time, the three-dimensional instantaneous cutting forces are summed up, and the cutting force of the complete milling cycle is calculated with the milling time as a variable to generate the following: Figure 7 The three-dimensional cutting force curve shown in the figure finally realizes the prediction of in-situ laser assisted heating orthogonal milling force.

[0163] The accuracy of the prediction of orthogonal milling force with in-situ laser assisted heating is determined by the presence or absence of a laser temperature threshold function.

[0164] Table 1 Error comparison with and without laser temperature threshold function

[0165] Laser power Laser temperature threshold function error (%) No laser temperature threshold function error (%) 100 5.61％ 5.52％ 150 3.13％ 3.37％ 200 6.79％ 31.97％

[0166] As shown in Table 1, after the three-dimensional cutting force is corrected by introducing the laser temperature threshold function, the prediction accuracy of the cutting force is significantly higher than that of the uncorrected cutting force prediction.

[0167] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referred to each other. Those skilled in the art can clearly understand that the technology in the embodiments of the present invention can be implemented by means of software plus a necessary general hardware platform. Based on this understanding, the technical solutions in the embodiments of the present invention are essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in the various embodiments of the present invention or certain parts of the embodiments.

[0168] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A cutting force prediction method based on in-situ laser assisted heat orthogonal milling, characterized in that: include: Based on the milling cutting parameters and the geometric parameters of the tool, the instantaneous meshing angle and the instantaneous cutting thickness of the milling cutter teeth are obtained; According to the ambient temperature and the workpiece temperature in the laser irradiation area obtained based on the laser temperature finite element model, the shear force coefficient and the plowing force coefficient in three directions are obtained; Based on the instantaneous meshing angle of the milling cutter teeth, the instantaneous cutting thickness, the three-dimensional shear force coefficient and the plowing force coefficient, the cutting force model of the milling cutter milling microelement in the tool coordinate system O1X1Y1Z1 is established to obtain the three-dimensional instantaneous cutting force on the milling cutter milling microelement; The three-dimensional instantaneous cutting force is converted to the workpiece coordinate system O0X0Y0Z0, and the integral sum is performed within the axial cutting depth range of the milling cutter cutting edge. At the same time, combined with the laser temperature threshold function, the three-dimensional cutting force exerted on the milling cutter in the workpiece coordinate system O0X0Y0Z0 is obtained.

2. The cutting force prediction method based on in-situ laser assisted heating orthogonal milling according to claim 1 is characterized in that: The instantaneous meshing angle and instantaneous cutting thickness of the milling cutter teeth are obtained based on the milling cutting parameters and the geometric parameters of the tool, wherein the milling cutting parameters include spindle speed, feed rate and axial cutting depth; the geometric parameters of the tool include: milling cutter diameter, milling cutter helix angle, milling cutter rake angle and milling cutter tip arc radius; Among them, the instantaneous meshing angle Φ of the jth milling cutter tooth on the milling cutter j for: The instantaneous cutting thickness h of the jth milling cutter tooth on the milling cutter j for: Among them, f c is the feed rate, z is the total number of milling cutter teeth, n is the milling cutter speed, Φ U1 is the micro-element angle of the first cutting bottom edge, γ is the helix angle of the milling cutter, d is the diameter of the milling cutter, Δz 1j is the axial cutting depth.

3. The cutting force prediction method based on in-situ laser assisted heating orthogonal milling according to claim 1 is characterized in that: Based on the instantaneous meshing angle of the milling cutter teeth, the instantaneous cutting thickness, the three-dimensional shear force coefficient and the plowing force coefficient, a cutting force model of the milling cutter milling microelement under the tool coordinate system O1X1Y1Z1 is established to obtain the three-dimensional instantaneous cutting force of the milling cutter milling microelement. The three-dimensional instantaneous cutting force includes: the instantaneous tangential force dF t , instantaneous radial force dF r and instantaneous axial force dF a , the three-way shear force coefficient and plough shear force coefficient include: the shear force coefficient corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force, and the plough shear force coefficient corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force; The cutting force model of the milling cutter microelement under the tool coordinate system O1X1Y1Z1 is: Among them, Φ j is the instantaneous engagement angle of the jth milling cutter tooth on the milling cutter, h j is the instantaneous cutting thickness of the jth milling cutter tooth on the milling cutter, Δz 1j is the axial cutting depth, K tc , K rc , K ac are the shear force coefficients corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force, respectively, K te , K re , K ae are the plowing force coefficients corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force respectively.

4. The cutting force prediction method based on in-situ laser assisted heating orthogonal milling according to claim 1 is characterized in that: The three-dimensional shear force coefficient and the plowing force coefficient are obtained according to the ambient temperature and the workpiece temperature of the laser irradiation area obtained based on the laser temperature finite element model, wherein the three-dimensional shear force coefficient and the plowing force coefficient include: the shear force coefficient corresponding to the instantaneous tangential force, the instantaneous radial force and the instantaneous axial force, and the plowing force coefficient corresponding to the instantaneous tangential force, the instantaneous radial force and the instantaneous axial force; Obtain the shear force coefficient corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force. The specific formula is: Obtain the plow shear force coefficient corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force. The specific formula is: Among them, K te , K re , K ae are the plow shear force coefficients corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force respectively; K tc , K rc , K ac are the shear force coefficients corresponding to the instantaneous tangential force, instantaneous radial force and instantaneous axial force, τ s is the shear flow stress, is the shear angle, i n is the local tilt angle, β a is the friction angle on the normal plane of the milling cutter microelement, α n The front angle of the milling cutter element, η c is the cutting flow angle, σ p is the normal stress of the milling cutter microelement plow section, τ p is the shear stress of the milling cutter microelement plow section, R0 is the sector radius, θ0, η0 and γ0 are the three angles in the slip line field model.

5. The cutting force prediction method based on in-situ laser assisted heating orthogonal milling according to claim 4 is characterized in that: The shear flow stress τ s for: Among them, A, B, C, n and m are the Johnson-Cook constitutive parameters of the workpiece material; ε and are the equivalent strain and the equivalent strain rate, is the reference strain rate, T m is the melting point of the workpiece material, T r is the ambient temperature, T s is the temperature of the main shear surface of the cutting edge microelement; Cutting edge microelement main shear surface temperature T s for: Wherein, T is the workpiece temperature in the laser irradiation area, τ0 is the initial pure shear yield strength, ρ is the density of the workpiece material, c is the specific heat capacity of the workpiece material; u0 is the non-uniform coefficient.

6. The cutting force prediction method based on in-situ laser assisted heating orthogonal milling according to claim 1 is characterized in that: The three-dimensional instantaneous cutting force is converted to the workpiece coordinate system O0X0Y0Z0, integrated and summed within the axial cutting depth range of the milling cutter cutting edge, and combined with the laser temperature threshold function to obtain the three-dimensional cutting force of the milling cutter in the workpiece coordinate system O0X0Y0Z0, specifically including: Convert the three-dimensional instantaneous cutting force to the workpiece coordinate system O0X0Y0Z0; in, and are the micro-element cutting forces in the X, Y and Z directions in the workpiece coordinate system, λ is the micro-element motion of the tool coordinate system per unit time in the workpiece coordinate system; dF t 、dF r and dF a are the instantaneous tangential force, instantaneous radial force and instantaneous axial force, respectively, Φ j is the instantaneous engagement angle of the jth milling tooth on the milling cutter; The laser temperature threshold function includes the cutting force variation values ​​caused by the workpiece temperature in the laser irradiation area in the X, Y and Z directions of the workpiece coordinate system, specifically: Among them, F hx 、F hy and F hz are the cutting force changes caused by the workpiece temperature in the laser irradiation area in the X, Y and Z directions of the workpiece coordinate system, T is the workpiece temperature in the laser irradiation area, K th , K rh , K ah , K tf , K rf and K af are the six cutting force coefficients related to the workpiece temperature in the laser irradiation area, which are obtained by fitting the average force coefficient in the tests with different laser powers; The three-dimensional cutting force on the milling cutter in the workpiece coordinate system O0X0Y0Z0 includes the cutting forces in the X, Y and Z directions in the workpiece coordinate system, specifically: in, and are the cutting forces in the X, Y and Z directions in the workpiece coordinate system; z is the total number of milling cutter teeth, Δz 1j is the axial cutting depth.

7. The cutting force prediction method based on in-situ laser assisted heating orthogonal milling according to claim 1 is characterized in that: The three-dimensional shear force coefficient and the plowing force coefficient are obtained according to the ambient temperature and the workpiece temperature in the laser irradiation area obtained based on the laser temperature finite element model, including constructing the laser temperature finite element model. The specific process is as follows: The convective heat transfer coefficient of the cutting fluid and the laser absorption rate after adding the cutting fluid are obtained by experimental method; Establish a workpiece finite element model based on workpiece size and material parameters; Based on the workpiece finite element model, the boundary conditions of convective heat transfer are obtained through the convective heat transfer coefficient, and the laser heat source load is applied on the workpiece surface in combination with the laser absorptivity to establish the laser temperature finite element model.

8. The cutting force prediction method based on in-situ laser assisted heating orthogonal milling according to claim 7, characterized in that: Based on the workpiece finite element model, the boundary conditions of convective heat transfer are obtained through the convective heat transfer coefficient, and the laser heat source load is applied on the workpiece surface in combination with the laser absorptivity to establish a laser temperature finite element model, which specifically includes: Define the laser heat source. The equation of the laser heat source is: Where q(x,y) is the power density of the laser, α is the laser absorptivity, P is the laser power, r0 is the radius of the laser irradiation area, (x,y) is the coordinate of the center of the laser irradiation area on the workpiece surface, τ is the unit time, ω is the laser pulse width, T ω is the laser light emission period; Establish the heat conduction equation; Obtain boundary conditions for convective heat transfer; Where ρ is the density of the workpiece material, C is the specific heat capacity of the workpiece material, k is the thermal conductivity of the material, and ε n is the emissivity of the workpiece material, σ is the Stefan-Boltzmann constant, is the heat generated per unit volume of the laser irradiation area, T is the workpiece temperature in the laser irradiation area, T0 is the initial temperature of the workpiece, x, y, z are the coordinates of the center of the laser irradiation area in three-dimensional space, and h is the convective heat transfer coefficient. A laser temperature finite element model was established by using Abaqus software.

9. The cutting force prediction method based on in-situ laser assisted heating orthogonal milling according to claim 7, characterized in that: In the process of establishing the workpiece finite element model according to the workpiece size and material parameters, the material parameters include density, constitutive model parameters, latent heat, thermal conductivity, thermal expansion and specific heat capacity.

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