Calculation method for equivalent elastic modulus of medium-containing bonding surface of composite material machine tool

Abstract

The invention is applicable to the technical field of calculation of equivalent elastic modulus of machine tool joint surfaces, and provides a method for calculating equivalent elastic modulus of a medium-containing joint surface of a composite machine tool, which comprises the following steps of: calculating solid contact rigidity between the joint surfaces by adopting a fractal contact theory and considering a microstructure of surface roughness; an elastic modulus temperature coefficient concept is introduced to quantify the relationship of the elastic modulus of the material along with the temperature change; analyzing the influence of different media on the equivalent stiffness of the junction surface; constructing an equivalent elastic modulus calculation model of the joint surface, analyzing the relationship between solid and medium contact stiffness, and calculating the equivalent elastic modulus of the medium-containing joint surface; and quantitatively analyzing the influence of the types of media between the junction surfaces, the preload conditions of the junction surfaces and the temperature change on the elastic modulus of the junction surfaces through a virtual material method. According to the method, the defects in the prior art are overcome, a more accurate theoretical basis is provided for machine tool design and performance optimization, optimization of the machine tool design is facilitated, and the performance and reliability of the machine tool in variable working environments are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of equivalent elastic modulus calculation of machine tool joint surfaces, and in particular relates to a method for calculating the equivalent elastic modulus of a medium-containing joint surface of a composite material machine tool. Background Art

[0002] The introduction of composite materials has significantly improved the thermal performance and static and dynamic response capabilities of machine tools, showing broad application prospects in the field of machine tool manufacturing. Machine tools are assembled from many precision parts, and 60% to 80% of their structural stiffness and about 90% of their damping characteristics are derived from the joints between these parts. During the operation of the machine tool, the intervention of media such as lubricating oil fills the tiny gaps on the joint surface, which has a significant impact on the physical properties of the joint surface, and then indirectly affects the overall performance of the machine tool. The elastic modulus of the joint surface of the machine tool is a key indicator to measure its ability to resist deformation under force, and plays a decisive role in the accuracy, stability and durability of the machine tool. A high elastic modulus means that the deformation of the joint surface is small under load, which is crucial to maintaining the precise positioning and processing accuracy of the machine tool. At the same time, it also determines the resistance of the joint surface to cutting force and thermal deformation, which plays an important role in maintaining the stability of the processing process and extending the service life of the machine tool.

[0003] However, in the current field of technical research, the analysis of the performance of machine tool joint surfaces is often limited to machine tool structures made of a single material. For example, the Chinese patent "Method and device for measuring contact thermal resistance of bolt joints based on effective contact area" with publication number CN117290979B uses metal materials with the same thermal conductivity on both sides of the joint surface in its thermal resistance measurement method. In contrast, the joint surface of composite machine tools uses different materials on both sides of the joint surface to achieve an optimized combination of performance. In addition, the prior art often relies on simplified mechanical models when performing numerical calculations of the mechanical properties of mechanical joint surfaces, such as the Chinese patent "Method for testing the stiffness of the joint surface of the top of a cylindrical grinder" with publication number CN113916473A. This type of model fails to comprehensively consider the complex effects of medium diversity and composite thermal loads on the performance of the joint surface. The limitations of this simplified processing lead to deviations in the existing models when predicting performance under actual working conditions, and cannot provide sufficient scientific basis for the precise optimization of machine tool design.

[0004] In view of this, the present invention proposes a method for calculating the equivalent elastic modulus of the medium-containing bonding surface of a composite material machine tool, aiming to make up for the shortcomings of the existing technology and provide more accurate theoretical support for machine tool design and performance optimization. Summary of the invention

[0005] The purpose of the present invention is to provide a method for calculating the equivalent elastic modulus of a composite material machine tool containing a medium interface, aiming to solve the problems raised in the above background technology.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for calculating the equivalent elastic modulus of a composite material machine tool containing a medium interface comprises the following steps:

[0008] Step 1: Using fractal contact theory, considering the microstructure of surface roughness, analyzing the deformation of the micro-convex body of the bonding surface after being subjected to force, and calculating the solid contact stiffness between the bonding surfaces;

[0009] Step 2: Introduce the concept of temperature coefficient of elastic modulus to quantify the relationship between the elastic modulus of the material and the temperature, and calculate the solid contact stiffness between the bonding surfaces considering the temperature change;

[0010] Step 3: Analyze the influence of different media on the equivalent stiffness of the bonding surface, consider the physical properties of the media, and calculate the contact stiffness of the bonding surface of the corresponding media components;

[0011] Step 4: Based on the physical performance characterization parameters, a calculation model for the equivalent elastic modulus of the bonding surface is constructed, and the relationship between the solid and medium contact stiffness is analyzed to calculate the equivalent elastic modulus of the bonding surface containing the medium;

[0012] Step 5: Build a bonding surface elastic modulus model through the virtual material method, quantitatively analyze the effects of bonding surface medium type, bonding surface preload conditions and temperature changes on the bonding surface elastic modulus, and use the equivalent elastic modulus of the virtual material layer to simulate the mechanical properties of the actual material.

[0013] Furthermore, the two sides of the composite material machine tool joint surface are made of different materials to contact each other; the medium component between the joint surfaces is oil or air.

[0014] Furthermore, in step 1, the calculation formula of the solid contact stiffness between the combined surfaces is specifically:

[0015]

[0016] Where: E S is the solid equivalent elastic modulus between the bonding surfaces, Where v1 and v2 represent the Poisson's ratio of the materials on both sides of the composite machine tool joint surface, E1 and E2 represent the elastic modulus of the materials on both sides of the composite machine tool joint surface; A is the nominal contact area of ​​the joint surface; is the dimensionless contact stiffness of the solid between the bonding surfaces; D is the fractal dimension of the rougher material surface of the bonding surface; Rs is the actual solid contact area between the bonding surfaces; is the dimensionless nominal contact area of ​​the asperities between the bonding surfaces; H v G is the hardness of the softer material on the bonding surface; *is the dimensioned characteristic scale parameter of the rougher material surface of the bonding surface, G is the characteristic scale parameter of the rough surface of the rougher material on the bonding surface.

[0017] Furthermore, in step 2, when the temperature rises, the elastic modulus of the material changes, which is calculated by the following formula:

[0018] Formula 2: ΔE=E0×α E ×ΔT

[0019] Where: ΔE is the change in the elastic modulus of the material in the temperature coefficient of elastic modulus; E0 is the initial elastic modulus of the material in the temperature coefficient of elastic modulus; α E is the temperature coefficient of elastic modulus; ΔT is the temperature change in the temperature coefficient of elastic modulus;

[0020] According to the temperature coefficient of elastic modulus of solid material between the joint surfaces, the calculation formula of the equivalent elastic modulus of solid between the joint surfaces affected by temperature change is:

[0021] Formula 3:

[0022] Combining equations 1 and 3, we establish a calculation formula for the solid contact stiffness between the joint surfaces taking into account temperature changes, specifically: Equation 4:

[0023] Furthermore, in step 3, when the medium between the bonding surfaces is air, the influence of the air medium stiffness on the overall stiffness is ignored, and the equivalent contact stiffness of the air medium bonding surface is actually the stiffness provided by the solid material contact between the bonding surfaces, that is, K S :

[0024] Formula 5: K = K S +K air =K S ;

[0025] The calculation formula of the equivalent elastic modulus of the oil medium between the joint surfaces is as follows:

[0026] Formula 6:

[0027] Where: E oil V is the equivalent elastic modulus of the oil medium between the bonding surfaces; oil is the volume of the oil medium between the joint surfaces; ΔP oil is the pressure acting on the oil medium between the joint surfaces; ΔV oil ΔF is the volume change of the oil medium between the joint surfaces after being compressed; oil Normal support force provided by the oil medium between the joint surfaces; A oil is the actual contact area of ​​the oil medium between the joint surfaces; Δδoil K is the thickness change of the oil layer between the joint surfaces after the oil medium is compressed; oil It is the contact stiffness provided by the oil medium in the oil-liquid medium joint surface; H is the equivalent thickness of the joint surface;

[0028] Considering the influence of leakage coefficient, the contact stiffness provided by the corrected oil medium is:

[0029] Formula 7:

[0030] Where: γ is the leakage coefficient;

[0031] Combining equations 2 and 7, the contact stiffness provided by the oil medium after optimizing the elastic modulus temperature coefficient is established, which is:

[0032] Formula 8:

[0033] Furthermore, in step 4, the calculation formula for the equivalent elastic modulus of the bonding surface is specifically:

[0034] Formula 9:

[0035] Where: E is the equivalent elastic modulus of the bonding surface; H is the equivalent thickness of the bonding surface; σ is the normal stress on the bonding surface; ε is the normal strain of the bonding surface; F n is the load applied to the joint surface; Δδ is the deformation of the joint surface when it is compressed; K is the equivalent stiffness of the joint surface; F n is the total load; A is the nominal contact area of ​​the bonding surface.

[0036] Furthermore, in step 4, the equivalent contact stiffness calculation formula of the composite material machine tool joint surface containing a dielectric component is:

[0037] Formula 10: K = K S +K med ;

[0038] Combining equation 9, equation 5 and equation 4, we can get the equivalent elastic modulus calculation formula of the composite material machine tool joint surface when the medium component is air medium:

[0039] Formula 11:

[0040] Combining equations 10, 9, 8 and 4, we can get the equivalent elastic modulus calculation formula of the composite material machine tool joint surface when the medium component is oil medium:

[0041] Formula 12:

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The calculation method of the equivalent elastic modulus of the medium-containing bonding surface of the composite machine tool aims to provide a more accurate and comprehensive numerical calculation scheme for the performance evaluation of the machine tool bonding surface by comprehensively considering the actual working conditions such as the medium intervention between the bonding surfaces and the temperature rise of the bonding surfaces. This method not only makes up for the shortcomings of the existing technology, but also provides a more accurate theoretical basis for machine tool design and performance optimization, which helps to optimize the design of machine tools and improve their performance and reliability in a changing working environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a microscopic diagram of the deformation of a micro-convex body.

[0045] Figure 2 Schematic diagram of parallel stiffness of the joint surface.

[0046] Figure 3 Schematic diagram of virtual material of the bonding surface.

[0047] Figure 4 This is the equivalent elastic modulus-preload diagram of the bonding surface.

[0048] Figure 5 This is the equivalent elastic modulus-temperature diagram of the bonding surface.

[0049] Figure 6 The figure is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0050] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0051] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0052] One embodiment of the present invention provides a method for calculating the equivalent elastic modulus of a composite material machine tool containing a medium interface, and its flow chart is as follows: Figure 1 As shown, the method comprises the following steps:

[0053] Step 1: Using fractal contact theory, considering the microstructure of surface roughness, analyzing the deformation of the micro-convex body of the bonding surface after being subjected to force, and calculating the solid contact stiffness between the bonding surfaces;

[0054] The specific process of step 1 is as follows: the actual bonding surface is usually composed of two rough surfaces. For the convenience of analysis, the bonding surface model can be transformed into a contact problem between a rough surface and an ideal plane. Each convex body on the rough surface can be approximated as a spherical object with an equivalent curvature radius R. In the absence of external force, the contact state between the spherical convex body and the plane can be simplified to point contact, such as Figure 1 However, when a normal load p is applied, the spherical micro-convex body will produce a normal deformation δ and maintain contact with the plane. At this time, the radius of the contact area becomes r, as shown in Figure 1 As shown in (b).

[0055] Then the following relationship holds:

[0056] Formula 1:

[0057] Formula 2:

[0058] Where: p is the normal load applied to the asperity, N; E S is the solid equivalent elastic modulus between the bonding surfaces, GPa, where v1 and v2 represent the Poisson's ratio of the materials on both sides of the composite machine tool joint surface; E1 and E2 represent the elastic modulus of the materials on both sides of the steel composite machine tool joint surface, GPa. R is the equivalent radius of curvature of the micro-convex body, m; δ is the contact deformation of the micro-convex body under load, m; r is the radius of the contact area between the micro-convex body and the smooth surface after deformation, m.

[0059] According to equations 1 and 2, the normal contact stiffness K provided by a single micro-convex body in contact with a smooth surface is n for:

[0060] Formula 3: K n =2E n ·r;

[0061] Where: E n Elastic modulus provided for a single asperity, GPa.

[0062] The contact area a of the asperity contact region can be expressed as:

[0063] Formula 4: a = πr 2 ;

[0064] So it can be deduced that:

[0065] Formula 5:

[0066] Since the surface morphology of the material after processing is isotropic and similar in all directions, it can be considered that each micro-asperity interacts with other surfaces independently during the contact process. Therefore, it is assumed here that there is no interaction between micro-asperities.

[0067] Therefore, the calculation formula of the solid contact stiffness of the composite machine tool joint surface is:

[0068] Formula 6:

[0069] Where: a l 、a c Respectively represent the maximum contact area and nominal contact area of ​​the micro-convex body between the bonding surfaces, mm 2 ; n(a) is the distribution density function of the contact points of the micro-convex body, Where D is the fractal dimension of the rougher material surface of the bonding surface, and a is the average contact area of ​​the micro-convex bodies between the bonding surfaces.

[0070] Substituting equation 5 into equation 6, we get:

[0071] Formula 7:

[0072] After the equation 7 is arranged and dimensionless, the dimensionless normal contact stiffness of the solid between the bonding surfaces is obtained: for:

[0073] Formula 8:

[0074] Where: is the dimensionless contact stiffness of the solid between the bonding surfaces; Rs is the actual solid contact area between the bonding surfaces, m 2 ; is the dimensionless nominal contact area of ​​the asperities between the mating surfaces, Among them, H v is the hardness of the softer material on the bonding surface, GPa; G * is the dimensioned characteristic scale parameter of the rougher material surface of the bonding surface, Where G is the characteristic scale parameter of the rough surface of the rougher material on the bonding surface; A is the nominal contact area of ​​the bonding surface, m 2 .

[0075] Therefore, the calculation formula of the solid contact stiffness between the bonding surfaces is as follows:

[0076] Formula 9:

[0077] Step 2: Introduce the concept of the effect of temperature change on the elastic modulus of the material, quantify this relationship through the temperature coefficient of the elastic modulus, and derive the calculation formula of the solid stiffness of the bonding surface considering the temperature change;

[0078] The specific process of step 2 is: considering that increasing the temperature usually leads to an increase in the vibration amplitude of atoms inside the engineering material, resulting in a decrease in the rigidity of the material and a decrease in the elastic modulus, in order to accurately analyze the thermal properties of the bonding surface and quantify the relationship between the elastic modulus of the material and the temperature, the concept of temperature coefficient of elastic modulus is introduced, which is a physical quantity used to describe the change of the elastic modulus of the material with temperature.

[0079] When the temperature rises, the elastic modulus of the material changes and can be calculated by the following formula:

[0080] Formula 10: ΔE=E0×α E ×ΔT;

[0081] Where: ΔE is the change in the elastic modulus of the material in the temperature coefficient of elastic modulus, GPa; E0 is the initial elastic modulus of the material in the temperature coefficient of elastic modulus, GPa; α E is the temperature coefficient of elastic modulus, K -1 ; ΔT is the temperature change in the temperature coefficient of elastic modulus, °C. In practical applications, the temperature coefficient of elastic modulus can be determined by experimental methods. In this invention, 10 -5 K -1 .

[0082] According to the temperature coefficient of elastic modulus of solid material between the joint surfaces, the calculation formula of the solid equivalent elastic modulus between the joint surfaces affected by temperature change is rewritten as:

[0083] Formula 11:

[0084] Where: is the solid equivalent elastic modulus between the bonding surfaces affected by temperature changes, GPa.

[0085] Combining equations 9 and 11, we establish a formula for calculating the solid contact stiffness between the joint surfaces taking temperature changes into account. Specifically, it is: Equation 12:

[0086] Step 3: Analyze the influence of different media (such as air, oil, etc.) on the equivalent stiffness of the joint surface, consider the physical properties of the medium, such as elastic modulus and leakage coefficient, and calculate the contact stiffness of the joint surface of the corresponding medium component;

[0087] The specific process of step 3 is:

[0088] S1. When the medium between the joint surfaces is air, the air medium is considered as a mixed gas. Since the elastic modulus (bulk modulus) of air is significantly lower than that of solid materials, its contribution in the calculation of the equivalent stiffness of the joint surface can usually be ignored. During the operation of the machine tool, since the joint surface is not completely sealed, the air medium will leak. In this case, when the air medium is compressed, its volume will decrease, resulting in an increase in pressure, causing the air medium to leak through the tiny gaps in the joint surface.

[0089] Considering these characteristics of the air medium, the present invention ignores the influence of the air medium stiffness on the overall stiffness in the calculation. This neglect is based on the following assumption: the leakage of the air medium will quickly reduce its pressure in the joint surface, thereby reducing its contribution to the structural stiffness. Even when there is air medium on the joint surface, due to the characteristics of low elastic modulus, the deformation of the air medium when bearing load is much greater than that of the solid material, so its contribution to the overall stiffness is relatively small.

[0090] Therefore, when the medium between the joint surfaces is air, the equivalent contact stiffness of the joint surface containing the air medium is actually the stiffness provided by the solid material contact between the joint surfaces. Therefore:

[0091] Formula 13: K = K S +K air =K S ;

[0092] Where: K is the equivalent contact stiffness of the interface containing air medium, K S is the solid contact stiffness between the bonding surfaces, K air The contact stiffness provided by the air medium.

[0093] S2. When the medium between the joint surfaces is oil, the calculation formula of the equivalent elastic modulus of the oil medium between the joint surfaces is obtained by defining the bulk modulus of the liquid, specifically:

[0094] Formula 14:

[0095] Where: E oil is the equivalent elastic modulus of the oil medium between the joint surfaces, GPa; V oil is the volume of the oil medium between the joint surfaces, m 3 ; ΔP oil is the pressure of the oil medium acting on the joint surface, N; ΔV oil is the volume change of the oil medium between the joint surfaces after being compressed, m 3 ; ΔF oil Normal support force provided by the oil medium between the joint surfaces, N; A oil is the actual contact area of ​​the oil medium between the joint surfaces, m2; Δδ oil K is the thickness change of the oil layer between the joint surfaces after the oil medium is compressed, m; oil It is the contact stiffness provided by the oil medium in the oil-liquid medium joint surface; H is the equivalent thickness of the joint surface, m.

[0096] Therefore, the contact stiffness provided by the oil medium in the oil-medium joint surface is:

[0097] Formula 15:

[0098] In actual situations, the lubricating oil between the mating surfaces is not completely sealed. After the mating surfaces are subjected to normal loads, the oil medium will leak to a certain extent. Therefore, considering the influence of the leakage coefficient, the contact stiffness provided by the corrected oil medium is:

[0099] Formula 16:

[0100] Where: γ is the leakage coefficient, which is related to the roughness and geometry of the joint surface. For cast iron and alloy steel materials, the value can be 0.421;

[0101] Combining equations 10 and 16, the contact stiffness provided by the oil medium after considering the optimization of the elastic modulus temperature coefficient is established, which is:

[0102] Formula 17:

[0103] Step 4: Based on the physical performance characterization parameters, a calculation model for the equivalent elastic modulus of the bonding surface is constructed, and the relationship between the solid and medium contact stiffness is analyzed to calculate the equivalent elastic modulus of the bonding surface containing the medium;

[0104] The specific process of step 4 is as follows: The elastic modulus of an object is defined as the ratio between the normal strain ε and the stress generated when the structure is subjected to a normal stress σ. Normal stress refers to the normal load acting on a unit area, which can be calculated by dividing the total applied load F by n It is calculated by dividing by the nominal contact area A of the bonding surface; the normal strain is the ratio between the deformation Δδ of the bonding surface when it is compressed and the equivalent thickness H of the bonding surface, which is related to the equivalent stiffness K of the force borne by the bonding surface under unit deformation. Therefore, the equivalent elastic modulus of the bonding surface can be calculated by the following formula:

[0105] Formula 18:

[0106] Where: E is the equivalent elastic modulus of the bonding surface, GPa; H is the equivalent thickness of the bonding surface, m; σ is the normal stress on the bonding surface, GPa; ε is the normal strain of the bonding surface, which is the ratio of the deformation of the bonding surface when it is compressed to the original size; F n is the load applied to the joint surface, N; Δδ is the deformation of the joint surface when it is compressed, m; K is the equivalent stiffness of the joint surface, N / m; F n is the total load; A is the nominal contact area of ​​the joint surface, m 2 .

[0107] like Figure 2 As shown in the figure, the equivalent stiffness of the joint surface of the composite material machine tool containing dielectric components is provided by two main components: one is the solid contact stiffness K in the direct contact area between the materials on both sides of the joint surface. S, and the second is the medium stiffness K of the medium between the surfaces (such as oil, air or other types of media) med The two parts are mechanically in parallel, that is, they contribute independently to the overall stiffness.

[0108] Therefore, the calculation formula for the equivalent contact stiffness of the composite material machine tool joint surface containing medium components is:

[0109] Formula 19: K = K S +K med ;

[0110] Combining equations 18, 13, and 12, we can get the equivalent elastic modulus calculation formula of the composite material machine tool joint surface when the medium component is air medium:

[0111] Formula 20:

[0112] Combining equations 19, 18, 17 and 12, we can get the equivalent elastic modulus calculation formula of the composite material machine tool joint surface when the medium component is oil medium:

[0113] Formula 21:

[0114] Step 5: Build a bonding surface elastic modulus model through the virtual material method, quantitatively analyze the effects of bonding surface medium type, bonding surface preload conditions and temperature changes on the bonding surface elastic modulus, and use the equivalent elastic modulus of the virtual material layer to simulate the mechanical properties of the actual material.

[0115] The specific process of step 5 is: considering the complexity of the machine tool working process, in order to accurately calculate the equivalent elastic modulus of the bonding surface, the present invention proposes a method for calculating the equivalent elastic modulus of the bonding surface of a composite material machine tool containing a dielectric component based on a virtual material method.

[0116] First, the joint surface is assumed to be a uniform layer of virtual material, and the nominal contact area of ​​the virtual material layer is set to 0.225m 2 , the equivalent elastic modulus of the virtual material layer is used to simulate the mechanical properties of the actual material of the bonding surface, such as Figure 3 As shown. The thickness of the virtual material layer is determined by the micro-convex bodies on both sides of the bonding surface and the thickness of the deformation area of ​​the material. Taking the fiber resin concrete mineral composite machine tool bonding surface as an example, the materials on both sides of the bonding surface are 45 steel and composite materials respectively. The composite material is cast, and its roughness after machining usually fluctuates around Ra 6.3. The maximum peak of the micro-convex body is around 500μm. Assuming that the deformation area of ​​the composite material when in contact is 500μm, we set the equivalent thickness of the composite material, that is, h A=1mm; the roughness of the steel surface after machining that matches the composite material is usually Ra 3.2, which is about half of the composite material. The equivalent thickness of the steel is 0.5mm, that is, h B =0.5mm. Therefore, the equivalent thickness of the virtual material layer is the sum of the thickness of the steel material and the composite material, H = h A +h B =1.5mm.

[0117] Next, using the calculation process mentioned in steps 1-4, the equivalent elastic modulus of the composite material interface under the conditions of oil medium and air medium was calculated respectively. The material performance parameters involved in the calculation are shown in Table 1. Compared with 45 steel, the composite material has greater roughness and is softer. Therefore, in the calculation process, only the fractal dimension, surface characteristic scale parameter and hardness of the composite material need to be determined. The calculation results are shown in Table 2. Based on the calculation results, the elastic modulus-preload diagram of the composite material machine tool interface containing medium components is drawn, as shown in Table 2. Figure 4 As shown in the figure, it can be seen that the equivalent elastic modulus of the bonding surface is proportional to the size of the preload of the bonding surface. After analysis, it can be seen that the elastic modulus and density of the solid material are larger than those of the medium. A larger bonding surface preload will lead to more solid material contact between the bonding surfaces, and the elastic modulus of the oil medium is much smaller than that of the solid material. Therefore, the equivalent elastic modulus of the oil medium bonding surface is basically equal to the equivalent elastic modulus of the air medium bonding surface.

[0118] Table 1 Material performance parameters involved in the calculation

[0119]

[0120] Table 2 Calculation results of equivalent elastic modulus of the bonding surface

[0121]

[0122] In addition, we explored the influence of temperature change and medium type on the elastic modulus of the virtual material of the bonding surface when the roughness of the composite specimen is Ra6.3μm and the preload of the bonding surface is 0.6MPa. Figure 5As shown in the figure, it can be seen that the equivalent elastic modulus of the bonding surface decreases with the increase of temperature. This is because increasing the temperature usually leads to an increase in the vibration amplitude of the atoms inside the engineering material, which in turn causes an increase in the average distance between atoms and a weakening of the interaction force, which ultimately leads to a decrease in the rigidity of the material and a decrease in the elastic modulus. At the same time, it can be found that the rate of change of the elastic modulus of the bonding surface of the oil medium with temperature is greater than the rate of change of the elastic modulus of the bonding surface of the air medium with temperature. This is because the elastic modulus of the bonding surface of the air medium is approximately equal to the elastic modulus of the solid material between the bonding surfaces, while the elastic modulus of the bonding surface of the oil medium is the sum of the elastic moduli of the solid material between the bonding surfaces and the oil medium.

[0123] In summary, the elastic modulus model of the bonding surface constructed by the virtual material method provides us with an effective method to quantitatively analyze the influence of the type of medium between the bonding surfaces, the preload conditions of the bonding surfaces and the temperature changes on the elastic modulus of the bonding surfaces.

[0124] The above are only preferred embodiments of the present invention. It should be pointed out that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. These should also be regarded as the protection scope of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A method for calculating the equivalent elastic modulus of a composite material machine tool containing a medium interface, characterized in that: The following steps are involved: Step 1: Using fractal contact theory, considering the microstructure of surface roughness, analyzing the deformation of the micro-convex body of the bonding surface after being subjected to force, and calculating the solid contact stiffness between the bonding surfaces; Step 2: Introduce the concept of temperature coefficient of elastic modulus to quantify the relationship between the elastic modulus of the material and the temperature, and calculate the solid contact stiffness between the bonding surfaces considering the temperature change; Step 3: Analyze the influence of different media on the equivalent stiffness of the bonding surface, consider the physical properties of the media, and calculate the contact stiffness of the bonding surface of the corresponding media components; Step 4: Based on the physical performance characterization parameters, a calculation model for the equivalent elastic modulus of the bonding surface is constructed, and the relationship between the solid and medium contact stiffness is analyzed to calculate the equivalent elastic modulus of the bonding surface containing the medium; Step 5: Build a bonding surface elastic modulus model through the virtual material method, quantitatively analyze the influence of the type of medium between the bonding surfaces, the bonding surface preload conditions and temperature changes on the bonding surface elastic modulus, and use the equivalent elastic modulus of the virtual material layer to simulate the mechanical properties of the actual material.

2. The method for calculating the equivalent elastic modulus of the medium-containing interface of a composite material machine tool according to claim 1, characterized in that: The two sides of the composite material machine tool joint surface are made of different materials to contact each other; the medium component between the joint surfaces is oil or air.

3. The method for calculating the equivalent elastic modulus of the medium-containing interface of a composite material machine tool according to claim 1, characterized in that: In step 1, the calculation formula of the solid contact stiffness between the bonding surfaces is specifically: Formula 1: Where: E S is the solid equivalent elastic modulus between the bonding surfaces, Where v1 and v2 represent the Poisson's ratio of the materials on both sides of the composite machine tool joint surface, E1 and E2 represent the elastic modulus of the materials on both sides of the composite machine tool joint surface; A is the nominal contact area of ​​the joint surface; is the dimensionless contact stiffness of the solid between the bonding surfaces; D is the fractal dimension of the rougher material surface of the bonding surface; Rs is the actual solid contact area between the bonding surfaces; is the dimensionless nominal contact area of ​​the asperities between the bonding surfaces; H v G is the hardness of the softer material on the bonding surface; * is the dimensioned characteristic scale parameter of the rougher material surface of the bonding surface, G is the characteristic scale parameter of the rough surface of the rougher material on the bonding surface.

4. The method for calculating the equivalent elastic modulus of the medium-containing interface of a composite material machine tool according to claim 3, characterized in that: In step 2, when the temperature rises, the elastic modulus of the material changes, which is calculated by the following formula: Formula 2: ΔE=E0×α E ×ΔT Where: ΔE is the change in the elastic modulus of the material in the temperature coefficient of elastic modulus; E0 is the initial elastic modulus of the material in the temperature coefficient of elastic modulus; α E is the temperature coefficient of elastic modulus; ΔT is the temperature change in the temperature coefficient of elastic modulus; According to the temperature coefficient of elastic modulus of solid material between the joint surfaces, the calculation formula of the equivalent elastic modulus of solid between the joint surfaces affected by temperature change is: Formula 3: Combining equations 1 and 3, we establish a calculation formula for the solid contact stiffness between the joint surfaces taking into account temperature changes, specifically: Formula 4:

5. The method for calculating the equivalent elastic modulus of the medium-containing interface of a composite material machine tool according to claim 4, characterized in that: In step 3, when the medium between the bonding surfaces is air, the influence of the air medium stiffness on the overall stiffness is ignored. The equivalent contact stiffness of the air medium bonding surface is actually the stiffness provided by the solid material contact between the bonding surfaces, that is, K S : Formula 5: K = K S +K air =K S ; The calculation formula of the equivalent elastic modulus of the oil medium between the joint surfaces is as follows: Formula 6: Where: E oil V is the equivalent elastic modulus of the oil medium between the joint surfaces; oil is the volume of the oil medium between the joint surfaces; ΔP oil is the pressure acting on the oil medium between the joint surfaces; ΔV oil ΔF is the volume change of the oil medium between the joint surfaces after being compressed; oil Normal support force provided by the oil medium between the joint surfaces; A oil is the actual contact area of ​​the oil medium between the joint surfaces; Δδ oil K is the thickness change of the oil layer between the joint surfaces after the oil medium is compressed; oil It is the contact stiffness provided by the oil medium in the oil-liquid medium joint surface; H is the equivalent thickness of the joint surface; Considering the influence of leakage coefficient, the contact stiffness provided by the corrected oil medium is: Formula 7: Where: γ is the leakage coefficient; Combining equations 2 and 7, the contact stiffness provided by the oil medium after optimizing the elastic modulus temperature coefficient is established, which is: Formula 8:

6. The method for calculating the equivalent elastic modulus of the medium-containing interface of a composite material machine tool according to claim 5, characterized in that: In step 4, the calculation formula of the equivalent elastic modulus of the bonding surface is specifically: Formula 9: Where: E is the equivalent elastic modulus of the bonding surface; H is the equivalent thickness of the bonding surface; σ is the normal stress on the bonding surface; ε is the normal strain of the bonding surface; F n is the load applied to the joint surface; Δδ is the deformation of the joint surface when it is compressed; K is the equivalent stiffness of the joint surface; F n is the total load; A is the nominal contact area of ​​the bonding surface.

7. The method for calculating the equivalent elastic modulus of the medium-containing interface of a composite material machine tool according to claim 6, characterized in that: In step 4, the equivalent contact stiffness calculation formula of the composite material machine tool joint surface containing a dielectric component is: Formula 10: K = K S +K med ; Combining equation 9, equation 5 and equation 4, we can get the equivalent elastic modulus calculation formula of the composite material machine tool joint surface when the medium component is air medium: Formula 11: Combining equations 10, 9, 8 and 4, we can get the equivalent elastic modulus calculation formula of the composite material machine tool joint surface when the medium component is oil medium: Formula 12:

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