Method for calculating actual contact area ratio of oil medium joint surface of gantry machine tool

Abstract

The invention is suitable for the technical field of gantry machine tools, and provides a gantry machine tool oil medium joint surface actual contact area ratio calculation method comprising the following steps: obtaining an actual contact specific gravity rubbing of a joint surface, and carrying out discretization processing; mATLAB software is used for storing a gray value matrix and carrying out reverse processing; then decomposing into an inner contact matrix and an outer contact matrix; deducing the solid discrete contact area of the junction surface considering the contact weight; performing primary and secondary correction on the area of the external contact unit to obtain a solid discrete contact area ratio of the oil medium junction surface of the gantry machine tool; deducing a solid discrete contact area ratio and an oil medium discrete contact area ratio of the junction surface without considering the contact weight; in combination with MTALAB software, the calculation process is input, and the actual contact area ratio of the gantry machine tool oil medium combination surfaces is output. The method is not only suitable for a gantry machine tool under an oil medium, but also can be popularized to calculation and research of the actual contact area ratio of other types of mechanical joint surfaces.

Description

Technical Field

[0001] The invention belongs to the technical field of gantry machine tools, and in particular relates to a method for calculating the actual contact area ratio of an oil-liquid medium combination surface of a gantry machine tool. Background Art

[0002] Gantry machine tools are assembled from many parts through various combinations. During their operation, there are a large number of joint surface contacts. Studies have shown that 60%-80% of the stiffness of gantry machine tools and about 90% of the damping are derived from the joint surface. The actual contact area of ​​the joint surface is an important factor affecting the performance of the joint surface. However, in the actual contact model, the contact surface is often an irregular surface with a certain degree of roughness, resulting in the contact of the joint surface of the gantry machine tool being actually the contact of two discrete micro-convex bodies, which makes the actual contact area of ​​the joint surface often smaller than the nominal contact area of ​​the joint surface. At the same time, when the gantry machine tool is working normally, the lubricating oil medium component will intervene in the gap of the joint surface to form a gantry machine tool joint surface containing oil medium. The intervention of the medium component will significantly affect the performance of the joint surface, and then affect the overall performance of the gantry machine tool.

[0003] In the prior art, the calculation of the actual contact area of ​​mechanical joint surfaces usually relies on fractal contact theory, and studies are conducted on the elastic-plastic change process of a single micro-convex body between the joint surfaces. However, the calculation process mostly uses empirical parameters to determine the contact conditions between the joint surfaces, and the calculation process is cumbersome, such as the Chinese patent "A method for calculating the contact area of ​​a three-dimensional rough surface" disclosed as CN115033941A. In addition, most of the research conducted on machine tool joint surfaces ignores the presence of a medium between the machine tool joint surfaces, such as the Chinese patent "Method and device for measuring contact thermal resistance of bolt joints based on effective contact area" disclosed as CN117290979B, which is difficult to provide an effective reference for the optimal design of machine tools working under lubrication conditions. In view of the above problems, the present invention proposes a method for calculating the actual contact area ratio of the oil-medium joint surface of a gantry machine tool. Summary of the invention

[0004] The purpose of the present invention is to provide a method for calculating the actual contact area ratio of the oil-medium interface of a gantry machine tool, aiming to solve the problems raised in the above-mentioned background technology.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for calculating the actual contact area ratio of the oil-liquid medium interface of a gantry machine tool comprises the following steps:

[0007] Step 1, obtaining the actual contact density rubbing of the bonding surface, discretizing it and dividing it into inner contact units and outer contact units;

[0008] Step 2, input the discretized imprint image into MATLAB software, save it as a gray value matrix and perform inverse processing;

[0009] Step 3, decomposing the inverse processing gray value matrix into an internal contact matrix and an external contact matrix according to the divided internal contact units and external contact units;

[0010] Step 4, considering the contact weight, dividing the discrete data in the internal contact matrix and the external contact matrix by the maximum element in the inverse processing gray value matrix and then summing them up, and deriving the discrete contact area of ​​the bonding surface solid considering the contact weight;

[0011] Step 5: To solve the problem that the external contact unit area is too large, the external contact unit area is corrected;

[0012] Step 6: To solve the problem of inaccurate calculation of the contact area of ​​the external contact unit, a secondary correction is made to the area of ​​the external contact unit, and a calculation formula for the solid discrete contact area ratio of the oil-liquid medium interface of the gantry machine tool is derived;

[0013] Step 7, derive the calculation formula of the discrete contact area ratio of the bonding surface solid without considering the contact weight, and derive the calculation formula of the discrete contact area ratio of the oil medium;

[0014] Step 8. Combined with MTALAB software, input the calculation process of the discrete contact area ratio of the bonding surface, import the actual contact density rubbing of the bonding surface, and output the actual contact area ratio of the gantry machine tool oil medium bonding surface.

[0015] Furthermore, in step 2, the specific operation of inverse processing the gray value matrix is: gray level 255 represents the discrete unit with the largest contact ratio of the bonding surface, and gray level 0 represents the discrete unit with the smallest contact ratio of the bonding surface. Let the gray value matrix be G i×j , the inverse processing gray value matrix is ​​R i×j .

[0016] Furthermore, the specific process of step 3 is: reverse processing the gray value matrix R i×j Decompose according to the internal contact unit and the external contact unit, and divide it into the internal contact matrix I i×j and the external contact matrix N i×j :

[0017] Formula 1: R i×j =I i×j +N i×j .

[0018] Furthermore, the specific process of step 4 is: considering the influence of the contact weight to accurately calculate the solid contact area, the internal contact matrix I i×j and the external contact matrix N i×jThe elements in are divided by the inverse gray value matrix R i×j Then sum up the largest elements in the matrix, and the discrete contact area of ​​the solid surface considering the contact weight is:

[0019] Formula 2:

[0020] Where: A ds is the solid discrete contact area of ​​the bonding surface considering the contact weight; n is the number of equal parts of the discrete treatment; Δx 2 is the unit area.

[0021] Furthermore, the specific process of step 5 is: establishing a quadratic function with the outer contact unit angular distance e and the outer contact unit angle θ as independent variables, wherein e is the outer contact unit angular distance, e∈(0,Δx); θ is the outer contact unit angle, θ∈(0,π), and the functional relationship is:

[0022] Formula 3:

[0023] The calculation formula for the average value of the external contact unit area after the first external contact unit area correction is as follows:

[0024] Formula 4:

[0025] Where: is the average area of ​​the external contact unit;

[0026] The formula for the solid discrete contact area of ​​the bonding surface after the first correction is:

[0027] Formula 5:

[0028] Where: κ is the external contact proportional area coefficient, which is the average area of ​​the external contact unit With the unit area Δx 2 Ratio of:

[0029] Formula 6:

[0030] Furthermore, the specific process of step 6 is: the actual contact area S of the external contact unit b The sum of the area of ​​the external contact unit S is regarded as the size of the modified quarter circle area S', S b , S and S' are related as follows:

[0031] Formula 7:

[0032] Substituting equations 4, 6, and 7 into equation 5, and the solid discrete contact area ratio being the ratio of the solid discrete contact area of ​​the bonding surface considering the contact weight to the nominal contact area, the calculation formula for the solid discrete contact area ratio of the bonding surface after secondary correction is obtained:

[0033] Formula 8:

[0034] Where: R ds is the solid discrete contact area ratio; x 2 is the nominal contact area.

[0035] Furthermore, the specific process of step 7 is: when calculating the actual contact area of ​​the oil medium, the contact weight is not considered, and the solid discrete contact area of ​​the bonding surface without considering the contact weight is:

[0036] Formula 9:

[0037] Where: A' ds is the solid discrete contact area of ​​the bonding surface without considering the contact weight; Item(I i×j ) is the number of non-zero elements in the internal contact matrix; Item(N i×j ) is the number of non-zero elements in the external contact matrix;

[0038] The discrete contact area ratio of the bonding surface solid without considering the contact weight is:

[0039] Formula 10:

[0040] Where: L 2 is the total nominal contact area between the bonding surfaces;

[0041] The discrete contact area of ​​the oil medium between the joint surfaces is:

[0042] Formula 11: A dl =L 2 -A' ds

[0043] The calculation formula of the discrete contact area ratio of the oil-liquid medium on the combined surface is:

[0044] Formula 12:

[0045] Where: Item(I i×j ) is the number of non-zero elements in the internal contact matrix; Item(N i×j ) is the number of non-zero elements in the external contact matrix.

[0046] Furthermore, the specific process of step 8 is: combined with the MTALAB software, the calculation process of the solid discrete contact area ratio and the oil-medium discrete contact area ratio in the gantry machine tool oil-medium interface is input, and the actual contact density rubbing of the gantry machine tool oil-medium interface is imported to output the actual contact area ratio of the gantry machine tool oil-medium interface.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] 1. The present invention skillfully combines theoretical calculation with MATLAB software model analysis, performs primary and secondary optimization processing on the external contact unit area according to the different contact unit types, so as to accurately calculate the solid discrete contact area ratio of the oil-liquid medium interface of the gantry machine tool, thereby providing a new calculation method.

[0049] 2. The present invention takes into account the mixing of oil medium in the joint surface of the gantry machine tool and calculates the actual contact area of ​​the oil medium between the joint surfaces of the gantry machine tool. In response to different calculation requirements, the present invention innovatively proposes a calculation method for the actual contact area ratio of the joint surface, making the calculation of the actual contact area ratio of the oil medium joint surface of the gantry machine tool more comprehensive and close to the actual working condition of the machine tool.

[0050] 3. The present invention starts from the contact ratio of the joint surface of the gantry machine tool, breaking the excessive reliance of the traditional calculation method on fractal contact theory. This method is also applicable to different types of mechanical joint surfaces, opening up a new way for the calculation and research of the actual contact area ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 The diagram is discretized and divided into contact units; (a) is the obtained contact density rubbing diagram, (b) is the schematic diagram of the contact density rubbing after discretization and division, and (c) is the schematic diagram of the contact density rubbing after partial division according to the internal contact unit and the external contact unit.

[0052] Figure 2 It is a gray value matrix diagram.

[0053] Figure 3 This is the first boundary element correction diagram.

[0054] Figure 4 This is the second boundary element correction diagram.

[0055] Figure 5 This is a flow chart for calculating the actual contact area ratio of the oil-medium interface of the gantry machine tool.

[0056] Figure 6 The present invention is a flow chart of the method. DETAILED DESCRIPTION

[0057] 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.

[0058] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0059] One embodiment of the present invention provides a method for calculating the actual contact area ratio of the oil-medium interface of a gantry machine tool, and its flow chart is as follows: Figure 6 As shown, the method comprises the following steps:

[0060] Step 1: Obtain the actual contact density of the bonding surface, discretize it and divide it into internal contact units and external contact units, such as Figure 1 shown.

[0061] The specific process of step 1 is as follows: select square specimens No. 1 and No. 2 of the gantry machine tool joint surface and clean their surfaces to improve the surface quality of the specimens. The side lengths of both specimens are d. Apply a layer of marking paint evenly on the rough surface of specimen No. 1, then place the contact surface of specimen No. 1 coated with marking paint upward on the workbench of the hydraulic testing machine, and then place the contact surface of specimen No. 2 facing downward, accurately docking with the contact surface of specimen No. 1 coated with marking paint, and apply pressure through the YAM-2000C computer-controlled electro-hydraulic servo press. The pressure rate of the press should be less than 0.8mm / min, and graded loading is performed according to the preset pressure level of 0.2MP~1.0MPa. Until the marking paint is evenly printed on the contact surface of specimen No. 2, use a high-definition camera to shoot the contact surface of specimen No. 2 to improve the shooting accuracy of the joint surface specific gravity rubbing, so as to obtain the actual contact specific gravity rubbing of the joint surface. Discretize the actual contact density rubbing of the bonding surface, set the side length of the discretized discrete unit to be x, and divide it into internal contact units and external contact units, mark the internal contact unit as i, and the external contact unit as n. The contact density rubbing diagram obtained is as follows: Figure 1 As shown in (a), the schematic diagram of the contact specific gravity rubbing after discretization is as follows Figure 1 As shown in (b), the schematic diagram of the contact density rubbing after the selection of part of the division is divided according to the internal contact unit and the external contact unit. Figure 1 As shown in (c).

[0062] Step 2, input the discretized imprint image into MATLAB software, save it as a gray value matrix and perform inverse processing;

[0063] The specific process of step 2 is as follows: First, the discretized contact imprint map is input into the MATLAB software and saved in the form of a gray value matrix, where the cell color of the matrix gray value of 255 is white, the cell color of the matrix gray value of 0 is black, and the cells with matrix gray values ​​from 0 to 255 are displayed in gray of different brightness, such as Figure 2 Next, in order to facilitate subsequent calculations, the gray value matrix is ​​processed inversely, that is, gray level 255 represents the discrete unit with the largest contact ratio of the bonding surface, and gray level 0 represents the discrete unit with the smallest contact ratio of the bonding surface. Let the gray value matrix be G i×j , the inverse processing gray value matrix is ​​R i×j .

[0064] Step 3, decomposing the inverse processing gray value matrix into an internal contact matrix and an external contact matrix according to the divided internal contact units and external contact units;

[0065] The specific process of step 3 is as follows: In order to facilitate subsequent calculations, the inverse processing gray value matrix is ​​decomposed according to the internal contact unit and the external contact unit, and divided into the internal contact matrix I i×j and the external contact matrix N i×j , then:

[0066] Formula 1: R i×j =I i×j +N i×j

[0067] Suppose that a 4×4 matrix containing an external contact unit is randomly extracted from the inverse processing gray value matrix, the extracted inverse gray value matrix is The decomposed internal contact matrix is The external contact matrix is

[0068] Step 4, considering the contact weight, dividing the discrete data in the internal contact matrix and the external contact matrix by the maximum element in the inverse processing gray value matrix and then summing them up, and deriving the discrete contact area of ​​the bonding surface solid considering the contact weight;

[0069] The specific process of step 4 is as follows: Since there are uncontacted gaps in the solid contact imprint of the bonding surface, in order to accurately calculate the solid contact area, the influence of the contact weight is considered and the internal contact matrix I is converted into i×j and the external contact matrix N i×j The elements in are divided by the inverse gray value matrix R i×j Then sum up the largest elements in the matrix, and the discrete contact area of ​​the solid surface considering the contact weight is:

[0070] Formula 2:

[0071] Where: A dsis the discrete contact area of ​​the bonding surface solid considering the contact weight, in mm 2 ; n is the number of equal parts of discrete processing. The larger the value of n, the more discrete parts of the contact specific gravity rubbing are; Δx 2 is the unit area.

[0072] Step 5: To solve the problem that the external contact unit area is too large, the external contact unit area is corrected;

[0073] The specific process of step 5 is as follows: Figure 1 As shown in (c), in fact, only the area of ​​the inner contact unit is equal to the area of ​​a single discrete unit, while the area of ​​the outer contact unit is smaller than the area of ​​a single discrete contact unit. Formula 2 is based on the assumption that the areas of all contact units are equivalent to the area of ​​a single discrete unit, which leads to an overestimation of the calculation result. Therefore, the first correction calculation should be performed on the area of ​​the outer contact unit.

[0074] like Figure 3 As shown, connect the intersection points where the contact mark boundary of the external contact unit intersects with the discrete unit boundary, and take the area S(e,θ) enclosed by the connecting line and the discrete unit boundary to simply replace the external contact unit area (the dark area in the figure). The area S(e,θ) of the dark area can be expressed as a quadratic function with the external contact unit corner distance e and the external contact unit angle θ as independent variables, where e is the external contact unit corner distance (the distance from the intersection point where the contact mark boundary of the external contact unit intersects with the discrete unit boundary to the corner point of the discrete unit unit boundary), e∈(0,Δx), in units of mm; θ is the external contact unit angle (the angle between the discrete unit boundary and the connecting line), θ∈(0,π). Due to the randomness of the microscopic surface distribution, e and θ are both uniformly randomly distributed variables. The functional relationship is:

[0075] Formula 3:

[0076] The calculation formula for the average value of the external contact unit area after the first external contact unit area correction is as follows:

[0077] Formula 4:

[0078] Where: is the average area of ​​the external contact unit, in mm 2 ;

[0079] The formula for the solid discrete contact area of ​​the bonding surface after the first correction is:

[0080] Formula 5:

[0081] Where: κ is the external contact proportional area coefficient, which is the average area of ​​the external contact unit With the unit area Δx 2The ratio is 0.15, and the calculation formula is:

[0082] Formula 6:

[0083] Step 6: To solve the problem of inaccurate calculation of the contact area of ​​the external contact unit, a secondary correction is made to the area of ​​the external contact unit, and a calculation formula for the solid discrete contact area ratio of the oil-liquid medium interface of the gantry machine tool is derived;

[0084] The specific process of step 6 is as follows: Figure 4 As shown, the contact imprint boundary of the external contact unit is usually a curve. Suppose the area enclosed by the contact imprint boundary of the external contact unit and the connecting line is S b ,In order to make the area of ​​the external contact unit more accurate and easier to calculate, the area of ​​the boundary contact unit is corrected for the second time.

[0085] The actual contact area S of the external contact unit b The sum of the area of ​​the external contact unit S is regarded as the size of the modified quarter circle area S', S b The relationship between S, S and S' is:

[0086] Formula 7:

[0087] Substituting equations 4, 6, and 7 into equation 5, and the solid discrete contact area ratio being the ratio of the solid discrete contact area of ​​the bonding surface considering the contact weight to the nominal contact area, the calculation formula for the solid discrete contact area ratio of the bonding surface after secondary correction is obtained:

[0088] Formula 8:

[0089] Where: R ds is the solid discrete contact area ratio; x 2 is the nominal contact area.

[0090] Step 7, derive the calculation formula of the discrete contact area ratio of the bonding surface solid without considering the contact weight, and derive the calculation formula of the discrete contact area ratio of the oil medium;

[0091] The specific process of step 7 is as follows: Under actual working conditions, due to the viscosity and fluidity of the oil, there are narrow gaps inside the solid contact of the bonding surface that are difficult for the oil to enter. Therefore, directly using the total area of ​​the bonding surface minus the actual solid contact area considering the contact weight to calculate the actual contact area of ​​the oil will result in an overly large calculation result. When calculating the actual contact area of ​​the oil medium, the contact weight is not considered. The discrete contact area of ​​the solid bonding surface without considering the contact weight is:

[0092] Formula 9:

[0093] Where: A'ds is the discrete contact area of ​​the bonding surface without considering the contact weight, mm 2 Item(I i×j ) is the number of non-zero elements in the internal contact matrix; Item(N i×j ) is the number of non-zero elements in the external contact matrix;

[0094] The discrete contact area ratio of the bonding surface solid without considering the contact weight is:

[0095] Formula 10:

[0096] Where: L 2 is the total nominal contact area between the bonding surfaces;

[0097] The discrete contact area of ​​the oil medium between the joint surfaces is:

[0098] Formula 11: A dl =L 2 -A' ds

[0099] The calculation formula of the discrete contact area ratio of the oil-liquid medium on the combined surface is:

[0100] Formula 12:

[0101] Where: Item(Ii × j) is the number of non-zero elements in the internal contact matrix; Item(N i×j ) is the number of non-zero elements in the external contact matrix.

[0102] Step 8. Combined with MTALAB software, input the calculation process of discrete contact area ratio of the joint surface, import the actual contact ratio of the joint surface, and output the actual contact area ratio of the oil medium joint surface of the gantry machine tool (the calculation flow chart is as follows Figure 5 shown).

[0103] The specific process of step 8 is: combined with MTALAB software, the calculation process of the inferred solid discrete contact area ratio and the oil-liquid medium discrete contact area ratio in the gantry machine tool oil-liquid medium interface is input, and the actual contact density rubbing of the gantry machine tool oil-liquid medium interface is imported to output the actual contact area ratio of the gantry machine tool oil-liquid medium interface.

[0104] 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 actual contact area ratio of the oil-medium interface of a gantry machine tool, characterized in that: The following steps are involved: Step 1, obtaining the actual contact density rubbing of the bonding surface, discretizing it and dividing it into inner contact units and outer contact units; Step 2, input the discretized imprint image into MATLAB software, save it as a gray value matrix and perform inverse processing; Step 3, decomposing the inverse processing gray value matrix into an internal contact matrix and an external contact matrix according to the divided internal contact units and external contact units; Step 4, considering the contact weight, dividing the discrete data in the internal contact matrix and the external contact matrix by the maximum element in the inverse processing gray value matrix and then summing them up, and deriving the discrete contact area of ​​the bonding surface solid considering the contact weight; Step 5: To solve the problem that the external contact unit area is too large, the external contact unit area is corrected; Step 6: To solve the problem of inaccurate calculation of the contact area of ​​the external contact unit, a secondary correction is made to the area of ​​the external contact unit, and a calculation formula for the solid discrete contact area ratio of the oil-liquid medium interface of the gantry machine tool is derived; Step 7, derive the calculation formula of the discrete contact area ratio of the bonding surface solid without considering the contact weight, and derive the calculation formula of the discrete contact area ratio of the oil medium; Step 8. Combined with MTALAB software, input the calculation process of the discrete contact area ratio of the bonding surface, import the actual contact density rubbing of the bonding surface, and output the actual contact area ratio of the gantry machine tool oil medium bonding surface.

2. The method for calculating the actual contact area ratio of the oil-liquid medium interface of a gantry machine tool according to claim 1, characterized in that: In step 2, the specific operation of inverse processing the gray value matrix is: gray level 255 represents the discrete unit with the largest contact ratio of the bonding surface, and gray level 0 represents the discrete unit with the smallest contact ratio of the bonding surface. Let the gray value matrix be G i×j , the inverse gray value matrix is ​​R i×j .

3. The method for calculating the actual contact area ratio of the oil-medium interface of a gantry machine tool according to claim 2, characterized in that: The specific process of step 3 is: reverse processing the gray value matrix R i×j Decompose according to the internal contact unit and the external contact unit, and divide it into the internal contact matrix I i×j and the external contact matrix N i×j : Formula 1: R i×j =I i×j +N i×j .

4. The method for calculating the actual contact area ratio of the oil-medium interface of a gantry machine tool according to claim 3, characterized in that: The specific process of step 4 is: considering the influence of contact weight to accurately calculate the solid contact area, the internal contact matrix I i×j and the external contact matrix N i×j The elements in are divided by the inverse gray value matrix R i×j Then sum up the largest elements in the matrix, and the discrete contact area of ​​the solid surface considering the contact weight is: Formula 2: Where: A ds is the solid discrete contact area of ​​the bonding surface considering the contact weight; n is the number of equal parts of the discrete treatment; Δx 2 is the unit area.

5. The method for calculating the actual contact area ratio of the oil-medium interface of a gantry machine tool according to claim 1, characterized in that: The specific process of step 5 is: establish a quadratic function with the outer contact unit angular distance e and the outer contact unit angle θ as independent variables, wherein e is the outer contact unit angular distance, e∈(0,Δx); θ is the outer contact unit angle, θ∈(0,π), and the functional relationship is: Formula 3: The calculation formula for the average value of the external contact unit area after the first external contact unit area correction is as follows: Where: is the average area of ​​the external contact unit; The formula for the solid discrete contact area of ​​the bonding surface after the first correction is: Formula 5: Where: κ is the external contact proportional area coefficient, which is the average area of ​​the external contact unit With the unit area Δx 2 Ratio of: Formula 6:

6. The method for calculating the actual contact area ratio of the oil-medium interface of a gantry machine tool according to claim 1, characterized in that: The specific process of step 6 is: b The sum of the area of ​​the external contact unit S is regarded as the size of the modified quarter circle area S', S b , S and S' are related as follows: Formula 7: Substituting equations 4, 6, and 7 into equation 5, and the solid discrete contact area ratio being the ratio of the solid discrete contact area of ​​the bonding surface considering the contact weight to the nominal contact area, the calculation formula for the solid discrete contact area ratio of the bonding surface after secondary correction is obtained: Formula 8: Where: R ds is the solid discrete contact area ratio; x 2 is the nominal contact area.

7. The method for calculating the actual contact area ratio of the oil-medium interface of a gantry machine tool according to claim 6, characterized in that: The specific process of step 7 is: when calculating the actual contact area of ​​the oil medium, the contact weight is not considered, and the solid discrete contact area of ​​the bonding surface without considering the contact weight is: Formula 9: Where: A' ds is the solid discrete contact area of ​​the bonding surface without considering the contact weight; Item(I i×j ) is the number of non-zero elements in the internal contact matrix; Item(N i×j ) is the number of non-zero elements in the external contact matrix; The discrete contact area ratio of the bonding surface solid without considering the contact weight is: Formula 10: Where: L 2 is the total nominal contact area between the bonding surfaces; The discrete contact area of ​​the oil medium between the joint surfaces is: Formula 11:A dl = L 2 -A' ds The calculation formula of the discrete contact area ratio of the oil-liquid medium on the combined surface is: Formula 12: Where: Item(Ii × j) is the number of non-zero elements in the internal contact matrix; Item(N i×j ) is the number of non-zero elements in the external contact matrix.

8. The method for calculating the actual contact area ratio of the oil-medium interface of a gantry machine tool according to claim 6, characterized in that: The specific process of step 8 is: combining with MTALAB software, inputting the calculation process of the solid discrete contact area ratio and the oil-medium discrete contact area ratio in the oil-medium interface of the gantry machine tool, and importing the actual contact density rubbing of the oil-medium interface of the gantry machine tool, and outputting the actual contact area ratio of the oil-medium interface of the gantry machine tool.

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