Parts rough surface contact detection method based on global nearest point partition search

Abstract

The invention discloses a part rough surface contact detection method based on global nearest point partition search. Comprising the following steps: firstly, obtaining rough morphology curved surfaces corresponding to two contact surfaces in a product part, marking the rough morphology curved surfaces as a main rough morphology curved surface and an auxiliary rough morphology curved surface, and dividing the main rough morphology curved surface into a plurality of local areas; then, a plurality of slave contact points of the slave rough morphology curved surface are determined, the influence condition of each slave contact point on the local area of the master rough morphology curved surface is judged according to the influence radius of each slave contact point, and the influenced local area corresponding to each slave contact point is obtained; and then, calculating a local nearest point of each slave contact point in the corresponding affected local area by using a nearest point projection method, generating a global nearest point of each slave contact point, and further judging the contact state of each slave contact point and the main rough morphology curved surface. The calculation cost for judging the contact state is reduced, and the calculation time is shortened.

Description

Technical Field

[0001] The present invention relates to the field of calculating the contact deformation of the rough surface topography of parts at the microscale, and specifically relates to a method for detecting the contact of the rough surface of parts based on global nearest point partition search. Background Art

[0002] Calculating the deformation after the rough surface topographies of product parts come into contact with each other is the basis for analyzing contact performance such as the contact area, contact resistance, and contact thermal resistance of product parts. Finite element analysis is the most common method for calculating the contact deformation of rough surface topographies. When using spline surfaces (such as NURBS) to represent rough surface topographies and using NURBS basis functions as the basis functions for finite element analysis, such finite element analysis is also called isogeometric analysis. Compared with the classical finite element analysis using polynomials as basis functions, the NURBS basis functions of isogeometric analysis have high-order continuity at nodes, which is more conducive to contact state detection.

[0003] When calculating the contact deformation between parts with ideally smooth surfaces, isogeometric analysis mostly uses the nearest point projection method to find the projection point of the contact point on the secondary surface from the surface, and this projection point is the nearest point from the contact point to the primary surface. Then, according to the relative position relationship between the contact point and the nearest point, it is determined whether contact occurs between the secondary surface and the primary surface. However, when the part surface has a rough topography, there will be multiple projection points of the contact point on the rough topography of the primary surface, which causes the nearest point projection method to randomly converge to a projection point that may not necessarily be the nearest point, resulting in incorrect contact detection results. Therefore, existing methods all use genetic algorithms to find the global nearest point of the contact point on the rough topography. Although genetic algorithms are effective, their computational efficiency is too low. Therefore, it is necessary to construct a more efficient method for finding the nearest point of the contact point on the rough topography. Summary of the Invention

[0004] In order to solve the problems in the background art, the present invention proposes a method for detecting the contact of the rough surface of parts based on global nearest point partition search.

[0005] The technical solution of the present invention is as follows:

[0006] 1. A method for detecting the contact of the rough surface of parts based on global nearest point partition search

[0007] Step 1: Obtain the rough surface topography surfaces corresponding to two contact surfaces in a product part, and denote them as the primary rough surface topography surface and the secondary rough surface topography surface. Divide the primary rough surface topography surface into several local regions;

[0008] Step 2: Determine a number of secondary contact points on the rough surface topography. Based on the influence radius of each secondary contact point, judge the influence of each secondary contact point on the local area of the main rough surface topography, and obtain the affected local area corresponding to each secondary contact point;

[0009] Step 3: Use the closest point projection method to calculate the local closest point of each secondary contact point in the corresponding affected local area and generate the global closest point of each secondary contact point. Then judge the contact state between the secondary contact point and the main rough surface topography. Traverse and judge the contact states of all secondary contact points to complete the contact state detection between the rough surface topographies.

[0010] In the above Step 1, the main rough surface topography is divided into several local areas, specifically:

[0011] Take all the NURBS knot vector element values in the main rough surface topography as the parameter coordinates of the segmentation points, so as to generate multiple segmentation points. After using the segmentation points to divide the main rough surface topography, several local areas are obtained.

[0012] The above Step 2 is specifically:

[0013] Step 2.1: Take the Gaussian points of each NURBS patch in the secondary rough surface topography as the secondary contact points of the secondary rough surface topography;

[0014] Step 2.2: Determine the segmentation point with the lowest height in the main rough surface topography and record the height difference between this segmentation point and each secondary contact point as the influence radius of the current secondary contact point; if there is at least one segmentation point in a certain local area whose horizontal distance from the current secondary contact point is less than the influence radius of the current secondary contact point, then this local area is the affected local area of the current secondary contact point;

[0015] Step 2.3: Repeat Step 2.2, traverse and process the remaining secondary contact points of the secondary rough surface topography, so as to obtain the affected local areas corresponding to all secondary contact points.

[0016] In the above Step 3, the global closest point of each secondary contact point is the local closest point closest to the secondary contact point among all the local closest points of the current secondary contact point.

[0017] In the above Step 3, judge the contact state between the secondary contact point and the main rough surface topography, specifically:

[0018] If the direction from each secondary contact point to its global closest point is the same as the outer normal direction of the global closest point in the main rough surface topography, then there is contact between the current secondary contact point in the secondary rough surface topography and the main rough surface topography, otherwise there is no contact.

[0019] II. A part rough surface contact detection system based on global closest point partition search

[0020] A rough surface morphology obtaining unit for generating rough surface morphologies corresponding to two contact surfaces in a product part;

[0021] A region segmentation unit for dividing the main rough surface morphology into several local regions;

[0022] A determining unit for secondary contact points and their affected local regions, for determining several secondary contact points on the secondary rough surface morphology, and judging the influence of each secondary contact point on the local regions of the main rough surface morphology according to the influence radius of each secondary contact point, to obtain the affected local regions corresponding to each secondary contact point;

[0023] A global nearest point generating unit for secondary contact points, for calculating the local nearest points of each secondary contact point in the corresponding affected local region using the nearest point projection method, so as to generate the global nearest points of the secondary contact points;

[0024] A contact state judging unit for secondary contact points, for judging the contact state between the secondary contact point and the main rough surface morphology according to the secondary contact point and its global nearest point.

[0025] III. A computer device

[0026] The device includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of the part rough surface contact detection method based on global nearest point partition search are implemented.

[0027] IV. A computer-readable storage medium

[0028] The medium stores a computer program, and when the computer program is executed by a processor, the steps of the part rough surface contact detection method based on global nearest point partition search are implemented.

[0029] V. A computer program product

[0030] The product includes a computer program / instructions, and when the computer program / instructions are executed by a processor, the steps of the part rough surface contact detection method based on global nearest point partition search are implemented.

[0031] The beneficial effects of the present invention are:

[0032] The present invention divides the rough surface morphology in NURBS form into several local regions, so that there is only one or no projection point of the secondary contact point on each local region, thereby avoiding the phenomenon that the nearest point projection method randomly converges to a certain projection point on the rough surface morphology.

[0033] The present invention proposes a definition method for the influence radius, which reduces the number of regions required to calculate the local nearest points from the contact point on each local region of the main rough surface topography, and shortens the time required to finally calculate the global nearest point from the contact point on the main rough surface topography.

[0034] Compared with the contact state detection method based on the genetic algorithm, the contact state detection method based on segmented local nearest point projection proposed by the present invention can obtain the same calculation results as the former, but the required calculation time is greatly reduced.

[0035] Therefore, the present invention overcomes the deficiency that the nearest point projection method is sensitive to the initial guess point when applied to the contact state detection of rough surface topography, and thus is prone to falling into the local nearest point, and reduces the calculation amount of solving the global nearest point by defining the influence radius. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a flow chart of the method of the present invention.

[0037] Figure 2 It is a schematic diagram of the rough surface topography contact problem and the Gaussian points from the rough surface topography in the embodiment of the present invention.

[0038] Figure 3 It is a schematic diagram of the segmentation points and local regions of the main rough surface topography in the embodiment of the present invention.

[0039] Figure 4 It is a schematic diagram of the influence radius of the slave contact point on the main rough surface topography in the embodiment of the present invention.

[0040] Figure 5 It is a schematic diagram of the affected local region corresponding to the slave contact point on the main rough surface topography and the initial guess values of the nearest point parameter coordinates of the nearest point projection method on the local region in the embodiment of the present invention.

[0041] Figure 6 It is a schematic diagram of the local nearest point and the global nearest point of the slave contact point on the main rough surface topography in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] The present invention will be further described in detail below with reference to the drawings and embodiments.

[0043] As Figure 1 shown, Figure 1 the block diagram is the flow chart of the part rough surface contact detection method based on global nearest point partition search proposed by the present invention. Specifically, it includes the following steps:

[0044] Step 1: The rough surface topography contact problem in this embodiment is as Figure 2As shown, the rough morphology surfaces corresponding to two contact surfaces in the product parts are generated and obtained, and the rough morphology surfaces are in the form of NURBS surfaces. Among them, the main rough morphology surface and the secondary rough morphology surface are relative concepts. The main rough morphology surface is a NURBS rough morphology defined on a rectangular area with a size of 2 mm × 2 mm, and the secondary rough morphology surface is a NURBS rough morphology defined on a rectangular area with a size of 1 mm × 1 mm. Taking the Gaussian points of the secondary rough morphology NURBS patches as the secondary contact points, it shows how to use the part rough surface contact detection method based on global nearest point partition search proposed by the present invention to calculate the global nearest points of the secondary contact points on the main rough morphology, and then judge the contact state.

[0045] The formula for the main rough morphology surface in NURBS form is as follows:

[0046]

[0047] Where S(ξ,η) is the main rough morphology surface, ξ and η are the coordinate values in the ξ direction and η direction in the parameter space, n is the number of control points along the ξ direction in the parameter space, m is the number of control points along the η direction in the parameter space, is the NURBS basis function, p is the order of the basis function along the ξ direction in the parameter space, q is the order of the basis function along the η direction in the parameter space, B i,j is the coordinate of the control point (i,j) corresponding to the NURBS basis function in the physical space.

[0048] It is determined by the knot vector Ξ along the ξ direction and the knot vector Η along the η direction. Ξ contains n - p + 1 different element values, and Η contains m - q + 1 different element values. Taking these element values as the segmentation point parameter coordinates, the main rough morphology surface S(ξ,η) can be divided into (n - p)·(m - q) local regions.

[0049] The order, knot vector, control point coordinates and their weights of the main rough morphology surface in each parameter direction are shown in Table 1. As Figure 3 shown, all the NURBS knot vector element values in the main rough morphology surface are used as the parameter coordinates of the segmentation points, so as to generate a plurality of segmentation points. After the main rough morphology surface is segmented by using the segmentation points, several local regions are obtained.

[0050] Table 1 is the order, knot vector, control point coordinates and their weights of the main rough morphology surface in each parameter direction

[0051]

[0052]

[0053] Step 2 is specifically as follows:

[0054] Step 2.1: Since the present invention determines the contact state between rough profiles based on Gaussian point - surface contact, the Gaussian points of each NURBS patch on the rough profile surface are selected as the slave contact points of the rough profile surface.

[0055] Step 2.2: Determine the segmentation point with the lowest height on the master rough profile surface, and record the height difference between this segmentation point and each slave contact point as the influence radius of the current slave contact point. For example, first calculate the coordinates of each segmentation point of the master rough profile surface in the physical space, and screen out the minimum value of the z - coordinate among the segmentation points. Then calculate the z - coordinate of the slave contact point on the rough profile surface. And The distance between them is used as the influence radius r of the slave contact point, that is, e , namely As Figure 4 shown. If there is at least one segmentation point in a certain local area whose horizontal distance from the current slave contact point is less than the influence radius of the current slave contact point, then this local area is the affected local area of the current slave contact point; each local area of the master rough profile surface contains four segmentation points as vertices. Calculate the two horizontal distances from each vertex of the local area to the slave contact point in the physical space along the x - direction and y - direction respectively. The two horizontal distances are and and are the x - and y - direction coordinate values of the vertex , and are the x - and y - direction coordinate values of the slave contact point . If the horizontal distance l x or l y is less than the influence radius r e , then this local area is recorded as the affected local area. As Figure 5 shown, the master rough profile surface is divided into 25 local areas, among which 8 are the affected local areas of a slave contact point.

[0056] Step 2.3: Repeat Step 2.2 to traverse and process the remaining slave contact points on the rough profile surface, so as to obtain the affected local areas corresponding to all slave contact points.

[0057] Step 3: Use the nearest point projection method to calculate the local nearest points of each slave contact point in the corresponding affected local area and generate the global nearest points of each slave contact point, and then judge the contact state between the slave contact point and the main rough surface topography. Traverse and judge the contact states of all slave contact points to complete the detection of the contact state between rough surface topographies.

[0058] As Figure 5 shown, denote the value ranges of the parametric coordinates of the local area in the ξ direction and η direction as [ξ1, ξ2] and [η1, η2] respectively. Let the initial guess value [ξ c0 , η c0 for calculating the parametric coordinates of the nearest point of the slave contact point on this local area by the nearest point projection method be Thus, calculate the parametric coordinates of the nearest point of the slave contact point on each local area and use them as the local nearest points. If the nearest point projection method cannot find a projection point as the nearest point on a certain local area, it is considered that there is no local nearest point of the slave contact point in this local area, and the global nearest point will be selected from the local nearest points on other local areas. As Figure 6 shown, compare the distances between all local nearest points and the slave contact point, and take the local nearest point with the smallest distance as the global nearest point

[0059] The global nearest point of each slave contact point is the local nearest point that is closest to the slave contact point among all local nearest points of the current slave contact point.

[0060] Judge the contact state between the slave contact point and the main rough surface topography, specifically:

[0061] If the direction from each slave contact point to its global nearest point is the same as the outer normal direction of the global nearest point in the main rough surface topography, then there is contact between the current slave contact point on the slave rough surface topography and the main rough surface topography, otherwise there is no contact. Specifically, calculate the vector n from the slave contact point to the global nearest point c and the dot product g of the outer normal direction of the main rough surface topography at the position of the global nearest point. If the directions of n N and c are the same, then g >0, and there is contact between the slave rough surface topography at the position of this slave contact point and the main rough surface topography, otherwise there is no contact. N >0, there is contact between the slave rough surface topography at the position of this slave contact point and the main rough surface topography, otherwise there is no contact.

[0062] Use the method of the present invention and the genetic algorithm respectively to calculate 3 different slave contact points in as Figure 3The global nearest points on the shown main rough surface topography, obtained coordinates, g N The comparison of the obtained coordinates, g values and calculation time consumption is shown in Table 2. It can be seen from Table 2 that the results obtained by the two methods are very close, but the calculation time consumption of the method of the present invention is about 30% of that of the genetic algorithm on average, verifying the effectiveness and superiority of the method of the present invention in substituting the genetic method for contact state detection.

[0063] Table 2 is a table of the results of calculating the nearest points and calculation time consumption of three different using the method of the present invention and the genetic algorithm

[0064]

[0065] The present invention also provides a part rough surface contact detection system based on global nearest point partition search. The system includes:

[0066] A rough topography surface acquisition unit, configured to generate rough topography surfaces corresponding to two contact surfaces in a product part;

[0067] A region segmentation unit, configured to segment the main rough topography surface into several local regions;

[0068] A determining unit for slave contact points and their affected local regions, configured to determine several slave contact points on the rough topography surface, and judge the influence of each slave contact point on the local regions of the main rough topography surface according to the influence radius of each slave contact point, and obtain the affected local regions corresponding to each slave contact point;

[0069] A global nearest point generation unit for slave contact points, configured to calculate the local nearest points of each slave contact point in the corresponding affected local region using the nearest point projection method, so as to generate the global nearest points of the slave contact points;

[0070] A contact state judging unit for slave contact points, configured to judge the contact state between the slave contact points and the main rough topography surface according to the slave contact points and their global nearest points.

[0071] The present invention also provides a computer device, which includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of the part rough surface contact detection method based on global nearest point partition search are implemented.

[0072] The present invention also provides a computer-readable storage medium

[0073] The medium stores a computer program, and when the computer program is executed by a processor, the steps of the part rough surface contact detection method based on global nearest point partition search are implemented.

[0074] The present invention also provides a computer program product

[0075] The product includes a computer program / instructions, and when the computer program / instructions are executed by a processor, the steps of the method for detecting the contact of the rough surface of a part based on global nearest point partition search are implemented.

[0076] The above embodiments are only specific embodiments of the present invention, which are used to illustrate the technical solutions of the present invention rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: any person skilled in the art within the technical scope disclosed by the present invention can still modify the technical solutions recorded in the foregoing embodiments, or can easily conceive of changes, or perform equivalent replacements on some of the technical features; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the present invention, and should all be covered by the protection scope of the present invention.

Claims

1. A method for detecting the contact of a rough surface of a part based on global nearest point partition search, characterized in that Including the following steps: Step 1: Obtain the rough topography surfaces corresponding to two contact surfaces in the product part, and denote them as the main rough topography surface and the secondary rough topography surface. Divide the main rough topography surface into several local regions; Step 2: Determine several secondary contact points on the secondary rough topography surface. According to the influence radius of each secondary contact point, judge the influence of each secondary contact point on the local regions of the main rough topography surface, and obtain the affected local regions corresponding to each secondary contact point; Step 3: Use the closest point projection method to calculate the local closest point of each secondary contact point in the corresponding affected local region and generate the global closest point of each secondary contact point. Then, judge the contact state between the secondary contact point and the main rough topography surface. Traverse and judge the contact states of all secondary contact points to complete the detection of the contact state between the rough topography surfaces; 2. The method for detecting the contact of a rough surface of a part based on global nearest point partition search according to claim 1, wherein In the said Step 1, dividing the main rough topography surface into several local regions specifically means: Take all the NURBS knot vector element values in the main rough topography surface as the parameter coordinates of the segmentation points, thereby generating multiple segmentation points. After using the segmentation points to divide the main rough topography surface, several local regions are obtained; 3. A method for detecting the contact of a rough surface of a part based on global nearest point partition search according to claim 1, characterized in that The said Step 2 specifically means: Step 2.1: Take the Gauss points of each NURBS patch in the secondary rough topography surface as the secondary contact points of the secondary rough topography surface; Step 2.2: Determine the segmentation point with the lowest height in the main rough topography surface and record the height difference between this segmentation point and each secondary contact point as the influence radius of the current secondary contact point. If the horizontal distance between at least one segmentation point and the current secondary contact point in a certain local region is less than the influence radius of the current secondary contact point, then this local region is the affected local region of the current secondary contact point; Step 2.3: Repeat Step 2.2, traverse and process the remaining secondary contact points of the secondary rough topography surface, so as to obtain the affected local regions corresponding to all secondary contact points; 4. A method for detecting the contact of a rough surface of a part based on global nearest point partition search according to claim 1, characterized in that In the said Step 3, the global closest point of each secondary contact point is the local closest point closest to the secondary contact point among all the local closest points of the current secondary contact point; 5. A method for detecting the contact of a rough surface of a part based on global nearest point partition search according to claim 1, characterized in that In the said Step 3, judging the contact state between the secondary contact point and the main rough topography surface specifically means: If the direction from each secondary contact point to its global closest point is the same as the outer normal direction of the global closest point in the main rough topography surface, then contact occurs between the current secondary contact point in the secondary rough topography surface and the main rough topography surface, otherwise no contact occurs; 6. A part rough surface contact detection system based on global nearest point partition search, characterized in that, Including: A rough topography surface acquisition unit for generating the rough topography surfaces corresponding to two contact surfaces in the product part; A region segmentation unit for dividing the main rough topography surface into several local regions; A secondary contact point and its affected local region determination unit for determining several secondary contact points of the secondary rough topography surface, and judging the influence of each secondary contact point on the local regions of the main rough topography surface according to the influence radius of each secondary contact point, and obtaining the affected local regions corresponding to each secondary contact point; A global closest point generation unit of the secondary contact point for using the closest point projection method to calculate the local closest point of each secondary contact point in the corresponding affected local region, thereby generating the global closest point of the secondary contact point; A contact state determination unit for the slave contact point, which is used to determine the contact state between the slave contact point and the main rough surface according to the slave contact point and its globally nearest point.

7. A computer device, comprising a memory and a processor, the memory storing a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the part rough surface contact detection method based on globally nearest point partition search according to any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the part rough surface contact detection method based on globally nearest point partition search according to any one of claims 1 to 5.

9. A computer program product, comprising a computer program / instructions, characterized in that, When the computer program / instruction is executed by the processor, it implements the steps of the part rough surface contact detection method based on globally nearest point partition search according to any one of claims 1 to 5.

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