Method for acquiring contact stress of machine tool assembly interface

Abstract

The invention relates to the technical field of numerical control machine tool assembly stress detection, and discloses a method for acquiring contact stress of a machine tool assembly interface. Based on the real mapping of the contact resistance to the contact stress, the contact stress of the to-be-detected assembly interface is obtained by detecting the contact resistance value of the to-be-detected assembly interface, the contact stress obtaining process of the machine tool assembly interface is simplified, accurate obtaining of the contact stress of the machine tool assembly interface is achieved, and the working efficiency of the machine tool assembly interface is improved. And the method has high reliability and universality. According to the method for acquiring the contact stress of the machine tool assembly interface, a mapping relation model of the contact resistance and the contact stress of the assembly interface is constructed, the model considers the influence of the contact stress on the contact resistance, and the contact stress of the assembly interface is acquired through a micro-convex body distribution density function and a Hertz contact theory. And the real mapping of the contact resistance to the contact stress is realized by defining the transmission characteristic of the current passing through the rough assembly interface.

Description

Technical Field

[0001] The present invention belongs to the technical field of CNC machine tool assembly stress detection, and in particular relates to a method for obtaining contact stress of a machine tool assembly interface. Background Art

[0002] Assembly is the final step in machine tool manufacturing and a key bottleneck in improving machine tool accuracy and precision retention. The magnitude and distribution of contact stress at the assembly interface directly reflects the connection state of the assembly interface and determines the quality of the assembly. However, the strong dielectric discontinuity and material nonlinearity exhibited by rough assembly interfaces pose significant challenges to contact stress detection at assembly interfaces.

[0003] Currently, stress measurement methods for contact interfaces can be divided into two categories, depending on whether they damage the object being tested: destructive testing and nondestructive testing. Destructive stress testing methods require damage to the object being tested. The most representative destructive testing method is the blind hole method. While its advantage lies in its high accuracy, this method also requires damage to the object being tested. For critical assembly interfaces of some high-end precision instruments, destructive testing cannot be tolerated. Therefore, destructive testing methods are often not suitable for stress testing on assembly interfaces of high-end CNC machine tools.

[0004] Nondestructive testing methods measure stress without causing damage, and primarily include neutron diffraction, X-rays, photoelasticity, and ultrasonics. X-rays and photoelasticity have limited detection ranges and can only be used to measure stress within a certain depth of a workpiece surface. Neutron diffraction instruments are expensive and unsuitable for large-scale use. Ultrasonics is susceptible to industrial noise and material properties, resulting in unstable probe coupling and requiring strict control of the measurement environment to achieve accurate results.

[0005] In view of the defects of the existing technology, in order to realize the detection of interface stress of high-end CNC machine tools and improve the assembly quality of high-end CNC machine tools, it is urgent to improve the existing interface stress non-destructive testing method to improve its detection accuracy and universality. Summary of the Invention

[0006] In view of this, the present invention discloses a method for obtaining contact stress of a machine tool assembly interface, which can solve the deficiencies existing in the related art.

[0007] To achieve the above purpose, the present invention discloses the following technical solutions:

[0008] In a first aspect, the present invention provides a method for obtaining contact stress of a machine tool assembly interface, the method comprising:

[0009] A mapping relationship model between the contact resistance and contact stress of the assembly interface is constructed. The mapping relationship model is:

[0010]

[0011] Where, F is the contact stress of the assembly interface; R2 is the contact resistance; D is the fractal dimension of the rough surface; G is the surface roughness coefficient; E is the surface roughness coefficient. * -Equivalent elastic modulus of the two contact surfaces; a' L - Maximum cross-sectional area; a' c Critical contact cross-sectional area; H - material hardness; A0 - nominal contact area; ρ"2 - resistivity of the contact gap; ρ′2 - equivalent resistivity of the contact micro-convex bodies in series from two components; σ - equivalent root mean square roughness, γ-frequency related constant, take γ = 1.5;

[0012] Obtaining the contact resistance value of the assembly interface to be tested;

[0013] The contact stress value corresponding to the contact resistance value of the assembly interface to be detected in the mapping relationship model is obtained, thereby obtaining the contact stress of the assembly interface.

[0014] Preferably, the step of obtaining the contact stress value corresponding to the contact resistance value of the assembly interface to be detected in the mapping relationship model includes:

[0015] The mapping relationship model is trained by a neural network model, and the contact stress value corresponding to the contact resistance value of the assembly interface to be detected in the trained mapping relationship model is obtained.

[0016] Preferably, the training of the mapping relationship model by a neural network model includes:

[0017] Obtaining a training data set including contact resistance and corresponding contact stress of an assembly interface;

[0018] Based on the neural network model, the predicted value of the contact stress corresponding to the contact resistance of the assembly interface is obtained;

[0019] Calculate the error between the predicted value and the true value using a mean square error function;

[0020] The parameters of the neural network model are adjusted using a back-propagation algorithm and a gradient descent optimizer to minimize the mean squared error loss function.

[0021] Preferably, the neural network model comprises at least one hidden layer, and the hidden layer always adopts a nonlinear activation function.

[0022] Preferably, the gradient descent optimizer is an Adam optimizer and is configured with an adaptive learning rate.

[0023] Preferably, the contact resistance of the assembly interface is obtained by a resistance detection device, the contact stress is obtained by a neutron diffraction method or an ultrasonic method, and the training data set containing the contact resistance of the assembly interface and the corresponding contact stress is subjected to normalization preprocessing.

[0024] In a second aspect, the present invention provides a device for obtaining contact stress of a machine tool assembly interface, the device comprising:

[0025] Mapping storage unit: mapping relationship model between contact resistance and contact stress at the assembly interface;

[0026] Detection unit: detects and obtains the contact resistance value of the assembly interface to be detected;

[0027] Output unit: outputs the contact stress of the assembly interface according to the contact stress value corresponding to the contact resistance value of the assembly interface to be detected stored in the mapping storage unit.

[0028] In a third aspect, the present invention provides an electronic device, comprising:

[0029] processor;

[0030] a memory for storing processor-executable instructions;

[0031] The processor implements the steps of the above-mentioned contact stress acquisition method by running the executable instructions.

[0032] In a fourth aspect, the present invention provides a computer-readable storage medium having computer instructions stored thereon, which implement the steps of the above-mentioned contact stress acquisition method when executed by a processor.

[0033] It can be seen from the above technical solutions that, compared with the prior art, the present invention has the following technical effects:

[0034] (1) The contact stress acquisition method disclosed in the present invention can obtain contact stress by detecting resistance, thereby avoiding the problem of damage to the detection object caused by the blind hole method for detecting stress, and avoiding the problem of the ultrasonic method requiring strict requirements on the detection environment, and has universal applicability.

[0035] (2) The contact stress acquisition method of the machine tool assembly interface disclosed in the present invention constructs a mapping relationship model between the contact resistance and contact stress of the assembly interface. The model takes into account the influence of contact stress on contact resistance. Through the micro-convex body distribution density function, Hertz contact theory, and by clarifying the transmission characteristics of current passing through the rough assembly interface, the true mapping of contact resistance to contact stress is achieved. Based on the true mapping of contact resistance to contact stress, the contact stress of the assembly interface to be detected is obtained by detecting the contact resistance value of the assembly interface to be detected, which simplifies the contact stress acquisition process of the machine tool assembly interface and realizes the accurate acquisition of the contact stress of the machine tool assembly interface with high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a flowchart of a method for obtaining contact stress of a machine tool assembly interface provided by an exemplary embodiment.

[0037] Figure 2 It is a schematic structural diagram of an assembly structure provided by an exemplary embodiment.

[0038] Figure 3 It is a schematic structural diagram of a device provided by an exemplary embodiment.

[0039] Figure 4 It is a block diagram of a contact stress acquisition device for a machine tool assembly interface provided by an exemplary embodiment.

[0040] Reference numerals are: processor 502 , internal bus 504 , network interface 506 , memory 508 , and non-volatile memory 510 . DETAILED DESCRIPTION

[0041] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, like numbers in different figures represent like or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all possible implementations consistent with one or more embodiments of the present invention. Rather, they are merely examples of apparatuses and methods consistent with certain aspects of one or more embodiments of the present invention, as detailed in the appended claims.

[0042] It should be noted that in other embodiments, the steps of the corresponding method are not necessarily performed in the order shown and described in the present invention. In some other embodiments, the method may include more or fewer steps than those described in the present invention. In addition, a single step described in the present invention may be broken down into multiple steps for description in other embodiments, and multiple steps described in the present invention may be combined into a single step for description in other embodiments.

[0043] To further illustrate the present invention, the following examples are provided:

[0044] For critical assembly interfaces of high-end precision instruments, for example, when testing stress at the assembly interfaces of high-end CNC machine tools, destructive testing traces are often not allowed. However, existing non-destructive stress testing methods have low detection accuracy. For example, when X-ray and photoelastic methods detect contact stress at assembly interfaces deep from the surface, the signal value reaching the contact interface is limited, resulting in poor detection accuracy. The ultrasonic method is easily affected by industrial site noise and material properties, and the probe coupling state is unstable, affecting the measurement results.

[0045] In order to solve the deficiencies in the related art, the present invention proposes a method for obtaining contact stress of a machine tool assembly interface.

[0046] Figure 1 This is a flow chart of a method for obtaining contact stress of a machine tool assembly interface provided by an exemplary embodiment. Figure 1 As shown, the method may include the following steps S1 to S3:

[0047] Step S1: constructing a mapping relationship model between contact resistance and contact stress of the assembly interface. The mapping relationship model is:

[0048]

[0049] Where, F is the contact stress of the assembly interface; R2 is the contact resistance; D is the fractal dimension of the rough surface; G is the surface roughness coefficient; E is the surface roughness coefficient. * -Equivalent elastic modulus of the two contact surfaces; a' L - Maximum cross-sectional area; a' c Critical contact cross-sectional area; H - material hardness; A0 - nominal contact area; ρ"2 - resistivity of air gap; ρ' 2 -Equivalent resistivity of two mutually bonded rough micro-convex bodies; σ-equivalent root mean square roughness, γ-frequency related constant, take γ=1.5.

[0050] This embodiment intends to obtain the contact stress of the assembly interface to be detected by detecting the contact resistance value of the assembly interface to be detected, thereby simplifying the contact stress acquisition process of the machine tool assembly interface and improving the accuracy of obtaining the contact stress.

[0051] To accurately capture contact stress at a machine tool assembly interface, achieving a true mapping of contact resistance to contact stress is a key step. In one embodiment, the present invention constructs a mapping model between contact resistance and contact stress at an assembly interface. This model accounts for the influence of contact stress on contact resistance. By employing the asperity distribution density function, Hertzian contact theory, and clarifying the transmission characteristics of current across a rough assembly interface, this model achieves a true mapping of contact resistance to contact stress.

[0052] In this embodiment, the step of constructing a mapping relationship model between contact resistance and contact stress of an assembly interface includes the following steps 101 to 103:

[0053] Step 101 provides a theoretical basis for constructing an equivalent resistance of a multilayer dielectric assembly, specifically:

[0054] The magnitude of contact stress changes the contact state at the assembly interface, resulting in varying contact resistance across the contact layer. To better reflect and compensate for the impact of contact stress on contact resistance, this step equates the assembly structure to a structure consisting of three different materials connected in series, transforming the contact resistance at the assembly interface into a current-dependent value.

[0055] In order to more clearly describe the mapping relationship model between the contact resistance and contact stress of the assembly interface constructed by the present invention, this step explains the structure of the machine tool assembly, such as Figure 2 Figure 2 shows an exemplary schematic diagram of an assembly structure. In machine tool manufacturing, an assembly structure is formed by the contact and assembly of different components. For a given assembly structure, two components (referred to as connected component 1 and connected component 2) are assembled and contacted to form the assembly structure. The surfaces of these two components (i.e., the contact surface) form the assembly interface. The surfaces of the components are not perfectly smooth but rather rough. The tiny, irregular protrusions on the assembly interface originating from the rough surfaces of the two components are called asperities. The contact areas of these asperities on the assembly interface are called contact asperities. The areas where these asperities contact each other are called true contact areas, and their contact area is called true contact areas. The spaces formed by the asperities on the interface are called contact gaps. Several contact gaps are formed on the assembly interface. The contact layer consists of asperities and contact gaps.

[0056] When the current signal passes through a rough assembly interface, part of the current passes through the actual contact part of the contact interface, while the other part of the current passes through the contact gap. The medium in the contact gap is air. Since the resistance value of the air medium is generally quite different from that of the assembly material (mostly metal), the contact layer formed by the metal of the assembly and the contact gap in parallel creates additional resistance to current transmission, namely contact resistance. Since the contact layer formed by the metal and the contact gap in parallel creates additional resistance to current transmission, the assembly structure is equivalent to a structure in which the connected part 1, the contact layer, and the connected part 2 are connected in series, that is, the assembly structure is defined as a series structure of multiple layers of dielectrics. The equivalent resistance R * The calculation formula is:

[0057] R * =R1+R2+R3

[0058] Where, R1 is the resistance value of the connected component 1, ρ1, L1, and S1 are the resistivity, thickness, and cross-sectional area of the connected component 1, respectively;

[0059] R2-contact resistance;

[0060] R3- resistance value of connected component 2, ρ3, L3, and S2 are the resistivity, thickness, and cross-sectional area of the connected component 2, respectively.

[0061] When a certain voltage value U is applied across the assembly, U is known, and the resistances R1 and R2 of the connected parts 1 and 2 can be measured by an instrument, R1 and R2 are known. At this time, the current I passing through the assembly is:

[0062]

[0063] Where, R2 is the contact resistance, and U is the voltage across the assembly structure.

[0064] Step 102: construct a calculation function for the contact resistance of the assembly interface, specifically:

[0065] First, the resistance detection method is to apply a certain voltage value U across the assembly. In order to correlate with the resistance detection method, this step introduces the current correlation function. Furthermore, in order to accurately obtain the current magnitude passing through the assembly interface, the current density J calculation formula is introduced as follows:

[0066]

[0067] Where, E-electric field intensity;

[0068] ρ - resistivity of the material.

[0069] Furthermore, the total resistance r′2 of the contact asperities in series on the assembly interface originating from two components is calculated as follows:

[0070]

[0071] Where r1 and r3 are the resistance values of the contact asperities of the two components respectively;

[0072] l1, l3 - the heights of the contact asperities of the two components;

[0073] a′ - contact area of the contact asperities of the two components;

[0074] ρ′2- comes from the equivalent resistivity of the contact asperities of the two components in series,

[0075] In order to obtain the total current passing through the assembly interface, it is divided into the current passing through the contact micro-protrusion and the current passing through the contact gap, so the current passing through the two places needs to be calculated separately.

[0076] Therefore, the current density j' through a single contact protrusion n for:

[0077]

[0078] The current i′ passing through a single contact asperity n for:

[0079]

[0080] Where a′ n -Contact area of a single asperity contact.

[0081] Current density j at the contact gap n "for:

[0082]

[0083] Where ρ"2 is the resistivity of the air gap.

[0084] Current through the contact gap i" n for:

[0085]

[0086] Where, a" n is the area of a single contact gap;

[0087] Considering the presence of real contact areas and an air layer (lubricant layer) in the contact gap, these discrete contact areas and contact gaps are equivalent to contact resistance units connected in parallel. The current passing through the assembly interface is the result of the current through the real contact area and the current through the contact gap in parallel, so:

[0088]

[0089] Where, I′2-current value at the real contact area of the assembly interface;

[0090] I"2-current value passing through the contact gap;

[0091] A0-nominal contact area;

[0092] A a -True contact area.

[0093] The contact resistance R2 is:

[0094]

[0095] Where, U2-voltage value at both ends of the assembly interface, U2=EL2;

[0096] L2 - average thickness of the contact layer.

[0097] Step 103: construct a mapping relationship model between contact resistance and contact stress of the assembly interface, specifically:

[0098] First, the Weierstrass-Mandelbrot (WM) function is used to simulate the surface profile. The WM function expression is:

[0099]

[0100] Where, z-protrusion profile height;

[0101] xx direction coordinate value;

[0102] D - fractal dimension of the rough surface;

[0103] G-surface roughness coefficient;

[0104] γ-frequency related constant, take γ = 1.5;

[0105] m-asperity frequency number.

[0106] Among them, the curvature radius of the micro-convex body R' is:

[0107]

[0108] The deformation of the micro-convex body δ is:

[0109] δ=2 3-D π 0.5D-1 (lnγ) 1 / 2 G D-1 (a') (2-D) / 2

[0110] The two contacting rough surfaces are equivalent to a rough surface and a smooth rigid plane. The distribution of asperities on the rough surface obeys the island distribution function, which is:

[0111]

[0112] Where, a'-cross-sectional area of the micro-convex body;

[0113] a' L - maximum cross-sectional area;

[0114] Critical contact cross-sectional area a' of elastic-plastic deformation of asperities c for:

[0115]

[0116] Where, E * -Equivalent elastic modulus of the two contact surfaces,

[0117] H-hardness of softer materials;

[0118] D - fractal dimension of the rough surface;

[0119] when a'>a' c , the micro-convex body undergoes elastic deformation, a'=2a, a is the real contact area of the micro-convex body;

[0120] when a' <a' c , the micro-convex body undergoes plastic deformation, a'=a.

[0121] Furthermore, in this step, according to the Hertz contact theory, the contact loads of the elastically deformed and plastically deformed asperities are characterized as follows:

[0122]

[0123] f p =Ha′

[0124] Where, E * -Equivalent elastic modulus of the two contact surfaces, E1, E2- are the elastic moduli of the two contact surfaces;

[0125] H-hardness of softer materials;

[0126] a'-cross-sectional area of the asperity;

[0127] D - fractal dimension of the rough surface.

[0128] G-surface roughness coefficient;

[0129] γ-frequency related constant, take γ=1.5.

[0130] The total elastic contact load and plastic contact load are obtained by integrating the convex volume of the contact surface of the assembly interface:

[0131]

[0132] Where, E* is the equivalent elastic modulus of the two contact surfaces, E1, E2- are the elastic moduli of the two contact surfaces;

[0133] H-hardness of softer materials;

[0134] a'-cross-sectional area of the asperity;

[0135] D - fractal dimension of the rough surface.

[0136] G-surface roughness coefficient;

[0137] a' L - maximum cross-sectional area;

[0138] a' c Critical contact cross-sectional area;

[0139] γ-frequency related constant, take γ=1.5.

[0140] The total contact load is the sum of the elastic contact load and the plastic contact load, which is:

[0141] F=F e +F p

[0142] Since the calculation formula of the contact resistance R2 obtained in step 102 contains the actual contact A a And the average contact gap L2, in order to build the correlation between the contact resistance R2 and the assembly material, A is calculated respectively. a With L2.

[0143] The actual contact area of the rough assembly interface is:

[0144]

[0145] Where a' L - maximum cross-sectional area;

[0146] a' cCritical contact cross-sectional area;

[0147] D - fractal dimension of the rough surface.

[0148] The average contact gap between the two rough surfaces forming the assembly interface is:

[0149]

[0150] Where, P-average stress value of assembly interface, P=F / A;

[0151] σ - equivalent root mean square roughness, σ1, σ2 - root mean square roughness of the two contact surfaces;

[0152] H-hardness of the material.

[0153] The actual contact A a And the average contact gap L2 is substituted into the assembly material to obtain the correlation of the assembly interface contact resistance:

[0154]

[0155] Where, D-fractal dimension of rough surface;

[0156] A0-nominal contact area;

[0157] H-hardness of the material;

[0158] σ - equivalent root mean square roughness,

[0159] A0-nominal contact area;

[0160] a' L - maximum cross-sectional area;

[0161] a' c Critical contact cross-sectional area;

[0162] ρ"2 - resistivity of the contact gap;

[0163] ρ′2 - the equivalent resistivity of the contact asperities of the two components in series.

[0164] Finally, the mapping relationship between the contact stress and the equivalent resistance value of the assembly interface is obtained as follows:

[0165]

[0166] Where, D is the fractal dimension of the rough surface;

[0167] G-surface roughness coefficient;

[0168] E *-Equivalent elastic modulus of the two contact surfaces;

[0169] a' L - maximum cross-sectional area;

[0170] a' c Critical contact cross-sectional area;

[0171] H-hardness of the material;

[0172] A0-nominal contact area;

[0173] ρ"2 - resistivity of the contact gap;

[0174] ρ′2 - equivalent resistivity of the contact asperities in series of two components;

[0175] σ - equivalent root mean square roughness,

[0176] γ-frequency related constant, take γ=1.5.

[0177] Step S2: obtaining the contact resistance value of the assembly interface to be tested.

[0178] Step S3 , obtaining a contact stress value corresponding to the contact resistance value of the assembly interface to be detected in the mapping relationship model, thereby obtaining the contact stress of the assembly interface.

[0179] Based on step S1, a mapping relationship model between contact resistance and contact stress is constructed. In this step, the contact resistance value of the assembly interface to be detected is detected, so as to obtain the contact stress value corresponding to the contact resistance value of the assembly interface to be detected in the mapping relationship model. This simplifies the contact stress acquisition process of the machine tool assembly interface, and realizes the accurate acquisition of the contact stress of the machine tool assembly interface with high reliability.

[0180] In one embodiment, to further improve the accuracy of obtaining the contact stress values corresponding to the contact resistance values of the assembly interface to be inspected in the mapping relationship model, the mapping relationship model is trained using a neural network model. This embodiment obtains more accurate contact stress results for the assembly interface to be inspected by obtaining the contact stress values corresponding to the contact resistance values of the assembly interface to be inspected in the trained mapping relationship model.

[0181] In this embodiment, the training of the mapping relationship model by using a neural network model includes:

[0182] Obtaining a training data set including contact resistance and corresponding contact stress of an assembly interface;

[0183] Based on the neural network model, the predicted value of the contact stress corresponding to the contact resistance of the assembly interface is obtained;

[0184] Calculate the error between the predicted value and the true value using a mean square error function;

[0185] The parameters of the neural network model are adjusted using a back-propagation algorithm and a gradient descent optimizer to minimize the mean squared error loss function.

[0186] In one embodiment, the neural network model includes at least one hidden layer, and the hidden layer always adopts a nonlinear activation function.

[0187] In one embodiment, the gradient descent optimizer is an Adam optimizer and is configured with an adaptive learning rate.

[0188] Specifically, the contact resistance of the assembly interface is obtained by a resistance detection device, and the contact stress is obtained by a blind hole method, a neutron diffraction method, or an ultrasonic method. The training data set containing the contact resistance and corresponding contact stress of the assembly interface undergoes normalization preprocessing.

[0189] Figure 3 This is a schematic structural diagram of a device provided by an exemplary embodiment. Figure 3 At the hardware level, the device includes a processor 502, an internal bus 504, a network interface 506, a memory 508, and a non-volatile memory 510. Of course, it may also include hardware required for other functions. One or more embodiments of the present invention can be implemented based on software, such as the processor 502 reading the corresponding computer program from the non-volatile memory 510 into the memory 508 and then running it. Of course, in addition to software implementation, one or more embodiments of the present invention do not exclude other implementation methods, such as logic devices or a combination of software and hardware. In other words, the execution subject of the following processing flow is not limited to each logic unit, but can also be hardware or logic devices.

[0190] Please refer to Figure 4 , a contact stress acquisition device for a machine tool assembly interface can be applied to Figure 3 In the device shown, to implement the technical solution of the present invention, the device may include:

[0191] Mapping storage unit: mapping relationship model between contact resistance and contact stress at the assembly interface;

[0192] Detection unit: detects and obtains the contact resistance value of the assembly interface to be detected;

[0193] Output unit: outputs the contact stress of the assembly interface according to the contact stress value corresponding to the contact resistance value of the assembly interface to be detected stored in the mapping storage unit.

[0194] Optionally, the mapping storage unit is specifically used to:

[0195] The mapping relationship model between contact resistance and contact stress of the storage assembly interface is as follows:

[0196]

[0197] Where, F is the contact stress of the assembly interface; R2 is the contact resistance; D is the fractal dimension of the rough surface; G is the surface roughness coefficient; E is the surface roughness coefficient. * -Equivalent elastic modulus of the two contact surfaces; a' L - Maximum cross-sectional area; a' c Critical contact cross-sectional area; H - material hardness; A0 - nominal contact area; ρ"2 - resistivity of the contact gap; ρ' 2 -Equivalent resistivity of the contact asperities of the two components; σ-equivalent root mean square roughness, γ-frequency related constant, take γ=1.5.

[0198] Optionally, the detection unit includes a resistance detection device. The assembly structure is equivalent to a structure composed of three different materials connected in series, wherein two materials forming the assembly structure (the two materials may be the same) are known, and their resistances can be considered known. The contact layer resistance of the assembly structure, i.e., the contact resistance, can be obtained using existing technology.

[0199] The devices or units described in the above embodiments may be implemented by computer chips or entities, or by products having certain functions. A typical implementation device is a computer, which may be in the form of a personal computer, laptop computer, cellular phone, camera phone, smartphone, personal digital assistant, media player, navigation device, email transceiver, game console, tablet computer, wearable device, or any combination of these devices.

[0200] In a typical configuration, a computer includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0201] Memory may include non-permanent storage in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. Memory is an example of a computer-readable medium.

[0202] Computer-readable media include permanent and non-permanent, removable and non-removable media that can be used to store information using any method or technology. Information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, disk storage, quantum memory, graphene-based storage media or other magnetic storage devices, or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include transitory media such as modulated data signals and carrier waves.

[0203] For the computer-readable medium (or computer-readable storage medium) as described above or in any other form, computer instructions may be stored thereon, which, when executed by a processor, implement one or more of the above-mentioned embodiments, thereby realizing the technical solution of the present invention.

[0204] The present invention further provides a computer program that, when executed by a processor, implements one or more of the aforementioned embodiments, thereby realizing the technical solution of the present invention. The computer program may be recorded on the aforementioned or any other form of computer-readable medium, and the present invention is not limited thereto.

[0205] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0206] The foregoing description describes specific embodiments of the present invention. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims can be performed in an order different from that described in the embodiments and still achieve the desired results. Furthermore, the processes depicted in the accompanying drawings do not necessarily require the specific order shown or the sequential order to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0207] The terms used in one or more embodiments of the present invention are for the purpose of describing specific embodiments only and are not intended to limit one or more embodiments of the present invention. The singular forms "a", "an", "the" and "the" used in one or more embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0208] It should be understood that although the terms first, second, third, etc. may be used to describe various information in one or more embodiments of the present invention, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of one or more embodiments of the present invention, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining."

[0209] The above description is merely a preferred embodiment of one or more embodiments of the present invention and is not intended to limit one or more embodiments of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present invention shall be included in the scope of protection of one or more embodiments of the present invention.

Claims

1. A method for obtaining contact stress of a machine tool assembly interface, characterized in that: The method comprises: A mapping relationship model between the contact resistance and contact stress of the assembly interface is constructed. The mapping relationship model is: Where, F is the contact stress of the assembly interface; R2 is the contact resistance; D is the fractal dimension of the rough surface; G is the surface roughness coefficient; E is the surface roughness coefficient. * -Equivalent elastic modulus of the two contact surfaces; a' L - Maximum cross-sectional area; a' c Critical contact cross-sectional area; H - material hardness; A0 - nominal contact area; ρ"2 - resistivity of the contact gap; ρ' 2 - the equivalent resistivity of the contact asperities in series between two components; σ - the equivalent root mean square roughness, γ-frequency related constant, take γ = 1.5; Obtaining the contact resistance value of the assembly interface to be tested; The contact stress value corresponding to the contact resistance value of the assembly interface to be detected in the mapping relationship model is obtained, thereby obtaining the contact stress of the assembly interface.

2. The contact stress acquisition method according to claim 1, wherein: Obtaining a contact stress value corresponding to the contact resistance value of the assembly interface to be detected in the mapping relationship model includes: The mapping relationship model is trained by a neural network model, and the contact stress value corresponding to the contact resistance value of the assembly interface to be detected in the trained mapping relationship model is obtained.

3. The contact stress acquisition method according to claim 2, wherein: The training of the mapping relationship model by a neural network model includes: Obtaining a training data set including contact resistance and corresponding contact stress of an assembly interface; Based on the neural network model, the predicted value of the contact stress corresponding to the contact resistance of the assembly interface is obtained; Calculate the error between the predicted value and the true value using a mean square error function; The parameters of the neural network model are adjusted using a back-propagation algorithm and a gradient descent optimizer to minimize the mean squared error loss function.

4. The contact stress acquisition method according to claim 2 or 3, characterized in that: The neural network model includes at least one hidden layer, and the hidden layer always adopts a nonlinear activation function.

5. The contact stress acquisition method according to claim 3, wherein: The gradient descent optimizer is the Adam optimizer, and is configured with an adaptive learning rate.

6. The contact stress acquisition method according to claim 3, wherein: The contact resistance of the assembly interface is obtained by a resistance detection device, the contact stress is obtained by a blind hole method, a neutron diffraction method or an ultrasonic method, and the training data set containing the contact resistance of the assembly interface and the corresponding contact stress is subjected to normalization preprocessing.

7. A contact stress acquisition device for a machine tool assembly interface, characterized in that: The device comprises: Mapping storage unit: mapping relationship model between contact resistance and contact stress at the assembly interface; Detection unit: detects and obtains the contact resistance value of the assembly interface to be detected; Output unit: outputs the contact stress of the assembly interface according to the contact stress value corresponding to the contact resistance value of the assembly interface to be detected stored in the mapping storage unit.

8. An electronic device, characterized in that: include: processor; a memory for storing processor-executable instructions; The processor implements the steps of the method according to any one of claims 1 to 6 by running the executable instructions.

9. A computer-readable storage medium having computer instructions stored thereon, characterized in that: When the instruction is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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