Three-directional excitation high-end machine tool joint surface contact characteristic testing device and method

Abstract

The application discloses a three-directional vibration high-end machine tool joint surface contact characteristic testing device and method, and belongs to the field of machine tool dynamic characteristic analysis. The testing device and process mainly comprise the following steps: before testing, a first support and a second support are fixed on a base through bolts, a tested piece is screwed on a boss of the base through a pre-tightening bolt, and a vibration exciter system is hung on the support through a rope; a vibration mode database in a computer is called, the number of sensors and a layout position scheme are determined according to the vibration mode of a tested piece with different structures; the sensors are pasted on the tested piece according to the obtained scheme, the output ends of the sensors are connected to the computer through a signal acquisition system, and the contact characteristic of the machine tool joint surface is obtained by processing the computer. The device has the advantages of simple structure, convenient loading and unloading, easy repeated experiment, sensor layout scheme according to the shape of the tested piece, and fast and accurate measurement of the dynamic characteristic of the machine tool joint surface.

Description

Technical Field

[0001] This invention belongs to the field of machine tool dynamic characteristic analysis, and relates to a device and method for testing the contact characteristics of high-end machine tool mating surfaces under triaxial excitation. Background Technology

[0002] Bolted joint surfaces are generally weak points in machine tool structures. Under external loads, they exhibit complex dynamic characteristics, exhibiting both elasticity and damping, significantly impacting the overall dynamic performance of the machine. Many complex factors influence the dynamic characteristics of these joint surfaces, including the material of the joint surface, its machining method, and its assembly process.

[0003] Currently, analytical methods based on theoretical models and finite element simulations have been proposed. The idea is to study the contact stiffness and contact damping of the interface from a microscopic perspective and verify them experimentally using finite element methods. However, given the numerous factors affecting the dynamic characteristics of the interface, finite element verification often has limitations, necessitating on-site experimental research to corroborate the validity of the theoretical model.

[0004] To systematically study the influence of contact load on the contact stiffness and contact damping of bolted joint surfaces in machine tools, a complete testing device is needed. However, existing dynamic characteristic testing devices for bolted joint surfaces mainly rely on unidirectional excitation to identify normal contact stiffness and contact damping. Therefore, to obtain the contact stiffness and contact damping of bolted joint surfaces in different excitation directions and to enable users to conveniently and quickly formulate testing schemes, a high-end machine tool joint surface contact characteristic testing device and method with triaxial excitation has been developed. Summary of the Invention

[0005] The technical problem this invention aims to solve is to design an experimental device that can measure the contact stiffness and contact damping of bolted joint surfaces from three directions, allowing users to quickly specify the sensor arrangement scheme based on the shape and size of the test specimen. This invention designs a bolted joint test specimen, adjusting the contact load on the joint surface by changing the torque of the preload bolts; measuring the contact stiffness and contact damping of the bolted joint surface in different directions by adjusting the rope passing through different lifting frames or support frames of the vibrator fixing frame; and obtaining the sensor arrangement scheme for the specimen by querying a specimen vibration mode database.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A high-end machine tool mating surface contact characteristic testing device with three-dimensional excitation includes: a base, a first support, a second support, a vibrator, a vibrator fixing frame, an impedance head, a rope, a test piece, preload bolts, support bolts, a sensor, a signal acquisition system, and a computer.

[0008] Connections between the various parts that make up the device:

[0009] The first bracket is fixed to the base by bracket bolts; the second bracket is fixed to the base by bracket bolts; the exciter is placed in the exciter fixing frame, forming the exciter assembly; the impedance head is installed on the excitation end of the exciter, forming the excitation system with the exciter assembly; the excitation system is suspended on the bracket by a rope passing through the lifting frame in the exciter assembly; the specimen is fixed to the boss of the base by pre-tightening bolts; the acceleration sensor is fixed to the specimen by glue; the output end of the acceleration sensor is connected to the computer through the signal acquisition system.

[0010] Compared with existing technologies, the present invention has the following advantages:

[0011] (1) By changing the different lifting frames or support frames through which the rope passes through the vibrator fixing frame, the contact stiffness and contact damping during normal and tangential excitation can be measured.

[0012] (2) The computer has a built-in vibration mode database. During the test, the modal vibration mode of the test specimen is obtained by querying the shape and size of the specimen, and the sensor arrangement scheme is determined according to the vibration mode.

[0013] (3) The experimental setup is simple in structure, easy to replace, and can meet the requirements of repeatable experiments. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the high-end machine tool mating surface contact characteristic testing device with triaxial excitation according to the present invention.

[0015] Figure 2 This is a top view of the high-end machine tool mating surface contact characteristic testing device with triaxial excitation according to the present invention.

[0016] Figure 3 This is a schematic diagram of the base of this experimental setup.

[0017] Figure 4 This is a schematic diagram of the vibrator mounting frame.

[0018] Figure 5 This is a schematic diagram of the specimen vibration mode database.

[0019] Figure 6 This is the test flowchart for this method. Detailed Implementation

[0020] The following description, in conjunction with the working principle and structural drawings, further explains the experimental device for testing the contact stiffness and contact damping of the three-dimensional bolted joint surface of the present invention.

[0021] like Figure 1-6As shown, a high-end machine tool mating surface contact characteristic testing device with three-dimensional excitation includes: a base 1, a first bracket 2, a second bracket 3, a vibrator 4, a vibrator fixing frame 5, a rope 6, an impedance head 7, a test piece 8, and preload screws. The first bracket 2 and the second bracket 3 are support frames for suspending the vibrator system. The first bracket 2 is fixed to the base 1 by bracket bolts 10, and the second bracket 3 is fixed to the base 1 by bracket bolts 10. The base 1 is as follows: Figure 3 As shown. Specimen 8 has bolt holes and is fixed to the boss of base 1 by pre-tightening bolts 9. The vibrator 4 is placed in the vibrator fixing frame 5, forming the vibrator assembly. The vibrator fixing frame 5 is as shown... Figure 4 As shown. Impedance head 7 is installed at the excitation end of exciter 4, forming an excitation system with the exciter assembly. Rope 6 passes through the lifting frame of exciter fixing frame 5 and can be suspended on the first support 2 or the second support 3. Rope 6 passes through the (5-1) lifting frame of exciter fixing frame 5 and can be suspended on the first support 2 for normal excitation. Rope 6 passes through the (5-2) lifting frame of exciter fixing frame 5 and can be suspended on the first support 2 for tangential excitation. By querying the mode shape database, the number and position of sensors are selected according to their mode shapes. The sensors are fixed to the specimen 8 with glue. The sensors are connected to an external signal acquisition system to transmit the vibration signal received by the mating surface to the computer.

[0022] During testing, specimen 8 was first fixed to the boss of base 1 using pre-tightening bolts 9. Then, the first bracket 2 and the second bracket 3 were installed. Next, the exciter 4 was placed in the exciter fixing frame 5, and the impedance head 7 was installed at the excitation end of the exciter 4. The sensor was attached to specimen 8, and then connected to an external signal acquisition system to transmit the vibration signal received by the mating surface to a computer. During the experiment, the load on the mating surface was changed by altering the torque of the pre-tightening bolts 9. Multiple sets of experimental data were extracted, and the influence of the load on the contact stiffness and contact damping of the mechanical mating surface was determined using a modeling method for the stiffness and damping of the mechanical mating surface.

[0023] Principle of contact stiffness test at fixed mating surfaces:

[0024] For ease of calculation, the contact between two rough surfaces can be simplified to the contact between a rigid plane and a rough surface, where the profile of the rough surface can be described by a three-dimensional WM function, and a single micro-protrusion of the rough surface has the following relationship.

[0025] (1)

[0026] (2)

[0027] (3)

[0028] (4)

[0029] In the formula: denoted as denoted as the normal deformation of the micro-protrusion; denoted as a, the contact area of ​​a single micro-protrusion; denoted as D, the fractal dimension; and denoted as G, the fractal roughness. D and G are parameters used in fractal theory to characterize the three-dimensional morphology of a surface. The contour of the bonding surface is obtained by a surface profilometer, and D and G are obtained by the power spectral density method. is the size parameter of the spectral density, typically 1.5; R represents the radius of curvature of a single micro-convexity; It is the critical cross-sectional area at which the micro-convex body undergoes elastoplastic deformation; E represents the composite elastic modulus. , , , , These are the elastic modulus and Poisson's ratio of the two contacting materials, respectively. It is the critical cross-sectional area at which the micro-convex body undergoes plastic deformation.

[0030] The normal loads on a single micro-protrusion in the perfectly elastic, elastoplastic, and plastic stages can be expressed as follows:

[0031] (5)

[0032] (6)

[0033] (7)

[0034] In the formula: The coefficient is related to material properties and fractal parameters of the interface; H is the hardness of the softer material.

[0035] The normal contact stiffness of a single micro-convex body can be expressed as:

[0036] (8)

[0037] Based on the MB fractal model, an expansion factor for the distribution domain of micro-contact point size is introduced, resulting in the distribution function of the contact point size for a micro-contact cross-sectional area as follows:

[0038] (9)

[0039] (10)

[0040] In the formula: The domain extension factor is obtained from formula 10; This indicates the maximum contact area of ​​the micro-protrusion. W is the normal load.

[0041] In the fully elastic deformation region ( ), elastic-plastic deformation region ( Integrating over ), the total stiffness of the bonding surface can be expressed as:

[0042] (11)

[0043] Fixed interface contact damping analysis theory:

[0044] Energy stored per cycle by a single micro-protrusion during contact deformation With dissipated energy Represented as:

[0045] (12)

[0046] (13)

[0047] By integrating the periodically stored energy and dissipated energy in the fully elastic deformation region and the plastic deformation region, the elastic strain energy and plastic strain energy at the interface are obtained as follows:

[0048] (14)

[0049] (15)

[0050] The total contact damping of the mating surface can be expressed as:

[0051] (16)

[0052] In the formula: M is the structural mass; K is the contact stiffness of the mating surface.

[0053] The mode shape database displays the mode shapes of the tested specimen based on its shape and size. The placement of the sensors is determined based on the mode shapes, as shown in the following method:

[0054] Open the software, consult the operation manual according to the specimen's shape, find its corresponding number, select the number in the software interface, then select the material, and click the search button to display its first four vibration modes. Determine the sensor arrangement scheme based on the displayed vibration modes. The specimen vibration mode database is as follows: Figure 5 As shown.

[0055] This invention is not limited to the specific embodiments described above. Those skilled in the art can make various changes and modifications within the scope of the concept and spirit of this invention, and all such changes and modifications should fall within the protection scope of this invention.

Claims

1. A high-end machine tool mating surface contact characteristic testing device with triaxial excitation, characterized in that: The device comprises: a base (1), a first support (2), a second support (3), a vibrator (4), a vibrator fixing frame (5), an impedance head (6), a rope (7), a test piece (8), a pre-tightening bolt (9), a support bolt (10), a sensor, a signal acquisition system, and a computer; The first bracket (2) is fixed to the base (1) by bracket bolts (10); the second bracket (3) is fixed to the base (1) by bracket bolts (10); the exciter (4) is placed in the exciter fixing frame (5) to form an exciter assembly; the impedance head (6) is installed at the excitation end of the exciter (4) and forms an excitation system with the exciter assembly; the excitation system is suspended on the first bracket by a rope (7) passing through the lifting frame in the exciter assembly; the excitation system is suspended on the second bracket (3) by a rope (7); the specimen (8) is fixed to the boss of the base (1) by pre-tightening bolts (9); the acceleration sensor is fixed to the specimen (8) by glue; the output end of the acceleration sensor is connected to the computer through the signal acquisition system.

2. The high-end machine tool mating surface contact characteristic testing device with triaxial excitation according to claim 1, characterized in that: The first support (2) and the second support (3) are the support frames for the suspension exciter system. By changing the support suspended by the rope (7), the specimen (8) is excited in different directions.

3. The high-end machine tool mating surface contact characteristic testing device with triaxial excitation according to claim 1, characterized in that: There are two lifting frames on the vibrator fixing frame (5). By changing the rope (7) and passing it through different lifting frames, the specimen (8) is vibrated in different directions.

4. The high-end machine tool mating surface contact characteristic testing device with triaxial excitation according to claim 1, characterized in that: By adjusting the torque of the preload bolt (9) to adjust the load on the mating surface, experiments were conducted on the contact stiffness and contact damping of the mechanical mating surface. During the experiment, the experimental data was measured by the sensor and transmitted to the computer through the data acquisition system.

5. The high-end machine tool mating surface contact characteristic testing device with triaxial excitation according to claim 1, characterized in that: The computer has a mode shape database installed. The database stores the finite element simulation results of different specimens. The number and location of sensors are determined based on their mode shapes. Before the test, the mode shapes are queried in the specimen mode shape database according to the shape and material of the specimen being tested.

6. A method for testing the contact characteristics of a high-end machine tool mating surface using a device with triaxial excitation as described in any one of claims 1-5, characterized in that, During the test, the specimen (8) was first fixed to the boss of the base (1) by the pre-tightening bolt (9), and then the first bracket (2) and the second bracket (3) were installed. After that, the exciter (4) was placed in the exciter fixing frame (5) and the impedance head (7) was installed at the excitation end of the exciter (4). The sensor was pasted on the specimen (8), and then the sensor was connected to an external signal acquisition system to transmit the vibration signal of the joint surface to the computer. During the experiment, the load on the joint surface was changed by changing the torque of the pre-tightening bolt (9), and multiple sets of experimental data were extracted. The influence of the load on the joint surface on the contact stiffness and contact damping was obtained by using the modeling method of mechanical joint surface stiffness and damping.

7. The method for testing the contact characteristics of a high-end machine tool mating surface under three-dimensional excitation as described in claim 6, characterized in that, The contact between two rough surfaces can be simplified to the contact between a rigid plane and a rough surface, where the profile of the rough surface is described by a three-dimensional WM function, and a single micro-protrusion of the rough surface has the following relationship. （1）； （2）； （3）； （4）； In the formula: denoted as denoted as the normal deformation of the micro-protrusion; denoted as a, the contact area of ​​a single micro-protrusion; denoted as D, the fractal dimension; and denoted as G, the fractal roughness. D and G are parameters used in fractal theory to characterize the three-dimensional morphology of a surface. The contour of the bonding surface is obtained by a surface profilometer, and D and G are obtained by the power spectral density method. The spectral density is a size parameter; R represents the radius of curvature of a single micro-protrusion. It is the critical cross-sectional area at which the micro-convex body undergoes elastoplastic deformation; E represents the composite elastic modulus. , , , , These are the elastic modulus and Poisson's ratio of the two contacting materials, respectively. It is the critical cross-sectional area at which the micro-protrusion undergoes plastic deformation; The normal loads on a single micro-protrusion in the fully elastic, elastoplastic, and plastic stages are respectively expressed as: （5）； （6）； （7）； In the formula: The coefficients are related to material properties and fractal parameters of the interface; H is the hardness of the softer material. The normal contact stiffness of a single micro-protrusion is expressed as: （8）； Based on the MB fractal model, an expansion factor for the distribution domain of micro-contact point size is introduced, resulting in the distribution function of the contact point size for a micro-contact cross-sectional area as follows: （9） （10）； In the formula: The domain extension factor is obtained from formula 10; This indicates the maximum contact area of ​​the micro-protrusion. W is the normal load; In the fully elastic deformation region Elastic-plastic deformation region Integrating over the above, the total stiffness of the mating surface can be expressed as: （11）； Fixed interface contact damping analysis theory: Energy stored per cycle by a single micro-protrusion during contact deformation With dissipated energy Represented as: （12）； （13）； By integrating the periodically stored energy and dissipated energy in the fully elastic deformation region and the plastic deformation region, the elastic strain energy and plastic strain energy at the interface are obtained as follows: （14）； （15）； The total contact damping of the mating surface is expressed as: （16）； In the formula: M is the structural mass; K is the contact stiffness of the mating surface.

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