Method for relieving residual stress by using multi-level vibration stress relief platform

Abstract

The present invention provides a method for relieving residual stress by using a multi-level vibration stress relief platform, and aims to improve the residual stress relieving effect for metal structural parts having small sizes. The method for relieving the residual stress by using a multi-level vibration stress relief platform comprises: a numerical modal analysis process; a harmonic response analysis process; determination of mounting positions; determination of an excitation frequency of a multi-level vibration stress relief platform and the angle of an eccentric block of a speed adjustable motor; adjustment of a damping factor ζ and a damping ratio; and stress relief treatment on a metal structural part by the multi-level vibration stress relief platform. The present invention has the advantage of amplifying the excitation energy of a low-frequency vibration stress relief platform to improve the residual stress relieving effect of the vibration platform.

Description

Method of eliminating residual stress using multi-level vibration aging platform Technical Field

[0001] The present invention relates to the technical field of vibration aging, in particular to a method for eliminating residual stress by using a multi-level vibration aging platform. Technical Background

[0002] With the rapid development of micro-nano manufacturing technology, various small-sized metal structural parts are increasingly used in small precision equipment. How to eliminate the residual stress of small-sized metal structural parts is an important research topic in the field of mechanical manufacturing technology.

[0003] Vibration aging (VSA) is a widely used residual stress relief method in mechanical engineering. Cyclic loading is applied to metal components. When the sum of the internal residual stress and the added dynamic stress exceeds the material's yield point, plastic deformation occurs within the material, releasing the residual stress. Compared to natural and thermal aging, VSA offers advantages such as simple equipment, portability, and ease of on-site operation. It is an energy-efficient, environmentally friendly aging treatment method. Currently, VSA uses an adjustable-speed motor as the excitation device, typically with an excitation frequency of less than 200Hz, making it a low-frequency VSA technique. Since smaller metal components cannot be directly clamped to an adjustable-speed motor for VSA treatment, improvements are needed to develop a vibration platform capable of VSA treatment of smaller components. However, conventional low-frequency VSA platforms utilize a single, low-frequency vibration layer, introducing low excitation energy and resulting in poor residual stress relief.

[0004] Therefore, in order to improve the effect of eliminating residual stress and meet the clamping problem of small-sized metal structural parts, the present invention proposes a method for eliminating residual stress using a multi-level vibration aging platform, which further improves the excitation energy and thus improves the elimination rate of residual stress.

[0005] Summary of the Invention

[0006] In view of the limitation that the excitation energy is small when metal structural parts of smaller size are installed on the vibration platform for vibration aging treatment, the present invention proposes a method for eliminating residual stress using a multi-level vibration aging platform. The multi-level vibration aging platform includes a host computer system, a signal generator, a speed regulator, an adjustable speed motor, a first-level vibration platform, a second-level vibration platform, a G-type clamp, an air spring, an additional air chamber, an air inlet valve, an air outlet valve, a valve body controller, an elastic gasket, an acceleration sensor, a pad, a charge amplifier, a strain gauge, and a dynamic strain gauge; the G-type clamp fixes the adjustable speed motor on the first-level vibration platform; the elastic gasket is installed at the lower end of the node line of the first-level vibration platform; an air spring is installed between the second-level vibration platform and the first-level vibration platform; the air inlet of the air spring is connected to the air inlet valve; the air inlet valve and the air outlet valve are connected to the additional air chamber, the air inlet valve and the air outlet valve are connected to the valve body controller, and the valve body controller is connected to the valve body control module of the host computer system. connected; the metal structure is clamped and fixed on the secondary vibration platform, and a pad is set between the metal structure and the secondary vibration platform; the signal generator control module in the host computer system controls the signal generator to output a step-type excitation signal, which is input to the adjustable speed motor via the speed regulator to drive the adjustable speed motor to generate vibration; the strain gauge is pasted on the metal structure, the output end of the strain gauge is connected to the input end of the dynamic strain gauge, and the output end of the dynamic strain gauge is connected to the host computer system; the acceleration sensor is installed on the secondary vibration platform and the metal structure; the output end of the acceleration sensor is connected to the input end of the charge amplifier, the output end of the charge amplifier is connected to the input end of the oscilloscope, and the output end of the oscilloscope is connected to the host computer system.

[0007] The host computer system includes: signal generator control module, waveform and voltage display module, strain waveform acquisition module and peak strain extraction module, finite element numerical simulation software, and valve body control module;

[0008] Furthermore, the air springs are arranged on both sides of the peak symmetry axis of the displacement mode of the first-stage vibration platform using bolt connection, and according to the modal analysis results, it can be seen that the amplitudes of the air springs installed at the first-stage vibration platform are the same.

[0009] Furthermore, the upper computer system valve control module controls the air spring pressure and thus the spring coefficient through the valve controller. The upper ends of the air springs share a common air inlet to ensure that the four air springs have the same pressure and thus the same spring stiffness and damping. The pad is composed of an upper sleeve, a spring, and a lower sleeve. The upper end of the spring is mounted in the upper sleeve, the lower end of the spring is mounted in the lower sleeve, and the upper sleeve is embedded in the lower sleeve. The air spring is installed between the secondary vibration platform and the primary vibration platform, and the pad is installed between the metal structure and the secondary vibration platform. According to the dual-mass spring damping model, the air spring and the pad both serve to amplify the excitation energy. The dynamic strain gauge is a multi-channel strain gauge that displays strain waveforms in real time. The strain gauge is affixed to the peak residual stress of the metal structure, wherein the first strain gauge is affixed along the first principal stress direction of the metal structure, and the second strain gauge is affixed along the second principal stress direction of the metal structure. The elastic washer is installed on the nodal line of the first-order bending displacement vibration mode of the first-level vibration platform; according to the forced vibration model under harmonic excitation of the damped two-degree-of-freedom system, it can be seen that when the adjustable speed motor excites the first-level vibration platform, the excitation energy of the first-level vibration platform is amplified at multiple levels.

[0010] Furthermore, the present invention also proposes a method for eliminating residual stress using a multi-level vibration aging platform, comprising the following steps:

[0011] (1) Obtaining the natural frequency and displacement vibration mode: The finite element numerical simulation software is pre-installed in the host computer system. The finite element numerical simulation software is used to establish a three-dimensional finite element model of the first-level vibration platform, the second-level vibration platform, and the structural parts. The modal analysis of the first-level vibration platform, the second-level vibration platform, and the metal structural parts is performed to obtain the natural frequencies of the first-level vibration platform, the second-level vibration platform, and the metal structural parts and the displacement vibration modes of the first-level vibration platform, the second-level vibration platform, and the metal structural parts corresponding to the natural frequencies.

[0012] (2) Obtain the maximum dynamic stress of the surface vibrating at the natural frequency: Based on the numerical modal analysis, the natural frequencies of the first-order vibration platform, the second-order vibration platform, and the metal structure and the corresponding displacement modes are obtained for harmonic response analysis. When the first-order vibration platform vibrates at the natural frequency ω0 of the first-order bending vibration, the node line position of the first-order bending displacement mode of the first-order vibration platform and the position of the maximum dynamic stress on the surface of the second-order vibration platform are obtained;

[0013] (3) Determine the installation positions of the primary vibration platform, air spring, secondary vibration platform, pad, metal structure, acceleration sensor, and strain gauge: according to the results of numerical modal analysis and harmonic response analysis; place the elastic gasket on the node line of the first-order bending displacement mode of the primary vibration platform; the adjustable speed motor is fixed on both sides of the symmetry axis of the vibration peak of the first-order bending displacement mode of the primary vibration platform; the acceleration sensor is installed at the vibration peak position of the first-order bending displacement mode of the secondary vibration platform and the vibration peak position of the first-order bending vibration displacement mode of the metal structure; the distribution state of the residual stress of the metal structure is obtained by X-ray diffraction method, the strain gauge is pasted at the peak position of the residual stress of the metal structure, and the peak position of the residual stress of the metal structure is fixedly installed at the maximum dynamic stress on the upper surface of the secondary vibration platform; a pad is set between the metal structure and the secondary vibration platform; the pad is installed on both sides of the symmetry axis of the vibration peak of the first-order bending vibration displacement mode of the metal structure, and the metal structure is clamped on the secondary vibration platform using a G-type clamp;

[0014] (4) Determine the excitation frequency of the multi-level vibration aging platform and the angle of the eccentric block of the adjustable speed motor: fix the angle θ of the eccentric block of the adjustable speed motor, control the signal generator to output the step-type excitation signal through the signal generator control module of the host computer system, and obtain the secondary vibration platform under different voltages U of the step-type excitation signal in the waveform and voltage display module of the host computer system. i The acceleration level a during the vibration, each voltage peak U i , i=1, 2, ..., n; where n is a positive integer, corresponding to an excitation frequency ω i , and record the maximum value of the acceleration level a max and the corresponding excitation frequency ω n ; Adjust the eccentric block angle θ of the adjustable speed motor; control the signal generator output voltage value to U through the host system signal generator control module n , the excitation frequency is ω n The excitation signal is obtained in the waveform and voltage display module of the host computer system. The excitation frequency of the secondary vibration platform is ω when the adjustable speed motor has different eccentric block angles. n Under the acceleration level a, when the acceleration level a ≥ a 有效 When θ0 is set, the eccentric block angle θ0 of the adjustable speed motor is recorded; U0 is the voltage value output by the signal generator, ω is the excitation frequency of the secondary vibration platform of the multi-level vibration aging platform, and θ0 is the eccentric block angle of the adjustable speed motor;

[0015] (4.1) Open the signal generator control module of the host computer system, set the voltage peak and frequency peak of the signal generator input to the speed regulator, then create a step-by-step analog excitation signal and save it in the host computer system. Send the analog signal saved by the host computer system to the signal generator and save it, disconnect the host computer system and the signal generator, then input the excitation signal in the signal generator into the speed regulator, the speed regulator drives the adjustable speed motor to rotate, the adjustable speed motor generates an excitation force on the first vibration platform, and the air spring on the first vibration platform drives the second vibration platform to vibrate together. The acceleration sensor receives the vibration signals of the second vibration platform and the metal structure respectively, and converts them into voltage signals through the charge amplifier and displays the acceleration level of the second vibration platform and the metal structure and the corresponding frequency of the excitation signal in the waveform and voltage display module of the host computer system;

[0016] (4.2) The vibration signals collected by the acceleration sensor from the secondary vibration platform and the metal structure are converted into voltage signals through the charge amplifier. The conversion relationship between the acceleration level a of the metal structure and the secondary vibration platform and the voltage signal U is: The unit is m / s 2 , where the sensitivity of the acceleration sensor is β1, and the unit is pC / m·s -2 , the sensitivity coefficient of the charge amplifier input is β2, the unit is pC / Unit, and the amplification factor is S, the unit is Unit / V;

[0017] (4.3) Set the acceleration level of the metal structure: the acceleration level on the metal structure reaches the set critical threshold a 有效 When the critical threshold acceleration level a is exceeded 有效 The acceleration vibration level a is used as the effective acceleration vibration level for eliminating residual stress in the multi-level energy controllable vibration aging platform;

[0018] (5) Adjust the damping factor ζ and damping ratio The natural frequency of the first-order vibration system composed of metal structural parts and elastic pads is ω1 and the damping ratio is ζ1, where The natural frequency of the second-stage vibration system composed of the secondary vibration platform and the air spring is ω2, and the damping ratio is ζ2, where The mass ratio of the secondary vibration platform to the metal structure is μ, where μ = m2 / m1 and g = ω / ω1. The excitation frequency of the primary vibration platform is ω, and the natural frequency of the first-stage vibration system is ω1. x1 is the amplitude of the metal structure, x2 is the amplitude of the secondary vibration platform, X is the amplitude of the primary vibration platform, m1 is the mass of the metal structure, m2 is the mass of the secondary vibration platform, the elastic pad is equivalent to an elastic element with a stiffness of k1 and a damping element of c1, and the air spring is equivalent to an elastic element with a stiffness of k2 and a damping element of c2.

[0019] Establish the motion equation of the vibration system based on the momentum theorem

[0020] Performing Laplace transform on the equation of motion yields:

[0021] Simplifying formula (2) can eliminate X1(s) and obtain the ratio of the amplitude of the secondary vibration platform to the amplitude of the primary vibration platform, that is, the second-stage amplification factor α2 of the vibration aging platform

[0022] Simplifying formula (2) and eliminating X(s) yields the first-order magnification factor of the vibration aging platform:

[0023] Simplifying formula (2) can eliminate X2(s) and obtain the ratio of the metal structure and the amplitude of the first-level vibration platform, that is, the total magnification of the vibration aging platform α0

[0024] Let s = jw. According to the frequency characteristics of x1 to X, we can get the amplitude-frequency characteristics of the metal structure's amplitude x1 to the amplitude X of the first-level vibration platform, that is, the total magnification of the vibration aging platform α0.

[0025] ABCD is a coefficient defined for the convenience of calculation.

[0026] (6) Multi-level vibration aging platform aging treatment: When the eccentric block angle of the adjustable speed motor is θ0, the upper computer system signal generator control module controls the signal generator to output an excitation signal with an initial voltage value of U0 to perform fixed-frequency vibration aging treatment on the metal structure with an excitation frequency of ω, and the strain waveform acquisition module in the upper computer system obtains the strain waveform output of the metal structure collected by the dynamic strain gauge. When the strain waveform remains unchanged, the upper computer system valve body control module controls the air intake valve through the valve body controller to increase the elastic coefficient of the air spring, so that the acceleration vibration level a of the metal structure increases. After the acceleration vibration level a of the metal structure reaches a peak value, no more gas is introduced. When the strain waveform output of the metal structure collected by the dynamic strain gauge obtained by the strain waveform acquisition module in the upper computer system remains unchanged again, the power is cut off and the vibration aging treatment of the metal structure is stopped. The finite element numerical simulation software is ANSYS finite element software. The signal connections include those between the host system and the signal generator; between the signal generator and the speed regulator; between the speed regulator and the adjustable-speed motor; between the accelerometer and the charge amplifier; between the charge amplifier and the oscilloscope; between the oscilloscope and the host system; between the strain gauge and the dynamic strain gauge; between the dynamic strain gauge and the host system; between the air inlet and outlet and the valve controller; and between the valve controller and the host system. The power supply includes the power supply for the host system, signal generator, speed regulator, charge amplifier, and oscilloscope. The installation position of the elastic washer is determined to ensure that the primary vibration platform does not deviate from its original position when vibrating according to the first-order bending displacement mode, reduce energy loss during vibration of the primary vibration platform, and weaken the vibration effect of the primary vibration platform on the ground. The pad amplifies the vibration energy injected into the metal structure and causes the metal structure to vibrate according to the first-order bending displacement mode. The step-type excitation signal, the horizontal axis represents time, the vertical axis represents analog voltage, is in the shape of a step-up, and each voltage peak U i , i=1, 2, ..., n; where n is a positive integer, corresponding to an excitation frequency ω i , where U i The corresponding horizontal axis is the excitation time Δt; the eccentric block angle of the adjustable speed motor is 0°<θ≤180°.

[0027] The beneficial effects of the present invention are as follows:

[0028] The present invention adopts finite element numerical modal analysis to obtain the natural frequencies of each order and the corresponding displacement modes of each order of the first-level vibration platform, and through harmonic response analysis, elastic washers are placed in the areas with the smallest strain at both ends of the vibration platform's node line, so that the first-level vibration platform vibrates according to the first-order bending displacement mode, reducing the loss of vibration energy and weakening the vibration effect of the first-level vibration platform on the ground.

[0029] The present invention arranges an air spring with adjustable elastic coefficient and damping between the primary vibration platform and the secondary vibration platform, and changes the elastic stiffness of the air spring during the vibration process to improve the vibration aging treatment effect.

[0030] The present invention installs an air spring between the secondary vibration platform and the primary vibration platform, and installs a pad between the metal structure and the secondary vibration platform. According to the dual-mass spring damping model, the air spring and the elastic pad both have the effect of energy amplification, thereby improving the shortcoming of the low-frequency vibration aging platform with small excitation energy.

[0031] The present invention uses finite element numerical modal analysis to obtain the natural frequencies of each order of the structural parts and the displacement modes corresponding to each order of the natural frequencies. A pad is installed between the metal structural parts and the first-level vibration platform. The pad amplifies the vibration energy injected into the metal structural parts and allows the metal structural parts to vibrate according to the first-order bending displacement mode, thereby improving the effect of vibration aging.

[0032] The present invention fixes the metal structural part on the maximum dynamic stress position on the secondary vibration platform according to the residual stress distribution state of the metal structural part, thereby improving the effect of vibration aging.

[0033] When the multi-level vibration aging platform proposed by the present invention is used to perform vibration aging treatment on metal structural parts, it is controlled by the host computer system, which reduces the workload, improves the work efficiency and the intelligence level of the low-frequency vibration platform.

[0034] While retaining certain advantages of the original low-frequency vibration aging platform in eliminating residual stress, the present invention also proposes a method for eliminating residual stress using a multi-level vibration aging platform, which solves the defects that the low-frequency vibration aging platform cannot clamp small-sized metal structural parts and has poor residual stress elimination effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG1 is a schematic diagram of a multi-level vibration aging platform for eliminating residual stress using the platform according to the present invention.

[0036] FIG2 is a flow chart of a method for eliminating residual stress using the platform according to the present invention.

[0037] FIG3 is a schematic diagram of a multi-layer vibration aging platform and four air springs in the method of eliminating residual stress using the platform according to the present invention.

[0038] FIG4 is a schematic diagram of the natural frequency of the first-level vibration platform and the displacement mode shape corresponding to the natural frequency in the method of eliminating residual stress using the platform of the present invention.

[0039] FIG5 is a schematic diagram of the natural frequency of the secondary vibration platform and the displacement mode shape corresponding to the natural frequency in the method of eliminating residual stress using the platform of the present invention.

[0040] FIG6 is a schematic diagram of a forced vibration model of a two-degree-of-freedom system under harmonic excitation using the platform for eliminating residual stress according to the present invention. DETAILED DESCRIPTION

[0041] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0042] The contents described in the embodiments of this specification are merely an enumeration of the implementation forms of the inventive concept. The scope of protection of the present invention should not be regarded as limited to the specific forms described in the embodiments. The scope of protection of the present invention also extends to equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

[0043] With reference to the accompanying drawings, the method for eliminating residual stress using a multi-level vibration aging platform of the present invention is further described: FIG1 is a schematic diagram of a multi-level vibration aging platform; the multi-level vibration aging platform includes a host computer system 1, a signal generator, a speed regulator 2, an adjustable speed motor 3, a primary vibration platform 4, a secondary vibration platform 5, a G-type clamp, an air spring 6, an additional air chamber 7, an air inlet valve 8, an air outlet valve 9, a valve body controller 10, an elastic washer 11, an acceleration sensor 12, a pad 13, a charge amplifier 14, a strain gauge 15, a dynamic strain gauge 16, and an oscilloscope 17; the G-type clamp fixes the adjustable speed motor 3 on the primary vibration platform 4; the elastic washer 1 is installed at the lower end of the node line of the primary vibration platform; an air spring 6 is installed between the secondary vibration platform 5 and the primary vibration platform 4; the air inlet of the air spring 6 is connected to the air inlet valve 8; the air inlet valve 8 and the air outlet valve 9 are connected to the additional air chamber 7, the air inlet valve 8 and the air outlet valve 9 It is connected to the valve body controller 10, and the valve body controller 10 is connected to the valve body control module of the upper computer system 1; the metal structure 18 is clamped and fixed on the secondary vibration platform 5, and a pad 13 is set between the metal structure 18 and the secondary vibration platform 5; the signal generator 1 control module in the upper computer system 1 controls the signal generator 1 to output a step-type excitation signal, which is input to the adjustable speed motor 3 via the speed regulator 2 to drive the adjustable speed motor 3 to generate vibration; the strain gauge 15 is pasted on the metal structure 18, and the output end of the strain gauge 15 is connected to the input end of the dynamic strain gauge 16, and the output end of the dynamic strain gauge 16 is connected to the upper computer system 1; the acceleration sensor 12 is installed on the primary vibration platform 4 and the metal structure 18; the output end of the acceleration sensor 12 is connected to the input end of the charge amplifier 14, the output end of the charge amplifier 14 is connected to the input end of the oscilloscope 17, and the output end of the oscilloscope 17 is connected to the upper computer system 1. The host computer system includes: signal generator control module, waveform and voltage display module, strain waveform acquisition module and peak strain extraction module, finite element numerical simulation software, and valve body control module;

[0044] Furthermore, the air spring is arranged at both sides of the peak symmetry axis II of the displacement mode of the first-level vibration platform using bolt connection as shown in Figure 3, and according to the modal analysis results, it can be seen that the amplitude of the air spring installed at the position of the first-level vibration platform is the same.

[0045] Furthermore, as shown in Figure 4, which is a schematic diagram of the natural frequency of the first-level vibration platform and the displacement vibration mode corresponding to the natural frequency, the elastic washer is placed on the node line I of the first-order bending displacement vibration mode of the first-level vibration platform, and the air spring is arranged on both sides of the peak symmetry axis II of the displacement vibration mode of the first-level vibration platform, and ensure that the distance x1 from the air spring to the peak symmetry axis is less than the distance x2 between the elastic washer and the peak symmetry axis.

[0046] Furthermore, Figure 5 shows the natural frequency of the secondary vibration platform and the corresponding displacement mode shape. The upper end of the air spring is fixed on both sides of the displacement peak symmetry axis IV of the secondary vibration platform, and the distance from the air spring to the center of the displacement peak symmetry axis is x3.

[0047] Furthermore, the upper computer system valve control module controls the air spring pressure and thus the spring coefficient via the valve body controller. The upper ends of the air springs share a common air inlet to ensure that the four air springs have the same pressure, thereby ensuring the same spring stiffness and damping. The pad consists of an upper sleeve, a spring, and a lower sleeve. The upper end of the spring is mounted in the upper sleeve, the lower end of the spring is mounted in the lower sleeve, and the upper sleeve is embedded in the lower sleeve. The air spring is installed between the secondary vibration platform and the primary vibration platform, and the pad is installed between the metal structure and the secondary vibration platform. According to the dual-mass spring-damping model shown in Figure 6, the air spring and the pad both serve to amplify the excitation energy. The dynamic strain gauge is a multi-channel strain gauge that displays strain waveforms in real time. The strain gauge is affixed to the peak residual stress of the metal structure, with the first strain gauge affixed along the direction of the first principal stress of the metal structure, and the second strain gauge affixed along the direction of the second principal stress of the metal structure. The elastic washer is installed on the nodal line I of the first-order bending displacement mode of the first-level vibration platform; according to the forced vibration model under harmonic excitation of the damped two-degree-of-freedom system, it can be seen that when the adjustable speed motor excites the first-level vibration platform, the excitation energy of the first-level vibration platform is amplified at multiple levels.

[0048] Furthermore, FIG2 is a flow chart of the present invention using a multi-level vibration aging platform to eliminate residual stress. The present invention also proposes a method for eliminating residual stress using a multi-level vibration aging platform, comprising the following steps:

[0049] (1) Obtaining the natural frequency and displacement vibration mode: The finite element numerical simulation software is pre-installed in the host computer system. The finite element numerical simulation software is used to establish a three-dimensional finite element model of the first-level vibration platform, the second-level vibration platform, and the structural parts. The modal analysis of the first-level vibration platform, the second-level vibration platform, and the metal structural parts is performed to obtain the natural frequencies of the first-level vibration platform, the second-level vibration platform, and the metal structural parts and the displacement vibration modes of the first-level vibration platform, the second-level vibration platform, and the metal structural parts corresponding to the natural frequencies.

[0050] (2) Obtain the maximum dynamic stress of the surface vibrating at the natural frequency: Based on the numerical modal analysis, the natural frequencies of the first-order vibration platform, the second-order vibration platform, and the metal structure and the corresponding displacement modes are obtained for harmonic response analysis. When the first-order vibration platform vibrates at the natural frequency ω0 of the first-order bending vibration, the node line position of the first-order bending displacement mode of the first-order vibration platform and the position of the maximum dynamic stress on the surface of the second-order vibration platform are obtained;

[0051] (3) Determine the installation positions of the primary vibration platform, air spring, secondary vibration platform, pad, metal structure, acceleration sensor, and strain gauge: according to the results of numerical modal analysis and harmonic response analysis; place the elastic gasket on the node line I of the first-order bending displacement mode of the primary vibration platform; the adjustable speed motor is fixed on both sides of the symmetry axis of the vibration peak of the first-order bending displacement mode of the primary vibration platform; the acceleration sensor is installed at the vibration peak position of the first-order bending displacement mode of the secondary vibration platform and the vibration peak position of the first-order bending vibration displacement mode of the metal structure; the distribution state of the residual stress of the metal structure is obtained by X-ray diffraction method, the strain gauge is pasted at the peak position of the residual stress of the metal structure, and the peak position of the residual stress of the metal structure is fixedly installed at the maximum dynamic stress on the upper surface of the secondary vibration platform; a pad is set between the metal structure and the secondary vibration platform; the pad is installed at IV on both sides of the symmetry axis of the vibration peak of the first-order bending vibration displacement mode of the metal structure, and the metal structure is clamped on the secondary vibration platform using a G-type clamp;

[0052] (4) Determine the excitation frequency of the multi-level vibration aging platform and the angle of the eccentric block of the adjustable speed motor: fix the angle θ of the eccentric block of the adjustable speed motor, control the signal generator to output the step-type excitation signal through the signal generator control module of the host computer system, and obtain the secondary vibration platform under different voltages U of the step-type excitation signal in the waveform and voltage display module of the host computer system. i The acceleration level a during the vibration, each voltage peak U i , i=1, 2, ..., n; where n is a positive integer, corresponding to an excitation frequency ω i , and record the maximum value of the acceleration level a max and the corresponding excitation frequency ω n ; Adjust the eccentric block angle θ of the adjustable speed motor; control the signal generator output voltage value to U through the host system signal generator control module n , the excitation frequency is ω n The excitation signal is obtained in the waveform and voltage display module of the host computer system. The excitation frequency of the secondary vibration platform is ω when the adjustable speed motor has different eccentric block angles. n Under the acceleration level a, when the acceleration level a ≥ a 有效 When θ0 is set, the eccentric block angle θ0 of the adjustable speed motor is recorded; U0 is the voltage value output by the signal generator, ω is the excitation frequency of the secondary vibration platform of the multi-level vibration aging platform, and θ0 is the eccentric block angle of the adjustable speed motor;

[0053] (4.1) Open the signal generator control module of the host computer system, set the voltage peak and frequency peak of the signal generator input to the speed regulator, then create a step-by-step analog excitation signal and save it in the host computer system. Send the analog signal saved by the host computer system to the signal generator and save it, disconnect the host computer system and the signal generator, then input the excitation signal in the signal generator into the speed regulator, the speed regulator drives the adjustable speed motor to rotate, the adjustable speed motor generates an excitation force on the first vibration platform, and the air spring on the first vibration platform drives the second vibration platform to vibrate together. The acceleration sensor receives the vibration signals of the second vibration platform and the metal structure respectively, and converts them into voltage signals through the charge amplifier and displays the acceleration level of the second vibration platform and the metal structure and the corresponding frequency of the excitation signal in the waveform and voltage display module of the host computer system;

[0054] (4.2) The vibration signals collected by the acceleration sensor from the secondary vibration platform and the metal structure are converted into voltage signals through the charge amplifier. The conversion relationship between the acceleration level a of the metal structure and the secondary vibration platform and the voltage signal U is: The unit is m / s 2 , where the sensitivity of the acceleration sensor is β1, and the unit is pC / m·s -2 , the sensitivity coefficient of the charge amplifier input is β2, the unit is pC / Unit, and the amplification factor is S, the unit is Unit / V;

[0055] (4.3) Set the acceleration level of the metal structure: the acceleration level on the metal structure reaches the set critical threshold a 有效 When the critical threshold acceleration level a is exceeded 有效 The acceleration vibration level a is used as the effective acceleration vibration level for eliminating residual stress in the multi-level energy controllable vibration aging platform;

[0056] (5) Adjust the damping factor ζ and damping ratio The natural frequency of the first-order vibration system composed of metal structural parts and elastic pads is ω1 and the damping ratio is ζ1, where The natural frequency of the second-stage vibration system composed of the secondary vibration platform and the air spring is ω2, and the damping ratio is ζ2, where The mass ratio of the secondary vibration platform to the metal structure is μ, where μ = m2 / m1 and g = ω / ω1. The excitation frequency of the primary vibration platform is ω, and the natural frequency of the first-stage vibration system is ω1. x1 is the amplitude of the metal structure, x2 is the amplitude of the secondary vibration platform, X is the amplitude of the primary vibration platform, m1 is the mass of the metal structure, m2 is the mass of the secondary vibration platform, the elastic pad is equivalent to an elastic element with a stiffness of k1 and a damping element c1, and the air spring is equivalent to an elastic element with a stiffness of k2 and a damping element c2.

[0057] Establish the motion equation of the vibration system based on the momentum theorem

[0058] Performing Laplace transform on the equation of motion yields:

[0059] Simplifying formula (2) can eliminate X1(s) and obtain the ratio of the amplitude of the secondary vibration platform to the amplitude of the primary vibration platform, that is, the second-stage amplification factor α2 of the vibration aging platform

[0060] Simplifying formula (2) and eliminating X(s) yields the first-order magnification factor of the vibration aging platform:

[0061] Simplifying formula (2) can eliminate X2(s) and obtain the ratio of the metal structure and the amplitude of the first-level vibration platform, that is, the total magnification of the vibration aging platform α0

[0062] Let s = jw. According to the frequency characteristics of x1 to X, we can get the amplitude-frequency characteristics of the metal structure's amplitude x1 to the amplitude X of the first-level vibration platform, that is, the total magnification of the vibration aging platform α0.

[0063] ABCD is a coefficient defined for the convenience of calculation.

[0064] (6) Multi-level vibration aging platform aging treatment: When the eccentric block angle of the adjustable speed motor is θ0, the upper computer system signal generator control module controls the signal generator to output an excitation signal with an initial voltage value of U0 to perform fixed-frequency vibration aging treatment on the metal structure with an excitation frequency of ω, and the strain waveform acquisition module in the upper computer system obtains the strain waveform output of the metal structure collected by the dynamic strain gauge. When the strain waveform remains unchanged, the upper computer system valve body control module controls the air intake valve through the valve body controller to increase the elastic coefficient of the air spring, so that the acceleration vibration level a of the metal structure increases. After the acceleration vibration level a of the metal structure reaches a peak value, no more gas is introduced. When the strain waveform output of the metal structure collected by the dynamic strain gauge obtained by the strain waveform acquisition module in the upper computer system remains unchanged again, the power is cut off and the vibration aging treatment of the metal structure is stopped. The finite element numerical simulation software is ANSYS finite element software. The signal connections include those between the host system and the signal generator; between the signal generator and the speed regulator; between the speed regulator and the adjustable-speed motor; between the accelerometer and the charge amplifier; between the charge amplifier and the oscilloscope; between the oscilloscope and the host system; between the strain gauge and the dynamic strain gauge; between the dynamic strain gauge and the host system; between the air inlet and outlet and the valve controller; and between the valve controller and the host system. The power supply includes the power supply for the host system, signal generator, speed regulator, charge amplifier, and oscilloscope. The installation position of the elastic washer is determined to ensure that the primary vibration platform does not deviate from its original position when vibrating according to the first-order bending displacement mode, reduce energy loss during vibration of the primary vibration platform, and weaken the vibration effect of the primary vibration platform on the ground. The pad amplifies the vibration energy injected into the metal structure and causes the metal structure to vibrate according to the first-order bending displacement mode. The step-type excitation signal, the horizontal axis represents time, the vertical axis represents analog voltage, is in the shape of a step-up, and each voltage peak U i , i=1, 2, ..., n; where n is a positive integer, corresponding to an excitation frequency ω i , where U i The corresponding horizontal axis is the excitation time Δt; the eccentric block angle of the adjustable speed motor is 0°<θ≤180°.

Claims

1. A method for eliminating residual stress using a multi-level vibration aging platform, the multi-level vibration aging platform comprising: The multi-level vibration aging platform comprises a host computer system (1), a signal generator, a speed regulator (2), an adjustable speed motor (3), a primary vibration platform (4), a secondary vibration platform (5), a G-type clamp, an air spring (6), an additional air chamber (7), an air inlet valve (8), an air outlet valve (9), a valve body controller (10), an elastic gasket (11), an acceleration sensor (12), a cushion block (13), a charge amplifier (14), a strain gauge (15), a dynamic strain gauge (16), and an oscilloscope (17); the G-type The adjustable speed motor (3) is fixed to the primary vibration platform (4) by a clamp; the elastic gasket (11) is installed at the lower end of the node line of the primary vibration platform (4); an air spring (6) is installed between the secondary vibration platform (5) and the primary vibration platform (4); the air inlet of the air spring (6) is connected to the air inlet valve (8); the air inlet valve (8) and the air outlet valve (9) are connected to the additional air chamber (7), the air inlet valve (8) and the air outlet valve (9) are connected to the valve body controller (10), and the valve body controller (10) is connected to the The host computer system (1) is connected to the valve body control module; the metal structure (18) is clamped and fixed on the secondary vibration platform (5), and a cushion block (13) is arranged between the metal structure (18) and the secondary vibration platform (5); the signal generator (1) control module in the host computer system (1) controls the signal generator (1) to output a step-type excitation signal which is input to the adjustable speed motor (3) via the speed regulator (2), thereby driving the adjustable speed motor (3) to generate vibration; the strain gauge (15) is pasted on the metal structure (18) , the output end of the strain gauge (15) is connected to the input end of the dynamic strain gauge (16), and the output end of the dynamic strain gauge (16) is connected to the host computer system (1); the acceleration sensor (12) is installed on the primary vibration platform (4) and the metal structure (18); the output end of the acceleration sensor (12) is connected to the input end of the charge amplifier (14), the output end of the charge amplifier (14) is connected to the input end of the oscilloscope (17), and the output end of the oscilloscope (17) is connected to the host computer system (1); Characterized in that the method of eliminating residual stress using a multi-level vibration aging platform comprises the following steps: (1) Obtaining natural frequencies and displacement vibration modes: The finite element numerical simulation software is pre-installed in the host computer system. The finite element numerical simulation software is used to establish a three-dimensional finite element model of the primary vibration platform, the secondary vibration platform, and the metal structure. The modal analysis function of the finite element numerical simulation software is used to analyze the primary vibration platform, the secondary vibration platform, and the metal structure to obtain the natural frequencies of the primary vibration platform, the secondary vibration platform, and the metal structure, and the displacement vibration modes of the respective orders corresponding to the natural frequencies of the respective orders. (2) Obtain the maximum dynamic stress of the surface vibrating at the natural frequency: According to the modal analysis function of the finite element numerical simulation software, the modal stress of each order of the primary vibration platform, the secondary vibration platform, and the metal structure is obtained. The harmonic response analysis is performed with the frequency and the corresponding displacement modes of each order, and the node line position of the first-order bending displacement mode of the first-order vibration platform and the maximum dynamic stress position on the upper surface of the second-order vibration platform are obtained when the first-order vibration platform vibrates at the natural frequency ω0 of the first-order bending vibration; (3) Determine the installation positions of the primary vibration platform, air spring, secondary vibration platform, pad, metal structure, acceleration sensor, and strain gauge: According to the results of numerical modal analysis and harmonic response analysis; place the elastic gasket on the node line of the first-order bending displacement mode of the primary vibration platform; the adjustable speed motor is fixed at the vibration peak position of the first-order bending displacement mode of the primary vibration platform; the acceleration sensor is installed at the vibration peak position of the first-order bending displacement mode of the secondary vibration platform and at the vibration peak position of the first-order bending vibration displacement mode of the metal structure; the distribution state of the residual stress of the metal structure is obtained by X-ray diffraction method, the strain gauge is pasted at the peak position of the residual stress of the metal structure, and the peak position of the residual stress of the metal structure is fixedly installed at the maximum dynamic stress on the upper surface of the secondary vibration platform; a pad is set between the metal structure and the secondary vibration platform; the pad is installed at the vibration peak position of the first-order bending vibration displacement mode of the metal structure, and the metal structure is clamped on the secondary vibration platform using a G-type clamp; (4) Determine the excitation frequency of the multi-level vibration aging platform and the angle of the eccentric block of the adjustable speed motor: fix the angle θ of the eccentric block of the adjustable speed motor, control the signal generator to output a step-type excitation signal through the signal generator control module of the host computer system, and obtain the waveform and voltage display module of the host computer system under different voltages U of the step-type excitation signal. i The acceleration level a during the vibration, each voltage peak U i , i = 1, 2, ..., n; where n is a positive integer, corresponding to an excitation frequency ω i , and record the maximum value of the acceleration level a max and the corresponding excitation frequency ω n ; Adjust the eccentric block angle θ of the adjustable speed motor; control the signal generator output voltage value to U through the host computer system signal generator control module n , the excitation frequency is ω n The excitation signal is obtained in the waveform and voltage display module of the host computer system. The excitation frequency of the secondary vibration platform is ω when the adjustable speed motor has different eccentric block angles. n Under the acceleration level a, when the acceleration level a ≥ a 有效 When the eccentric block angle θ0 of the adjustable speed motor is recorded; U0 is the voltage value output by the signal generator, ω is the excitation frequency of the secondary vibration platform of the multi-level vibration aging platform, and θ0 is the eccentric block angle of the adjustable speed motor; the method for adjusting the signal generator by the host computer system includes the following steps: (4.1) Open the signal generator control module of the host computer system, set the voltage peak value and frequency peak value of the signal generator input to the speed regulator, then create a step-by-step simulation excitation signal and save it in the host computer system. system; sending the analog signal saved in the host computer system to the signal generator and saving it, disconnecting the host computer system and the signal generator, and then inputting the excitation signal in the signal generator into the speed regulator, the speed regulator drives the adjustable speed motor to rotate, the adjustable speed motor generates an excitation force on the primary vibration platform, the air spring on the primary vibration platform drives the secondary vibration platform to vibrate together, the acceleration sensor receives the vibration signals of the secondary vibration platform and the metal structure respectively, and converts them into voltage signals through the charge amplifier, and displays the acceleration vibration level of the secondary vibration platform and the metal structure and the frequency of the corresponding excitation signal in the waveform and voltage display module of the host computer system; (4.2) The vibration signals collected by the acceleration sensor from the secondary vibration platform and the metal structure are converted into voltage signals through the charge amplifier. The conversion relationship between the acceleration level a of the metal structure and the secondary vibration platform and the voltage signal U is: The unit is m / s 2 , where the sensitivity of the acceleration sensor is β1, and the unit is pC / m·s -2 , the sensitivity coefficient of the charge amplifier input is β2, the unit is pC / Unit, and the amplification factor is S, the unit is Unit / V; (4.3) Set the acceleration level of the metal structure: The acceleration level on the metal structure reaches the set critical threshold a 有效 When the critical threshold acceleration level a is exceeded 有效 The acceleration vibration level a is used as the effective acceleration vibration level for eliminating residual stress in the multi-level energy controllable vibration aging platform; (5) Adjust the damping factor ζ and damping ratio (6) Multi-level vibration aging platform aging treatment: When the eccentric block angle of the adjustable speed motor is θ0, the host computer system signal generator control module controls the signal generator to output an excitation signal with an initial voltage value of U0 to perform fixed-frequency vibration aging treatment on the metal structure with an excitation frequency of ω. The strain waveform acquisition module in the host computer system acquires the strain waveform output by the metal structure collected by the dynamic strain gauge. When the strain waveform remains unchanged, the valve body control module of the host computer system controls the air input of the intake valve through the valve body controller to increase the elastic coefficient of the air spring, so that the acceleration vibration level a of the metal structure increases. After the acceleration vibration level a of the metal structure reaches a peak value, no more gas is introduced. When the strain waveform acquisition module in the host computer system acquires the strain waveform output by the metal structure collected by the dynamic strain gauge and remains unchanged again, the power is cut off to stop the vibration aging treatment of the metal structure.

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