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 struct

Description

To address the limitation of insufficient excitation energy when the small-sized metal structural component is mounted on a vibratory stress relief platform for vibratory stress relief treatment, the present invention proposes a method for eliminating residual stress by employing a multi-level vibratory stress relief platform, the multilevel vibratory stress relief platform comprising a host computer system, a signal generator, a speed controller, an adjustable-speed motor, a primary vibration platform, a secondary vibration platform, a multitude of G-clamps, a multitude of air springs, an additional air chamber, an intake valve, an exhaust valve, a valve body controller, a multitude of elastic gaskets, a multitude of acceleration sensors, a multitude of pads, a charge amplifier, a strain gauge, a dynamic strain indicator, and an oscilloscope; the adjustable-speed motor is connected to the primary vibration platform by the multitude of the G-clamps; each elastic gasket is installed at a lower end of the primary vibration platform; each air spring is installed between the secondary vibration platform and the primary vibration platform; an air intake of the air spring is connected to the intake valve; the intake valve and the exhaust valve are connected to the additional air chamber, and both the intake valve and the exhaust valve are connected to the valve body controller, and the valve body controller is connected to a valve body control module of the host computer system; a metal structural component is clamped and fixed on the secondary vibration platform, with the multitude of the pads placed between the metal structural component and the secondary vibration platform; a signal generator control module within the host computer system controlling the signal generator to output a step-like excitation signal, feeding through the speed controller to the adjustable-speed motor, driving the adjustable-speed motor to vibrate; the strain gauge is affixed to the metal structural component, with an output end of the strain gauge connected to an input end of the dynamic strain indicator, and the output end of the dynamic strain indicator is connected to the host computer system; the acceleration sensor is installed on both the primary vibration platform and the metal structural component; the output end of the acceleration sensor connected to the input end of the charge amplifier, and the output end of the charge amplifier is connected to the input end of the oscilloscope, with the output end of the oscilloscope connected to the host computer system; The host computer system comprises: a signal generator control module, a waveform and voltage display module, a strain waveform acquisition module and a peak strain extraction module, a finite element numerical simulation software, and a valve body control module. Further, the multitude of the air springs are arranged on both sides of a peak symmetric axis of displacement mode shape of the primary vibration platform by using bolt connections, and according to the results of the modal analysis, the multitude of the air springs installed at the position where the amplitude is the same as that of the primary vibration platform. Further, the valve body control module of the host computer system controls an air pressure of the multitude of the air springs, and thereby controls an air spring's elastic coefficient, through the valve body controller by managing the intake valve and the exhaust valve. The upper ends of the multitude of the air springs are collectively connected to an air inlet to ensure that the air pressure, and consequently the elastic stiffness and damping, are the same for the four air springs. Each pad consist of an upper sleeve, a spring, and a lower sleeve, with the upper end of the spring installed in the upper sleeve and the lower end of the spring installed in the lower sleeve, and the upper sleeve being embedded in the lower sleeve. The multitude of the air springs is installed between the secondary vibration platform and the primary vibration platform, and the multitude of the pads is installed between the metal structural component and the secondary vibration platform. According to the dual-mass spring-damper model, both the multitude of the air springs and pads serve to amplify the excitation energy. The dynamic strain indicator is a multi-channel strain gauge that displays strain waveforms in real-time. The strain gauge is attached to the positions of peak residual stress on the metal structural components; with the first strain gauge attached along the first principal stress direction of the metal structural component and the second strain gauge attached along the second principal stress direction. The multitude of the elastic gaskets is installed on the nodal lines of the first-stage bending displacement vibration mode shape of the primary vibration platform; according to the forced vibration model of a damped two-degree-of-freedom system under the harmonic excitation, when the adjustable-speed motor excites the primary’ vibration platform, the excitation energy of the primary' vibration platform is multi-level amplified. Further, the present invention discloses a method for eliminating residual stress by employing a multi-level vibratory stress relief platform, comprising the following steps: step (1): obtaining a multitude of natural frequencies and a multitude of displacement mode shapes: pre-installing a finite element numerical simulation software in the host computer system; using the finite element numerical simulation software to establish a three-dimensional finite element model of the primary vibration platform, secondary vibration platform, and the metal structural component; using a modal analysis capability of the finite element numerical simulation software to analyze the primary and secondary vibration platforms; and the metal structural component to obtain the multitude of the natural frequencies of each stage for the primary vibration platform, secondary vibration platform and the metal structural component, along with the multitude of the corresponding displacement mode shapes for each stage; step (2): acquiring a maximum dynamic surface stress at the natural frequency of a vibratory stress relief treatment: utilizing the modal analysis capability of the finite element numerical simulation software to analyze the multitude of the natural frequencies and the multitude of the corresponding displacement mode shapes of the primary vibration platform, the secondary vibration platform and the metal structural component; analyzing a harmonic response of the multitude of the natural frequencies and the multitude of the corresponding displacement mode shapes of the primary vibration platform, the secondary vibration platform and the metal structural component to determine a nodal line of a first-stage bending displacement mode of the primary vibration platform and obtaining a maximum dynamic stress position of an upper surface of the secondary vibration platform satisfying the primary vibration platform vibrating at the natural frequency co 0 of the first-stage bending vibration; step (3): determining a multitude of installation positions for the primary vibration platform, the multitude of the air springs, the secondary vibration platform, the multitude of the pads, the metal structural component, the acceleration sensor, and the strain gauge: placing the multitude of the elastic gaskets on the nodal line of the first-stage bending displacement mode shape of the primary vibration platform on the basis of the result of the modal analysis and a harmonic response analysis; securing the adjustable-speed motor on both sides of a peak symmetric axis of the first-stage bending displacement mode shape of the primary vibration platform; installing each acceleration sensor at the vibration peak position of the first-stage bending displacement mode shape of the secondary- vibration platform, and the metal structural component; employing a X-ray diffraction to ascertain a residual stress distribution in the metal structural component and adhering the strain gauge to a peak residual stress position; aligning these peak residual stress position with the maximum dynamic stress position on the upper surface of the secondary vibration platform; inserting the multitude of the pads between the metal structural component and the secondary-vibration platform on both sides of the peak symmetric axis of the first-stage bending displacement mode shape, and clamping the metal structural component onto the secondary vibration platform using the multitude of the G-clamps; step (4): determining an excitation frequency and an angle of an eccentric block of the adjustable-speed motor for the multi-level vibratory stress relief platform: fixing the angle of the eccentric block 9 ; controlling the signal generator to output the step-like excitation signal through the signal generator control module in the host computer system; obtaining an acceleration amplitude of the secondary vibration platform under the step-like excitation signal at a different voltage in a waveform and voltage display module of the host computer system for different voltage peak value U1, i=l,2,...,n; where n being a positive integer, corresponding to the excitation frequency co t, recording a maximum acceleration amplitude amax, and the corresponding excitation frequency con ; adjusting the angle of the eccentric block 9 of the adjustable-speed motor; controlling the signal generator control module in the host computer system to output the excitation signal with voltage value Un, and excitation frequency on ; obtaining the acceleration amplitude level a of the secondary- vibration platform at the different angle of the eccentric block of the adjustable-speed motor at the excitation frequency con , and recording the angle of the eccentric block 0O satisfying the acceleration amplitude level where Uo being a voltage output by the signal generator, CO being the excitation frequency of the secondary vibration platform of the multi-level vibratory stress relief platform, and 0O being the angle of the eccentric block of the adjustable-speed motor; adjusting the signal generator in the host computer system through the following steps; step (4.1): activating the signal generator control module of the host computer system to set the voltage and frequency peak value of the signal input to the speed controller; creating a step-like simulated excitation signal and saving the step-like simulated excitation signal in the host computer system; transmitting and saving the step-like simulated excitation signal to the signal generator; disconnecting the host computer system from the signal generator; inputting the step-like simulated excitation signal into the speed controller to drive the adjustable-speed motor, the adjustable-speed motor generating an excitation force on the primary vibration platform; actuating the secondary vibration platform, inducing synchronized vibration of the air spring on the primary vibration platform, with the acceleration sensor receiving vibration signal from both the secondary vibration platform and the metal structural component; converting the signal through the charge amplifier into a voltage signal; displaying the acceleration amplitude level of the secondary vibration platform and the metal structural component, along with the frequency of the corresponding excitation signal in the waveform and voltage display module of the host computer system; step (4.2): converting the vibration signal collected by the acceleration sensor from the secondary vibration platform and the metal structural component into the voltage signal via a charge amplifier; the conversion relationship between the acceleration amplitude level of the metal structural component and the secondary vibration S x B 2 platform and the voltage signal being a =---— x U, with units of m / s where A being a sensitivity of the acceleration sensor, with units of pC / m-s 2, / ?2 being a sensitivity coefficient at the input end of the charge amplifier, with units of pC / Unit, and S being a amplification factor with units of Unit / V; step (4.3): setting the acceleration amplitude level for the metal structural component: when the acceleration amplitude level on the metal structural component reaches the predetermined critical threshold , the acceleration amplitude level exceeding the critical threshold Geff is utilized as an effective acceleration amplitude level a for a multi-level energy-controllable vibratory stress relief platform to eliminate residual stress; step (5): adjusting a damping factor and damping ratio q : the metal structural component and the multitude of the pads constitute a primary vibration system with the natural frequency of ©j and the damping ratio of Q, where CDj = „ C, Q = —secondary vibration platform, in conjunction with the multitude of 2^ / klm] the air springs, forms a secondary vibration system with the natural frequency of © 2 and the damping ratio of 2, where ©2 = and <^2 =—---■ A mass ratio of V m2 the secondary vibration platform to the metal structural component is p , where p = m2 / nt], g = © / ©j. The excitation frequency of the primary vibration platform is CO, and the natural frequency of the primary' vibration system is © j . x j is the amplitude of the metal structural component, x 2 is the amplitude of the secondary vibration platform, X is the amplitude of the primary vibration platform, m, is the mass of the metal structural component, m, is the mass of the secondary vibration platform, the multitude of the pads is equivalent to an elastic element with a stiffness of kj and a damping element Cj, the multitude of the air springs are equivalent to the elastic element with a stiffness of k2 and the damping element c2. Establish a equation of motion for the vibration system in accordance with a momentum theorem: nijXj + CjXj + kjX] C]X2 kjX2 = 0 <m2x2 +(cj +c2)x2 +(kj +k2)x2 (1) -CjXj - kjXj = c2X + k,X Applying the Laplace transform to the equation of motion yields: (nijS2 + c]s + k1)X] (s)-(c1s + k])X2(s) = 0 ' (2) ^m2s2 +(C] +c2)s + kj +k2JX2(s)^(c1s + k1)X1 (s) = (c2s + k2)X(s) Simplifying the equation of motion (2) by eliminating X] (s), yields the ratio of the amplitude of the secondary vibration platform to the amplitude of the primary vibration platform, that is, the amplification factor a 2 of the second stage of the vibratory stress relief platform. X2(s) (c2s + k2)(m1S2 + C1s + kj) a2 = = ----;---------------------------------------------- (3 ) X(s) I m2s2 + (cj + c2) s + kj + k2 J(m,s2 + c,s + k, )-(c,s + k,) Simplifying the equation of motion (2) by eliminating X(s) yields the amplification factor a, of the first-stage of the vibratory stress relief platform. X,(s) (0,8 + ^)(03 + ^) «1 1 W 2-----(4) X(s) ^c2s + k2)lm,s +c1s + k1) Simplifying the equation of motion (2) by eliminating X2(s) yields the ratio of the amplitude of the metal structural component to the amplitude of the primary vibration platform, that is the total amplification factor a0 of the vibratory stress relief platform. ao = Xi(s) =______________(^s + kj^s + k,)______________ X(s) |^m2s2 + (c, + c2)s + k, +k2^m,s2 + c1s + k1)-(c,s + k1)2 Given s=jw, based on the frequency response of x, to X, an amplitude frequency characteristic of the metal structural component x, relative to the primary’ vibration platform X can be determined, which corresponds to the total amplification factor a0 of the vibratory stress relief platform. a0(g’ ^1’ ^1’ f) = ^W? A2 +B2 C2 +D2 (6) A = f2-4^2fg2 B=2f (^2 + y)g C = g4- d + f^ + i + ^f g2+f (7) D = 2fg(52+^f)-2k +   +y)g5 In J Where A, B, C, D are coefficients defined for simplifying calculations. step (6): eliminating residual stress by means of employing the multi-level vibratory stress relief platform: controlling a signal generator via a signal generator control module of the host computer system to output the excitation signal with an initial voltage excitation signal Uo satisfying the angle of the eccentric block 0O of the adjustable speed motor; conducting a fixed-frequency vibratory stress relief on the metal structural component at the excitation frequency ®; collecting an unchanged strain waveform recorded by the dynamic strain indicator of the metal structural component using a strain waveform acquisition module in the host computer system; adjusting the intake valve via the valve body control module of the host computer system; increasing the acceleration vibration level a of the metal structural component by introducing an air to increase an air spring's elastic coefficient; continuing to introduce the air at the acceleration vibration level a reaching a peak; stopping the gas input at the acceleration vibration level a reaching a peak; collecting an unchanged strain waveform again recorded by the dynamic strain indicator using the strain waveform acquisition module: cutting off the power supply; and terminating the vibratory stress relief treatment of the metal structural component; the finite element numerical simulation software referred to is ANSYS finite element software. The signal connections include a signal line between the host computer system and the signal generator; the signal line between the signal generator and the speed controller; the signal line between the speed controller and the adjustable-speed motor; the signal line between the acceleration sensor and the charge amplifier; the signal line between the charge amplifier and the oscilloscope; the signal line between the oscilloscope and the host computer system; the signal line between the strain gauge and the dynamic strain indicator; the signal line between the dynamic strain indicator and the host computer system; the signal line between the intake valve and the exhaust valve and the valve body controller; the signal line between the valve body controller and the host computer system; the power supply includes the host computer system, the signal generator, the speed controller, the charge amplifier, and the oscilloscope. The determination of the installation position of the multitude of the pads is to ensure that the primary vibration platform does not deviate from its original position when vibrating according to the first-stage bending displacement mode shape, and to reduce the energy loss of the primary vibration platform, and to weaken the vibration effect of the primary vibration platform on the ground. The multitude of the pads injected into the metal structural component amplifies the vibration energy and causes the metal structural component to vibrate according to the first-stage bending displacement mode shape. The step-like excitation signal, with the horizontal axis representing time and the vertical axis representing simulated voltage, has a stepped ascending shape, with each voltage peak Ut, i= 1,2 ,...,n; where n is a positive integer, corresponding to the excitation frequency co^ where the corresponding U1 horizontal axis is the excitation time At ; the angle of the eccentric block of the adjustable-speed motor is 0° <0 <180° . The beneficial effects of the present invention are as follows: 1 The invention employs the finite element numerical simulation software to obtain the multitude of the natural frequencies and the corresponding displacement modes for each stage of the primary vibration platform. Additionally, through harmonic response analysis, the multitude of the elastic gaskets is placed at the ends of the vibration platform's nodal lines, where the strain is minimal. This arrangement allows the primary vibration platform to vibrate according to the first-stage bending displacement mode shape, reducing the energy loss of vibration and weaken the vibration effect of the primary vibration platform on the ground. 2S The invention incorporates the multitude of the air springs with adjustable elastic coefficients and damping between the primary and secondary vibration platforms. During the vibration process, the elastic stiffness of these air springs is altered to improve the efficiency of the vibratory’ stress relief treatment. 3„ The invention installs the multitude of the air springs between the secondary vibration platform and the primary vibration platform, and installs the multitude of the pads between the metal structural components and the secondary vibration platform. According to the dual-mass spring-damper model, both the multitude of the air springs and pads serve to amplify energy, thereby addressing the issue of insufficient excitation energy in low-frequency vibration platforms during the vibratory stress relief treatment process. 4S The invention utilizes the finite element numerical simulation software to determine the multitude of the natural frequencies of the metal structural components and the multitude of the corresponding displacement mode shapes for each stage. The multitude of the pads is installed between the metal structural components and the primary vibration platform. These pads injected into the metal structural components amplify the energy of vibration and cause them to vibrate according to the first-stage bending displacement mode shape, thereby enhancing the effectiveness of the vibratory stress relief treatment. 5, The invention based on the distribution of residual stress in the metal structural components, fixes and installs the metal structural components at the position of maximum dynamic stress on the secondary vibration platform to further enhance the effect of vibratory stress relief. 6, The invention proposes a method for eliminating residual stress in metal structural components by employing the multi-level vibratory stress relief platform, This system is controlled by the host computer system, which reduces the workload, increases work efficiency, and enhances the intelligent level of the low-frequency vibration platform. 7,, The invention while retaining the advantages of the original low-frequency vibratory stress relief platform in eliminating residual stress, also proposes a method for eliminating residual stress by employing a multi-level vibratory stress relief platform. This addresses the shortcomings of the low-frequency vibratory stress relief platform, such as the inability to clamp small-sized metal structural components and the poor effectiveness in eliminating residual stress. Brief Description of the Drawings Fig. 1 is a schematic diagram of the multi-level vibratory stress relief platform for eliminating residual stress by employing the platform in the method of the present invention. Fig. 2 is a flowchart of the method for eliminating residual stress by employing the platform in the method of the present invention. Fig. 3 is a schematic diagram of the multi-level vibratory stress relief platform and the four air springs used in the method of the present invention for eliminating residual stress. Fig. 4 is a schematic diagram of the natural frequency of the primary vibration platform and the displacement mode shape corresponding to the natural frequency in the method of the present invention for eliminating residual stress. Fig. 5 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 the present invention for eliminating residual stress. Fig. 6 is a schematic diagram of the forced vibration model under harmonic excitation of a two-degree-of-freedom system in the method of the present invention for eliminating residual stress. Embodiments In order to provide a clearer understanding of the technical features, purposes, and effects of the present invention, the specific implementation of the invention is now described in detail with reference to the accompanying drawings. The content described in the embodiment of the present specification is merely an enumeration of the forms of implementation of the inventive concept. The scope of protection of the present invention should not be considered limited to the specific forms stated in the embodiment. The scope of protection of the present invention also extends to equivalent technical means that technicians in the field could conceive based on the inventive concept. With reference to the accompanying drawings, a further description is given of the method of the present invention for eliminating residual stress by employing a multilevel vibratory stress relief platform: Fig. 1 is a schematic diagram of the multi-level vibratory stress relief platform; the multi-level vibratory stress relief platform comprising a host computer system 1, a signal generator, a speed controller 2, an adjustable-speed motor 3, a primary vibration platform 4, a secondary vibration platform 5, a multitude of G-clamps, a multitude of air springs 6, an additional air chamber 7, an intake valve 8, an exhaust valve 9, a valve body controller 10, a multitude of elastic gaskets 11, a multitude of acceleration sensors 12, a multitude of pads 13, a charge amplifier 14, a strain gauge 15, a dynamic strain indicator 16, and an oscilloscope 17; the adjustable-speed motor 3 is connected to the primary vibration platform 4 by the multitude of the G-clamps; each elastic gasket 11 is installed at a lower end of the primary vibration platform 4; each air spring 6 is installed between the secondary vibration platform 5 and the primary vibration platform 4; an air intake of the air spring 6 is connected to the intake valve 8; the intake valve 8 and the exhaust valve 9 are connected to the additional air chamber 7, and both the intake valve 8 and the exhaust valve 9 are connected to the valve body controller 10, and the valve body controller is connected to a valve body control module of the host computer system 1; a metal structural component 18 is clamped and fixed on the secondary vibration platform 5, with the multitude of the pads 13 placed between the metal structural component 18 and the secondary vibration platform 5; a signal generator control module within the host computer system 1 controlling the signal generator to output a step-like excitation signal, feeding through the speed controller 2 to the adjustable-speed motor 3, driving the adjustable-speed motor 3 to vibrate; the strain gauge 15 is affixed to the metal structural component 18, with an output end of the strain gauge connected to an input end of the dynamic strain indicator 16, and the output end of the dynamic strain indicator 16 is connected to the host computer system 1; the acceleration sensor 12 is installed on both the primary vibration platform 4 and the metal structural component 18; the output end of the acceleration sensor connected to the input end of the charge amplifier 14, and the output end of the charge amplifier 14 is connected to the input end of the oscilloscope 17, with the output end of the oscilloscope 17 connected to the host computer system 1. The host computer system comprises: a signal generator control module, a waveform and voltage display module, a strain waveform acquisition module and a peak strain extraction module, a finite element numerical simulation software, and a valve body-control module. Further, as shown in Fig. 3, the multitude of the air springs are arranged on both sides of a peak symmetric axis II of displacement mode shape of the primary vibration platform by using bolt connections, and according to the results of the modal analysis, the multitude of the air springs installed at the position where the amplitude is the same as that of the primary vibration platform. Further, as shown in Fig. 4, which is a schematic diagram of the natural frequency of the primary vibration platform and the corresponding displacement mode shape, the multitude of the elastic gaskets is placed on the nodal line I of the first-stage bending displacement mode shape of the primary vibration platform, and the multitude of the air springs are arranged on both sides of the peak symmetry axis II of the displacement mode shape of the primary vibration platform, ensuring that the distance Xj from the multitude of the air springs to the peak symmetry axis is less than the distance x 2 from the multitude of the elastic gaskets to the peak symmetry axis. Further, as shown in Fig. 5, it is a schematic diagram of the natural frequency of the secondary vibration platform and the corresponding displacement mode shape. The upper ends of the multitude of the air springs are fixed on both sides of the displacement peak symmetry axis IV of the secondary vibration platform, with the distance from the multitude of the air springs to the middle of the displacement peak symmetry axis being x 3 . Further, the valve body control module of the host computer system controls an air pressure of the multitude of the air springs, and thereby controls an air spring's elastic coefficient, through the valve body controller by managing the intake valve and the exhaust valve. The upper ends of the multitude of the air springs are collectively connected to an air inlet to ensure that the air pressure, and consequently the elastic stiffness and damping, are the same for the four air springs. Each pad consist of an upper sleeve, a spring, and a lower sleeve, with the upper end of the spring installed in the upper sleeve and the lower end of the spring installed in the lower sleeve, and the upper sleeve being embedded in the lower sleeve. The multitude of the air springs is installed between the secondary vibration platform and the primary vibration platform, and the multitude of the pads is installed between the metal structural component and the secondary vibration platform. According to the dual-mass spring-damper model, both the multitude of the air springs and pads serve to amplify the excitation energy. The dynamic strain indicator is a multi-channel strain gauge that display s strain waveforms in real-time. The strain gauge is attached to the positions of peak residual stress on the metal structural components; with the first strain gauge attached along the first principal stress direction of the metal structural component and the second strain gauge attached along the second principal stress direction. The multitude of the elastic gaskets is installed on the nodal lines of the first-stage bending displacement vibration mode shape of the primary vibration platform; according to the forced vibration model of a damped two-degree-of-freedom system under the harmonic excitation, when the adjustable-speed motor excites the primary vibration platform, the excitation energy of the primary? vibration platform is multi-level amplified. Further, as shown in Fig. 2, which is a flowchart of a method for eliminating residual stress by employing a multi-level vibratory stress relief platform of the present invention, the method proposed by the invention for eliminating residual stress with the multi-level vibratory stress relief platform includes the following steps: step (1): obtaining a multitude of natural frequencies and a multitude of displacement mode shapes: pre-installing a finite element numerical simulation software in the host computer system; using the finite element numerical simulation software to establish a three-dimensional finite element model of the primary vibration platform, secondary vibration platform, and the metal structural component; using a modal analysis capability of the finite element numerical simulation software to analyze the primary and secondary vibration platforms; and the metal structural component to obtain the multitude of the natural frequencies of each stage for the primary vibration platform, secondary vibration platform and the metal structural component, along with the multitude of the corresponding displacement mode shapes for each stage; step (2): acquiring a maximum dynamic surface stress at the natural frequency of a vibratory stress relief treatment: utilizing the modal analysis capability of the finite element numerical simulation software to analyze the multitude of the natural frequencies and the multitude of the corresponding displacement mode shapes of the primary vibration platform, the secondary vibration platform and the metal structural component; analyzing a harmonic response of the multitude of the natural frequencies and the multitude of the corresponding displacement mode shapes of the primary vibration platform, the secondary vibration platform and the metal structural component to determine a nodal line of a first-stage bending displacement mode of the primary vibration platform and obtaining a maximum dynamic stress position of an upper surface of the secondary vibration platform satisfying the primary vibration platform vibrating at the natural frequency o 0 of the first-stage bending vibration; step (3): determining a multitude of installation positions for the primary vibration platform, the multitude of the air springs, the secondary vibration platform, the multitude of the pads, the metal structural component, the acceleration sensor, and the strain gauge: placing the multitude of the elastic gaskets on the nodal line I of the first-stage bending displacement mode shape of the primary’ vibration platform on the basis of the result of the modal analysis and a harmonic response analysis; securing the adjustable-speed motor on both sides of a peak symmetric axis of the first-stage bending displacement mode shape of the primary vibration platform; installing each acceleration sensor at the vibration peak position of the first-stage bending displacement mode shape of the secondary vibration platform, and the metal structural component; employing a X-ray diffraction to ascertain a residual stress distribution in the metal structural component and adhering the strain gauge to a peak residual stress position; aligning these peak residual stress position with the maximum dynamic stress position on the upper surface of the secondary vibration platform; inserting the multitude of the pads between the metal structural component and the secondary vibration platform on both sides of the peak symmetric axis IV of the first-stage bending displacement mode shape, and clamping the metal structural component onto the secondary vibration platform using the multitude of the G-clamps; step (4): determining an excitation frequency and an angle of an eccentric block of the adjustable-speed motor for the multi-level vibratory stress relief platform: fixing the angle of the eccentric block 0 ; controlling the signal generator to output the step-like excitation signal through the signal generator control module in the host computer system; obtaining an acceleration amplitude of the secondary vibration platform under the step-like excitation signal at a different voltage in a waveform and voltage display module of the host computer system for different voltage peak value Ut, i=l,2,...,n; where n being a positive integer, corresponding to the excitation frequency co t, recording a maximum acceleration amplitude amax, and the corresponding excitation frequency con ; adjusting the angle of the eccentric block 9 of the adjustable-speed motor; controlling the signal generator control module in the host computer system to output the excitation signal with voltage value Un, and excitation frequency con ; obtaining the acceleration amplitude level a of the secondary vibration platform at the different angle of the eccentric block of the adjustable-speed motor at the excitation frequency on , and recording the angle of the eccentric block 0O satisfying the acceleration amplitude level Cl >; where Uo being a voltage output by the signal generator, co being the excitation frequency of the secondary vibration platform of the multi-level vibratory stress relief platform, and 0O being the angle of the eccentric block of the adjustable-speed motor; adjusting the signal generator in the host computer system through the following steps; step (4.1): activating the signal generator control module of the host computer system to set the voltage and frequency peak value of the signal input to the speed controller; creating a step-like simulated excitation signal and saving the step-like simulated excitation signal in the host computer system; transmitting and saving the step-like simulated excitation signal to the signal generator; disconnecting the host computer system from the signal generator; inputting the step-like simulated excitation signal into the speed controller to drive the adjustable-speed motor, the adjustable-speed motor generating an excitation force on the primary vibration platform; actuating the secondary vibration platform, inducing synchronized vibration of the air spring on the primary vibration platform, with the acceleration sensor receiving vibration signal from both the secondary vibration platform and the metal structural component; converting the signal through the charge amplifier into a voltage signal; displaying the acceleration amplitude level of the secondary vibration platform and the metal structural component, along with the frequency of the corresponding excitation signal in the waveform and voltage display module of the host computer system; step (4.2): converting the vibration signal collected by the acceleration sensor from the secondary vibration platform and the metal structural component into the voltage signal via a charge amplifier; the conversion relationship between the acceleration amplitude level a of the metal structural component and the secondary vibration S x B 2 platform and the voltage signal being a =---— x U ■, with units of m / s where being a sensitivity of the acceleration sensor, with units of pC / m-S 2, / ?2 being a sensitivity coefficient at the input end of the charge amplifier, with units of pC / Unit, and S being a amplification factor with units of Unit / V; step (4.3): setting the acceleration amplitude level for the metal structural component: when the acceleration amplitude level on the metal structural component reaches the predetermined critical threshold Ct^-, the acceleration amplitude level exceeding the critical threshold is utilized as an effective acceleration amplitude level a for a multi-level energy-controllable vibratory' stress relief platform to eliminate residual stress; step (5): adjusting a damping factor and damping ratio q : the metal structural component and the multitude of the pads constitute a primary vibration system with the natural frequency of ©j and the damping ratio of where Oj = , the secondary vibration platform, in conjunction with the multitude of the air springs, forms a secondary vibration system with the natural frequency of o2 and the damping ratio of £ 2, where ©2 and = —— \m2 . A mass ratio of the secondary vibration platform to the metal structural component is p , where p = m2 / m], g = © / ©j. The excitation frequency of the primary vibration platform is CO, and the natural frequency of the primary vibration system is © j . x j is the amplitude of the metal structural component, x 2 is the amplitude of the secondary vibration platform, X is the amplitude of the primary vibration platform, m, is the mass of the metal structural component, m2 is the mass of the secondary vibration platform, the multitude of the pads is equivalent to an elastic element with a stiffness of kj and a damping element Cj, the multitude of the air springs are equivalent to the elastic element with a stiffness of k2 and the damping element c2. Establish a equation of motion for the vibration system in accordance with a momentum theorem: nijXj + CjXj + kjXj - ^x, - kjX2 = 0 J m2x2 +(cj + c2)x, +(k, +k2)x2 (1) ^qxj - kjXj = c,X + k2X Applying the Laplace transform to the equation of motion yields: (mjS^ + c1s + k1)xi (s)-(c1s + k])X2(s) = 0 |_m2s2+(cj+c2)s + kj+k2 JX2 (s)-(c1s + k1)X1 (s) = (c2s + k2)X(s) Simplifying the equation of motion (2) by eliminating X^s) , yields the ratio of the amplitude of the secondary vibration platform to the amplitude of the primary vibration platform, that is, the amplification factor a 2 of the second stage of the vibratory stress relief platform. X2(s) (c2s + k2)(m1s2+c1s + k]) a2 = —= --------------------------— --------- (3 ) X(s) I m2s2 + (cj + c2) s + kj + k2 [(m^2 + c,s + k, )-(cjS + kj Simplifying the equation of motion (2) by eliminating X(s) yields the amplification factor a, of the first-stage of the vibratory stress relief platform. a = xi(s)_ (^+^)(^ + ^) 1 X2(s) (cjS+k^rr^s2 + CjS + kJ Simplifying the equation of motion (2) by eliminating X2(s) yields the ratio of the amplitude of the metal structural component to the amplitude of the primary vibration platform, that is the total amplification factor a0 of the vibratory stress relief platform. ao = =______________(^s + kj^s + k,)______________ X(s) [m2s2 +(C] +c2)s + k; +k2Xni]S2 +c1s + k1)-(c1s + k1)2 Given s=jw, based on the frequency response of x, to X, an amplitude frequency characteristic of the metal structural component Xj relative to the primary' vibration platform X can be determined, which corresponds to the total amplification factor a0 of the vibratory' stress relief platform. «o(g’ = X^jw) _ / A2 +B2 X(jw) C2 +D2 (6) A = f2 -4½¾2 B = 2f +   ) g C = g4-f-!- + f' + i + 4i;iy'| g'+f (7) D = 2fg(52+51f)-2k +    +i;2f|g I H ) Where A, B. C, D are coefficients defined for simplifying calculations. step (6): eliminating residual stress by' means of employing the multi-level vibratory stress relief platform: controlling a signal generator via a signal generator control module of the host computer system to output the excitation signal with an initial voltage excitation signal Uo satisfying the angle of the eccentric block 0O of the adjustable speed motor; conducting a fixed-frequency vibratory stress relief on the metal structural component at the excitation frequency CD; collecting an unchanged strain waveform recorded by the dynamic strain indicator of the metal structural component using a strain waveform acquisition module in the host computer system; adjusting the intake valve via the valve body control module of the host computer system; increasing the acceleration vibration level a of the metal structural component by introducing an air to increase an air spring's elastic coefficient; continuing to introduce the air at the acceleration vibration level a reaching a peak; stopping the gas input at the acceleration vibration level a reaching a peak; collecting an unchanged strain waveform again recorded by' the dynamic strain indicator using the strain waveform acquisition module; cutting off the power supply; and terminating the vibratory stress relief treatment of the metal structural component; the finite element numerical simulation software referred to is ANSYS finite element software. The signal connections include a signal line between the host computer system and the signal generator; the signal line between the signal generator and the speed controller; the signal line between the speed controller and the adjustable-speed motor; the signal line between the acceleration sensor and the charge amplifier; the signal line between the charge amplifier and the oscilloscope; the signal line between the oscilloscope and the host computer system; the signal line between the strain gauge and the dynamic strain indicator; the signal line between the dynamic strain indicator and the host computer system; the signal line between the intake valve and the exhaust valve and the valve body controller; the signal line between the valve body controller and the host computer system; the power supply includes the host computer system, the signal generator, the speed controller, the charge amplifier, and the oscilloscope. The determination of the installation position of the multitude of the pads is to ensure that the primary vibration platform does not deviate from its original position when vibrating according to the first-stage bending displacement mode shape, and to reduce the energy loss of the primary vibration platform, and to weaken the vibration effect of the primary vibration platform on the ground. The multitude of the pads injected into the metal structural component amplifies the vibration energy and causes the metal structural component to vibrate according to the first-stage bending displacement mode shape. The step-like excitation signal, with the horizontal axis representing time and the vertical axis representing simulated voltage, has a stepped ascending shape, with each voltage peak U1, i = 1 ,2 ,...,n; where n is a positive integer, corresponding to the excitation frequency where the corresponding UI horizontal axis is the excitation time At; the angle of the eccentric block of the adjustable-speed motor is 0° <0 <180° .

Claims

1. A method for eliminating residual stress by employing a multi-level vibratory stress relief platform, the multi-level vibratory' stress relief platform comprising a host computer system (1), a signal generator, a speed controller (2), an adjustable-speed motor (3), a primary vibration platform (4), a secondary vibration platform (5), a multitude of G-clamps, a multitude of air springs (6), an additional air chamber (7), an intake valve (8), an exhaust valve (9), a valve body controller (10), a multitude of elastic gaskets (11), a multitude of acceleration sensors (12), a multitude of pads (13), a charge amplifier (14), a strain gauge (15), a dynamic strain indicator (16), and an oscilloscope (17); the adjustable-speed motor (3) is connected to the primary vibration platform (4) by the multitude of the G-clamps; each elastic gasket (11) is installed at a lower end of the primary vibration platform (4); each air spring (6) is installed between the secondary vibration platform (5) and the primary vibration platform (4); an air intake of the air spring (6) is connected to the intake valve (8); the intake valve (8) and the exhaust valve (9) are connected to the additional air chamber (7), and both the intake valve (8) and the exhaust valve (9) are connected to the valve body controller (10), and the valve body controller is connected to a valve body control module of the host computer system (1); a metal structural component (18) is clamped and fixed on the secondary vibration platform (5), with the multitude of the pads (13) placed between the metal structural component (18) and the secondary vibration platform (5); a signal generator control module within the host computer system (1) controlling the signal generator to output a step-like excitation signal, feeding through the speed controller (2) to the adjustable-speed motor (3), driving the adjustable-speed motor (3) to vibrate; the strain gauge (15) is affixed to the metal structural component (18), with an output end of the strain gauge connected to an input end of the dynamic strain indicator (16), and the output end of the dynamic strain indicator (16) is connected to the host computer system (1); the acceleration sensor (12) is installed on both the primary' vibration platform (4) and the metal structural component (18); the output end of the acceleration sensor connected to the input end of the charge amplifier (14), and the output end of the charge amplifier (14) is connected to the input end of the oscilloscope (17), with the output end of the oscill oscope (17) connected to the host computer system (1);characterized in that the method for eliminating residual stress by employing a multilevel vibratory-' stress relief platform comprises the folloyvmg steps:step (1): obtaining a multitude of natural frequencies and a multitude of displacement mode shapes: pre-installing a finite element numerical simulation software in the host computer system; using the finite element numerical simulation software to establish a three-dimensional finite element model of the primary vibration platform, secondary vibration platform, and the metal structural component; using a modal analysis capability of the finite element numerical simulation software to analyze the primary and secondary vibration platforms, and the metal structural component to obtain the multitude of the natural frequencies of each stage for the primary vibration platform, secondary vibration platform and the metal structural component, along with the multitude of the corresponding displacement mode shapes for each stage;step (2): acquiring a maximum dynamic surface stress at the natural frequency of a vibratory stress relief treatment: utilizing the modal analysis capability of the finite element numerical simulation software to analyze the multitude of the natural frequencies and the multitude of the corresponding displacement mode shapes of the primary vibration platform, the secondary vibration platform and the metal structural component; analyzing a harmonic response of the multitude of the natural frequencies and the multitude of the corresponding displacement mode shapes of the primary vibration platform, the secondary vibration platform and the metal structural component to determine a nodal line of a first-stage bending displacement mode of the primary vibration platform and obtaining a maximum dynamic stress position of an upper surface of the secondary vibration platform satisfying the primary vibration platform vibrating at the natural frequency o0 of the first-stage bending vibration;step (3): determining a multitude of installation positions for the primary vibration platform, the multitude of the air springs, the secondary vibration platform, the multitude of the pads, the metal structural component, the acceleration sensor, and the strain gauge: placing the multitude of the elastic gaskets on the nodal line of the first-stage bending displacement mode shape of the primary’ vibration platform on the basis of the result of the modal analysis and a harmonic response analysis; securing the adjustable-speed motor at a vibration peak position of the first-stage bending displacement mode shape of the primary' vibration platform; installing each acceleration sensor at the vibration peak position of the first-stage bending displacement mode shape of the secondary' vibration platform, and the metal structuralcomponent; employing a X-ray diffraction to ascertain a residual stress distribution in the metal structural component and adhering the strain gauge to a peak residual stress position; aligning these peak residual stress position with the maximum dynamic stress position on the upper surface of the secondary vibration platform; inserting the multitude of the pads between the metal structural component and the secondary vibration platform at the vibration peak position of the first-stage bending displacement mode shape, and clamping the metal structural component onto the secondary vibration platform using the multitude of the G-clamps;step (4): determining an excitation frequency and an angle of an eccentric block of the adjustable-speed motor for the multi-level vibratory stress relief platform: fixing the angle of the eccentric block 0 ; controlling the signal generator to output the step-like excitation signal through the signal generator control module in the host computer system; obtaining an acceleration amplitude of the secondary vibration platform under the step-like excitation signal at a different voltage in a waveform and voltage display module of the host computer system for different voltage peak value U,, i=l,2,...,n; where n being a positive integer, corresponding to the excitation frequency co ,, recording a maximum acceleration amplitude amax, and the corresponding excitation frequency ®n ; adjusting the angle of the eccentric block 9 of the adjustable-speed motor; controlling the signal generator control module in the host computer system to output the excitation signal with voltage value Un, and excitation frequency ©n ; obtaining the acceleration amplitude level a of the secondary vibration platform at the different angle of the eccentric block of the adjustable-speed motor at the excitation frequency ron , and recording the angle of the eccentric block 90 satisfying the acceleration amplitude level <2^; where Uo being a voltage output by the signal generator, co being the excitation frequency of the secondary vibration platform of the multi-level vibratory stress relief platform, and 0O being the angle of the eccentric block of the adjustable-speed motor; adjusting the signal generator in the host computer system through the following steps;step (4.1): activating the signal generator control module of the host computer system to set the voltage and frequency peak value of the signal input to the speed controller; creating a step-like simulated excitation signal and saving the step-like simulated excitation signal in the host computer system; transmitting and saving thestep-like simulated excitation signal to the signal generator; disconnecting the host computer system from the signal generator; inputting the step-like simulated excitation signal into the speed controller to drive the adjustable-speed motor, the adjustable-speed motor generating an excitation force on the primary vibration platform; actuating the secondary vibration platform, inducing synchronized vibration of the air spring on the primary vibration platform, with the acceleration sensor receiving vibration signal from both the secondary vibration platform and the metal structural component; converting the signal through the charge amplifier into a voltage signal; displaying the acceleration amplitude level of the secondary vibration platform and the metal structural component, along with the frequency of the corresponding excitation signal in the waveform and voltage display module of the host computer system;step (4.2): converting the vibration signal collected by the acceleration sensor from the secondary vibration platform and the metal structural component into the voltage signal via a charge amplifier; the conversion relationship between the acceleration amplitude level a of the metal structural component and the secondaryS x B 2vibration platform and the voltage signal being a =---— x U, with units of m / SAwhere being a sensitivity of the acceleration sensor, with units of pC / Hl-S 2, being a sensitivity coefficient at the input end of the charge amplifier, with units of pC / Unit, and S being a amplification factor with units of Unit / V;step (4.3): setting the acceleration amplitude level for the metal structural component: the acceleration amplitude level exceeding the critical threshold being utilized as an effective acceleration amplitude level a for a multi-level energy-controllable vibratory stress relief platform to eliminate residual stress satisfying the acceleration amplitude level on the metal structural component reaches the predetermined critical threshold ;step (5): adjusting the damping factor Q and damping ratio q ;step (6): eliminating residual stress by means of employing the multi-level vibratory stress relief platform: controlling a signal generator via a signal generator control module of the host computer system to output the excitation signal with aninitial voltage excitation signal Uo satisfying the angle of the eccentric block 0O of the adjustable speed motor; conducting a fixed-frequency vibratory stress relief on the metal structural component at the excitation frequency CO; collecting an unchanged strain waveform recorded by the dynamic strain indicator of the metal structural component using a strain waveform acquisition module in the host computer system; adjusting the intake valve via the valve body control module of the host computer system; increasing the acceleration vibration level a of the metal structural component by introducing an air to increase an air spring's elastic coefficient; continuing to introduce the air at the acceleration vibration level a reaching a peak; stopping the gas input at the acceleration vibration level a reaching a peak; collecting an unchanged strain waveform again recorded by the dynamic strain indicator using the strain waveform acquisition module; cutting off the power supply; and terminating the vibratory stress relief treatment of the metal structural component.

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