阅读说明：本技术 一种空间三维残余应力超声检测方法 (Spatial three-dimensional residual stress ultrasonic detection method ) 是由 赵勃 阚艳 陈婷 史维佳 王丙泉 于 2021-09-06 设计创作，主要内容包括：本发明公开了一种空间三维残余应力超声检测方法,属于超声检测技术领域。步骤一、推导三相应力状态下声弹性方程；步骤二、根据所述三相应力状态下声弹性方程,确定空间三维残余应力超声检测方案。本发明通过理论推导得到三向应力状态下的声弹性方程,并基于此进一步得到了三维空间残余应力的检测方案。本发明提出的三维空间残余应力的检测方法,操作简单,成本较低,具有可行性,解决了现有传统残余应力只能实现单轴或平面检测的不足。同时也为后续三维空间残余应力检测的进一步研究提供了一定的想法与方向。(The invention discloses a spatial three-dimensional residual stress ultrasonic detection method, and belongs to the technical field of ultrasonic detection. Step one, deducing an acoustoelastic equation under a three-phase stress state; and step two, determining a spatial three-dimensional residual stress ultrasonic detection scheme according to the acoustoelastic equation under the three-phase stress state. According to the invention, the acoustoelastic equation under the three-dimensional stress state is obtained through theoretical derivation, and a detection scheme of the three-dimensional space residual stress is further obtained based on the acoustoelastic equation. The method for detecting the residual stress in the three-dimensional space is simple to operate, low in cost and feasible, and overcomes the defect that the conventional residual stress can only realize single-axis or plane detection. Meanwhile, certain ideas and directions are provided for further research of subsequent three-dimensional space residual stress detection.)

1. The ultrasonic detection method for the spatial three-dimensional residual stress is characterized by comprising the following steps of:

step one, deducing an acoustoelastic equation under a three-phase stress state;

and step two, determining a spatial three-dimensional residual stress ultrasonic detection scheme according to the acoustoelastic equation under the three-phase stress state.

2. The ultrasonic testing method for the spatial three-dimensional residual stress according to claim 1, wherein in step one, in particular,

a spatial three-dimensional stress ultrasonic detection scheme. Assuming the plane wave propagation direction is along e₁₁And obtaining a longitudinal wave velocity expression represented by the initial coordinate by solving the eigenvalue of the sound tensor, and arranging the longitudinal wave velocity expression into a common form expression as follows:

in the formula: v. of_LThe longitudinal wave velocity is in a three-dimensional stress state; rho⁰Density of the object in an unstressed state; e is the modulus of elasticity;is a constant; e.g. of the type₁₁、e₂₂、e₃₃Three main strains respectively; lambda and mu are second-order elastic constants of the medium; l and m are three-order elastic constants of the medium; sigma₁₁、σ₂₂、σ₃₃Three principal stresses, respectively; v is the poisson ratio,

from the formula (1), the ultrasonic longitudinal sound velocity is the principal stress σ from three directions₁₁、σ₂₂、σ₃₃Jointly determined, the result of the formula (1) provides theoretical support for researching the relation between the ultrasonic wave speed and the stress under the complex stress, an elastic wave sound speed measurement formula of a plane stress field under the combined action of the two-way stress needs to be considered,

to obtain the result in general form, the symbol e is used₁、e₂、e₃Expressing principal strain by σ₁、σ₂、σ₃Representing principal stress, assuming plane wave in ξ₁The direction of the light is transmitted,

suppose the plane wave is xi₂The direction of the light is transmitted,

suppose the plane wave is xi₃The direction of the light is transmitted,

from the theory of material mechanics, it is known that for a spatial three-dimensional stress state, there isThree mutually perpendicular principal stresses, respectively marked as a first principal stress, a second principal stress and a third principal stress, are expressed as plane waves in xi₁The directional propagation is taken as an example to carry out space three-dimensional stress state analysis, and according to the propagation characteristic of the LCR wave, the LCR wave is in the xi material₁-ξ₂The surface is small amplitude wave, the propagation direction is parallel to the vibration direction, when the propagation direction of LCR wave is parallel to the first main stress direction, it must be perpendicular to the second and third main stress directions, then the acoustic elastic equation under three-way stress state is simplified into the acoustic elastic equation under plane stress state,

substituting the formula (5) into the formula (2),

will be provided withIs substituted into the formula (6) to obtain,

in the formula:in order to be the bulk modulus,

when e is₁＝e₂＝e₃When the value is 0, the longitudinal wave velocity in the unstressed state is obtained as follows:

the formula (7) and the formula (8) are subtracted,

since the change in speed is small, the approximation can be made as follows, v_L+v_L0≈2v_L0But due to v_L-v_L0Not equal to 0, the formula is substituted into the formula (9),

then

In the formula: c. C₁、c₂、c₃Respectively, the stress coefficients of three mutually perpendicular directions.

3. The ultrasonic testing method for the three-dimensional residual stress in the space according to claim 1, wherein in the step one, specifically, a fixed distance sound time method is adopted in the actual measurement process, the speed variation is converted into the measurement of the time variation, and the fixed distance of ultrasonic wave propagation is set as L, t_l1Propagation time of LCR wave in stressed state, t_l0The LCR wave propagation time is in an unstressed state.

The formula (15) is substituted for the formula (11),

suppose σ₁＞σ₂When the "one-shot" ultrasonic probe is placed, i.e. the propagation direction of the longitudinal wave and the maximum principal stress σ₁When the included angle is theta, according to the Morel circle stress theory, the stress in the direction and the stress vertical to the direction are,

four different directions theta need to be performed simultaneously₁，θ₂，θ₃，θ₄Measurement of the stress magnitude of (c): the first selected measuring direction is regarded as 0 degree, three directions of 30 degrees, 60 degrees and 90 degrees are selected for detection, and four groups of sound time measuring data t are obtained_l1、t_l2、t_l3And t_l4. Note t_l0-t_l1＝Δt₁，t_l0-t_l2＝Δt₂，t_l0-t_l3＝Δt₃，t_l0-t_l4＝Δt₄Due to t_l4≈t_l3≈t_l2≈t_l1≈t_l0However, t_l0-t_l4≠0，t_l0-t_l3≠0，t_l0-t_l2≠0，t_l0-t_l1If the number is not equal to 0, then,

the unknown quantity sigma of the four space three-dimensional stress can be obtained by simultaneous solving₁、σ₂、σ₃And theta.

Technical Field

The invention relates to a spatial three-dimensional residual stress ultrasonic detection method, and belongs to the technical field of ultrasonic detection.

Background

The residual stress is elastic stress which is caused by uneven plastic deformation in the material and keeps self balance, and is divided into macroscopic stress and microscopic stress. Macroscopic residual stress, i.e. the average stress between grains in a material, is the main test object in engineering applications. In various machines and machines, residual stress is generated in the components, and the generated residual stress state is greatly different according to various processing methods or treatment methods. Residual stress and residual stress maldistribution will have a significant impact on fatigue strength, static strength, structural deformation, and service life of the component. For example, the residual stress of the weld seam, which affects the life cycle of the welded structure, causes severe stress concentration at the weld seam, which leads to microcracks in the weld seam, and the cracks may cause cracking of the welded part under certain conditions.

Compared with other nondestructive testing methods for residual stress, the ultrasonic nondestructive testing method has the advantages of high testing speed, no radiation damage to human bodies, low cost, better spatial resolution, larger testing depth range, capability of realizing field holding and carrying, capability of completing the testing of the macroscopic participation of surface and subsurface stress in the stress magnitude and the tension and compression state and the like, and has been widely paid attention by domestic and foreign scholars. Beijing university of science and engineering proposes a nonlinear ultrasonic detection method of bolt axial stress (a nonlinear ultrasonic detection method of bolt axial stress, publication No. CN 111442869A). The invention provides a nonlinear ultrasonic detection method for axial stress of a bolt, which comprises the following implementation steps: step A: establishing a relation model between the amplitude of the second harmonic and the amplitude of the fundamental wave based on the propagation theory of the ultrasonic wave in the isotropic medium to obtain an expression of a relative nonlinear coefficient; and B: carrying out an axial stress loading experiment on a bolt sample, carrying out nonlinear ultrasonic detection, and calculating relative nonlinear coefficients under different stress states; and C: fitting the loaded axial stress and the corresponding relative nonlinear coefficient, determining the ultrasonic detection coefficient of the axial stress of the bolt, and finally obtaining a relational expression of the axial stress of the bolt and the relative nonlinear coefficient; through the steps, the nonlinear ultrasonic detection of the axial stress of the bolt can be realized, the method can be used for quickly and accurately detecting the axial stress of the bolt, and the accuracy and the practicability of the bolt axial stress detection technology are improved. The method has problems that: only the axial stress detection of the bolt can be realized, and the spatial three-dimensional representation of the residual stress cannot be carried out.

University of major graduates proposes a plane residual stress electromagnetic ultrasonic detection method (a plane residual stress electromagnetic ultrasonic detection method, publication number: CN 110632177A). The method comprises the steps of firstly assembling an electromagnetic ultrasonic detection system, and measuring stress detection ultrasonic signal waveforms along three directions by utilizing ultrasonic coils in an electromagnetic ultrasonic surface wave probe so as to calibrate the acoustic elastic coefficient of the material. The method comprises the steps of collecting three directional surface wave signals of a point to be measured, and calculating the size and the direction of plane stress by applying an ultrasonic detection theoretical formula. The method adopts a surface wave probe with three-transmitting and three-receiving functions, and realizes one-time positioning and multi-parameter simultaneous measurement of two main stresses and the included angle of the main stresses in a plane stress state. The space between the receiving and transmitting probes is reduced and the spatial resolution of the probes is improved by reducing the turns, the line width and the line distance of the ultrasonic transmitting and receiving coils. The radio frequency connector is adopted to connect the circuit board and the impedance matching network, so that the installation and repeated use are convenient, the detection method is simple, and the efficiency is high. The method has problems that: the method and the detection system are complex, can only complete plane residual stress detection of the to-be-detected part, and cannot perform space three-dimensional representation on the residual stress.

A residual stress water immersion ultrasonic detection method for an aluminum alloy pre-stretching plate is provided by Beijing aviation material research institute of China aviation industry group company (a residual stress water immersion ultrasonic detection method for an aluminum alloy pre-stretching plate, publication No. CN 103543206A). The invention relates to a water immersion ultrasonic detection method for residual stress of an aluminum alloy pre-stretching plate, belonging to the field of nondestructive detection, and comprising the following steps: making a reference test block; measuring and calibrating; and measuring the residual stress. The method adopts a water immersion method, can ensure the temperature consistency in the stress calibration and stress measurement process by controlling the water temperature to be constant, thereby eliminating the influence of temperature difference on the ultrasonic speed and eliminating the temperature error, and in addition, adopts an automatic scanning frame to replace manual scanning, can ensure the distance between a probe and the surface of a material to be measured to be constant in the measurement process, thereby eliminating the influence of the coupling condition difference on the sound propagation time and eliminating the coupling error. The method is beneficial to nondestructive evaluation of the near-surface residual stress of the aluminum alloy pre-stretched plate. The method has problems that: the method adopts a water immersion method, the detection environment is limited, only unidirectional residual stress detection of the to-be-detected part can be completed, and spatial three-dimensional representation of the residual stress cannot be performed.

At present, ultrasonic stress detection on a to-be-detected part in the market is usually towards common structures such as flat plates, bolts and welding seams, and axial, unidirectional or planar residual stress detection can only be realized. In summary, an ultrasonic detection method capable of realizing spatial three-dimensional stress is absent in the current market, and three-dimensional spatial characterization is performed on residual stress.

Disclosure of Invention

The invention aims to provide a spatial three-dimensional residual stress ultrasonic detection method, which is used for deducing a three-dimensional residual stress detection formula based on a longitudinal wave stress detection principle to realize the three-dimensional representation of the residual stress of a piece to be detected so as to solve the problems in the prior art.

A three-dimensional ultrasonic detection method for residual stress in space comprises the following steps:

step one, deducing an acoustoelastic equation under a three-phase stress state;

and step two, determining a spatial three-dimensional residual stress ultrasonic detection scheme according to the acoustoelastic equation under the three-phase stress state.

Further, in step one, specifically,

a spatial three-dimensional stress ultrasonic detection scheme. Assuming the plane wave propagation direction is along e₁₁And obtaining a longitudinal wave velocity expression represented by the initial coordinate by solving the eigenvalue of the sound tensor, and arranging the longitudinal wave velocity expression into a common form expression as follows:

in the formula: v. of_LThe longitudinal wave velocity is in a three-dimensional stress state; rho⁰Density of the object in an unstressed state; e is the modulus of elasticity;is a constant; e.g. of the type₁₁、e₂₂、e₃₃Three main strains respectively; lambda and mu are second-order elastic constants of the medium; l and m are three-order elastic constants of the medium; sigma₁₁、σ₂₂、σ₃₃Three principal stresses, respectively; v is the poisson ratio,

from the formula (1), the ultrasonic longitudinal sound velocity is the principal stress σ from three directions₁₁、σ₂₂、σ₃₃Jointly determined, the result of the formula (1) provides theoretical support for researching the relation between the ultrasonic wave speed and the stress under the complex stress, an elastic wave sound speed measurement formula of a plane stress field under the combined action of the two-way stress needs to be considered,

to obtain the result in general form, the symbol e is used₁、e₂、e₃Expressing principal strain by σ₁、σ₂、σ₃Representing principal stress, assuming plane wave in ξ₁The direction of the light is transmitted,

suppose the plane wave is xi₂The direction of the light is transmitted,

suppose the plane wave is xi₃The direction of the light is transmitted,

from the theory of material mechanics, it is known that for a spatial three-dimensional stress state, there are threeThe main stresses which are perpendicular to each other are respectively marked as a first main stress, a second main stress and a third main stress, and the plane wave is in xi₁The directional propagation is taken as an example to carry out space three-dimensional stress state analysis, and according to the propagation characteristic of the LCR wave, the LCR wave is in the xi material₁-ξ₂The surface is small amplitude wave, the propagation direction is parallel to the vibration direction, when the propagation direction of LCR wave is parallel to the first main stress direction, it must be perpendicular to the second and third main stress directions, then the acoustic elastic equation under three-way stress state is simplified into the acoustic elastic equation under plane stress state,

substituting the formula (5) into the formula (2),

will be provided withIs substituted into the formula (6) to obtain,

in the formula:in order to be the bulk modulus,

when e is₁＝e₂＝e₃When the value is 0, the longitudinal wave velocity in the unstressed state is obtained as follows:

the formula (7) and the formula (8) are subtracted,

since the change in speed is small, the approximation can be made as follows, v_L+v_L0≈2v_L0But due to v_L-v_L0Not equal to 0, the formula is substituted into the formula (9),

then

In the formula: c. C₁、c₂、c₃Respectively, the stress coefficients of three mutually perpendicular directions.

Further, in the step one, specifically, a fixed distance sound time method is adopted in the actual measurement process, the variation of the speed is converted into the measurement of the time variation, and the fixed distance of ultrasonic wave propagation is set as L, t_l1Propagation time of LCR wave in stressed state, t_l0The LCR wave propagation time is in an unstressed state.

The formula (15) is substituted for the formula (11),

suppose σ₁＞σ₂When the "one-shot" ultrasonic probe is placed, i.e. the propagation direction of the longitudinal wave and the maximum principal stress σ₁When the included angle is theta, according to the Morel circle stress theory, the stress in the direction and the stress vertical to the direction are,

four different directions theta need to be performed simultaneously₁，θ₂，θ₃，θ₄Measurement of the stress magnitude of (c): the first selected measuring direction is regarded as 0 degree, three directions of 30 degrees, 60 degrees and 90 degrees are selected for detection, and four groups of sound time measuring data t are obtained_l1、t_l2、t_l3And t_l4. Note t_l0-t_l1＝Δt₁，t_l0-t_l2＝Δt₂，t_l0-t_l3＝Δt₃，t_l0-t_l4＝Δt₄Due to t_l4≈t_l3≈t_l2≈t_l1≈t_l0However, t_l0-t_l4≠0，t_l0-t_l3≠0，t_l0-t_l2≠0，t_l0-t_l1If the number is not equal to 0, then,

the unknown quantity sigma of the four space three-dimensional stress can be obtained by simultaneous solving₁、σ₂、σ₃And theta.

The invention has the following beneficial effects: according to the invention, the acoustoelastic equation under the three-dimensional stress state is obtained through theoretical derivation, and a detection scheme of the three-dimensional space residual stress is further obtained based on the acoustoelastic equation. The method for detecting the residual stress in the three-dimensional space is simple to operate, low in cost and feasible, and overcomes the defect that the conventional residual stress can only realize single-axis or plane detection. Meanwhile, certain ideas and directions are provided for further research of subsequent three-dimensional space residual stress detection.

Drawings

FIG. 1 is a schematic diagram of principal stress of a material;

FIG. 2 is a schematic diagram of a spatial three-dimensional stress detection apparatus;

fig. 3 is a schematic diagram of spatial three-dimensional stress detection.

Part number in the figure: 1 is a single-array element oblique probe, and 2 is a test piece to be detected.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

A three-dimensional ultrasonic detection method for residual stress in space comprises the following steps:

step one, deducing an acoustoelastic equation under a three-phase stress state;

and step two, determining a spatial three-dimensional residual stress ultrasonic detection scheme according to the acoustoelastic equation under the three-phase stress state.

Further, the spatial three-dimensional stress ultrasonic detection scheme is specifically described with reference to fig. 1, 2 and 3. Assuming that the propagation direction of the plane wave is along e11, a longitudinal wave velocity expression represented by the initial coordinates can be obtained by solving the eigenvalues of the sound tensor, and the longitudinal wave velocity expression is arranged into a common form expression:

in the formula: v. of_LThe longitudinal wave velocity is in a three-dimensional stress state; rho⁰Density of the object in an unstressed state; e is the modulus of elasticity;is a constant; e.g. of the type₁₁、e₂₂、e₃₃Three main strains respectively; lambda and mu are second-order elastic constants of the medium; l and m are three-order elastic constants of the medium; sigma₁₁、σ₂₂、σ₃₃Three principal stresses, respectively; v is the poisson ratio,

from the formula (1), the ultrasonic longitudinal sound velocity is the principal stress σ from three directions₁₁、σ₂₂、σ₃₃Together, the result of the formula (1) provides theoretical support for researching the relation between the ultrasonic wave speed and the stress under complex stress, and the poisson ratio v of the aluminum alloy material is 0.3 generally, and at the moment, the longitudinal wave sound speed is mainly influenced by sigma parallel to the propagation direction₁₁The influence of the directional stress is influenced by σ perpendicular to its propagation direction₂₂、σ₃₃The influence of the directional stress is 0.3 times, however, by σ₂₂、σ₃₃The acoustic elastic effect caused by the directional stress is still not negligible. Therefore, the elastic wave sound velocity measurement formula of the plane stress field under the combined action of the two-way stress needs to be considered,

to obtain the result in general form, the symbol e is used later₁、e₂、e₃Expressing principal strain by σ₁、σ₂、σ₃Indicating the principal stress. Suppose the plane wave is xi₁The direction of the light is transmitted,

suppose the plane wave is xi₂The direction of the light is transmitted,

suppose the plane wave is xi₃The direction of the light is transmitted,

the theory of material mechanics shows that for the state of space three-dimensional stress, there are three main stresses perpendicular to each other, which are respectively marked as the first main stress, the second main stress and the third main stress, and the plane wave is in xi₁The directional propagation is taken as an example to carry out space three-dimensional stress state analysis, and according to the propagation characteristic of the LCR wave, the LCR wave is in the xi material₁-ξ₂The surface is small amplitude wave, the propagation direction is parallel to the vibration direction, when the propagation direction of LCR wave is parallel to the first main stress direction, it must be perpendicular to the second and third main stress directions, then the acoustic elastic equation under three-way stress state is simplified into the acoustic elastic equation under plane stress state,

substituting the formula (5) into the formula (2),

will be provided withIs substituted into the formula (6) to obtain,

in the formula:in order to be the bulk modulus,

when e is₁＝e₂＝e₃When the value is 0, the longitudinal wave velocity in the unstressed state is obtained as follows:

the formula (7) and the formula (8) are subtracted,

since the change in speed is small, the approximation can be made as follows, v_L+v_L0≈2v_L0But due to v_L-v_L0Not equal to 0, the formula is substituted into the formula (9),

then

In the formula: c. C₁、c₂、c₃Respectively, the stress coefficients of three mutually perpendicular directions.

Furthermore, due to the tiny acoustic elastic effect, direct sound velocity change is not easy to measure, and under a fixed condition, the sound velocity is inversely proportional to the LCR wave propagation time, so that a fixed distance sound time method is adopted in the actual measurement process, the speed variation is converted into the measurement of time change, the fixed distance of ultrasonic wave propagation is set as L, and t is set as_l1Propagation time of LCR wave in stressed state, t_l0The LCR wave propagation time is in an unstressed state.

The formula (15) is substituted for the formula (11),

in the actual detection process, the main stress direction of a stress to-be-detected piece is unknown, so that the condition that the 'one-sending-one-receiving' ultrasonic probe is parallel to the sigma cannot be ensured₁Direction is placed or parallel to sigma₂Directional placement, assuming σ₁＞σ₂When the "one-shot" ultrasonic probe is placed, i.e. the propagation direction of the longitudinal wave and the maximum principal stress σ₁When the included angle is theta, according to the Morel circle stress theory, the stress in the direction and the stress vertical to the direction are,

for quasi-isotropic composites in a stressed state, a measurement of only one time is not sufficient to obtain σ₁、σ₂、σ₃And theta are four unknowns, so the method requires four different directions theta to be performed simultaneously₁，θ₂，θ₃，θ₄For convenience of measurement, the first selected measurement direction is regarded as 0 °, and three directions of 30 °, 60 ° and 90 ° are selected for detection, so as to obtain four groups of acoustic time measurement data t_l1、t_l2、t_l3And t_l4. Note t_l0-t_l1＝Δt₁，t_l0-t_l2＝Δt₂，t_l0-t_l3＝Δt₃，t_l0-t_l4＝Δt₄Due to t_l4≈t_l3≈t_l2≈t_l1≈t_l0However, t_l0-t_l4≠0，t_l0-t_l3≠0，t_l0-t_l2≠0，t_l0-t_l1If the number is not equal to 0, then,

the unknown quantity sigma of the four space three-dimensional stress can be obtained by simultaneous solving₁、σ₂、σ₃And theta.

The above embodiments are only used to help understanding the method of the present invention and the core idea thereof, and a person skilled in the art can also make several modifications and decorations on the specific embodiments and application scope according to the idea of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.