CN114623956B - An Ultrasonic Measuring Method of Bolt Random Transverse Load and Its Action Direction - Google Patents

Abstract

The invention discloses an ultrasonic measurement method for random transverse loads and action directions of bolts, which comprises the following steps: (1) Preparing a thin film coating sensor with the center and the edge arranged at the top or the bottom of the bolt to be detected; (2) Calibrating the sound time and the load of the central electrode to obtain a load calibration coefficient of the central electrode; (3) Fitting a flight time array of the edge electrode under different loads and different angles to obtain an ultrasonic flight time-load-angle relation function; (4) When the bolt to be tested actually works, measuring the ultrasonic flight time of the central electrode and the edge electrode, and obtaining the maximum load at the moment by utilizing the ultrasonic flight time and the calibration coefficient of the central electrode; and solving by using the maximum load, the ultrasonic flight time of the edge electrode and a function of the ultrasonic flight time and the angle to obtain the random load action angle and direction. The invention realizes the synchronous measurement of the size and the direction of the transverse load of the connecting pieces such as the bolt fastener bearing the random transverse load for the first time by utilizing the matching scheme of the central electrode and the edge electrode, is particularly suitable for the online monitoring of the fastening connection structure bearing the random transverse load, and has the advantages of high measurement precision and good stability.

Description

An Ultrasonic Measuring Method of Bolt Random Transverse Load and Its Action Direction

technical field

The invention relates to the field of ultrasonic non-destructive testing technology and piezoelectric film, in particular to an ultrasonic measurement method for bolt random lateral load and its action direction.

Background technique

Bolt fasteners are subject to loads in random directions in application environments including vehicle road noise and vibration, ocean wave erosion, etc. And as the operating time increases, its material properties gradually degrade, so it is very necessary to carry out real-time online load evaluation on the connecting fasteners of these devices. Develop a new actual measurement method to measure fasteners subjected to random loads with high precision and meet the requirements of real-time detection of internal stress of fasteners, so as to evaluate random changes in space, time, and strength dimensions such as strong winds and earthquakes in real time The effect of the load.

Early research work on bolt stress measurement was carried out at home and abroad, most of which were based on axial stress measurement. According to the principle of acoustic elasticity, the bolt stress value can be quantitatively measured by measuring the propagation time of ultrasonic waves in the bolt, so as to judge the health status of the bolt connection. At present, the patch-type ultrasonic stress detection method has been used for many years, but since the piezoelectric chip is generally bonded to the bolt with epoxy resin or adhesive, it is easy to fall off. Moreover, since the thickness of the adhesive layer cannot be measured, the detection accuracy is greatly affected. In addition to the conventional stress detection method, at present, the pre-tightening force measurement method based on the PMTS (Permanent Mounted Transducer System) sensor has been partially applied in the direction of pre-tightening force detection. It mainly prepares a permanent piezoelectric sensor on the bolt, and then uses the inverse piezoelectric effect of the sensor to generate an ultrasonic signal in the bolt, and realizes the measurement of the internal load of the bolt by calibrating the relationship between different loads, temperatures and the flight time difference of the ultrasonic wave in the bolt. , is a direct, in-situ measurement of bolt load. However, including the conventional method and the piezoelectric sensor measurement method, there is no in-depth progress in the measurement of the lateral load or the technology to accurately measure the angle of the shear force.

In the process of implementing the present invention, the inventors of the present application have found that at least the following technical problems exist in the method of the prior art:

(1) The existing ultrasonic measurement of bolt load, including the piezoelectric film method or the traditional ultrasonic probe method, can only provide one time-of-flight data during the measurement process, and cannot simultaneously measure the two physical quantities of load magnitude and load azimuth angle . Therefore, these methods can only be applied to scenarios where the direction of the load is known, such as the installation process of torsion bolts; however, during the service process, the magnitude and direction of the load brought by the environment are random, and new measurement methods need to be developed.

(2) The stress generated by the transverse load on the shear plane of the bolt is non-uniform, and the resulting problem is that the theoretically constructed mapping relationship between the angle and the characteristic quantity is not one-to-one correspondence, that is to say , when the traditional single sensor is used to measure, it is possible to resolve two lateral load directions.

Therefore, the present invention proposes a two-step solution: firstly, the difference between the center sensor and the edge sensor is used to solve the influence of the load size, and secondly, the difference between two edge sensors with different azimuth angles is used to solve the problem of the uniqueness of the load angle measurement value .

Contents of the invention

The invention discloses an ultrasonic measurement method for bolt random transverse load and its action direction, which is used to realize the accurate measurement of the size and angle of the transverse load acting in random direction.

The invention provides an ultrasonic measurement method for bolt random lateral load and its direction of action, which is characterized in that it comprises the following steps:

An ultrasonic measurement method for bolt random lateral load and its direction of action, characterized in that it comprises the following steps:

Step S1, preparing thin-film coating sensors on the top or bottom of the bolt to be inspected in the center and on the edge;

Step S2, calibrate the acoustic time and load of the center electrode, and obtain the load calibration coefficient of the center electrode;

Step S3, fitting the ultrasonic time-of-flight-load-angle relationship function to the time-of-flight arrays under different loads and angles of the edge electrodes;

Step S4, when the bolt to be tested is actually working, measure the ultrasonic flight time of the center electrode and the edge electrode, first use the ultrasonic flight time of the center electrode and the calibration coefficient to obtain the maximum load at this time; then use the maximum load and the ultrasonic wave of the edge electrode The flight time and its function with the angle are solved, and the angle and direction of the random load are obtained.

In the above-mentioned ultrasonic measurement method of bolt random lateral load and its direction of action, S1, a physical vapor deposition method is used on the top or bottom of the bolt to be tested to prepare a layer of piezoelectric effect coating sensor, and the center of the upper surface of the sensor is A center electrode is prepared, and two edge electrodes are prepared on the edge of the center electrode, and the angle between the two edge electrodes relative to the center electrode is α, 0°<α<180°.

In the above-mentioned ultrasonic measurement method of a random transverse load of a bolt and its direction of action, in step S2, the gradient loading of the transverse load is first carried out on a standard stretching machine, and the loading gradient load is m*ΔF, m=0,1,2 , 3, 4, 5..., and then use the test data of the central electrode to perform fitting to obtain the load calibration coefficient, specifically record the ultrasonic flight time t ₀ when the central electrode load is 0 and the ultrasonic flight time t _m under each load , m=1, 2, 3, 4, 5..., fitting the relationship between ultrasonic flight time and load data, and obtaining the acoustic time t _m corresponding to the center electrode and the load calibration formula F=a ₀ *t _m +b ₀ , Among them, F is the lateral load applied in real time, and a ₀ and b ₀ are the calibration coefficients.

In the above-mentioned ultrasonic measurement method of a bolt random lateral load and its direction of action, in step S3, the steps for obtaining the relational function are:

Step S3.1, use the edge electrode test data to fit and obtain the load calibration coefficient: ensure that the No. 1 edge electrode is located in the loading direction of the stretching machine, and record the ultrasonic flight time t _1m of the next No. electrode and the No. Ultrasonic flight time t _2m , m=1,2,3,4,5...;

Step S3.2, fitting the relationship between ultrasonic flight time and load data, and obtaining the acoustic time t _1m corresponding to the No. 1 edge electrode and the load calibration formula F=a ₁₀ *t _1m +b ₁₀ , where F is the real-time applied lateral Load, a ₁₀ and b ₁₀ are the calibration coefficients of No. 1 edge electrode;

Step S3.3, use the edge electrode test data to construct the function of bolt angle and calibration coefficient: rotate the standard bolt by Δθ angle in turn, repeat step S4, and obtain the stress calibration coefficients a ₁₁ and b ₁₁ corresponding to each Δθ angle, the second edge The corresponding angle of the electrode is also denoted as θ; the model of lateral load size F, lateral load direction θ and flight time t _1m constructed by fitting is

F＝f ₁ (θ)*t _1m +g ₁ (θ)

where f ₁ (θ) is the fitting relationship between stress calibration coefficient a _1i and angle θ, g ₁ (θ) is the fitting relationship between stress calibration coefficient b _1i and angle θ, the fitting relationship is a sine function, then The model of the lateral load F of the No. 2 edge electrode, the lateral load direction θ and the flight time t _2m is

F＝f ₂ (θ)*t _2m +g ₂ (θ)

Where f ₂ (θ) is the fitting relationship between the stress calibration coefficient a _2i and the angle θ, g ₂ (θ) is the fitting relationship between the stress calibration coefficient b _2i and the angle θ, and the fitting relationship is a sine function.

In the above-mentioned ultrasonic measurement method of a random lateral load on a bolt and its direction of action, step S4 is actually detecting the in-service bolts that are subjected to a random load in the working state, and simultaneously measure the ultrasonic flight time _t of the central electrode and the ultrasonic flight time of the edge electrodes t _1m , t _2m , by substituting t _m into the center electrode calibration formula F=a ₀ *t _m +b ₀ , the value of the real-time applied load F can be obtained.

In the above-mentioned ultrasonic measurement method of a random lateral load of a bolt and its direction of action, in step S4, the edge electrode ultrasonic flight time t _1m and the applied load F are substituted into the No. 1 edge electrode calibration function F=f ₁ (θ)* t _1m + g ₁ (θ), the angles θ ₁ and θ ₂ of the load F relative to the No. 1 edge electrode can be obtained at this time, and the edge electrode ultrasonic flight time t _2m and the applied load F are substituted into the edge electrode calibration function F = f ₂ (θ)*t _2m +g ₂ (θ), _the angles θ ₃ and θ ₄ of the load F relative to the No. ₂ edge electrode can be obtained at this time. When the difference θ _{4 -θ 1} , θ ₄ -θ _{2 ,} θ ₃ -θ ₁ , θ ₃ -θ ₂ calculated by the second edge electrode is the angle α between the two edge electrodes, If θ ₃ -θ ₁ = α, it is considered that the direction of load action at this time is at the angle θ ₁ of the No. 1 edge electrode, that is, at the angle θ ₃ of the No. 2 electrode.

In the above-mentioned ultrasonic measurement method of bolt random lateral load and its direction of action, the sensor film of the array film sensor completely covers the upper surface or the lower surface, the shape of the center electrode is circular, and the shape of the edge electrodes has many choices. The number of electrodes is 2, and they cannot be symmetrically distributed relative to the center electrode;

In the above-mentioned ultrasonic measurement method of the random lateral load of the bolt and its direction of action, the maximum value of the gradient load does not exceed 80% of the shear strength of the bolt.

In the above-mentioned ultrasonic measurement method of random lateral load of bolts and its direction of action, the angle Δθ in step S3 is between 5°-15°.

The above one or more technical solutions in the embodiments of the present application have at least one or more of the following technical effects:

The present invention proposes a combination scheme of using one center coating sensor and two edge coating sensors, and for the first time realizes the synchronous measurement of the magnitude and direction of the transverse load of connecting parts such as bolts and fasteners that bear random transverse loads. The coating sensor located in the center will not be affected by the direction of the load, so it can be used to directly measure the magnitude of the load; the two coating sensors located on the edge are used to measure the possible load direction, and the difference between the two edge sensors solves the unique angle measurement. sexual issues. Only this technology can be used but not limited to bolt fasteners subjected to loads in random directions such as vehicle road noise and vibration, ocean wave erosion, etc., to achieve accurate measurement under complex loads, and to distinguish the direction of lateral loads in real time, Realize all-round judgment of stress.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are For some embodiments of the present invention, those skilled in the art can also obtain other drawings based on these drawings without creative work.

Figure 1a is a schematic diagram of the shape of the bolt and the sensor

Fig. 1b is a schematic diagram of the electrode arrangement on the top of the torsion bolt in Fig. 1a.

Figure 2 is a schematic diagram of the fixture and load action.

Figure 3 is a schematic diagram of edge electrode angle calibration.

Figure 4 is the acoustic time-load calibration curve of the center electrode.

Fig. 5 is two edge electrode angle-calibration coefficient fitting relationship curves.

Detailed ways

In order to solve the problem that existing fastener bolts cannot accurately measure the size and angle of lateral loads acting in random directions, resulting in the inability to realize real-time stress monitoring of bolt fasteners, the present invention proposes a random lateral load and its Ultrasonic measurement method of direction of action.

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

An ultrasonic measurement method for bolt random transverse load and its direction of action, comprising the following steps:

S1. Use the physical vapor deposition method on the top of the torsion bolt used in the spacecraft to prepare a layer of piezoelectric effect coating sensor. The shape of the bolt and the sensor is shown in Figure 1a and Figure 1b, and the center electrode is prepared in the center of the upper surface of the sensor. Two edge electrodes are prepared on the edge of the center electrode, and the angle between the two edge electrodes relative to the center electrode is α=90°. The laser cutting method can realize the processing of electrodes of various shapes.

S2. According to the actual working conditions, design a matching shear action fixture, and use a high-precision tensile testing machine or pin testing machine to carry out gradient loading of lateral loads. The shape and loading method of the fixture are shown in Figure 2. After keeping the load stable for a period of time, the measurement is carried out, the loading gradient load is 5000N, and the maximum load is 35kN.

S3. Use the ultrasonic measuring instrument to collect the ultrasonic signals of the center electrode and the edge electrode, and use the test data of the center electrode to perform fitting to obtain the load calibration coefficient: record the ultrasonic flight time t ₀ when the center electrode load is 0 and each in the range of 0-35kN The ultrasonic flight time t _m under the gradient is used to fit the relationship between the ultrasonic flight time and the load data, and the acoustic time and load calibration formula F=a ₀ *t _m +b ₀ corresponding to the center electrode is obtained, as shown in Figure 4.

S4. Use the edge electrode test data to fit and get the load calibration coefficient: ensure that the No. 1 edge electrode is located in the loading direction of the stretching machine, and record the ultrasonic flight time t _1m and the No. 2 electrode under each gradient within the range of 0-35kN in sequence Ultrasonic flight time t _2m of the electrode.

S5. Fitting the relationship between the ultrasonic flight time and the load data, and obtaining the acoustic time and load calibration formula F=a ₁₀ *t _1m +b ₁₀ corresponding to the No. 1 edge electrode.

Use the edge electrode test data to construct the function of bolt angle and calibration coefficient: rotate the standard bolt Δθ=10° in turn, repeat step S4 to obtain the stress calibration coefficients a ₁₁ and b ₁₁ corresponding to each θ angle, and the corresponding angle of the second edge electrode Also denoted as θ;; the model of lateral load size F, lateral load direction θ and flight time t _1m constructed by fitting is

F＝f ₁ (θ)*t _1m +g ₁ (θ)

Where f ₁ (θ) is the fitting relationship between the stress calibration coefficient a _1i and the angle θ, g ₁ (θ) is the fitting relationship between the stress calibration coefficient b _1i and the angle θ, using f ₁ (θ)=a _1i =y ₁ +A ₁ sin[π(xx ₁ )/w ₁ ], g ₁ (θ) is fitted using a quadratic or cubic polynomial.

S6. Obtain the model of No. 2 edge electrode lateral load size F, lateral load direction θ and flight time t _2m as

F＝f ₂ (θ)*t _2m +g ₂ (θ)

Where f ₂ (θ) is the fitting relationship between the stress calibration coefficient a _2i and the angle θ, g ₂ (θ) is the fitting relationship between the stress calibration coefficient b _2i and the angle θ, using f ₂ (θ)=a _2i =y ₂ +A ₂ sin[π(xx ₂ )/w ₂ ], g ₂ (θ) is fitted using a quadratic or cubic polynomial, and the f(θ) curves of the two edge electrodes are shown in Figure 5.

S7. Carry out the actual detection of the in-service bolts under random loads in the working state, and measure the ultrasonic flight time t _m of the center electrode and the ultrasonic flight time t _1m and t _2m of the edge electrodes at the same time, by substituting t _m into the center electrode calibration formula F in the attached drawing 4 ＝a ₀ *t _m +b ₀ , it can be obtained that the real-time applied load F＝32kN;

S8. Substituting the ultrasonic flight time t _1m of the edge electrode and the applied load F=32kN into the calibration function F=f ₁ (θ)*t _1m +g ₁ (θ) of the edge electrode No. 1, the load F can be obtained at this time relative to a The angle θ ₁ =72° and θ ₂ =-59° of the edge electrode action, the edge electrode ultrasonic flight time t _2m and the time load F=32kN are substituted into the edge electrode calibration function F=f ₂ (θ)*t _2m + g ₂ (θ), the angle θ _{3 =} 19° and θ ₄ = 167° of the load F relative to the No. The value of θ ₄ =167° difference θ ₄ -θ ₁ calculated by the edge electrodes is 95°, which is similar to the angle α=90° between the two edge electrodes. It is considered that the direction of the load at this time is 72° to the number one edge electrode °, that is, the 167° of the second electrode.

Claims (7)

1. An ultrasonic measurement method for random transverse loads and action directions of bolts is characterized by comprising the following steps:

s1, preparing thin film coating sensors distributed at the center and the edge at the top or the bottom of a bolt to be detected;

s2, calibrating the sound time and the load of the central electrode to obtain a load calibration coefficient of the central electrode;

s3, fitting a flight time array of the edge electrode under different loads and different angles to obtain an ultrasonic flight time-load-angle relation function;

s4, when the bolt to be tested actually works, measuring the ultrasonic flight time of the central electrode and the edge electrode, and obtaining the maximum load at the moment by utilizing the ultrasonic flight time and the calibration coefficient of the central electrode; solving by utilizing the maximum load, the ultrasonic flight time of the edge electrode and a function of the ultrasonic flight time and the angle to obtain the random load action angle and direction;

in the step S1, a physical vapor deposition method is used at the top or the bottom of a bolt to be detected to prepare a layer of sensor with a piezoelectric effect coating, a central electrode is prepared at the center of the upper surface of the sensor, two edge electrodes are prepared at the edges of the central electrode, the included angle of the two edge electrodes relative to the central electrode is alpha, and the angle is more than 0 degrees and less than 180 degrees;

in step S3, the obtaining step of the relation function is:

s3.1, fitting by using the edge electrode test data to obtain a load calibration coefficient: ensuring that the first edge electrode is positioned in the loading direction of the stretcher, and sequentially recording the ultrasonic flight time t of the first electrode under each load _1m Ultrasonic time of flight t with second electrode _2m ，m＝1,2,3,4,5……；

S3.2, fitting the relation between the ultrasonic flight time and the load data to obtain the acoustic time t corresponding to the No. 1 edge electrode _1m And load calibration formula F = a ₁₀ *t _1m +b ₁₀ Wherein F is a transverse load applied in real time, a ₁₀ 、b ₁₀ The calibration coefficient of the first edge electrode is obtained;

s3.3, constructing a bolt angle and calibration coefficient function by using the edge electrode test data: sequentially rotating the standard sample bolt by delta theta angles, and repeating the step S4 to obtain the stress calibration corresponding to each delta theta angleCoefficient a ₁₁ And b ₁₁ The corresponding angle of the second edge electrode is also marked as theta; construction of lateral load magnitude F, lateral load direction θ and time of flight t by fitting _1m Is modeled as

F＝f ₁ (θ)*t _1m +g ₁ (θ)

Wherein f is ₁ (theta) is a stress calibration coefficient a _1i Fitting relation with angle theta, g ₁ (theta) is a stress calibration coefficient b _1i Fitting relation with angle theta, wherein the fitting relation is a sine function, and then the transverse load magnitude F, the transverse load direction theta and the flight time t of the second edge electrode _2m Is modeled as

F＝f ₂ (θ)*t _2m +g ₂ (*)

Wherein f is ₂ (theta) is a stress calibration coefficient a _2i Fitting relation with angle theta, g ₂ (theta) is a stress calibration coefficient b _2i And fitting the angle theta, wherein the fitting relation is a sine function.

2. The ultrasonic measurement method for the random transverse load and the acting direction of the bolt according to claim 1, wherein in step S2, gradient loading of the transverse load is performed on a standard stretcher, the gradient loading is m × Δ F, m =0,1,2,3,4,5 … …, and then fitting is performed by using central electrode test data to obtain a load calibration coefficient, specifically, the ultrasonic flight time t when the central electrode load is 0 is recorded ₀ And ultrasonic time of flight t at each load _m M =1,2,3,4,5 … …, and the relation between the ultrasonic flight time and the load data is fitted to obtain the acoustic time t corresponding to the central electrode _m And load calibration formula F = a ₀ *t _m +b ₀ Wherein F is a transverse load applied in real time, a ₀ 、b ₀ Is a calibration coefficient.

3. The ultrasonic measurement method for the random transverse load and the acting direction of the bolt according to claim 2, wherein step S4 is implemented for the actual detection of the bolt in service which bears the random load in the working stateSimultaneously measuring the ultrasonic time of flight t of the central electrode _m Ultrasonic time of flight t with edge electrode _1m 、t _2m By mixing t _m Substituting the center electrode calibration formula F = a ₀ *t _m +b ₀ And obtaining the value of the real-time acting load F.

4. The ultrasonic measurement method for the random transverse loads and the acting directions of the random transverse loads of the bolts according to claim 3, wherein in the step S4, the ultrasonic flight time t of the edge electrode is determined _1m Substituting time acting load F into edge electrode calibration function I F = F ₁ (θ)*t _1m +g ₁ (theta) obtaining the angle theta of the load F acting against the first edge electrode at that time ₁ And theta ₂ Ultrasonic time of flight t of edge electrode _2m Substituting the time action load F into the edge electrode calibration function F = F ₂ (θ)*t _2m +g ₂ (theta) obtaining the angle theta of the load F acting against the second edge electrode at the moment ₃ And theta ₄ Theta when calculated for the first edge electrode ₁ Or theta ₂ Theta obtained from edge electrode II ₃ Or theta ₄ Difference of difference theta ₄ -θ ₁ 、θ ₄ -θ ₂ 、θ ₃ -θ ₁ 、θ ₃ -θ ₂ When the value of (a) is the angle alpha between the two edge electrodes, e.g. theta ₃ -θ ₁ (= α), θ) of edge electrode with the direction of load applied at this time being one ₁ At an angle, i.e. theta for electrode number two ₃ At an angle.

5. The ultrasonic measurement method of the random transverse load and the acting direction of the random transverse load of the bolt as claimed in claim 4, wherein the sensor film of the array film sensor completely covers the upper surface or the lower surface, the shape of the central electrode is circular, the shape of the edge electrode has more choices, the number of the edge electrodes is 2, and the sensor film cannot be distributed in central symmetry relative to the central electrode.

6. The ultrasonic measurement method for the random transverse load and the acting direction of the bolt according to claim 5, wherein the maximum value of the gradient load is not more than 80% of the shear strength of the bolt.

7. The ultrasonic method for measuring the random transverse load of the bolt and the acting direction of the random transverse load according to claim 6, wherein the angle delta theta in the step S3 is between 5 degrees and 15 degrees.

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