Ultrasonic calculation method of axial stress of in-service bolts considering temperature

Abstract

The present invention relates to the technical field of bolt axial stress measurement, and specifically to an ultrasonic calculation method for the axial stress of an in-service bolt taking temperature into consideration. When the ultrasonic wave propagates in the in-service bolt, the temperature of the in-service bolt itself is changed, and the current equivalent temperature of the in-service bolt is calculated through the temperature equivalent model; then the ultrasonic wave's transit time ratio is calculated based on the equivalent temperature; finally, the axial stress of the in-service bolt at the current equivalent temperature is calculated according to the axial stress model. Based on the above operations, the method of the present invention can accurately calculate the axial stress of the in-service bolt at various temperatures, and then provide accurate data support for the evaluation of the service status of the in-service bolt at various temperatures, so as to improve the accuracy of the evaluation.

Description

Technical Field

[0001] The invention relates to the technical field of bolt axial stress measurement, in particular to an ultrasonic calculation method for the axial stress of an in-service bolt taking temperature into consideration. Background Art

[0002] Bolts are one of the important fasteners and are widely used because of their advantages such as easy assembly and disassembly, and easy maintenance. When the in-service bolts are connected to the connecting equipment, axial stress will be generated. When the axial stress of the in-service bolts is too large, fatigue cracks are likely to occur. When the axial stress is too small, the connection strength is insufficient. Therefore, it is very necessary to determine the tightness and safety of the in-service bolt connection by measuring the axial stress of the in-service bolts.

[0003] Traditional methods for detecting axial stress of in-service bolts usually use torque wrench method, strain gauge method, etc. The torque wrench method can only be used for tightening control of in-service bolts, and this method is easily affected by the friction between the connection surfaces of in-service bolts, resulting in low measurement accuracy. The use of the strain gauge method is limited by the instrument and installation conditions, and this method is mostly used for stress calculation in the laboratory.

[0004] In order to avoid the influence of the above-mentioned prior art, patent CN115855331A discloses a method for measuring the axial force of an in-service bolt based on the absolute acoustic time ratio of ultrasonic transverse and longitudinal waves. The method comprises the following steps: 1. Measuring the ultrasonic stress detection system

[0005] 1. Select in-service bolts with the same material and heat treatment method as the in-service bolts for laboratory calibration to obtain the absolute acoustic time ratio of transverse and longitudinal waves and the double-wave stress coefficient under zero stress; 2. Obtain the external dimensions of the in-service bolts and use ultrasonic wave to calibrate the bolts.

[0006] The force detection system obtains the absolute acoustic time of the transverse wave and the absolute acoustic time of the longitudinal wave of the in-service bolt after deducting the system delay; 4. The measured absolute acoustic time is temperature corrected to obtain the corrected absolute acoustic time ratio of the transverse and longitudinal waves; 5. The double-wave stress coefficient of the in-service bolt obtained in step 2 is corrected; 6. The absolute acoustic time ratio of the transverse and longitudinal waves of the in-service bolt under zero stress obtained in step 2 is corrected; 7. The axial force of the in-service bolt is obtained according to the corrected absolute acoustic time ratio of the transverse and longitudinal waves under zero stress and the double-wave stress coefficient in steps 5 and 6.

[0007] The above-mentioned measurement method has the advantages of not damaging the in-service bolts themselves and being quick and simple to operate, so it is widely used. In the process of measuring the axial stress of in-service bolts by the dual-wave method, the change in temperature has a great influence on the measurement of the transit time, and the transit time calculated at different temperatures is also different. However, the above-mentioned prior art does not consider the influence of temperature on the measurement of transit time, that is, when measuring the transit time, it is assumed that the temperature of the in-service bolts is constant, which will lead to the problem of using the calculation results of the same temperature to represent the calculation results at various temperatures. This kind of sweeping approach does not conform to the actual calculation of the axial stress of in-service bolts, and thus makes it impossible to calculate the true axial stress of in-service bolts at various temperatures. It can be seen that the current method of calculating the axial stress of in-service bolts needs to focus on the influence of temperature changes in order to accurately calculate the axial stress of in-service bolts that conforms to the actual situation. Summary of the invention

[0008] In order to avoid and overcome the technical problems existing in the prior art, the present invention provides an ultrasonic calculation method for the axial stress of an in-service bolt taking temperature into consideration. The method of the present invention can more accurately calculate the axial stress of an in-service bolt at various temperatures.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] The ultrasonic calculation method of the axial stress of in-service bolts considering temperature includes the following calculation steps:

[0011] S1. Apply ultrasonic waves propagating along the axial direction of the in-service bolts under axial force.

[0012] S2. Changing the temperature of the in-service bolt itself and obtaining the sound velocity of the ultrasonic longitudinal wave and ultrasonic transverse wave in the ultrasonic wave propagating on the in-service bolt;

[0013] S3. Based on the sound velocity of the ultrasonic longitudinal wave and the sound velocity of the ultrasonic transverse wave, the current equivalent temperature of the in-service bolt itself is calculated in the temperature equivalent model;

[0014] S4. Calculate the equivalent transit time ratio of ultrasonic longitudinal wave and ultrasonic shear wave according to the equivalent temperature of the in-service bolt;

[0015] S5. Input the equivalent transit time ratio into the axial stress model to calculate the axial stress of the in-service bolt at the current equivalent temperature.

[0016] As a further solution of the present invention: after measuring the temperature of the in-service bolt, the sound velocity of the ultrasonic longitudinal wave at the current temperature is calculated by the ultrasonic longitudinal wave sound velocity calculation formula, and then the sound velocity of the ultrasonic shear wave at the current temperature is calculated by the ultrasonic shear wave sound velocity calculation formula;

[0017] The calculation formula of ultrasonic longitudinal wave speed is as follows:

[0018] ;

[0019] In the formula, Indicates that the in-service bolts subjected to axial stress are at a temperature of T When , the sound velocity of ultrasonic longitudinal wave propagating in the in-service bolt; superscript Z Indicates that the wave is an ultrasonic longitudinal wave, the subscript σ - T Indicates that the sound velocity of the wave is also subject to axial stress σ

[0020] and temperature T The impact of Indicates that the in-service bolts are at a temperature of T When , the elastic modulus of the in-service bolt; Indicates that the in-service bolts are at a temperature of T When , the Poisson's ratio of the in-service bolt; Indicates that the in-service bolts are at a temperature of T When , the density of the in-service bolt;

[0021] The ultrasonic shear wave speed calculation formula is as follows:

[0022] ;

[0023] In the formula, Indicates that the in-service bolts subjected to axial stress are at a temperature of T When , the sound velocity of ultrasonic shear wave propagating in the in-service bolt; superscript H Indicates that the wave is an ultrasonic shear wave.

[0024] As a further solution of the present invention: by solving the equation of the temperature equivalent model, the corresponding equivalent temperature can be obtained; the temperature equivalent model is expressed as follows:

[0025] ;

[0026] In the formula, Indicates the axial stress of the in-service bolt σ Length under action; x Indicates that along the axial direction of the in-service bolt, the in-service bolt

[0027] The axial distance from a point in the bolt to the end face of the in-service bolt that emits the ultrasonic wave; T x Indicates that among the bolts in service, x The temperature at Indicates that the in-service bolts subjected to axial stress are at a temperature of T x point x At this point, the ultrasonic longitudinal wavex The speed of sound propagating at l x Indicates at point x At a point x is the length of the neighborhood of the neighborhood center; d Indicates the differential sign; T eqv Indicates the equivalent temperature of the bolt in service; Indicates that the in-service bolts subjected to axial stress are at a temperature of T eqv When the ultrasound

[0028] The speed of sound at which the wave propagates in the in-service bolt.

[0029] As a further solution of the present invention: the equivalent transit time ratio of ultrasonic longitudinal wave and ultrasonic shear wave is calculated by the equivalent transit time ratio calculation formula, and the equivalent transit time ratio calculation formula is expressed as follows:

[0030] ;

[0031] In the formula, Indicates that the in-service bolts subjected to axial stress are at a temperature of T eqv The ratio of the transit sound time of the ultrasonic longitudinal wave and the ultrasonic transverse wave propagating in the in-service bolt is recorded as the equivalent transit sound time ratio; Indicates that the in-service bolts subjected to axial stress are at a temperature of T eqv When the ultrasonic longitudinal wave propagates in the in-service bolt, the transit acoustic time is recorded as the equivalent transit acoustic time of the ultrasonic longitudinal wave; Indicates that the in-service bolts subjected to axial stress are at a temperature of T eqv When the ultrasonic shear wave propagates in the in-service bolt, the transit acoustic time is recorded as the equivalent transit acoustic time of the ultrasonic shear wave; It means that the in-service bolts subjected to axial stress are at room temperature.

[0032] The sound velocity of the ultrasonic longitudinal wave propagating in the in-service bolt; Indicates that the in-service bolts subjected to axial stress are at a temperature of T eqv The sound velocity of ultrasonic shear wave propagating in the in-service bolt at ; Indicates the temperature of the in-service bolts subjected to axial stress.

[0033] The speed of sound of ultrasonic shear waves propagating in the in-service bolt when the temperature is normal.

[0034] As a further solution of the present invention: the equivalent transit acoustic time of ultrasonic longitudinal waves is calculated by the equivalent transit acoustic time calculation formula of ultrasonic longitudinal waves. The equivalent transit acoustic time calculation formula of ultrasonic longitudinal waves is as follows:

[0035] ;

[0036] The equivalent transit time of ultrasonic shear waves is calculated by the equivalent transit time calculation formula of ultrasonic shear waves. The equivalent transit time calculation formula of ultrasonic shear waves is as follows:

[0037] .

[0038] As a further solution of the present invention: when the temperature of the in-service bolt itself is room temperature, the sound velocity of the ultrasonic longitudinal wave propagating in the in-service bolt is calculated by the corresponding sound velocity calculation formula, and the sound velocity calculation formula is expressed as follows:

[0039] ;

[0040] ;

[0041] In the formula, It indicates the sound velocity of ultrasonic longitudinal waves propagating in the in-service bolt that is not subjected to axial stress and is at room temperature; It means that when the service bolt which is not subjected to axial stress is at room temperature, the ultrasonic shear wave will

[0042] The speed of sound propagation; the subscript 0 means that the in-service bolt is not subjected to axial stress; k Z Represents the acoustic elastic coefficient of ultrasonic longitudinal waves; k H Represents the acoustoelastic coefficient of ultrasonic shear waves.

[0043] As a further solution of the present invention: the axial stress model is expressed as follows:

[0044] ;

[0045] In the formula, σ ( T eqv ) indicates that the in-service bolts are at a temperature of T eqv , the axial stress.

[0046] As a further solution of the present invention: the in-service bolt is subjected to axial stress σ Length under action L σ The calculation formula is as follows:

[0047] ;

[0048] In the formula, E It indicates the elastic modulus of the in-service bolt material at room temperature. L 0 It indicates the length of the in-service bolt when it is not subjected to axial stress and is at room temperature.

[0049] Axial stress of bolts in service Length under action The calculation formula is as follows:

[0050] ;

[0051] In the formula, E It indicates the elastic modulus of the in-service bolt material at room temperature. It indicates the length of the in-service bolt when it is not subjected to axial stress and is at room temperature.

[0052] An electronic device comprises a processor, an input device, an output device and a memory, wherein the processor, the input device, the output device and the memory are connected in sequence, the memory is used to store a computer program, the computer program comprises program instructions, and the processor is configured to call the program instructions to execute the above method.

[0053] A storage medium stores a computer program, wherein the computer program includes program instructions, and when the program instructions are executed by a processor, the processor executes the above method.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] When ultrasonic waves propagate in the in-service bolts, they change the temperature of the in-service bolts themselves, and the current equivalent temperature of the in-service bolts is calculated through the temperature equivalent model; then the ultrasonic sound time ratio is calculated based on the equivalent temperature; finally, the axial stress of the in-service bolts at the current equivalent temperature is calculated according to the axial stress model. Based on the above operations, the axial stress of the in-service bolts at various temperatures can be accurately calculated, thereby providing accurate data support for the evaluation of the service status of the in-service bolts at various temperatures, so as to improve the accuracy of the evaluation. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is the main flow chart of the method of the present invention.

[0057] Figure 2 It is a schematic diagram of the propagation of ultrasonic waves in a bolt in the present invention.

[0058] Figure 3 This is a temperature distribution cloud diagram of the flange joint when the inner wall is at 200°C in the present invention.

[0059] Figure 4 This is a cloud diagram of bolt temperature distribution when the inner wall is at 200°C in the present invention.

[0060] Figure 5 This is a temperature distribution cloud diagram of the bolt center section when the inner wall is at 200°C in the present invention.

[0061] Figure 6 It is a one-dimensional axial temperature distribution curve diagram of the bolt in the present invention.

[0062] Figure 7 It is a structural schematic diagram of the flange joint in the present invention.

[0063] Figure 8 This is a diagram of the arrangement of thermocouples in the flange structure of the present invention.

[0064] Fig. 9 It is a comparison chart of temperature distribution results in the experiment and simulation in the present invention.

[0065] Fig.10 It is a schematic diagram of the electronic device framework in the present invention.

[0066] In the figure: 10, electronic device; 11, processor; 12, memory; 13, input device; 14, output device; 20, lower flange; 21, gasket; 22, bolt; 23, upper flange; 24, heating tube. DETAILED DESCRIPTION

[0067] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0068] See also Figures 1 to 10 In an embodiment of the present invention, an ultrasonic calculation method for axial stress of in-service bolts considering temperature includes the following contents.

[0069] 1. Principle of ultrasonic double-wave measurement of axial stress of in-service bolts.

[0070] The ultrasonic method for measuring the axial stress of in-service bolts is mainly divided into the single-wave method and the dual-wave method. The single-wave method only uses ultrasonic longitudinal waves. It is necessary to measure the acoustic wave transit time of the in-service bolt in the stress-free state and the acoustic wave transit time of the in-service bolt in the stress state, calculate the acoustic time difference between the two, and then obtain the axial stress of the in-service bolt. The dual-wave method combining longitudinal and transverse waves is based on the common relationship between the axial stress of the in-service bolt and the propagation sound time of the longitudinal and transverse waves to eliminate the variable of the in-service bolt length. It can realize the axial stress measurement of in-service bolts of unknown length, which is easy to calibrate and suitable for field conditions. When the two ends of the in-service bolt are subjected to axial tensile stress, the schematic diagram of the propagation of ultrasonic waves in the in-service bolt is shown in Figure 2.

[0071] According to the theory of acoustic elasticity, stress in a material changes its elastic behavior, so the speed of ultrasound can be linked to the stress state in the material. For isotropic homogeneous materials, the speeds of ultrasonic longitudinal waves and ultrasonic shear waves propagating in the same direction as the applied stress are linearly related, namely:

[0072] (1-1);

[0073] (1-2);

[0074] Since both longitudinal and transverse waves are incident vertically into the in-service bolt, the angle between the center of the sound beam and the axis of the in-service bolt is very small, so the longitudinal and transverse wave transit time can be expressed as:

[0075] (2-1);

[0076] (2-2);

[0077] In the formula, It indicates the transit sound time of ultrasonic longitudinal wave propagating in the in-service bolt under axial stress when the temperature is at room temperature. It indicates the transit sound time of ultrasonic shear waves propagating in a service bolt subjected to axial stress when the temperature is at room temperature.

[0078] Compare the transit time of ultrasonic longitudinal wave with the transit time of ultrasonic transverse wave, and make Taylor expansion for the comparison result. The details are as follows:

[0079]

[0080] (3);

[0081] In the formula, represents the remainder of the Taylor expansion.

[0082] Ignoring the higher-order terms and remainders in the Taylor expansion, it is approximately assumed that the transit time ratio and stress have a linear relationship:

[0083] (4);

[0084] Based on formula (4), the relationship between the axial stress of the in-service bolt and the transit time ratio is as follows:

[0085] (5);

[0086] It can be seen from formula (5) that the magnitude of axial stress is linearly related to the acoustic time ratio of longitudinal and transverse waves. For different in-service bolt materials, the specific values ​​of each parameter in formula (5) can be obtained through room temperature calibration experiments.

[0087] 2. Model correction based on equivalent temperature.

[0088] Under the influence of temperature, on the one hand, the in-service bolts will expand thermally and increase in length. On the other hand, the temperature increase will also cause the transverse and longitudinal wave speeds to decrease, both of which will cause the transit time to become longer. The double-wave calculation model of formula (5) is obtained at room temperature and does not consider the effect of temperature on the transit time. When measuring the axial stress of high-temperature in-service bolts, in order to improve the measurement accuracy, the model needs to be corrected. At the same time, there is a common phenomenon of uneven temperature distribution in in-service bolts. If the end surface temperature of the in-service bolts is simply used for calculation, it will also cause errors in the measurement results.

[0089] Therefore, considering the temperature distribution state in the in-service bolts and the influence of temperature on the ultrasonic velocity, an equivalent temperature calculation method is used. Its physical meaning is that the transit time of the in-service bolts at this temperature is the same as that in the state of uneven temperature distribution. The model is modified according to the equivalent temperature to improve the calculation accuracy of the axial stress of the in-service bolts.

[0090] For in-service bolts made of metal materials of common specifications, the influence of their wave velocity on the transit acoustic time is much greater than the influence of the thermal expansion deformation of the in-service bolts on the acoustic time measurement, so in this embodiment, only the influence of temperature on the wave velocity is considered. T When , the relationship between ultrasonic longitudinal and transverse wave speed and material properties is as follows:

[0091] (6-1);

[0092] (6-2);

[0093] in, , and All can be obtained through experimental measurement.

[0094] Since the temperature difference of the in-service bolts is mainly concentrated in the axial direction, and the sound wave is excited at one end of the in-service bolt and propagates along the axial direction of the in-service bolt to the other end, the in-service bolt model can be simplified to a one-dimensional model with only axial temperature difference. The temperature of the in-service bolt is related to the position, so the calculation formula for the transit time of the longitudinal and transverse sound waves in the in-service bolt is:

[0095] (7-1);

[0096] (7-2);

[0097] In the formula, Indicates that the in-service bolts subjected to axial stress are at a temperature of varying temperature. T act When the ultrasonic longitudinal wave propagates in the in-service bolt, the transit sound is Indicates that the in-service bolts subjected to axial stress are at a temperature of varying temperature. T act When the ultrasonic shear wave propagates in the service bolt, the transit sound is

[0098] On the other hand, when the equivalent temperature of the in-service bolt is used to calculate the transit time, the transit time is:

[0099] (8-1);

[0100] (8-2);

[0101] Formula (7-1) and formula (8-1) are combined to form a temperature equivalent model. By solving the temperature equivalent model, the corresponding equivalent temperature can be obtained. T eqv .

[0102] At the same time, for ultrasonic measurement of axial stress of in-service bolts at high temperature, the sound-time ratio in the model needs to be corrected. The equivalent transit sound-time ratio of in-service bolts can be written as:

[0103] (9);

[0104] By combining formula (5) and formula (9), we can obtain the axial stress model of the in-service bolt at the corresponding equivalent temperature. The axial stress model is expressed as follows:

[0105] (10);

[0106] 3. Calculation of axial stress model example.

[0107] In order to verify the correctness of the model, the material of the in-service bolt is selected as the high-strength alloy structure 35CrMoA, which has stable performance at high temperatures and is a commonly used in-service bolt material in high-load working scenarios in the petrochemical industry. Experiments are carried out to calibrate the acoustic elastic coefficient of this material. The specifications of the in-service bolts are M30×200mm. The two ends of the in-service bolts are polished to ensure good coupling between the probe and the in-service bolts. The in-service bolts are clamped on the in-service bolt fixture to simulate the pre-tightening conditions of the in-service bolts. The SHT-4206 universal testing machine is used to apply a specified axial tensile force to the in-service bolts. Its maximum loading capacity is 2000kN, and the test force resolution is 1 / 300000 of the full scale, which meets the experimental requirements.

[0108] The experiment uses longitudinal wave and shear wave piezoelectric ultrasonic probes, both with a center frequency of 5MHz, and a special coupling agent. The longitudinal wave and shear wave piezoelectric ultrasonic probes are fixed on one end of the in-service bolt.

[0109] The ultrasonic testing device uses an open ultrasonic acquisition module commonly used in the prior art, with adjustable signal gain, which can collect and save longitudinal and transverse wave transit times in real time. An ultrasonic probe is installed on the top of the in-service bolt, and the in-service bolt is fixed between the upper and lower in-service bolt fixtures in the universal testing machine, and the ultrasonic acquisition module is connected to the probe.

[0110] The load applied in the experiment should be controlled within the elastic range of the in-service bolt material. For the calibrated in-service bolt, its strength grade is 10.9, the tensile strength is 1000MPa, and the yield strength is 900MPa. The loading interval of the experiment in this embodiment is selected as the range of 0-80% of the yield strength, that is, the axial load of the in-service bolt is 0-720MPa, the loading step is selected as 80MPa, and the loading speed is 1MPa / s. Each group of in-service bolt loading experiments is repeated three times, and the average value of the three measurements is taken as the final result. The experimental result data is shown in Table 1.

[0111] Table 1 Measurement results of the calibration sound time of in-service bolts

[0112] ;

[0113] From the data in Table 1, we can see that when the stress increases by 80 MPa, the transit time of longitudinal waves increases by an average of 0.08 us, and the transit time of transverse waves increases by an average of 0.054 us. It can be seen that compared with transverse waves, longitudinal waves are more sensitive to changes in axial stress.

[0114] In order to calculate the equivalent temperature of the in-service bolts, it is necessary to first accurately obtain the temperature field distribution of the in-service bolts in the flange structure. Due to the limitations of the use of piezoelectric ultrasonic probes and coupling agents, the maximum temperature of the flange in this embodiment is 200°C.

[0115] The DN80 flange joint structure model was established by physical field simulation software. The in-service bolt material is 35CrMoA and the flange material is 316L stainless steel. Since the flange connection structure has symmetric characteristics, in order to reduce the amount of calculation and improve the calculation efficiency, this embodiment only takes 1 / 4 of the flange structure model. The mesh division adopts free tetrahedron units, and in order to ensure the calculation accuracy, the mesh density of the in-service bolt component is increased.

[0116] The inner wall of the flange is set to 100℃, 150℃ and 200℃ respectively, the ambient temperature is 20℃, and the flange is not insulated. The temperature distribution law of the in-service bolts is studied respectively. Thin layer boundary conditions are added to the contact boundaries of the flange components to simulate the thin air gap between the parts, which can realize the convection and radiation heat transfer between different components. Because the temperature distribution results of the flange joint and the in-service bolts are similar under different inner wall temperatures, there are only numerical differences. Therefore, only the temperature distribution of the flange and the in-service bolts under the condition of the highest inner wall temperature of 200℃ is shown here, as shown in the figure. Figure 3 and Figure 4 shown.

[0117] Depend on Figure 3 and Figure 4 From the distribution cloud diagram, it can be seen that the temperature gradually decreases from the inner wall to the outside of the flange structure, forming an obvious temperature gradient. There is also an obvious temperature difference between the flange and the in-service bolts. The highest temperature of the in-service bolts is located in the in-service bolt hole of the flange. This position is directly affected by the heat radiation of the inner wall of the in-service bolt hole, and the surrounding air temperature is high, and the heat dissipation conditions are poor; the lowest temperature is at the top of the in-service bolt, which has a large heat exchange area, good heat exchange conditions, more sufficient convection heat exchange, and greater heat loss.

[0118] Take the center section of the in-service bolt through the center line of the flange, and its temperature distribution is as follows Figure 5 The corresponding curve diagram is shown in Figure 6 Analysis of the temperature distribution characteristics of the in-service bolts shows that the temperature difference of the in-service bolts is concentrated in the axial direction of the in-service bolts, while in the circumferential section of the in-service bolts, the temperature distribution difference of the in-service bolts is small, which is consistent with the assumptions in the previous model and provides a basis for simplifying the in-service bolts into a one-dimensional model with only axial temperature difference.

[0119] In order to verify the accuracy of the simulation, the flange joint is designed and processed as shown in FIG7. The flange joint includes a cylindrical support base, and the lower flange 20 is coaxially sleeved on the outer side of the support base and fixedly connected to the support base. The upper flange 23 is fixedly connected to the upper side of the lower flange 20 by the in-service bolts 22, and the upper flange 23 is coaxially detachably sleeved on the support base. Four heating tubes 24 arranged parallel to each other are evenly distributed inside the support base to simulate the high-temperature working medium inside the flange. The upper flange 23 and the lower flange 20 are coaxially provided with positioning grooves for cutting off the in-service bolt holes, and a gasket 21 for buffering is coaxially fixed in the positioning groove. A temperature-controlled thermocouple is pasted on the inner wall of the flange, and the thermocouple is connected to the temperature meter to collect and control the internal temperature of the flange in real time. The gasket 21 is a graphite wound gasket, and the specifications of the in-service bolts 22 are 8 M20×140mm studs. The experimental conditions are kept consistent with the boundary conditions in the simulation.

[0120] In the experiment, 9 thin-film K-type thermocouples were pasted on different positions of the in-service bolts, such as Figure 8 As shown, Figure 8 The star pattern in the figure represents a thin-film K-type thermocouple, which is used to accurately obtain the surface temperature of the in-service bolts in the flange structure. 1 and T 2 Symmetrically arranged between the in-service bolts and nuts, T 3 , T 4 , T 5 , T 6 They are located at the center of the in-service bolts and distributed at 90° along the circumference of the in-service bolts. 7 , T 8 They are located between the in-service bolt hole and the in-service bolt of the flange. This is where the surface temperature of the in-service bolt is the highest in the simulation results. 9 Located at the top of the in-service bolt, this is where the surface temperature of the in-service bolt is the lowest in the simulation results.

[0121] The measured temperature results at each point are as follows Fig. 9 As shown, the highest temperature is T 7 , the lowest temperature is T 9 , T within the same in-service bolt section 3 , T 4 , T 5 , T 6 The temperature difference at the bolts is not big. The temperature distribution law of the in-service bolts in the experimental and simulation results is basically consistent, so the simulation results can be considered reliable.

[0122] The ultrasonic measurement results were compared with the strain gauge measurement results to verify the calculation accuracy of the above model. The strain gauge was pasted on the in-service bolt. To ensure the measurement accuracy of the strain gauge and reduce the influence of the in-service bolt deflection on the measurement results, the strain gauges were installed symmetrically on both sides of the in-service bolt at 180° apart. The average value of the two was taken as the measurement result. At the same time, the in-service bolt strain signal was recorded and saved through a multi-channel strain data acquisition instrument.

[0123] In the above flange experiment, the temperature of the inner wall of the flange was raised to 100℃, 150℃, and 200℃ respectively, and the longitudinal and transverse wave transit sound time and strain gauge results of the in-service bolts were obtained, and the axial stress of the in-service bolts was calculated respectively. At the same time, the stress results measured by ultrasonic method were corrected by using the end surface temperature and equivalent temperature of the in-service bolts, and the deviation from the strain gauge measurement results was calculated. The results are shown in Table 2. Where T represents the temperature of the inner wall of the flange, t L represents the time when the longitudinal wave transits the sound; t S represents the transverse wave transit time; t L / S Represents the ratio of the transit time of longitudinal and transverse waves. (sur)L / S Represents the ratio of the longitudinal and transverse wave transit times using the end surface temperature. (eqv)L / S Represents the ratio of the transit time of longitudinal and transverse waves at equivalent temperature. sur Represents the calculated value of the bolt axial stress using the end surface temperature correction. eqv Represents the calculated value of the bolt axial stress using equivalent temperature correction. δ sur Represents the relative deviation between the calculated value of the bolt axial stress corrected by the end surface temperature and the theoretical value. eqv Represents the relative deviation between the calculated value of the bolt axial stress using equivalent temperature correction and the theoretical value.

[0124] Table 2 Stress measurement results of in-service bolts

[0125] ;

[0126] The calculation results show that temperature and stress have an important influence on the ultrasonic method of measuring the axial stress of in-service bolts. In high-temperature stress measurement, the deviation caused by temperature must be corrected. On the one hand, from experiments I, II, and IV, it can be seen that with the increase of flange temperature, the temperature distribution of in-service bolts becomes more uneven. If the end temperature of the in-service bolts is used for correction, the deviation of the result will also increase. The deviation of the calculation result using the equivalent temperature correction method is around 8%, which is basically unchanged. On the other hand,

[0127] It can be seen from experiments III, IV, and V that with the increase of the axial stress of the in-service bolts, the measurement deviation gradually decreases. Compared with the end surface temperature correction method, the measurement deviation of the axial stress of the in-service bolts using the equivalent temperature correction method is smaller, with a maximum value of 11.28% and a minimum value of 6.28%.

[0128] like Fig.10 As shown, the electronic device 10 includes one or more processors 11 and corresponding memory 12 .

[0129] The processor 11 may be a central processing unit or other forms of processing units having data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device 10 to perform desired functions. The memory 12 may include one or more computer program products, which may include various forms of computer storage media, such as volatile memory and / or non-volatile memory. The volatile memory may include, for example, a random access memory (RAM) and / or a cache memory (cache), etc. The non-volatile memory may include, for example, a read-only memory (ROM), a hard disk, a flash memory, etc. One or more computer program instructions may be stored on the computer storage medium, and the processor 11 may run the program instructions to implement the decision behavior decision method and / or other desired functions of the various embodiments of the present application described above.

[0130] In the example, the electronic device 10 may further include: an input device 13 and an output device 14, which are interconnected via a bus system and / or other forms of connection mechanisms (not shown). For example, the input device 13 may also include a keyboard, a mouse, etc. The output device 14 may include, for example, a display, a speaker, a printer, a communication network and a remote output device connected thereto, etc.

[0131] Of course, to simplify, Fig.10 Only some of the components related to the present application in the electronic device 10 are shown, and components such as a bus, an input / output interface, etc. are omitted. In addition, according to specific application situations, the electronic device 10 may also include any other appropriate components.

[0132] In addition to the above-mentioned methods and devices, the embodiments of the present application may also extend to a computer program product, which includes computer program instructions, which, when executed by a processor, enable the processor to execute the steps of the decision-making behavior decision method according to various embodiments of the present application described in the above-mentioned "Exemplary Method" section of this specification.

[0133] The computer program product may be written in any combination of one or more programming languages ​​to write program codes for performing the operations of the embodiments of the present application, including object-oriented programming languages, such as Java, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. The program code may be executed entirely on the user computing device, partially on the user device, as an independent software package, partially on the user computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0134] In addition, an embodiment of the present application may also be a readable computer storage medium on which computer program instructions are stored. When the computer program instructions are executed by a processor, the processor executes the steps of the decision-making behavior decision-making method according to various embodiments of the present application described in the above specific implementation process section of this specification.

[0135] The computer storage medium may be any combination of one or more readable media. The readable medium may be a readable signal medium or a storage medium. The storage medium may include, for example, but is not limited to, an electrical, magnetic, optical, electromagnetic, infrared or semiconductor system, device or device, or any combination of the above. More specific examples of storage media (a non-exhaustive list) include: an electrical connection with one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0136] Of course, it will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0137] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. Ultrasonic calculation method of axial stress of in-service bolts considering temperature, characterized in that: The calculation steps include: S1. Apply ultrasonic waves propagating along the axial direction of the in-service bolts under axial force. S2. Changing the temperature of the in-service bolt itself and obtaining the sound velocity of the ultrasonic longitudinal wave and ultrasonic transverse wave in the ultrasonic wave propagating on the in-service bolt; S3. Based on the sound velocity of the ultrasonic longitudinal wave and the sound velocity of the ultrasonic transverse wave, the current equivalent temperature of the in-service bolt itself is calculated in the temperature equivalent model; S4. Calculate the equivalent transit time ratio of ultrasonic longitudinal wave and ultrasonic shear wave according to the equivalent temperature of the in-service bolt; S5. Input the equivalent transit time ratio into the axial stress model to calculate the axial stress of the in-service bolt at the current equivalent temperature.

2. The ultrasonic calculation method of axial stress of in-service bolts considering temperature according to claim 1 is characterized in that: After measuring the temperature of the in-service bolt, the sound velocity of the ultrasonic longitudinal wave at the current temperature is calculated by the ultrasonic longitudinal wave sound velocity calculation formula, and then the sound velocity of the ultrasonic shear wave at the current temperature is calculated by the ultrasonic shear wave sound velocity calculation formula; The calculation formula of ultrasonic longitudinal wave speed is as follows: ； In the formula, Indicates that the in-service bolts subjected to axial stress are at a temperature of T When , the sound velocity of ultrasonic longitudinal wave propagating in the in-service bolt; superscript Z Indicates that the wave is an ultrasonic longitudinal wave, the subscript σ - T Indicates that the sound velocity of the wave is also subject to axial stress σ and temperature T The impact of Indicates that the in-service bolts are at a temperature of T When , the elastic modulus of the in-service bolt; Indicates that the in-service bolts are at a temperature of T When , the Poisson's ratio of the in-service bolt; Indicates that the in-service bolts are at a temperature of T When , the density of the in-service bolt; The ultrasonic shear wave speed calculation formula is as follows: ； In the formula, Indicates that the in-service bolts subjected to axial stress are at a temperature of T When , the sound velocity of ultrasonic shear wave propagating in the in-service bolt; superscript H Indicates that the wave is an ultrasonic shear wave.

3. The ultrasonic calculation method of axial stress of in-service bolts considering temperature according to claim 2 is characterized in that: By solving the equation of the temperature equivalent model, the corresponding equivalent temperature can be obtained; the temperature equivalent model is expressed as follows: ； In the formula, Indicates the axial stress of the in-service bolt σ Length under action; x Indicates that along the axial direction of the in-service bolt, the in-service bolt The axial distance from a point in the bolt to the end face of the in-service bolt that emits the ultrasonic wave; T x Indicates that among the bolts in service, x The temperature at Indicates that the in-service bolts subjected to axial stress are at a temperature of T x point x At this point, the ultrasonic longitudinal wave x The speed of sound propagating at l x Indicates at point x At a point x is the length of the neighborhood of the neighborhood center; d Indicates the differential sign; T eqv Indicates the equivalent temperature of the bolt in service; Indicates that the in-service bolts subjected to axial stress are at a temperature of T eqv The sound velocity of the ultrasonic longitudinal wave propagating in the in-service bolt.

4. The ultrasonic calculation method of axial stress of in-service bolts considering temperature according to claim 3 is characterized in that: The equivalent transit time ratio of ultrasonic longitudinal waves and ultrasonic shear waves is calculated by the equivalent transit time ratio calculation formula. The equivalent transit time ratio calculation formula is expressed as follows: ； In the formula, Indicates that the in-service bolts subjected to axial stress are at a temperature of T eqv The ratio of the transit sound time of the ultrasonic longitudinal wave and the ultrasonic transverse wave propagating in the in-service bolt is recorded as the equivalent transit sound time ratio; Indicates that the in-service bolts subjected to axial stress are at a temperature of T eqv When the ultrasonic longitudinal wave propagates in the in-service bolt, the transit acoustic time is recorded as the equivalent transit acoustic time of the ultrasonic longitudinal wave; Indicates that the in-service bolts subjected to axial stress are at a temperature of T eqv When the ultrasonic shear wave propagates in the in-service bolt, the transit acoustic time is recorded as the equivalent transit acoustic time of the ultrasonic shear wave; It means that the in-service bolts subjected to axial stress are at room temperature. The sound velocity of the ultrasonic longitudinal wave propagating in the in-service bolt; Indicates that the in-service bolts subjected to axial stress are at a temperature of T eqv The sound velocity of ultrasonic shear wave propagating in the in-service bolt at ; Indicates the temperature of the in-service bolts subjected to axial stress The speed of sound of ultrasonic shear waves propagating in the in-service bolt at room temperature.

5. The ultrasonic calculation method of axial stress of in-service bolts considering temperature according to claim 4 is characterized in that: The equivalent transit time of ultrasonic longitudinal waves is calculated by the equivalent transit time calculation formula of ultrasonic longitudinal waves. The equivalent transit time calculation formula of ultrasonic longitudinal waves is as follows: ； The equivalent transit time of ultrasonic shear waves is calculated by the equivalent transit time calculation formula of ultrasonic shear waves. The equivalent transit time calculation formula of ultrasonic shear waves is as follows: 。 6. The ultrasonic calculation method for axial stress of in-service bolts considering temperature according to claim 4 or 5, characterized in that: When the temperature of the in-service bolt itself is room temperature, the sound velocity of the ultrasonic longitudinal wave propagating in the in-service bolt is calculated by the corresponding sound velocity calculation formula, which is expressed as follows: ； ； In the formula, It indicates the sound velocity of ultrasonic longitudinal waves propagating in the in-service bolt that is not subjected to axial stress and is at room temperature; It indicates the speed of sound of ultrasonic shear wave propagating in the in-service bolt which is not subjected to axial stress at room temperature; the subscript 0 indicates that the in-service bolt is not subjected to axial stress; k Z Represents the acoustoelastic coefficient of ultrasonic longitudinal waves; k H Represents the acoustoelastic coefficient of ultrasonic shear waves.

7. The ultrasonic calculation method of axial stress of in-service bolts considering temperature according to claim 6 is characterized in that: The axial stress model is expressed as follows: ； In the formula, σ ( T eqv ) indicates that the in-service bolts are at a temperature of T eqv , the axial stress.

8. The ultrasonic calculation method of axial stress of in-service bolts considering temperature according to claim 7 is characterized in that: Axial stress of bolts in service σ Length under action L σ The calculation formula is as follows: ； In the formula, E It indicates the elastic modulus of the in-service bolt material at room temperature. L 0 represents the length of the in-service bolt when it is not subjected to axial stress and is at room temperature.

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