A system and method for detecting absolute stress of a steel member in service considering temperature influence

Abstract

The application relates to an absolute stress detection system and method of a steel component in service considering temperature influence, which is used for nondestructive detection of absolute stress of a steel component in service and comprises a temperature sensor for collecting surface temperature of the steel component to be detected, an ultrasonic generator for exciting ultrasonic waves, a transmitting-receiving sensor group for collecting propagation time of the critical refraction longitudinal wave signal in the steel component to be detected, a digital oscilloscope, and an upper computer for inputting the propagation information and the surface temperature into a predefined steel component absolute stress detection equation to calculate and obtain absolute stress distribution of the steel component to be detected. Nondestructive detection of absolute stress of the steel component in service under different temperatures can be realized, and the detection precision is relatively high.

Description

Technical Field

[0001] This invention belongs to the field of non-destructive testing of stress in steel components, and particularly relates to an absolute stress testing system and method for in-service steel components that takes into account the influence of temperature. Background Technology

[0002] Structural steel, with its advantages of high strength, good plasticity / toughness, and excellent assemblability, is widely used in building and bridge engineering, especially in high-rise steel structures and long-span structures where steel components serve as the main load-bearing members. With the rapid development of steel structure buildings, a large number of steel structure stadiums, airports, railway stations, super high-rise buildings, and long-span bridges have been completed or are under construction. However, in-service steel components are subject to long-term environmental corrosion and fatigue loads, resulting in damage and stress redistribution, which adversely affects the safety of steel structure buildings.

[0003] Currently, in order to understand the stress state and mechanical properties of steel components, the common method is to test the absolute stress of the steel components to detect stress concentrations and damage points.

[0004] Existing nondestructive testing methods for stress include strain gauge methods, fiber optic grating methods, X-ray methods, neutron diffraction methods, magnetic methods, and ultrasonic methods. Among these, strain gauge methods, fiber optic grating methods, X-ray methods, neutron diffraction methods, and magnetic methods suffer from drawbacks such as low accuracy, limited applicability, and high cost. These drawbacks include the inability to measure stress changes in steel components over a period of time, the complexity and expense of the equipment, the potential for radiation pollution, and limitations imposed by factors such as grain size, microcracks, porosity, carbon content, and environmental electromagnetic noise in the steel component being tested.

[0005] Ultrasonic stress testing technology, especially critical refraction longitudinal waves, is widely used due to its advantages such as high sensitivity to stress, good signal stability, and insensitivity to structural geometry. Li Zuohua et al. proposed a method for detecting the absolute stress distribution of steel components based on critical refraction longitudinal waves in CN201710118738.1, realizing the detection of regional stress distribution in steel components. Xu Chunguang et al. proposed an ultrasonic non-destructive testing method for torsional residual stress in CN201610009044.X. However, the ambient temperature of in-service steel components changes over time, affecting the propagation speed of critical refraction longitudinal waves. The thermal expansion effect of the material also alters the propagation path of the critical refraction longitudinal waves. Since the above methods do not consider the influence of temperature on the propagation information of critical refraction longitudinal waves, the stress detection results show significant deviations, resulting in limited applicability in practical applications. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] To address the aforementioned problems in the prior art, this invention provides an absolute stress detection system and method for in-service steel components that takes temperature effects into account. This system enables non-destructive testing of the absolute stress of in-service steel components at different temperatures, solving the technical problem of large deviations in detection accuracy due to temperature changes and low applicability in practical applications.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0010] In a first aspect, the present invention provides an absolute stress detection system for in-service steel components that takes into account the influence of temperature, for non-destructive testing of the absolute stress of in-service steel components, comprising: an ultrasonic generator, a transducer and receiver sensor group, a digital oscilloscope, a host computer, and a temperature sensor.

[0011] The temperature sensor is used to collect the surface temperature of the steel component to be tested;

[0012] The single-transmitter dual-receiver sensor group includes a transmitting sensor, a first receiving sensor, and a second receiving sensor, wherein the first receiving sensor and the second receiving sensor are identical.

[0013] The ultrasonic generator is used to excite the transmitting sensor to generate a critically refracted longitudinal wave signal that propagates in the steel component under test.

[0014] The first receiving sensor is used to receive the critically refracted longitudinal wave signal propagating in the steel component under test and to acquire the first receiving signal;

[0015] The second receiving sensor is used to receive the critically refracted longitudinal wave signal propagating in the steel component under test and to acquire the second receiving signal;

[0016] The digital oscilloscope is used to receive the first received signal and the second received signal, perform signal conversion, and obtain a first digital received signal corresponding to the first received signal and a second digital received signal corresponding to the second received signal.

[0017] The host computer is used to receive and calculate the time interval between the first digital received signal and the second digital received signal, wherein the time interval is the propagation sound time of the critical refracted longitudinal wave signal; and inputs the propagation sound time and the surface temperature into a predefined absolute stress detection equation for steel components to calculate and obtain the absolute stress distribution of the steel component to be tested.

[0018] The equation for detecting the absolute stress of the steel component is:

[0019]

[0020] σ is the absolute stress detection value, t is the propagation time of the critical refracted longitudinal wave in the steel component at the actual temperature, t0 is the propagation time of the critical refracted longitudinal wave in the replica at the reference temperature, T is the surface temperature of the steel component, T0 is the reference temperature, C1 is the stress influence coefficient, C2 is the temperature influence coefficient, and C3 is the temperature and stress coupling influence coefficient.

[0021] Optionally, the transmitting sensor, the first receiving sensor, and the second receiving sensor are sequentially fixed on the steel component to be tested; the transmitting sensor, the first receiving sensor, and the second receiving sensor are respectively spaced at a preset distance;

[0022] The transmitting sensor is connected to the ultrasonic generator;

[0023] The first receiving sensor and the second receiving sensor are connected via plexiglass.

[0024] The digital oscilloscope is connected to the first receiving sensor and the second receiving sensor respectively;

[0025] The digital oscilloscope is connected to the host computer via communication.

[0026] The temperature sensor is fixed on the steel component to be tested, and the temperature sensor is communicatively connected to the host computer.

[0027] Optionally, before the ultrasonic generator operates, the temperature sensor is used to detect the surface temperature of the steel component to be tested, and after obtaining the surface temperature, the temperature sensor is removed.

[0028] Secondly, the present invention also provides an absolute stress detection method based on the absolute stress detection system for in-service steel components considering the temperature effect described in the first aspect, for detecting the absolute stress distribution of in-service steel components in steel structure buildings, including:

[0029] S1. Prepare a replica of the steel component to be tested in service. Under the same temperature gradient, apply stress to the replica with different stress gradients. Collect the time-domain signals of the critical refractive longitudinal wave of the replica under different temperature gradients and different stress gradients, and obtain the critical refractive longitudinal wave propagation information of each temperature gradient and each stress gradient.

[0030] S2. Fit the propagation information of each temperature gradient and each stress gradient and the corresponding critical refractive longitudinal wave, calculate the stress influence coefficient, temperature influence coefficient and temperature and stress coupling influence coefficient, and obtain the absolute stress detection equation of the steel component.

[0031] S3. Collect surface temperature data of the steel component to be tested; the surface temperature data is obtained by a temperature sensor.

[0032] S4. Acquire the propagation information of the critical refraction longitudinal wave signal in the steel component under test. The propagation information is the time difference between the first receiving sensor and the second receiving sensor set on the component under test sensing the same critical refraction longitudinal wave signal.

[0033] The critical refractive longitudinal wave signal is an ultrasonic signal generated by an ultrasonic generator and emitted by a sensor, which propagates in the steel component under test.

[0034] S5. Input the propagation information and the surface temperature into the absolute stress detection equation of the steel component to calculate the absolute stress distribution of the steel component to be tested.

[0035] Optionally, S1 further includes,

[0036] Data processing of the time-domain signal of the critically refracted longitudinal wave is performed as follows:

[0037] A bandpass filter is used to filter noise in the time-domain signal of the critically refracted longitudinal wave. The passband of the bandpass filter is ±2MHz of the center frequency of the transmitting sensor.

[0038] In one embodiment, after S4, data processing of the time-domain signal of the critically refracted longitudinal wave is also included, specifically:

[0039] A bandpass filter is used to filter noise in the time-domain signal of the critically refracted longitudinal wave. The passband of the bandpass filter is ±2MHz of the center frequency of the transmitting sensor.

[0040] Optionally, the temperature gradient ranges from 0°C to 55°C, with each 5°C increment representing a gradient.

[0041] The stress gradient ranges from 0 MPa to 160 MPa, with each 10 MPa representing a gradient.

[0042] Optionally, the replica has the same specifications, material, and surface roughness as the in-service steel component to be tested.

[0043] Optionally, in S1,

[0044] The replica is kept at the same temperature gradient for at least 30 minutes.

[0045] (III) Beneficial Effects

[0046] This invention provides an absolute stress detection system and method for in-service steel components considering the influence of temperature. The system uses a single-transmitter, dual-receiver sensor array to generate a critically refracted longitudinal wave in the steel component under test and collects signals of the same critically refracted longitudinal wave at two locations on the steel structure. A temperature sensor detects the surface temperature of the steel component. A digital oscilloscope and a host computer process the signals to calculate the propagation information of the same critically refracted longitudinal wave. Finally, a predefined absolute stress detection equation for the steel component is used to determine the absolute stress distribution. The system has a simple structure, fast detection speed, high efficiency, minimal time and scenario limitations, high feasibility, high detection accuracy, and stable detection results.

[0047] The method described herein, based on the system, can be applied to the absolute stress detection of steel components in steel structure buildings under construction and already completed. It is simple, fast, easy to implement, and has high detection efficiency and accuracy. Furthermore, in the technical solution provided by this invention, the replica is subjected to stress loading at different stress gradients under each temperature gradient, and the time-domain signals of the critical refraction longitudinal waves of the replica are collected under different temperature gradients and different stress gradients. This considers the cases of different stress loadings at the same temperature and the same stress loading at different temperatures, resulting in more refined data. It also takes into account the errors caused by the simultaneous changes in temperature and stress loading. The calculation accuracy of the absolute stress detection equation for steel components obtained through the data is high and the error is small.

[0048] The system and method provided by this invention employ a single-transmitter, dual-receiver sensor array to measure the propagation information of critically refracted longitudinal waves, thereby reducing the influence of temperature on this information. Furthermore, the detection equation incorporates a coupling term between temperature and stress, further improving detection accuracy. Moreover, non-destructive testing of absolute stress in in-service steel components under different temperature conditions is achieved through replication. The testing process is convenient and efficient, the testing instrument is easy to carry and install, and the test results are stable and reliable. Attached Figure Description

[0049] Figure 1 A schematic diagram of an absolute stress detection system for in-service steel components considering the temperature effect, provided in an embodiment of the present invention;

[0050] Figure 2 This is a schematic diagram of a single-transmitter, dual-receiver sensor assembly fixed on a steel component according to an embodiment of the present invention.

[0051] Figure 3 A schematic diagram of the propagation of a critically refracted longitudinal wave on a steel component, provided for another embodiment of the present invention;

[0052] Figure 4 A flowchart of an absolute stress detection method for in-service steel components considering the temperature effect, provided in an embodiment of the present invention;

[0053] Figure 5A schematic diagram of an absolute stress detection system for in-service steel components considering the temperature effect, provided as another embodiment of the present invention;

[0054] Figure 6 A schematic diagram of the time-domain signal of the critically refracted longitudinal wave provided in another embodiment of the present invention;

[0055] Figure 7 A schematic diagram of the dimensions of a steel component is provided for another embodiment of the present invention;

[0056] Figure 8 for Figure 7 A replica of a steel structural member;

[0057] Figure 9 A schematic diagram illustrating the fitting of temperature gradients, stress gradients, and corresponding critical refractive longitudinal wave propagation information according to another embodiment of the present invention;

[0058] Figure 10 This is a deviation diagram of ultrasonic testing results for steel components provided in another embodiment of the present invention. Detailed Implementation

[0059] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0060] Steel structures are widely used in the construction and related industries, and are present in numerous completed, under-construction, and planned buildings. After construction, steel structures are subjected to long-term environmental erosion and fatigue loads during their service life, leading to damage to steel components and stress redistribution. This adversely affects the safety of steel structure buildings, potentially causing collapses, deformations, or fractures. To promptly and accurately detect the absolute stress distribution of in-service steel structures, this invention provides an absolute stress detection system for in-service steel components that considers the influence of temperature. This system allows for absolute stress detection without damaging in-service steel components. Figure 1 The structure of the in-service steel component absolute stress detection system shown mainly includes an ultrasonic generator, a single-transmitter dual-receiver sensor group, a digital oscilloscope, a host computer, and a temperature sensor.

[0061] The sensor array, consisting of a transmitter, a first receiver, and a second receiver, comprises an identical transmitter and a receiver. The transmitter, receiver, and receiver are sequentially fixed to the steel component under test, with a predetermined distance between them. The fixing method can be as follows: Figure 2As shown. The first preset distance between the transmitting sensor and the first receiving sensor, and the second preset distance between the first receiving sensor and the second receiving sensor, are determined by the actual application conditions, and the first preset distance does not need to be the same as the second preset distance.

[0062] The transmitting sensor is connected to the ultrasonic generator.

[0063] The first receiving sensor and the second receiving sensor are connected by plexiglass.

[0064] The digital oscilloscope is connected to the first receiving sensor and the second receiving sensor respectively, and the digital oscilloscope can simultaneously receive and display ultrasonic signals from at least two channels.

[0065] The digital oscilloscope is connected to the host computer via communication.

[0066] The temperature sensor is fixed on the steel component to be tested, and the temperature sensor is communicatively connected to the host computer.

[0067] The temperature sensor is used to collect the surface temperature of the steel component to be tested.

[0068] In some embodiments, for greater convenience, in addition to contact-type temperature sensors, more portable non-contact infrared thermometers may also be used.

[0069] The ultrasonic generator is used to excite the emission sensor to generate a critically refracted longitudinal wave signal that propagates in the steel component under test.

[0070] The first receiving sensor is used to receive the critically refracted longitudinal wave signal propagating in the steel component under test and obtain the first receiving signal.

[0071] The second receiving sensor is used to receive the critically refracted longitudinal wave signal propagating in the steel component under test and to obtain the second receiving signal.

[0072] The digital oscilloscope is used to receive the first received signal and the second received signal, perform signal conversion, and obtain a first digital received signal corresponding to the first received signal and a second digital received signal corresponding to the second received signal.

[0073] The host computer is used to receive and calculate the time interval between the first digital received signal and the second digital received signal, wherein the time interval is the propagation sound time of the critical refracted longitudinal wave signal; and inputs the propagation sound time and the surface temperature into a predefined absolute stress detection equation for steel components to calculate and obtain the absolute stress distribution of the steel component to be tested.

[0074] In practical applications, before the ultrasonic generator operates, the surface temperature of the steel component to be tested is detected using the temperature sensor. After obtaining the surface temperature, the temperature sensor is removed. The host computer can be any electronic device, such as a computer, capable of performing the above operations. The system may also include devices such as signal amplifiers.

[0075] In one embodiment, the system application can be specifically implemented as follows: A target steel component to be tested is selected; a suitable location on the steel component is chosen as the test area; the surface of the test area is polished; a coupling agent is applied to the detection area; and a transmitting sensor, a first receiving sensor, and a second receiving sensor are sequentially fixed in place. Once all connections are properly prepared, the detection system is adjusted to appropriate parameters for normal operation. Then, a temperature sensor is used to detect the surface temperature of the steel component to be tested. After obtaining the surface temperature, the temperature sensor is removed from the steel component. Further, the system is brought into normal operating condition, such as... Figure 3 The critically refracted longitudinal wave propagates on the steel component. A dual-sensor array transmits and receives the critically refracted longitudinal wave signal, and an oscilloscope is used to acquire the time-domain signal of the critically refracted longitudinal wave in the detection area of ​​the in-service steel component. The host computer processes the acquired time-domain signal to obtain the propagation time of the measured ultrasonic signal, and inputs the measured surface temperature of the in-service steel component and the ultrasonic propagation time into the predefined absolute stress detection equation of the steel component to obtain the absolute stress distribution of the in-service steel component.

[0076] Since most in-service steel components are non-removable, the predefined absolute stress test equation for steel components is usually obtained by conducting experiments on replicas of the steel component under test at different temperatures and under different loading stresses.

[0077] In this embodiment, the equation for detecting the absolute stress of the steel component is:

[0078]

[0079] Where σ is the absolute stress detection value, t is the propagation time of the critical refracted longitudinal wave in the steel component at the actual temperature, t0 is the propagation time of the critical refracted longitudinal wave in the replica at the reference temperature, T is the surface temperature of the steel component, T0 is the reference temperature, C1 is the stress influence coefficient, C2 is the temperature influence coefficient, and C3 is the temperature and stress coupling influence coefficient.

[0080] This invention provides an absolute stress detection system for in-service steel components considering the influence of temperature. The system uses a single transmitter and dual receiver sensor array to generate a critically refracted longitudinal wave in the steel component under test and collects signals of the same critically refracted longitudinal wave at two locations on the steel structure. A temperature sensor detects the surface temperature of the steel component. A digital oscilloscope and a host computer process the signals to calculate the propagation information of the same critically refracted longitudinal wave. Finally, a predefined absolute stress detection equation for the steel component is used to determine the absolute stress distribution. The system has a simple structure, fast detection speed, high efficiency, minimal time and scenario limitations, high feasibility, high detection accuracy, and stable detection results.

[0081] Furthermore, the present invention also provides a non-destructive testing method based on the aforementioned in-service steel component absolute stress detection system, used to detect the absolute stress distribution of in-service steel components in steel structure buildings, such as... Figure 4 As shown, the main steps include:

[0082] S1. Prepare a replica of the in-service steel component to be tested. Under each temperature gradient, apply stress to the replica at different stress gradients. Collect the time-domain signals of the critical refractive longitudinal waves of the replica at different temperature gradients and stress gradients to obtain the critical refractive longitudinal wave propagation information for each temperature gradient and stress gradient. In order to make the final absolute stress detection equation of the steel component closer to the in-service steel component, the replica has the same specifications, material, and surface roughness as the in-service steel component to be tested.

[0083] S2. Fit the propagation information of each temperature gradient and each stress gradient and the corresponding critical refraction longitudinal wave, calculate the stress influence coefficient, temperature influence coefficient, and temperature and stress coupling influence coefficient, and obtain the absolute stress detection equation of the steel component.

[0084] S3. Collect surface temperature data of the steel component to be tested; the surface temperature data is obtained by temperature sensor detection.

[0085] S4. Acquire the propagation information of the critical refraction longitudinal wave signal in the steel component under test. The propagation information is the time difference between the first receiving sensor and the second receiving sensor set on the component under test sensing the same critical refraction longitudinal wave signal.

[0086] The critical refractive longitudinal wave signal is an ultrasonic signal generated by an ultrasonic generator and emitted by a sensor, which propagates in the steel component under test.

[0087] S5. Input the propagation information and the surface temperature into the absolute stress detection equation of the steel component to calculate the absolute stress distribution of the steel component to be tested.

[0088] In some other embodiments, it also includes S1 and / or S4,

[0089] Data processing of the time-domain signal of the critically refracted longitudinal wave can be performed as follows:

[0090] A bandpass filter is used to filter noise in the time-domain signal of the critically refracted longitudinal wave. The passband of the bandpass filter is ±2MHz of the center frequency of the transmitting sensor.

[0091] In one specific embodiment, the transmitting sensor, the first receiving sensor, and the second sensor are preferably all sensors of the same specification for detection.

[0092] Furthermore, in one embodiment, S1 and S2 can be specifically implemented as follows:

[0093] Information such as the specifications, material, and surface roughness of the steel component to be tested is collected. A replica is then fabricated that is nearly identical to the original in terms of specifications, material, and surface roughness. Higher similarity leads to better absolute stress measurement equations for the steel component. To increase the accuracy of the measurement data, internal stresses in the replica can be eliminated after fabrication.

[0094] The above system is used to test replicas subjected to different temperatures and loading stresses. Specifically, in this embodiment, the ultrasonic signal generator outputs a 200V square wave pulse electrical signal to excite the transmitting sensor fixed on the replica to generate a critically refracted longitudinal wave signal that propagates on the replica. The first receiving sensor and the second receiving sensor sense the same critically refracted longitudinal wave signal.

[0095] The first and second receiving sensors are the same size and model and are connected by an plexiglass plate.

[0096] The oscilloscope receives the same critical refraction longitudinal wave signal sensed by the first receiving sensor and the second receiving sensor, generates the corresponding critical refraction longitudinal wave time domain signal, and sends it to the host computer for processing.

[0097] Furthermore, a high and low temperature test chamber can be used to control the temperature of the replicated specimen, and a universal testing machine can be used to apply gradient tensile loading to the replicated specimen. The temperature gradient ranges from 0℃ to 55℃, with each 5℃ increment; the stress gradient ranges from 0MPa to 160MPa, with each 10MPa increment. Gradient tensile loading is applied to the replicated specimen under different temperature conditions. Once the temperature and stress reach the target values, a dual-sensor array is used to transmit and receive critical refractive longitudinal wave signals, and the time-domain signals of the critical refractive longitudinal waves under different temperature and stress conditions are stored. Specifically, the operation involves transmitting and receiving the critical refractive longitudinal wave signals while simultaneously loading with the universal testing machine. After loading is complete, the universal testing machine is released from its constraint on the replicated specimen, and the high and low temperature test chamber is adjusted to the next temperature. This process is repeated, and the time-domain signals of the critical refractive longitudinal waves under different temperature and stress conditions are stored.

[0098] The replica is kept at the same temperature gradient for at least 30 minutes.

[0099] Specifically, such as Figure 5 In the illustrated embodiment, a dual-sensor array is coupled to a replica specimen. The replica specimen is placed in a high-low temperature test chamber. After the internal temperature of the high-low temperature test chamber reaches the set value, it is kept at that temperature for half an hour to ensure uniform heating of the replica specimen and the sensor array. After the temperature stabilizes, a universal testing machine is used to apply gradient tensile loading to the replica specimen. For example, when measuring the propagating sound of a replica under 0 MPa (no stress loading) by holding it at 0℃ for more than 30 minutes, stress loading is then applied sequentially to the replica at 10 MPa, 20 MPa, 30 MPa, ..., 150 MPa, and 160 MPa to obtain the critical refractive longitudinal wave signal of the replica under different stress loading at 0℃. Then, after controlling the internal temperature of the high and low temperature test chamber to reach 5℃, it is held for half an hour, and the stress loading is repeated sequentially with stresses of 10 MPa, 20 MPa, 30 MPa, ..., 150 MPa, and 160 MPa to obtain the critical refractive longitudinal wave signal of the replica under different stress loading. Then, after controlling the internal temperature of the high and low temperature test chamber to reach 10℃, it is held for half an hour, and the above stress loading is repeated, and so on, changing the temperature and repeating the stress loading process.

[0100] The influence of thermal stress is eliminated by changing the temperature first and then loading, so that the absolute stress of the replicated specimen is the loading stress.

[0101] In the above embodiments, the preferred measurement temperature is 0-55℃, with each 5℃ increment representing a gradient, which is applicable to a wide range of natural scenarios. In practical applications, the method provided by this invention can also be extended to other temperature scenarios, such as below zero or higher temperatures, and the gradient range should be changed according to the actual situation. In addition, the method provided by this invention is not only applicable to steel components, but also has great reference and applicability for the absolute stress detection of other metal components.

[0102] Furthermore, the acquired time-domain signal of the critically refracted longitudinal wave is processed to obtain the propagation acoustic time of the critically refracted longitudinal wave under different temperature and stress conditions. Data fitting is then performed on temperature, applied stress, and the propagation acoustic time of the critically refracted longitudinal wave to obtain an absolute stress detection equation for the steel component considering the influence of temperature. For example... Figure 6 A schematic diagram of the time-domain signal of the critically refracted longitudinal wave provided in another embodiment of the present invention.

[0103] The data processing of the time-domain signal may include: using a bandpass filter to remove noise from the time-domain signal, wherein the passband of the bandpass filter is ±2MHz of the sensor center frequency; and using a cross-correlation algorithm to calculate the propagation acoustic time of the two critical refracted longitudinal waves.

[0104] The equation for detecting the absolute stress of the steel component is:

[0105]

[0106] σ is the absolute stress detection value, t is the propagation time of the critical refracted longitudinal wave in the steel component at the actual temperature, t0 is the propagation time of the critical refracted longitudinal wave in the replica at the reference temperature, T is the surface temperature of the steel component, T0 is the reference temperature, C1 is the stress influence coefficient, C2 is the temperature influence coefficient, and C3 is the temperature and stress coupling influence coefficient. C1, C2, and C3 are all obtained by data fitting.

[0107] The absolute stress detection equation for steel components considering temperature effects incorporates the coupled influence of temperature and stress, and the detection coefficients in the equation are obtained through variable temperature loading tests. In one embodiment, the process of obtaining the absolute stress detection equation for the steel component is as follows:

[0108] A1. Calculate the propagation path of the critical refracted longitudinal wave at temperature T:

[0109] In a dual-receiver sensor array, ultrasonic waves are emitted from the transmitting sensor, pass through the sensor interior and coupling agent at a first critical refraction angle, and are converted into critically refracted longitudinal waves on the surface of the steel component. These critically refracted longitudinal waves propagate along the surface of the steel component and are received by the first and second receiving sensors. Since the two receiving sensors have the same geometric dimensions and model, the propagation time of the critically refracted longitudinal wave is only the propagation time within the steel component, excluding its propagation time within the sensor interior and coupling agent. The two receiving probes of the dual-receiver sensor array are connected by an acrylic plate, and the sensors are also made of acrylic. Temperature changes cause the acrylic to expand and contract, resulting in a change in the path length of the critically refracted longitudinal wave. When the temperature is T, the propagation path of the critically refracted longitudinal wave is given by formula (1):

[0110]

[0111] Among them, L T Let T be the critical propagation path of the refracted longitudinal wave at temperature T. α is the propagation path of the critical refracted longitudinal wave at temperature T0 (reference temperature); α is the coefficient of thermal expansion of plexiglass.

[0112] A2. Determine the critical refracted longitudinal wave propagation velocity in the steel structure:

[0113] According to the thermoelastic theory, the propagation speed of ultrasound in steel components has an approximately linear relationship with temperature, as shown in formula (2):

[0114]

[0115] Among them, V T Let T be the critical refracted longitudinal wave propagation velocity in the steel component at temperature T. β is the propagation velocity of the critical refracted longitudinal wave in the steel component at a temperature of T0 (reference temperature); β is the coefficient of the critical refracted longitudinal wave sound velocity as a function of temperature.

[0116] A3. Calculate the velocity of sound when the direction of ultrasonic wave propagation is parallel to the stress:

[0117] According to the principle of acoustoelasticity, when the direction of ultrasonic wave propagation is parallel to the stress, its sound velocity can be calculated using formula (3):

[0118]

[0119] Where σ is the absolute stress of the steel member, V σ Let be the propagation velocity of the critically refracted longitudinal wave at stress σ. denoted as ν, represents the propagation velocity of the critical refracted longitudinal wave at zero stress; k is the acoustoelastic coefficient, which is related to the elastic modulus of the material.

[0120] A4. Calculation of sound velocity under different temperature and stress conditions:

[0121] Since the elastic modulus of a material has an approximately linear relationship with temperature, the acoustoelastic coefficient also changes with temperature. Considering the effects of temperature and stress on wave velocity, by combining equations (2) and (3), we can obtain the formulas for calculating the sound velocity under different temperature and stress conditions:

[0122]

[0123] A5. Calculate the propagation time of the critical refracted longitudinal wave.

[0124] Where γ is the coefficient of acoustoelasticity that varies with temperature. Combining equations (1) and (4), the propagation time t of the critical refracted longitudinal wave under the combined influence of stress σ and temperature T is calculated:

[0125] t=t0+C1σ+C2ΔT+C3(T-T0)σ (5)

[0126] Where C1 = kt0 / 2, C2 = t0(α+β), and C3 = -kt0(α+β+γ) / 2, t0 is the propagation time of the critical refracted longitudinal wave at zero stress at the reference temperature; C1 is the stress influence coefficient; C2 is the temperature influence coefficient; and C3 is the temperature and stress coupling influence coefficient. C1, C2, and C3 are obtained through data fitting.

[0127] By separating variables in equation (5), the absolute stress detection equation for steel components considering the effect of temperature can be obtained:

[0128]

[0129] The reference temperature is preferably 0℃, used for comparison. In practical applications, a suitable temperature can be selected as the reference temperature according to the actual situation, and there is no restriction here.

[0130] To better explain the above technical solution, a more specific embodiment is used here for illustration.

[0131] like Figure 7 and Figure 8 The embodiment shown is a verification embodiment. Figure 8 Specimen A was used as the tensile specimen of Q345 steel to be tested, and specimen B was used as a replica. Figure 7 This is a dimensional drawing of the steel component.

[0132] The copy and the system are as follows Figure 3 The replica is coupled and fixed in the manner shown, and then placed in a high and low temperature test chamber.

[0133] The temperature of the high and low temperature test chamber was controlled from 0 to 55℃ in 5℃ increments, with 0℃ as the reference temperature. After the test chamber reached the target temperature and was held at that temperature for half an hour, a universal testing machine was used to apply tensile stress to the replicated specimen, with the stress ranging from 0 to 160 MPa in 10 MPa increments. The time-domain signals of the critical refracted longitudinal wave under different temperature and stress conditions were collected, and the time-domain signals were processed to obtain the propagation acoustic time of the critical refracted longitudinal wave under different temperature and stress conditions.

[0134] By fitting data on temperature, applied stress, and critical refractive longitudinal wave propagation time, an absolute stress detection equation for steel components considering the effect of temperature is obtained. The coefficient fitting graph is shown below. Figure 9 As shown.

[0135] The steel component to be tested is placed in a high and low temperature test chamber, the internal temperature of the high and low temperature test chamber is controlled, and a universal testing machine is used to load it.

[0136] When measuring the critical refracted longitudinal wave propagation time of the steel component under test, a temperature sensor was used to measure the surface temperature of the steel component. The propagation time and temperature were substituted into the absolute stress detection equation for the steel component considering the temperature effect, and the magnitude of the absolute stress of the in-service steel component was obtained. The detection results are shown in Table 1. The deviation between the ultrasonically detected stress value and the actual loaded stress value is shown in Table 1. Figure 10 As shown.

[0137] Table 1:

[0138]

[0139] like Figure 10 As shown, under conditions of temperature and applied stress variation, the deviation between the ultrasonically detected stress value and the actual applied stress value is small, and the detection accuracy is high.

[0140] The present invention provides an absolute stress detection system for in-service steel components. It uses a single transmitter and dual receiver sensor group to measure the propagation time of critical refracted longitudinal waves. The two receiver sensors have the same geometric dimensions and model. The propagation time of the critical refracted longitudinal wave is only the propagation time in the steel component, excluding the propagation time inside the sensor and in the coupling agent. This can reduce the influence of temperature on the propagation time of the critical refracted longitudinal wave. It is easy to carry and install and has high detection accuracy.

[0141] This invention provides an absolute stress detection system and non-destructive testing method for in-service steel components, enabling non-destructive testing of the absolute stress of in-service steel components under different temperature conditions. The instrument and method are simple, easy to implement, and offer high testing efficiency and accuracy. It can be applied to the absolute stress detection of steel components in both under-construction and completed steel structure buildings. The method described above, based on the system, is simple, fast, easy to implement, and offers high testing efficiency and accuracy. Furthermore, in the technical solution provided by this invention, under each temperature gradient, the replica is subjected to stress loading at different stress gradients. The time-domain signals of the critical refracted longitudinal waves of the replica are collected under different temperature and stress gradients. This considers the cases of different stress loadings at the same temperature and the same stress loading at different temperatures, resulting in more refined data. It also takes into account the errors caused by simultaneous changes in temperature and stress loading. The calculation accuracy of the absolute stress detection equation for steel components obtained from the data is high, with small errors.

[0142] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. An absolute stress testing system for in-service steel components considering the influence of temperature, used for non-destructive testing of the absolute stress of in-service steel components, characterized in that, Includes an ultrasonic generator, a dual-transmitter sensor group, a digital oscilloscope, a host computer, and a temperature sensor; The temperature sensor is used to collect the surface temperature of the steel component to be tested; The single-transmitter dual-receiver sensor group includes a transmitting sensor, a first receiving sensor, and a second receiving sensor, wherein the first receiving sensor and the second receiving sensor are identical. The ultrasonic generator is used to excite the transmitting sensor to generate a critically refracted longitudinal wave signal that propagates in the steel component under test. The first receiving sensor is used to receive the critically refracted longitudinal wave signal propagating in the steel component under test and to acquire the first receiving signal; The second receiving sensor is used to receive the critically refracted longitudinal wave signal propagating in the steel component under test and to acquire the second receiving signal; The digital oscilloscope is used to receive the first received signal and the second received signal, perform signal conversion, and obtain a first digital received signal corresponding to the first received signal and a second digital received signal corresponding to the second received signal. The host computer is used to receive and calculate the time interval between the first digital received signal and the second digital received signal, wherein the time interval is the propagation sound time of the critical refracted longitudinal wave signal; and inputs the propagation sound time and the surface temperature into a predefined absolute stress detection equation for steel components to calculate and obtain the absolute stress distribution of the steel component to be tested. The equation for detecting the absolute stress of the steel component is: σ is the absolute stress detection value, t is the propagation time of the critical refracted longitudinal wave in the steel component at the actual temperature, t0 is the propagation time of the critical refracted longitudinal wave in the replica at the reference temperature, T is the surface temperature of the steel component, T0 is the reference temperature, C1 is the stress influence coefficient, C2 is the temperature influence coefficient, and C3 is the temperature and stress coupling influence coefficient.

2. The absolute stress detection system as described in claim 1, characterized in that, The transmitting sensor, the first receiving sensor, and the second receiving sensor are fixed sequentially on the steel component to be tested; the transmitting sensor, the first receiving sensor, and the second receiving sensor are spaced apart by a preset distance; The transmitting sensor is connected to the ultrasonic generator; The first receiving sensor and the second receiving sensor are connected via plexiglass. The digital oscilloscope is connected to the first receiving sensor and the second receiving sensor respectively; The digital oscilloscope is connected to the host computer via communication. The temperature sensor is fixed on the steel component to be tested, and the temperature sensor is communicatively connected to the host computer.

3. The absolute stress detection system as described in claim 2, characterized in that, Before the ultrasonic generator operates, the temperature sensor is used to detect the surface temperature of the steel component to be tested. After obtaining the surface temperature, the temperature sensor is removed.

4. An absolute stress detection method based on the absolute stress detection system according to any one of claims 1 to 3, used to detect the absolute stress distribution of in-service steel components in steel structure buildings, characterized in that, include: S1. Prepare a replica of the steel component to be tested in service. Under each temperature gradient, apply stress to the replica at different stress gradients. Collect the time-domain signals of the critical refractive longitudinal waves of the replica at different temperature gradients and stress gradients to obtain the critical refractive longitudinal wave propagation information at each temperature gradient and stress gradient. S2. Fit the propagation information of each temperature gradient and each stress gradient and the corresponding critical refractive longitudinal wave, calculate the stress influence coefficient, temperature influence coefficient and temperature and stress coupling influence coefficient, and obtain the absolute stress detection equation of the steel component. S3. Collect surface temperature data of the steel component to be tested; the surface temperature data is obtained by a temperature sensor. S4. Acquire the propagation information of the critical refraction longitudinal wave signal in the steel component under test. The propagation information is the time difference between the first receiving sensor and the second receiving sensor set on the component under test sensing the same critical refraction longitudinal wave signal. The critical refractive longitudinal wave signal is an ultrasonic signal generated by an ultrasonic generator and emitted by a sensor, which propagates in the steel component under test. S5. Input the propagation information and the surface temperature into the absolute stress detection equation of the steel component to calculate the absolute stress distribution of the steel component to be tested.

5. The absolute stress detection method according to claim 4, characterized in that, The S1 also includes, Data processing of the time-domain signal of the critically refracted longitudinal wave is performed as follows: A bandpass filter is used to filter noise in the time-domain signal of the critically refracted longitudinal wave. The passband of the bandpass filter is ±2MHz of the center frequency of the transmitting sensor.

6. The absolute stress detection method as described in claim 4, characterized in that, The temperature gradient ranges from 0°C to 55°C, with each 5°C increment representing a gradient. The stress gradient ranges from 0 MPa to 160 MPa, with each 10 MPa representing a gradient.

7. The absolute stress detection method as described in claim 4, characterized in that, The replica has the same specifications, material, and surface roughness as the in-service steel component to be tested.

8. The absolute stress detection method as described in claim 4, characterized in that, In S1, The replica is kept at the same temperature gradient for at least 30 minutes.

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