Ultrasonic probe for on-line measurement of axial force of high-temperature bolt

Abstract

The present invention relates to an integrated and a split-type ultrasonic probe for measuring an axial force of a high-temperature bolt, the integrated ultrasonic probe being vertically installed, an

Description

CROSS REFERENCE OF RELATED APPLICATIONS The present application claims the priority of the Chinese invention patent application which application number is 202110549336.3 filed May 20, 2021, and the contents of which are hereby incorporated into this application by reference. FIELD OF THE INVENTION The invention relates to an ultrasonic probe for on-line measurement of axial force of high-temperature bolt, and specifically relates to an integrated and a split-type ultrasonic probe for on-line measuring an axial force of a high-temperature bolt, the device can long-term measure axial force of high-temperature bolt in high-temperature environments online, belongs to the field of ultrasonic nondestructive testing. BACKGROUND Special pressure equipment such as pressure vessels and pipelines are widely used in the pillar areas of the national economy such as petrochemicals, electricity, and metallurgy, mostly is used in harsh environments such as high temperature and high pressure. In recent years, with the increasing demand for carbon reduction and efficiency enhancement, pressure equipment has developed towards extreme directions such as high parameters, heavy duty, and long service life. Bolts are key components in the assembly of these pressure equipment, and leakage caused by changes in bolt axial force is the biggest safety hazard in the industry. The pre tightening force applied to the bolt has a significant impact on its service state, performance, and lifespan. A small preload can easily lead to unreliable connections, resulting in vibration relaxation, structural slippage, and other conditions during operation; if the pre tightening force is too large, it will increase the load on the bolts, making bolts extremely easy to breakage, thereby weakening the load bearing capacity of the node, and in severe cases, it may induce structural instability; however, bolt looseness caused by alternating loads is difficult to detect, ultimately resulting in significant damage and loss. Therefore, real-time monitoring of bolt axial force is important for ensuring the stability and reliability of bolt assembly structures. The commonly used methods for measuring bolt axial force include torque wrench method, adhesive strain gauge method, stress washer method, implanted strain gauge method, implanted fiber grating method, ultrasonic measurement techniques, etc. In engineering, construction personnel often use the torque wrench method to control the axial force of bolts in the connecting structure. Manual torque wrenches or pneumatic, hydraulic or electric wrenches are usually used to indirectly control bolt preload through tightening torque. This method is simple to operate and low in cost, but the measurement accuracy of bolt axial force is not high. The adhesive strain gauge method is a commonly used method for measuring bolt axial force in engineering, by measuring the strain on the bolt surface, the stress on the surface of the tested bolt is calculated to achieve bolt axial force detection. However, strain gauges may experience stress relaxation at high temperatures, which cannot meet the needs of long-term monitoring; the stress washer method is to make the pressure sensor into a washer shape and install it below the bolt head like a regular washer to monitor the axial force of the bolt. However, this method has changed the original installation standards of the connectors and cannot be widely used; The method of implanting strain gauges is similar to the method of implanting fiber Bragg gratings. Both require a small hole to be machined along the axial direction at the top of the bolt and a strain gauge (or fiber bragg grating strain sensor) to be embedded in it. The strain gauge (or fiber bragg grating strain sensor) senses the deformation of the bolt inside the bolt and measures the axial force of the bolt in real-time. This type of method changes the strength of the bolts, and the sealing of high-temperature and high-pressure devices does not allow this operation. In order to find a bolt axial force measurement method that does not cause any changes to the bolts, the patents US2012222485A1 and EP1776571A1 have released a bolt axial force 2 29 09 25 measurement system based on ultrasonic measurement technology, improving the stability and reliability of component connections. The patents CN109781332A and CN109668672A measure the acoustic time difference between the free state and tightened state of bolts by using ultrasound, calculate the elongation of bolts based on the acoustic time difference, 5 and then calculate the bolt axial force, achieving the purpose of measuring the bolt axial force. The patent CN108387338A discloses a high-precision real-time detection method and system for bolt axial force based on piezoelectric ultrasonic wafer. By utilizing the variation law of ultrasonic single wave time-of-flight difference with stress value, a high-precision fitting relationship between ultrasonic time-of-flight difference and bolt axial force is 10 established to achieve real-time detection of bolt axial force. However, these methods cannot provide long-term monitoring of the axial force of high-temperature bolts during service. In order to design an online ultrasonic probe for measuring the axial force of high-temperature bolts, this patent utilizes the characteristic that the acoustic energy is concentrated in the center of the bolt when SHO wave and AO wave propagate. A wave guide rod is designed as the acoustic propagation medium between high-temperature bolts and temperature-sensitive transducers, ensuring that the ultrasonic transducer can work stably for a long time and achieve the goal of accurately measuring the axial force of bolts 20 in high-temperature environments. SUMMARY OF THE INVENTION The technical problem to be solved by the present invention is to provide a reliable and 25 convenient ultrasonic probe for on-line measurement of axial force of high-temperature bolts in high-temperature environments. The invention is as defined in the appended claims. The present invention is achieved through the following technical solutions: 30 An integrated ultrasonic probe for on-line measurement of axial force of high-temperature bolt, is characterized in that, it comprising a piezoelectric wafer I, a piezoelectric wafer II 3 and a piezoelectric wafer III inlaid in upper damping block, a circuit board impedance matching with the piezoelectric wafer I is set on the upper surface of the upper damping block, the piezoelectric wafer II and the piezoelectric wafer III, and sealed on the upper damping block with glue line, three positive wires and three negative wires are separately connected to the positive and negative electrodes of the three piezoelectric wafers, and connect to the circuit board through the upper damping block, then connect to the threaded joint located on the outer side of the covered shell; the upper damping block is tightly close to the lower damping block of the same diameter, and tightly fixed by the inner shell, the upper end of the inner shell is embedded in the covered shell, the lower end of the inner shell is embedded in the cylinder shell; the upper ends of wave guide rod I and wave guide rod II pass through the circular back cover and the lower damping block in sequence, and are connected to the corresponding piezoelectric wafer, the lower end surfaces of wave guide rod I and wave guide rod II are closely contact with the top of the tested bolt; the top end surface of wave guide rod I is connected to the piezoelectric wafer I, and stimulate single-mode SHO waves; the left side of wave guide rod II is connected to the piezoelectric wafer II, the right side of wave guide rod II is connected to the piezoelectric wafer III, the piezoelectric wafer II and the piezoelectric wafer III are jointly motivated, and generate single-mode AO wave. The wave guide rod I and wave guide rod II are coiled sheet, and their cross sections are rectangular; the width of the wave guide rod is regarding to the ultrasonic signal wavelength A propagating within it, and the width of the wave guide rod is 5A; the thickness of the wave guide rod is 1mm; the length of the wave guide rod is calculated according to the temperature of the tested bolt by ANSYS software, and the length required is calculated which reduces the temperature t to the ambient temperature under air cooling. The piezoelectric wafer I, the piezoelectric wafer II and the piezoelectric wafer III are all cuboids, and their length are 0.9 times the width of the wave guide rod, their width are all equal to the thickness of the wave guide rods separately installed, the thickness of the piezoelectric wafer t is calculated by formula f=N I f according to the required excitation frequency, wherein f is the frequency of the piezoelectric wafer, N is piezoelectric material system; the electrode surface of the piezoelectric wafer I is either its upper surface or lower surface or any side of the piezoelectric wafer I; the polarization direction of the piezoelectric wafer I is parallel to the electrode surface; the electrode surfaces of piezoelectric wafer II and piezoelectric wafer III are either their left side or right side or on any side in contact with the wave guide rod; the polarization direction of piezoelectric wafer II and piezoelectric wafer III are vertical to the electrode surfaces, the piezoelectric wafer II and piezoelectric wafer III to excite AO waves are used at the same time, and the AO wave is received by piezoelectric wafer II; the wave guide rod and the piezoelectric wafer is connected by bonding or welding. The diameter of the upper damping block is longer than the length of the piezoelectric wafer I, the piezoelectric wafer II and the piezoelectric wafer III, and the lower surface of the upper damping block is flush with the lower surfaces of the three piezoelectric wafers. The upper end surface of the wave guide rod I is flush with the upper surface of the lower damping block, the upper end surface of the wave guide rod II is 2mm higher than the upper surface of the lower damping block; the lower surfaces of the wave guide rod I and the wave guide rod II are in the same plane, and the total length of the wave guide rod II is 3mm longer than the length of the wave guide rod I; the through slot of the lower damping block and the through slot of the circular back cover can stuck the upper part of wave guide rod I and wave guide rod II. According to different installation space requirements, the present invention also provides a split-type ultrasonic probe for measurement of axial force of high-temperature bolt, characterized in that it comprising SHO probe and AO probe, the two probes are used together; the SHO probe comprises: a piezoelectric wafer I is inlaid in upper damping block of SHO probe, the upper surfaces of upper damping block of SHO probe is set a circuit board of SHO probe impedance matching with the piezoelectric wafer I, which sealed on the upper damping block of SHO probe with glue line, two wires are separately connected to the positive and negative electrodes of the piezoelectric wafer I, and connect to the circuit board of SHO probe through the upper damping block of SHO probe, and connect to the threaded joint located on the outer side of the covered shell; the upper damping block of SHO probe is tightly close to the lower damping block of SHO probe of the same diameter, and tightly fixed by the inner shell, the upper end of the inner shell is embedded in the covered shell, the lower end of the inner shell is embedded in the cylinder shell; the upper end of the wave guide rod I passes through the circular back cover of SHO probe and the lower damping block of SHO probe, and is connected to the piezoelectric wafer I; the AO probe comprises: a piezoelectric wafer II and a piezoelectric wafer III are inlaid in upper damping block of AO probe, a circuit board of AO probe impedance matching with the piezoelectric wafer II and a piezoelectric wafer III is set on the upper surface of upper damping block of AO probe, and sealed on the upper damping block of AO probe with glue line, four wires are separately connected to the positive and negative electrodes of the piezoelectric wafer II and a piezoelectric wafer III, and connect to the circuit board of AO probe through the upper damping block of AO probe, and connect to the threaded joint located on the outer side of the covered shell; the upper damping block of AO probe is tightly close to the lower damping block of AO probe of the same diameter, and tightly fixed by the inner shell, the upper end of the inner shell is embedded in the covered shell, the lower end of the inner shell is embedded in the cylinder shell; the upper end of the wave guide rod II passes through the circular back cover of AO probe and the lower damping block of AO probe, and its left side is connected to the piezoelectric wafer II, its right side is connected to the piezoelectric wafer III. The diameter of the upper damping block of SHO probe is longer than the length of the piezoelectric wafer I, and the lower surface of the upper damping block of SHO probe is flush with the lower surface of the piezoelectric wafer I. The upper end surfaces of the wave guide rod I is flush with the upper surface of the lower damping block of SHO probe, and the through slot of the lower damping block of SHO probe and the circular back cover of SHO probe can stuck the upper part of wave guide rod I. The diameter of the upper damping block of AO probe is longer than the length of the piezoelectric wafer II and the piezoelectric wafer III, and the lower surface of the upper 6 damping block of AO probe is flush with the lower surface of the piezoelectric wafer II and the piezoelectric wafer III. The upper end surface of the wave guide rod II is 2mm higher than the upper surface of the lower damping block of AO probe; the through slot of the lower damping block of AO probe and the circular back cover of AO probe can stuck the upper part of wave guide rod II. The wave guide rod I and wave guide rod II are bent along axes parallel to the direction of their cross sections. The advantages of the present invention are: 1. The ultrasonic probe can excite SHO wave and AO wave in single mode, and determine the axial force of bolts by the velocity ratio method of AO wave and SHO wave. Due to the propagation of SHO and AO waves, the acoustic wave energy is concentrated in the center of the bolt, which reduces the interference of the threads of the bolt on the acoustic wave propagation, and enables accurate measurement of the axial force of high-temperature bolts. 2. The ultrasonic probe can be integrated or divided into SHO probe and AO probe split-type structures according to the actual installation space requirements. Integrated structure saves manufacturing costs and is easy to install; the split-type structure can be bend according to the installation environment of the tested piece, thus improving its usability in the environment. 3. The introduction of a wave guide rods in probes as an acoustic wave propagation medium between the high-temperature bolt and the temperature-sensitive piezoelectric wafer in this probe, making the piezoelectric wafer immune to high temperatures, thus ensuring that longterm monitoring of the axial force of the high-temperature bolt is possible. 4. The ultrasonic probe used to measure the axial force of high-temperature bolts will effectively reduce the tedious auxiliary work such as removing insulation and scaffolding. 5. The waveguide rod extends the monitoring signal of the tested piece from the high-temperature zone (50°C ~ 650°C) to the room temperature area for sensing, which improves the working environment of the probe's piezoelectric wafer, circuits, and other temperature-sensitive parts, and enables on-line, long-term measurements of the axial force of bolts in a high-temperature environment. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows the structural diagram of the integrated structure according to the present invention. Figure 2 shows the structural diagram of the split-type SHO probe according to the present invention. Figure 3 shows the structural diagram of the split-type AO probe according to the present invention. Figure 4 shows the stereogram of the waveguide sensor which can excite and receive SHO waves according to the present invention. Figure 5 shows the stereogram of the waveguide sensor which can excite and receive AO waves according to the present invention. Figure 6 shows the front view of the waveguide sensor which can excite and receive AO waves according to the present invention. Figure 7 shows the front view of the installation example of the integrated ultrasonic probe when there is sufficient space for axial installation of bolts according to the present invention. Figure 8 shows the left view of the installation example of the integrated ultrasonic probe when there is sufficient space for axial installation of bolts according to the present invention. Figure 9 shows the front view of the installation example of the split-type ultrasonic probe when there is limited space for axial installation of bolts according to the present invention. Figure 10 shows the top diagram of the installation example of the split-type ultrasonic probe when there is limited space for axial installation of bolts according to the present invention. Figure 11 shows the structural diagram of the second installation example of the split-type ultrasonic probe according to the present invention. Figure 12 shows the top diagram of the second installation example of the split-type ultrasonic probe according to the present invention. Figure 13 shows a working diagram of the installation example of an ultrasonic probe for wall thickness reduction measurements in extreme environments according to the present invention. REFERENCE NUMBERS IN FIGURES 1 covered shell 2 positive wire of piezoelectric wafer II 3 positive wire of piezoelectric wafer III 4 negative wire of piezoelectric wafer III 5 upper damping block 6 piezoelectric wafer III 7 piezoelectric wafer II 8 lower damping block 9 cylinder shell 10 circular back cover 11 wave guide rod II 12 thread joint 13 positive wire of piezoelectric wafer I 14 negative wire of piezoelectric wafer I 15 negative wire of piezoelectric wafer II 16 circuit board 17 piezoelectric wafer I 18 inner shell 19 wave guide rod I 20 circuit board of SHO probe 21 upper damping block of SHO probe 22 lower damping block of SHO probe 23 circular back cover of SHO probe 9 24 circuit board of AO probe 25 upper damping block of AO probe 26 lower damping block of AO probe 27 circular back cover of AO probe 28 an integrated ultrasonic probe for measurement of axial force of high-temperature bolt 29 tested bolt I 30 SHO probe 31 AO probe 32 tested bolt II 33 tested bolt III 34 flange plate 35 high temperature box DETAILED DESCRIPTION In order to be able to understand the technical content of the present invention more clearly, the following embodiments are specifically described. As shown in figure 1, an integrated ultrasonic probe for measurement of axial force of high-temperature bolt comprises: the lower end surfaces of wave guide rod I 19 and wave guide rod I111 are closely contacted with the top of the tested bolt; the upper end of wave guide rod 119 passes through the circular back cover 10 and the lower damping block 8, and tightly closes to the lower surface of the piezoelectric wafer 117; the upper end of wave guide rod II 11 passes through the circular back cover 10 and the lower damping block 8, and tightly closes to the lower surfaces of piezoelectric wafer II 7 and a piezoelectric wafer III 6. Three piezoelectric wafers inlaid in upper damping block 5, and the lower surface of the upper damping block 5 is flush with the lower surfaces of the three piezoelectric wafers. The central part of the lower damping block 8 and the circular back cover 10 are provided with through slots, two through slots stuck the upper part of wave guide rod I 19 and wave guide rod II 11; three positive wires are separately connected to the positive electrodes of the three piezoelectric wafers, three negative wires are separately connected to the negative io 29 09 25 electrodes of the three piezoelectric wafers, six wires connect to the circuit board 16 through the upper damping block 5, and connect to the threaded joint 12; the threaded joint 12 is set on the outer side of the covered shell 1; the upper damping block 5 is tightly close to the lower damping block 8, and tightly fixed by the inner shell 18, the upper end of the inner 5 shell 18 is embedded in the covered shell 1, the lower end of the inner shell 18 is embedded in the cylinder shell 9. As shown in figure 2, the SHO probe comprises: the lower end surface of the wave guide rod I 19 is closely contacted with the top of the tested bolt, the upper end of wave guide rod 10 119 passes through the circular back cover of SHO probe 23 and the lower damping block of SHO probe 22, and tightly closes to the lower surface of the piezoelectric wafer 117. The piezoelectric wafer 117 is inlaid in upper damping block of SHO probe 21, the lower surface of the piezoelectric wafer I 17 is flush with the lower surface of the upper damping block of SHO probe 21. The central part of the circular back cover of SHO probe 23 and the lower damping block of SHO probe 22 are provided with through slots, the diameter of the lower damping block of SHO probe 22 is longer than the length of the through slot. Two through slots can stuck the upper part of wave guide rod I 19; the piezoelectric wafer I 17 is connected to the circuit board of SHO probe 20 by wires and is connected to the threaded joint 12; the lower surface of the upper damping block of SHO probe 21 is tightly close to the 20 upper surfaces of the lower damping block of SHO probe 22, and tightly fixed by the inner shell 18, the upper end of the inner shell 18 is embedded in the covered shell 1, the lower end of the inner shell 18 is embedded in the cylinder shell 9. As shown in figure 3, the AO probe comprises: the lower end surface of the wave guide rod 25 I111 is closely contacted with the top of the tested bolt, the upper end of wave guide rod II 11 passes through the circular back cover of AO probe 27 and the lower damping block of AO probe 26, and tightly closes to the right surface of the piezoelectric wafer II7 and the left surface of the piezoelectric wafer III 6. The piezoelectric wafer II 7 and the piezoelectric wafer III 6 are both inlaid in upper damping block of AO probe 25, their lower surfaces are 30 flush with the lower surface of the upper damping block of A0 probe 25. The central part of the circular back cover of A0 probe 27 and the lower damping block of A0 probe 26 are ii provided with through slots, the diameter of the lower damping block of AO probe 26 is longer than the length of the through slot. Two through slots can stuck the upper part of wave guide rod I111; the piezoelectric wafer II 7 and the left surface of the piezoelectric wafer III 6 are connected to the circuit board of AO probe 24 by wires and are connected to the threaded joint 12; the upper damping block of AO probe 25 is tightly close to the upper surface of the lower damping block of AO probe 26, and tightly fixed by the inner shell 18, the upper end of the inner shell 18 is embedded in the covered shell 1, the lower end of the inner shell 18 is embedded in the cylinder shell 9. As shown in figure 4, the upper and lower surfaces of piezoelectric wafer 117 are electrode surfaces, the polarization directions are vertical to the electrode surfaces. The positive wire of piezoelectric wafer 113 is connected to the positive electrode of the upper surface of the piezoelectric wafer I 17, the negative wire of piezoelectric wafer I 14 is connected to negative electrode of other surfaces. The center of the cross-section of the piezoelectric wafer I 17 coincides with the center of the upper end face of the upper part of wave guide rod I 19, the lower surface of the piezoelectric wafer I 17 is parallel to the upper surface of the wave guide rod I 19, the joints can be bonded or welded. The combination of piezoelectric wafer 117 and wave guide rod I 19 can excite and receive SHO waves. As shown in figure 5 and figure 6, the left and right sides of piezoelectric wafer II 7 and piezoelectric wafer III 6 are electrode surfaces, the polarization directions are vertical to the electrode surfaces. The positive wire of piezoelectric wafer II 2 is connected to the positive electrode of the left surface of the piezoelectric wafer II 7, and the negative wire of piezoelectric wafer II 15 is connected to the negative electrode of the front surface of the piezoelectric wafer II 7. The positive wire of piezoelectric wafer III 3 is connected to the positive electrode of the right surface of the piezoelectric wafer III 6, the negative wire of piezoelectric wafer III 4 is connected to the negative electrode of the front surface of the piezoelectric wafer III 6. The right surface of the piezoelectric wafer II 7 is connected to the left surface of the wave guide rod II 11, the left surface of the piezoelectric wafer III 6 is connected to the right surface of the wave guide rod II 11, the joints can be bonded or welded, two piezoelectric wafers are symmetrically installed on the left surface and right 12 surface of wave guide rod I111, and are 1 mm from the upper end face of wave guide rod II 11. The combination of piezoelectric wafer II 7, piezoelectric wafer III 6 and the wave guide rod I111 can excite and receive AO waves. As shown in figure 7 and figure 8, when there is sufficient space for axial installation of bolts, an integrated ultrasonic probe for on-line measurement of axial force of high-temperature bolt 28 is selected, the bottom of two wave guide rods is contact to the top of the tested bolt I 29. As shown in figure 9 and figure 10, when there is limited space for axial installation of bolts, a split-type ultrasonic probe for measurement of axial force of high-temperature bolt is selected. The lower surfaces of wave guide rod I 19 and wave guide rod I111 are contact to the upper end of the tested bolt II 32, the SHO probe 30 and the A0 probe 31 are bend to both sides. As shown in figure 11 and figure 12, when the temperature near the center of flange plate 34 is high, the SHO probe 30 and A0 probe 31 can be bent outward to reduce the impact of temperature on the probe. The two installation structures of an ultrasonic probe for measurement of axial force of high-temperature bolt of the present invention have the same working principle. As an example of the integrated structure, the working principle is explained as follows: The piezoelectric wafer I 17 generates vibration and excites SHO wave under voltage excitation, which passes through the wave guide rod I 19 and propagates into the tested bolt 129. The reflected return wave at the bottom of the bolt returns through the wave guide rod 119 and is sensed by the piezoelectric wafer 117 and converted into an electrical signal; the piezoelectric wafer II 7 and the piezoelectric wafer III 6 generates vibration together under voltage excitation, excite A0 wave, which passes through the wave guide rod II 11 and propagates into the tested bolt 129, the reflected return wave returns through the wave guide rod II 11 and is sensed by the piezoelectric wafer II 7 and the piezoelectric wafer III 6 and converted into an electrical signal. Using the SHO wave received by piezoelectric wafer I 17 and the A0 wave received by piezoelectric wafer II 7, the preloading force of the 13 bolt is calculated by using the velocity ratio method of the AO wave and the SHO wave. 29 09 25 Since sound waves propagate in all directions when a piezoelectric wafer is electrically excited, the part of the acoustic wave is incident on the waveguide rod for monitoring 5 purposes, and part of the acoustic wave is incident on the wave guide rod when it reflects from the interface inside the probe, these waves are clutter for monitoring purposes. Therefore, a upper damping block is designed inside the probe to absorb the interfering clutter away; furthermore, when an electrical excitation is applied to the piezoelectric wafer, the piezoelectric wafer begins to vibrate, the upper damping block also has damping action 10 on the piezoelectric wafer, to make the piezoelectric wafer stop as soon as possible, and reduce the aftershock, decrease the ultrasonic pulse width, and improve the ultrasonic detection resolving power; the upper damping blocks and lower damping blocks are mainly sound-absorbing materials made of epoxy resin, curing agent, rubber, calcium powder, red lead etc., which are proportionally blended and poured directly around the piezoelectric wafer. The lower damping block is harder than the upper block and serves to hold the piezoelectric wafer and wave guide rods in place, while the upper block is slightly softer and serves to protect the wires. The material of circular back cover 10, circular back cover of SHO probe 23, circular back 20 cover of AO probe 27 can select alumina (corundum) film, which is a commonly used hard protective film for the probe to protect the damping block from contamination and damage in the working environment. The threaded joint 12 is connected to an external wire and is connected to the signal 25 acquisition device. Implementation case: According to the two different working conditions of sufficient installation space and limited installation space, the integrated ultrasonic probe and the split-type SHO probe and AO probe 30 are designed and processed respectively. The piezoelectric wafer I 17, piezoelectric wafer II 7, piezoelectric wafer III 6 are of 2-2 composite material, the circular back cover 10, 14 29 09 25 circular back cover of SHO probe 23, and circular back cover of AO probe 27 are of aluminium oxide (corundum), the inner shell 18 is of Teflon (RTM), the upper damping block 5, upper damping block of SHO probe 21 and upper damping block of AO probe 25 are of cement material, the lower damping block 8, lower damping block of SHO probe 22 and lower 5 damping block of AO probe 26 are of cement material with added silicon powder, and the covered shell (cover shell) 1 is of hard aluminum alloy 2219. The material of wave guide rod 119 and piezoelectric wafer I111 is 42CrMo stainless steel, the thicknesses is 1mm, the widths is 20mm, the length of wave guide rod I 19 is 300mm, 10 the length of wave guide rod I111 is 303mm. The thicknesses of piezoelectric wafer 117, piezoelectric wafer II7, piezoelectric wafer III 6 are 1mm, the widths are 1mm, the length is 18mm, impedance matching between circuit board 16 and piezoelectric wafer I 17, piezoelectric wafer II7 and piezoelectric wafer III 6, is assembled from commercially available resistors, capacitors and other components. The present invention selects the following specifications of the fittings of Guangdong Fenghua High-Tech Company: capacitor model: CC4-0805N200J500F3, resistor model: RC-MTO8W512JT, inductor model: LGA0204-221KP52E. 20 The tested sample is the bolt which the size is M24mm x 95mm, the tested bolt is put into the high temperature box 35, two slot holes are opened in the upper part of high-temperature box 35, the integrated ultrasonic probe and the split-type SHO probe and A0 probe are used respectively under different operating conditions: The lower end surfaces of the wave guide rod 119 and wave guide rod I111 of the probes are inserted into the slotted holes of the high 25 temperature box 35 from top to bottom, and the wave guide rod I 19 and wave guide rod II 11 are welded to the top of the bolt. Except for the lower portion of wave guide rod I 19 and wave guide rod II 11, the rest of the ultrasound probe of the present invention is placed outside of the high temperature chamber 35 and is connected to the signal acquisition instrument by wires. The temperature of the high temperature box is heated to 300°C, and 30 measure the temperature after keeping warm for 20 minutes, the measurement results of the integrated and split-type probes are the same, both 95.2mm, tolerance is 2%, meeting 15 engineering requirements. In this specification, the present invention has been described with reference to its specific embodiments. However, it is clear that various modifications and changes can still be made 5 without departing from the spirit and scope of the present invention. Therefore, the description and drawings should be regarded as illustrative rather than restrictive.

Claims

1. An integrated ultrasonic probe for on-line measurement of an axial force in a high-temperature bolt, the integrated ultrasonic probe comprising:a first piezoelectric wafer I (17), a second piezoelectric wafer n (7) and a third piezoelectric wafer m (6), each of the first, second and third piezoelectric wafers I, II, III (17, 7, 6) being inlaid in an upper damping block (5),a circuit board (16) impedance-matched with the first piezoelectric wafer I(17), the second piezoelectric wafer n (7) and the third piezoelectric wafer m (6), the circuit board being set on an upper surface of the upper damping block (5), and the circuit board being sealed on the upper damping block (5) with a glue line,wherein three positive wires and three negative wires are separately connected to respective positive and negative electrodes of the respective first, second and third piezoelectric wafers I, II, III, each wire being connected to the circuit board (16) through the upper damping block (5), and then connected to a threaded joint (12) located on an outer side of a cover shell (1) of the integrated ultrasonic probe;wherein the upper damping block (5) is tightly close to a lower damping block (8) of the same diameter as the upper damping block (5), the upper damping block (5) and the lower damping block (8) being tightly fixed together by an inner shell (18),wherein an upper end of the inner shell (18) is embedded in the cover shell (1), and a lower end of the inner shell (18) is embedded in a cylinder shell (9);wherein respective upper ends of a first wave guide rod I (19) and a second wave guide rod n (11) pass through a circular back cover (10) and the lower damping block (8) in sequence,wherein, in use, respective lower end surfaces of the first wave guide rod I (19) and the second wave guide rod n (11) are closely in contact with the top of the bolt;wherein an upper end surface of the first wave guide rod I (19) is connected to the first piezoelectric wafer I (17), such that single-mode SH0 waves can be generated by the first piezoelectric wafer I (17) and transmitted through the first wave guide rod I (19) into the bolt, and such that reflected SH0 waves can return through the first wave guide rod I (19) for sensing by the first piezoelectric wafer I (17);wherein a left side of the second wave guide rod n (11) is connected to the second piezoelectric wafer n (7), a right side of the second wave guide rod n (11) is connected to the third piezoelectric wafer m(6), the second piezoelectric wafer n (7) and the thirdpiezoelectric wafer m (6) being jointly motivated, such that single-mode A0 waves can be generated by the second and third piezoelectric wafers II, III (11, 6) and transmitted through the second wave guide rod n (11) into the bolt, and such that reflected A0 waves can return through the second wave guide rod n (11) for sensing by the second and third piezoelectric wafers II, III (11, 6).

2. The integrated ultrasonic probe according to claim 1, wherein the first wave guide rod I (19) and the second wave guide rod n (11) are strip-shaped thin plates with rectangular cross-sections;wherein the width of each of the wave guide rods (19, 11) is related to the ultrasonic signal wavelength A propagating within it, with the width of the respective wave guide rod equal to 5A;and wherein the thickness of each of the wave guide rods is 1mm.

3. The integrated ultrasonic probe according to claim 1, wherein the first piezoelectric wafer I (17), the second piezoelectric wafer n (7) and the third piezoelectric wafer m (6) are all cuboids, each of the first, second and third piezoelectric wafers I, II, III (17, 7, 6) having:a length that is 0.9 times a width of the respective first and second wave guide rod I, II (19, 11) to which the corresponding piezoelectric wafer is mounted,a width that is equal to a thickness of the respective first or second wave guide rod I, II (19, 11) to which the corresponding piezoelectric wafer is mounted, anda thickness t calculated by the formula t —N / f according to the required excitation frequency, in which f is the frequency of the piezoelectric wafer and N is the piezoelectric material system;wherein an electrode surface of the first piezoelectric wafer I (17) is either its upper surface or lower surface or any side of the piezoelectric wafer I (17) and a polarization direction of the first piezoelectric wafer I (17) is parallel to the electrode surface of the first piezoelectric wafer I (17);wherein the electrode surface of the second piezoelectric wafer n (7) and the electrode surface of the third piezoelectric wafer m (6) are respectively either their left side or right side or any side in contact with the second wave guide rod n (11) and the polarization directions of the second piezoelectric wafer n (7) and the thirdpiezoelectric wafer m (6) are perpendicular to the respective electrode surfaces of the second piezoelectric wafer n (7) and the third piezoelectric wafer m (6),wherein the second piezoelectric wafer n (7) and the third piezoelectric wafer m (6) are used simultaneously to excite A0 waves, and the A0 wave is received by the second piezoelectric wafer n (7);and wherein the wave guide rods and the respective piezoelectric wafers are connected by bonding or welding.

4. The integrated ultrasonic probe according to claim 1, wherein the upper damping block (5) has a diameter that is longer than the respective lengths of the first piezoelectric wafer I (17), the second piezoelectric wafer n (7) and the third piezoelectric wafer m (6), and wherein a lower surface of the upper damping block (5) is flush with respective lower surfaces of each of the first, second and third piezoelectric wafers.

5. The integrated ultrasonic probe according to claim 1, wherein the upper end surface of the first wave guide rod I (19) is flush with an upper surface of the lower damping block (8), and an upper end surface of the second wave guide rod n (11) is 2mm higher than the upper surface of the lower damping block (8);wherein the respective lower end surfaces of the first wave guide rod I (19) and the second wave guide rod n (11) are in the same plane, and the total length of the second wave guide rod n (11) is 3mm longer than the length of the first wave guide rod I (19);and wherein respective through slots of the lower damping block (8) and respective through slots of the circular back cover (10) clamp respective upper parts of the first wave guide rod I (19) and the second wave guide rod n (11).

6. A split-type ultrasonic probe apparatus for measurement of an axial force in a high-temperature bolt, the split-type ultrasonic probe apparatus comprising an SH0 probe (30) and an A0 probe (31), the two probes being used in conjunction to measure the axial force in use of the apparatus;the SH0 probe (30) comprising:a first piezoelectric wafer I (17), inlaid in an upper damping block of the SH0 probe (30);a circuit board (20) of the SH0 probe, impedance matched with the first piezoelectric wafer I (17), the circuit board (20) of the SH0 probe being set on an upper surface of the upper damping block (21) of the SH0 probe and sealed on the upper damping block (21) of the SH0 probe with a glue line,wherein two wires are separately connected to respective positive and negative electrodes of the first piezoelectric wafer I (17), each wire being connected to the circuit board (20) of the SH0 probe through the upper damping block (21) of the SH0 probe, and then connected to a threaded joint (12) of the SH0 probe located on an outer side of a cover shell (1) of the SH0 probe;wherein the upper damping block (21) of the SH0 probe is tightly close to a lower damping block (22) of the SH0 probe of the same diameter as the upper damping block (21) of the SH0 probe, the upper damping block (21) and the lower damping block (20) of the SH0 probe being tightly fixed together by an inner shell (18) of the SH0 probe,wherein an upper end of the inner shell (18) of the SH0 probe is embedded in the cover shell (1) of the SH0 probe, and a lower end of the inner shell (18) of the SH0 probe is embedded in a cylinder shell (9) of the SH0 probe;and wherein an upper end of a first wave guide rod I (19) passes through a circular back cover (23) of the SH0 probe and the lower damping block (22) of the SH0 probe, and an upper end surface of the first wave guide rod I (19) is connected to the first piezoelectric wafer I(17), such that single-mode SH0 waves can be generated by the first piezoelectric wafer I (17) and transmitted through the first wave guide rod I (19) into the bolt, and such that reflected SH0 waves can return through the first wave guide rod I (19) for sensing by the first piezoelectric wafer I (17);and the A0 probe (31) comprising:a second piezoelectric wafer n (7) and a third piezoelectric wafer M (6) inlaid in an upper damping block (25) of the A0 probe,a circuit board (24) of the A0 probe impedance matched with the second piezoelectric wafer n (7) and the third piezoelectric wafer n (6), the circuit board (24) of the A0 probe being set on an upper surface of the upper damping block (25) of the A0 probe and sealed on the upper damping block (25) of the A0 probe with a glue line, wherein four wires are separately connected to the respective positive and negative electrodes of the second piezoelectric wafer n (7) and the third piezoelectricwafer in (6), each wire being connected to the circuit board (24) of the A0 probe through the upper damping block (25) of the A0 probe, and then connected to a threaded joint (12) of the A0 probe located on an outer side of a cover shell (1) of the A0 probe;wherein the upper damping block (25) of the A0 probe is tightly close to a lower damping block (26) of the A0 probe of the same diameter as the upper damping block of the A0 probe, the upper damping block (25) of the A0 probe and the lower damping block (26) of the A0 probe being tightly fixed together by an inner shell (18) of the A0 probe,wherein an upper end of the inner shell (18) of the A0 probe is embedded in the cover shell (1) of the A0 probe, and a lower end of the inner shell (18) of the A0 probe is embedded in a cylinder shell (9) of the A0 probe;and wherein an upper end of a second wave guide rod n (11) passes through a circular back cover (27) of the A0 probe and the lower damping block of the A0 probe (26), a left side of the second wave guide rod n is connected to the second piezoelectric wafer n (7), and a right side of the second wave guide rod n is connected to the third piezoelectric wafer M (6), such that single-mode A0 waves can be generated by the second and third piezoelectric wafers II, III (11, 6) and transmitted through the second wave guide rod n (11) into the bolt, and such that reflected A0 waves can return through the second wave guide rod n (11) for sensing by the second and third piezoelectric wafers II, III (11, 6).

7. The split-type ultrasonic probe apparatus according to claim 6,wherein a diameter of the upper damping block (21) of the SH0 probe is longer than the length of the first piezoelectric wafer I (17),wherein a lower surface of the upper damping block (21) of the SH0 probe is flush with a lower surface of the first piezoelectric wafer I (17);wherein a diameter of the upper damping block (25) of the A0 probe is longer than respective lengths of the second piezoelectric wafer n (7) and the third piezoelectric wafer m (6),and wherein a lower surface of the upper damping block (25) of the A0 probe is flush with respective lower surfaces of the second piezoelectric wafer n (7) and the third piezoelectric wafer m (6).

8. The split-type ultrasonic probe apparatus according to claim 6, wherein the upper end surface of the first wave guide rod I(19) is flush with an upper surface of the lower damping block (22) of the SH0 probe, and respective through slots of the lower damping block of the SH0 probe (22) and the circular back cover of the SH0 probe (23) clamp an upper part of the first wave guide rod I (19);and wherein an upper end surface of the second wave guide rod n (11) is 2mm higher than an upper surface of the lower damping block of the A0 probe (26); and respective through slots of the lower damping block of the A0 probe (26) and the circular back cover of the A0 probe (27) clamp the upper part of the second wave guide rod n (11).

9. The split-type ultrasonic probe apparatus according to claim 6, wherein the first wave guide rod I (19) and the second wave guide rod n (11) are bent along respective axes parallel to the direction of their respective cross sections.

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