In-situ ultrasonic detection method for double-order T-shaped blade root of low-pressure rotor

Abstract

The invention discloses an in-situ ultrasonic detection method for a double-step T-shaped blade root of a low-pressure rotor, which breaks through the bottleneck of complex sound path caused by double steps of the double-step T-shaped blade root through sectional detection logic of same-side scanning, opposite-side scanning and auxiliary wedge block scanning. The non-blind area coverage of the full stress concentration area is realized, and the problem of incomplete coverage of a traditional single process is solved. CIVA simulation and artificial defect test block calibration are introduced at the same time, blind setting of parameters is avoided, scanning feasibility is verified in advance through simulation, a unified judgment benchmark is established through calibration, and the omission ratio and the misjudgment rate are greatly reduced. And whole-course in-situ detection can be realized without disassembling the steam turbine rotor, so that the detection cost and the downtime are greatly reduced, and the on-site detection requirements of a power plant are met. In addition, by designing and machining an auxiliary wedge block for detection, the problem that detection cannot be achieved due to a blade root inclined structure is solved.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic inspection in nuclear power plants, and more particularly to an in-situ ultrasonic testing method for the root of a low-pressure rotor with a two-stage T-shaped blade. Background Technology

[0002] Steam turbines are one of the most important pieces of equipment in power plants, and their operating conditions directly affect power generation efficiency and the safe and stable operation of the power plant. Blades are a critical component of steam turbines, with the blade root, which connects to the rotor impeller, enduring complex effects of centrifugal force, vibration, and thermal stress during operation, making it highly susceptible to defects. Therefore, to ensure the safe and stable operation of power plants and to promptly detect and eliminate equipment defects, periodic inspections of steam turbine blade roots are now widely implemented. These inspections include non-destructive testing methods such as eddy current testing, penetrant testing, and ultrasonic testing. Among these, ultrasonic testing is widely used in on-site non-destructive testing of blade roots due to its strong penetrating power, adaptability to complex shapes, and high sensitivity.

[0003] Leaf roots commonly exhibit structural forms such as T-shaped, forked, fungal, and fir-shaped. In recent years, T-shaped leaf roots have further evolved into oblique T-shaped, shouldered T-shaped, and double-step T-shaped types. This paper studies an oblique double-step T-shaped leaf root, characterized by double-step and inclined steps. Traditional detection techniques cannot meet the scanning requirements, and there are currently no reports on defect detection techniques or implementation cases for this type of leaf root, both domestically and internationally; therefore, related technical research remains incomplete. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an in-situ ultrasonic testing method for the root of a low-pressure rotor with two-stage T-shaped blades.

[0005] The technical solution adopted by this invention to solve its technical problem is: to construct an in-situ ultrasonic testing method for the root of a low-pressure rotor with a double-stage T-shaped blade, which includes the following steps: S1. Prepare an artificial defect test block. The artificial defect test block has an outlet side A step and an inlet side B step corresponding to the double-stage T-shaped blade root. The artificial defect test block is provided with R1 angle, R2 angle and R3 angle distributed sequentially along the blade body to the blade root direction. S2. Design the probe and auxiliary wedge based on CIVA simulation, and determine the matching parameters between the probe and the auxiliary wedge; S3. Use the artificial defect test block prepared in step S1 to perform benchmark sensitivity calibration; S4. Use a probe to scan the defects at the R1 corner on the same side of the outlet side A step and the inlet side B step respectively; S5. Use a probe to scan for defects at the R2 and R3 angles on the opposite sides of the outlet side A step and the inlet side B step, respectively. S6. Based on step S5, add an auxiliary wedge to the probe to deflect the incident sound beam surface, and then scan the defects at the R2 and R3 angles again on the opposite side of the outlet side A step and the inlet side B step. S7. Analyze and process the ultrasonic signals obtained in steps S4, S5, and S6 to identify leaf root structure signals and defect signals, and complete the in-situ ultrasonic detection of the double-order T-shaped leaf root.

[0006] In some embodiments, in step S1, two artificial defects are provided at each end of the R1 angle of the outlet side A step and the inlet side B step of the artificial defect test block, respectively denoted as F1, F2, F3 and F4, wherein F1 and F2 are located at the R1 angle of the outlet side A step, and F3 and F4 are located at the R1 angle of the inlet side B step. There are two artificial defects at each end of the R2 corner of the outlet side A step and the inlet side B step, respectively, which are labeled F5, F6, F7 and F8. F5 and F6 are located at the R2 corner of the outlet side A step, and F7 and F8 are located at the R2 corner of the inlet side B step. There are two artificial defects at each end of the R3 corner of the outlet side A step and the inlet side B step, respectively denoted as F9, F10, F11 and F12. F9 and F10 are located at the R3 corner of the outlet side A step, and F11 and F12 are located at the R3 corner of the inlet side B step.

[0007] In some embodiments, the artificial defects F1-F12 are all artificial grooves, and the size of the artificial grooves is 0.5mm×5mm; wherein, F1-F4 and F5-F8 are machined at the lower edge of the R1 corner and the R2 corner respectively, and F9-F12 are machined at the center of the R3 corner.

[0008] In some embodiments, in step S2, during the CIVA simulation process, same-side scanning, opposite-side scanning, and auxiliary wedge deflection incident surface scanning are simulated respectively to verify the detectability of defects at R1, R2, and R3 angles; When simulating same-side scanning, the structural signal of corner R1 and the defect signal of artificial defects at corner R1 are acquired; When simulating the opposite side scan, the structural signal of corner R2, the defect signal of the artificial defect at corner R2, and the defect signal of the artificial defect at corner R3 are acquired. When simulating the auxiliary wedge deflection incident surface scanning, the probe scans the opposite side, and by deflecting the incident sound beam surface, the auxiliary wedge deflects the incident surface to obtain the structural signal of the R2 angle, the defect signal of the artificial defect at the R2 angle, and the defect signal of the artificial defect at the R3 angle.

[0009] In some embodiments, in step S2, the probe is a planar array transverse wave angle probe with a frequency of 5.0MHz, an array element specification of 6×4, an element spacing of 1.0mm×1.5mm, an element gap of 0.1mm, and 24 wafers. It adopts an integrated wedge block with an acoustic wave incident angle of 36°.

[0010] In some embodiments, in step S4, a continuous scan is performed on step A on the outlet side along a direction parallel to the blade root length to obtain structural signals of angles R1 and R2, and defect signals of artificial defects F1 and F2. The intake side B step is continuously scanned at two depth positions along the direction parallel to the blade root length. The two depth positions are the depth position close to the R1 angle and the depth position far away from the R1 angle, respectively. When scanning at the depth position close to the R1 angle on the intake side B step, the structural signal of the R2 angle and the defect signals of artificial defects F3 and F4 are obtained. When scanning at the depth position far away from the R1 angle on the intake side B step, the structural signal of the R1 angle and the defect signals of artificial defects F3 and F4 are obtained.

[0011] In some embodiments, in step S5, without an auxiliary wedge, the structural signal of the R2 angle and the defect signals of artificial defects F8 and F12 are obtained by scanning the A step on the air outlet side. The structural signal of the R2 angle and the defect signals of artificial defects F5 and F9 were obtained by scanning the B step on the intake side.

[0012] In some embodiments, in step S6, an auxiliary wedge is added to scan and obtain the structural signal of the R2 angle and the defect signals of artificial defects F7 and F11 on the A step of the air outlet side; The structural signal of the R2 angle and the defect signals of artificial defects F6 and F10 were obtained by scanning the B step on the intake side.

[0013] In some embodiments, in steps S4, S5, and S6, the ultrasonic testing equipment uses amplitude display, sector display, and planar display modes to display the artificial defect test block, wherein the horizontal axis of the planar display mode is the probe scanning direction, and the vertical axis is the sound beam propagation direction.

[0014] In some embodiments, in the signal analysis and processing of step S7, by comparing the positional differences between the structural signals and defect signals obtained by the fan-shaped display method, the differences between the signal amplitude and waveform obtained by the amplitude display method, and the signal continuity obtained by the planar display method, the R1 and R2 angle structural signals of the double-order T-shaped leaf root and the defect signals corresponding to each artificial defect are distinguished, and the existence and location of defects are determined.

[0015] The implementation of this invention has the following beneficial effects: This in-situ ultrasonic testing method for the double-step T-shaped blade root of a low-pressure rotor overcomes the bottleneck of complex acoustic paths caused by the double-step structure of the double-step T-shaped blade root through a segmented testing logic of same-side scanning, opposite-side scanning, and auxiliary wedge scanning. It achieves blind-spot-free coverage of the entire stress concentration area, solving the problem of incomplete coverage by traditional single-process methods. Furthermore, it introduces CIVA simulation and artificial defect block calibration to avoid blind parameter setting. Simulation verifies the feasibility of the scanning in advance, and calibration establishes a unified judgment benchmark, significantly reducing the missed detection rate and false judgment rate. It also enables in-situ testing throughout the entire process without disassembling the turbine rotor, significantly reducing testing costs and downtime, and adapting to the on-site testing needs of power plants. In addition, the design and fabrication of auxiliary wedges for testing solves the problem of inaccessibility caused by the tilted blade root structure. Attached Figure Description

[0016] To more clearly illustrate the technical solution of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be understood that the following drawings only show some embodiments of the present invention and therefore should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram of the overall process of the in-situ ultrasonic testing method for the root of a low-pressure rotor double-stage T-shaped blade in some embodiments of the present invention. Figure 2 These are schematic diagrams of the artificial defect test block structure in some embodiments of the present invention; Figure 3 This is a schematic diagram of the structure at step A on the vent side of the artificial defect test block in some embodiments of the present invention; Figure 4 This is a schematic diagram of the structure at step B on the air inlet side of the artificial defect test block in some embodiments of the present invention. Detailed Implementation

[0017] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described in detail with reference to the accompanying drawings. In the following description, it should be understood that the orientations or positional relationships indicated by terms such as "front," "rear," "upper," "lower," "left," "right," "longitudinal," "horizontal," "vertical," "horizontal," "top," "bottom," "inner," "outer," "head," and "tail" are based on the orientations or positional relationships shown in the accompanying drawings, and are constructed and operated in a specific orientation. They are only for the convenience of describing this technical solution and do not indicate that the device or element referred to must have a specific orientation; therefore, they should not be construed as limitations on this invention.

[0018] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "linking," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. When an component is referred to as being "on" or "below" another component, the component can be located "directly" or "indirectly" on the other component, or there may be one or more intermediary components. The terms "first," "second," "third," etc., are only for the convenience of describing this technical solution and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0019] Please see Figures 2 to 4 This is a schematic diagram of an artificial defect test block in some embodiments of the present invention, such as... Figure 1 The diagram shown is a schematic of the overall process for in-situ ultrasonic testing of the root of a low-pressure rotor with a double-stage T-shaped blade. The process includes the following steps: S1. Prepare an artificial defect test block. The artificial defect test block has an outlet side A step and an inlet side B step corresponding to the double-stage T-shaped blade root. The artificial defect test block has R1 angle, R2 angle and R3 angle distributed sequentially along the blade body to the blade root direction. S2. Design the probe and auxiliary wedge based on CIVA simulation, and determine the matching parameters between the probe and the auxiliary wedge; S3. Use the artificial defect test block prepared in step S1 to perform reference sensitivity calibration; S4. Use a probe to scan the R1 corner on the same side of the outlet side A step and the inlet side B step respectively; S5. Use a probe to scan for defects at the R2 and R3 angles on the opposite sides of the outlet side A step and the inlet side B step, respectively. S6. Based on step S5, add an auxiliary wedge to the probe to deflect the incident sound beam surface, and then scan the defects at the R2 and R3 angles again on the opposite side of the outlet side A step and the inlet side B step. S7. Analyze and process the ultrasonic signals obtained in steps S4, S5, and S6 to identify leaf root structure signals and defect signals, and complete the in-situ ultrasonic detection of the double-order T-shaped leaf root.

[0020] Understandably, the current double-stage T-shaped blade root has two steps, resulting in a complex ultrasonic beam propagation path and mutual interference between the two steps, making it difficult for traditional single-inspection processes to cover the entire detection range. The complex structure of the double-stage T-shaped blade root also presents an angular deviation between the probe's detection surface and the opposite inspection surface, requiring simulation and experimental determination of the effective detection area. There are three stress concentration areas (R-angles) on the double-stage T-shaped blade root, located on different steps, demanding a high coverage range from the ultrasonic testing system. To address these issues, this in-situ ultrasonic testing method for the low-pressure rotor double-stage T-shaped blade root incorporates a probe and auxiliary wedges. Blade root scanning is performed on the outlet side (step A) and the inlet side (step B). For defects at position R1, a same-side scanning process is used; for defects at positions R2 and R3, a opposite-side scanning process is used. During opposite-side scanning, due to the tilted structure of the blade root, auxiliary wedges are added to deflect the incident acoustic beam surface in certain areas. Same-side scanning refers to placing the probe on step A on the exhaust side or step B on the intake side to scan for R-angle defects belonging to the same side of that step. Opposite-side scanning refers to placing the probe on step A on the exhaust side or step B on the intake side to scan for R-angle defects belonging to the opposite side of that step. Step S3 uses the artificial defect test block prepared in S1 to calibrate the baseline sensitivity. The probe scans the artificial defects F1-F12 on the test block, recording the baseline amplitude and propagation time of each defect signal. This data serves as the baseline for defect judgment in subsequent actual testing, avoiding detection errors caused by fluctuations in equipment sensitivity.

[0021] This in-situ ultrasonic testing method for the double-step T-shaped blade root of a low-pressure rotor overcomes the bottleneck of complex acoustic paths caused by the double-step structure of the blade root through a segmented testing logic of same-side scanning, opposite-side scanning, and auxiliary wedge scanning. It achieves blind-spot-free coverage of the entire stress concentration area, solving the problem of incomplete coverage by traditional single-process methods. Furthermore, it introduces CIVA simulation and manual defect block calibration to avoid blind parameter setting. Simulation verifies the feasibility of the scanning in advance, and calibration establishes a unified judgment benchmark, significantly reducing the missed detection rate and false judgment rate. It also enables in-situ testing throughout the entire process without disassembling the turbine rotor, significantly reducing testing costs and downtime, and adapting to the on-site testing needs of power plants. In addition, the design and fabrication of auxiliary wedges for testing solves the problem of inaccessibility caused by the tilted blade root structure.

[0022] like Figures 2 to 4As shown, in step S1, two artificial defects are provided at each end of the R1 angle of the outlet side A step and the inlet side B step of the artificial defect test block, respectively denoted as F1, F2, F3, and F4. F1 and F2 are located at the R1 angle of the outlet side A step, and F3 and F4 are located at the R1 angle of the inlet side B step. Two artificial defects are provided at each end of the R2 angle of the outlet side A step and the inlet side B step, respectively denoted as F5, F6, F7, and F8. F5 and F6 are located at the R2 angle of the outlet side A step, and F7 and F8 are located at the R2 angle of the inlet side B step. Two artificial defects are provided at each end of the R3 angle of the outlet side A step and the inlet side B step, respectively denoted as F9, F10, F11, and F12. F9 and F10 are located at the R3 angle of the outlet side A step, and F11 and F12 are located at the R3 angle of the inlet side B step.

[0023] Specifically, Figure 2 This is a schematic diagram of the artificial defect test block structure in some embodiments of the present invention. In the figure, step A corresponds to step A on the air outlet side, and step B corresponds to step B on the air inlet side. Figure 3 This is a schematic diagram of the structure of the artificial defect test block at step A on the gas outlet side in some embodiments of the present invention. In the figure, F1 and F2 correspond to the artificial defects at corner R1 on the side of step A on the gas outlet side, F5 and F6 correspond to the artificial defects at corner R2 on the side of step A on the gas outlet side, and F9 and F10 correspond to the artificial defects at corner R3 on the side of step A on the gas outlet side. Figure 4 This is a schematic diagram of the structure of the artificial defect test block at step B on the air intake side in some embodiments of the present invention. In the figure, F3 and F4 correspond to artificial defects at corner R1 on the side of step B on the air intake side, F7 and F8 correspond to artificial defects at corner R2 on the side of step B on the air intake side, and F11 and F12 correspond to artificial defects at corner R3 on the side of step B on the air intake side.

[0024] Understandably, this artificial defect test block corresponds to step A on the exhaust side and step B on the intake side of the blade root, replicating the size and tilt angle of the double steps. Angles R1, R2, and R3 are sequentially set along the blade body to the blade root, replicating the radius and spatial position of the actual blade root's R-angles. Simultaneously, artificial defects are set according to the tendency of defects to develop: F1 and F2 are set on side A at both ends of angle R1, and F3 and F4 on side B. F5 and F6 are set on side A at both ends of angle R2, and F7 and F8 on side B. F9 and F10 are set on side A at both ends of angle R3, and F11 and F12 on side B. This design covers all critical areas, avoiding calibration failures caused by mismatch between the test block and the actual blade root structure, ensuring that the calibrated testing method can be directly transferred to actual blade root testing without additional parameter adjustments, thus improving process versatility.

[0025] Artificial defects F1-F12 are all manually grooved, with a size of 0.5mm × 5mm. F1-F4 and F5-F8 are machined at the lower edges of corners R1 and R2, respectively, while F9-F12 are machined at the center of corner R3. The size of these artificial grooves simulates early-stage micro-cracks at the blade root, a type of defect that is easily overlooked and dangerous in actual operation, ensuring the detection sensitivity of the inspection method for these minute defects. The groove positions are precisely matched to the stress concentration core area: F1-F4 and F5-F8 are located at the lower edges of corners R1 and R2, respectively, areas with high stress concentration coefficients; F9-F12 are located at the center of corner R3, an area with high load-bearing capacity. This makes the inspection more targeted and avoids wasted efficiency due to scanning ineffective areas.

[0026] During the CIVA simulation, same-side scanning, opposite-side scanning, and auxiliary wedge deflection incident surface scanning were simulated to verify the detectability of defects at angles R1, R2, and R3. When simulating same-side scanning, the structural signal of angle R1 and the defect signal of the artificial defect at angle R1 were acquired. When simulating opposite-side scanning, the structural signal of angle R2, the defect signal of the artificial defect at angle R2, and the defect signal of the artificial defect at angle R3 were acquired. When simulating auxiliary wedge deflection incident surface scanning, the probe was used to scan the opposite side, and the auxiliary wedge deflection incident surface was used to simulate the deflection of the incident surface, acquiring the structural signal of angle R2, the defect signal of the artificial defect at angle R2, and the defect signal of the artificial defect at angle R3. Understandably, by simulating three scanning modes in advance using CIVA, the detectability of defects can be verified without repeated physical experiments. The simulation process allows for direct observation of the ultrasonic beam propagation path and real-time detection of beam obstruction blind spots, such as beam obstruction of defects F6 and F7 without an auxiliary wedge. By adjusting the wedge angle and probe position in advance, optimization can be achieved, ensuring the effective detection of defects F6 and F7. The simulation results provide a quantitative basis for parameter setting: for example, determining the optimal wedge angle through simulation avoids the subjectivity of traditional parameter setting.

[0027] In step S2, the probe is a planar array shear wave angle probe with a frequency of 5.0 MHz, an array element configuration of 6×4, an element spacing of 1.0 mm × 1.5 mm, an element gap of 0.1 mm, and 24 crystals. An integrated wedge is used, with an acoustic wave incident angle of 36°. The parameters of the planar array shear wave angle probe achieve a balance between resolution and coverage. The 5 MHz high frequency ensures signal clarity for minute defects, and the 6×4 element configuration and 1.0 mm × 1.5 mm element spacing ensure that the acoustic beam covers the full width and depth of the double-step leaf root. The 36° incident angle of the integrated wedge adapts to the double-step tilt angle, allowing the ultrasonic beam to be perpendicularly incident on the R-angle region to be inspected, reducing acoustic energy loss. The auxiliary wedge, designed as an inclined plane wedge, meets the requirement of the shear wave angle probe moving on the same side of the step to scan the opposite side. The auxiliary wedge compensates for the tilt angle of the leaf root step by deflecting the acoustic beam incident surface laterally along the probe, thus enabling the scanning of defects on the opposite side.

[0028] In step S4, a continuous scan is performed on the outlet side A step along a direction parallel to the blade root length to acquire structural signals of angles R1 and R2, and defect signals of artificial defects F1 and F2. On the inlet side B step, a continuous scan is performed at two depth positions along a direction parallel to the blade root length. These two depth positions are the depth position closer to angle R1 and the depth position farther from angle R1, respectively. When scanning at the depth position close to angle R1 on the inlet side B step, the structural signal of angle R2 and defect signals of artificial defects F3 and F4 are acquired. When scanning at the depth position far from angle R1 on the inlet side B step, the structural signal of angle R1 and defect signals of artificial defects F3 and F4 are acquired. Specifically, when a continuous scan is performed on the outlet side A step along a direction parallel to the blade root length, the structural signals of angles R1 and R2, and the defect signals of artificial defects F1 and F2 are visible. When scanning along the parallel direction at step B on the intake side, the structural signals of artificial defects F3, F4, and angle R2 are clearly visible when the probe is close to angle R1. However, the signals are not visible because the probe is too close to angle R1 and is outside the gate range. When the probe is moved away from angle R1, the defect signals of angle R1 and artificial defects F3 and F4 are clearly visible, while the structural signal of angle R2 is weak and intermittent.

[0029] Understandably, a differentiated scanning strategy is designed based on the width difference between the outlet side (step A) and the inlet side (step B). The outlet side (step A) has sufficient width, allowing for parallel continuous scanning to improve efficiency. The inlet side (step B) is narrower, so scanning is conducted at two depths: near and far from the R1 corner. This avoids signal obstruction at the R1 corner due to step width limitations, ensuring the detection rate of F3 and F4 defects. Same-side scanning focuses on R1 corner defects, avoiding signal interference caused by simultaneous scanning of multiple areas. The R1 corner is the area closest to the blade and most susceptible to vibration; scanning it separately improves the identification of its defect signals.

[0030] In step S5, without auxiliary wedges, the structural signal of the R2 angle and the defect signals of artificial defects F8 and F12 are obtained by scanning the A step on the exhaust side; the structural signal of the R2 angle and the defect signals of artificial defects F5 and F9 are obtained by scanning the B step on the intake side. In the basic opposite-side scanning without auxiliary wedges, easily detectable defects such as F5, F8, F9, and F12 at the R2 and R3 angles are prioritized to form a basic detection layer. No additional auxiliary wedges are required. The basic scanning and the subsequent auxiliary wedge scanning complement each other. The basic scanning quickly covers most of the area first, and then the auxiliary wedge scanning completes the detection range, balancing detection efficiency and coverage integrity.

[0031] In step S6, an auxiliary wedge is added to scan the A step on the outlet side to obtain the structural signal of the R2 angle and the defect signals of artificial defects F7 and F11; and to scan the B step on the inlet side to obtain the structural signal of the R2 angle and the defect signals of artificial defects F6 and F10. The auxiliary wedge deflects the incident sound beam surface, precisely compensating for the angular deviation of the inclined step, solving the problem that defects F6, F7, F10, and F11 are located inside the inclined step and in the difficult-to-incident area of ​​the sound beam when there is no auxiliary wedge, thus completing the detection range and achieving full coverage of the R2 and R3 angles. The auxiliary wedge is structurally compatible with the main wedge, eliminating the need to adjust the core parameters of the probe, ensuring a continuous detection process, and improving detection efficiency.

[0032] In steps S4, S5, and S6, the ultrasonic testing equipment uses a combination of amplitude display, sector display, and planar display methods on the artificial defect test block. In the planar display method, the horizontal axis represents the probe scanning direction, and the vertical axis represents the sound beam propagation direction. This integration of amplitude, sector, and planar display methods forms a multi-dimensional point-line-plane detection system. Amplitude scanning accurately interprets signal properties, sector scanning locates the spatial position of the defect, and planar scanning confirms the continuity of the area. The three methods work together to avoid the limitations of a single scanning method. Furthermore, the coordinate definition of the planar display method visually presents the signal distribution along the sound beam propagation direction, facilitating quick identification of the defect's horizontal position by the testing personnel and providing precise location information for subsequent defect repair.

[0033] In the signal analysis and processing step S7, the positional differences between the structural signals and defect signals obtained from the fan-shaped display method, the differences in signal amplitude and waveform obtained from the amplitude display method, and the continuity of the signals obtained from the planar display method are compared to distinguish the R1 and R2 angle structural signals of the double-order T-shaped leaf root from the defect signals corresponding to each artificial defect, thus determining the existence and location of defects. Through multi-dimensional comparison of positional differences, amplitude waveform differences, and continuity differences, interference from misjudging structural reflection signals as defects is eliminated, effectively reducing the misjudgment rate.

[0034] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A method for in-situ ultrasonic testing of the root of a low-pressure rotor with a double-stage T-shaped blade, characterized in that, Including the following steps: S1. Prepare an artificial defect test block. The artificial defect test block has an outlet side A step and an inlet side B step corresponding to the double-stage T-shaped blade root. The artificial defect test block is provided with R1 angle, R2 angle and R3 angle distributed sequentially along the blade body to the blade root direction. S2. Design the probe and auxiliary wedge based on CIVA simulation, and determine the matching parameters between the probe and the auxiliary wedge; S3. Use the artificial defect test block prepared in step S1 to perform benchmark sensitivity calibration; S4. Use a probe to scan the R1 corner on the same side of the outlet side A step and the inlet side B step respectively; S5. Use a probe to scan for defects at the R2 and R3 angles on the opposite sides of the outlet side A step and the inlet side B step, respectively. S6. Based on step S5, add an auxiliary wedge to the probe to deflect the incident sound beam surface, and then scan the defects at the R2 and R3 angles again on the opposite side of the outlet side A step and the inlet side B step. S7. Analyze and process the ultrasonic signals obtained in steps S4, S5, and S6 to identify leaf root structure signals and defect signals, and complete the in-situ ultrasonic detection of the double-order T-shaped leaf root.

2. The in-situ ultrasonic testing method for the root of a low-pressure rotor with a double-stage T-shaped blade according to claim 1, characterized in that, In step S1, two artificial defects are provided at each end of the R1 corner of the outlet side A step and the inlet side B step of the artificial defect test block, which are respectively denoted as F1, F2, F3 and F4. F1 and F2 are located at the R1 corner of the outlet side A step, and F3 and F4 are located at the R1 corner of the inlet side B step. There are two artificial defects at each end of the R2 corner of the outlet side A step and the inlet side B step, respectively, which are labeled F5, F6, F7 and F8. F5 and F6 are located at the R2 corner of the outlet side A step, and F7 and F8 are located at the R2 corner of the inlet side B step. There are two artificial defects at each end of the R3 corner of the outlet side A step and the inlet side B step, respectively denoted as F9, F10, F11 and F12. F9 and F10 are located at the R3 corner of the outlet side A step, and F11 and F12 are located at the R3 corner of the inlet side B step.

3. The in-situ ultrasonic testing method for the root of a low-pressure rotor with a double-stage T-shaped blade according to claim 2, characterized in that, The artificial defects F1-F12 are all artificial grooves, and the size of the artificial grooves is 0.5mm×5mm; among them, F1-F4 and F5-F8 are machined at the lower edge of the R1 corner and the R2 corner respectively, and F9-F12 are machined at the center of the R3 corner.

4. The in-situ ultrasonic testing method for the root of a low-pressure rotor with a double-stage T-shaped blade according to claim 1, characterized in that, In step S2, during the CIVA simulation, same-side scanning, opposite-side scanning, and auxiliary wedge deflection incident surface scanning are simulated respectively to verify the detectability of defects at R1, R2, and R3 angles; When simulating same-side scanning, the structural signal of corner R1 and the defect signal of artificial defects at corner R1 are acquired; When simulating the opposite side scan, the structural signal of corner R2, the defect signal of the artificial defect at corner R2, and the defect signal of the artificial defect at corner R3 are acquired. When simulating the auxiliary wedge deflection incident surface scanning, the probe scans the opposite side, and by deflecting the incident sound beam surface, the auxiliary wedge deflects the incident surface to obtain the structural signal of the R2 angle, the defect signal of the artificial defect at the R2 angle, and the defect signal of the artificial defect at the R3 angle.

5. The in-situ ultrasonic testing method for the root of a low-pressure rotor with a double-stage T-shaped blade according to claim 1, characterized in that, In step S2, the probe is a planar array transverse wave angle probe with a frequency of 5.0MHz, an array element specification of 6×4, an element spacing of 1.0mm×1.5mm, an element gap of 0.1mm, and 24 crystals. It adopts an integrated wedge block with an acoustic wave incident angle of 36°.

6. The in-situ ultrasonic testing method for the root of a low-pressure rotor with a double-stage T-shaped blade according to claim 2, characterized in that, In step S4, a continuous scan is performed on step A on the outlet side along a direction parallel to the blade root length to obtain structural signals of angles R1 and R2, and defect signals of artificial defects F1 and F2. The intake side B step is continuously scanned at two depth positions along the direction parallel to the blade root length. The two depth positions are the depth position close to the R1 angle and the depth position far away from the R1 angle, respectively. When scanning at the depth position close to the R1 angle on the intake side B step, the structural signal of the R2 angle and the defect signals of artificial defects F3 and F4 are obtained. When scanning at the depth position far away from the R1 angle on the intake side B step, the structural signal of the R1 angle and the defect signals of artificial defects F3 and F4 are obtained.

7. The in-situ ultrasonic testing method for the root of a low-pressure rotor with a double-stage T-shaped blade according to claim 2, characterized in that, In step S5, without auxiliary wedges, the structural signal of angle R2 and the defect signals of artificial defects F8 and F12 are obtained by scanning step A on the outlet side; The structural signal of the R2 angle and the defect signals of artificial defects F5 and F9 were obtained by scanning the B step on the intake side.

8. The in-situ ultrasonic testing method for the root of a low-pressure rotor with a double-stage T-shaped blade according to claim 2, characterized in that, In step S6, an auxiliary wedge is added to scan the A step on the air outlet side to obtain the structural signal of the R2 angle and the defect signals of artificial defects F7 and F11; The structural signal of the R2 angle and the defect signals of artificial defects F6 and F10 were obtained by scanning the B step on the intake side.

9. The in-situ ultrasonic testing method for the root of a low-pressure rotor with a double-stage T-shaped blade according to claim 1, characterized in that, In steps S4, S5, and S6, the ultrasonic testing equipment uses a combination of amplitude display, sector display, and planar display on the artificial defect test block. In the planar display, the horizontal axis represents the probe scanning direction, and the vertical axis represents the sound beam propagation direction.

10. The in-situ ultrasonic testing method for the root of a low-pressure rotor with a double-stage T-shaped blade according to claim 9, characterized in that, In the signal analysis and processing of step S7, by comparing the positional differences between the structural signals and defect signals obtained by the fan-shaped display method, the differences in signal amplitude and waveform obtained by the amplitude display method, and the continuity of the signals obtained by the planar display method, the R1 and R2 angle structural signals of the double-order T-shaped leaf root are distinguished from the defect signals corresponding to each artificial defect, and the existence and location of defects are determined.

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