Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection and detection method

Abstract

The invention discloses a Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection and a detection method, and belongs to the technical field of ultrasonic flaw detection and stress detection. The problems that an existing ultrasonic method is low in detection efficiency and poor in precision, and corrosion can be caused to the surface of large precise rotary equipment are solved. Comprising a sealing cover, a shell and a printed circuit board which are sequentially and fixedly connected from top to bottom, a Fresnel annular coil is machined on the upper surface of the printed circuit board, a permanent magnet is arranged in the shell, and the permanent magnet and the Fresnel annular coil are arranged in an up-down opposite mode. Ultrasonic focusing is achieved through the Fresnel coil, the signal strength is improved, the detection area is reduced, the spatial resolution of stress detection is improved, meanwhile, the electromagnetic ultrasonic technology does not corrode the surface to be detected of the large precision rotary equipment, a coupling agent does not need to be smeared, and the detection efficiency is effectively improved.

Description

Technical Field

[0001] The invention relates to a Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection and a detection method, belonging to the technical field of ultrasonic flaw detection and stress detection. Background Art

[0002] Large precision rotating equipment such as aircraft engines or gas turbines are assembled from multi-stage rotors. Frequent starting, acceleration, deceleration and stopping of the engine cause high and low cycle fatigue and mechanical friction of the rotor under the action of cyclic stress such as alternating stress and torsional stress. In such a harsh working environment, the effect of every tiny defect in the rotor will be magnified, causing the entire engine rotor system to be unbalanced or even fail, causing aviation accidents. At the same time, the assembly quality between the rotors at each level has a very large impact on the performance of the aircraft engine or gas turbine. During the assembly process, if there is uneven contact stress at the rotor connection interface, the deformation of the aircraft engine or gas turbine at high speed will be uneven, and the unbalance of the rotor will vary greatly, which will eventually cause the aircraft engine or gas turbine to vibrate during operation. More than 90% of the failures of turbofan aircraft engines are caused by vibration, which is one of the reasons why my country's aircraft engines need to be overhauled after working for hundreds of hours. In addition, the rotor is subjected to thermal shock from high temperature, high pressure and highly corrosive gas up to 2000 degrees Celsius in the turbine chamber when rotating at a high speed of tens of thousands of revolutions per minute. Therefore, in view of the fault diversity and high failure rate of large precision rotating equipment such as aircraft engines or gas turbines, the research on high-precision, reliable non-destructive defect and stress detection technology has always been a hot issue in the aviation industry system. The current methods of defect and stress detection have the following problems:

[0003] 1. The existing defect detection method (water immersion focusing method) is greatly restricted by the environment, the water immersion structure is complex, the detection efficiency is low, and it will damage the surface of large precision rotating equipment. This method needs to be operated in water, which is greatly restricted by the environment, and water immersion focusing requires additional water tanks or pools for immersion, which increases the complexity and cost of the operation. In addition, water immersion may cause corrosion or contamination on the surface of large precision rotating equipment. Ultrasonic waves propagating in water will be affected by the absorption and scattering of water, which may cause signal attenuation and distortion, thereby reducing the accuracy and efficiency of detection.

[0004] 2. The existing stress measurement methods have low detection accuracy and spatial resolution and cannot reflect the actual contact situation. Currently, contact stress is usually measured by two methods. One method is to set a pressure-sensitive film or apply red lead powder on the contact interface of large-scale precision rotating equipment, and judge the contact situation by observing the changes in the pressure-sensitive film or red lead powder after assembly, and then calculate the contact stress. This method changes the contact state of the interface and has low measurement accuracy; the other is the ultrasonic method, which is divided into the water immersion focusing method and the non-water immersion non-focusing method. Both ultrasonic methods will damage the surface of the measured part. The difference is that the spatial resolution of stress measurement of the non-water immersion non-focusing method is low. Low spatial resolution makes it difficult to reflect the stress state of a smaller area.

[0005] 3. Coupling agent damages the surface. Traditional ultrasonic technology mostly uses contact transducers. In order to ensure high sensitivity and reliability, various ultrasonic coupling agents are usually required. Ultrasonic waves need a certain transit time when passing through the coupling agent, and will produce interfering harmonics, which will bring instability to the detection. In addition, the use of coupling agents will increase the workload and lead to low detection efficiency. What is more serious is that it will cause certain corrosion and damage to the surface of large precision rotating equipment. Therefore, in practical applications, traditional ultrasonic technology is subject to certain limitations.

[0006] 4. Currently, defect and stress detection of large rotary equipment usually uses two sets of equipment to detect defects and stress separately, which not only increases the initial investment, but also increases the long-term operating costs. Operators need to be familiar with the operating procedures of the two devices. During the inspection process, it may be necessary to clamp and adjust the tested parts many times, resulting in a longer inspection cycle. Since the two sets of equipment may come from different manufacturers and use different technical standards and data processing methods, the obtained inspection results may be inconsistent. This inconsistency may affect the accuracy of data analysis and decision-making. Summary of the invention

[0007] The present invention aims to solve the problems of low efficiency and poor accuracy of existing ultrasonic detection methods, and the corrosion caused to the surface of large-scale precision rotating equipment, and further provides a Fresnel coil electromagnetic ultrasonic transducer and a detection method for defect and stress detection.

[0008] The technical solution adopted by the present invention to solve the above technical problems is:

[0009] A Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection comprises a cover, a shell and a printed circuit board which are fixedly connected in sequence from top to bottom, wherein a Fresnel annular coil is processed on the upper surface of the printed circuit board, a permanent magnet is arranged inside the shell, and the permanent magnet and the Fresnel annular coil are arranged vertically opposite to each other.

[0010] Furthermore, the Fresnel toroidal coil comprises a plurality of concentrically arranged circular toroidal coils.

[0011] Furthermore, the radius r of each ring in the Fresnel toroidal coil is n Obtained by the following formula:

[0012]

[0013] Among them, F0 is the focal length, λ is the ultrasonic wavelength, n is the number of coil rings, and n is an odd number.

[0014] Furthermore, the shell comprises an upper shell and a lower shell arranged in a convex shape, a through hole is vertically opened inside the shell, the permanent magnet is installed in the through hole, the cover is fixedly connected to the upper shell, and the printed circuit board is fixedly connected to the lower shell.

[0015] Furthermore, the permanent magnet is arranged at the same height as the shell.

[0016] Furthermore, the cover and the shell are fixedly connected by a plurality of first screws.

[0017] Furthermore, the housing and the printed circuit board are fixedly connected by a plurality of second screws.

[0018] A detection method for the above-mentioned Fresnel coil electromagnetic ultrasonic transducer comprises the following steps:

[0019] Step 1: Position the Fresnel coil electromagnetic ultrasonic transducer at the position to be detected L(i) of the large precision rotary equipment;

[0020] Step 2: Current is passed through the Fresnel toroidal coil to generate ultrasonic waves inside the large precision rotating equipment and focus them on the focal area;

[0021] Step 3: The Fresnel coil electromagnetic ultrasonic transducer collects the ultrasonic signal S(i) reflected inside the large precision rotating equipment;

[0022] Step 4: Analyze and extract the waveform index W(i) of the ultrasonic signal S(i), and determine whether there is a defect at the current detection position through the waveform index W(i). If there is a defect, the specific information of the defect is obtained based on the corresponding relationship between the waveform index W(i) and the defect feature D(i);

[0023]

[0024] Wherein, N is the number of sampling points of the ultrasonic signal S(i), and j takes values ​​of 1, 2, ..., N;

[0025] Step 5: Analyze and extract the propagation time difference Δt(i) of the ultrasonic signal S(i), and obtain the specific stress information at the detection position L(i) based on the corresponding relationship between the propagation time difference Δt(i) and the stress σ(i);

[0026] Step 6: Repeat steps 1 to 5 to detect the defects and stress information of all positions that need to be detected on the large-scale precision rotary equipment, and draw a defect distribution map and a stress field cloud map.

[0027] Furthermore, in step 4, the corresponding relationship between the waveform index W(i) and the defect feature D(i) is:

[0028] D(i)=F(W(i))

[0029] Where F(·) represents the function between the waveform index W(i) and the defect feature D(i), which is obtained through calibration experiments.

[0030] Furthermore, in step 5, the corresponding relationship between the propagation time difference Δt(i) and the stress σ(i) is obtained through calibration experiments:

[0031] σ(i)=K·Δt(i)

[0032] Where K is the stress coefficient.

[0033] Compared with the prior art, the present invention has the following effects:

[0034] The Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection of the present invention has a Fresnel ring coil processed on the upper surface of a printed circuit board, that is, an excitation coil in the form of a Fresnel ring structure and a coil manufacturing technology for a printed circuit are adopted. The excitation coil in the form of a Fresnel ring structure is an improved version of a racetrack-shaped coil, and has both the characteristics of a racetrack-shaped coil that can excite and receive body waves and the characteristics of a Fresnel ring that can focus ultrasonic waves, thereby focusing the sound waves on a focal area, increasing signal strength and reducing the detection area, thereby improving stress detection accuracy and spatial resolution.

[0035] The Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection of the present invention adopts an integrated installation method, which installs the permanent magnet and the printed circuit board processed with the Fresnel ring coil together to form a whole. Traditional electromagnetic ultrasonic transducers mostly adopt a separate type, which is complicated to operate in actual applications and is easy to be accidentally touched, resulting in a change in the relative position of the permanent magnet and the excitation coil, thereby causing measurement errors. The printed circuit coil manufacturing technology adopted by the present invention has the best comprehensive characteristics, can reduce the coil resistance, is easy to manufacture, and has higher dimensional accuracy and is easy to use, making the electromagnetic ultrasonic transducer structure more compact, so that it can adapt to more complex measurement environments.

[0036] The Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection of the present invention adopts electromagnetic ultrasonic technology that does not require coupling agent. The Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection of the present invention can directly excite and generate ultrasonic waves on the surface to be tested of large-scale precision rotating equipment, and no coupling agent is required during measurement, thereby avoiding the influence of the coupling agent on the detection results and improving the accuracy of defect and stress detection. At the same time, the electromagnetic ultrasonic technology will not cause corrosion to the surface to be tested of large-scale precision rotating equipment, and no coupling agent needs to be applied, which effectively improves the detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is an exploded schematic diagram of the Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection of the present invention;

[0038] Figure 2 It is a schematic diagram of the three-dimensional structure of the Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection of the present invention;

[0039] Figure 3 The figure is a schematic diagram of the application position of the Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection of the present invention applied to large-scale precision rotating equipment.

[0040] In the figure:

[0041] 1. Cover; 2. Shell; 21. Upper shell; 22. Lower shell; 23. Through hole; 3. Printed circuit board; 4. Fresnel ring coil; 5. Permanent magnet; 6. First screw; 7. Second screw; 8. Fresnel coil electromagnetic ultrasonic transducer; 9. Large precision rotating equipment. DETAILED DESCRIPTION

[0042] Specific implementation method 1: Combination Figure 1 to Figure 3 This embodiment is explained, and the technical scheme in the embodiment of the present invention is clearly and completely described. Obviously, the described embodiment is only a part of the embodiment of the present invention, rather than all the embodiments. Based on the embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0043] It should be noted that the descriptions of the present invention regarding directions such as "front", "back", "left", "right", "inside", "outside", "left side", "right side", "upper", "lower", "top", "bottom", etc. are all defined based on the relationship between the orientations or positions shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the structure must be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention. In the description of the present invention, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0044] In the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] A Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection comprises a cover 1, a shell 2 and a printed circuit board 3 which are fixedly connected in sequence from top to bottom, wherein a Fresnel ring coil 4 is processed on the upper surface of the printed circuit board 3, and a permanent magnet 5 is arranged inside the shell 2, and the permanent magnet 5 and the Fresnel ring coil 4 are arranged vertically opposite to each other.

[0046] The Fresnel ring coil 4 refers to the structural form of the coil, which is not a separate structure, that is, the Fresnel ring coil 4 and the printed circuit board 3 are integrated and are manufactured using the coil manufacturing technology of the printed circuit.

[0047] The permanent magnet 5 is encapsulated in the housing 2 through the cover 1 and the printed circuit board 3 .

[0048] The permanent magnet 5 and the Fresnel ring coil 4 are arranged vertically opposite to each other, so that the center of the permanent magnet 5 coincides with the center of the Fresnel ring coil 4. The permanent magnet 5 generates a bias magnetic field perpendicular to the surface to be measured of the large precision rotating equipment.

[0049] When performing defect and stress detection on the surface of large precision rotating equipment or other devices, the Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection of the present invention is placed on the surface to be tested. The Fresnel annular coil 4 is excited by a pulse or alternating current source, generating an alternating electromagnetic field on the surface to be tested of the large precision rotating equipment, inducing eddy currents according to the Biotsager's law, and the eddy currents are acted upon by the Lorentz force in the bias magnetic field generated by the permanent magnet 5, causing high-frequency vibration of the particles on the surface to be tested of the large precision rotating equipment, thereby generating ultrasonic waves.

[0050] The Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection of the present invention adopts electromagnetic ultrasonic technology that does not require coupling agent. The Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection of the present invention can directly excite and generate ultrasonic waves on the surface to be tested of large-scale precision rotating equipment, and no coupling agent is required during measurement, thereby avoiding the influence of the coupling agent on the detection results and improving the accuracy of defect and stress detection. At the same time, the electromagnetic ultrasonic technology will not cause corrosion to the surface to be tested of large-scale precision rotating equipment, and the detection efficiency is effectively improved without the need to apply coupling agent.

[0051] The Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection of the present invention has a Fresnel ring coil 4 processed on the upper surface of a printed circuit board 3, that is, an excitation coil in the form of a Fresnel ring structure and a coil manufacturing technology for a printed circuit are adopted. The excitation coil in the form of a Fresnel ring structure is an improved version of a racetrack-shaped coil, and has both the characteristics of a racetrack-shaped coil that can excite and receive body waves and the characteristics of a Fresnel ring that can focus ultrasonic waves, thereby focusing the sound waves on a focal area, increasing signal strength and reducing the detection area, thereby improving stress detection accuracy and spatial resolution.

[0052] The Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection of the present invention adopts an integrated installation method, and the permanent magnet 5 and the printed circuit board 3 processed with the Fresnel ring coil 4 are installed together to form a whole. Traditional electromagnetic ultrasonic transducers mostly adopt a separate type, which is complicated to operate in actual applications and is easy to be accidentally touched, resulting in a change in the relative position of the permanent magnet and the excitation coil, thereby causing measurement errors. The printed circuit coil manufacturing technology adopted by the present invention has the best comprehensive characteristics, can reduce the coil resistance, is easy to manufacture, and has higher dimensional accuracy and is easy to use, making the electromagnetic ultrasonic transducer structure more compact, so that it can adapt to more complex measurement environments.

[0053] Ultrasonic defect detection is a non-destructive testing method that uses ultrasonic waves to detect internal defects in materials. The principle is that when ultrasonic waves propagate in materials, they interact with defects, interfaces or other inhomogeneities inside the materials, causing reflection, scattering, refraction and other phenomena. The defects of materials are detected and evaluated by analyzing the waveform index W of the echo signal to determine the type, location, shape and size of the defects.

[0054] Ultrasonic contact stress measurement is a method that uses ultrasonic technology to measure the internal stress distribution of materials. Its principle is based on the fact that when ultrasonic waves propagate in materials, they are affected by stress, which causes the propagation time of ultrasonic waves to change. The distribution of internal stress in the material is inferred by measuring the ultrasonic propagation time difference Δt (the difference between the propagation time of ultrasonic waves when stress exists and the propagation time of ultrasonic echoes when there is no stress) and the stress coefficient K (the stress coefficient K is determined by calibration tests).

[0055] The Fresnel ring coil 4 comprises a plurality of concentrically arranged circular ring coils. That is, the Fresnel ring coil 4 is composed of a series of concentric circular rings and conforms to the Fresnel ring array distribution.

[0056] The radius r of each ring in the Fresnel ring coil 4 n Obtained by the following formula:

[0057]

[0058] Where F0 is the focal length, λ is the ultrasonic wavelength, n is the number of coil rings, and n is an odd number. In this design, the width of the ring is Δr n The area below the Fresnel annular coil 4 generates ultrasonic waves, while the area below the coil gap does not generate ultrasonic waves. The distance between the edges of two adjacent rings of the coil and the focus differs by half an ultrasonic wavelength (π phases), so that the ultrasonic wave is focused at the focus (half-wavelength principle).

[0059] The housing 2 includes an upper housing 21 and a lower housing 22 arranged in a convex shape. A through hole 23 is vertically provided inside the housing 2. The permanent magnet 5 is installed in the through hole 23. The cover 1 is fixedly connected to the upper housing 21, and the printed circuit board 3 is fixedly connected to the lower housing 22. With such a design, a space for accommodating the permanent magnet 5 is provided by providing the through hole 23. The upper housing 21 and the lower housing 22 arranged in a convex shape facilitate the reasonable arrangement of the connection structure between the cover 1 and the housing 2 and between the housing 2 and the printed circuit board 3. The step surface formed between the upper housing 21 and the lower housing 22 facilitates the fixed connection between the housing 2 and the printed circuit board 3. At the same time, the convex housing 2 can also reduce the overall weight of the transducer.

[0060] The permanent magnet 5 is arranged at the same height as the housing 2. With such a design, the height direction of the permanent magnet 5 can be limited by the cover 1 and the printed circuit board 3, so that the permanent magnet 5 always maintains direct contact with the printed circuit board 3 during the measurement process, thereby ensuring the accuracy of the measurement structure.

[0061] The cover 1 and the housing 2 are fixedly connected by a plurality of first screws 6. In such a design, the first screws 6 are short screws, and the number of the first screws 6 is preferably four and evenly distributed along the circumference of the cover 1. The first screws 6 pass through the cover 1 and are threadedly connected to the upper part of the housing 2.

[0062] The housing 2 and the printed circuit board 3 are fixedly connected by a plurality of second screws 7. In this design, the second screws 7 are long screws, and the number of the second screws 7 is preferably four and evenly distributed along the circumference of the housing 2. The second screws 7 pass through the housing 2 and are threadedly connected to the printed circuit board 3, or the second screws 7 pass through the housing 2 and the printed circuit board 3 in sequence and are fixed by nuts.

[0063] A detection method for the above-mentioned Fresnel coil electromagnetic ultrasonic transducer comprises the following steps:

[0064] Step 1: Position the Fresnel coil electromagnetic ultrasonic transducer 8 at the position L(i) to be detected of the large precision rotary equipment 9;

[0065] Step 2: Current is passed through the Fresnel ring coil 4 to generate ultrasonic waves inside the large precision rotary equipment 9 and focus them on a focal area; the focal area is the area where ultrasonic energy is concentrated, that is, the measurement area.

[0066] Step 3: The Fresnel coil electromagnetic ultrasonic transducer 8 collects the ultrasonic signal S(i) reflected inside the large precision rotating equipment 9;

[0067] Step 4: Analyze and extract the waveform index W(i) of the ultrasonic signal S(i), and determine whether there is a defect at the current detection position through the waveform index W(i). If there is a defect, the specific information of the defect is obtained based on the corresponding relationship between the waveform index W(i) and the defect feature D(i);

[0068]

[0069] Wherein, N is the number of sampling points of the ultrasonic signal S(i), and j takes the value of 1, 2, ..., N; that is, starting from the first sampling point, until the N sampling points in the ultrasonic signal are calculated.

[0070] Step 5: Analyze and extract the propagation time difference Δt(i) of the ultrasonic signal S(i), and obtain the specific stress information at the detection position L(i) based on the corresponding relationship between the propagation time difference Δt(i) and the stress σ(i);

[0071] Step 6: Repeat steps 1 to 5 to detect the defects and stress information of all positions that need to be detected on the large-scale precision rotating equipment, and draw a defect distribution map and a stress field cloud map.

[0072] The detection method of the present invention can simultaneously realize defect and stress detection of large-scale rotating equipment, effectively reduce the detection and equipment operation costs, improve the detection efficiency, and overcome the problem of poor data consistency and compatibility between multiple sets of equipment.

[0073] In step 4, the corresponding relationship between the waveform index W(i) and the defect feature D(i) is:

[0074] D(i)=F(W(i))

[0075] Where F(·) represents the function between the waveform index W(i) and the defect feature D(i), which is obtained through calibration experiments.

[0076] In step 5, the corresponding relationship between the propagation time difference Δt(i) and the stress σ(i) is obtained through calibration experiments:

[0077] σ(i)=K·Δt(i)

[0078] Where K is the stress coefficient.

[0079] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection, characterized in that: The invention comprises a cover (1), a shell (2) and a printed circuit board (3) which are fixedly connected in sequence from top to bottom, wherein a Fresnel annular coil (4) is processed on the upper surface of the printed circuit board (3), a permanent magnet (5) is arranged inside the shell (2), and the permanent magnet (5) and the Fresnel annular coil (4) are arranged vertically opposite to each other.

2. The Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection according to claim 1, characterized in that: The Fresnel annular coil (4) comprises a plurality of concentrically arranged circular annular coils.

3. The Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection according to claim 2, characterized in that: The radius r of each ring in the Fresnel ring coil (4) n Obtained by the following formula: Among them, F0 is the focal length, λ is the ultrasonic wavelength, n is the number of coil rings, and n is an odd number.

4. The Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection according to claim 1, characterized in that: The housing (2) comprises an upper housing (21) and a lower housing (22) arranged in a convex shape, a through hole (23) is vertically opened inside the housing (2), a permanent magnet (5) is inserted into the through hole (23), the cover (1) is fixedly connected to the upper housing (21), and the printed circuit board (3) is fixedly connected to the lower housing (22).

5. The Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection according to claim 1, characterized in that: The permanent magnet (5) is arranged at the same height as the housing (2).

6. The Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection according to claim 1, characterized in that: The cover (1) and the housing (2) are fixedly connected via a plurality of first screws (6).

7. The Fresnel coil electromagnetic ultrasonic transducer for defect and stress detection according to claim 1, characterized in that: The housing (2) and the printed circuit board (3) are fixedly connected via a plurality of second screws (7).

8. A method for detecting the Fresnel coil electromagnetic ultrasonic transducer according to any one of claims 1 to 7, characterized in that: The steps include: Step 1: Position the Fresnel coil electromagnetic ultrasonic transducer (8) at the position L (i) to be detected of the large precision rotary equipment (9); Step 2: Current is passed through the Fresnel ring coil (4), generating ultrasonic waves inside the large precision rotating equipment (9) and focusing them on a focal area; Step 3: The Fresnel coil electromagnetic ultrasonic transducer (8) collects the ultrasonic signal S (i) reflected from the large precision rotating equipment (9); Step 4: Analyze and extract the waveform index W(i) of the ultrasonic signal S(i), and determine whether there is a defect at the current detection position through the waveform index W(i). If there is a defect, the specific information of the defect is obtained based on the corresponding relationship between the waveform index W(i) and the defect feature D(i); Wherein, N is the number of sampling points of the ultrasonic signal S(i), and j takes values ​​of 1, 2, ..., N; Step 5: Analyze and extract the propagation time difference Δt(i) of the ultrasonic signal S(i), and obtain the specific stress information at the detection position L(i) based on the corresponding relationship between the propagation time difference Δt(i) and the stress σ(i); Step 6: Repeat steps 1 to 5 to detect the defects and stress information of all positions that need to be detected on the large-scale precision rotary equipment, and draw a defect distribution map and a stress field cloud map.

9. The detection method according to claim 8, characterized in that: In step 4, the corresponding relationship between the waveform index W(i) and the defect feature D(i) is: D(i)=F(W(i)) Where F(·) represents the function between the waveform index W(i) and the defect feature D(i), which is obtained through calibration experiments.

10. The detection method according to claim 8, characterized in that: In step 5, the corresponding relationship between the propagation time difference Δt(i) and the stress σ(i) is obtained through calibration experiments: σ(i)=K·Δt(i) Where K is the stress coefficient.

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