In-situ eddy current detection method for surface defects of small-gap rotating part

Abstract

The invention relates to the technical field of eddy current detection, and discloses a small-gap rotating part surface defect in-situ eddy current detection method which is used for aero-engine blade detection. According to the eddy current detection sensor, the micro coil is embedded on the ultrathin metal sheet with the gradually-changed thickness, namely, the ultrathin metal sheet with the gradually-changed thickness is used as a supporting framework of the micro coil, so that the fine structural design of the eddy current detection sensor is realized; the device has certain rigidity and can extend into a narrow gap between a blade tip and the surface of the inner wall of a casing to implement in-situ detection, and the engineering technical problem that a conventional eddy current detection means cannot be effectively implemented is solved. The method has the advantages of being reliable in detection result, free of missing detection and high in detection efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of eddy current detection, and in particular to an in-situ eddy current detection method for surface defects of a small-gap rotating component. Background Art

[0002] In the industrial field, especially in the aviation, automotive and energy industries, there are many complex devices. The rapid detection of some rotating parts in these devices located in narrow spaces faces significant challenges. These parts will be subjected to extreme conditions such as high temperature, high pressure and high speed during operation, and are prone to defects such as fatigue cracks, wear and corrosion, which seriously threaten the safe operation of the equipment. Therefore, how to perform effective in-situ non-destructive testing on these narrow parts is particularly important. Taking the tip of the rotating blade in the engine casing as an example, the gap between the tip and the inner wall of the casing is usually very small (less than 1 cm), and the number of blades is large, with dozens to hundreds of blades on each wheel. If detected one by one, it is not only time-consuming and laborious, but there is currently no eddy current sensor and corresponding detection method that can meet such complex detection needs. Based on this, the present invention is improved on the basis of the prior art to solve this problem. Summary of the invention

[0003] In order to solve the above problems, the present invention provides an in-situ eddy current detection method for surface defects of small-gap rotating parts, which is implemented as follows:

[0004] An in-situ eddy current detection method for surface defects of small-gap rotating parts, the eddy current detection method is used in the field of aero-engine blade detection, and the tip of the blade to be tested is rotated and passed through an eddy current detection device for eddy current detection;

[0005] The eddy current detection device includes a detection unit, an auxiliary device and a signal analysis unit;

[0006] The detection unit includes an ultra-thin metal sheet and a plurality of micro coils;

[0007] The thickness of the ultra-thin metal sheet is set to a gradual value of the gap between the blade tip and the inner wall surface of the casing, and a plurality of grooves are processed on its surface;

[0008] The grooves are arranged in multiple rows and are arranged in a herringbone shape, and an insulating groove is provided between adjacent grooves;

[0009] The plurality of micro coils are embedded in the groove;

[0010] The auxiliary device comprises a handle, a probe rod and a movable joint connected to the ultra-thin metal sheet, which are connected in sequence and are used to deliver the detection unit into the engine casing through the detection hole and fix it;

[0011] The signal analysis unit analyzes and processes the eddy current signal acquired by the detection unit, wherein the eddy current signal includes a noise interference signal and an effective detection signal, wherein the noise interference signal is an eddy current signal generated on the ultra-thin metal sheet when the micro-coil is excited, and the effective detection signal is an eddy current signal generated on the tip of the blade being detected when the micro-coil is excited;

[0012] The steps of eddy current testing are:

[0013] S1. Pre-extracting noise interference signals: Based on the characteristic that the eddy current signal output generated by the micro-coil on the ultra-thin metal sheet when each blade tip rotates and passes through the detection unit is uniform, before the actual detection, the detection unit is placed in the air with the same detection frequency as in the actual detection and the eddy current signal generated on the ultra-thin metal sheet is obtained and marked as a noise interference signal;

[0014] S2. Installation and fixation of the detection unit: the detection unit and the probe rod are arranged on the same plane by the auxiliary device, and the detection unit is extended into the inner casing through the detection hole, and the movable joint is arranged to rotate so that the detection unit and the probe rod form a certain angle and can be inserted into the gap between the casing and the blade tip;

[0015] S3. Implementation of detection: After the detection unit is fixedly installed in step S2, the engine turbine disk is rotated automatically or manually so that the blades of the entire machine rotate at a uniform speed in turn through the detection unit and obtain eddy current signals. In this process, the signal analysis unit uses a signal processing algorithm to remove the noise interference signal marked in step S1 from the eddy current signal obtained when each blade passes through the detection unit in real time and finally outputs the effective detection signal.

[0016] Furthermore, the ultra-thin metal sheet is an austenitic stainless steel sheet; the micro coil is configured as a planar spiral coil, and the micro coil is fixedly installed in the groove by glue or spot welding.

[0017] Furthermore, the bottom surface of the groove is in the form of a grid and is provided with a plurality of strip-shaped open grooves, and the open grooves block the influence of the induced magnetic field generated by the planar spiral coil on the ultra-thin metal sheet.

[0018] Compared with the existing ones, this application can obtain the following technical effects:

[0019] The present invention adopts the method of embedding a micro coil on an ultra-thin metal sheet with a gradual thickness, that is, by using an ultra-thin metal sheet with a gradual thickness as a supporting frame of the micro coil, a refined structural design of an eddy current detection sensor is realized, so that it has a certain rigidity and can extend into the narrow gap between the blade tip and the inner wall surface of the casing to implement in-situ detection. At the same time, based on the characteristic that the eddy current signal output generated by the micro coil on the ultra-thin metal sheet when each blade tip rotates through the detection sensor is uniform, a method of pre-marking the background noise interference signal generated by the ultra-thin metal sheet as the coil frame and removing it is adopted to obtain a real and effective eddy current detection signal, solving the engineering and technical problems that cannot be effectively implemented by existing conventional eddy current detection means. The detection method of the present invention has the advantages of reliable detection results, no missed detection, and high detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the examples of the present invention or the technical solutions in the prior art or the drawings required for use in the description of the prior art, a brief introduction is given. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 Schematic diagram of the detection working condition of this embodiment.

[0022] Figure 2-3 Schematic diagram of the eddy current testing equipment of this embodiment.

[0023] Figure 4 Schematic diagram of the detection unit of this embodiment.

[0024] 10- eddy current testing equipment, 11- testing unit, 111- ultra-thin metal sheet, 111a- groove, 111b- insulating groove, 111c- opening groove, 112- micro coil, 12- auxiliary device, 121- handle, 122- probe rod;

[0025] 20-outer casing, 21-inner casing, 22-detection hole;

[0026] 30-leaf blade, 31-leaf tip. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but only represents selected embodiments of the present invention.

[0028] The present invention can be applied to aircraft engine blade detection, gas turbine blade detection, steam turbine blade detection, etc. In this embodiment, the tip of an aircraft engine blade is taken as an example.

[0029] This embodiment discloses an in-situ eddy current detection method for surface defects of small-gap rotating parts, which is used in the field of aircraft engine blade detection. In order to meet the detection requirements of eddy current detection of crack defects on the blade tips of moving blades in the engine casing, the eddy current sensor needs to pass through the detection holes 22 on the outer casing 20 and the inner casing 21 in sequence and turn to extend into the narrow gap between the inner wall surface of the casing and the blade tip in order to implement in-situ detection. However, the gap between the inner wall of the casing and the blade tip is extremely small (usually less than 1 cm), and the size of the gap gradually changes unevenly. In addition, there are dozens or even hundreds of blades per week. If they are detected one by one, the efficiency is extremely low, and it is very easy to miss the detection.

[0030] The detection method disclosed in the present invention is to rotate the tip of the blade to be detected and pass it through the eddy current detection equipment to perform eddy current detection;

[0031] The eddy current detection device 10 includes a detection unit 11, an auxiliary device 12 and a signal analysis unit;

[0032] The detection unit 11 includes an ultra-thin metal sheet 111 and a plurality of micro coils 112;

[0033] Reference Figure 4 , attached Figure 4 2 is a schematic diagram of the structure of an ultra-thin metal sheet, wherein a plurality of grooves 111a are processed on the surface of the ultra-thin metal sheet 111, wherein the grooves 111a are arranged in multiple rows and the plurality of grooves 111a are arranged in an array, and an insulating groove 111b is provided between adjacent grooves 111a; the insulating grooves 111b serve to electrically isolate the micro coils 112 in adjacent grooves. In the present embodiment, the insulating grooves 111b are of a straight-line structure and are vertically connected between two adjacent grooves. In other embodiments, electroplating may be used to plate a linear insulating layer between adjacent grooves.

[0034] The plurality of micro coils 112 are respectively embedded in the grooves 111 a to prevent the micro coils 112 from being worn and to increase the service life of the detection element.

[0035] In other embodiments, the groove shape can be set to a diamond structure, and a plurality of grooves are arranged in a straight line, and the micro coil is set to a diamond planar spiral structure that completely matches the groove shape.

[0036] The auxiliary device 12 includes a handle 121, a probe rod 122 and an active joint connected to the ultra-thin metal sheet 111, which are connected in sequence, and is used to deliver the detection unit 11 to the engine casing through the detection hole 22 and fix it. In this embodiment, a hollow probe rod is used, and a traction wire and a tiny pulley built into the probe rod are set for traction deformation. In other embodiments, other active joints suitable for fine structures can be used.

[0037] The signal analysis unit analyzes and processes the eddy current signal obtained by the detection unit, wherein the eddy current signal includes a noise interference signal and an effective detection signal, wherein the noise interference signal is an eddy current signal generated on the ultra-thin metal sheet when the micro-coil is excited, and the effective detection signal is an eddy current signal generated on the tip of the blade being detected when the micro-coil 112 is excited;

[0038] In this embodiment, the gap between the tip 31 of the blade 30 and the inner wall of the engine casing varies from about 0.6mm to 1mm, the diameter of the detection hole on the casing is 8mm, and the width of the blade to be tested is 15mm. The size design and parameter setting of the eddy current detection equipment are carried out according to this detection example. Among them, the thickness of the ultra-thin metal sheet is set to the gradual value of the gap between the tip and the inner wall surface of the casing. It is extended into the gap between the casing and the tip of the blade to achieve a complete fit between the ultra-thin metal sheet and the tip of the blade, overcome the lift-off problem, and ensure the sensitivity of the detection.

[0039] The steps of eddy current testing are:

[0040] S1. Pre-extracting noise interference signals: Based on the characteristic that the eddy current signal output generated by the micro-coil on the ultra-thin metal sheet when each blade tip rotates and passes through the detection unit is uniform, before the detection unit is installed and fixed, the detection unit is placed in the air with the same detection frequency as the actual detection and the eddy current signal generated on the ultra-thin metal sheet is obtained and marked as a noise interference signal;

[0041] S2. Installation and fixation of the detection unit: the detection unit and the probe rod are arranged on the same plane by the auxiliary device, and the detection unit is extended into the inner casing through the detection hole, and then the movable joint is arranged to rotate so that the detection unit and the probe rod form a certain angle and can be inserted into the gap between the casing and the blade tip;

[0042] S3. Implementation of detection: After the detection unit is fixedly installed in step S2, the engine turbine disk is rotated automatically or manually so that the blades of the entire machine rotate at a uniform speed and pass through the detection unit in sequence, and eddy current signals are obtained. In this process, the signal analysis unit uses a signal processing algorithm to remove the noise interference signal marked in step S1 from the eddy current signal obtained when each blade passes through the detection unit in real time, and finally outputs the effective detection signal.

[0043] In this embodiment, the detection parameters used to obtain the ultra-thin metal sheet interference signal are the same as the detection parameters used to detect the blade tip. In the denoising data processing, the measured eddy current signal image and the stainless steel sheet interference signal image are aligned and matched in time and amplitude, and then a subtraction operation is performed.

[0044] Alternatively, a filtering processing method is used, using a digital filter, and the filter parameters are set according to the frequency characteristics of the obtained stainless steel sheet interference signal to filter out the part of the measured eddy current detection signal containing the interference signal frequency component.

[0045] Alternatively, methods such as using wavelet transform and establishing a mathematical model of the measured signal and the interference signal are adopted, which will not be elaborated in this embodiment.

[0046] In the design of eddy current detection sensors, ultra-thin metal sheets are used as the supporting structure of the coil. The metal sheets have good toughness and ductility and are easy to process and deform. At the same time, combined with the detection characteristics under specific working conditions, interference signals are eliminated by using interference signal extraction methods, breaking through the technical ideas of conventional eddy current detection sensor structure design and solving the problems of actual engineering applications.

[0047] Furthermore, in this embodiment, the ultra-thin metal sheet is an austenitic stainless steel sheet; the micro coil is a planar spiral coil for blade defect detection, and the micro coil is fixedly installed in the groove by glue or spot welding. The austenitic stainless steel sheet has weak magnetic conductivity and electrical conductivity, but good performance, which meets the design requirements of the fine sensor structure and can reduce the background noise generated by the material.

[0048] Furthermore, the bottom surface of the groove is provided with a plurality of strip-shaped opening grooves 111c in a grid-like manner, and the opening grooves 111c block the induced magnetic field generated by the planar spiral coil on the ultra-thin metal sheet. The design of the opening grooves 111c can change the magnetic field distribution characteristics of the coil, thereby having a certain shielding or isolation effect on the magnetic field generated by the ultra-thin metal sheet.

[0049] Furthermore, the surface of the planar spiral coil is sprayed with an ultra-thin wear-resistant layer to increase the service life of the coil.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An in-situ eddy current detection method for surface defects of small-gap rotating parts, characterized in that: The eddy current detection method is used in the field of aero-engine blade detection, where the tip of the blade to be detected is rotated and passed through an eddy current detection device for eddy current detection; The eddy current detection device includes a detection unit, an auxiliary device and a signal analysis unit; The detection unit includes an ultra-thin metal sheet and a plurality of micro coils; The thickness of the ultra-thin metal sheet is set to a gradual value of the gap between the blade tip and the inner wall surface of the casing, and a plurality of grooves are processed on its surface; The grooves are arranged in multiple rows and are arranged in a herringbone shape, and an insulating groove is provided between adjacent grooves; The plurality of micro coils are embedded in the groove; The auxiliary device comprises a handle, a probe rod and a movable joint connected to the ultra-thin metal sheet, which are connected in sequence and are used to deliver the detection unit into the engine casing through the detection hole and fix it; The signal analysis unit analyzes and processes the eddy current signal acquired by the detection unit, wherein the eddy current signal includes a noise interference signal and an effective detection signal, wherein the noise interference signal is an eddy current signal generated on the ultra-thin metal sheet when the micro-coil is excited, and the effective detection signal is an eddy current signal generated on the tip of the blade being detected when the micro-coil is excited; The steps of eddy current testing are: S1. Pre-extracting noise interference signals: Based on the characteristic that the eddy current signal output generated by the micro-coil on the ultra-thin metal sheet when each blade tip rotates and passes through the detection unit is uniform, before the actual detection, the detection unit is placed in the air with the same detection frequency as the actual detection and the eddy current signal generated on the ultra-thin metal sheet is obtained and marked as a noise interference signal; S2. Installation and fixation of the detection unit: the detection unit and the probe rod are arranged on the same plane by the auxiliary device, and the detection unit is extended into the inner casing through the detection hole, and the movable joint is arranged to rotate so that the detection unit and the probe rod form a certain angle and can be inserted into the gap between the casing and the blade tip; S3. Implementation of detection: After the detection unit is fixedly installed in step S2, the engine turbine disk is rotated automatically or manually so that the blades of the entire machine rotate at a uniform speed in turn through the detection unit and obtain eddy current signals. In this process, the signal analysis unit uses a signal processing algorithm to remove the noise interference signal marked in step S1 from the eddy current signal obtained when each blade passes through the detection unit in real time and finally outputs the effective detection signal.

2. The in-situ eddy current detection method for surface defects of small clearance rotating parts according to claim 1 is characterized in that: The ultra-thin metal sheet is an austenitic stainless steel sheet; the micro coil is configured as a planar spiral coil, and the micro coil is fixedly installed in the groove by glue or spot welding.

3. The in-situ eddy current detection method for surface defects of small clearance rotating parts according to claim 2 is characterized in that: The bottom surface of the groove is provided with a plurality of strip-shaped opening grooves in a grid-like manner.

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