In-situ detection method for complex structure of engine

Abstract

The present application relates to the technical field of nondestructive testing of aerospace engines, in particular to an in-situ detection method for complex structures of engines, which is used for detecting multilayer metal structural parts of complex internal structures of engine turbines. The detection method of the present application solves the contradiction between conventional eddy current small wire diameter coils and large excitation current by using a variable width pulse string excitation mode and a placement type profiling differential eddy current probe based on small wire diameter coils, so that the probe can detect cracks without relative motion with the workpiece, and can detect fatigue cracks generated in the inner layer through the surface alloy material. In this way, not only the problem of detection in narrow space positions where the probe cannot move is solved, but also surface cracks of the surface metal material can be detected, and the damage degree of the surface cracks of the bottom metal material can also be quantitatively evaluated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nondestructive testing of aerospace engines, and particularly relates to an in-situ detection method for engine components in complex structures. BACKGROUND

[0002] In modern industry, aerospace engines are one of the advanced major complex equipment integrating the highest technologies of multiple disciplines, and are known as the crowning glory of modern industry. In order to ensure the safety during operation, especially for the repeated use of aerospace engines, in-situ detection without disassembly is needed to detect defects such as fatigue cracks in advance, so as to eliminate the hidden dangers that may cause air disasters. However, due to the complexity of the engine structure, the implementation of in-situ detection is extremely difficult. For example, the limitations of narrow space (the probe has almost no moving space), small detection area of key parts, irregular shape and other conditions make it difficult to perform this work. Moreover, the complex and special equipment components have poor in-service accessibility, and the internal fatigue cracks of multi-layer alloy are different from volume corrosion defects. In addition, the endoscope can only detect surface defects. Therefore, for the existing nondestructive testing technology, only the eddy current method is feasible. However, the conventional eddy current detection technology needs to scan the fatigue cracks (i.e. the workpiece and the probe need to move relative to each other), and can only detect cracks on the surface layer that the probe can reach, and thus cannot detect fatigue cracks in the inner layer through the surface alloy material. Therefore, the existing detection equipment cannot solve the above-mentioned in-situ detection problem. SUMMARY

[0003] The present application aims to overcome the shortcomings of the prior art, and provides an in-situ detection method for engine complex structures, which not only solves the problem of detection in narrow space where the probe cannot move, but also detects surface cracks of the surface metal material and quantitatively evaluates the damage degree of the surface cracks of the bottom metal material.

[0004] To solve the above problems, the present application provides an in-situ detection method for engine complex structures, which is implemented as follows:

[0005] An in-situ detection method for engine complex structures is used for detecting multi-layer metal structural parts of the complex internal structure of an engine turbine, which comprises the steps of establishing a reference model of a standard workpiece without cracks and measuring a workpiece to be detected. The method is characterized in that, in the steps of establishing a reference model of a standard workpiece without cracks and measuring a workpiece to be detected, a proximity probe based on a small-diameter coil is used to approach the detection part of the workpiece, a strong pulse eddy current field is excited, and the width of the pulse train is adjusted, so as to obtain the eddy current signals of different metal layers of the metal structural part at different main frequencies.

[0006] Further, the placement probe is designed as a profiling shell to adapt to the profile of the to-be-inspected part of the corresponding workpiece by the shape of the profiling shell; meanwhile, the placement probe is designed with the excitation coil and the detection coil separated, and the excitation coil excites the strong pulsed eddy current field.

[0007] Further, the diameter of the small-diameter coil of the excitation coil of the placement probe is designed to be greater than the thickness of the first metal layer of the to-be-inspected workpiece and less than the total thickness of the to-be-inspected workpiece.

[0008] Further, a pulse generator is used to excite the excitation coil, and the pulse generator is set to emit a plurality of single pulses to form a pulse train, and the width of the pulse train is adjustable.

[0009] Further, the step of establishing the reference model of the crack-free standard workpiece includes the following steps:

[0010] Further, the step of measuring the to-be-inspected workpiece includes the following steps:

[0011] a. Moving the placement probe to the to-be-inspected part and corresponding to the to-be-inspected part;

[0012] b. According to the step of establishing the reference model of the crack-free standard workpiece, selecting the width of the pulse train that can reach the thickness of the corresponding metal layer, and forming a transient pulsed eddy current field through the excitation coil of the placement probe;

[0013] c. Detecting the to-be-inspected workpiece through the detection coil of the placement probe, and sending the detection data to the computer system, and comparing the measured data with the standard comparison data by the computer system to determine whether the to-be-inspected workpiece has defects.

[0014] Further, the step of measuring the to-be-inspected workpiece also includes: detecting each metal layer of the to-be-inspected part layer by layer by selecting the width of the pulse train that can reach the thickness of the corresponding metal layer, and sending the detection data to the computer system, and comparing the measured data with the standard comparison data by the computer system to determine whether the corresponding metal layer of the to-be-inspected workpiece has defects.

[0015] Further, after the step of establishing the reference model of the crack-free standard workpiece and before the step of measuring the to-be-inspected workpiece, the placement probe is used for a detection-free detection of the to-be-inspected workpiece.

[0016] Further, in the step c, the acquired multiple groups of to-be-detected signals can also be subjected to difference balancing, and then compared with the standard control data.

[0017] Further, the actual measurement step of the to-be-detected workpiece further comprises: in the processing of the metal layer crack detection data, the detection data of the next metal layer can be determined after the interference and noise generated by the previous metal layer are screened out.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] The detection method of the present application solves the contradiction between the conventional eddy current small wire diameter coil and the large excitation current by adopting the placement type profiled differential eddy current probe based on the small wire diameter coil and the variable width pulse string excitation mode, and can achieve: (1) the probe can detect cracks without relative motion with the workpiece, solving the problem of detection in narrow space positions where the probe cannot move; (2) the probe can detect fatigue cracks generated in the inner layer through the surface alloy material, so that not only the surface cracks of the surface metal material can be detected, but also the damage degree of the surface cracks of the bottom metal material can be quantitatively evaluated. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the present application or the prior art described in the prior art description, it is obvious that, without creative labor, other drawings can also be obtained according to these drawings for the ordinary skilled in the art.

[0021] Figure 1 The flow chart of the detection method of the present application. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all the embodiments. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application.

[0023] In the description of the present application, the terms "first", "second" are only used for description purpose, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more features.

[0024] Due to the complexity of engine structure, narrow space inside the structure, poor accessibility in service, and many other problems for engineers in the design of eddy current testing method, large diameter coil cannot be placed in narrow space and cannot be moved for scanning, and in single frequency excitation, small diameter coil can pass through small current, but once the load power is too large, the coil will be damaged, so the conventional setting cannot reach the required penetration depth for detecting cracks in the inner layer of multi-layer dissimilar metal.

[0025] The present application aims to study an in-situ detection method for complex engine structure, which is used for detecting multi-layer metal structure of complex internal structure of engine turbine, and the specific method is as follows:

[0026] Reference is made to the accompanying drawings Figure 1 , which comprises the steps of establishing a reference model of a standard workpiece without cracks and actually measuring the workpiece to be detected, the performance of the workpiece to be detected is known in advance by establishing the reference model, the detection method is pre-played, and the data of the standard workpiece are obtained as a reference for data comparison in subsequent actual measurement, data processing and analysis. The actual measurement step is to detect in the actual work position. In the steps of establishing a reference model of a standard workpiece without cracks and actually measuring the workpiece to be detected, a small-diameter coil-based placement probe is used to approach the detection part of the workpiece, a strong pulse eddy current field is excited, and a small-diameter coil-based placement probe is used. The probe has a small overall volume and can be placed flexibly on the workpiece to be detected. The pulse excitation current is used to excite the strong pulse eddy current field, which can solve the contradiction between the small-diameter coil and the large excitation current. In order to reduce the heat generation of the excitation coil, the excitation signal is set as a pulse string with intermittent output, the interval time between pulses is very small, and the width of the pulse string is adjusted to obtain the eddy current signals of different metal layers of the metal structure under different main frequencies.

[0027] The step of establishing a reference model of a standard workpiece without cracks is to measure the properties of each layer of the multi-layer dissimilar metal structure to be detected, including electrical conductivity, magnetic permeability, and the thickness of each metal layer, establish a standard workpiece reference model, and according to the basic principle of eddy current testing, the penetration depth formula is as follows: Then, In this embodiment, the dissimilar metal layers include "metal A" and "metal B", the electrical conductivities thereof are σ a , σ b , the magnetic permeabilities thereof are μ a , μ b , and the thicknesses thereof are d a , d b . Taking metal A as an example, The period T=2△ of the pulse excitation signal is set, based on which the pulse generation function of the pulse generator is determined and the pulse width required for the pulse penetration depth to reach different metal layer thicknesses is calculated, and further the width, time, etc. of each pulse in the form of pulse train is decomposed, and the detection data of the different metal layers of the crack-free standard workpiece obtained at different pulse train pulse widths are obtained in advance and fixed as standard comparison data and stored in the control end. Each layer of metal can be detected as a whole detection unit, or can be further subdivided into multiple detection depth detection units according to the detection accuracy requirement. The obtained multiple groups of to-be-detected signals are subjected to difference balancing, and then compared with the standard comparison data. During detection, the pulse width is gradually increased to obtain a greater penetration depth.

[0028] The actual measurement step of the to-be-detected workpiece includes the following steps:

[0029] a. Move the placement probe to the to-be-detected position and correspond to the to-be-detected position; the placement probe is designed as a profiling shell to adapt to the shape of the to-be-detected position of the corresponding workpiece by the shape of the profiling shell.

[0030] In the embodiment, the placement probe includes a profiling shell, a magnetic core arranged at the middle part of the profiling shell, an excitation coil and a detection coil, and a positioning block adapted to the to-be-detected workpiece is arranged on the outer wall of the profiling shell, the positioning of the detection point is completed by matching the edge of the to-be-detected workpiece through the positioning block on the profiling shell, and the stability of the small-volume placement profiling probe and the accuracy of the detection point positioning are ensured.

[0031] b. According to the step of establishing the reference model of the crack-free standard workpiece, the width of the pulse train that can reach the thickness of the corresponding layer of metal is selected, and a transient pulse eddy current field is formed through the excitation coil of the placement probe;

[0032] c. The to-be-detected workpiece is detected through the detection coil of the placement probe, and the detection data is sent to the computer system, and the computer system compares the actual measurement data with the standard comparison data to determine whether the to-be-detected workpiece has defects.

[0033] It is well known that the aero-engine needs to work repeatedly in the special environment of high temperature, high pressure, high speed and high load for a long time. In order to ensure safety, the quality performance requirements of the components are very high. Generally, fatigue cracks in the components are not allowed. For multi-layer dissimilar metal components, defects in the surface layer or in the inner layer / bottom layer are not allowed, because they will cause great safety hazards. As a further improvement, the actual measurement step of the workpiece to be inspected includes: detecting each layer of metal layer of the detected part layer by layer by selecting the width of the pulse string that can reach the corresponding layer metal thickness of the penetration depth, and sending the detection data to the computer system respectively, and comparing the actual measurement data with the standard comparison data respectively by the computer system to determine whether the corresponding metal layer of the workpiece to be inspected has defects, each layer of metal layer is detected layer by layer in the order from top to bottom, and the detection is completed when defects are detected in the current layer, that is, the first layer of metal is detected, and the detection of the workpiece is completed when the detection result feedbacks that the layer has defects, that is, the detection is completed and is marked in the system, and the repair personnel picks up and replaces; when the detection result feedbacks that the first layer does not have defects, the detection of the deeper layer is carried out by increasing the pulse width. Ensure that each layer of the workpiece left in the engine does not have crack defects.

[0034] There are few inspirations for the detection of dissimilar metal structure composite layer in the prior art, especially the defect detection in the lower layer of dissimilar metal structure composite layer. In the actual measurement process, the vortex field of the upper and lower layers will naturally change under the same pulse width excitation due to the different properties of the upper and lower layers, which will affect the judgment of the detection result. Therefore, as a further improvement, the actual measurement step of the workpiece to be inspected further includes: in the processing of the metal layer crack detection data, the detection data of the next layer of metal layer can be determined after filtering out the interference and noise generated by the previous layer of metal layer.

[0035] As a further improvement, the excitation coil and the detection coil of the placement probe are separately arranged, so that the excitation coil can receive pulse excitation current. Further, the diameter of the small diameter coil of the excitation coil of the placement probe is designed to be greater than or equal to the thickness of the first layer of metal layer of the workpiece to be detected and less than the total thickness of the workpiece to be detected. The detection sensitivity is not only affected by the skin effect, but also closely related to the size of the coil wire diameter. In the arrangement of the coil, not only the defect depth but also the defect length should be considered. Most of the defect length is not greater than the thickness of the workpiece. The diameter of the small diameter coil is designed to be greater than the thickness of the first layer of metal layer of the workpiece to be detected to ensure the penetration depth, and the diameter of the small diameter coil is less than the total thickness of the workpiece to be detected to ensure that the sensitive area of the probe can cover the defect length. In this way, the magnetic field is concentrated and the penetration depth is not affected.

[0036] As further improvement, after the step of establishing the reference model of the crack-free standard workpiece and before the step of implementing the actual measurement of the workpiece to be inspected, an empty detection of the workpiece to be inspected is implemented using the placement probe, the potential is balanced through the empty detection, and the accuracy of the detection is improved.

[0037] The preferred embodiments of the present application have been described above with the preferred embodiments, but the present application is not limited to them and can be variously changed and modified by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for in-situ detection of complex engine structures, for the detection of multilayered dissimilar metal structures of complex internal engine turbine structures, comprising: The method comprises the steps of establishing a reference model of a crack-free standard workpiece and measuring a workpiece to be inspected, wherein in the steps of establishing a reference model of a crack-free standard workpiece and measuring a workpiece to be inspected, a proximity probe based on a small-diameter coil is used to approach the part to be inspected of the workpiece, a strong pulsed eddy current field is excited, and the width of the pulse train is adjusted, so as to obtain the eddy current signals of different metal layers of the metal structure under different main frequencies. The proximity probe is designed as a profiling shell to adapt to the shape of the part to be inspected of the corresponding workpiece by using the shape of the profiling shell. Meanwhile, the proximity probe is designed with a separate excitation coil and detection coil, and the strong pulsed eddy current field is excited by the excitation coil. The diameter of the small-diameter coil of the excitation coil of the proximity probe is designed to be greater than the thickness of the first metal layer of the workpiece to be inspected and less than the total thickness of the workpiece to be inspected.

2. The method of claim 1, wherein the engine complex is an engine complex of an automobile. The excitation coil is excited by a pulse generator, and the pulse generator is set to emit a plurality of single pulses to form a pulse train, and the width of the pulse train is adjustable.

3. The method of claim 1, wherein the engine complex is a diesel engine. In the step of establishing a reference model of a crack-free standard workpiece, the properties of each metal layer of the multi-layer heterogeneous metal structure to be inspected, including electrical conductivity, magnetic permeability and thickness, are determined in advance, a standard workpiece reference model is established, the pulse generation function of the pulse generator is determined, and the detection data of different metal layers of the crack-free standard workpiece under different pulse widths are obtained in advance and fixed as standard comparison data.

4. The method of claim 3, wherein the engine complex is a diesel engine. The measurement step of the workpiece to be inspected comprises the following steps: a. moving the proximity probe to the part to be inspected and corresponding to the part to be inspected; b. selecting the width of the pulse train that can reach the thickness of the corresponding metal layer according to the step of establishing a reference model of a crack-free standard workpiece, and forming a transient pulsed eddy current field by the excitation coil of the proximity probe; c. detecting the workpiece to be inspected by the detection coil of the proximity probe, and sending the detection data to the computer system, and comparing the measured data with the standard comparison data by the computer system to determine whether the workpiece to be inspected has defects.

5. The method of claim 4, wherein the engine complex is an engine complex of an automobile. The measurement step of the workpiece to be inspected further comprises: detecting each metal layer of the part to be inspected layer by layer after excitation by selecting the width of the pulse train that can reach the thickness of the corresponding metal layer, and sending the detection data to the computer system, and comparing the measured data with the standard comparison data by the computer system to determine whether the corresponding metal layer of the workpiece to be inspected has defects; each metal layer is detected layer by layer in the order from top to bottom, and when defects are detected in the current layer, the detection is completed and the workpiece to be inspected is repaired.

6. The method of claim 4, wherein the engine complex is a diesel engine. After the step of establishing a reference model of a crack-free standard workpiece and before the step of measuring a workpiece to be inspected, the proximity probe is used for empty detection of the workpiece to be inspected.

7. The method of claim 4, wherein the engine complex is an engine complex of an automobile. In step c, the obtained multiple groups of detection signals are subjected to difference balancing, and then compared with the standard comparison data.

8. The method of claim 5, wherein the engine complex is a diesel engine. In the processing of the metal layer crack detection data, the detection data of the next metal layer are determined after filtering out the interference and noise generated by the previous metal layer.

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