A method and apparatus for detecting surface roughness of non-metallic workpieces

Abstract

The present application relates to non-metallic workpiece nondestructive testing technical field, especially to a kind of method for detecting non-metallic workpiece material surface roughness, the present application proposes a new idea, on the basis of indirect measurement method, it uses the electrically conductive material with negative mold function as medium to transfer the roughness profile of non-metallic workpiece surface, the height difference between the upper and lower surfaces of electrically conductive material is detected by eddy current method, the profile curve of the lower surface of electrically conductive material is calculated and drawn back through the detection result of height difference, so as to indirectly obtain the surface roughness of non-metallic workpiece, the present application solves the problem that the non-metallic surface roughness is difficult to detect at present. In the method, the negative mold material does not need to contact the workpiece, and does not need to wait for the negative mold material to solidify and demould, so that the effect of simple operation and high detection efficiency is realized;Eddy current detection is used, response is fast, interference factor is small, and result accuracy is higher.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of non-destructive testing of non-metallic workpieces, and in particular to a method and device for detecting the surface roughness of a non-metallic workpiece. BACKGROUND

[0002] In modern industry, more and more non-metallic materials are used to make various components. Due to design and process requirements, especially for major equipment in the aerospace or nuclear industries, the surface roughness of the materials often needs to be evaluated.

[0003] Because most non-metallic materials have irregular shapes and different hardnesses, they differ greatly from traditional metallic materials, and the current detection methods are no longer applicable, so further research is needed on the detection methods. Existing measurement methods include contact measurement, non-contact measurement, comparative testing methods, and indirect measurement methods.

[0004] Contact measurement mainly uses a stylus detection method, which is stable and reliable, but can easily scratch and damage high-precision surfaces. Non-contact measurement includes optical measurement, ultrasonic methods, scanning tunneling microscope methods, etc., which do not damage the surface but have high requirements for the detection environment. Comparative testing methods use human visual and tactile comparison to make judgments, which are subjective and have certain errors. Indirect measurement methods use a negative mold method to take a negative of the workpiece surface, and then measure the removed negative copy, which is a complex process.

[0005] In summary, the existing detection methods are difficult to achieve non-destructive, efficient, and high-precision, so the present application studies a method for detecting the surface roughness of a non-metallic workpiece to solve the above problems. SUMMARY

[0006] To solve the above problems, the present application proposes a new approach, which uses an electrically conductive material with negative mold function as a medium to transfer the rough profile of the non-metallic workpiece surface based on the indirect measurement method. The height difference between the upper and lower surfaces of the electrically conductive material is detected by an eddy current detection assembly, and the surface roughness of the non-metallic workpiece is indirectly obtained. The present application is implemented as follows:

[0007] A method for detecting the surface roughness of a non-metallic workpiece, which involves laying a layer of electrically conductive material on the surface of the non-metallic workpiece, keeping the upper surface of the electrically conductive material flat, and making the lower surface of the electrically conductive material conform to the surface of the non-metallic workpiece. Then, an eddy current detection assembly is used to detect the eddy current on the upper surface of the electrically conductive material, obtain the height difference of the lower surface of the electrically conductive material, and use a computer system to perform inverse calculation to obtain the surface roughness of the non-metallic workpiece.

[0008] Further, the conductive material is in liquid or gel or powder form, so that the lower surface of the conductive material can be in close contact with the surface of the non-metallic workpiece.

[0009] Further, the conductive material is placed in a flexible bag, and the flexible bag is placed on the surface of the non-metallic workpiece, so that the lower surface of the conductive material is in close contact with the surface of the non-metallic workpiece.

[0010] Further, a horizontal reference plate is placed on the upper surface of the conductive material, so that the upper surface of the conductive material remains planar.

[0011] Further, the application also discloses a method for detecting the roughness of the surface of a non-metallic workpiece, a horizontal reference plate is arranged at the bottom of the eddy current detection assembly, and a flexible negative mold structure with conductivity is arranged at the bottom of the horizontal reference plate; during detection, the bottom of the flexible negative mold structure is in close contact with the non-metallic workpiece with a rough surface, the bottom of the flexible negative mold structure forms a height difference, the eddy current detection assembly detects the profile of the bottom of the flexible negative mold structure, and an evaluation value of the roughness of the surface of the non-metallic workpiece is obtained through data processing.

[0012] Further, the method comprises the following steps:

[0013] S1: placing the non-metallic workpiece to be detected horizontally on a detection workbench, and placing the eddy current detection assembly with the flexible negative mold structure vertically on the upper surface of the non-metallic workpiece, and confirming whether the eddy current detection assembly is stably placed on the upper surface of the non-metallic workpiece;

[0014] S2: when the eddy current detection assembly is stably placed on the upper surface of the non-metallic workpiece, the upper surface of the flexible negative mold structure remains horizontal, the bottom of the flexible negative mold structure is in contact with and flexibly attached to the upper surface of the non-metallic workpiece, and the bottom of the flexible negative mold structure forms a profile conforming to the shape of the upper surface of the non-metallic workpiece;

[0015] S3: the eddy current detection assembly detects the flexible negative mold structure with conductivity under the same horizontal reference surface, and obtains an eddy current signal;

[0016] S4: the eddy current signal is converted and processed by a data processing analyzer, and parameters for calculating the roughness of the surface of the non-metallic workpiece are indirectly obtained.

[0017] Further, in the step S4, the data processing comprises:

[0018] S41: according to the size of the actual detection workpiece, the workpiece is divided into one or more sampling areas, and the sampling length of each detection is determined;

[0019] S42: converting the eddy current signal obtained in the sampling length into a distance signal from the horizontal reference surface to each point on the bottom profile of the negative mold structure;

[0020] S43: plotting the distance signal into a profile signal curve, and performing data processing on the profile information curve,

[0021] Obtaining a parameter for evaluating the roughness of a non-metal surface.

[0022] Further, the eddy current signal obtained in step S42 is subjected to signal correction, and the conversion of the eddy current signal and the distance signal is performed after the correction processing.

[0023] Further, the flexible negative mold structure can be integrally arranged with the eddy current detection assembly or arranged separately.

[0024] When arranged separately, the eddy current detection assembly adopts a point-type eddy current detection assembly or a line-array eddy current detection assembly, the flexible negative mold structure is first placed on the upper surface of the non-metal workpiece, and then the eddy current detection assembly is placed on the horizontal reference surface of the flexible negative mold structure to move and scan the sampling area.

[0025] When arranged integrally, the eddy current detection assembly adopts a surface-array eddy current detection assembly, and the eddy current detection assembly with the flexible negative mold structure is directly placed on the upper surface of the non-metal workpiece to perform static detection on the sampling area.

[0026] Compared with the prior art, the present application can obtain the following technical effects:

[0027] The present application sets the conductive material on the surface of the non-metal workpiece, combines the eddy current detection method, uses the conductive material to completely transfer the rough particle size and shape of the non-metal surface, and then indirectly obtains the roughness information of the non-metal workpiece surface by detecting the height difference of the lower surface of the conductive material.

[0028] First, the present application installs the conductive material in the flexible bag to form a flexible negative mold structure, the flexible negative mold structure includes a flexible bag, and the negative mold material is arranged in the bag, and the conductive liquid or conductive gel or conductive powder with fluidity and not solidified is used as the negative mold material.

[0029] II. The horizontal reference plate is arranged at the lower end of the eddy current detection assembly. During detection, the eddy current detection assembly and the flexible negative mold structure are vertically placed on the surface of the workpiece to be detected. Under the action of natural weight or artificial force, the horizontal reference plate can ensure that the upper surface of the flexible negative mold structure is in a horizontal state, realize the detection of the eddy current detection assembly on the same reference surface, and make the flexible material in a stable state.

[0030] III. The conductive liquid or conductive colloid or conductive powder is used as a medium, and eddy current detection is adopted, so that the detection result is accurate and the data response is fast. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the present application or the prior art or the descriptions in the prior art, it is obvious that other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0032] Figure 1 The flow chart of the detection method disclosed in the present application.

[0033] Figure 2 The non-metallic workpiece to be detected.

[0034] Figure 3 The rendering diagram of Figure 2

[0035] Figure 4 The schematic diagram of detection using a point eddy current detection assembly.

[0036] Figure 5 The exploded schematic diagram of Figure 3

[0037] Figure 6 The rendering diagram of Figure 5

[0038] Figure 7 The schematic diagram of detection using a line array eddy current detection assembly.

[0039] Figure 8 The schematic diagram of one embodiment of detection using a surface array eddy current detection assembly.

[0040] Figure 9 The schematic diagram of another embodiment of detection using a surface array eddy current detection assembly.

[0041] Figure 10 The rendering diagram of Figure 9

[0042] In the figure: 10 - eddy current detection assembly; 20 - horizontal reference plate; 30 - flexible negative mold structure; 40 - non-metallic workpiece.​​​​ Detailed Implementation

[0043] The following description, in conjunction with the accompanying drawings and specific embodiments, will further illustrate this aspect.

[0044] Surface roughness refers to the unevenness of a machined surface, characterized by small gaps and minute peaks and valleys. The distance between two peaks or valleys (wavelength) is very small and falls under the category of microscopic geometric errors. Surface roughness is closely related to the fit properties, wear resistance, fatigue strength, contact stiffness, vibration, and noise of mechanical parts, and has a significant impact on the service life and reliability of mechanical products. Therefore, it is necessary to inspect the surface roughness of workpieces.

[0045] In critical equipment used in aerospace or nuclear industries, the variety and quantity of parts are numerous, and defects in the workpieces used in the equipment are unacceptable. This necessitates rapid and accurate inspection and evaluation of the workpieces. For the inspection of surface roughness of non-metallic workpieces, there is an urgent need to design an inspection device and method that is highly applicable, capable of rapid inspection, and does not cause secondary damage to the workpiece under inspection.

[0046] Based on this, the present invention adopts a new detection approach and a method for detecting the surface roughness of non-metallic workpieces. A layer of conductive material is laid on the surface of the non-metallic workpiece, with the upper surface of the conductive material kept flat and the lower surface conforming to the surface of the non-metallic workpiece. Then, an eddy current detection component is used to perform eddy current detection on the upper surface of the conductive material to obtain the height difference of the lower surface of the conductive material. The computer system is then used to perform back calculations to obtain the surface roughness of the non-metallic workpiece.

[0047] Furthermore, the conductive material is in liquid, colloidal, or powder form, so that the lower surface of the conductive material can conform to and adhere to the surface of the non-metallic workpiece.

[0048] Furthermore, conductive material is placed inside a flexible bag, and the flexible bag is placed on the surface of a non-metallic workpiece, so that the lower surface of the conductive material fits snugly against the surface of the non-metallic workpiece. Alternatively, conductive material is placed inside an enclosure structure and sealed with a flexible cloth, and the entire flexible structure containing conductive material is placed on the surface of the non-metallic workpiece, so that the lower surface of the conductive material fits snugly against the surface of the non-metallic workpiece.

[0049] Furthermore, a horizontal reference plate is placed on the upper surface of the conductive material to keep the upper surface of the conductive material flat.

[0050] Reference Appendix Figures 1-10 , attached Figure 1 The flowchart for this method is attached. Figure 2 The non-metallic workpiece to be inspected has an uneven, wavy surface (see attached document). Figure 3), the application further discloses a method for detecting the roughness of a nonmetallic workpiece surface, a horizontal reference plate is arranged at the bottom of the eddy current detection assembly, a flexible negative mold structure with electrical conductivity is arranged at the bottom of the horizontal reference plate (i.e. the eddy current detection assembly, the horizontal reference plate and the flexible negative mold structure are sequentially arranged from top to bottom), and the bottom of the flexible negative mold structure at the lower end of the eddy current detection assembly is attached to the nonmetallic workpiece with a rough surface during detection. The bottom of the flexible negative mold structure forms a height difference, the distance from the bottom profile surface of the water bag structure to the horizontal reference plate is detected, the data of the bottom profile line of the water bag structure is acquired, and the evaluation value of the roughness of the nonmetallic workpiece surface is obtained through data processing.

[0051] Specifically, the method comprises the following steps:

[0052] S1: placing a nonmetallic workpiece to be detected horizontally on a detection workbench, vertically placing an eddy current detection assembly with a flexible negative mold structure on the upper surface of the nonmetallic workpiece, and confirming whether the eddy current detection assembly is stably placed on the upper surface of the nonmetallic workpiece;

[0053] S2: after the eddy current detection assembly is stably placed on the upper surface of the nonmetallic workpiece, the upper surface of the flexible negative mold structure remains horizontal, the bottom of the flexible negative mold structure is in contact with and flexibly attached to the upper surface of the nonmetallic workpiece under the action of natural gravity or artificial force, and the bottom of the flexible negative mold structure forms a profile conforming to the shape of the upper surface of the nonmetallic workpiece;

[0054] S3: detecting the flexible negative mold structure with electrical conductivity under the same horizontal reference surface by the eddy current detection assembly, and acquiring an eddy current signal;

[0055] S4: converting and processing the eddy current signal by a data processing analyzer to indirectly acquire parameters for calculating the roughness of the nonmetallic workpiece surface.

[0056] Further, in the step S4, the data processing comprises:

[0057] S41: dividing the actual detection workpiece into one or more sampling regions according to the size of the actual detection workpiece, and determining the sampling length for each detection;

[0058] S42: converting the eddy current signal acquired within the sampling length into a distance signal from the horizontal reference surface to each point on the bottom profile of the negative mold structure;

[0059] During the movement scanning or static scanning of the eddy current detection assembly, the eddy current signal appears different depths of eddy current signals along with the fluctuating profile of the bottom of the flexible negative mold structure, and these tiny different depths of eddy current signals are converted into distance signals.

[0060] S43: plot the distance signal into a profile signal curve, and data process the profile information curve,

[0061] The height parameter, the interval parameter and the comprehensive parameter are obtained for evaluating the roughness of the nonmetal surface.

[0062] The profile of the negative mold is smaller than the actual profile, so the eddy current signal obtained in step S42 is corrected; since the roughness is a microstructure, in order to facilitate evaluation, the signal is amplified and filtered before correction, and then the corrected signal is converted. The converted data is operated, and the related parameters of the actual surface roughness can be displayed on the display of the detection device.

[0063] Further, the flexible negative mold structure can be integrally arranged with the eddy current detection assembly or arranged separately.

[0064] Referring to the accompanying drawings Figures 4-10 When arranged separately, the eddy current detection assembly adopts a point-type eddy current detection assembly or a linear array eddy current detection assembly or a planar array eddy current detection assembly, the flexible negative mold structure is placed on the upper surface of the nonmetal workpiece, and the eddy current detection assembly is placed on the horizontal reference surface of the flexible negative mold structure to move and scan the sampling area.

[0065] Referring to the accompanying drawings Figure 9 , the accompanying drawings Figure 10 When arranged integrally, the eddy current detection assembly adopts a planar array eddy current detection assembly, the eddy current detection assembly with the flexible negative mold structure is vertically placed on the upper surface of the nonmetal workpiece to statically detect the sampling area, and when the current area is detected, the planar array eddy current detection assembly is moved to the next detection area for detection.

[0066] The application also designs a device for detecting the surface roughness of a nonmetal workpiece, which can use any of the above methods for detection. The device comprises an eddy current detection assembly, a data processing analyzer, a controller and a display which are electrically connected to each other, the bottom of the eddy current detection assembly is provided with a horizontal reference plate, and the lower end of the horizontal reference plate is integrally provided with a flexible negative mold structure.

[0067] Preferably, the flexible negative mold structure comprises a flexible bag, the inside of the flexible bag is provided with a negative mold material which can transfer the rough profile shape of the nonmetal workpiece surface, and the negative mold material has electrical conductivity, and the bottom of the flexible negative mold structure is in contact with the nonmetal workpiece surface.

[0068] The upper end of the horizontal reference plate is provided with an eddy current detection assembly, and the eddy current detection assembly detects the profile signal of the bottom of the flexible negative mold structure. The horizontal reference plate is in the form of a thin plate and also has electrical conductivity, and does not affect the eddy current detection.

[0069] The flexible negative mold structure is placed on the surface of the non-metallic workpiece to be detected, and the flexible negative mold structure is naturally attached to the surface to be detected. Thus, the bottom of the flexible negative mold structure forms a high and low profile conforming to the surface of the non-metallic workpiece to be detected. The bottom profile of the flexible negative mold structure is detected by the eddy current detection assembly, so that the roughness parameters of the surface of the non-metallic workpiece can be indirectly obtained.

[0070] As a further improvement, the deformation of the upper surface of the flexible negative mold structure is limited by the horizontal reference plate, so that the upper surface of the flexible negative mold structure always remains planar. The horizontal reference plate allows the eddy current field to easily detect the bottom profile of the flexible negative mold structure, and the detection is performed on the same plane. The horizontal reference plate is actually a calibrated detection plane, which ensures that the measurement of the bottom profile of the flexible negative mold structure is on the same reference.

[0071] As a further improvement, the negative mold material is a liquid or gel or powder with flowability. Such material has negative mold function, good flowability and is not easy to solidify. Preferably, the flexible negative mold bag is filled with conductive liquid, and more preferably, the conductive liquid is saturated sodium chloride solution. In other embodiments, other materials can also be used for filling.

[0072] As a further improvement, the eddy current detection assembly adopts a point eddy current detection assembly or a line array eddy current detection assembly or a surface array eddy current detection assembly, which can be selected according to different detection requirements.

[0073] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method of detecting surface roughness of a non-metallic workpiece, comprising: The method comprises the following steps: a conductive material is laid on the surface of the nonmetallic workpiece; the upper surface of the conductive material is kept flat; the lower surface of the conductive material is inlaid with the surface of the nonmetallic workpiece; then, the upper surface of the conductive material is detected by using an eddy current detection assembly to obtain the height difference of the lower surface of the conductive material; and finally, the surface roughness of the nonmetallic workpiece is obtained by using a computer system to perform reverse calculation.

2. The method of claim 1, wherein The conductive material is in liquid, gel or powder form so that the lower surface of the conductive material can be inlaid with the surface of the nonmetallic workpiece.

3. The method of claim 2, wherein the non-metallic workpiece is a glass workpiece. The conductive material is filled into a flexible bag, and the flexible bag is placed on the surface of the nonmetallic workpiece so that the lower surface of the conductive material is inlaid with the surface of the nonmetallic workpiece.

4. The method of claim 3, wherein the non-metallic workpiece is a glass workpiece. A horizontal reference plate is placed on the upper surface of the conductive material so that the upper surface of the conductive material is kept flat.

5. A method of detecting surface roughness of a non-metallic workpiece, characterized by, A horizontal reference plate is arranged at the bottom of the eddy current detection assembly, and a flexible negative mold structure with conductivity is arranged at the bottom of the horizontal reference plate; during detection, the bottom of the flexible negative mold structure is inlaid with the nonmetallic workpiece with a rough surface; the bottom of the flexible negative mold structure forms a height difference; the eddy current detection assembly detects the height difference between the upper surface and the lower surface of the flexible negative mold structure; and the evaluation value of the surface roughness of the nonmetallic workpiece is obtained through data processing.

6. The method of claim 5, wherein the non-metallic workpiece is a glass workpiece. The method comprises the following steps: S1: the nonmetallic workpiece to be detected is horizontally placed on a detection workbench, and an eddy current detection assembly with a flexible negative mold structure is vertically placed on the upper surface of the nonmetallic workpiece; whether the eddy current detection assembly is stably placed on the upper surface of the nonmetallic workpiece is confirmed; S2: when the eddy current detection assembly is stably placed on the upper surface of the nonmetallic workpiece, the upper surface of the flexible negative mold structure is kept horizontal, the bottom of the flexible negative mold structure is in contact with and inlaid with the upper surface of the nonmetallic workpiece, and the bottom of the flexible negative mold structure forms a contour that is in conformity with the shape of the upper surface of the nonmetallic workpiece; S3: the eddy current detection assembly detects the flexible negative mold structure with conductivity under the same horizontal reference surface to obtain an eddy current signal; S4: the eddy current signal is converted and processed by a data processing analyzer to indirectly obtain parameters for calculating the surface roughness of the nonmetallic workpiece.

7. The method of claim 6, wherein the non-metallic workpiece is a glass workpiece. In the step S4, the data processing comprises: S41: the actual detection workpiece is divided into one or more sampling regions according to the size of the actual detection workpiece, and the sampling length of each detection is determined; S42: the eddy current signal obtained within the sampling length is converted into a distance signal from the horizontal reference surface to each point on the contour of the bottom of the negative mold structure; S43: the distance signal is drawn into a contour signal curve, the contour information curve is processed, and parameters for evaluating the surface roughness of the nonmetallic workpiece are obtained.

8. The method of claim 7, wherein the non-metallic workpiece is a glass workpiece. The eddy current signal obtained in the step S42 is corrected, and the corrected eddy current signal is converted into a distance signal from the horizontal reference plate to the bottom of the flexible negative mold structure.

9. The method of claim 8, wherein the non-metallic workpiece is a glass workpiece. The flexible negative mold structure can be integrally arranged with the eddy current detection assembly or separately arranged. When the vortex detection assembly is arranged separately, the vortex detection assembly is a point vortex detection assembly or a linear array vortex detection assembly, the flexible negative mold structure is designed to be suitable for the size of the non-metal workpiece and is placed on the upper surface of the non-metal workpiece, and then the vortex detection assembly is placed on the horizontal reference surface of the flexible negative mold structure to move and scan the sampling area; When the vortex detection assembly is arranged integrally, the vortex detection assembly is a surface array vortex detection assembly, and the vortex detection assembly with the flexible negative mold structure is directly placed on the upper surface of the non-metal workpiece to detect the sampling area statically.

10. An apparatus for detecting surface roughness of a metal workpiece using any of the methods of claims 1-9, the apparatus comprising an eddy current detection assembly, a data processing analyzer, a controller, and a display; wherein, The bottom of the vortex detection assembly is provided with a horizontal reference plate, and the lower end of the horizontal reference plate is provided with a flexible negative mold structure; The flexible negative mold structure comprises a flexible bag, the inside of the flexible bag is provided with a negative mold material capable of transferring the rough profile shape of the surface of the non-metal workpiece, and the negative mold material is electrically conductive, and the bottom of the flexible negative mold structure is in contact with the surface of the non-metal workpiece; The upper end of the horizontal reference plate is provided with a vortex detection assembly, and the vortex detection assembly detects the profile signal of the bottom of the flexible negative mold structure; The horizontal reference plate limits the deformation of the upper surface of the flexible negative mold structure, and the upper surface of the flexible negative mold structure always maintains a horizontal plane state.

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