Method for detecting internal defects of aramid rope core conveying belt with straight warp and straight weft structure

Abstract

The invention discloses a method for detecting internal defects of an aramid rope core transmission band with a straight-warp straight-weft structure, and belongs to the field of industrial non-destructive detection.An electromagnetic wave transmission transmission band is adopted, signal perturbation is amplified and analyzed at a receiving end, imaging and recognition are carried out by utilizing internal aramid rope core defect characteristics, and a detection result is obtained. And the defect condition of the aramid rope core in the conveying belt can be judged. According to the aramid rope core defect detection method, micro disturbance of electromagnetic waves under certain power is utilized, fundamental waves of detection signals have no effect on defect detection, weak signals are analyzed, namely, secondary and tertiary signals are resonated, aramid rope core defect detection is achieved, the detection result is accurate, and the problem that internal defects of an aramid rope core conveying belt cannot be recognized can be solved.

Description

Technical Field

[0001] The invention relates to an electromagnetic wave defect detection method, belongs to the field of industrial non-destructive testing, and specifically relates to an internal defect detection method for an aramid rope core transmission belt with a straight warp and straight weft structure. Background Art

[0002] Belt conveyor is a continuous transportation equipment in modern production. It has the advantages of large transportation capacity, long distance, low energy consumption, stable operation, convenient loading and unloading, and suitable for bulk material transportation. It is widely used in mining, coal, electricity, chemical industry, metallurgy, construction and other fields. Together with cars and trains, it has become the three main transportation tools. Belt conveyor is mainly composed of transmission belt, frame, roller, drum, tensioning device, transmission device, etc. Among them, the transmission belt is the key component of belt conveyor traction and transportation, accounting for 40%-60% of the total belt conveyor cost.

[0003] In order to strengthen the support force of the conveyor belt, increase the wear resistance and service life of the conveyor surface, a belt core is added to the conveyor belt. At present, the belt core is mainly a steel rope core, and some use aramid rope cores. The aramid rope core mainly adopts a straight warp and straight weft structure, which has the characteristics of strong tension, light weight, and energy-saving operation. It is gradually replacing the steel rope core conveyor belt in some fields.

[0004] During operation, the conveyor belt may fail, especially at the joints of the conveyor belt. Once a failure occurs, it will cause major safety accidents such as belt breakage or longitudinal tearing. In order to avoid the occurrence of failures, internal defect detection is necessary. It is of great significance to avoid potential failures by discovering internal defects.

[0005] At present, the aramid core in the aramid core transmission belt is a straight warp and straight weft structure, which is difficult to identify under the covering rubber layer using X-ray. Therefore, a new detection method is needed to detect internal defects of the aramid core transmission belt.

[0006] Electromagnetic waves can be used in many applications for rubber detection, but the detection signals of aramid rope cores with internal straight warp and straight weft structures are almost the same, making it difficult to distinguish internal defects.

[0007] Aramid rope core transmission belt contains carbon, and the carbon transmission belt has a certain absorption of electromagnetic waves. At the same time, a signal that is too large is not conducive to the extraction of micro-disturbance signals and is difficult to distinguish. A signal that is too small is difficult to penetrate the carbon transmission belt. There are certain requirements for the selection of power, which should not be too large but also able to transmit signals. Summary of the invention

[0008] In order to solve the problem that it is difficult to detect internal defects of the straight warp and straight weft structure aramid rope core transmission belt, the present invention adopts an electromagnetic wave source of a certain power as the emission source, and utilizes the characteristics that the electromagnetic wave radiation passes through the transmission belt, and the internal information is a micro-disturbance when the electromagnetic wave signal is extracted. By extracting and amplifying the micro-disturbance signal at the receiving end, the micro-disturbance signal is clearly displayed, and the normal value and defect value of the aramid rope core of the transmission belt are directly displayed, providing an aramid rope core transmission belt internal defect detection method with the characteristics of non-radiation safety.

[0009] The technical solution adopted by the present invention to solve its technical problems is: a method for detecting internal defects of an aramid rope core transmission belt with a straight warp and straight weft structure, selecting an electromagnetic wave source of a certain power, and the power of the wave source determines the thickness of the transmission belt and the imaging clarity. Then, the frequency of the wave source is selected according to the size of the aramid rope core defect using the characteristics of electromagnetic wave micro-disturbance. Finally, the receiving end signal is amplified. Electromagnetic waves are emitted by the wave source, and the electromagnetic waves are received on the other side through the transmission belt. The cross section of the transmission belt can be imaged by a line scan, and then a planar imaging map of the aramid rope core defect can be formed by moving the transmission belt longitudinally. Since the power energy of the wave source is relatively small, and the emission is perpendicular to the transmission belt direction, it is almost harmless to the surrounding environment and personnel, and is a radiation-free detection method.

[0010] The present invention has the following beneficial effects:

[0011] Defect detection of carbon-containing transmission belts has high requirements on the selection of electromagnetic wave power. The present invention realizes defect detection of carbon-containing transmission belts by selecting corresponding power under a certain thickness of the transmission belt.

[0012] The present invention utilizes the micro-disturbance of electromagnetic waves at a certain power, wherein the fundamental wave of the detection signal has no effect on defect detection. The present invention adopts the analysis of weak signals, i.e. resonating the secondary and tertiary signals, and further amplifying the signals by micro-disturbance, thereby realizing aramid rope core defect detection with accurate detection results.

[0013] The electromagnetic wave source of the present invention has low power and low working voltage, has no radiation to the operator, is safe and environmentally friendly, has no high-voltage reduction and explosion-proof measures, and is particularly suitable for working in a mine environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of electromagnetic wave transmission in the detection transmission belt;

[0015] Figure 2 It is a schematic diagram of single signal detection of electromagnetic wave source;

[0016] Figure 3 It is a schematic diagram of detection after amplification of a single signal;

[0017] Figure 4 It is a schematic diagram of different order detection after signal amplification;

[0018] Figure 5 This is a schematic diagram of defect detection after signal amplification;

[0019] Figure 6 It is a schematic diagram of defect detection imaging.

[0020] In the figure, the reference numerals are:

[0021] Transmitting device 1, aramid rope core transmission belt 2, receiving device 3. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above-mentioned purpose, the present invention adopts the following technical scheme.

[0023] The present invention proposes a method for detecting internal defects of an aramid rope core transmission belt with a straight warp and straight weft structure, which is mainly divided into four steps: one is the selection of the power size of the electromagnetic wave source, the second is the selection of the electromagnetic wave micro-disturbance order and the determination of the wave source frequency, the third is imaging the inside of the aramid rope core transmission belt, and the fourth is imaging and identifying the internal defects of the aramid.

[0024] Selection of electromagnetic wave source power: As the aramid core transmission belt requires wear resistance, the thickness of the rubber layer varies according to the specific specifications. It is generally divided into three parts: upper cover rubber, middle core rubber reinforcement layer, and lower cover rubber. Wear-resistant carbon is added to the rubber of each part. The middle core rubber reinforcement layer of the aramid core transmission belt is a multi-layer straight warp and straight weft aramid structure, such as Figure 1 As shown, a cross-sectional view of an aramid rope core transmission belt 2. Figure 1 In the figure, the transmitting device 1 of the electromagnetic wave source transmits electromagnetic waves, and the receiving device 3 of the electromagnetic wave source receives electromagnetic waves. The electromagnetic waves are emitted from the transmitting device 1 along the direction of the arrow, pass through the aramid rope core transmission belt 2, and reach the receiving device 3.

[0025] Rubber and aramid absorb less electromagnetic waves, and the carbon in rubber absorbs electromagnetic waves to a certain extent, which leads to the need to select appropriate power when the wave source penetrates the transmission belt. Specifically, when the thickness of the aramid rope core transmission belt is less than 10mm, the wave source power can be selected within 0.2 watts; when the thickness of the aramid rope core transmission belt is less than 20mm, the wave source power can be selected within 0.5 watts; when the thickness of the aramid rope core transmission belt is more than 20mm, the wave source power can be selected within 1 watt; the wave source power can penetrate the transmission belt for internal imaging.

[0026] Selection of electromagnetic wave micro-disturbance order and determination of wave source frequency: The selection of electromagnetic wave micro-disturbance order is mainly related to the single detection signal. After the electromagnetic wave single detection signal passes through the aramid rope core transmission belt, the signal at the receiving end is as follows: Figure 2 As shown, the maximum peak in the middle of the signal is the fundamental wave, and the signal fluctuates and decays toward both ends, representing the second and third harmonics, etc., respectively. After Fourier transform, it is generally expressed in order. The fundamental wave of a single detection signal is mainly related to the thickness of the transmission belt. The internal aramid rope core almost does not absorb the fundamental wave, so it cannot be displayed in the fundamental wave. The second and third harmonics are related to the aramid rope core, and the amplitude of the harmonics can represent the difference in the longitude and latitude of the aramid rope core. The fundamental wave signal is a directly penetrating signal and is related to the thickness of the transmission belt. The second harmonic is a tiny signal attached to the fundamental wave, which is an expression of different signals inside the transmission belt. The third harmonic is an even smaller signal attached to the second harmonic, and is also an expression of different signals inside the transmission belt. Generally, the change value of the fundamental wave signal is very small, and the change of the signal after the separation of the second harmonic and the third harmonic is large.

[0027] Since the harmonic amplitude is very small, it is generally called a micro-disturbance. It is necessary to amplify the amplitude direction, such as Figure 3 As shown, Figure 3 The dashed line is the curve before the amplitude is amplified, and the solid line is the curve after the amplitude is amplified by 2 times. It can be seen that after the amplitude is amplified, the fluctuation of the curve increases. By amplifying the amplitude of the harmonic, the difference in micro-disturbance will increase, and the detection of the warp and weft of the aramid rope core can be realized, and then the detection of internal defects can be realized.

[0028] When testing aramid rope core transmission belts, a combination of signal amplification and effective order selection is used, such as Figure 4 As shown, line a is the fundamental signal, which is a horizontal line. Based on the fundamental signal a, it is amplified and adjusted to the state of the 1st or 2nd order signal as shown in line b. The dotted line c is the curve of a single detection signal. Curve b is the curve after the signal is amplified. It can be a 1st order signal, or a 2nd order or 3rd order signal. It is selected according to the amplification factor and the amplitude of curve b. The 1st order signal is selected according to the size of the signal. When the aramid rope core characteristics are obvious, the 1st order signal or the 2nd order signal can be selected. Generally, when the amplification factor is 20 times, the 1st order signal is selected. When the amplification factor is 100 times, the signal is selected as the 2nd order signal. When amplifying the signal, the previous line of data is first processed, and the 1st order signal is at the zero point of the oscilloscope through offset, and then the signal is changed in multiples, such as 10 times, 20 times amplification, etc., so that the amplitude of this line of curve is amplified. When scanning the next line, the signal will be amplified as a whole.

[0029] When the perturbation signal is selected as the first-order signal, the operating frequency of its wave source selection can be reduced by half when the fundamental wave is selected. The selection of the wave source frequency for the aramid rope core transmission belt is related to the defect range. For example, the maximum length of the minimum defect area to be identified is L, and the resolution of the wave source must be less than L to identify it. The resolution of the wave source is determined by half the wavelength (λ / 2). Only when λ / 2≤L can the defect be identified. When the first-order signal is used, the resolution is the wavelength corresponding to the second harmonic 2f, which corresponds to the wavelength of the selected wave source multiplied by 2. Then the wavelength of the wave source is selected as λ≤L.

[0030] Taking the maximum length L of the smallest defect to be identified as 10mm as an example, in order to identify the internal defects of the aramid rope core transmission belt, the wavelength of the wave source must be greater than 10mm, that is, the frequency of the wave source is 30GHz. If the maximum length L of the smallest defect to be identified is 15mm, the wavelength of the wave source is 15mm, and the frequency of the wave source is 20GHz.

[0031] When the perturbation signal is selected as a second-order signal, the operating frequency of its wave source selection can be reduced to 1 / 4 when the fundamental wave is selected. The selection of the wave source frequency for the aramid rope core transmission belt is related to the defect range. For example, if the maximum length of the minimum defect area is L, the wavelength of the wave source can be selected as λ≤2L.

[0032] Taking the identification of the minimum defect with a maximum length L of 10 mm as an example, in order to identify the internal defects of the aramid rope core transmission belt, the wavelength of this wave source must be greater than 20 mm, that is, the frequency of the wave source is 15 GHz.

[0033] Internal imaging of aramid rope core transmission belt: Use the wave source power to pass through the aramid rope core transmission belt to perform internal imaging. The structure is as follows Figure 1 When imaging internally, the micro-perturbation characteristics of electromagnetic waves are used to distinguish the aramid cores with straight longitude and latitude, as shown in Figure 2. Figure 4 As shown by the middle curve b. The straight-warp and straight-weft aramid rope core has a mesh structure in its internal structure, and the signal between the grids on the latitude line or longitude line is different. By using the different characteristics of the signal between the grids, combined with a row of multi-point scanning or a row of multi-wave sources, a cross-sectional signal of the transmission belt is imaged. Combined with the longitudinal movement of the transmission belt, a flat imaging picture of the interior of the aramid rope core can be formed.

[0034] Image recognition based on aramid internal defects: The internal defects of aramid rope core transmission belts are mainly the misalignment of joints, which will be reflected in the loss of a certain line of originally uniformly distributed signals during signal processing, such as Figure 5 As shown in line b, the originally upward peak signal becomes flat at the trough, which is caused by the missing part of the aramid rope core in the cross-section observation. After multiple line scans, the internal imaging diagram will show the defect information, such as Figure 6As shown, a is the longitude and latitude imaging diagram, b is the defective part diagram of the aramid rope core, and c is the signal schematic diagram of the missing part of the second-order or third-order aramid rope core, which can directly identify the internal defect information.

[0035] The invention discloses a method for detecting internal defects of an aramid rope core transmission belt with a straight warp and straight weft structure. The method uses a low-power electromagnetic wave source without high voltage to perform imaging, has no radiation to the operator, is safe and environmentally friendly, and has no high voltage reduction and explosion-proof measures, and is particularly suitable for use in a mine environment.

Claims

1. A method for detecting internal defects of an aramid rope core transmission belt having a straight warp and weft structure, characterized in that: The method comprises: selecting the power of the electromagnetic wave source, selecting the order of electromagnetic wave micro-disturbance, determining the wave source frequency, imaging the interior of the aramid rope core transmission belt, imaging and identifying the internal defects of the aramid rope core, and realizing non-destructive imaging of the internal defects of the aramid rope core.

2. The method for detecting internal defects of a straight-warp and straight-weft structured aramid rope core transmission belt according to claim 1, characterized in that: The selection of electromagnetic wave source power is related to the thickness of the aramid rope core transmission belt. When the thickness of the aramid rope core transmission belt is less than 10mm, the wave source power is selected within 0.2 watts; when the thickness of the aramid rope core transmission belt is less than 20mm, the wave source power can be selected within 0.5 watts; when the thickness of the aramid rope core transmission belt is more than 20mm, the wave source power is selected within 1 watt; the wave source power can penetrate the transmission belt for internal imaging.

3. The method for detecting internal defects of a straight-warp and straight-weft structured aramid rope core transmission belt according to claim 1, characterized in that: Selecting the order of electromagnetic wave micro-disturbance includes: the internal signal of the aramid rope core is related to the electromagnetic wave micro-disturbance, the electromagnetic wave micro-disturbance is the first-order signal or the second-order signal in the single detection signal passing through the aramid rope core transmission belt, the middle maximum peak of the single detection signal passing through the aramid rope core transmission belt is the fundamental wave, the signal fluctuates and decays toward both ends, representing the second and third harmonics respectively, and after Fourier transformation, the order is used to represent the first-order signal or the second-order signal; Determining the wave source frequency includes: when the maximum length of the minimum defect area to be identified is L, when a first-order signal is selected, the wave source frequency selection must satisfy a wavelength of λ≤L; when a second-order signal is selected, the wave source frequency selection must satisfy a wavelength of λ≤2L.

4. The method for detecting internal defects of a straight-warp and straight-weft structured aramid rope core transmission belt according to claim 3, characterized in that: The micro-disturbance characteristics of electromagnetic waves are used to distinguish the straight longitude and straight latitude aramid cores. The internal structure of the straight longitude and straight latitude aramid rope core is a mesh structure. The signal on the latitude line or longitude line is different from the signal between the grids. Using the difference in signals, a cross-sectional signal of the aramid rope core transmission belt is imaged, and then combined with the longitudinal movement of the aramid rope core transmission belt, a flat image of the interior of the aramid rope core is formed.

5. The method for detecting internal defects of a straight-warp and straight-weft structured aramid rope core transmission belt according to claim 1, characterized in that: When the internal defect of the aramid rope core transmission belt is the misalignment at the joint, it will be reflected in the missing of a certain line of originally evenly distributed signals during signal processing, and the signal at the original peak will become a trough. After multiple lines of scanning, the internal imaging diagram will show the defect information.

6. The method for detecting internal defects of a straight-warp and straight-weft structured aramid rope core transmission belt according to claim 3, characterized in that: When testing aramid rope core transmission belts, a combination of signal amplification and effective order selection is adopted. When the amplification factor is 20 times, the 1st order signal is selected; when the amplification factor is 100 times, the 2nd order signal is selected; when amplifying the signal, the previous line of data is first processed, and the 1st order signal is placed at the zero point of the oscilloscope through bias, and then the signal is multipled to amplify the amplitude of this line of curves. When scanning the next line, the signal will be amplified as a whole.

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