CN119146912B - Gear crack internal and external depth detection method and system based on gear coil induction thermal response - Google Patents
Gear crack internal and external depth detection method and system based on gear coil induction thermal response Download PDFInfo
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- G—PHYSICS
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- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
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- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/0002—Inspection of images, e.g. flaw detection
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- G06T2207/00—Indexing scheme for image analysis or image enhancement
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Abstract
The invention provides a gear crack inner and outer depth detection method and system based on simulated tooth coil induction thermal response, and relates to the field of image detection. The method adopts the designed tooth-like coil to carry out electromagnetic excitation on the gear groove, and forms relatively uniform induced current with curved surface shape characteristics on the surface and the near surface of the gear. Eddy currents produce motion in the gear, and when the depth of a defect changes, the motion of the current changes accordingly, so that the temperature around the defect forms a temperature difference with other areas. The more obvious the thermal cloud image is as the depth of the defect increases, the higher the proportional matching between the temperature characteristic points of the cloud image in the middle of the defect and the depth is. For cracks in gears, the positions and the forms of defects can be obtained when the embedded depth is shallow, and the embedded depth and the tooth surface temperature of the defects are quantitatively related in a certain range. The invention discloses an internal connection between the induced eddy current thermal response and internal and external cracks of a gear, and constructs a characteristic characterization method and parameters of crack depth, which plays an important role in the field of defect detection of industrial parts.
Description
Technical Field
The invention relates to the field of image detection, in particular to a method and a system for detecting the inner and outer depths of gear cracks of an imitated tooth coil induction thermal response.
Background
Gears are indispensable mechanical elements in the modern industry, and play a vital role in various fields of industry, traffic, energy, aerospace and the like. The importance of the gears is represented by the core functions of the gears in the aspects of power transmission, speed control, torque conversion, accurate motion control, system integration and the like. In general, in the running or production and manufacturing process of gears, defects such as cracks and abrasion may occur due to factors such as fatigue, corrosion and abrasion. These defects are not timely discovered and handled and may lead to failure of the gear by breakage, which may have serious consequences. For example, if a gear in a case of an aeroengine fails, the aeroengine can be directly caused to stop running, so that serious hidden danger is caused for life safety or certain economic loss is caused for enterprises.
The gear is subjected to nondestructive testing regularly, so that defects such as cracks, abrasion and the like in the gear or on the surface of the gear can be found in time, corresponding measures can be taken in time to avoid accidents, and the gear can be subjected to the nondestructive testing regularly, so that the safety of the gear can be improved, the service life of the gear can be prolonged, the product quality can be improved, the economic loss can be reduced and the like. The existing method mainly comprises three types of ultrasonic nondestructive detection, electromagnetic eddy current detection and magnetic powder detection aiming at nondestructive detection of gears.
Ultrasonic nondestructive detection is to realize detection of defects by transmitting ultrasonic waves in a conductor material through an acoustic coupling medium, and the method can effectively detect internal defects of gears, but the method needs to smear the coupling medium on the surface in advance during detection and cannot effectively detect the defects of tooth surfaces.
The basic principle of electromagnetic eddy current detection is based on faraday electromagnetic induction principle, and the existence of defect is judged by impedance change of a magnetic field or a coil. The method has the advantages of higher sensitivity, non-contact and the like, but cannot effectively judge the depth of the gear defect and the near-surface defect.
The magnetic powder detection is a nondestructive detection technology for detecting the surface and near-surface defects of the ferromagnetic material, and has the main advantages of being easy to master, visual, low in cost and the like, and capable of effectively detecting the surface defects. However, the defects are obvious, the magnetic powder or the magnetic suspension is required to be smeared during detection, certain requirements are met on the directional strength of the magnetic field, and the experience of operators is depended.
Disclosure of Invention
The present disclosure provides a method for detecting the depth of cracks on the inner and outer surfaces of a gear in which a tooth coil is simulated to electromagnetically excite and thermally respond to the problems.
To solve at least one of the above technical problems, the present disclosure proposes a gear crack internal and external depth detection method of an imitated tooth coil induction thermal response, including:
Electromagnetic excitation is carried out on the gear through the designed tooth-shaped coil, induced current is formed on the surface and the near surface of the gear, and then temperature detection is carried out to obtain a thermal cloud picture;
After judging the internal and external cracks according to the thermal cloud image, detecting the hidden depth of the internal cracks if the internal cracks are the internal cracks, and detecting the hidden depth of the external cracks if the internal cracks are the external cracks;
taking cloud picture temperature characteristic points in the middle of the defect as main judgment basis and taking other cloud picture temperature characteristic points as auxiliary judgment, so as to realize the detection of the depth of the external crack;
And detecting the hidden depth of the internal crack through the quantitative relation between the hidden depth of the defect and the temperature of the tooth surface in a certain range.
Further, the tooth coil structure comprises:
The simulated tooth coil is an excitation coil which is formed by a plurality of sections of circular arcs which are coaxial with the curved surfaces of all parts of the gear groove and are similar to a triangle, the radius of the circular arc at the top of the simulated tooth coil is 47mm, the radius of the circular arc at the left and right sides is 18mm, the radius of the circular arc at the bottom of the simulated tooth coil is 4mm, the upper and lower heights of the simulated tooth coil are 25mm, the thickness of the simulated tooth coil is 12mm, the outer diameter of a coil wire is 1.8mm, the inner diameter of the coil wire is 0.8mm, the coil wire is made of copper, the number of turns is 5, the simulated tooth coil is placed in the gear groove in the detection process, and the two side surfaces and the bottom surface of the simulated tooth coil are 2mm away from the two side surfaces and the bottom surface of the gear groove.
Further, electromagnetic excitation of the gear by the designed simulated tooth coil includes:
The coil is applied with a sinusoidal alternating current signal, the oscillation frequency is 50kHz at maximum, the current of the coil is 2A when the coil is in idle load, the current is 6A when the coil is placed in a gear groove for heating, and the maximum heating power of an excitation device is 120W.
Further, the excitation device comprises a capacitor, an inductor, a MOSFET, a diode, a voltage stabilizing diode, a pull-down resistor and a current limiting resistor, and current is directly loaded on the grid electrode of the MOSFET through the current limiting resistor.
Further, the tooth-like coil structure further comprises a tooth-like coil auxiliary device:
The input voltage of the induction heating device is limited to be DC 5-12V, the power supply is converted into DC 5-12V by using auxiliary equipment, the tooth-shaped coil imitating auxiliary device consists of a transformer, a diode, a voltage regulator and a voltage stabilizer, and meanwhile, the induction heating device also comprises a self-priming pump with the power supply of DC5V, wherein the maximum flow rate of the self-priming pump is 1.6L/min, and the maximum lift is 1.5m.
Further, taking cloud image temperature characteristic points in the middle of the defect as a main judgment basis and other cloud image temperature characteristic points as auxiliary judgment, and detecting the depth of the external crack, wherein the method comprises the following steps:
And probe points are respectively arranged in the areas at the two ends of the defect and the middle parts of the two sides of the defect.
Further, the detection of the external crack depth is realized by extracting cloud image temperature characteristic points at different depths, and then adopting fourth-order polynomial fitting to finally obtain defect depth and temperature expressions at different probe points:
The probe point 1 and the probe point 4 are positioned on the same side, the probe point 2 and the probe point 3 are positioned on the same side, are respectively arranged at the corner points of the defects,
The probe point 5 and the probe point 6 are respectively positioned at the position of 0.5mm from the defect edge in the middle area of the defect,
Determination coefficient of probe point 1The fitting formula is as follows:
determination coefficient of probe point 2 The fitting formula is as follows:
determination coefficient of probe point 3 The fitting formula is as follows:
determination coefficient of probe point 4 The fitting formula is as follows:
Determination coefficient of probe point 5 The fitting formula is as follows:
Determination coefficient of probe point 6 The fitting formula is as follows:
the probe point 5 and the probe point 6 are respectively positioned at the position 0.5mm away from the edge of the defect in the middle area of the defect, wherein x is the depth of the defect, and y is the temperature characteristic point of the cloud image of the defect;
The temperature data of the probe point 5 is used as a main judgment basis, and the data of the rest positions are used as auxiliary.
Further, the method is characterized in that the detection of the hidden depth of the internal crack is realized by the quantitative relation between the hidden depth of the defect and the temperature of the tooth surface in a certain range, and the method comprises the following steps:
Through the thermal cloud diagram, a probe point is arranged at the middle position of the highest temperature region, a defect 1 is arranged at the middle position of one side tooth surface of the gear groove, and a defect 2 is arranged at the middle position of the tooth bottom.
Further, the detection of the hidden depth of the internal crack is realized by the quantitative relation between the hidden depth of the defect and the temperature of the tooth surface in a certain range, which comprises the following steps:
Determination coefficient of probe point at defect 1 The fitting formula is as follows:
determination coefficient of probe point at defect 2 The fitting formula is as follows:
wherein h is the depth of the buried defect, and y is the temperature characteristic point of the cloud picture.
In addition, the invention also provides a gear crack internal and external depth detection system imitating tooth coil induction thermal response, which comprises:
The excitation module is used for carrying out electromagnetic excitation on the gear through the designed tooth-shaped coil, forming induced currents on the surface and the near surface of the gear, and then carrying out temperature detection to obtain a thermal cloud picture;
The excitation module is used for detecting the hidden depth of the internal crack if the internal crack is the internal crack after judging the internal crack and the external crack according to the thermal cloud picture;
the external crack depth detection module takes cloud image temperature characteristic points in the middle of the defect as a main judgment basis and takes other cloud image temperature characteristic points as auxiliary judgment to realize detection of external crack depth;
and the internal crack hiding depth detection module is used for realizing the detection of the internal crack hiding depth through the quantitative relation between the defect hiding depth and the tooth surface temperature in a certain range.
The technical scheme has the following advantages or beneficial effects:
(1) According to the exciting coil for gear detection designed according to the tooth groove structure, the coverage area of detection, such as tooth surfaces on two sides of a single tooth groove, tooth bottoms and tooth root areas, is enlarged, and the effective current field area and density are greatly increased. According to the coil structure, the thermal cloud image display can be carried out only after single excitation, and detection of different positions of the tooth surface is not needed to be carried out by moving the coil for multiple times. In addition, relatively uniform induced currents with curved surface shape characteristics are formed on the surface and the near surface of the gear, so that a heat map with obvious distinguishing effect characteristics is formed;
(2) The method is not limited by experience of operators, accurate quantitative detection of crack depth can be realized, and the detection accuracy of combining the temperature cloud picture with the probe point fixed point temperature is higher, so that intelligent upgrading is facilitated.
(3) The method reveals the association of the defects in the gear and the temperature response cloud picture, and provides a convenient and fast visualization method for detecting the internal cracks. Meanwhile, the deep law of cloud image temperature characteristic points and defect hiding depth at different positions on the gear surface is revealed, the limit position of the hiding depth is quantified, and a reference is provided for timely finding and predicting hidden faults.
(4) The method is non-contact detection, does not need to be in direct contact with the detected gear, can realize comprehensive detection of defects of all positions of the disposable gear, and avoids adverse damage to the gear transmission part. In addition, the requirement of fault monitoring is completely met in measurement accuracy without expensive detection equipment with a complex structure.
The invention starts from the essence of multi-physical field coupling and combined action, further deeply understands the internal connection between the surface temperature of the gear and the gear defect, and discovers more effective characteristic characterization methods and parameters for describing the gear defect.
Drawings
The invention and its features, aspects and advantages will become more apparent from the detailed description of non-limiting embodiments with reference to the following drawings. Like numbers refer to like parts throughout. The drawings are not intended to be drawn to scale, emphasis instead being placed upon illustrating the principles of the invention.
FIG. 1 is a flow chart of a method for detecting the internal and external depths of gear cracks according to an embodiment of the induction thermal response of a tooth-like coil;
FIG. 2 is a block diagram of a gear crack internal and external depth detection system with simulated tooth coil induction thermal response according to a third embodiment;
FIG. 3 is a schematic diagram of an eddy current sensing gear defect depth detection according to a fourth embodiment;
FIG. 4 is a diagram showing a current flow distribution of the exciting coil structure according to the fourth embodiment;
FIG. 5 is a graph showing the temperature response of a crack defect on the surface of a gear according to the fourth embodiment, wherein the crack defect is observed by comparing a temperature response cloud image with probe points arranged at the defect;
FIG. 6 is a graph showing the temperature response of the gear surface according to the fourth embodiment;
FIG. 7 is a temperature cloud chart of gear defects at different depths at 0.15s according to the fourth embodiment;
FIG. 8 is probe point fitting data for different depth defects according to the fourth embodiment;
FIG. 9 is a temperature cloud image at different burial depths at gear defect 1 (tooth face crack) according to example four;
FIG. 10 is a simulation graph of the different burial depths at defect 2 (tooth bottom crack) and its surface temperature response according to example four;
FIG. 11 is a graph showing temperature characteristic point fitting curves of cloud patterns with different burial depths according to the fourth embodiment.
Detailed Description
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present application.
It will be understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, steps, operations, devices, components, and/or groups thereof.
The terms "first," "second," "third," and the like, as used herein, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The following description of the technical solutions according to the embodiments of the present invention refers to the accompanying drawings, which are included to illustrate only some embodiments of the invention, and not all embodiments. Accordingly, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by a person skilled in the art without making any inventive effort, are intended to fall within the scope of the present invention.
Embodiment one:
The embodiment provides a gear crack internal and external depth detection method based on the simulated tooth coil induction thermal response shown in fig. 1, which comprises the following steps:
Electromagnetic excitation is carried out on the gear through the designed tooth-shaped coil, induced current is formed on the surface and the near surface of the gear, and then temperature detection is carried out to obtain a thermal cloud picture;
After judging the internal and external cracks according to the thermal cloud image, detecting the hidden depth of the internal cracks if the internal cracks are the internal cracks, and detecting the hidden depth of the external cracks if the internal cracks are the external cracks;
taking cloud picture temperature characteristic points in the middle of the defect as main judgment basis and taking other cloud picture temperature characteristic points as auxiliary judgment, so as to realize the detection of the depth of the external crack;
And detecting the hidden depth of the internal crack through the quantitative relation between the hidden depth of the defect and the temperature of the tooth surface in a certain range.
According to the exciting coil for gear detection designed according to the tooth groove structure, the coverage area of detection, such as the tooth surfaces on two sides of a single tooth groove, the tooth bottom and the tooth root area, is enlarged, and the effective current field area and density are greatly increased. According to the coil structure, the thermal cloud image display can be carried out only after single excitation, and detection of different positions of the tooth surface is not needed to be carried out by moving the coil for multiple times. In addition, relatively uniform induced currents with curved surface shape characteristics are formed on the surface and the near surface of the gear, so that a heat map with obvious distinguishing effect characteristics is formed;
The embodiment provides visualization and quantitative detection of depth of the gear surface crack, is not limited by experience of operators, can realize accurate quantitative detection of crack depth, has higher detection precision of combining a temperature cloud picture with a probe point fixed point temperature, and is beneficial to realizing intelligent upgrading.
The embodiment provides visualization and quantitative detection of hidden depth of the internal cracks of the gear, and the correlation of the internal defects of the gear and the temperature response cloud picture provides a convenient and fast visualization method for the detection of the internal cracks. Meanwhile, the deep law of cloud image temperature characteristic points and defect hiding depth at different positions on the gear surface is revealed, the limit position of the hiding depth is quantified, and a reference is provided for timely finding and predicting hidden faults.
The embodiment is non-contact detection, does not need to be in direct contact with a detected gear, can realize comprehensive detection of all position defects of the disposable gear, and avoids adverse damage to a gear transmission piece. In addition, the requirement of fault monitoring is completely met in measurement accuracy without expensive detection equipment with a complex structure.
The embodiment starts from the essence of multi-physical field coupling and combined action, further deeply understands the internal connection between the surface temperature of the gear and the gear defect, and discovers more effective characterization methods and parameters for describing the gear defect.
Embodiment two:
The present embodiment further discloses, based on the first embodiment:
Further, the tooth coil structure comprises:
The simulated tooth coil is an excitation coil which is formed by a plurality of sections of circular arcs which are coaxial with the curved surfaces of all parts of the gear groove and are similar to a triangle, the radius of the circular arc at the top of the simulated tooth coil is 47mm, the radius of the circular arc at the left and right sides is 18mm, the radius of the circular arc at the bottom of the simulated tooth coil is 4mm, the upper and lower heights of the simulated tooth coil are 25mm, the thickness of the simulated tooth coil is 12mm, the outer diameter of a coil wire is 1.8mm, the inner diameter of the coil wire is 0.8mm, the coil wire is made of copper, the number of turns is 5, the simulated tooth coil is placed in the gear groove in the detection process, and the two side surfaces and the bottom surface of the simulated tooth coil are 2mm away from the two side surfaces and the bottom surface of the gear groove.
Further, electromagnetic excitation of the gear by the designed simulated tooth coil includes:
The coil is applied with a sinusoidal alternating current signal, the oscillation frequency is 50kHz at maximum, the current of the coil is 2A when the coil is in idle load, the current is 6A when the coil is placed in a gear groove for heating, and the maximum heating power of an excitation device is 120W.
Further, the excitation device comprises a capacitor, an inductor, a MOSFET, a diode, a voltage stabilizing diode, a pull-down resistor and a current limiting resistor, and current is directly loaded on the grid electrode of the MOSFET through the current limiting resistor.
Further, the tooth-like coil structure further comprises a tooth-like coil auxiliary device:
The input voltage of the induction heating device is limited to be DC 5-12V, the power supply is converted into DC 5-12V by using auxiliary equipment, the tooth-shaped coil imitating auxiliary device consists of a transformer, a diode, a voltage regulator and a voltage stabilizer, and meanwhile, the induction heating device also comprises a self-priming pump with the power supply of DC5V, wherein the maximum flow rate of the self-priming pump is 1.6L/min, and the maximum lift is 1.5m.
Further, taking cloud image temperature characteristic points in the middle of the defect as a main judgment basis and other cloud image temperature characteristic points as auxiliary judgment, and detecting the depth of the external crack, wherein the method comprises the following steps:
And probe points are respectively arranged in the areas at the two ends of the defect and the middle parts of the two sides of the defect.
Further, the detection of the external crack depth is realized by extracting cloud image temperature characteristic points at different depths, and then adopting fourth-order polynomial fitting to finally obtain defect depth and temperature expressions at different probe points:
The probe point 1 and the probe point 4 are positioned on the same side, the probe point 2 and the probe point 3 are positioned on the same side, are respectively arranged at the corner points of the defects,
The probe point 5 and the probe point 6 are respectively positioned at the position of 0.5mm from the defect edge in the middle area of the defect,
Determination coefficient of probe point 1The fitting formula is as follows:
determination coefficient of probe point 2 The fitting formula is as follows:
determination coefficient of probe point 3 The fitting formula is as follows:
determination coefficient of probe point 4 The fitting formula is as follows:
Determination coefficient of probe point 5 The fitting formula is as follows:
Determination coefficient of probe point 6 The fitting formula is as follows:
the probe point 5 and the probe point 6 are respectively positioned at the position 0.5mm away from the edge of the defect in the middle area of the defect, wherein x is the depth of the defect, and y is the temperature characteristic point of the cloud image of the defect;
The temperature data of the probe point 5 is used as a main judgment basis, and the data of the rest positions are used as auxiliary.
Further, the method is characterized in that the detection of the hidden depth of the internal crack is realized by the quantitative relation between the hidden depth of the defect and the temperature of the tooth surface in a certain range, and the method comprises the following steps:
Through the thermal cloud diagram, a probe point is arranged at the middle position of the highest temperature region, a defect 1 is arranged at the middle position of one side tooth surface of the gear groove, and a defect 2 is arranged at the middle position of the tooth bottom.
Further, the detection of the hidden depth of the internal crack is realized by the quantitative relation between the hidden depth of the defect and the temperature of the tooth surface in a certain range, which comprises the following steps:
Determination coefficient of probe point at defect 1 The fitting formula is as follows:
determination coefficient of probe point at defect 2 The fitting formula is as follows:
wherein h is the depth of the buried defect, and y is the temperature characteristic point of the cloud picture.
According to the exciting coil for gear detection designed according to the tooth groove structure, the coverage area of detection, such as the tooth surfaces on two sides of a single tooth groove, the tooth bottom and the tooth root area, is enlarged, and the effective current field area and density are greatly increased. According to the coil structure, the thermal cloud image display can be carried out only after single excitation, and detection of different positions of the tooth surface is not needed to be carried out by moving the coil for multiple times. In addition, relatively uniform induced currents with curved surface shape characteristics are formed on the surface and the near surface of the gear, so that a heat map with obvious distinguishing effect characteristics is formed;
The embodiment provides visualization and quantitative detection of depth of the gear surface crack, is not limited by experience of operators, can realize accurate quantitative detection of crack depth, has higher detection precision of combining a temperature cloud picture with a probe point fixed point temperature, and is beneficial to realizing intelligent upgrading.
The embodiment provides visualization and quantitative detection of hidden depth of the internal cracks of the gear, and the correlation of the internal defects of the gear and the temperature response cloud picture provides a convenient and fast visualization method for the detection of the internal cracks. Meanwhile, the deep law of cloud image temperature characteristic points and defect hiding depth at different positions on the gear surface is revealed, the limit position of the hiding depth is quantified, and a reference is provided for timely finding and predicting hidden faults.
The embodiment is non-contact detection, does not need to be in direct contact with a detected gear, can realize comprehensive detection of all position defects of the disposable gear, and avoids adverse damage to a gear transmission piece. In addition, the requirement of fault monitoring is completely met in measurement accuracy without expensive detection equipment with a complex structure.
The embodiment starts from the essence of multi-physical field coupling and combined action, further deeply understands the internal connection between the surface temperature of the gear and the gear defect, and discovers more effective characterization methods and parameters for describing the gear defect.
Embodiment III:
The embodiment provides a gear crack internal and external depth detection system imitating tooth coil induction thermal response as shown in fig. 2, comprising:
The excitation module is used for carrying out electromagnetic excitation on the gear through the designed tooth-shaped coil, forming induced currents on the surface and the near surface of the gear, and then carrying out temperature detection to obtain a thermal cloud picture;
The excitation module is used for detecting the hidden depth of the internal crack if the internal crack is the internal crack after judging the internal crack and the external crack according to the thermal cloud picture;
the external crack depth detection module takes cloud image temperature characteristic points in the middle of the defect as a main judgment basis and takes other cloud image temperature characteristic points as auxiliary judgment to realize detection of external crack depth;
and the internal crack hiding depth detection module is used for realizing the detection of the internal crack hiding depth through the quantitative relation between the defect hiding depth and the tooth surface temperature in a certain range.
According to the exciting coil for gear detection designed according to the tooth groove structure, the coverage area of detection, such as the tooth surfaces on two sides of a single tooth groove, the tooth bottom and the tooth root area, is enlarged, and the effective current field area and density are greatly increased. According to the coil structure, the thermal cloud image display can be carried out only after single excitation, and detection of different positions of the tooth surface is not needed to be carried out by moving the coil for multiple times. In addition, relatively uniform induced currents with curved surface shape characteristics are formed on the surface and the near surface of the gear, so that a heat map with obvious distinguishing effect characteristics is formed;
The embodiment provides visualization and quantitative detection of depth of the gear surface crack, is not limited by experience of operators, can realize accurate quantitative detection of crack depth, has higher detection precision of combining a temperature cloud picture with a probe point fixed point temperature, and is beneficial to realizing intelligent upgrading.
The embodiment provides visualization and quantitative detection of hidden depth of the internal cracks of the gear, and the correlation of the internal defects of the gear and the temperature response cloud picture provides a convenient and fast visualization method for the detection of the internal cracks. Meanwhile, the deep law of cloud image temperature characteristic points and defect hiding depth at different positions on the gear surface is revealed, the limit position of the hiding depth is quantified, and a reference is provided for timely finding and predicting hidden faults.
The embodiment is non-contact detection, does not need to be in direct contact with a detected gear, can realize comprehensive detection of all position defects of the disposable gear, and avoids adverse damage to a gear transmission piece. In addition, the requirement of fault monitoring is completely met in measurement accuracy without expensive detection equipment with a complex structure.
The embodiment starts from the essence of multi-physical field coupling and combined action, further deeply understands the internal connection between the surface temperature of the gear and the gear defect, and discovers more effective characterization methods and parameters for describing the gear defect.
Embodiment four:
The embodiment proposes that other physical quantities such as solid heat transfer and the like caused by electromagnetic effect are coupled together based on an eddy current induction thermal response detection technology, and as shown in an eddy current induction gear defect depth detection schematic diagram shown in fig. 3, an exciting coil which is fed with high-frequency alternating current is close to a gear during detection, induced current, flow and hysteresis induction heat are generated on the surface and the inside of a material, the temperature distribution condition of the gear is measured by using a thermal cloud picture, when the surface of a detected material has defects, cracks, surface defect depth change and the like, the distribution condition of the induced current is changed, and different density distribution of the induced current forms various temperature distribution different areas near the defects. And judging the position, the size, the shape parameters and the like of the defect through temperature comparison of the non-defect area and the defect area on the surface of the gear.
(1) Structural design of exciting coil probe
The coil structure form is critical to the detection result, the parameters reflected by different coil structure forms are different, and the reasonable design of the exciting coil is critical to the response of the researched parameters. And comparing different coil structures, comprehensively considering the response conditions, detection efficiency and the like of the research parameters, and finally determining the structural form of the exciting coil. FIG. 4 is a diagram showing the structure of the excitation coil and the current flow direction distribution;
And (3) through the modeling of the coil, analyzing and observing whether the temperature response condition of the tooth surface meets the required requirement. Coil excitation current 5A, frequency 15kHz, excitation time 0.15s. The materials were selected from copper (exciting coil), iron (gear) and air (air domain) in table 1.
FIG. 5 is a graph of crack defects on a gear surface, and is used to observe the temperature response at a defect by comparing a temperature response cloud with probe points disposed at the defect. FIG. 6 is a graph showing the temperature response of the gear surface under excitation of the simulated tooth coil of FIG. 4.
The optimal design of the exciting coil is mainly characterized in that 1) the position and the shape of the defect can be well reflected by the coil structure, a detection blind area cannot exist in the coil structure, so that the comprehensiveness of tooth surface detection can be influenced, and 2) the operability and the convenience of actual detection are considered, and the function condition of automatic detection is realized. If only one area is detected during detection, when other areas are to be detected, the coil needs to be moved, the detection efficiency is greatly reduced, 3) the manufacturing difficulty of the coil structure cannot be too complex, 4) the temperature distribution at the defect has obvious advantages, some characteristic information of the defect can be well reflected, and the temperature change at the defect can meet the resolution of the existing equipment.
By comparing the temperature distribution cloud of different forms of coil excitation, it can be seen that the end result presented is greatly different. By combining the above factors, the tooth-like coil structure has a comprehensive coverage area for the tooth surface, and the temperature cloud image of the excitation response of the tooth-like coil structure can show that the temperature distribution change of the defect is obvious, and the parameters such as the position, the shape, the size and the like of the defect can be well represented. The temperature change amplitude at the defect can be obvious through the change of the cloud picture temperature characteristic points at the defect, and the shape and the position characteristics of the defects of each part of the gear are fully and thoroughly displayed.
(2) Detection of crack depth on gear surface
To investigate the effect of defect depth on tooth surface temperature, the effect of defect depth on temperature was analyzed by extracting the final temperature response of each excitation of the defect per change by increasing the initial defect depth from 4.3 mm. Fig. 7 is a cloud chart of the temperature of the gear defect at the moment of 0.15s, wherein cloud chart temperature characteristic points are respectively arranged at the defect corners and the middle positions.
As can be seen from the temperature response cloud of different defects, the color of the temperature at both ends of the defect gradually deepens after the depth of the defect increases, that is, the temperature at both ends of the defect gradually increases, and the temperature at the middle area of the defect, that is, the temperature at the position area of the probe point 5 and the probe point 6 gradually decreases with the increase of the depth. In order to verify the found situation, the temperatures at the probe points 1-6 are extracted under different defect depths, and the extracted temperature data under different depths are fitted. Through the fitted curve, the change trend of the probe point can be intuitively seen, namely, the probe point 1, the probe point 2, the probe point 3 and the probe point 4 with the defect increase of depth respectively show obvious temperature rising trend, and the probe point 5 and the probe point 6 show obvious descending trend. And its temperature response starts to stabilize with increasing depth, such as when the defect depth is around 3.7 mm.
In summary, it is found that, as the depth of the defect increases, the current flowing in the defect is gradually increased until the depth reaches a certain level, and when the current starts to flow to both ends of the defect, the temperature at the defect tends to be stable, that is, the temperature does not increase continuously with the increase of the depth. That is, the defects found at the different positions above, the temperature of which starts to be smoothed after the depth of the defects increases to a certain stage.
Based on the above study analysis, quantitative analysis of defect depth was performed by temperature data. Fig. 8 shows fitting data of probe points with defects of different depths, and from the fitting data, the convergence of the probe points 5 and 6 is higher than that of other probe points, and by comparing the response conditions of the temperature characteristic points of the cloud image, the accuracy of conversion with depth by extracting the temperature data of the middle part is higher in the practical application condition. And the temperature change of the probe points 1-4 at a certain depth due to the influence of the current skin effect tends to be stable and not to show a direct proportion relation with the depth, so that the temperature data of the middle part of the defect in the actual detection process can judge the more accurate defect depth, and the cloud image temperature characteristic points at other points can be used as auxiliary judgment.
(3) Detection of hidden depth of crack in gear
Fig. 9 is a temperature cloud chart at different burial depths of a gear defect 1 (tooth surface crack), and it can be observed from fig. 9 that when a defect is generated in the gear, the defect also generates uneven temperature fields in the heating process, and the main reason for the change of the temperature fields is that the current flow direction of the defect is suddenly changed due to the existence of the defect, so that the change of joule heat is caused, and finally, the uneven temperature distribution of the tooth surface is reflected.
The temperature response cloud chart shows that the whole temperature is uniform and has no temperature mutation on the tooth surface of the non-defective gear, when one defect is buried at the position of 0.1-2 mm below the tooth surface, the temperature field distribution of the tooth surface can be clearly seen, the phenomenon of uneven temperature distribution of the tooth surface caused by the defect can be clearly seen, and the position and the shape of the defect can be clearly seen when the buried depth is shallow. But with increasing burial depth and the effect of current skin effect, the surface temperature distribution at the defect will no longer be apparent, i.e. 1.3mm burial depth and thereafter burial depth of fig. 9.
The right side of fig. 10 is a simulation graph of the different burial depths at defect 2 (tooth bottom crack) and their surface temperature response, and it can be seen that the overall trend is the same as that at defect 1. The position and shape of the defect can be observed through the temperature cloud picture, but the temperature cloud picture of the buried depth of the defect cannot be reflected, at the moment, because the buried depth of the defect is gradually increased, most of current is concentrated on the near surface due to the skin effect of the current, so that the closer the defect is to the surface, the larger the generated joule heat is, and the higher the surface temperature is. When the defect is far from the surface, the current density in the gear is smaller, so that the generated joule heat at the defect is smaller, and when the generated joule heat at the defect is smaller than that generated by the surface, the temperature cloud image of the surface can not clearly reflect the position and the shape of the defect.
FIG. 11 is a graph of cloud temperature characteristic point fitting curves of different burial depths, and the burial depths of defects can be seen to be different, and the tooth surface response temperature at the defect position can be changed. The depth of the buried defect is in direct proportion to the temperature of the tooth surface at the defect in a certain range. But the depth of burial also shows a smoother change at the defect in a certain range, and the temperature cloud image cannot show the existence of defects such as 1.3mm in fig. 9 and 1mm in fig. 10. At this time, the existence of defects cannot be judged through the temperature cloud pattern distribution condition of the tooth surface, so that quantitative analysis of the defects cannot be performed. However, for other temperature cloud patterns such as those shown in fig. 9 and 10, which can represent defects, quantitative analysis of the absence can be performed by collecting temperature data at the defects at the moment when the excitation is finished, and the fitting formula is used for quantitatively analyzing the burial depth of the defects.
Through the research and analysis, near-surface cracks generated by the gear due to heat treatment processes such as quenching, grinding and the like can be effectively detected and judged. The depth of the crack near the surface can be judged by combining the temperature response cloud image of the tooth surface and the temperature data of the defect, and the temperature cloud image of the crack near the surface is displayed more clearly and accurately. Although this method can detect near-surface defects, it is determined that the detection cannot have a large depth due to the skin effect of the current, but the method has high sensitivity for detecting near-surface defects, and can accurately determine the shape, position, and depth of the defects.
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