CN107345937B - Ultrasonic array in-situ detection method for surface defects of fan main shaft - Google Patents
Ultrasonic array in-situ detection method for surface defects of fan main shaft Download PDFInfo
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- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
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Abstract
The invention discloses an ultrasonic array in-situ detection method for surface defects of a main shaft of a fan. The piezoelectric array elements are arranged in a circular ring mode to form a piezoelectric sensor array which is fixed on the end face of a main shaft of the fan, and the sound beam in the diffusion angle of the piezoelectric array elements is utilized to realize the full coverage of the surface of the main shaft in the detection area of the main shaft of the fan; piezoelectric array elements in the piezoelectric sensor array are sequentially excited in an electronic scanning mode, so that ultrasonic waves are radiated to the surface of a main shaft in a detection area, ultrasonic echo signals are received, and the surface defects of the main shaft are positioned by identifying the characteristics of the echo signals. The invention detects the fan main shaft in an array mode, and realizes the in-situ detection of the surface defects of the fan main shaft in a non-manual scanning mode.
Description
Technical Field
The invention relates to an ultrasonic array in-situ detection method for surface defects of a main shaft of a fan, and belongs to the field of nondestructive detection.
Background
Wind energy has received increasing attention as a clean renewable energy source. With the large-scale popularization of wind power generation, the running states of fans and parts thereof are directly related to the safety and benefits of national production. The main shaft of the fan is in rotary motion, the main shaft is a main stressed part, and the situations of fatigue defects and abrasion and corrosion caused by long-time work are inevitable. Thus, the safety detection of the structure not only helps to prevent the occurrence of safety accidents, but also can avoid unnecessary economic loss.
The main shaft of the fan is fixed between the hub bin and the gear box through a bearing and is installed on the tower together. After the fan is installed, the fan is difficult to enter the position of the main shaft again for defect detection; in addition, the main shaft is installed in a hub and a shaft sleeve (or a bearing and the like), and the defects generated at the contact part can not be directly detected in a contact mode. If the main shaft of the fan needs to be detected, at present, only in a fan shutdown state, a detector climbs the tower frame, enters the fan hub bin, scans the end face of the main shaft by using the longitudinal wave probe, or detaches the main shaft from the fan for detection. However, once the installation of the fan on the tower is completed, the shutdown or the disassembly of the fan is almost difficult to realize, the time and the labor are consumed, and the detection cost is very huge. Therefore, the online in-situ detection of the main shaft of the current fan, particularly a large fan, cannot be well implemented. In order to ensure the safe use of the fan, guarantee the national production safety and minimize the potential safety hazard, it is necessary and urgent to research a defect detection method without the need of personnel to approach the main shaft of the fan.
The shafts of the fan are basically in a completely closed state, only the end faces can be exposed outside through simple disassembly, and the parts of the workpieces which are easy to have defects are generally far away from the end faces, mainly concentrated on press-fitting parts and have surface defects relative to the main shaft. To detect this, ultrasound is certainly the most suitable and effective detection method. The ultrasonic nondestructive detection technology has comprehensive advantages in determining the size, position, orientation, burial depth, property and other parameters of the internal defect compared with other nondestructive detection methods. The main performance is as follows: the detection capability is strong, and the method is harmless to human bodies, workpieces and the surrounding environment.
The research on wind power facility shaft detection is relatively less at home and abroad, and the research on locomotive axles is more. The axle of the locomotive is generally detected after being disassembled from the locomotive, and the detection is carried out by adopting a method of small-angle end surface incidence and oblique probe incidence on the axle body under the condition of no wheel withdrawal, and the detection method is nearly mature. Although the method is reasonable and feasible in design, the method cannot be directly applied to in-situ detection of the main shaft of the fan, and the main reasons are as follows: the in-situ detection requirement cannot be met, the detection piece needs to be detached from the parent body on the premise of detection, and the application specificity of the wind power industry cannot be met; the ultrasonic probe needs to be operated manually, and for the detection of the fan spindle in the tower with the height of hundreds of meters, the detection condition is harsh, and the practicability is not strong.
Disclosure of Invention
The invention provides an array detection method based on ultrasonic longitudinal waves, which adopts longitudinal wave piezoelectric array elements and can realize the detection of the defects of the circumferential surface of a main shaft through electronic scanning, thereby avoiding the complex process of manual scanning in the conventional detection process.
In order to achieve the above object, the technical solution adopted by the present invention is an ultrasonic array in-situ detection method for surface defects of a main shaft of a wind turbine, wherein a detection device for implementing the detection method comprises a computer 1, an ultrasonic excitation receiving device 2 and a multi-way gate 3, wherein the computer 1 is connected with the ultrasonic excitation receiving device 2, and the ultrasonic excitation receiving device 2 is connected with the multi-way gate 3, and the method comprises the following specific implementation steps:
according to the material of a fan main shaft and the size Q of a defect to be detected, selecting a piezoelectric array element with the central frequency f and the diameter d according to an ultrasonic detection principle, and calculating to obtain the size theta of a half diffusion angle of an acoustic beam of the piezoelectric array element, wherein the range of f is 1 MHz-5 MHz; half spread angle pass through
Calculating, wherein: c. CLThe longitudinal wave velocity of the main shaft material;
step two, calculating the section radius r of the piezoelectric array element acoustic beam in the detection area according to the half-diffusion angle theta of the piezoelectric array element acoustic beam calculated in the step one and the distance end face depth H of the area to be detected of the main shaft to be detected, and calculating the section radius r of the single piezoelectric array element (6) acoustic beam in the detection area by the method that r is H multiplied by tan theta;
step three, according to the coverage radius R of the piezoelectric array element acoustic beam obtained by calculation in the step two and the diameter D of the area needing to be detected of the detected main shaft, calculating the number N of the required piezoelectric array elements, rounding up if N is decimal, and rounding up if R is decimal, wherein R is vertical distance R between the center point of the piezoelectric array element and the center line of the main shaft:
step four, arranging the N piezoelectric array elements into a circular ring according to the vertical distance R between the center of the piezoelectric array element and the center line of the spindle and the number N of the piezoelectric array elements, wherein the vertical distance R is obtained by calculation in the step three, and the piezoelectric array elements are uniformly arranged on the end face of the spindle to form a piezoelectric sensor array by taking the center line of the spindle as a symmetry axis and taking the radius of R as a radius;
fixing the N piezoelectric array elements in the piezoelectric sensor array on the end face of the main shaft, numbering the piezoelectric array elements in sequence in a clock scale mode, and setting the zero time position as the piezoelectric array element with the number 1;
step six, respectively connecting the outgoing line of each piezoelectric array element in the piezoelectric sensor array to a channel interface corresponding to the multi-channel gate to complete the arrangement and the electrical cross-linking of the piezoelectric sensor array;
step seven, sending a detection instruction through a computer to control the ultrasonic excitation receiving equipment to enable the multi-channel gating device to gate each numbered piezoelectric array element in sequence for excitation and receive an echo signal of the piezoelectric array element;
step eight, the ultrasonic excitation receiving equipment collects the echo signals received each time and sends the echo signals to a computer, and the computer records the echo signals of each numbered piezoelectric array element;
and step nine, after the ultrasonic excitation receiving equipment completes the excitation, the receiving and the data transmission of the No. N piezoelectric array element, judging the defect position on a computer through the identification of the echo characteristics of each numbered piezoelectric array element, and completing the main shaft detection. The identification of the echo characteristics is judged according to the time difference between the echo and the bottom wave of the main shaft and the occurrence or non-occurrence of the time echo of each channel. The specific judgment method is as follows: the echo appearing before the bottom wave is determined as a suspicious defect echo, the suspicious echo appearing at the time of each numbered piezoelectric array element is a structure echo, and the suspicious echo appearing only in a certain number or the number adjacent to the certain number is determined as a defect echo;
step ten, determining the defect position, namely the channel number and the depth according to the number of the piezoelectric array element with the echo and the echo depth;
compared with the prior art, the invention has the beneficial effects.
1. The method realizes the detection of the surface defect of the main shaft on the end surface of the main shaft by utilizing the ultrasonic wave radiated by the piezoelectric sensor array, does not need to detach the main shaft from the fan in the detection process, realizes the in-situ detection of the surface defect of the main shaft, and has obvious advantages in the aspects of implementation convenience and economy.
2. According to the invention, an electronic scanning mode is used for replacing a manual scanning mode, and detection personnel do not need to enter a fan hub bin where the end surface of the main shaft is located for detection operation; aiming at the quality detection of the components, in particular to the detection of the components which are difficult to be approached, the invention provides a new idea for solving the technical problem.
Drawings
FIG. 1 is a schematic structural diagram of an ultrasonic in-situ detection system for surface defects of a main shaft of a wind turbine used in the present invention;
FIG. 2 is a structural dimension and detection area of a spindle in an embodiment of the present invention;
FIG. 3 is a schematic diagram of half divergence angle and acoustic beam radius of a single piezoelectric array element according to the present invention;
FIG. 4 is a schematic diagram of the arrangement of the piezoelectric array elements on the end face of the spindle according to the present invention;
FIG. 5a is a diagram of an echo waveform containing a defect in an embodiment of the present invention;
FIG. 5b is a defect-free echo waveform of an embodiment of the present invention;
Detailed Description
The invention is described in detail below with reference to the drawings and the detailed description.
For the main shaft of the fan, whether the quality of the main shaft can reach or even exceed the design requirement is very critical for quality detection. Practice shows that in the long-term use process of the main shaft of the fan, cracks growing towards the center of the main shaft are easily generated on the surface of the main shaft of the fan, and the cracks directly influence the service performance and service life of the main shaft.
The main shaft of the fan adopted in this embodiment is the main shaft 5 to be measured in fig. 1, the material of the main shaft is 42CrMo4, and the ultrasonic longitudinal sound velocity of the material is 5900 m/s. The structural size and the detection area are shown in fig. 2, and the detection surface is the upper end surface of the main shaft.
The detection system adopted by the embodiment comprises a computer, an ultrasonic excitation receiving device and a multi-channel gating device, and the specific implementation steps are as follows:
firstly, the material of the fan spindle in the embodiment is 42CrMo4, surface defects with Q more than or equal to 5mm need to be detected, piezoelectric array elements with the center frequency of 5MHz and the diameter phi of 20mm are selected according to a general ultrasonic detection principle, and the half-diffusion angle theta of the acoustic beam of the piezoelectric array elements is calculated to be 4.13 degrees;
step two, calculating the section radius r of the piezoelectric array element sound beam in the detection area to be 57.8mm according to the half diffusion angle theta of the piezoelectric array element sound beam calculated in the step one to be 4.13 degrees and the depth H of the detected main shaft to be detected from the end face to be 800mm, as shown in fig. 3;
step three, calculating the required number N of the piezoelectric array elements to be 24.2 (taking 25) and the vertical distance R of the center points of the piezoelectric array elements to the center line of the spindle to be 222.2mm (taking 223) according to the coverage radius R of the acoustic beams of the piezoelectric array elements obtained by calculation in the step two to be 57.8mm and the diameter D of the spindle to be detected to be 560 mm;
step four, according to the vertical distance R between the center of the piezoelectric array element and the center line of the spindle, which is obtained by calculation in step three, being 223mm and the number of the piezoelectric array elements being 25, arranging the 25 piezoelectric array elements into a circular ring, taking the center line of the spindle as a symmetry axis, and uniformly arranging the radius R being 223mm on the end face of the spindle to form a piezoelectric sensor array, as shown in FIG. 4;
fixing 25 piezoelectric array elements in the piezoelectric sensor array on the end face of the spindle, numbering the piezoelectric array elements in sequence in a clock scale mode, and setting the zero-point time position as the piezoelectric array element with the number 1 as shown in fig. 4;
step six, respectively connecting the outgoing line of each piezoelectric array element in the piezoelectric sensor array to a channel interface corresponding to the multi-channel gate to complete the arrangement and the electrical cross-linking of the piezoelectric sensor array;
step seven, sending a detection instruction through a computer to control the ultrasonic excitation receiving equipment to enable the multi-channel gating device to gate 25 numbered piezoelectric array elements in sequence for excitation and receive echo signals of the piezoelectric array elements;
step eight, the ultrasonic excitation receiving equipment collects the echo signals received each time and sends the echo signals to a computer, and the computer records the echo signals of each numbered piezoelectric array element;
and step nine, after the ultrasonic excitation receiving equipment completes the excitation, the receiving and the data transmission of the No. 25 piezoelectric array element, judging the defect position on a computer through the identification of the echo characteristics of each numbered piezoelectric array element, and completing the main shaft detection. The waveform corresponding to piezoelectric array element No. 18 stored in the computer is shown in fig. 5(a), and the waveforms corresponding to the remaining piezoelectric array elements are shown in fig. 5 (b). Fig. 5(a) shows the echo waveform with a defect;
and step ten, determining the position of the defect below the No. 18 array element of the main shaft and away from the end surface 833mm according to the number 18 of the piezoelectric array element and the echo depth corresponding to the figure 5 (a).
Claims (1)
1. An ultrasonic array in-situ detection method for surface defects of a main shaft of a fan is characterized by comprising the following steps: the detection device for realizing the detection method comprises a computer (1), ultrasonic excitation receiving equipment (2) and a multi-channel gate (3), wherein the computer (1) is connected with the ultrasonic excitation receiving equipment (2), the ultrasonic excitation receiving equipment (2) is connected with the multi-channel gate (3), and the method comprises the following specific implementation steps:
step one, selecting piezoelectric array elements with center frequency f and diameter d according to the material of a main shaft of a fan and the size Q of a defect to be detected and the ultrasonic detection principle, and calculating to obtain the range of the half-diffusion angle theta and f of the acoustic beam of the piezoelectric array elementsThe periphery is 1 MHz-5 MHz; half spread angle pass through
Calculating, wherein: c. CLThe longitudinal wave velocity of the main shaft material;
step two, calculating the section radius r of the piezoelectric array element acoustic beam in the detection area according to the half-diffusion angle theta of the piezoelectric array element acoustic beam calculated in the step one and the distance end face depth H of the area to be detected of the main shaft to be detected, and calculating the section radius r of the single piezoelectric array element (6) acoustic beam in the detection area by the method that r is H multiplied by tan theta;
step three, according to the coverage radius R of the piezoelectric array element acoustic beam obtained by calculation in the step two and the diameter D of the area needing to be detected of the detected main shaft, calculating the number N of the required piezoelectric array elements, rounding up if N is decimal, and rounding up if R is decimal, wherein R is vertical distance R between the center point of the piezoelectric array element and the center line of the main shaft:
step four, arranging the N piezoelectric array elements into a circular ring according to the vertical distance R between the center of the piezoelectric array element and the center line of the spindle and the number N of the piezoelectric array elements, wherein the vertical distance R is obtained by calculation in the step three, and the piezoelectric array elements are uniformly arranged on the end face of the spindle to form a piezoelectric sensor array by taking the center line of the spindle as a symmetry axis and taking the radius of R as a radius;
fixing the N piezoelectric array elements in the piezoelectric sensor array on the end face of the main shaft, numbering the piezoelectric array elements in sequence in a clock scale mode, and setting the zero time position as the piezoelectric array element with the number 1;
step six, respectively connecting the outgoing line of each piezoelectric array element in the piezoelectric sensor array to a channel interface corresponding to the multi-channel gate to complete the arrangement and the electrical cross-linking of the piezoelectric sensor array;
step seven, sending a detection instruction through a computer to control the ultrasonic excitation receiving equipment to enable the multi-channel gating device to gate each numbered piezoelectric array element in sequence for excitation and receive an echo signal of the piezoelectric array element;
step eight, the ultrasonic excitation receiving equipment collects the echo signals received each time and sends the echo signals to a computer, and the computer records the echo signals of each numbered piezoelectric array element;
after the ultrasonic excitation receiving equipment completes the excitation, the receiving and the data transmission of the No. N piezoelectric array element, the defect position is judged on a computer through the identification of the echo characteristics of each numbered piezoelectric array element, and the main shaft detection is completed; the specific judgment method is as follows: the echo appearing before the bottom wave of the main shaft is determined as a suspicious defect echo, the suspicious echo appearing in each numbered piezoelectric array element is a structure echo, and the suspicious echo appearing in a certain number is determined as a defect echo;
step ten, determining the defect position, namely the channel number and the depth according to the number of the piezoelectric array element with the echo and the echo depth.
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| CN107907594A (en) * | 2017-12-21 | 2018-04-13 | 爱德森（厦门）电子有限公司 | A kind of coupling process of in-service wind power principal axis low-angle ultrasonic monitoring sensor |
| CN108414624B (en) * | 2018-03-03 | 2020-11-03 | 北京工业大学 | Full waveform inversion method based detection method for crane special-shaped section structure lifting telescopic arm |
| CN109239198B (en) * | 2018-08-21 | 2020-12-25 | 北京工业大学 | Method for detecting transverse crack diffracted wave of main shaft of wind driven generator |
| CN109164034B (en) * | 2018-08-28 | 2021-01-08 | 河南科技大学 | Wheat seed quality detection device and detection method thereof |
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