Because the characteristics of rotating machinery determine that it may encounter rub-impact faults during operation and is not easy to stop for maintenance, the rub-impact positioning of rotating machinery is an urgent problem to be solved. To solve this problem, this paper proposed a parameter location method based on acoustic emission signal characteristics, and used an improved clustering algorithm to optimize the location results. This method can monitor the running of rotating machinery and accurately locate the source of rub-impact. The experimental results showed that compared with the TDOA location algorithm, the proposed method can more effectively separate the collision sources, and the improved clustering algorithm ran faster.
Using tensile testing machine and ultrasonic stress detector, axial tensile was carried out on 45 steel of volute bolt of hydropower unit, and the stress value and the corresponding ultrasonic p-wave and s-wave propagation time were measured in the tensile process, so as to obtain the ultrasonic p-wave and s-wave acoustic ratio, i.e., the ultrasonic p-wave and s-wave velocity ratio. The quantitative relationship between elastic stress and ultrasonic p-wave and s-wave acoustic time ratio was established, which provided a basis for real-time determination of bolt elastic stress by ultrasonic wave. The results showed that the axial elastic stress of 45 steel was within the elastic deformation range of the steel, and the relationship between the acoustic time ratio of ultrasonic p-wave and s-wave and the elastic stress was linear, σ=-50 249.8 Sl/St+90 536.1. The error between the stress measured by p-wave and s-wave and the actual stress was 2.36%, which meets the engineering requirements.
During the phased array ultrasonic testing of wind turbine blades with pultrusion beam, the signal is affected by the special structure of the blade and the anisotropy of its material, resulting in the low signal-to-noise ratio of the data, and the defect identification is difficult in the data analysis. To solve this problem, this paper analyzes the structure and typical defects of wind turbine blades with pultrusion beam, clarifies the corresponding relationship between phased array ultrasonic image signal and the structure of wind turbine blades with pultrusion beam, and proposes an efficient and accurate analysis process. After verification, this method helps to improve the quality of data analysis work in the wind power industry.
In the manufacturing process of pressure vessel equipments, there are many special butt welds structures, some of which are difficult to use the conventional TOFD(Time of flight diffraction) detection process for volume detection. In this paper, the TOFD test for the butt girth weld between cone and cylinder with different thickness was analyzed and studied. The whole process was introduced from the basic theory of TOFD, the design and manufacture of special block, the preparation of TOFD scan plan, the test verification and the analysis of the final test results. The results were satisfactory and can be applied to engineering practice.
Cavity and delamination are common defects in brazed joints, and the quality of brazed joints was impacted by the area of defects. In order to calculate the defect area accurately and efficiently, the defect recognition algorithm was proposed to mark the defect. Firstly, ultrasonic microscopy system was used to detect the brazed workpiece and generate ultrasonic C-scan image. Then the C-scan image was binarized with the threshold-based image segmentation method. Finally, the defect was marked and the defect area was calculated using the proposed defect recognition algorithm. The accuracy and efficiency of defect detection was improved.
Aiming at the shortcomings of the ultrasonic guided wave phased array method, this paper proposed a damage focusing imaging method for composite materials using multiple array of ultrasonic guided wave frequency-phased joint control excitation. Compared with the standard ultrasonic guided wave phased array technology, this method realized angle-distance focused scanning and damage locationon composite material plates by setting different excitation frequencies on each array element. Firstly, the signal model of multi-array ultrasonic guided wave frequency and phase joint control excitation focusing was established; Secondly, a distributed multiple-input multiple-output (MIMO) linear array was designed to focus and scan the monitoring area point by point, and the array ultrasonic guided wave damage echo reception was established, and the multiple signal classification (MUSIC) method was used to realize composite material Imaging of damage. The simulation and experimental results of glass fiber plate showed that the method had good focusing performance, high damage imaging and positioning accuracy for composite materials.
The damage characteristics of the acoustic emission signals produced in high temperature ceramic matrix composites were analyzed based on the relations between acoustic emission (AE) signals and X-ray CT images. The characteristic parameters including the frequencies of AE signals were obtained by analyzing the signals of macroscopic stress waves in the case of composite damage by using AE technology. Existing damage types can be confirmed by the microscopic 3D damage images of composite structures were obtained by CT method. The results showed that different types of damage can generate in the interior of ceramic matrix composite specimens fabricated by different processing techniques under tension load. The corresponding frequency of AE signals for the delaminations between fiber bundles and the matrix damage and fiber bundle fracture were respectively 44 kHz, 150 kHz and 250 kHz.
In response to the need for in-service monitoring of titanium alloy damages in high-temperature environments, a real-time dynamic monitoring technology using acoustic emission (AE) was proposed. In this paper, the acoustic emission monitoring test of tensile damage mechanics of TA15 titanium alloy at high temperature was carried out by simulating the high-temperature environment in the real casing. Firstly, titanium alloy was determined as the material for waveguide rods. Then, the titanium alloy specimens welded with waveguide rods were subjected to high-temperature tensile tests at different tensile rates. Experiments showed that the mechanical properties exhibited regular changes at different temperatures. Acoustic emission technology can successfully monitor and characterize the damage evolution of titanium alloys, and counting can clearly reflect the different mechanical stages of tensile experiments at high temperatures.
To ensure the stability of the bolt connection, a certain tightening force is required on the bolt. Currently, the measurement of the tightening force of in-service bolts remains a technical challenge. This paper proposed a method to measure bolt tightening force using the ratio of ultrasound transverse and longitudinal waves, and verified through measurement, with the results showing high detection accuracy for the double-wave method.Studied the factors affecting the accuracy of the double-wave method, a temperature correction coefficient was proposed to compensate for the influence of temperature on the measurement of bolt tightening force. This method has high engineering application value in measuring the tightening force of in-service bolts.
In order to meet the demand of detecting moisture content of aggregates in industrial production, an analysis model was constructed based on microwave transmission and multiple linear regression model theory, its significance and the reliability of its detection results were studied. The comparison deviation and its root mean square error, standard deviation and coefficient of variation evaluation indexes were established to represent the repeatability and accuracy of the off-line and on-line measurement results of the water content of aggregates with different particle size ranges of 0~4. 75 mm, 4. 75~16. 00 mm and 16. 00~31. 50 mm. The results showed that the multiple linear regression analysis model had a high goodness of fit, the deviation range of offline and online detection data was ±0. 3%, and the root mean square error was 0. 148%, 0. 13%, 0. 147%. The test results were highly consistent and meet the requirements of engineering detection.
This study investigated the gate adjustment of ultrasonic A-scan signals in the process of ultrasonic C-scan detection system, and proposed a multi-gate dynamic tracking method suitable for workpieces with variable thickness. The basic principle was to set the detection gate on the echoes between the surface and bottom of the variable thickness workpiece, and the detection gate simultaneously tracked the surface echo and the bottom echo. This method can improve the circumstance when the surface or the bottom of the variable thickness workpiece changed during the detection process, it reduced the influence of interference waves and maximized the effective data collected by the gate. Finally, the feasibility of the multi-gate dynamic tracking method was verified by using water immersion ultrasonic testing to detect variable thickness stainless steel plates with artificial defects.
In order to improve the conversion efficiency of the conventional Electromagnetic Acoustic Transducer (EMAT) surface wave transducer, this paper proposes a new type of biased magnetic field EMAT transducer. A two-dimensional simulation model of EMAT excited surface wave is established using finite element software to compare and analyze the influence of conventional and biased EMAT on the excited surface wave. Finally, an orthogonal experiment is designed to study the influence of magnet height, magnet width, line height, line width, and coil lift on the excited surface wave of the biased EMAT. The accuracy of the orthogonal experiment was verified by experiment. In addition, the influence of biased magnet on the receiving EMAT was also studied. The research results showed that the amplitude of the excited surface wave of the biased EMAT was 51% higher than that of the conventional EMAT, and this method does not cause main frequency bifurcation distortion in the frequency domain information. The amplitude of the receiving signal using the biased EMAT was 38% higher than that of the conventional EMAT, and the biased EMAT can effectively improve the detection sensitivity.
Welds exist widely in industrial sites, and the quality inspection of welds based on X-ray flaw detection is very important to maintain the normal operation of production and life. However, high-quality X-ray flaw detection images have high bit counts. Therefore, the weld image processing system has problems such as slow reading, high power consumption and poor real-time performance. Therefore, this paper proposed a welding seam X-ray image compression method based on Walsh-Hadamard transform. Image optimization was realized based on the energy concentration property of Walsh-Hadamard transform, and key feature boundaries of weld images were preserved. The quantum particle swarm optimization algorithm was used to realize the adaptive optimization of the compression parameters of the Walsh-Hadamard transformation of the weld image. The actual production site image verification results showed that while the size of the compressed image was one-tenth of the original image, the method in this paper can preserve the weld features and image quality to the greatest extent, making the subsequent weld detection based on X-ray images more efficient.
Electromagnetic nondestructive testing technology is an important method for monitoring the condition of steel wire ropes. This paper summarized electromagnetic testing technology for steel wire ropes, from four parts: electromagnetic testing methods for steel wire ropes, signal preprocessing, feature extraction, qualitative judgment, and quantitative analysis. This paper summarized outlined the research status and related progress of electromagnetic testing technology for steel wire ropes. The impact of different detection techniques on the detection of steel wire rope defects also plored, and from the perspective of signal processing, commonly used noise reduction methods, feature extraction algorithms, and qualitative and quantitative analysis methods were analyzed. The impact of noise such as strand waves and vibrations on steel wire rope defect signals and corresponding noise reduction methods were discussed. On the basis of comparing the advantages and disadvantages of feature extraction algorithms, an effective method for qualitative judgment and quantitative analysis of damage was proposed. Finally, the shortcomings and future development directions of electromagnetic testing technology for steel wire ropes were discussed.
