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2021 Vol. 64, No. 21
Published: 2021-11-01
FEATURE
FORUM
RESEARCH
C0NTENTS
COVER STORY
APPROACHING SCIENCE
 
       COVER STORY
1 COVER
2021 Vol. 64 (21): 1-1 [Abstract] ( 113 ) HTMLNew PDF (978 KB)  ( 98 )
       C0NTENTS
6 CONTENTS
2021 Vol. 64 (21): 6-10 [Abstract] ( 99 ) HTMLNew PDF (812 KB)  ( 66 )
       FEATURE
14 Research on Ultrafast Laser Machining of Film Cooling Hole in Turbine Blade
ZHANG Xiaobing, JI Liang,CAI Min, MAO Zhong, LI Yuancheng, ZHANG Wei
DOI: 10.16080/j.issn1671-833x.2021.21.014
Making film cooling holes by ultrafast laser in turbine blade of single crystal superalloy to obtain better quality was studied widely at home and abroad. Ultrafast laser drilling research status abroad on making relatively high depth-diameter-ratio was briefly introduced at first. Then the quality of hole’s wall, the relationship between of hole’s depth and efficiency made by ultrafast laser at 2.1ps pulse width, 400μJ pulse energy and experimental results of fatigue life comparison of three groups samples of single crystal superalloy with holes which were made by ms, ns, ps laser separately were presented. The technical research results were described on making film cooling holes in turbine blades with thermal barrier coatings, in double wall blades and processing shaped film cooling holes. Further research focused on putting ultrafast laser drilling technology into production of making film cooling holes in turbine blades was proposed.
2021 Vol. 64 (21): 14-22 [Abstract] ( 431 ) HTMLNew PDF (19527 KB)  ( 363 )
       COVER STORY
24 Cross-Sectional Imaging and Defect Evaluation of Composite Repairs Using High-Resolution Ultrasonic Technique
LIU Feifei, ZHOU Zhenggan, LIU Songping, YANG Yusen,ZHANG Lianwang
DOI: 10.16080/j.issn1671-833x.2021.21.024
The recovery of composite structure using performance is closely related to the repair quality. Repair quality is associated with defects in repair area. Complex repair behavior and conditions increase the difficulty and uncertainty in non-destructive testing and evaluation (NDT & E) of composite repair. A high-resolution ultrasonic (HU) technique was proposed to characterize carbon-fiber composite repair behaviors and detect defects induced in repair zones. A HU detection system was constructed. The composite repair specimen was manufactured. The time-domain behaviors of the HU signals in repaired area were studied. A series HU experiments were carried out to the repaired specimen using HU cross-sectional imaging technique. The experimental results show that the quality and time-domain resolution of HU echo signals are obviously better than conventional ultrasonic method; the estimated thickness based on the HU signals is close to 0 deviation from its design value for a 4.5mm thick carbon-fiber composite repaired specimen; the detail repair behaviors, such as repaired area, repaired area morphology, repaired bonding interfaces topography, defects and local resin zones in repaired area, internal microstructures, are very clear and intuitively revealed using the HU cross-sectional imaging and image grayscale distributions; the φ 6mm defects located at near the specimen surface and bottom layers and middle depth are detected clearly and intuitively; the imaging resolution is up to the thickness of a single ply (~0.125mm). Thus, it provides a very effective and powerful detection and evaluation for composite repairs, and good practical application has been obtained.
2021 Vol. 64 (21): 24-31 [Abstract] ( 186 ) HTMLNew PDF (5648 KB)  ( 325 )
       FORUM
34 Research Progress of Ultrasonic Testing and Evaluation Technology for Fiber Buckling Defects of Laminated Structure of Advanced Resin Matrix Composites
XU Guirong, MA Tengfei,LI Yang,XIAO Peng,ZHOU Zhenggan
DOI: 10.16080/j.issn1671-833x.2021.21.034
In recent years, to meet the new requirements of nondestructive testing and evaluation of fiber buckling in aircraft industry, many researchers have carried out NDT&E research on fiber buckling defects using ultrasonic. Unlike typical defects such as delamination, porosity and inclusion, fiber buckling defects resulting in less acoustic impedance mismatch to reflect the transmitted ultrasonic wave, it is difficult to characterize fiber buckling defects by ultrasonic A-scan signal. The main research progress of ultrasonic nondestructive testing and evaluation technology of fiber buckling defects has been introduced from three aspects including detection principle, ultrasonic transducer parameter selection and ultrasonic data post-processing method. In the meantime, the shortcomings of current research and its future development trends have also been discussed. In terms of detection principle, the structure characteristics of CFRP laminates, the different ultrasonic responses caused by the local structural changes caused by the out-of-plane/in-plane fiber buckling defects, and the detection scheme of the fiber buckling defects by using different ultrasonic response characteristics are introduced. In the aspect of parameter selection of ultrasonic transducer, the selection criteria of using half-wave resonance to maximize the interlayer echo energy are introduced. In the aspect of ultrasonic echo data post-processing, the methods are presented that the instantaneous phase method and average scattering coefficient matrix are used to detect the out-of-plane fiber buckling defects, the angle spectrum distribution and local image operator are used to detect the in-plane fiber buckling, and the three-dimensional direction of the carbon fiber is measured by the image structure tensor. Finally, the shortcomings of the current research work and the future development trend are analyzed in the aspects of acoustic mechanism, detection ability, types of detectable defects and types of inspected structural parts.
2021 Vol. 64 (21): 34-42 [Abstract] ( 173 ) HTMLNew PDF (18789 KB)  ( 118 )
43 Experimental Study on Optimization of Multi-Features of Ultrasonic Signals of Resistance Spot Welding Defects
HUANG Hong, WU Wei,LI Kunhang,YANG Hongrui,YIN Xiangjie,JIANG Qiming,DENG Zhanying
DOI: 10.16080/j.issn1671-833x.2021.21.043
For the common ultrasonic echo signals of porosity, unfused and defect-free aluminum alloy spot welded joints, noise reduction and reconstruction were first performed with empirical mode decomposition (EMD) analysis, and multi-scale eigenvalues in the time and frequency domains were extracted using statistical methods to analyze the eigenvalue variation patterns of different defects. The principal component analysis (PCA) and linear discriminant analysis (LDA) are used to optimize the feature values and obtain the principal element features of the defective echo signal, finally the principal element features are used as the input of the BP neural network to identify the defect signal. The experimental results show that the feature quantities constructed by the two dimensionality reduction methods have better classification results compared with those without dimensionality reduction, with PCA acting better and effectively improving the defect recognition accuracy of BP neural networks.
2021 Vol. 64 (21): 43-50 [Abstract] ( 122 ) HTMLNew PDF (1326 KB)  ( 245 )
51 Evaluation of Composite Matrix Crack Using Nonlinear Ultrasonic Lamb Wave Detected by Fiber Bragg Grating
WANG Rong, WU Qi,XIONG Ke,ZHANG Hanqi
DOI: 10.16080/j.issn1671-833x.2021.21.051
A high-sensitive and broad-bandwidth phase-shifted fiber Bragg grating based ultrasonic detection system with proportional-integral-derivative feedback controller was proposed to evaluate the ultrasonic nonlinearity induced by the matrix crack in carbon fiber reinforced plastic. After the optical fiber sensing system detected the ultrasonic Lamb wave propagating in a composite laminate, the second harmonic components with a frequency of 2.0MHz was extracted from Lamb wave signals by data processing. The result show that the relative nonlinear parameter grew linearly with the increase of crack numbers. In comparison with conventional lead zirconate titanate sensor, the relative nonlinear parameter detected by the phase-shifted fiber Bragg grating sensor shows a higher growth rate. Thus, the proposed fiber optic-ultrasonic detection system with high reliability can be applied to the evaluation of matrix cracks damage of composite materials.
2021 Vol. 64 (21): 51-56 [Abstract] ( 157 ) HTMLNew PDF (4675 KB)  ( 316 )
57 Study on Acoustic Reflection Characteristics and Detection Application of Line Focusing Probe
DUAN Jiangang, XIONG Ying
DOI: 10.16080/j.issn1671-833x.2021.21.057
The line focusing probes with focal lengths of 25mm, 35mm, 45mm and 50mm were selected, φ 1.5mm steel bar was used as reflector, by changing the relationship of position between the probe and the steel bar, the acoustic reflection characteristics of the line focusing probe in water were measured, and the detectable diameter range of the bar with different focal length was obtained; A line focusing probe with a focal length of 45mm was selected, φ 47 GH4169 superalloy bar sample was tested under different water distances, and the position of flat bottom hole used to determine the detection sensitivity of bar was obtained; φ 18 TC4 bar sample and the line focusing probes with focal lengths of 25mm, 35mm, 45mm and 50mm were selected, the experiments to characterize the reciprocating transmission of sound wave and directivity of sound beam were carried out, the selection method of water distance corresponding to the highest reflected wave amplitude of flat bottom hole used to determine the detection sensitivity of bar was obtained; The line focusing probes with focal lengths of 25mm, 35mm, 45mm and 50mm were selected, TC4 titanium alloy bar samples with different diameters were tested, the diameter range of detectable bar with line focusing probes of different focal length was verified. The measurement and characterization of acoustic reflection characteristics of line focusing probe and its application in bar inspection were solved.
2021 Vol. 64 (21): 57-67 [Abstract] ( 138 ) HTMLNew PDF (16696 KB)  ( 88 )
       APPROACHING SCIENCE
68 Focus on Lightweight Materials and Manufacturing Research for Needs of Carbon Peak and Carbon Neutrality Industry
2021 Vol. 64 (21): 68-69 [Abstract] ( 98 ) HTMLNew PDF (892 KB)  ( 110 )
       RESEARCH
77 An Accuracy Compensation Method for Industrial Robot Based on Optimized Correlation Model
CHENG Simiao,TIAN Wei,LI Bo,LIAO Wenhe
DOI: 10.16080/j.issn1671-833x.2021.21.077
Due to the low absolute positioning accuracy, industrial robots are difficult to be directly applied to aerospace high precision manufacturing. In order to improve the absolute positioning accuracy of industrial robot, a robot accuracy compensation method based on optimized correlation model is proposed. Based on the principle of error similarity, the mathematical relationship between robot positioning error and joint angle is constructed. The simulation results show that the influence of different correlation models on accuracy compensation effect is analyzed. Finally, the optimal model is selected through experiments. The experimental results show that the proposed method can improve the absolute positioning accuracy of industrial robot from 1.8057mm to 0.2902mm. The research results of this paper provide a technical means to promote the application of industrial robots in aerospace high precision manufacturing.
2021 Vol. 64 (21): 77-83 [Abstract] ( 121 ) HTMLNew PDF (6528 KB)  ( 235 )
84 Research and Application of Automatic Drilling Equipment in Aircraft Assembly
LI Haiwei, PAN Xin, ZHANG Hui, DU Jie, LI Deyi
DOI: 10.16080/j.issn1671-833x.2021.21.084
Compared with the tradtional manual drilling technology, the application of automatic drilling technology in aircraft assembly has become an inevitable trend. In order to improve the efficiency and quality of drilling, the automatic drilling equipment is used in the assembly of certain aircraft parts. The experiments and analysis were carried out for the technical problems encountered in the application of the automatic drilling equipment and the processing parameters such as pressure, speed and feed rate were determined, the problem of low rigidity of parts was solved, the date processing flow was optimized, and the optimized process flow was introduced.
2021 Vol. 64 (21): 84-89/95 [Abstract] ( 161 ) HTMLNew PDF (8697 KB)  ( 237 )
90 Design of Adaptive Machining Fixture for Large Aircraft Structural Part Based on TRIZ
LIU Shi, MA Fei, CHU Fushun
DOI: 10.16080/j.issn1671-833x.2021.21.090
Large aviation structural parts have the characteristics of complex structure, small wall thickness and large material removal rate, which are easy to produce machining deformation and have a great influence on product quality. Due to technical blockade, imported raw materials with better performance are difficult to obtain and costly. Because of the uneven distribution of residual stress, the machining deformation of domestic blank is uncontrollable, which makes the problem more prominent. On the basis of analyzing the machining deformation mechanism and the current process scheme, the technical conflicts are found by using the analysis tool of TRIZ innovation theory. Based on contradiction matrix and innovation principle, a solution of "adaptive clamping of aircraft large structural parts" is proposed. In practical application, this scheme can effectively avoid the deformation of parts and improve the clamping efficiency, reduce the production cost, achieve remarkable results.
2021 Vol. 64 (21): 90-95 [Abstract] ( 151 ) HTMLNew PDF (15571 KB)  ( 96 )
96 Design and Optimization of 100kV Electron Gun for Welding
SI Qingrun,DONG Quanlin,SANG Xinghua
DOI: 10.16080/j.issn1671-833x.2021.21.096
A high-power electron gun for welding was designed by using LaB6 indirect thermal cathode and using the integrated iteration method. On the basis of theoretical design, the initial structural parameters were optimized and adjusted through the Source module in the Munro software. In the end, the design index of power 36kW, acceleration voltage 100kV, emission beam current 360mA, beam waist diameter 300μm was reached. A large number of simulation experiments were carried out using the single variable method. The relationship of the grid position, grid aperture, grid voltage, anode position, anode aperture of the electron gun and the size of the electron beam and the beam waist diameter was summarized. This has certain guiding significance for the adjustment and optimization of the structural parameters of the three-pole electron gun.
2021 Vol. 64 (21): 96-100 [Abstract] ( 173 ) HTMLNew PDF (1143 KB)  ( 280 )
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