Table of Content

30 March 2015, Volume 49 Issue 03 Previous Issue    Next Issue

Mathematical sciences and chemical

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Welding Process of Consumable DoubleElectrode GMAW with Single Power Supply SHI Yu，ZHOU Hai，ZHU Ming，WANG Guilong 2015, 49 (03):  293-296.  Abstract ( 720 )   Save Abstract： To decrease the welding costs, an innovation was proposed to realize a stable consumable doubleelectrode gas metal arc welding process with single power supply. Based on the xPC target system with realtime target environment，welding experiments were conducted. The results show that a stable welding process was realized; the stable welding parameter of bypass wire feed speed were also acquired when the main welding current was 300,350,400,450,500 or 550A. References | Related Articles | Metrics

Metallography and Metallurgical Technology

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Correction of MultiLayer Path Planning Based on Vision Recognition YANG Chengdong,ZHONG Jiyong,CHEN Yuxi,CHEN Shanben 2015, 49 (03):  297-300.  Abstract ( 767 )   Save Abstract： A novel technology of double sided arc welding (DSAW) in which the gas metal arc welding (GMAW) was employed for root welding and filler passes respectively was proposed in this paper. The correction of multilayer path planning based on vision recognition (CMLPPBVR)  was proposed to decrease the accumulated error and increase the precision of path planning. Laser stripe was used to scan the filler condition of the groove after each welding bead was welded. The real time filler information of each welding bead can be obtained through the image processing and 3D information restoration to correct the multilayer path planning, which improves the precision of multilayer path planning. References | Related Articles | Metrics

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Measurement of Characteristic Parameters of Three Dimensional Weld Pool Surface in Tungsten Inert Gas Arc Welding Based on Laser-Vision ZHANG Gang,SHI Yu,LI Chunkai,FAN Ding,HUANG Jiankang 2015, 49 (03):  301-305.  Abstract ( 682 )   Save Abstract： Aimed at the problems in measuring the three dimensional weld pool surface in tungsten inert gas arc welding in existing methods, which are hardly applied in the strong arc light, high temperature radiations and specular refection. A novel method named laservision was developed, and the measurement system was established. The experiments with laser dot matrix and parallel lines pattern were performed and the reflected laser distorted images were captured by a high speed camera. The reflected laser dot coordinate and its transfer model between projected laser dot coordinate were extracted and established, respectively. The geometric parameters of the weld pool surface were obtained offline. The comparison of the extracted and measured result shows that the proposed method can successfully measure the three dimensional information of the weld pool surface and the extracted results coincide with the actual measurement well. The error of width, length and convexity is 0.8%,0.6% and 4.7%, respectively. This paper provides a new method for control of 3D weld pool surface in realtime. Key words： References | Related Articles | Metrics

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Effect of Heat Input on Microstructure and Toughness of Weld Joint  of High-Strength LowAlloy Steel CHEN Yuxi1，LIU Liang2，ZHANG Huajun2，CHEN Huabin1，CHEN Shanben1 2015, 49 (03):  306-309.  Abstract ( 1072 )   Save Abstract： High strength low alloy steel Q690E thick plate of offshore drilling platform was welded by GMAW with different heat inputs. The effect of heat input on the microstructure and toughness of weld joint was investigated. The results indicated that the microstructure of the weld mainly consisted of acicular ferrite, and the best low temperature toughness could be obtained at the heat input 1.56 MJ/m. Under the condition of the same welding heat input, the microstructure of the weld was more uniform and the low temperature toughness was better at smaller welding current and slower welding speed. Besides, under the condition of the same heat input, the microstructure of the weld from robotic singlewire MAG welding was based on acicular ferrite and granular bainite. Moreover, the toughness of the weld metal of robotic single wire MAG welding was better than twinwire MAG welding. Key words： References | Related Articles | Metrics

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Detection of Intersecting Line Dedicated to J-groove Joints Based on SVM TUO Yukun1，HU Shengsun1，SHEN Junqi1，CHEN Changliang2，GU Wen3，LI Jian3 2015, 49 (03):  310-314.  Abstract ( 646 )   Save Abstract： In the automatic welding process of nuclear reactor vessels, the joints of the tubesphere intersections are usually complex. This paper presents a complete algorithm in detecting the intersecting line of the Jgroove based on image processing techniques and the support vector machine (SVM) classifier. Taking the combination of color moment feature and optimized gray level cooccurrence matrix (GLCM) feature as the feature vector, classification was made using the SVM classifier to acquire a binary image with the intersection area highlighted, while the image block sliding mechanism and voting mechanism were applied. The precise position of the intersecting line was detected by fitting a quadratic curve of the maximum outline. Experimental results show that the algorithm can endure a complex environment and can achieve realtime requirement. The accuracy of the SVM classifier is up to 95.6%, and the processing time of each image is less than 170 ms. References | Related Articles | Metrics

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Influence of Environmental Pressure on GMAW Process and The Weld Bead Appearance WU Jinming1,XUE Long1,HUANG Jiqiang1，LIU jian1,LI Lan2,XU Lei3 2015, 49 (03):  315-318.  Abstract ( 775 )   Save Abstract： Underwater hyperbaric dry gas metal arc welding (GMAW) welding technology is one of the key technologies for the maintenance of underwater equipment, such as shipping, ocean platform, seabed pipeline. To get high quality and high efficiency underwater welding technology parameters, the effect of hyperbaric ambient on GMAW is of important practical significance. The characteristics of the weld appearance and the GMAW process were studied at ambient pressure from 0.1 MPa to 1.0 MPa by using a highspeed camera and a Hannover analyser. The causes of weld spatter and the characteristics of weld appearance were analyzed. The experiment shows that as the number of the spatters increase, the weld joint becomes narrower and worsens gradually as the ambient pressure increases. Key words： References | Related Articles | Metrics

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Mathematical Modeling and Workspace Analysis of Visual Tracking Robot for Welding HE Jingjie1,WANG Su1，2,MIAO Xingang1，2 2015, 49 (03):  318-322.  Abstract ( 1010 )   Save Abstract： This paper describes a space robot modeling method. The main idea is to shift the moving coordinate system to the working point of the robot by following the mechanisms and joints. The robot was modelled to get the forward kinematics results and then simulated in Matlab. By analyzing the robot workspace with numerical method, the isometric view and profile of the workspace were obtained. The simulation experiments show that the mathematical modeling method is effective. The result of workspace analysis shows that the workspace is big enough without hole, which meets the demand of tracking. The motion tracking test on curve in space with the physical prototype is satisfactory. References | Related Articles | Metrics

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Arc Sound Acquisition and Analysis of Hyperbaric Underwater MIG Welding LI Weiqiang1,ZHU Jialei1,JIAO Xiangdong1,QIAO Xi1,JIA Cunfeng2,MA Zhengzhu1 2015, 49 (03):  323-325.  Abstract ( 699 )   Save Abstract： The hardware of arc sound acquisition system in hyperbaric underwater MIG welding was designed, the influence of different pressure to voice signal was studied, and the microphone was calibrated according to different pressures. Based on the LabVIEW software programming, the arc sound signal, welding current and arc voltage during welding were asynchronously acquired and the signal feature of arc sound in the different pressures was analyzed both in time domain and frequency domain, which lay the foundation for the application of arc sound signal in hyperbaric underwater MIG welding quality control. References | Related Articles | Metrics

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Aluminum Sheet Laser Welding Deformation Measurements HUANG Zunyue，LUO Zhen，ZHANG Yu，YAO Qi 2015, 49 (03):  326-328.  Abstract ( 912 )   Save Abstract： This paper reveals that the intensity of the light emitted by aluminum sheet laser welding, which possess a wavelength of 600 nm to 650 nm is nearly constant. A suitable narrow bandwidth filter was selected to prevent the fluctuation of the light, so that the pictures taken by the CCD camera have a coherent intensity. The images taken by two independent CCD cameras driven by pulsing signal simultaneously could reveal the threedimensional deformation, morphology and strain of the entire plate which were welded in the optimal welding parameters in real time. This procedure could help study the sheet laser welding deformation clearly, which was significant in the field of control welding distortion. References | Related Articles | Metrics

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Chamber Local Dry Underwater Welding ZHU Jialei1,WANG Dianshu2,JIAO Xiangdong1,CHEN Maoxiao1 2015, 49 (03):  329-332.  Abstract ( 978 )   Save Abstract： Due to the relatively large gas space and better flexibility, chamber local dry underwater welding has a better application prospect in repairing offshore gas and oil pipeline and nuclear spent fuel pool. With the development of chamber local dry underwater welding system, the verification test of buildup welding and butt welding were conducted in a 300 mm depth water environment, and the microstructure and hardness of butt weld were analyzed. The results show that with the premise that the chamber was well sealed, the wire feed speed, welding speed, weaving speed and weaving period  have a great influence on the weld formation and welding quality. By optimizing different welding parameters, a good appearance of chamber local dry underwater welding weld can be obtained; Underwater welding environment has influence on hardness and microstructure of weld; Due to the rapid  cooling effect  of water back and around the weld, some widmanstatten structure appear in the  center region of the weld, the hardness in  the central region is higher than that in the heat affected zone  and, hardening phenomenon appeared. References | Related Articles | Metrics

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Weld Forming and Mechanical Property of Stainless Steel Underwater Laser Welding YAO Qi,LUO Zhen,LI Yang,DUAN Rui,HUANG Zunyue 2015, 49 (03):  333-336.  Abstract ( 903 )   Save Abstract： The local dry underwater laser welding was applied on 1mm thick SUS304 stainless steel. The effect of water depth and shielding gas flow rate on the weld forming and weld mechanical property was investigated. The results show that when the water depth and shielding gas flow rate is appropriate, the weld with good shaping can be obtained. Meanwhile, the tensileshear strength of weld is similar with that of base metal. At a given water depth, when the gas flow rate increased, the weld width increased, and when weld penetration decreased, the depth-to-width ratio decreased. When the gas flow rate was constant, the variation of weld width and weld penetration is similar when the water depth increases. Compared with the traditional laser welding, the underwater laser welding changes the direction and rate of heat dissipation, resulting in the lessening of weld penetration and widening of weld width. References | Related Articles | Metrics

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Algorithm and Three-Dimensional Reconstruction for Tungsten Inert Gas Arc Welding Pool Surface HUANG Jiankanga，HE Xiaoyinga，ZHANG Gangb，SHI Yub，FAN Dingb 2015, 49 (03):  337-340.  Abstract ( 767 )   Save Abstract： To measure the highly dynamic and irregular mirror surface of the welding pool, the mathematical model for reconstructing the TIG welding threedimensional surface was proposed based on the existing algorithm. To reconstruct the threedimensional surface of different convex and concave using the new algorithm, lasers were reflected by different three-dimensional surface reforming different lasers dots matrix distribution on the imaging screen. The Matlab software was used to compile the corresponding procedures for the visualization of the welding pool. The result shows that mathematical model can better reflect the level of the welding pool surface successfully by relying on the lasers dots matrix distribution on the imaging screen, but in order to improve the reconstruction accuracy, more constraints should be applied. Key words： References | Related Articles | Metrics

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Passive Visual Technology in Aluminum Alloy Welding SHEN Hongyuan1，2,CHEN Huabin2,LIN Tao2,CHEN Shanben2 2015, 49 (03):  341-343.  Abstract ( 680 )   Save Abstract： This paper developed a passive visual sensing technology with doublewindows inspection, which was applied in gas tungsten arc welding (GTAW) for aluminum alloy. The profile of pool and seam gap was measured clearly. These data were applied in the weld quality control and seam tracking, and the sensor was used in component welding in the rocket. References | Related Articles | Metrics

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Control of Pulsed DE-MIG Welding Process ZHU Ming，SHI Yu，FAN Ding，LU Lihui，ZHOU Hai 2015, 49 (03):  344-347.  Abstract ( 716 )   Save Abstract： Pulsed DE-MIG welding is a novel welding method which can realize low heat imput. Aimed at the unstable problem of coupling arc in the pulsed DEMIG welding process, a control scheme was proposed which  changed the wire feed speed to adjust the main arc length and  to control the stability of the coupling arc. The simulations and welding experiments of control scheme were conducted based on the Matlab/Simulink and xPC target welding experiment system. The simulations showed that the control scheme was effective, and the welding results proved the simulations and a good weld apperance was acquired. Key words： References | Related Articles | Metrics

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Robot Tracking of Vertical Welding Seam Based on Rotating Arc Sensor LE Jian,ZHANG Hua,YE Yanhui,FAN Yu 2015, 49 (03):  348-352.  Abstract ( 759 )   Save Abstract： In order to achieve robot tracking of vertical welding seam accurately, improve the quality and efficiency of welding, and reduce labor intensity of welders, the sampling current was filtered by method of combination. Linear regression was done by using the method of “absolute difference” from the first sampling point to the 32th sampling point to regard the slope of fitting line as a deviation. The deviation and deviation change rate was used as the input of the fuzzy controller. The vertical welding seam was tracked by controlling level slider telescopic after fuzzification of the input, fuzzy reasoning and defuzzification of the output. The welding torch was made to move from updip 45 degrees to downdip 45 degrees by path planning. The vertical welding seam was tracked by combining path planning and horizontal slider telescopic. Experimental results show that the robot can well track the vertical welding seam based on rotating arc sensor by using the algorithm, which have good reliability and high accuracy. References | Related Articles | Metrics

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A Vision Sensing Based Welding Deviation Detection Algorithm for Rotating Arc Narrow Gap MAG Welding LI Wenhang1,2,GAO Kai1,WANG Jiayou1,HE Jinqiao1 2015, 49 (03):  353-356.  Abstract ( 859 )   Save Abstract： Aimed at welding seam tracking of multilayer single pass welding by narrow gap rotating arc MAG, a passive vision sensing based welding deviation detection algorithm was proposed. First，the welding image was obtained by the welding position sensor and the CCD camera in trigger mode when the rotating arc was on the left or right side of the groove. Second, two adaptive thresholds were computed according to the grayscale histogram of the welding image. The large threshold was used to obtain the arc region and the arc central location. The small threshold was used to obtain the base metal area of the groove, and the edges of the groove were obtained by calculating the horizontal direction firstorder difference in special horizontal positions. Finally, by comparing the image process result of two images in each rotation arc cycle, the welding deviation, i.e. the difference between the center of arc rotating and the center of the groove, were obtained. The deviation detection algorithm is efficient and reliable. It can avoid the interference of the variation of the groove bottom, and be used for comparison or integration with other deviation detection algorithms. References | Related Articles | Metrics

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Tracking Technology in Pipe Welding Based on Arc Sensor LUO Yu1,HAN Suxin1,JIAO Xiangdong1,ZHOU Canfeng1,HU Sheng2 2015, 49 (03):  357-360.  Abstract ( 646 )   Save Abstract： It is difficult to control the position of the torch very accurately for long periods because of the errors caused by the processing of pipeline and orbital assembled and thermal deformation. To adjust the torch height at a constant length is one of the key factors to guarantee the welding quality in the allposition of pipeline welding. A mathematical model was built regarding the relationship between the welding current and the CTWD, a multimodel variablegain PID control algorithm was proposed, and a multi-model controller based on fuzzy switching rules was designed to deal with the changes of welding standard in allposition welding. The test results show a good steady state and dynamic performance in CTWD control. The realtime CTWD control in different welding standard can be achieved. These methods ensure the stability of the welding process and improve the quality of welding. References | Related Articles | Metrics

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Double-Side Image Processing and Feature Extraction of  Variable Polarity Vertical-Up Plasma Arc Welding CHEN Lulu,HU Minghua,CHEN Yunxia,WU Di,CHEN Huabin,LIN Tao 2015, 49 (03):  361-365.  Abstract ( 754 )   Save Abstract： In order to obtain the double-side image feature signal for variable polarity verticalup plasma arc welding, an adaptable image processing method was proposed. The tree part-based model image processing algorithm and linear scanning edges algorithm were used simultaneously, and the appropriate one was selected. The result shows that reliable geometric features of front pool and back keyhole puddle can be obtained with the proposed method, which enables it to integrate muti-visual signals. References | Related Articles | Metrics

Automation Technique, Computer Technology

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A Novel Approach for Determining Intrinsic Parameters of Camera Using Two Parallelograms WANG Xiuping1,2,BAI Ruilin1,LIU Ziteng1 2015, 49 (03):  366-370.  Abstract ( 917 )   Save Abstract： According to the relationship between crossratio and angle, a novel linear approach was proposed to determine the  intrinsic parameters of the camera. The image coordinates of the two circular points were derived from two different methods concerning the images of two parallelograms using the Laguerre theorem and the invariance of crossratio. Then the intrinsic parameters of the camera are linearly calibrated from three images of parallelograms according to the circular points which are in the absolute conic(AC). Compared with the calibration method based on rectangles, this approach further weakens the required conditions. Therefore, it has a wide applicability. Extensive simulations and experimental results with real images show that the proposed approach is practicable. References | Related Articles | Metrics

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Seam Yracking Control Mechanism and Theoretical Analysis of Welding Mobile Robot Lv Xueqin1,ZHANG Ke2,WU Yixiong2 2015, 49 (03):  371-374.  Abstract ( 1063 )   Save Abstract： A mobile welding robot was made, the kinematics and dynamics model of the welding mobile robot were established, and a control algorithm to achieve seam tracking of a mobile welding robot was proposed. Based on the dynamics of the mobile welding robot, the theories of sliding mode for robust control were used in the proposed control algorithm, and smooth continuous function was used instead of the traditional switching function to deduce the chattering. The effectiveness of the proposed method is verified by experiments. In the seam tracking process, the robot moves steadily without any obvious chattering. References | Related Articles | Metrics

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Precision Prediction Model in Fused Deposition Modeling of  Three-Dimensional Printing Based on Wavelet Neural Network JI Liangbo 2015, 49 (03):  375-378.  Abstract ( 872 )   Save Abstract： Technological parameters in fused deposition modeling three-dimensional printing are coupled and the forming process is a non-linear forming process. A large number of modeling parameters affect the quality of the product precision in fused deposition modeling of three-dimensional printing. In order to clarify the effects of various parameters on the forming precision and improve the precision of three-dimensional printing, the wavelet neural network prediction model of product precision was build by using the Matlab software. The arithmetic was designed and the samples were acquired by fused deposition modeling experiment. The training samples were used to train the network to accomplish the mapping relation between the input and output of the network. The test samples were used to verify the performance of the trained network. Simulation results indicate that the prediction model has sufficient accuracy. The prediction model of product precision is feasible and valid in theory and in practice. The wavelet neural network method was used to model the relation between the processing parameters and the product precision in fused deposition modeling of threedimensional printing. The difficult problem to create the accurate mathematics model was solved.   References | Related Articles | Metrics

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Motion State Detection Technique for WallClimbing Robot Base on Two Degree of Freedom Universal Wheel Mechanism ZHENG Jun，QIU Qiang，LI Peng，PAN Jiluan 2015, 49 (03):  379-382.  Abstract ( 1023 )   Save Abstract： The speed measuring mechanism base on two degree freedom universal wheel was designed, which consisted of a two degree of freedom roller, a rotary encoder, an angular displacement sensor and a horizontal attitude sensor and so on. When the robot moved, its attitude angle and angular velocity were detected by the level posture sensor, its velocity direction was detected by the angle sensor, and its speed was measured by the photoelectric encoder, thus, the motion state of the robot can be obtained by this measuring device, and the relationship between the motor input and control point motion was also established, provide basis for the precise operation of the robot. References | Related Articles | Metrics

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Ant Colony Algorithm for Solving Discrete Minimum Constraint Removal (MCR) Problem XU Bo，MIN Huaqing，XIAO Fangxiong 2015, 49 (03):  383-386.  Abstract ( 1107 )   Save Abstract： This paper introduces the ant colony algorithm to solve the minimum constraint removal (MCR) problem. The inspired function and pheromone update strategy of the ant colony algorithm(ACO) were improved in the solving process, so that it is no longer easy to fall into local extremum. The simulation results show that the solution quality and convergence rate of the algorithm is better than those of the precise search and greedy algorithm. Key words： References | Related Articles | Metrics

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Combinatorial Optimization of Spray Painting Robot Tool Trajectory Based on Improved Membership Cloud Models Ant Colony Algorithm LI Cuiming，GONG Jun，NIU Wancai，WANG Chong 2015, 49 (03):  387-391.  Abstract ( 971 )   Save Abstract： Aimed at the combinatorial optimization of tool trajectory upon the complex freeform curved surface piece, Hamiltonian path was adopted to transform it to an open traveling salesman problem (OTSP). Meanwhile the strategy of integrating the problemunrelated optimization algorithm and the problemrelated local search was adopted. First, the membership cloud models were introduced to adapt and adjust the randomness controlled by the ant colony algorithm. Then, the Kopt partial search strategy was introduced to find the solution to OTSP in respect of the combinatorial optimization of the tool trajectory based on the improved membership cloud models ant colony algorithm (MCMACA). The simulation result shows that MCMACA features better global search ability and local convergence. Meanwhile, it has obvious advantages in terms of optimization of the spray painting robot tool trajectory on complex curved surface. References | Related Articles | Metrics

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Hand-Eye Calibration in Robot Welding of Aero Tube ZHANG Zongyu1,GAO Hongming1,HAN Qinglin1,HUANG Rui2 RONG Jian2,WANG Yongchao2 2015, 49 (03):  392-394.  Abstract ( 1028 )   Save Abstract： Based on the current domestic situation that the welding of aero tube is mainly the manual gas tungsten arc welding, a digital welding of aero tube was proposed. The hand-eye calibration of robot involved in the system was studied. By establishing the camera coordinate system in the installation distance of META seam tracking sensor, the handeye calibration is completed using a three dimensional measuring machine. The results show that the calibration accuracy of this method is ±0.4 mm, which meets the requirement of the digital welding of aero tube. References | Related Articles | Metrics

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Design of a Coaxial Welding Torch with Visual Sensor and Its Application CHEN Xizhang,YU Jie,HU Chao 2015, 49 (03):  395-397.  Abstract ( 776 )   Save  Abstract： For the issues of structural redundancy, interference of the welding torch and images deviation from the center of weld pool caused by separation between the welding monitoring system and torch, a coaxial welding torch with visual function (coaxial integration with the visual function, CIV) was designed, whose camera is coaxial to the tungsten electrode, installed in the interior of the welding torch, which can provide real time monitoring of the welding processing. Innovation design of the tungsten electrode regulating system simplifies the regulation of tungsten electrode. The cooling and protection system were integrated, which has a dramatically effect on welding gun cooling and gas shielding. It not only optimizes the structure of the welding torch, but also improves the accessibility of the welding gun. The result shows that a very central pool image of tungsten and the exact positions of tungsten and welding stick can be obtained by the structure of the CIV torch. The structure of CIV torch is more advantageous in the applications of seam tracking, process monitoring. References | Related Articles | Metrics

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Multi-Focus Welding Pool Image Fusion Based on Wavelet Transform of Double Arc Welding of Magnesium Alloy ZHANG Yugang1a,MA Guohong1a,CUI Yong1a，YE Jia2，JIANG Furong1b 2015, 49 (03):  398-401.  Abstract ( 724 )   Save Abstract： Aimed at the selection of the multi-focus image fusion rule of double arc welding of magnesium alloy, a fusion rule was proposed based on windows for choosing wavelet low frequency coefficient. The fusion rule gave full consideration of the contribution of the low frequency component to the fused image and the correlation between image pixels. To the experimental results and objective evaluation indicates that the proposed algorithm can have a better fusion effect, a clear object and fusion pool edge information of the multifocus image fusion of double arc welding of magnesium alloy. References | Related Articles | Metrics

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Configurable Fault Diagnosis Model in Induction Motor NIE Binga,ZHAO Huimina,DING Mingyanb,LI Wena 2015, 49 (03):  402-405.  Abstract ( 622 )   Save Abstract： Based on the research on typical fault diagnosis model, a configurable diagnosis model of induction motor was proposed to resolve the problem of complexity of network and difficulty of training. This model contains multiple sub RBF neural networks which have multiple inputs and single output, and one type of fault can be recognized by a specific sub-model. The sub-models can be any combination based on the demands of the system, and various faults can be identified. The model is trained using the samples with feature extracted, and the effectiveness of fault diagnosis model is verified through test samples. It is shown that one sub-model can be used to recognize one specific state of motor in the configured fault diagnosis model, the structure is simple, the difficulty of model training is reduced, the fault identification capability of model and flexibility of application are improved,  providing a new method for the induction motor fault diagnosis. References | Related Articles | Metrics

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Application of Improved Secondary 1.5-D Spectrum Estimation in Pipeline Inner Inspection TANG Jian1,2,JIAO Xiangdong2,DAI Bo2 2015, 49 (03):  406-410.  Abstract ( 820 )   Save Abstract： Aimed at the problem that the manual wall thickness acquisition algorithm has the disadvantages of large labor intensity, low efficiency, and so on, and the fact that the existing automatic wall thickness acquisition algorithm is not accurate and adaptable, the automatic wall thickness acquisition algorithm based on the improved secondary 1.5-D spectrum estimation was proposed. The pipeline ultrasonic A-wave signals were estimated by 1.5-D spectrum that were intercepted and filled zero by the upper and lower limit of the wall thickness. Then, the 1.5-D spectrum estimation was done again, and the wall thickness information was obtained. Experimental results show that  the wall thickness data generated by this algorithm is more accurate and the relative error is within 3%. References | Related Articles | Metrics