制造技术与机床

Research on parameters of flow regulators based on closed hydrostatic guideway of ultra-precision lathe

LI Xiaohui

2023, (8): 5-12, 31. doi: 10.19287/j.mtmt.1005-2402.2023.08.001

[Abstract] FullText HTML PDF(2661KB)

Abstract:
According to the coupling relationship between slider and flow regulators,the hydraulic circuits are drawn, the mathematics models are established, the influence of regulator parameters on static and dynamic characteristic of closed hydrostatic guideway which has opposite differential rectangle chamber are analyzed. This research obtains the combination mode of regulators, the best resistance ratio, the methods to optimize, the equality relation between the resistance ratio which of single film's and support chamber's and the resistance ratio which of single film's and parallel loop's, the influence of preload loop's resistance on guideway stability, provides reference and ways to regulators design and test.

Experimental study on microgrinding characteristic signal sensing of single crystal materials based on acoustic emission monitoring

ZHANG Yuexia, QU Yingying, LI Feng

2023, (8): 13-18. doi: 10.19287/j.mtmt.1005-2402.2023.08.002

[Abstract] FullText HTML PDF(1586KB)

Abstract:
The acoustic emission signal sensing of nickel-based crystal microgrinding was measured. The monitoring system of acoustic emission signal is established, the characteristic parameters are extracted from the signal and the division of frequency band is completed. The correlation degree between acoustic emission signal time domain root mean square spectrum and frequency band signal energy ratio predicted unsteady grinding characteristics is deeply discussed. The results show that the wear form of the micro-abrasive tool changes from the initial rapid wear process to the stable wear state after the grinding length increases gradually. With the increase of material removal amount, a larger diameter loss amount was formed, and the overall performance was first rising and then stable state change. There is a positive correlation between the energy ratio of middle band and the diameter loss of microabrasives. The energy ratio of high frequency band is positively correlated with the width of micro-slot edge breakage. Microgroove taper Angle usually presents continuous change characteristics, forming a larger microgroove taper angle. With the increasing of grinding depth, the diameter loss of micro-abrasive tools and the correlation coefficient of energy ratio in middle frequency band are increased, while the correlation coefficient of micro-groove edge breakage width and energy ratio in high frequency band are decreased.

Selective laser melting quality prediction based on adaptive GDSA-BPNN

DONG Hai, SONG Yufei

2023, (8): 19-26. doi: 10.19287/j.mtmt.1005-2402.2023.08.003

[Abstract] FullText HTML PDF(1323KB)

Abstract:
To solve the quality defect problem of selected laser melting(SLM) parts in additive manufacturing, a new adaptive multi-input and multi-output Back Propagation Neural Network(BPNN) was proposed to predict SLM product quality and solve the problem that the traditional method can not adapt the hyperparameter to different search stages. Firstly, the important process parameters and quality indexes of SLM molding were determined, Huber function was selected as the loss function of BP model, and BP model containing the objective function of structural risk minimization strategy was constructed. Secondly, a prediction model (GDSA-BPNN) based on the combination of the Gradient Descent Search Algorithm (GDSA) and BPNN was established. Three strategies with different learningrates were selected and put intothe adaptivestrategy library,and an adaptive mechanism was used to optimize the hyperparameters of BP model. Finally, the prediction results of GDSA-BPNNmodelwere compared with those of other four models, and the results show that the prediction accuracy of SLM parts quality prediction method based on GDSA-BPNN model has good prediction effect and high prediction accuracy.

Research on deformation and residual stress for overhanging structure of semi-circular hole by selective laser melting

JIANG Xu, ZHOU Liuru, BI Fengyang, LIU Changxi, LI Panpan

2023, (8): 27-31. doi: 10.19287/j.mtmt.1005-2402.2023.08.004

[Abstract] FullText HTML PDF(1568KB)

Abstract:
The simulation model of unsupported semi-circular hole overhanging structure of SLM formed AlSi10Mg alloy was established based on Simufact additive. The total distortion and residual stress in different processes were analyzed. The effects of geometric parameter thickness and inner and outer circle radius on the max total distortion and max residual stress were studied. The results show that the max total distortion and the max residual stress increase with the increase of the thickness of the semi-circular hole; the radius of the inner circle of the semi-circular hole becomes larger, and the max total distortion tends to increase; the outer radius of the semi-circular hole becomes larger, and the max total distortion decreases, but it has little effect on the total distortion.

Integrated scheduling optimization of two resources in flexible job-shop based on niche genetic

LIU Zhifei, MA Kexin

2023, (8): 32-38. doi: 10.19287/j.mtmt.1005-2402.2023.08.005

[Abstract] FullText HTML PDF(2007KB)

Abstract:
Aiming at the integrated scheduling problem of production and logistics resources in flexible workshop, a niche adaptive genetic algorithm based integrated scheduling method is proposed. First of all, logistics process, path conflict elimination method and allocation strategy of the AGV in flexible workshop are defined. Secondly, the integrated scheduling problem of workshop production and logistics resources is described, and an optimization model aiming at the shortest completion time is established. Then, the niche technology and adaptive strategy are introduced into the genetic algorithm to make the genetic strategy change with niche characteristics adaptively. And a new niche adaptive genetic algorithm (NAGA) is proposed. Finally, a niche adaptive genetic algorithm based two-resource integrated scheduling process is developed. Through experimental verification, the completion time of niche adaptive genetic algorithm scheduling is shorter than that of genetic algorithm (GA) and improved distribution estimation (IEDA) algorithm in literature [1], which indicates that the integrated scheduling performance of NAGA algorithm is better than that of GA algorithm and IEDA algorithm. According to the impact analysis of the number of AGVs, the completion time of the workshop decreases with the increase of the number of AGVs, and the completion time does not decline when the number of AGVs is saturated.

Intelligent drawing method and system of 3D model based on SolidWorks

ZHI Chenyu, FANG Xifeng, ZHU Yonghui, LUO Lanzhen

2023, (8): 39-46. doi: 10.19287/j.mtmt.1005-2402.2023.08.006

[Abstract] FullText HTML PDF(1760KB)

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In order to improve the efficiency of engineering drawing, reduce simple and repetitive drawing work, and ensure the standardization of engineering drawing on the basis of realizing intelligent drawing, machine learning is proposed to be applied to engineering drawing. Text similarity retrieval technology, image similarity retrieval technology and KNN algorithm are used in the secondary development of SolidWorks.Combined with Python and VB.net, the engineering drawing view is automatically selected, the drawing sheet is intelligently selected, and the proportion and position of the view are adjusted to ensure the correctness of the view selection, the standardization of the size and the rationality of the layout, saving a lot of manual drawing time.

Research on hybrid Seru production scheduling based on improved slime mold optimization algorithm

ZHANG Tianrui, CONG Sirui

2023, (8): 47-55. doi: 10.19287/j.mtmt.1005-2402.2023.08.007

[Abstract] FullText HTML PDF(1640KB)

Abstract:
With the increasingly significant market demand for customized production, Seru production system (SPS) came into being and has gradually become a hot spot in the field of production research. In this paper, the construction and scheduling problems of hybrid Seru production system are studied. That is, in the production scene of short production line, the mathematical model of hybrid Seru production system is established based on itinerant Seru unit, and double optimization objectives are established with the maximum completion time and total working hours to decide the construction sequence of hybrid Seru. First, based on the slime mold optimization algorithm, aiming at the limitations of its low initialization efficiency, Tent chaotic mapping and elite reverse learning strategy were introduced to obtain the Chaotic elite Slime mold algorithm (CESMA). Finally, the superiority of chaotic elite slime mold algorithm to the hybrid Seru production system is verified by experiments.

Research on design and simulation of high precision fitting forming milling tool edge

XU Chen, HONG Rongjing, GAO Han, LI Weiyuan, LI Shuaikang

2023, (8): 56-62. doi: 10.19287/j.mtmt.1005-2402.2023.08.008

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Abstract:
Forming milling cutter is used to mill large modulus gears, and the fitting accuracy of its blade type directly affects the accuracy of the machined tooth surface. Aiming at the problem of low precision of gear tooth profile machined by forming milling cutter, a method of high precision fitting of helical gear milling cutter edge shape by small segment NURBS is proposed. Based on the principle of gear meshing, the mathematical model of helical gear tooth surface is established by MATLAB. The contact line and tool edge point of helical gear milling are obtained by coordinate transformation. The traditional single arc fitting, piecewise cubic fitting and small piecewise NURBS fitting are carried out on the edge point to obtain different precision tool edge types. In order to verify the machining accuracy of small piecewise NURBS fitting edge, VERICUT is used to form milling of different precision edge tools, and compared with the standard helical gear profile. The research shows that the precision of the machined tooth surface is improved by the small segmented NURBS fitting edge tool.

Research on prediction method of grinding surface roughness based on numerical modeling

JI Ning, FENG Jianhai, SUN Zhonghua, ZHAO Honglin, JIANG Jinhua, JIA Chenyang

2023, (8): 63-69, 88. doi: 10.19287/j.mtmt.1005-2402.2023.08.009

[Abstract] FullText HTML PDF(3745KB)

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Grinding surface roughness is an important evaluation index to characterize grinding quality, and grinding micro-surface topography is an important factor to determine surface roughness. It is difficult to predict the grinding micro-surface topography and roughness of workpiece in advance based on experience. To solve this problem, a method based on numerical modeling and experiment was proposed to predict grinding surface roughness. Taking the needle valve body in the precision coupling of the injector nozzle as the research object, a numerical model of the grinding wheel was established based on the fact that the height of the grinding grains obey the normal distribution. On this basis, the grinding microscopic surface topography was generated by establishing the motion trajectory equation of grinding grains on the surface of the grinding wheel, and the surface roughness was accurately calculated. Finally, the effectiveness of the method proposed in this paper was verified by grinding experiments. The method proposed in this paper can provide method support for efficient, high quality and low cost processing of needle valve body.

Investigation on interfacial machining characteristics of variable parameters helical milling for CFRP/Titanium alloy laminated structures

YU Hui, MA Lijie, MAO Xinhui, MA Zunyan, PANG Minghua, WANG Zhankui

2023, (8): 70-78. doi: 10.19287/j.mtmt.1005-2402.2023.08.010

[Abstract] FullText HTML PDF(2655KB)

Abstract:
Helical milling is a common hole-making technique for CFRP/Titanium alloy laminated structural parts, however, the difference in cutting performances between two materials makes it difficult to guarantee machining quality with a single parameter. In this paper, a variable parameters helical milling technique was proposed to meet the practical demand for precision hole-making of laminated structures. By analyzing the transitional thrust force, the interfacial quality and the interfacial aperture, the influence of hole-making sequence and variable parameters position on the interfacial machining characteristics was investigated deeply. The results indicate that, the hole-making sequence had a significant influence on the transitional thrust force, the interfacial machining quality and the interfacial hole accuracy, while the variable parameter position mainly affected the interfacial quality. The optimal interfacial quality could be achieved by the use of C/Ti-C hole-making scheme, with an interfacial flatness factor of only 8% of the Ti/C-Ti method. And the smallest difference in the interfacial aperture between CFRP and Titanium alloy was achieved, only 29 μm, with the Ti/C hole-making sequence. Based on the comprehensive consideration of interfacial quality and dimensional accuracy, the C/Ti-C variable parameters scheme should be chosen.

Stress analysis and fatigue strength evaluation of flexsplines of industrial robot harmonic reducer

YU Xian, LIANG Xuexiu, GONG Xiao, XIAO Ke, HAN Yanfeng

2023, (8): 79-82. doi: 10.19287/j.mtmt.1005-2402.2023.08.011

[Abstract] FullText HTML PDF(1199KB)

Abstract:
In order to study the fatigue fracture failure in the flexsplines of the industrial robot harmonic reducers, the model based on cylindrical shell theory was used to evaluate the circumferential distribution of stress in the flexsplines and the effects of load, wall thickness and diameter on the stress was also analyzed. The result shows that the stress is more sensitive to the wall thickness than the diameter of flexsplines,while the load torque has little effect on the axial and circumferential stress in the flexsplines. Stress of the flexsplines mainly comes from the circumferential bending deformation forced by the wave generator, it also comes from the axial bending deformation and the torsional deformation. Finally,the evaluation method of fatigue failure strength in the flexsplines was proposed based on the study.

Mechanical properties analysis of double clutch precision planetary gear reducer based on Romax

QI Na, WANG Shijun, DU Yaning, WANG Cheng, WANG Guanzhong, RAN Chuandong

2023, (8): 83-88. doi: 10.19287/j.mtmt.1005-2402.2023.08.012

[Abstract] FullText HTML PDF(2598KB)

Abstract:
Taking the double clutch precision planetary gear reducer used in a numerical control vertical lathe as the research object, the reducer simulation model was established by Romax Designer software, and the transmission system was analyzed statically. The input shaft and output shaft meet the strength requirements, the bearing meets the life requirements, and the contact fatigue strength and bending fatigue of the gear meet the design requirements. The modal analysis of the planetary shelf is carried out by Ansys software, and the first six constraint modes, natural frequency and modal mode characteristics are obtained. Taking the transmission error as the vibration excitation source, the advanced roar analysis of planetary gear reducer is carried out, and the vibration acceleration is the largest in the Y direction. Finally, by ODS analysis, the deformation of flexural mode in Y direction is 0.96μm. This study provides theoretical data for gear modification, vibration reduction and noise reduction.

Engineering design and analysis of EHL for involute cylindrical spur gear transmission

CAO Dongjiang, YIN Feixing

2023, (8): 89-99. doi: 10.19287/j.mtmt.1005-2402.2023.08.013

[Abstract] FullText HTML PDF(2370KB)

Abstract:
Through the analysis of gear lubrication mechanism, the change law of relative sliding speed on the meshing line of gear pair is revealed. According to Dowson-Higginson's empirical formula of minimum oil film, the laws of equivalent curvature radius and entrainment speed changing with transmission ratio and modification coefficient, which are key factors affecting gear lubrication performance, are analyzed. Based on accurate tooth profile, the distribution of tooth surface load along the meshing line is calculated. The influence of gear design parameters such as transmission ratio, modification coefficient, pressure angle and center distance on the minimum oil film thickness of gear pair is analyzed by programming and calculating the corresponding relationship curves. The results show that the transmission ratio makes the minimum oil film thickness curve incline and rotate, the modification coefficient determines the starting and ending points of the film thickness curve along the meshing line, and causes the change of the center distance of the gear pair to indirectly affect the minimum film thickness. The relationship between the center distance, pressure angle and the minimum film thickness is positive correlation. Finally, the gear lubrication state is judged according to the film thickness ratio relationship. It can be seen from the calculation curve of an example that the minimum oil film thickness point of the gear pair does not occur at the meshing point of the pinion tooth root and the big gear tooth top, so the oil film thickness ratio of the meshing node is used to determine the gear lubrication state. The above conclusion provides a reference for the design of elastohydrodynamic lubrication of gear transmission.

Research on GH4169/K418B composite and functionally gradient materials

WANG Zhenzhong, XIAO Yuhang, GAO Kai, HUANG Xuepeng

2023, (8): 100-107. doi: 10.19287/j.mtmt.1005-2402.2023.08.014

[Abstract] FullText HTML PDF(4085KB)

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Based on the laser coaxial powder feeding LENS method, the composite materials and functional gradient materials of GH4169/K418B were prepared. The elastic modulus of GH4169/K418B was increased by 64.1% when the ratio of GH4169/K418B was 80%/20% compared with the pure GH4169. The yield strength was increased by 22.8%, the tensile strength was increased by 23.5%. When the proportion of K418B exceeded the threshold, the mechanical properties of functional gradient materials was significantly reduced. Due to the gradient characteristics of its composition, the performance of GH4169/K418B functionally mradient aterials showed the “learning from each other”. Its elastic modulus of 80.1 GPa, yield strength of 567.67 MPa, tensile strength of 790 MPa, the performance is at the excellent level of each composite material, can be applied to the aerospace field has certain requirements for various performance of the complex scene.

PMSM speed control based on new fractional-order sliding mode

REN Jinxia, HE Mingyan, YAO Guanghui

2023, (8): 108-112. doi: 10.19287/j.mtmt.1005-2402.2023.08.015

[Abstract] FullText HTML PDF(1439KB)

Abstract:
Aiming at the problems of steady-state error and large buffeting degree in the speed control system of permanent magnet synchronous motor (PMSM), a new frit-order sliding mode speed controller was designed to replace the traditional sliding mode speed controller. By studying the theory of fraction-order control and combining with the general exponential approach rate function, a new fraction-order approach rate is designed, and the traditional sign function is replaced by arctangent trigonometric function. The extended state observer is used to estimate the total disturbance error of the system and obtain accurate rotor velocity information. Lyapunov stability criterion is used to prove the feasibility of the scheme. Finally, under the same motor parameters, a simulation model was built and simulated according to the PMSM system control block diagram, and the performance indexes of the traditional sliding mode control were compared. The experimental results show that the motor system with the new fractional sliding mode controller can respond quickly, improve the anti-interference ability, and the system stability and robustness are better.

Research on welding torch height tracking system based on fuzzy PID

TIAN Yaohua, XUE Ruilei, WU Libin, LI Xiaojuan, LIU Hongsheng

2023, (8): 113-118. doi: 10.19287/j.mtmt.1005-2402.2023.08.016

[Abstract] FullText HTML PDF(1520KB)

Abstract:
A new algorithm for extracting the torch high and low tracking deviation - the "adaptive substitution learning method" - is proposed based on the analysis and improvement of the welding current standard value setting method in the welding torch high and low tracking method. In addition, an adaptive variable domain fuzzy PID control method is designed, which introduces the variable domain into the fuzzy control to achieve adaptive tuning of the control parameters. The PID is then employed as the controller to achieve accurate output of the high and low deviation control amount of the welding torch. The experimental results demonstrate that the adaptive substitution learning method has a maximum extraction deviation of 0.24 mm, while the adaptive variable domain fuzzy PID control method has a maximum tracking error of 0.32 mm. These methods enable real-time and accurate control of the welding torch height in pipeline welding processes, satisfying the welding requirements of pipeline laying.

Research on oil monitoring data modelling and prediction based on grey theory

WU Feng, JIANG Pei, DU Lulu

2023, (8): 119-123. doi: 10.19287/j.mtmt.1005-2402.2023.08.017

[Abstract] FullText HTML PDF(887KB)

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Accurate modeling and prediction of oil debris monitoring data for equipment power systems plays an important role in evaluation of the health status of power systems and ensuring their normal operation. An improved two-step GM (1,1) modeling method for non equidistant sampling of oil monitoring parameters, which is often encountered in engineering practice, is studied. This method is not only suitable for high growth sequence, but also has high model accuracy. Based on this method, the grey prediction model of oil wear particle number is established and the prediction accuracy is compared with that of the non-equidistance modeling accuracy of data transformation method. The results show that the former has higher accuracy and is more suitable for the short-term prediction of oil wear particle number trend.

Study on consistency of residual pre-tightening force of bolt group

JIA Zhe, WENG Zhiwei, ZHANG Song

2023, (8): 124-132. doi: 10.19287/j.mtmt.1005-2402.2023.08.018

[Abstract] FullText HTML PDF(2361KB)

Abstract:
Aiming at the problem of poor consistency of residual pre-tightening force of bolt group in CNC machine tools assembly, an experimental bench was set up to study the effect of tightening sequence and step tightening strategies on residual pre-tightening of bolt group. First, based on the common four-bolt connection structure in machine tools, the experiment part of four-bolt connection structure is designed and fabricated. Secondly, an experiment platform was built to analyze the influence of tightening sequence and step tightening strategy on the residual pre-tightening force of the four-bolt connection structure. Finally, the two step tightening strategies are compared and analyzed. The results show that: among the three tightening sequences, the residual pre-tightening force consistency of the four-bolt connection structure is the best under the clockwise tightening condition. With the increase of tightening steps, the consistency of residual pre-tightening force of bolt group becomes better, but with the continues to increase of tightening steps, the consistency of residual pre-tightening force does not improve significantly. The consistency of the residual pre-tightening force of the bolt group becomes better with the increase of the first step tightening proportion, while the consistency of the residual pre-tightening force does not improve significantly with the continuous to increase of the first step tightening proportion. This study can provide guidance for improving machine tools assembly quality and bolt pre-tightening effect.

Simulation and experimental research on friction stir welding of large thickness aluminum alloys

JIANG Xiaohui, YAO Mengcan, ZHANG Yi, GUO Weicheng, HOU Chunjie

2023, (8): 133-140. doi: 10.19287/j.mtmt.1005-2402.2023.08.019

[Abstract] FullText HTML PDF(2764KB)

Abstract:
In order to meet the requirement of friction stir welding joint for 7050 aluminum alloy plate with 10 mm thickness, an arbitrary Lagrange-Olah model was established, which was combined with simulation analysis and experimental research, the distribution law of joint temperature field under rotating speed, welding speed and welding time was analyzed. The thermal cycle curves of the measured temperature and the characteristic points are in good agreement, indicating that the numerical simulation can be used to predict the distribution pattern of the temperature field. The results show that the temperature field distribution of the weld cross-section under different welding parameters are bowl-shaped. The peak temperature at each location point increases with increasing rotational speed and decreasing welding speed, where the rotational speed has a more significant effect on the peak temperature. Finally, the experimental verification of the mechanical properties of the joint under three groups of process parameters, found that 800 r/min, 1.6 mm/s group of parameters under the better tensile properties, the study method for the determination of large thickness of light alloy stir friction welding process provides a reference.

Research on flow-solid coupling characteristics of deep small hole gaps by short electric arc-electrolysis composite machining

MA Xinyang, CHEN Xiaokang, WANG Kedian, ZHOU Jianping

2023, (8): 141-145. doi: 10.19287/j.mtmt.1005-2402.2023.08.020

[Abstract] FullText HTML PDF(1648KB)

Abstract:
In view of the problems of high quality requirements, small hole diameter, large number of holes and difficult processing, this paper proposes a short electric arc-electrolysis compound machining method for deep and small holes. Short electric arc-electrolysis machining has the advantages of material-independent, high processing efficiency and good surface quality, but due to the large flexibility of the cathode for deep and small hole machining, the processing is easy to shake and the arc discharge energy can cause poor chip discharge, short circuit and secondary discharge problems. In view of the above problems, this paper investigates the flow-solid coupling characteristics of deep and small holes by short electric arc-electrolysis compound machining. From the perspective of the gap flow field, the motion characteristics of the gap flow field under different feed rates and different machining depths are studied, and experiments are designed to verify the simulation results. The results show that in a certain range, the faster the feeding speed of short electric arc-electrolysis composite machining, the faster the average motion speed of interpolar medium, the more uniform the particle distribution, and the better the chip removal effect, therefore, by increasing the feeding speed can promote chip removal and improve the stability of short electric arc-electrolysis composite machining.

Process architecture and planning methods of mobile robot for large spacecraft capsule

LIU Baorong, YANG Jizhi, LI Haiou, WANG Yunpeng, WEN Ke, ZHOU Yinghao, HE Yuqing

2023, (8): 146-154. doi: 10.19287/j.mtmt.1005-2402.2023.08.021

[Abstract] FullText HTML PDF(2692KB)

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Mobile robot processing technology provides a new technical means for the manufacture of large spacecraft capsule. Compared with the traditional manufacturing process based on CNC machine tools, there is a lack of a systematic framework and method for machining process planning. For this reason, taking the processing of large spacecraft capsule as an example, a process architecture of mobile robot system processing is proposed. Based on the overall process flow of large spacecraft capsule manufacturing, the task flow for mobile robots is combed, and the robot processing process elements are comprehensively summarized and optimized according to the requirements of tool distribution at the production site. At the same time, facing the practical needs of precision control and task allocation in mobile robot processing, three typical problems in process planning process, including hierarchical precision control, station planning and processing space partition splicing, are introduced in detail and specific solutions are given. Finally, taking a capsule as the processing object, the case verification of processing planning for mobile robot is completed. The results show that it can provide technical guidance for high-precision and high-efficiency machining of large spacecraft cabin using mobile robots.

Research and analysis on vibration characteristics of large annular aluminum alloy parts

CUI Xin, LI Junwen, LIU qiang

2023, (8): 155-160. doi: 10.19287/j.mtmt.1005-2402.2023.08.022

[Abstract] FullText HTML PDF(1318KB)

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In this paper, aiming at the vibration characteristics of a large annular aluminum alloy part, a three-dimensional model is established, and the modal analysis and harmonious response analysis are carried out based on finite element software. The natural frequencies and vibration modes of annular aluminum alloy parts are obtained from the modal analysis results. On the basis of modal analysis, the harmonic response analysis is carried out, and the response curves of displacement and frequency, acceleration and frequency are obtained, and the resonance phenomenon in the range of 0~140Hz is analyzed. The analysis conclusion provides an important theoretical reference for the selection of vibration aging process parameters of large annular aluminum alloy parts, and has certain engineering application value.

Detection method of key parameters of small external thread based on machine vision

DAI Guocheng, LUO Zai, JIANG Wensong, WEI Hengzheng

2023, (8): 161-165. doi: 10.19287/j.mtmt.1005-2402.2023.08.023

[Abstract] FullText HTML PDF(2195KB)

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Aiming at the difficult problem of measuring small size external threads, a method for measuring key parameters of threads based on machine vision was proposed to obtain accurate information about the edge of the external thread profile, which solved the problem that the scanning probe tip was too large to measure small size threads. Firstly, a median filter was used for preprocessing to remove salt and pepper noise and pulse interference contained in the image, and Otsu was used to select the optimal threshold value to binarize the image. An improved Gaussian filter and adaptive threshold canny operator were used to extract the contour edge of the thread. At the same time, a minimum rectangle fitting algorithm for the measurement area was designed to correct the inclination angle of the screw image. Finally, the least square linear fitting method was used to calculate the dimension parameters of the thread. The experimental results showed that the measuring accuracy of the screw pitch and the middle diameter of the thread reached 0.001 4 mm and 0.002 7 mm, which realized the high precision measurement of the key parameters of the thread.

Research on visual detection method of cylinder head forging defects based on improved YOLOv5

TANG Yu, FANG Kai, YANG Shuai, WANG Chen, LI Zongliang

2023, (8): 166-173. doi: 10.19287/j.mtmt.1005-2402.2023.08.024

[Abstract] FullText HTML PDF(1902KB)

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Various types of cracks are prone to be produced in the production process of automotive cylinder head forgings, which affect the product quality. An improved algorithm model YOLOv5-MG based on the YOLOv5 network is proposed to address the current problem of low accuracy and efficiency in detecting defects in cylinder head forgings. Firstly, a sample dataset of cylinder head forgings defects is produced by building an image acquisition platform. Then, the accuracy and efficiency of the model are improved by replacing the YOLOv5 Head architecture of the SPP-YOLO network with the Decoupled Head structure; the fusion of shallow feature information with deeper feature information is enhanced by replacing the original path aggregation network (PANet) of the YOLOv5 network with the bidirectional feature pyramid network (BFPN); and the localization accuracy of the algorithm is improved by introducing the computation method of complete intersection over union (CIoU). 99.81% mean accuracy, 0.99 F1 score and 17.2 B floating point operations (FLOPs) are achieved by the improved algorithm on the test set.

Evaluation of crankshaft roundness error based on computational geometry

CAO Ying, HOU Yinglin, ZHANG Shengchuan, DING Shuokun, DOU Yaping, LI Changan

2023, (8): 174-179. doi: 10.19287/j.mtmt.1005-2402.2023.08.025

[Abstract] FullText HTML PDF(2263KB)

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Aiming at the problem in improving the efficiency of crankshaft roundness error measurement, a method of visual measurement which was used in the detection of crankshaft roundness error based on convex hull was proposed. Firstly, the camera calibration and distortion correction of roundness visual evaluation system were carried out, and the designed acquisition system was used to obtain the rotating image of the crankshaft in real time. Then, the edge coordinates were extracted by noise removal and sub-pixel edge detection, and the discrete data points were obtained by three-dimensional reconstruction. Finally, a roundness evaluation model based on computational geometry technology was proposed, and the data in literature were used for simulation verification. The results of crankshaft roundness error of CMM are taken as standard values to compare and verify the proposed methods. The results show that the mean absolute error of machine vision inspection results compared with CMM is 3.39 μm. It proves that the visual evaluation method of roundness error has high accuracy, and can be applied to the evaluation of crankshaft roundness.

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