- Online First |
- Publishing |
- Current Issue |
- Special Articles |
- Archive
-
YANG Xi, TIAN Chong, FANG Ruyi, LIU Zeyu, ZHANG Yinhang, LEI Kejun
Available online:May 19, 2022 DOI: 10.16339/j.cnki.hdxbzkb.2022353
Abstract:The classical maximum eigenvalue detection (MED) algorithm has excellent performance in detecting correlated signals. However, with the increasing signal dimensionality, the MED algorithm faces serious problems in the calculation efficiency and implementation of test statistic and decision threshold, thus greatly limiting the further application of the algorithm in modern cognitive communication systems. To this end, a low-implementation complexity MED algorithm based on a numerical analysis theoretical framework is proposed. The new algorithm uses the Rayleigh quotient accelerated power method to iteratively compute the test statistic, which has a fast convergence rate in detecting high-dimensional signals compared with the classical power method; meanwhile, different from the classical look-up table method, a threshold calculation method based on the cubic spline interpolation method is proposed, which can quickly determine the decision threshold corresponding to any given target false-alarm probability. The proposed MED algorithm effectively improves the computational efficiency and reduces the complexity of algorithm implementation while maintaining the detection performance of the original algorithm, which is particularly attractive for spectrum sensing problems in high-dimensional conditions. Finally, the simulation results demonstrate the effectiveness of the proposed algorithm.
-
Available online:May 19, 2022 DOI: 10.16339/j.cnki.hdxbzkb.2022355
Abstract:A terahertz fundamental up-conversion mixer with a high local oscillator (LO)/ radio frequency (RF) and local oscillator / intermediate frequency (IF) port isolation was presented, which was in the IHP 0.13μm SiGe BiCMOS process. The mixer adopted Gilbert’s double-balanced structure, local oscillator signal was transmitted through the Coplanar Waveguide (CPW) to suppress the transmission asymmetry caused by the strong parasitic coupling effect in the transmission process, which reduced the characteristic of LO/RF port isolation deterioration caused by the asymmetry. By adopting an asymmetric switch interconnection structure, the imbalance of the parasitic coupling of the local oscillator signal at the collectors of the switching transistors was reduced, and the cancellation efficiency of the local oscillator signal at the collectors of the switching transistors was improved. And the local oscillator signal was suppressed at the port of intermediate frequency by arranging the position of the transconductance transistors in a reasonable layout. The post-simulation results show that under the power supply voltage of 2.2V, the local oscillator signal is 230GHz and the intermediate frequency signal is 2-12GHz, when the up-conversion mixer works at 218-228GHz, the LO/RF port isolation is greater than 24dB, LO/IF port isolation is greater than 20dB, the conversion gain is -4dB to-3.4dB. The output 1dB compression point is -14.8dBm with an intermediate frequency signal is 10GHz. The DC power consumption is 42.4mW, the core area of the chip is 0.079mm2.
-
YUAN Yongjie, YANG Liang, CHEN Shenghai, MA Rongchang
Available online:May 17, 2022 DOI: 10.16339/j.cnki.hdxbzkb.2022296
Abstract:Free space optical (FSO) communications offer high speed, low cost, and strong anti-interference ability. However, the atmospheric turbulence-induced fading causes deterioration in the performance of FSO communication systems. The conventional solution is to use RF links as parallel communication links to improve the system performance. On the other hand, reconfigurable intelligent surfaces (RIS) can be employed to further improve the received signal-to-noise ratio of the RF link due to its advantages of low loss, easy deployment, and no complex coding and decoding. In this paper, an RIS-assisted hybrid RF-FSO transmission system is proposed to improve the communication quality of service. Based on this hybrid model, exact expressions for the outage probability, average BER, and channel capacity are derived, and Monte-Carlo simulations are presented to verify the accuracy of the analytical results. Results show that the performance of the proposed system is significantly improved compared to the conventional hybrid RF-FSO system.
-
Available online:May 17, 2022 DOI:
Abstract:The mechanism for asymmetric transmission is an important issue for enhanced sensing, amplification and asymmetric control of elastic waves. Parity-Time symmetric systems may provide a simple solution. The concept of Parity-Time symmetric systems comes from quantum mechanics, and one of its characteristics is unidirectional reflectionlessness. A PT symmetric beam for flexural waves is designed, which is based on piezoelectric shunting technology. Firstly, the PT symmetric condition is derived. Then, based on the effective medium method and finite element simulation, it is verified that the effective parameters of gain and loss unit meet the PT symmetric condition. The tunability of exception points is studied by changing the resonant frequency and the shunting resistance. Finally, the scattering property of the PT sym-metric beam is derived by transfer matrix method and finite element simulation, and the relationship between exceptional points and unidirectional non-reflection is illustrated. The calculated and simulated results show that the PT symmetric beam has several exceptional points including 511Hz and 520.5Hz. When the incident flexural waves of 511Hz is applied at the right side of the PT symmetric beam, the reflection coefficient is close to zero. However, when the frequency of the incident flexural waves changes to 520.5Hz, it should be applied on the left side of the PT symmetric beam in order to gain a total transmission without reflecting. The structure of the proposed PT symmetric beam is simple and the exceptional points of it are tunable, which can be used to achieve better asymmetric transmission of flexural wave.
-
Available online:May 17, 2022 DOI: 10.16339/j.cnki.hdxbzkb.2022297
Abstract:With the rapid development of Internet, virtual communities are emerging. While providing innovative resources, these communities also have problems such as low willingness of users to share and lack of good incentive mechanism. Blockchain can better solve these problems and promote community knowledge sharing. This paper constructs an online community knowledge sharing scheme based on Multi Chain, puts forward the resource access and storage mode of "metadata cloud storage" and designs the metadata information table in detail, designs the overall framework of the knowledge sharing scheme and the key processes of some businesses, puts forward the consensus mechanism of "Nominated Proof of Stake (NPOS) to design the blockchain network, Some functions of online community knowledge sharing are realized. Through analysis and experiment, the scheme of this paper has good scientific rationality, safety and execution efficiency, and has good reference value for the development of other related projects.
-
Available online:May 17, 2022 DOI: 10.16339/j.cnki.hdxbzkb.2022299
Abstract:Affected by suspended particles such as haze in the atmosphere,images taken outdoors often suffer from low contrast and low visibility. Existing dehazing methods fail to make full use of the local feature information of the image, and cannot fully extract the global details of the image. Therefore, there are problems such as incomplete dehazing and loss of image details. For this reason, this paper proposes a T-shaped image dehazing network based on wavelet transform and attention mechanism. Specifically, the proposed network obtains the edge detail features of the hazy image by performing multiple discrete wavelet decomposition and reconstruction on the image, and proposes a feature attention module that takes into account both the global feature and the local information extraction of the image, which strengthens the network"s learning in image visual perception and detail texture. Secondly, in the process of feature extraction, a T-shaped method is proposed to obtain multi-scale image features, which expands the network"s representation ability. Finally, perform color balance on the reconstructed clear image to obtain the final restored image. A large number of experimental results in synthetic data sets and real data sets show that the network proposed in this paper has superior performance compared with other existing network models.
-
Available online:May 17, 2022 DOI: 10.16339/j.cnki.hdxbzkb.2022300
Abstract:This paper proposes a state-sensitive event-triggered H∞ control strategy to solve the problem of unmanned ground vehicle (UGV) path tracking control under communication restriction. Firstly, the corresponding path tracking control model is established according to the dynamics of the connected vehicle. Secondly, a novel state-sensitive event-triggered communication (SS-ETC) strategy according to the state perception of path tracking in real time is proposed. Then, an event-triggered H∞ controller is designed by combining with time delay system modeling method and Lyapunov stability theory. The proposed dynamic event-triggered communication strategy based on state perception can dynamically adjust the communication threshold according to the state measurements of the control system, and effectively realize the adaptive co-design of UGV communication and control. Finally, the effectiveness of the proposed dynamic event-triggered control strategy is verified by simulation experiments.
-
Chen jian, Zhuang yao yu, Yang dan, Zhang jun jie
Available online:May 17, 2022 DOI: 10.16339/j.cnki.hdxbzkb.2022351
Abstract:Although MIMO technology can improve the utilization rate of spectrum, multi-dimensional signal processing brings great challenges to the detection of MIMO signals. Based on the analysis of various MIMO detection algorithms, QR decomposition is selected as the research object, which is a kind of nonlinear algorithm. In order to obtain higher performance of detection, the sorted QR decomposition is further studied and propose the sorting scheme based on L1-norm. Using Matlab for performance simulation, the L1-norm sorting strategy and the L2-nrom sorting strategy have basically the same impact on MIMO system, but the L1-norm sorting strategy reduces the computational complexity. On this basis, the hardware structure of improved sorted QR decomposition by Givens rotation on FPGA is proposed. Comparing with the solution of L2-norm, the L1-norm strategy reduces at least 29.2% combinational logic resources and 32.4% register resources when calculating a single column norm in the realization of 4×4 channel matrix decomposition. Comparing with similar designs, the frequency of operating clock has been significantly improved.
-
wangzhenyu, Guo Yang, Li Shaoqing, Zeng Jianping
Available online:May 17, 2022 DOI: 10.16339/j.cnki.hdxbzkb.2022352
Abstract:With the development and application of communication networks, the Internet of Things carries the safe transmission and storage of a large amount of sensitive information. Since devices are usually small in size and resource-constrained, complex security primitives are not suitable for authentication of lightweight IoT devices. This paper proposes a lightweight anonymous key shared authentication protocol for IoT devices, which generates a shared key by the physical unclonable function(PUF) and uses security primitives such as the MASK algorithm and the Hash function. The security analysis and verification are accomplished by Ban logic and ProVerif to prove that the protocol ensures security attributes such as anonymity, non-repudiation, and forward/backward confidentiality. Compared with other protocols, this protocol has the characteristics of low computing cost, small communication overhead and storage capacity, and high security performance, which is suitable for the secure communication transmission of resource-constrained devices.
-
LIU Guangyu, CAO Yu, ZENG Zhiyong, ZHAO Enming, XING Chuanxi
Available online:May 17, 2022 DOI: 10.16339/j.cnki.hdxbzkb.2022354
Abstract:Sonar image is seriously polluted by noise, which leads to the problem of low precision in underwater multi-target segmentation.Therefore, an underwater multi-object segmentation technique based on self-adjusting spectrum clustering combined with entropy weight method is proposed.The technology first by self-tuning spectral clustering of sonar image pixel clustering processing, make the image is divided into multiple independent area, and then according to the characteristics of complementarity and more sections of the redundancy of the statistical information entropy characteristics, brightness, contrast, long and narrow degree, entropy weight method is used to analyse the characteristics more empowerment and the optimal selection of a target area,Then the optimal target region is matched with all regions by multi-feature similarity. Finally, all target regions are segmented automatically by adaptive threshold iterative method according to the matching results of similarity. Experimental results show that there is not over-segmented of noise interference regions, and target regions segmented have higher accuracy, which verifies the effectiveness of the proposed method.
-
HUANG Yun1，2，GUI Lin1，QIN Tao3，WANG Wenxi1，2，ZOU Lai1，2，LI Heng1?
Abstract:A robotic belt grinding method for accurate control of the blade leading edge profile was proposed in this paper. The stress distribution in the contact area between the flexible abrasive tool and the leading edge of the blade was obtained by combining the semi-Hertzian contact theory and finite element simulation， and the material removal function was solved based on the Preston equation. The global material removal matrix was established by traversing the grinding depth of the control point. The resident time was set up to solve the nonlinear equations. Tikhonov regularization with a damping factor was used to eliminate the influence of a large sparse-ill-conditioned matrix on the fluctuation of solving accuracy， and then the desired dwell time was converted to the feed speed of the corresponding cutter point so as to generate the robot machining code. The grinding experiment results show that the robotic belt grinding method based on resident time control can achieve accurate machining of the leading edge profile of the blade within a given tolerance range， and the profile error can be controlled within 0.02 mm.
-
YANG Xin，KANG Renke，REN Jiawei，LI Tianrun，GAO Shang?
Abstract:To investigate the material removal mechanism and the subsurface damage evolution of monocrystalline gallium oxide， a systematic study was conducted by experimental methods. Firstly， the variable-depth nano-scratching test was used to simulate the material removal process of single grit and explore the material removal mechanism in the grinding process. Subsequently， the diamond grinding wheels with mesh sizes of SD600， SD1500， and SD5000 were used to carry out the grinding tests on the monocrystalline gallium oxide and to analyze the morphology of the ground surface and the evolution of subsurface damage. Scanning electron microscope and transmission electron microscope were used as the primary means of characterization， and the stress distribution during the scratching process was analyzed with the finite element method. The results indicate that the cross-acting slip band with multi-directions may lead to irregular fracture pits， and the orientation cracks were greatly affected by the （-3-10） plane of the monocrystalline gallium oxide. The grinding experiments reveal that the ground morphology， characterized by a brittle removal surface dominated by fracture pits and orientation cracks， gradually evolved into a completely plastic removal surface with the decrease of mesh sizes.
-
Research on Quality of Bottom Surface of Sapphire Micro-grooves Ground by Structured Grinding Wheels
ZHOU Fei1，2，XU Jinkai1，2?，ZHANG Wentong1，2，YU Huadong3
Abstract:Aiming at the problem of difficult machining of micro-structured surfaces of super-hard materials such as sapphire， a microstructure technology for grinding surfaces based on structured grinding wheels is proposed. In this paper， the surface of the grinding wheel is structured through Wire Electrical Discharge Machining（WEDM） technology， and the structurally dressed wheel was utilized to grind the microstructure of the sapphire surface. The influence law of structured wheel grinding speed， grinding depth， and feed rate on the surface roughness at the bottom of sapphire microgrooves in both down and up grinding modes was carried out. The results show that the microgroove morphology of the sapphire surface ground by the structured wheel is basically complete， the dimensional error is only 1.4 μm relative to the cutting depth of 120 μm， and the perpendicularity of the microgrooves is better， with a perpendicularity deviation of only 4.9°； The surface roughness at the bottom of the sapphire microgroove can be reduced by increasing the grinding speed and decreasing the grinding depth and feed rate in both down and up grinding modes； Compared with the up-grinding method， the micro-pits on the bottom surface of the micro-groove are smaller， and the bottom surface quality is better in the down-grinding method. The bottom surface roughness is reduced from 4.487 μm to 2.923 μm under the better machining parameters of grinding speed of 35 m/s， grinding depth of 1 μm， and workpiece feed speed of 200 mm/min.
-
SHEN Jianyun?，LIN Shaolong，CHENG Jiawei，WU Xian，ZHU Laifa
Abstract:The kinematics of a single abrasive particle in three-dimensional Ultrasonic Vibration Assisted Grinding （UAG） was analyzed. The ultrasonic vibration assisted grinding experiment of zirconia ceramics was carried out with the self-built three-dimensional UAG system. By comparing the normal grinding force， surface roughness， and surface morphology of zirconia ceramics under different ultrasonic-assisted conditions， the influence of different processing parameters on the three-dimensional UAG process and the influence of three-dimensional ultrasound on the grinding process were studied. The experimental results show that the normal grinding force of zirconia ceramics decreases with the increase of ultrasonic assisted machining dimension. Three-dimensional UAG machining can effectively reduce the grinding load， and the influence of machining parameters on the reduction of normal grinding force is the smallest. The reduction of normal grinding force decreases with the increase of feed speed and cutting depth and increases with the increase of spindle speed. The surface roughness of zirconia ceramic workpieces decreases with the increase of ultrasonic assisted processing dimension， and the surface morphology gradually shows more plastic scratches. The influence of processing parameters on the surface roughness of three-dimensional UAG grinding is also the smallest. It can be seen that the increase of the cutting trajectory length of the single abrasive particle in the three-dimensional UAG machining is beneficial to the decrease of the cutting thickness， thus reducing the grinding force and improving the surface quality.
-
YIN Youkang1，2，XU Jinyang1，2?，MING Weiwei1，2，AN Qinglong1，2，CHEN Ming1，
Abstract:Thermal damage defects are prone to occur during the grinding process of superalloys， which seriously reduces the fatigue life of parts. To address this engineering issue， this paper uses zirconium corundum grinding wheels and microcrystalline corundum grinding wheels to carry out creep-deep grinding experiments on superalloys. The effects of grinding process parameters on grinding temperature， grinding force， surface morphology， and surface roughness were studied. The formation mechanisms and effective suppression measures of thermal damage in superalloy grinding were revealed. The influence of grinding thermal damages on surface integrity was compared and analyzed. The results indicate that the instantaneous high temperature in the processing arc zone is the essential cause of the thermal damage of superalloy grinding. Microcrystalline corundum grinder can suppress grinding thermal damages productively due to its self-sharpening advantage. The surface of superalloy alloy grinding with thermal damages exhibits oxidation discoloration， fish scale-like coating texture， decreased hardness， and residual tensile stress. An effective means to realize the thermal damage-free grinding of superalloys is to reduce the generation of grinding heat and strengthen the heat transfer in the machining arc region.
-
WANG Liaoyuan1，SUN Yuli1?，ZHANG Guiguan2，WU Pengfei1，YI Siguang1， SUN Yebin1，ZUO Dunwen1
Abstract:In this study， an orthogonal experiment was designed by changing the preparation process parameters of bonded magnetic abrasives. Then， a series of magnetic abrasives with different specifications were prepared， and their morphology and composition were detected. Taking the 3D-printed AlSi10Mg plate as the processing object， the influence of the magnetic abrasive preparation process parameters on the polishing quality was revealed through the planar magnetic abrasive finishing experiment. A regression model between parameters and responses was established based on regression analysis， and the genetic algorithm optimized parameters. The results show that under the condition that SiC is 18~25 μm， the mass ratio of Fe to SiC is 4.7， the mass ratio of resin to curing agent is 2， the curing temperature is 100 °C， the material removal rate is 1.7 mg/min， and the surface roughness is reduced from the original 3.90 μm to 0.27 μm with a reduction of 93.1%.
-
BU Yingbin，WAN Zhenping?，CHENG Yu
Abstract:Considering the interaction between any adjacent abrasive grains during the grinding process， the orderly arrangement of a single abrasive grain is studied， and an orderly arrangement strategy that can control the spacing of any two abrasive grains is proposed. After arrangement， each abrasive grain acts as a separate cutting edge on the surface of the workpiece， and the material is cut off successively to form grooves. According to the arrangement strategy， three arrangement methods are designed. The spacing of any adjacent abrasive grains is -50 μm， 0 μm， and 50 μm， respectively， the arrangement template is prepared by electrochemical anode dissolution on the surface of the grinding wheel matrix， and the corresponding orderly arrangement of the grinding wheel is prepared by sanding electroplating， and thickening. At the same time， the grinding force and grinding temperature changes in grinding are calculated by grinding kinematic analysis， and the grinding force and grinding temperature in actual grinding are measured and analyzed by grinding experiment. The results show that under this test condition， the influence of feed speed on both is relatively independent： the grinding force is positively correlated with the feed speed， while the grinding temperature is negatively correlated with the feed speed. The grinding depth and the abrasive grain arrangement spacing comprehensively affect the changes in temperature and grinding force. When the abrasive spacing is small， the grinding temperature and force increase steadily with the increase of grinding depth； When the abrasive grain spacing is large， as the grinding depth increases， the two increase steadily and then slowly.
-
YANG Tao1，2，ZHAO Wei1，2?，ZHU Xijing1，2，CHEN Junwei1，3，PAN Haoyu1，2
Abstract:To explore the cutting mechanism of cortical bone material during abrasive water jet cutting and improve the quality of cutting surfaces in the abrasive jet cutting process， sodium chloride and garnet were used as abrasives to cut cortical bone. The changes in surface roughness under different cutting directions and the microscopic scratch characteristics were compared. The experimental findings demonstrate a characteristic pattern in which the roughness values of the cutting section initially decrease and then increase. Based on these roughness values， the section can be divided into three distinct regions： initial region， smooth region， and rough region. When using sodium chloride as the abrasive， the average roughness values of the cutting surface in the direction perpendicular to the bone unit are 1.74 times and 1.70 times those in the directions parallel and traverse to the bone unit， respectively. When using garnet as the abrasive， the average roughness values of the cutting surface in the direction perpendicular to the bone unit are 1.41 times and 1.55 times those in the directions parallel and traverse to the bone unit， respectively. Numerous micrometer-scale scratches are formed on the cutting surface during the cutting process. The impact of sodium chloride and garnet abrasives on the scratch characteristics of the cutting surface was compared. Compared with garnet， when using sodium chloride as the abrasive， the dimensions of the cortical bone cutting surface scratches are too large， with similar length and width values； the range of scratch depth values is greater.
-
CHAI Tongshan1，2，HUANG Chengqi1，2，LI Honggang3，CHENG Huaiyu2， WU Ziquan4，LONG Xinping1，2?
Abstract:This study proposes a novel degradable soft abrasive for abrasive water jet cleaning technology and analyzes and compares the cleaning performance and surface damage patterns of remanufactured components treated with the abrasive water jet of varying hardness. Furthermore， the study conducts comparative experiments on the cleaning of component dirt using three different jet methods： garnet hard abrasive water jet， walnut shell soft abrasive water jet， and pure water jet. The study analyzes the differences in cleaning rate， specific energy consumption， surface roughness after cleaning， and maximum pit depth among different cleaning methods， and investigates the matrix damage under different cleaning modes from both macro and micro perspectives. The results show that the walnut shell soft abrasive demonstrates superior cleaning efficacy， reduced specific energy consumption， improved cleaning speed， and negligible substrate surface damage. Consequently， the walnut shell soft abrasive is regarded as an ideal cleaning choice in remanufacturing industries or for applications that demand high surface roughness standards.
-
Wheel Wear of Tungsten Heavy Alloy Precision Grinding and Its Influence Mechanism on Surface Quality
LI Gan，KANG Renke，DONG Zhigang，WANG Hao，WANG Zhongwang，BAO Yan?
Abstract:To meet the demand for high-precision and high-integrity surface machining of tungsten alloy parts， this paper carries out systematic research to achieve the control of tungsten alloy grinding quality and the optimization of the machining process. The impact of grinding wheel grit type and bond type on the form of grinding wheel wear was analyzed， and the advantages of super-hard abrasive in tungsten alloy grinding processing were clarified. The influence law of abrasive grain size and grinding parameters on the quality of tungsten alloy grinding processing was investigated， which provided a basis for the development of a reasonable grinding process. Finally， the high-precision and high-integrity surface grinding process of tungsten alloy was obtained through the grinding test. The results show that the grinding wheel of tungsten alloy is easy to wear during the grinding process， and the super-hard abrasive grinding wheel is more suitable for the grinding processing of tungsten alloy. Metal-bonded diamond wheels showed superiority in the comprehensive consideration of surface quality and machining accuracy of tungsten alloy grinding processing. By improving the grinding parameters， a surface roughness of 18.9 nm after precision grinding of tungsten alloy was realized， and a mirror grinding effect was achieved.
-
ZHANG Xianglei1，CHEN Zhuojie1，LIAO Yuhui1，ZHOU Fenfen2，FENG Ming1?
Abstract:In this paper， a chemical magnetorheological polishing method based on the Halbach magnetic field array is utilized to enhance the precision and efficiency of polishing medical titanium alloy （TC4）. Strengthening the magnetic field strength is used for the Halbach magnetic field array， and hydrogen peroxide solution is incorporated as an oxidant in the polishing process. Firstly， the Halbach magnetic field array is compared with the conventional N-S magnetic field array through simulation. Subsequently， the activity of carbonyl iron powder is adjusted to verify the experimental feasibility. The effects of working gap， main shaft speed， and abrasive particle size on surface roughness and contact angle of workpiece surface are then investigated. The results demonstrate that the Halbach magnetic field array exhibits higher magnetic-field strength than the conventional N-S magnetic field array. Moreover， the surface roughness of the medical titanium alloy polished using this method is 80% lower than that achieved through single pure magnetorheological polishing. Optimal smoothing of the workpiece surface is achieved at a working gap of 0.8 mm， a main shaft speed of 400 rad/min， and an abrasive particle size of 1 μm， resulting in an optimal Ra value of 15.5 nm. The surface contact angle measurements indicate that the majority of contact angle values for the titanium alloy surface in the experimental group are less than 90°. In conclusion， the application of this method for polishing medical titanium alloy yields an ultra-smooth surface and enhances its hydrophilicity， thereby meeting the standards required for medical titanium alloys.
-
LIU Chao1，LIU Cheng2，WANG Hu3?，CHEN Liang2，LIANG Xiaoyan2，JIN Tan3
Abstract:A deep learning-based recognition and classification model named Tenon Grinding Burn Net （TenonGBNet） is proposed to address the issues of misdiagnosis and missed detection in visual inspection of grinding burns on nickel-based Superalloy blades. The K4125 nickel-based superalloy blades are chosen as the target， and through grinding burn tests and specimen organization inspection， a set of classification standards and corresponding image collection for different degrees of blade tenon grinding burns are obtained. Then， ODConv dynamic convolution is employed to fuse Inception V2 modules and the Coordinate Attention mechanism to enhance the model's feature extraction capability while ensuring the model is lightweight. Finally， a fully connected layer is employed for identification and classification. Experimental results indicate that， compared with four other classical classification models， TenonGBNet achieves an average classification accuracy of 96.50% while maintaining a minor model complexity and parameter count. Additionally， the classification accuracy for each burn level exceeds 95%.
-
GAO Guimin，LIU Yueming?，YANG Ce，ZHAO Chaoyue
Abstract:Based on the geometric relationship between the steel rail and the abrasive belt， a calculation model for the grinding depth and profile of the contact area is established to clarify the influence of grinding process parameters on the contact area parameters. As the grinding radius of the abrasive belt increases， the contact area of different steel rail profiles increases logarithmically， and the position of the axis length radius of the contact area changes on different cross-sections. Based on the characteristics of the rail abrasive belt grinding process， a calculation model for heat flux density in the contact area was solved and theoretically verified. Based on the contact area grinding depth and profile calculation， and regional heat flux density calculation model solved above， the instantaneous point heat source temperature field， continuous point heat source temperature field， and continuous action moving point heat source temperature field were applied to discretize the temperature field of the continuous action moving surface heat source in the contact area. Research shows that under the set grinding process parameters， the simulation and theoretical temperature changes on the surface of rail grinding are similar and almost reach the maximum temperature at the same time. The relative error between the simulation and theoretical maximum temperature is 6.14%， which verifies the correctness of the above theoretical model and simulation.
-
CHAI Zelin1，ZHOU Cunlong1?，GUO Rui1，JIANG Zhengyi2
Abstract:Because of the lack of an accurate mathematical model of oxide scale removal and process parameters in slurry blasting， the oxide scale of the Q235 hot rolled strip is taken as the research object in this article. According to the energy conservation principle， the kinetic energy change law of the mixed slurry of abrasive particles and water in the slurry blasting process during the impact was analyzed. The strain energy change law of the oxide scale on the surface of the matrix after the slurry blast was analyzed based on the strain energy theory， the mathematical model between the oxide scale removal amount and the slurry blasting process parameters was established， and the finite element ANSYS/ AUTODYN module and smooth particle hydrodynamics are used to simulate the process of oxide scale and matrix deformation during the slurry blasting process. Finally， the integrated descaling test platform is used to carry out the slurry descaling test. The results show that the oxide scale cracks and peels off when the oxide scale strain on the substrate surface is higher than the critical strain， the ratio of the influence of abrasive particle size on the increase rate of impact range to the impact velocity is 105.35%∶24.14%， the ratio of the influence of abrasive particle size on the increase rate of impact depth to the impact velocity is 233.67%∶5.86%， the maximum deviation rate between the finite element calculation and experimental results in the impact range is 8.71%， and the maximum deviation rate of impact depth is 8.55%. The finite element calculation results are consistent with the experimental results， and the model applicability is verified by the results of 304 stainless steel and 45 steel slurry descaling tests.
-
HU Da1，2，LU Jiabin1，2?，YAN Qiusheng1，2，LUO Yingrong1，2，LUO Ziyuan1，2
Abstract:Aiming at the environmental pollution of the polishing solution in chemical mechanical polishing， a single-crystal SiC chemical mechanical polishing method based on metal electrochemical corrosion is proposed. The Si surface of single-crystal SiC corrosion performance and wear performance of electrochemically corroded were investigated by corrosion experiments and wear experiments. By comparing the corrosion performance of Al， Cu， and Fe metals on the Si face in a Na2SO4 electrolyte solution， it was found that only Al can generate a noticeable corrosion layer. The EDS and XPS analyses of the Si face confirmed that the corrosion is due to the formation of the SiO2 layer. Frictional wear experiments were conducted to investigate the influence of solution composition on the wear behavior of Si face. Increasing the concentration of the Na2SO4 electrolyte solution resulted in higher wear， with a maximum wear value of 7.19 μm2 obtained in 1.00 mol/L Na2SO4 electrolyte solution. In an acidic corrosive solution， the Si face exhibited the highest material removal， with a wear value of 11.97 μm2 achieved at pH=3. The material removal mechanism of single-crystal SiC via metal electrochemical corrosion involved the corrosive reaction involving Al at the cathode， which generated a corrosion current， and the subsequent oxidation of the SiC surface at the anode， thereby forming a SiO2 oxide layer leading to material removal.
-
ZHANG Wei1?，GAO Yuan1，MA Qingyuan1，PENG Yingbo1，3，WU Xiwang2，LAN Yang1， CHEN Yuxuan1，CHEN Zhiqiang2
Abstract:In the laser additive manufacturing process of superhard tools， diamonds are highly susceptible to the direct irradiation of laser beams and the influence of high-temperature melt pools， leading to phenomena such as graphitization and other thermal damage. A typical metal bonding agent CuSn10 powder for diamond abrasives is selected， and the Powder Bed Fusion-laser Beam （PBF-LB） technology is used to prepare CuSn10-diamond composites in this study. Focusing on two key factors affecting the performance of diamond particles in the manufacturing process， high-energy laser beams and high-temperature melt pools， individual diamond particles are selected as the research subject. A finite element simulation analysis is conducted to construct a temperature field model of diamond particles， reflecting the thermal evolution process of diamond particles in PBF-LB. The study elucidates the thermal damage mechanism of diamonds during the PBF-LB process， revealing that the graphitization transformation of diamonds is not caused by direct laser irradiation but is induced by the thermal effects of high-temperature melt pools. The critical temperature for graphitization of CuSn10-diamond composite material in the PBF-LB process is 1 491.6 °C. Furthermore， a quantitative relationship is established among the PBF-LB process-diamond particle temperature-degree of graphitization-frictional wear performance， demonstrating that with the increase of diamond particle temperature， the degree of graphitization increases， seriously damaging the friction and wear performance of the composite material.
-
LUO Qiufa1，3?，CHEN Jieming1，CHENG Zhihao1，LU Jing1，2
Abstract:The material characteristics of silicon carbide substrate， which are difficult to machine， coupled with its amplification effect of large-sized and ultra-thinned， pose a huge challenge to existing processing technologies. Consequently， the processing technology of high efficiency and high quality for silicon carbide substrate has become a current research focus. In this paper， the research progress of mechanical and chemical grinding and polishing technology for silicon carbide substrates is reviewed. The characteristics of various grinding and polishing technologies are compared. The challenge and development trend of grinding and polishing technologies of silicon carbide substrate is pointed out to provide new ideas and methods for high quality， high efficiency， and low-cost processing of large-size silicon carbide substrate.
-
REN Yinghui?，WAN Jiawei，KUANG Zengyu，XIE Hui
Abstract:The structural deformation generated by multi-source heterogeneous decommissioned 3C products in the service stage may cause the failure of automatic disassembly equipment. The performance drift failure will also disturb the disassembly process planning and production scheduling. Taking the decommissioned 3C product mixed-flow disassembly line as the research object， this study investigates the insertion order scheduling problem caused by decommissioned product disassembly failure in decommissioned products. An AND/OR node network model is constructed to quantify uncertain disassembly sequence and depth. With the optimization goal of maximizing workstation utilization and the variable of disassembly fault product buffering and transfer threshold， a mixed manual-automatic line reordering schedule model is established. Then， it is encoded by two-dimensional real-number coding and solved by a genetic algorithm. Finally， data instances of 58 varieties of decommissioned smartphones with mixed manual-automatic disassembly lines are selected for verification. The results show that the established manual-automatic hybrid line scheduling model can effectively develop the threshold scheduling scheme of maximum workstation utilization. The optimized maximum utilization rates of the three types of mixed-flow disassembly lines in the example clustering are 80.3%， 73.2%， and 81.3%， respectively.
-
KUANG Zengyu，XIE Hui?，REN Yinghui，SHI Minhao
Abstract:Aiming at the uncertainty of disassembly processes and logistics， an optimization method for the production and logistics integrated scheduling in a disassembly workshop is proposed to cooperatively optimize efficiency and cost. Firstly， the interaction factors between reverse production and reverse logistics in end-of-life product disassembly workshops are analyzed. A multi-objective scheduling model of the workshop is constructed， aiming at optimizing the maximum completion time and the advanced/delayed costs in reverse production and workshops logistics processes. Secondly， based on the logistics route decision， a mutation operator with gene repair is designed to improve the mutation accuracy of the NSGA-Ⅱ algorithm and enhances the solution effectiveness of the algorithm. Finally， taking a company's mobile phone disassembly line as an example， the multi-size production and logistics examples are analyzed. The results show that as the number of adaptive guided vehicles increases， the delay cost of large and small size examples are reduced by 57.1% and 58.3%， respectively， verifying the effectiveness of the model.
Vol, , No.4, 2024
Special Issue
Virtual Special Issue中国科学引文数据库来源期刊(CSCD)
第二届国家期刊奖百种重点期刊
教育部中国高校百佳科技期刊
湖南省十佳科技期刊
