China Mechanical Engineering

Experimental Study of Single Grain Grinding for SiCf/SiC Ceramic Matrix Composites

YIN Jingfei, XU Jiuhua, DING Wenfeng, SU Honghua, CAO Yang, HE Jingyuan

2022, 33(15): 1765-1771. DOI: 10.3969/j.issn.1004-132X.2022.15.001

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The single grain grinding tests of silicon carbide fiber-reinforced silicon carbide（SiCf/SiC） ceramic matrix composites were conducted to investigate the side chipping characteristics under the brittle removal mode. The results show that when grinding SiC matrix， the cracks in the matrix easily lead to the side chipping of large blocks. When grinding fibers， the widths of side chipping increase with the increasing of the angles between fiber and grinding direction. When grinding the 90° fiber， increasing grinding speed may decrease side chipping degree. The side chipping widths caused by grinding at 50 m/s and 90 m/s are as 30% and 60% smaller than that by grinding at 20 m/s， respectively. In the ranges of testing parameters， increasing the grinding parameters may not increase the side chipping degree， but may improve the material removal rate.

Numerical Simulation and Experiments of SLAEs for Planar Polishing with Dielectrophoresis Effect

DENG Qianfa, CHENG Jun, LYU Binghai, , YUAN Julong, WANG Xu, CEN Kaidi,

2022, 33(15): 1772-1779，1793. DOI: 10.3969/j.issn.1004-132X.2022.15.002

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In the processes of chemical mechanical plane polishing（CMPP）， the polishing liquid was affected by centrifugal forces of polishing disk， and the effective utilization rate was low， and the surfaces of polishing disks were unevenly distributed， thus the efficiency and quality of plane polishing were affected. A same layer arrangement of eletrodes-dielectrophoresis planar polishing（SLAE-DEPP）method was proposed herein. COMSOL Multiphysics was used to simulate the potential changes, and the electric field square gradient change of the closed ring electrode and the non-closed ring electrode under SLAEs. The simulation results show that there are changes in both of the radius ρ directions and the angle θ directions. And the maximum electric field square gradient change at the opening is about 1.5 times than that of the closed electrode methods. The non-closed ring SLAEs was used to make the polishing disc， and the experimental platform was built to carry out the polishing experiments. The experimental results show that compared with traditional CMPP polishing， the SLAE-DEPP method polishes a silicon wafer with a diameter of 76.2 mm. After polishing for 6 h， the values of surface roughness Ra at workpiece center decrease from the initial 690 nm to less than 1 nm， the workpiece flatness（RMS value）is as 0.268 μm， the workpiece material removal rate (MRR) increases by nearly 27.3%， the workpiece surface is removed uniformly to mirror surface， polishing efficiency and polishing quality are both better than that of traditional CMPP method.

Experimental Research of Coarse-grained Arc Diamond Grinding Wheel Dressed by Laser and Electrical Discharge Compound Dressing

CHEN Genyu, DAI Longzhou, LI Mingquan, YUAN Shangyong

2022, 33(15): 1780-1786. DOI: 10.3969/j.issn.1004-132X.2022.15.003

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Affected by the characteristics of laser Gaussian beam， the differences of the spot size and laser energy irradiated on the surface of grinding wheels follound the dressing path， which was difficult to realize high-precision dressing of arc diamond grinding wheels. A compound dressing method was proposed using laser rough dressing and electrical discharge finished dressing. First， the laser dressing method was used to efficiently remove the excess abrasive layers to obtain an arc profile. Then, a high-precision arc electrode was used to match the profile for electrical discharge dressing. In this way， a higher precision arc grinding wheel might be dressed. An arc profile with a radius of 13 mm was tested on a diamond grinding wheel with a grain size of 120. The radius of the final dressed arc profile is as 13.006 mm， and the PV value of the profile errors is as 10.90 μm. Finally， the grinding wheel dressing effectiveness was verified by grinding alumina ceramics. The fitting radius of the arc profile of workpiece is as 13.012 mm， and the profile error PV value is as 11.33 μm.

Preparation of Porous Brazed Grinding Wheels and Experimental Research of SiC Ceramic Grinding

LIU Wei, MAO Guoan, YAN Can, LI Boxin,

2022, 33(15): 1787-1793. DOI: 10.3969/j.issn.1004-132X.2022.15.004

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Based on the molding and vacuum solid-phase sintering processes，a porous brazed diamond grinding wheel（PBDGW）with high bonding strength and uniform pore distribution was prepared by using Cu-10Sn binder，oxidation pretreated TiH2 brazed pore-forming agent and MBD8 diamond abrasive particles. The SiC ceramic grinding experiments of PBDGW and multilayer brazed diamond grinding wheel（MBDGW） were carried out for comparison，then the grinding performances of grinding wheel were analyzed from grinding force，workpiece surface roughness and surface/sub-surface morphology. The experimental results show that the tangential force in SiC ceramics grinding with PBDGW decreases by 8.4%～23.6%，the normal force decreases by 10.2%～38.6%，and the average reduction of surface roughness is as 10.4%. The workpiece surface has better integrity，and the surface/sub-surface brittle fracture，microscopic crack and other defects are less.

ECCG of Aluminum AA6061 and Titanium TC4 at Pseudo-steady States

GAO Binhua, HE Xun, WANG Qirong, JIN Tan, SHANG Zhentao

2022, 33(15): 1794-1802，1809. DOI: 10.3969/j.issn.1004-132X.2022.15.005

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ECCG process was an effective method to solve wheel loading issue in grinding of ductile metal parts. Keeping the balance between loading material formation on wheel surfaces and the electrolysis was the key to successful application of this process. According to electrochemical theory and grinding mechanism， a new method was proposed to quantitatively evaluate wheel loading degree with electrolysis current， and the working voltages for different grinding parameters were determined during ECCG processes. Both of aluminum AA6061 and titanium TC4 were ground by this machining process at the pseudo-steady states. The results show that the ECCG process holds strong expandability and may be used for manufacturing large ductile metal parts.

Fabrication and Measurement of SiC Fiber-optic Fabry-Perot Pressure Sensors for High-temperature Applications

SHENG Tianyu, LI Jian, LI Hongchang, JIANG Yonggang

2022, 33(15): 1803-1809. DOI: 10.3969/j.issn.1004-132X.2022.15.006

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In order to meet the urgent needs of in-situ pressure detections at high temperatures, a fiber Fabry-Perot SiC high-temperature pressure sensor was fabricated based on the excellent high temperature resistance of SiC materials. A SiC sensor diaphragm with surface roughness Ra about 11.9 nm was fabricated via an ultrasonic vibration mill-grinding(UVMG) method. A direct bonding using SiC wafer hydrofluoric acid was used to realize the high strength air tightness bonding between SiC sensing diaphragm and SiC substrate. The prepared SiC high temperature resistant pressure sensor prototype was tested in high temperature conditions after a high temperature pressure test system was built. Results demonstrate the sensing capabilities for pressures from 0 to 4 MPa at 600 ℃. The pressure sensor illustrates a good linearity(R2>0.99). The pressure sensitivity is measured to be as 104.42 nm/MPa at 600 ℃.

Core-problem Oriented System Cause Identification Method and Innovative Design Research

YANG Guang, LI Wenqiang, WAN Changfu,

2022, 33(15): 1810-1820. DOI: 10.3969/j.issn.1004-132X.2022.15.007

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Aiming at the facts that traditional innovative design methods might only solve one pair of conflicts when solving multi-conflict problems, a core problem-oriented system cause identification method was proposed, which might solve multi-conflict problems. The conflict relationship in product design was obtained through the house of quality and the core problems were selected. The root cause analysis method was used to obtain the system causes of each core problems, and the relationship network diagram between the core problems and the system causes was established. The best worst method was used to obtain the importance degree of each system causes and carry out innovative design in order of importance. The solution of the system causes may realize the solution of multi-conflict problems. Moreover, the design of floating plate vibration isolator is taken as an example to verify the feasibility and effectiveness of this method.

Multiaxial Equivalent Strain Fatigue Life Prediction Model Based on Critical Plane Theory

LIU Jianhui, ZHAO He, RAN Yong, LI Bin

2022, 33(15): 1821-1827. DOI: 10.3969/j.issn.1004-132X.2022.15.008

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In view of the defects that the effects of non proportional additional strengthening were not considered in the equivalent strain model, the plane where the maximum shear strain was located was defined as the critical plane and introduced the maximum normal stress, normal strain range and phase difference in the shear plane as damage parameters to reflect the additional strengthening effects under non proportional loading. The influences of the maximum normal stress and normal strain range of the critical plane on the crack initiation and propagation were also considered. Thin-walled tube specimens made of five kinds of materials, 16MnR, GH4169, S460N, 45 steel and pure Ti, were used to verify the correctness and effectiveness of the proposed model. Meanwhile, compared with three classical models, the results show that the prediction ability of the proposed model is better than that of the other three models and the life prediction results are more accurate.

Analysis on Dynamic Characteristics of Compliant Foil Face Gas Seals with Three Degrees of Freedom Perturbation

2022, 33(15): 1828-1840. DOI: 10.3969/j.issn.1004-132X.2022.15.009

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A new type of compliant foil face gas seal was proposed. Based on the theory of gas lubrication and elasticity mechanics， small perturbation method was applied to establish the perturbation film pressure governing equations of compliant foil face gas seals. The variation laws of dynamic characteristic coefficients were compared and analyzed under different foil deformation mechanical models， and the influence laws of different operating and structural parameters on the dynamic characteristics of the gas films were investigated. Taking the maximum dynamic main stiffness and damping as comprehensive optimization objectives， the optimal range of structural parameters was determined. Results show that with the increasing of excitation frequency and rotational speed， the dynamic complementary changes of dynamic main stiffness and dynamic main damping of the gas film suppress the radical change of film thickness， while the change of dynamic cross coefficients of gas film instability causes slows down， which reduces the risk of gas film oscillation and instability caused by the sudden changes of operating conditions. In addition， the increase of medium pressure may significantly improve the seal stability and vibration resistance performance. When the wedge height is in 5～8 μm， the slope ratio is in 0.2～0.4， the foil-dam ratio is in 0.5～1.1， the number of foil is in 4～6， and the structural damping is in 5×107～8×107 Pa·s/m， the comprehensive dynamic immunity performance of compliant foil face gas seal is optimal.

A Multi Class Domain Adaptive Transfer Identification Method for Tool Wear States under Different Processing Conditions

SHI Keming, ZOU Yisheng, LIU Yongzhi, DING Kun, DING Guofu

2022, 33(15): 1841-1849. DOI: 10.3969/j.issn.1004-132X.2022.15.010

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Under the new processing conditions， aiming at the problems of low identification accuracy rate of tool wear identification model trained under historical processing conditions， a tool wear state identification model across processing conditions was proposed based on transfer learning. Firstly， convolutional neural network was constructed to extract the transfer features of tool samples， and the difference of tool sample distributions was measured by the maximum mean difference under different processing conditions. Secondly， the sample distance of source domain features was improved by IDC. The strategy of maximizing the norm was adopted for the probability matrix of target data to extract the fault features of target domain samples with high discrimination. Finally， the milling cutter machining tests were taken as an example to verify the validity of the model. The average identification accuracy rate of the model is as 96.8%， which is as 4.9% higher than that of the method without IDC and maximum kernel norm.

Avoidance Planning for Intelligent Vehicles in Dilemma Based on Nominal Cost

ZHANG Rongshen, WANG Yutian, HU Rongquan, YANG Lingfang, HUANG Zhi

2022, 33(15): 1849-1856. DOI: 10.3969/j.issn.1004-132X.2022.15.011

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A nominal cost of conflict injury was developed based on risk avoidance algorithm. Counting the casualty， legislation， ethics and the uncertainty of conflict， the nominal cost model for the involved traffic participants was devised based on ethical survey. Taking the nominal cost expectations as the object and limits of vehicle system as the constraints， the problem of trajectory planning of intelligent vehicles in dilemmas was established. This optimization problem was solved by a hierarchical frame consisting of warm start and numerical optimization. The typical dilemmas were designed， Simulation results verify that the proposed method presents risk avoidance trajectories that are in line with public expectations.

Applications of Microfluidic Technology in Cross-domain of Mechanical Engineering and Life Science

MAN Jia, HUA Zesheng, XIA He, LI Jianyong, LI Fangyi, LI Jianfeng,

2022, 33(15): 1857-1868. DOI: 10.3969/j.issn.1004-132X.2022.15.012

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Taking microfluidic technology as the research object， the preparation materials and technology of microfluidic chips were introduced， and the applications of microfluidic chip technology in the cross fields of life science were emphasized. It was mainly introduced from three aspects：biological detection， bionic fabrication of in vitro structure and preparation of controllable drug carriers， and the key technologies involved were discussed from the aspects of chip structure design and preparation， functional module integration， process regulation and so on. The application prospect of microfluidic technology in the fields of cross-domain between mechanical engineering and life science was prospected.

Conceptual Design of Bio-inspired Jumping Mechanisms for Flapping-wing Aerial Vehicles

MA Dongfu, SONG Bifeng, XUE Dong, XUAN Jianlin

2022, 33(15): 1869-1875，1889. DOI: 10.3969/j.issn.1004-132X.2022.15.013

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Aiming at the problems of lack of autonomous take-off and landing functions of flapping-wing aerial vehicles， which seriously affected the applicable scenarios， the design of bio-inspired jumping mechanisms was carried out. Firstly， the typical movement state of birds in the processes of jumping taking-off was analyzed. And according to the laws of movement changes of the hind limb skeleton structure， center of gravity， force and velocity in this process， the dynamic movement process of jumping take-off of the flapping-wing aerial vehicles was designed. Then， based on the skeleton anatomical structure of birds leg， a closed-chain five-bar geared bird-leg like jumping mechanism was designed. The kinematics equation of the mechanism was derived based on D-H method， and the dynamic equation of the mechanism in the take-off stage was established using Lagrange equation. Finally， the detailed structure design of the jumping mechanism was carried out， and then the simplified jumping model was simulated and analyzed by ADAMS. The simulation results show that， with the help of the designed bionic jumping mechanism， the velocity of mass center of the flapping-wing aerial vehicle system reaches 8.4 m/s， which is higher than the speed 7.9 m/s required by the “dove” aerial vehicle， so the mechanism has the possibility of jumping take-off.

Research on Influence Model and Influence Factors of Welding Quality of Continuous Annealing Units

ZHANG Wenjun, ZHANG Yandong, LIN Wei, ZHAI Qianjun, BAI Zhenhua,

2022, 33(15): 1876-1881. DOI: 10.3969/j.issn.1004-132X.2022.15.014

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During the welding processes of strip steel welding machine of continuous annealing units， there were problems that welding parameters might not be optimized and technicians might not quantitatively analyzed the welding quality. Based on the analyses of comprehensive influence model of the welding quality， taking full account of equipment and technology characteristics of welding machine of continuous annealing units， the typical specifications of strip steel were selected， and the factors that affected welding quality such as the pressure of roller， the pressure of welding machine， the welding current， the overlap amount， and the welding speed were quantitatively analyzed. Adjusting the above factors， the comprehensive objective function value of welding quality was controlled within a certain range， and then the floating range of welding parameters was obtained. Based on the field verification and analysis of optimal welding technology parameters， the quality requirements of the strip steel welding of the factory were satisfied. At the same time， the comprehensive impact model of welding quality of the continuous annealing units was applied to the practical production of a domestic continuous annealing unit welding machine， and the corresponding software was developed， which improves the strip production efficiency and finished product prediction accuracy of welding quality of strip steels.

Drag Torque Algorithm of Wet DCT and Its ApplicationsLIU Bo

ZHANG Xingui, SHI Xinglei, YU Zilin, ZHONG Zhenyuan, LI Jia

2022, 33(15): 1882-1889. DOI: 10.3969/j.issn.1004-132X.2022.15.015

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One type of wet DCT was taken as research subject, and the mechanism of output torque variations of the DCT for cars was analyzed in neutral/park positions while creeping or idling respectively. By building the mathematical model of the output torque， theoretical calculation formulas of the equivalent radius of lubricating oil film between DCT plates， the max drag torque and the critical rotational speed were figured out， and the dynamic interactions of three elements were illuminated. The accuracy was proved by experimental data， which may be used to reduce output torque fluctuation， drag torques and critical rotational speeds.

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