China Mechanical Engineering

Research Progresses on Surface Roughness Model of Brittle Material Machining

MA Lianjie, LI Hongshuang

2022, 33(07): 757-768. DOI: 10.3969/j.issn.1004-132X.2022.07.001

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Many factors affected surface roughness. Unique properties of brittle materials made the surface formation mechanism of brittle materials more complex, which made the machining quality difficult to control. By constructing the model of surface roughness, the surface roughness was predicted, and the machining quality might be controlled. In order to better reference the previous research results, characterization parameters of surface roughness were summarized herein. The methods used to establish the surface roughness model were constructed. The main research schools of the model and their development history, main academic contributions, and characteristics of the model were analyzed and summarized in detail. Finally, the future research direction of surface roughness model construction was prospected.

Decoupling and Reconstruction of Unsteady Flow Field of Inter-blade Vortices Based on DMD

TONG Zheming, XIN Jiage, TONG Shuiguang,

2022, 33(07): 769-776. DOI: 10.3969/j.issn.1004-132X.2022.07.002

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In order to explore the spatiotemporal evolution of inter-blade vortices in a francis turbine at unsteady load conditions, the DMD method was introduced in combination with numerical simulation and experimental verification to decouple the coherent structure of inter-blade vortices. The numerical results show that inter-blade vortices have low frequency characteristics and with the main frequency which is 0.5 times the rotation frequency of the turbine. The cavity of inter-blade vortices originates from the upper crown of the impeller in the shape of vortex tube, which is connected with the sheet vortices on the back of the blades. DMD method was applied to obtain dynamic modal of inter-blade vortices velocity field, and was compared with the POD method. The results show that the inter-blade vortices flow structure is decomposed by the DMD method at a specific frequency to obtain the single-fold frequency characteristics, which is more convenient for the flow mechanism analysis of the coherent structures. Both of two methods may reconstruct the inter-blade vortices velocity field based on the average flow mode and the main modes, but there are errors in the reconstruction of local complex inter-blade vortices regions.

Transient Start-up Dynamics Model and Sealing Performance of Single Metal Seals in Cone Bits

MA Yi, CHEN Yutao, MENG Xiangkai, ZHAO Wenjing, PENG Xudong,

2022, 33(07): 777-785. DOI: 10.3969/j.issn.1004-132X.2022.07.003

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The reliability and service lifes of the single metal seals were directly affected by the frequent start-up and vibrations of the cone bits during operations. The transient start-up dynamics model of single metal seals under complex working conditions was established based on the thermal-fluid-solid-dynamic coupling field. The lubrication equation and dynamics equation were solved by finite difference method and Newmark method. The effects of the bit speed and axial excitation on the dynamic sealing performance of single metal seals were investigated. The results show that as the bit starts up to constant speed， the liquid film on the end faces of single metal seals always presents a divergent distribution in the radial direction under high pressure condition（p0=30 MPa）. The interface temperature rise increases oscillatingly and reach a stable fluctuation under the axial excitation. The instantaneous leakage rate fluctuates alternately between positive and negative， and the amplitude is much larger than that of the steady leakage rate. Especially when the leakage rate is negative， the mud on the outer diameter side of sealing rings may easily invade the sealing gap. With the increase of bit speed and axial excitation load， the dynamic performance of single metal seals is further deteriorated.

Design of Diameter-variable Wheels Based on Continuity and Steady Distribution of Slip Line

YIN Yonghui, CHEN Sichen

2022, 33(07): 786-796. DOI: 10.3969/j.issn.1004-132X.2022.07.004

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Based on theories of wheel terrain contact dynamics, a new type of diameter-variable wheel, which was fit for sandy soil, with close fitting inner and outer double layers’ rigid rim and a central grouser was designed. The interaction mechanism between different sections of diameter-variable wheel and soil, and the soil flow slip model were analyzed. Through the detailed derivation and numerical calculation of the soil slip-line formulas, slip-line radius and equivalent wheel rim of the diameter-variable wheel were proposed. And then, the design ideas that the height of shear-slip section as main factor and inclination angel as auxiliary factor was put forward. The functional relationship among the height of shear-slip cross-section(the adjustable grouser) and inclination angle, and diameter ratio in smooth continuous slip-line model was established.

Electrochemical Trepanning for Long Thin-walled Blades

ZHANG Xiaobo, ZHU Dong

2022, 33(07): 797-803，810. DOI: 10.3969/j.issn.1004-132X.2022.07.005

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In order to realize the machining of long thin-walled blades, the flow form of electrolyte flowing into the blade profile uniformly was designed, and the simulations and comparisons of diversion outflow and the open outflow were performed. The results show that the uniformity and stability of the flow field may be optimized by adding diversion channels. Experiments on the electrochemical trepanning of thin-walled blades were performed, and the machining of thin-walled blades at 1.4 mm/min was realized. The surface roughness values of hubs are decreased from 0.532 μm to 0.307 μm, and the surface roughness values of blades are decreased from 0.816 μm to 0.583 μm.

Design of Oblique Incident Line-focusing SV Wave Electromagnetic Acoustic Transducer for Thick-walled Aluminum Tubes

CAI Zhuoyue, TU Jun, ZHANG Xu, DENG Zhiyang, WU Qiao, SONG Xiaochun,

2022, 33(07): 804-810. DOI: 10.3969/j.issn.1004-132X.2022.07.006

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In order to apply oblique incident line-focusing SV wave for defecting detection of thick-walled aluminum tubes, an optimization design method of curved meander-line coil was proposed, which was used to stimulate SV wave. Three simulation models with plane coil, plane bending coil, and optimized curved coil as main components were studied by taking workpiece with different curvatures as detection objects. The results show that the optimized curved coil has the most obvious improvement effectiveness on the workpieces with large curvature, the directivity accuracy may be increased by 14.53%, and the detection amplitude may be increased by 37.42%. Finally, the experiments were carried out with 4 mm diameter transverse through hole of the thick-walled aluminum tubes as artificial defect. It is found that the detection amplitude of the maximum curvature tube is enhanced by 338.84%.

Research on Geometric Error Analysis and Parameter Identification of Modular Robots

GAO Wenbin, HUANG Qi, YU Xiaoliu,

2022, 33(07): 811-817，851. DOI: 10.3969/j.issn.1004-132X.2022.07.007

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To solve the rapid compensation problem of the errors of modular robots after reconfiguration， the geometric error sources of modular robots were analyzed and divided into module parameter errors and assembly parameter errors between modules. The joint module， link module and assembly parameters between consecutive modules were described based on product of exponentials（POE）formula and homogeneous transformation. Then， the actual kinematic model of joint-link subassembly was established. Based on high-precision balls and external measurement，an identification method for module parameters and assembly parameters between modules was proposed to identify the kinematic parameters of the subassembly. A test of parameters identification and verification for two kinds of joint-link subassemblies with typical configuration was carried out. The results show that the average positioning errors of two subassemblies after compensation are about 1/30 than that before compensation.

Research on Numerical Calculation of Normal Contact Stiffness of Steel-BFPC Joint Surfaces

XU Ping, XU Shuting, SHEN Jiaxing, YU Yinghua

2022, 33(07): 818-824. DOI: 10.3969/j.issn.1004-132X.2022.07.008

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In order to solve the problems that the maximum contact area in fractal contact theory was difficult to calculate accurately, which would lead to the difficulty in obtaining actual contact area of joint surfaces effectively, a calculation method for actual contact area of joint surfaces was established based on discrete numerical calculation method, and a new calculation method for contact stiffness of steel-BFPC joint surfaces was established by combining the method with the theoretical contact stiffness model of joint surfaces. The contact stiffnesses of steel-BFPC joint surfaces components under five kinds of preloads were measured through modal experiments. Experimental results were compared with the theoretical calculation ones, and the relative errors between them are less than 6.0%.

An Assembly Quality Prediction Method for Automotive Instrument Clusters Using CNN-SVR

HE Yan, XIAO Zhen, LI Yufeng, WU Pengcheng, LIU Degao, DU Jiang

2022, 33(07): 825-833. DOI: 10.3969/j.issn.1004-132X.2022.07.009

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Due to the long quality inspection time during assembly and lower production efficiency of automotive instrument clusters, an assembly quality prediction method for automotive instrument clusters using CNN-SVR was proposed. Combined with the assembly processes of instrument products, the production data features were extracted through CNN, which were used as the inputs of SVR to predict the pointer deflection angle that characterizesd the quality of instruments. The original production data of the instruments were obtained through the quality inspection systems of the assembly workshops, and the pointer deflection angles under different quality inspection conditions were predicted. The results indicate that proposed method has smaller prediction errors and strong generalization ability, which may accurately and effectively predict the assembly quality of automobile instrument clusters.

Surface Roughness Modeling for Lapping Hard and Brittle Materials by Flexible Abrasive Tools

ZHANG Yuqiang, , HU Zhongwei, ZHU Zepeng, CUI Changcai, CHEN Mingxin, XIE Binhui, LI Ruiping

2022, 33(07): 834-841. DOI: 10.3969/j.issn.1004-132X.2022.07.010

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By analyzing the interaction processes between abrasive particles and the surface of the workpiece, a theoretical prediction model for surface roughness of the hard and brittle materials by flexible abrasive tool was established herein. The rubber bond diamond lapping disc was selected as the flexible abrasive tool, and the sapphire substrate was selected as the workpiece. The lapping experiments were carried out under different elastic modulus, abrasive particle concentration, abrasive particle size, and different lapping pressures. And then, the experimental values of the surface roughness were compared with the theoretical predicted values under different lapping conditions, which shows that the experimental values are consistent with the predicted results of the theoretical model. The prediction errors are as 6.32%~11.76%, which proves that the established theoretical prediction model of surface roughness is reliable for lapping hard and brittle materials by flexible abrasive tools.

Energy Consumption Distribution Characteristics and Prediction Model of High-speed Dry Gear Hobbing Machine

NI Hengxin, YAN Chunping, SUN Han, XU Teng, HUANG Yigong, ZHOU Chao

2022, 33(07): 842-851. DOI: 10.3969/j.issn.1004-132X.2022.07.011

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Aiming at the energy consumption optimization of high-speed dry gear hobbing machines, energy consumption distribution characteristics and prediction model of machine tool under variable processing parameters were explored herein. Firstly, taking energy consumption components of the machine tool as the research object, a power model of high-speed dry gear hobbing machine was established. Then, based on the circuit distribution principle of machine tools, the model was analyzed and verified through gear hobbing experiments, and the relationship between variable processing parameters and power and energy consumption of different parts of the machine tool was revealed. Finally, the energy consumption prediction model of high-speed dry gear hobbing machine was constructed.

Energy Management Strategy Optimization Method Based on SOC Penalty Function

ZENG Fanqi, YUAN Xiaojing, WANG Xuping, ZHANG Ze, LIU Xiaofang

2022, 33(07): 852-857，871. DOI: 10.3969/j.issn.1004-132X.2022.07.012

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In order to improve the fuel economy of military ISG hybrid power vehicles and ensure SOC of battery to be effectively maintained, a penalty function was introduced into the traditional EEMS. The EEMS based on SOC penalty function was proposed. Firstly, the energy management strategy built on logic rules was optimized. Then the optimization method was verified under the simulated off-road cycles. Finally, generation indexes of the vehicle were evaluated. After optimization, torque distribution among power sources is coordinated better, and the engine runs more smoothly. Meanwhile, the economy is improved, and the stabilizing effects of the voltages and currents are better.

Constituent and Property Adjustment of Deposited Metals by Dissimilar Auxiliary Wire Feed Gas Metal Arc-based Additive Manufacturing

HAN Qinglin, GAO Jia, LI Xinlei, ZHANG Guangjun

2022, 33(07): 858-863. DOI: 10.3969/j.issn.1004-132X.2022.07.013

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To achieve efficient and stable additive manufacturing of dissimilar material parts， the dissimilar auxiliary wire feed gas metal arc-based additive manufacturing method was proposed. The H08Mn2Si mild steel wire and the H06MnNi3CrMoA high-tensile steel wire were fed into the molten pool simultaneously. The tests were carried out to adjust the components， microstructures， and properties of the deposited metals. The results show that the quantity of granular bainite and acicular ferrite in the deposited metals increases with the mass fraction of high-tensile steels， which improves the tensile strength and microhardness of the deposited metals. The ranges of tensile strength and microhardness are as 558~885 MPa and 197HV~390HV， respectively. Finally， the induction teeth structure of low carbon steel/high strength steel was fabricated by the proposed method. The hardness gradient was realized between the two materials through the component gradient transition， which mitigates the interface mismatch problems.

Reverse Identification of Johnson-Cook Constitutive Parameters of 316H Stainless Steels Considering Thermoplastic Deformations

LI Xiuru, WEI Zhaocheng, GUO Minglong, WANG Minjie, GUO Jiang, GAO Wei, SUN Fang

2022, 33(07): 864-871. DOI: 10.3969/j.issn.1004-132X.2022.07.014

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The constitutive model might characterize the dynamic response of materials in the deformation processes, and the accuracy of constitutive model played a determinant role in analytical prediction of cutting forces, cutting temperature in machining. Aiming at the problems of lack for constitutive model of 316H stainless steels, a Johnson-Cook(J-C) constitutive parameter reverse identification method was proposed based on metal cutting theory. By establishing mathematics models of stress, strain, strain rate, and temperature distribution in unequal principal shear zones, and combining with the data of quasi-static compression tests and orthogonal cutting tests, the constitutive parameters of 316H stainless steel were reversely identified by particle swarm optimization algorithm. The cutting force prediction model was used to verify the feasibility of the reverse identification method and the reliability of the constitutive model.

Properties at Elevated Temperature and High Strain Rate and Establishment of Johnson-Cook Constitutive Model for GH2132

TIAN Xianhua, YAN Kuicheng, ZHAO Jun, WANG Qingqing, WANG Yanqing, CHEN Xiaoran,

2022, 33(07): 872-881. DOI: 10.3969/j.issn.1004-132X.2022.07.015

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Quasi-static compression tests and SHPB tests were carried out on superalloy GH2132, and the stress-strain curves of the materials at different temperatures and strain rates were obtained, and then the mechanics behavior were analyzed. GH2132 has a work hardening and unconspicuous yield stage in quasi-static compression processes. During the SHPB tests, GH2132 shows significant temperature strengthening effectiveness as the strain rate is between 4000 s-1 and 8000 s-1, while the material exhibits strain rate softening effectivenes as the strain rate is between 8000 s-1 and 10 000 s-1, and strain rate softening effectivenes is shown. By modifying temperature softening coefficient and strain rate strengthening parameter, the Johnson-Cook constitutive model of GH2132 with high temperature and high strain rate was established.

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