China Mechanical Engineering

Ultrasonic Impact Strengthening of Titanium Alloys：State-of-the-art and Prospectives

ZHA Xuming, YUAN Zhi, QIN Hao, XI Linqing, ZHANG Tao, JIANG Feng

2023, 34(19): 2269-2287. DOI: 10.3969/j.issn.1004-132X.2023.19.001

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This review started with the introduction to the principles and research progresses of the ultrasonic impact strengthening technology for titanium alloys. The influences of the properties of titanium alloys were investigated, which was associated with the different parameters of ultrasonic impact strengthening processes（static pressure， ultrasonic amplitude and numbers of rolling）. Results show that the optimization of different processing parameters has a significant improvement on the performance strengthening of the titanium alloys. However， there is a critical value of the different processing parameters. Once the critical values are exceeded， continuing to increase the parameter values will reduce the service performance of the titanium alloys. Finally， the difficulties of ultrasonic impact strengthening technology which used in the engineering applications were summarized. Combined with the development of intelligent manufacturing， the future development of ultrasonic impact strengthening technology was prospected.

Derivation Mechanism of Cyclic Alternating Dynamic Pressures in Linear Hydrodynamic Polishing Flow Fields

XIE Zhong, WEN Donghui, CHENG Zhichao, KONG Fanzhi

2023, 34(19): 2288-2295. DOI: 10.3969/j.issn.1004-132X.2023.19.002

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Aiming at the periodic polishing flow fields formed between the structured polishing roller and the workpiece surface in LHP， the dynamic pressure action rules of workpiece surfaces were studied in this flow field. The fluid dynamic pressure mathematical model was derived by taking the flow field of the wedge groove rollers as an example based on the hydrodynamic lubrication mechanism， and the global mathematical model of dynamic pressure that was changing with time was established during the LHP processes. The dynamic pressure distribution curve of the flow field was drawn by MATLAB programming language used the global mathematical model and compared with the simulation results of CFD. Furthermore， based on the influences of polishing parameters（polishing rotation speed， polishing gap and polishing slurry concentration）on dynamic pressures and the adjustment effects of workpiece feed speeds on the dynamic pressure periods at different polishing rotation speeds， a derivation mechanism of cyclic alternating dynamic pressures in the LHP flow fields was established to realize the adjustment function of the dynamic pressures and the pressure uniformity on the polished workpiece surfaces.

Research on Magnetic Field Compensated Double-layer Time-grating Angular Displacement Sensors under Structural Parameter Constraints

YANG Jisen, ZHOU Run, ZHANG Tianheng, LU Yu, WU Zhuo, ZHANG Di, ZHANG Jing

2023, 34(19): 2296-2303，2312. DOI: 10.3969/j.issn.1004-132X.2023.19.003

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Time-grating angular displacement sensor was widely used in angle measurement of CNC machine tools， industrial robots and other fields. In order to solve the problems of asymmetrical distribution of time-varying magnetic field in the measuring processes of double-layer time-grating angular displacement sensors， a magnetic field compensation driving scheme was proposed. In this scheme， a double-layer planar coil was excited by different layers and amplitudes to improve the symmetry of the time-varying magnetic fields. Firstly， a parameterized mathematical model of the time-varying magnetic fields of the sensor was established， and the relationship between the amplitude ratio of the excitation signals of the two layers and the structural parameters of the sensors was determined according to the idea of magnetic field compensation. Secondly， the simulation model and the sensor experimental system were constructed. Finally， a comparative simulation and experimental analysis of the original driving scheme and the magnetic field compensation driving scheme were designed. According to the simulation data， the magnetic field compensation driving scheme optimizes the magnetic field distribution， and effectively reduces the amplitude difference of the induced electromotive forces at the complementary positions in the sensor pitch， and the measurement errors in the pitch of the double-layer time-grating angular displacement sensors are reduced by 37.4%. The experimental data show that the magnetic field compensation driving scheme may reduce the intra-pitch measurement error to（-20.8″， 12.6″）. Therefore， the effectiveness of the magnetic field compensation driving scheme was verified by comparing the simulation and experimental data.

Performance Analysis and Optimization Design of 2PPaPaR Parallel Mechanism

PU Zhixin, GUO Jianwei, PAN Yuqi, BAI Yangxi

2023, 34(19): 2304-2312. DOI: 10.3969/j.issn.1004-132X.2023.19.004

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A new type of 4-degree-of-freedom(4-DOF) 3T1R parallel mechanism—2PPaPaR parallel mechanism was proposed, which had the characteristics of simple structure, symmetrical configuration, large workspace, high positioning accuracy and good dexterity, and might be widely used in sorting, handling and packaging operations. The number and types of DOF of the mechanism were verified based on the screw theory. By analyzing the configuration, the forward and inverse kinematics solution modules were obtained based on the closed-loop vector method, and were validated by calculating examples of forward and inverse solutions. With the inverse kinematics as the constraint conditions, the reachable workspace and the possible workspace shapes were discussed based on numerical method. The Jacobian matrix was established by analyzing the input and output velocity characteristics of the mechanism. Then the singularity of the mechanism was analyzed, and several typical singular configurations were given. Finally, taking the three performance evaluation indicators of reachable working space, positioning accuracy and operability degree as the objective function, the particle swarm algorithm was used to optimize the design of the geometric dimensional parameters. Compared with the original mechanism, it is discovered that the kinematic performance of the optimal mechanism is significantly improved, which provides reference for the subsequent prototype constructions.

Effects of Dynamic Stabilization Operation Parameters on Ballast Stability

ZHAO Zemin, WANG Lihua, HUANG Hongyi, CHEN Taimao, JIANG Wei

2023, 34(19): 2313-2319，2369. DOI: 10.3969/j.issn.1004-132X.2023.19.005

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To improve ballast stability, the dynamic stabilization unit-ballast coupling models were established using the discrete element-finite element coupling method. The orthogonal test method was used to analyze the significance and sensitivity of the operation parameters with the dynamic stabilization operation parameters as the research factors and the ballast compactness and settlement as the evaluation indexes. The dynamic stabilization unit test rig was built to verify the rationality of the simulation models. The simulation and experimental results show that the significant influences of dynamic stabilization operation parameters on ballasted are as follows: the effects of the amplitude of the excitation force are greater than that of the excitation frequency, and the effects of the excitation frequency are greater than that of the vertical downward pressure. The dynamic stabilization optimal operation parameters are as excitation frequency of 35 Hz and as excitation force amplitude of 197 kN.

Experimental Study of Portable Pneumatic Milling for Battle Damages of Aircraft Titanium Alloy Skins

GAO Kun, REN Yanxiu, ZHU Yue, QI Lehua, LUO Jun

2023, 34(19): 2320-2326. DOI: 10.3969/j.issn.1004-132X.2023.19.006

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Aiming at the problems that war-damaged aircraft titanium alloy skin damages were difficult to be efficiently cut， a novel in-situ cutting and repair process of pneumatic milling combined with CMJ lubrication was proposed. Through the developed aircraft skin portable pneumatic cutting test platform， the thin-walled titanium alloy pneumatic milling tests were carried out. The test results show that when the titanium alloy skin with a thickness of 1.5 mm is milling， the pneumatic motor may work in the best power range by using the up milling method， the 10 mm diameter milling cutter， and the milling width ae of 13 mm. With CMJ lubrication， re-cutting 12 times after each cutting with the same milling width may improve the tool life and cutting-edge shape accuracy. A prefect hole in a damaged specific aircraft skin was successfully prepared by using the portable pneumatic milling and cutting device and processing parameters developed herein， which provides a practical novel technology for repairing titanium alloy damages in aircrafts.

Ultrasonic Nondestructive Testing and Evaluation of CFRP Hole-making Structures

YANG Liang, CAI Guixi, LIU Fang, LI Jiankui

2023, 34(19): 2327-2332. DOI: 10.3969/j.issn.1004-132X.2023.19.007

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In order to realize the nondestructive testing and evaluation of the hole-making structure of CFRP, a portable ultrasonic C-scan tester was developed based on the principle of ultrasonic pulse reflection method, a spiral scanning method was proposed, and a mathematical model for the quality evaluation of the hole-making structures was established. By performing ultrosonic inspection tests on artificial specimens and in-service pores, based on the static distance principle, the centroid of the irregular ultrasonic C-scan image was determined. The longest axis of the centroid was extracted, and the ratio of the longest axis to the nominal diameter of the hole(RLN) was calculated to evaluate the quality of the holes. The results show that the method may greatly improve the detection speed. The measured values of stratified defect are equivalent to the actual ones. The results are consistent with the actual morphologies of in-service pores. The RLN factor may accurately evaluate various types of stratification defects.

Exergy Efficiency Analysis and Evaluation Model of Dry-cutting Machine Tools Considering Cooling Energy Consumption

WANG Qianyue, CAO Huajun, LIN Jianghai, LAI Kexu, LI Benjie, GE Weiwei

2023, 34(19): 2333-2342. DOI: 10.3969/j.issn.1004-132X.2023.19.008

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To study the cooling energy consumption used to keep the heat balance of machine tools and to more accurately reveal the potential in energy efficiency improvements for machine tools， the exergy analysis of dry-cutting machine tools and their cooling systems was analyzed， and exergy efficiency indicators of machine tools were proposed. An exergy efficiency evaluation model of machine tools was established considering the energy consumption for material removal and cooling， and the feasibility and reliability of this model were verified with the case study of high-speed dry gear hobbing. The results show that exergy efficiencies of all the cooling devices for high-speed dry gear hobbing machine tools are below 30% and the exergy losses are high. In order to improve the energy efficiency of machine tools， the exergy losses of the air filters and the air compression stations should be reduced, the exergy efficiency of the air compression stations and the hydraulic stations should be increased. This paper may provide theoretical support for the evaluation and energy-saving optimization of the precision green operations for dry-cutting machine tools.

Lightweight Design of Protective Structures of Battery Packs for Bottom-scraping Safety

WANG Chao, CHENG Aiguo, ZHANG Chenglin, YU Wanyuan, HE Zhicheng

2023, 34(19): 2343-2352. DOI: 10.3969/j.issn.1004-132X.2023.19.009

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To protect the battery pack from bottom-scraping， a section-layout design method for aluminium alloy protective structures was proposed. Firstly， a simulation model of the bottom-scraping of the vehicle was established and the intrusion target of the battery pack module was defined. The accuracy of the material was verified by three-point static pressure tests and simulation analysis on the anticollision beam. Secondly， the “人” glyph optimal cross-section was determined through topology optimization. Then the effects of different section shapes， installation positions and layout parameters on the bottom-scraping performance were compared and analyzed. The mechanism of bottom-scraping protection was investigated. Finally， hybrid approximation models were constructed and the MOMPA was used to optimize the section-layout of the structures. The results show that the two optimized aluminium alloy protection structures are 59.6% and 46.8% lighter than the original steel structures， respectively， and the battery module intrusions meet the requirements.

Study on the Influences of Bending Methods on Springback in Roll Forming Processes

HAN Fei, SUN Weilong, ZHANG Ruoqing

2023, 34(19): 2353-2361. DOI: 10.3969/j.issn.1004-132X.2023.19.010

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In order to study the influences of different bending methods on springback in roll forming processes， the effects of different bending methods， fillet radius and sheet thickness on springback were analyzed by combining the experimental method with finite element simulation. The stress and strain distribution in the roll forming processes with different bending methods was analyzed， and the springback mechanism of roll forming was revealed. The results show that according to the design principles of different bending methods（constant radius method and constant length method）， the differences between the fillet radius and the arc length of different bending sections in the design are the main factor that affect the difference of the stress-strain distribution and springback for the two methods； the springback amount of the constant bend radius method increases with the increase of the number of passes and the increment also rises； the springback of the constant arc length method does not change significantly with the increase of the number of passes， and the amplitude is greater than that of the constant bend radius method； in both bending methods， the springback increases with the increase of fillet radius and decreases with the sheet thickness increase.

Reverse Identification of Constitutive Parameters of ZM5 Magnesium Alloy Based on Unequal Shear Model#br#

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WANG Fulin, XIAO Qiang, LAI Shuning, TANG Nengyi

2023, 34(19): 2362-2369. DOI: 10.3969/j.issn.1004-132X.2023.19.011

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In order to solve the problems of missing dynamic mechanics parameters of ZM5 magnesium alloy， a reverse identification method of J-C constitutive parameters of the alloy was proposed based on unequal shear region theory. According to the metal cutting theory， the stress， strain， strain rate and temperature distribution model of the main shear zone were established， the orthogonal cutting experiments and the quasi-static tensile experiments were combined， and the J-C constitutive parameters of ZM5 magnesium alloy were determined by mixed particle swarm algorithm and applied to the simulation. Finally， the obtained simulation values are compared with the experimental ones， and the J-C model parameter simulation may betterly reflect the cutting forces and cutting temperature in the actual cutting experiments， so as to prove the feasibility of the reverse identification method adopted herein.

Levitation Force Characteristics and Parameter Optimization of Permanent Magnet Tracks

ZHANG Mingliang, YANG Dawei, LI Mingyuan, YANG Xinmeng, LIU Liru, ZHANG Lianpeng

2023, 34(19): 2370-2380. DOI: 10.3969/j.issn.1004-132X.2023.19.012

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Facing on the high temperature superconducting flux pinned maglev trains， a method of optimizing permanent magnet tracks was proposed by Taguchi orthogonal method. The influences of Halbach double peak permanent magnet tracks size on magnetic field was studied by finite element method， and the influencing factors were optimized in order to obtain the comprehensive magnetic field performance. A method of equivalent treatment of high-temperature superconductors(abbreviation for equivalent treatment method) was proposed based on frozen image mode， and the correctness of the equivalent treatment method was verified by experimental data. The results show that the influences of the height of the permanent magnet tracks on the average magnetic flux intensity and the average magnetic flux intensity per unit mass are far greater than that of the sectional width， and the pure iron thickness is a non-significant factor. Based on the equivalent treatment method， it is found that the suspension forces increase as the suspension gaps decrease. The suspension forces provided by the optimized permanent magnet railway are of 1.5 times that provided by the experimental permanent magnet tracks， the suspension stiffness increases rapidly as the number of rows of high temperature superconductors increase.

Parameter Identification Strategy of Yield Criterion for Accurately Predicting Anisotropic Behaviors under Near Plane Strain Loading

DU Kai, REN Yanqiang, HOU Yong, LI Xiaoqiang, CHEN Shuaifeng, SUN Liang, ZUO Xiaojiao, YUAN Xiaoguang

2023, 34(19): 2381-2393. DOI: 10.3969/j.issn.1004-132X.2023.19.013

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With the increasing demands for forming accuracy of stamped parts in the modern automobile industries， the accuracy of models describing the deformation behavior of commercial sheet metals should be improved accordingly. In the context， a parameter identification strategy was proposed based upon uniaxial tension， equi-biaxial tension， and near-plane strain data to calibrate advanced anisotropic yield criteria， combined with current industrial laboratory testing capabilities. The newly proposed calibration method was applied to the BBC2008 yield criterion and compared with several other yield criteria， including the widely used Hill48 and Balat89 in the industry， as well as Yld2004-18p， Yld2011-27p， Yoshida2013， and Poly4*Hosford， which had similar flexibility to BBC2008. The effectiveness and applicability of the new parameter identification strategy were verified by quantitatively evaluating the predicted errors of the yield loci in the normal and diagonal planes， equi-biaxial and uniaxial tensile yield stresses， and plastic strain rations for MP980 and SPCE steels， as well as 5182-O and A6XXX-T4 aluminum alloys. The results show that the new method may comprehensively improve the ability to describe plastic anisotropy， especially for diagonal plane shear yield loci. There are significant differences in the ability of different yield criteria to describe the anisotropic behavior of commercial sheet metals. In particular， under the premise of calibrating yield criteria with the same mechanics properties data， releasing the potential adjustment ability of the exponent is more important than increasing the number of material parameters.

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