Table of Content

25 February 2023, Volume 34 Issue 04

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Review on Management at Mechanical Design and Manufacturing Discipline of NSFC in 2022

YE Xin, ZHU Mingliang, HUANG Zhiquan,

2023, 34(04):  379-386.  DOI: 10.3969/j.issn.1004-132X.2023.04.001

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The applications， evaluations and funding of projects at mechanical design and manufacturing discipline （division Ⅱ of engineering science） of the NSFC in 2022， as well as the research progresses and achievements of the executing and finished projects were reviewed. Specific measures of mechanical design and manufacturing discipline were illustrated， such as the reform of scientific fund， talent cultivation and future research. Finally， a short prospect of the work in 2023 was introduced. 

Calculation of Solid Cylinder Pore Defect Depth in Hot Shaft Forgings by Improved Fireworks Algorithm

SHEN Jiuli, ZHANG Yucun

2023, 34(04):  387-394.  DOI: 10.3969/j.issn.1004-132X.2023.04.002

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In view of the difficulty in measuring the solid cylinder pore defects in hot shaft forgings at high temperature, a method for detecting the depth of pores was proposed based on the improved fireworks algorithm. Firstly, according to the internal micro element model of forgings and the heat transfer differential equation of transient temperature field, the differential equation of the relationship between the temperature field of the solid cylinder pore and the radius of the pore was derived, then the differential equation was solved by the separation variable method. Secondly, the fireworks algorithm was improved to improve the depth detection accuracy of the solid cylinder pores. Then the objective function of defect depth was constructed for testing, and the relative error of the optimal solution is as 2.5%. Finally, the same pore depth was detected by the proposed method, the PSO algorithm and the traditional fireworks algorithm respectively in order to verify the feasibility of the proposed algorithm.

Optimal Design of Tracking Mechanisms for a New Type Dish Solar ConcentratorLIU Fanmao

LIAO Cancan, ZHANG Yuanyuan, MO Han

2023, 34(04):  395-403.  DOI: 10.3969/j.issn.1004-132X.2023.04.003

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A general 3-RPS parallel mechanism was proposed herein， whose moving platforms and fixed platforms were similar arbitrary triangles， and the axis of rotation pair was perpendicular to the connecting line between the center and the vertex of the fixed platform. Then mechanism， a new dish solar concentrator was designed. The closed vector method was used to obtain the inverse kinematic position solution of the mechanism. Then the screw theory was used to analyze the speed mapping relationship between the input and output of the mechanism， and the Jacobian matrix of the mechanism was established. Taking global dexterity， global stiffness and global bearing capacity as optimization indexes， the optimal design of structure parameters of the mechanism were obtained by genetic algorithm， and the radius of the fixed platform of the mechanism was determined. The distribution of each performance index in the reachable workspace of the mechanism before and after optimization was quantitatively compared and analyzed by means of the performance map method， and the static verification analyses of the mechanism before and after optimization were carried out by ANSYS software. Results show that the dexterity， stiffness and bearing capacity of the new type dish solar tracking platform are improved in varying degrees when the fixed platform radius is as 860 mm. 

Dynamics Simulation and Experimental Study of Industrial Assembly Anti-vibration Exoskeletons

CHEN Yupeng, WANG Haibo, XUE Chaojun, ZOU Huaijing, GAO Yimin,

2023, 34(04):  404-413.  DOI: 10.3969/j.issn.1004-132X.2023.04.004

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 An upper limb wearable industrial assembly anti-vibration exoskeleton was proposed as an intervention measure for hand-arm vibrations. A parametric human-machine coupling simulation model was established by ADAMS. To optimize the structural parameters of the exoskeleton damping units， a single-factor vibration response analysis was conducted on the exoskeleton damping unit structures. It is found that the damper damping coefficient and installation positions were the key factors affecting the damping performance of the exoskeletons， and the front and rear spring stiffnesses of the shear damping structure were better when taken differently. The best combination of the modified factor levels was obtained through cross-orthogonal tests. The vibration reduction performance of the exoskeleton prototype was evaluated by vibration resistance tests using contact pressure and weighted vibration values as indicators. The exoskeletons reduce contact pressure by approximately 39.9% in riveting period and 49.4% in intermittent period. Wearing the exoskeletons reduce the daily contact vibration values by 15.1% and increase the riveting efficiency by up to 18% in a single day. The changes in contact pressure and vibration values demonstrate that the exoskeletons provide vibration reduction and tool support. 

Characterization Model of Critical State of Crack Closure Based on Magnetic Property

XING Haiyan, ZHU Kongyang, ZHANG Po, LIU Chuan, DUAN Chengkai, LIU Weinan, LIU Chao

2023, 34(04):  414-420.  DOI: 10.3969/j.issn.1004-132X.2023.04.005

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Determination and characterization of crack closure under low cycle fatigue loads were difficult in engineering practice. The characterization law and models of critical state of crack closure were studied based on magnetic property parameters. Graded loading and unloading experiments were carried out by using Q235B steel as the experimental materials. The TSC-5M-32 metal magnetic memory detector was used to collect magnetic characteristic parameters. The effects of different plastic zones at the crack tip and the crack tail on the magnetic field were investigated. The changing law of the synthetic magnetic characteristic parameter ΔHp at the critical state of crack closure was analyzed by comparing the critical load of crack closure determined by the flexibility differential method. The results show that the cracks close up when the load is less than Pop critical point， and at the same time ΔHp has a minimum inflection point； the crack is in the closure critical state when the load equals to the Pop， and at the same time ΔHp jumps sharply upward with turning points； the cracks open fully when the load is greater than Pop， and at the same time ΔHp fluctuates around at a higher level. Furthermore， the characterization model of crack closure state was established based on magnetic property parameters. The verification results show that， for the loading and unloading phases， the maximum relative errors between the model predicted values and measured values are 9.398% and 11.549% respectively， which provides a new method to judge and characterize the crack closure states for engineering practice. 

Design and Control Algorithm for Hexapod Landing Gear of Unmanned Helicopter

LIU Haolin, LIU Xiaochuan, REN Jia, WANG Jizhen, DONG Jiuxiang, FANG Zheng

2023, 34(04):  421-430，439.  DOI: 10.3969/j.issn.1004-132X.2023.04.006

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Unmanned helicopter played an extremely important role in combat, patrol, anti-submarine, rescue and transportation, but the traditional landing gear had higher requirements for take-off and landing environment. Aiming at the problems of adaptive take-off and landing on complex terrains, landing and parking on ship surfaces in harsh sea conditions, and improving survivability of emergency collision, a bionic legs landing gear system of unmanned helicopters was proposed based on multi-link mechanism, and the control algorithm was studied and the modeling and simulation were completed. First from bionic legs quantity, distribution form, DOF configuration and needed to complete the function of the legs, the bionic legs landing gear machinery configuration was analyzed, and the kinematics and dynamics analysis of the hexapod landing gears were completed, and then aiming at the adaptive landing processes of the bionic legs landing gear, buffer landing and terrain modeling algorithm were studied. Finally, a virtual prototype simulation model was built based on the control algorithm to effectively complete the landing simulation and prototype test of various terrains. The results show that the design of the bionic legs landing gear structure and control algorithm may achieve dynamic adaptive landing and smooth buffering during the landing processes.

Research on Complementary Double-layer Time-grid Angular Displacement Sensor

YANG Jisen, FU Hang, QIN Ziyang, ZHOU Run

2023, 34(04):  431-439.  DOI: 10.3969/j.issn.1004-132X.2023.04.007

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Aiming at the problems of the small amplitude of the induction signals and the low utilization rate of the uniform effective area of the time-varying magnetic field of the double-layer time-grid angular displacement sensors developed in the early stage， a double-layer complementary time-grid angular displacement sensor was proposed based on the original “figure-eight” half-sine structure. According to the characteristics of the double-layer time-grid displacement sensors， the spatial magnetic field distribution models were established， and the advantages of the complementary structure of the double-layer time-grid angular displacement sensors in forming traveling waves were verified. According to the magnetic field distribution of the excitation coil， the space between the double-layer planar excitation coil under this parameter state was as 0.235 mm. Finally， finite element simulation analysis and experimental verification were carried out. The simulation results show that the complementary structure may effectively increase the induction signal intensity， the peak-to-peak values of the short-period errors are significantly reduced， which may effectively suppress the 1st harmonic and the 4th harmonic in the angle errors. The experimental data shows that the original short-period error of the sensors is （-13.61″， 13.30″）， and the corrected error is （-3.01″， 0.78″）； the original long-period error of the sensor is （-19.60″， 21.96″）， and the corrected error is （-2.62″， 3.30″）， which reduces the primary errors by 66.3% compared to the single-layer “U”-shaped structure， the 4th time error is reduced by 25.3%. 

Research on Torsional Multi-directional Piezoelectric Vibration Energy Harvesters

KAN Junwu, WU Yaqi, ZHANG Zhonghua, HE Hengqian, MENG Fanxu

2023, 34(04):  440-445.  DOI: 10.3969/j.issn.1004-132X.2023.04.008

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In order to effectively harvest multi-directional vibration energy， a torsional multi-directional piezoelectric vibration energy harvester（PVEH） was proposed. Both the finite element simulation and experimental evaluation were conducted to figure out the output voltage characteristics of the PVEH. The variation of resonant frequency and the corresponding amplitude at different excitation angles（angle between the excitation direction and the X axis in the XOY plane） is found. The results show that the changes of excitation angles have little influence on the two-order resonant frequency， but have a great influence on the output voltages with different rules. When the excitation angles increased from 0° to 90°， the first-order resonant voltage decreases and the second-order resonant voltage increases； when the excitation angle is as 44°， the two-order resonant voltage is equal. To verify the feasibility of the PVEH used in practical applications， the capacitor charging characteristics and the output power characteristics was studied experimentally. When the PVEH was excited along the X axis and Y axis， the storage energy rates of capacitors may reach 0.58 mJ/s and 0.54 mJ/s respectively. When excited along the X-axis and Y-axis directions， there are two optimal resistances to maximize the output power. On the X-axis excitation direction， there are two optimal resistance values of 17 kΩ and 81 kΩ， corresponding to the output power of 4.56 mW and 3.4 mW， respectively， On the Y-axis excitation direction， there are two optimal resistance values of 17 kΩ and 61 kΩ， corresponding to the output power of 3.96 mW and 3.89 mW， respectively. 

Research on Laser Remanufacturing Method and Experiments of Valve Core Parts

SHU Linsen, GONG Jiangtao, DONG Yue, SU Chengming, WANG Xin

2023, 34(04):  446-453.  DOI: 10.3969/j.issn.1004-132X.2023.04.009

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 In order to achieve high-quality repair of damaged valve core parts， a remanufacturing process method was proposed based on geometric reconstruction and path-pose planning. The principles of remanufacturing boundary preprocess were introduced to design the geometric characteristics of damaged parts in valve core and the implementation steps were described in detail. The boundary surface and the three-dimensional model of the valve core to be repaired were reconstructed with high precision based on NURBS theory. The remanufacturing processing path was generated using a cross-sectional plane method， and each interpolation point coordinates were calculated according to the line approximation and the error control principles. The spot area was combined with the interpolation point gesture to determine the dynamic positions of laser spray head. An ABB robot simulation system was used to verify the correctness of the laser cladding paths and the laser spray head positions. Subsequently， the remanufacturing experiments of valve core parts were performed through the execution code generated by the simulation system. The results show that the planned path and positioning in the method may effectively follow the remanufacturing boundary surface in valve core parts. The formed molten coating is relatively dense and does not find pores and cracks. The coating grain size and average hardness are as 14～54 μm and 573.6HV0.5±51.8HV0.5， respectively. The erosion resistance of the coating is improved by 30.8%. The processing method may meet the remanufacturing requirements of damaged valve core parts. 

Cutting Performance of Coated Tools and Machined Surface Integrity in Superalloy Clean Cutting

LI Xiang, ZHENG Guangming, YAN Pei, SUN Zuomin, CHENG Xiang, LIU Huanbao

2023, 34(04):  454-463.  DOI: 10.3969/j.issn.1004-132X.2023.04.010

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 In the high-speed dry cutting processes of superalloy， there were some prominent problems， such as serious tool wear， poor machining surface quality and so on. The experiments of high-speed milling of superalloy GH2132 were carried out with cemented carbide coated tools based on clean cutting technology. The effect laws of dry cutting and various injection temperatures of liquid nitrogen on the cutting performance of the coated tools and the integrity of the machined surface were studied， and the feasibility of using clean cutting superalloy to improve the life of the coated tools and the machined surface quality was investigated. The research shows that the cutting forces by liquid nitrogen cryogenic cutting GH2132 increase with the decrease of the injection temperature. The cutting temperature of the cutting zone completely reaches a low temperature condition when the injection temperature is as -150～-190 ℃. With the decrease of liquid nitrogen injection temperature， the peeling areas of the coating are obviously reduced， and the adhesive wear and oxidative wear are reduced. A longer tool life may be obtained under the injection condition of -150 ℃. The lower machined surface roughness Sa may be obtained under the injection condition of -30～-150 ℃. With the decrease of injection temperature， the work hardening and residual tensile stress are increased and decreased， respectively. Compared with the dry cutting， liquid nitrogen cutting injection temperature at -150～-190 ℃ may significantly improve the coated tool life and machined surface quality. 

Forming Law of Multi-degree-of-freedom Rotary Forging for High-rib Thin-plate Components and Process Planning

CHEN Zhongbao, HAN Xinghui, ZHUANG Wuhao, HU Yaxiong, CHEN Mingzhang,

2023, 34(04):  464-474.  DOI: 10.3969/j.issn.1004-132X.2023.04.011

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The metal flow was very complicated in the multi-degree-of-freedom rotary forging processes for the high-rib thin-plate components， which led to the uneven distribution of the ribs heights. According to the motion principle of double eccentric rotary forging machines， the evolution law of contact pattern between rotary dies and billet was studied when rotary die moved with circular trajectory and spiral trajectory， and the mathematical calculation method of contact zone shape was proposed. The law of metal flow and the growth law of high ribs under circular trajectory rotary forging and spiral trajectory rotary forging were revealed by the finite element simulation， and the correlation between the motion of rotary die， contact zone， metal flow and the growth of high ribs were expounded. The rotary forging experiments of the high-rib thin-plate component were carried out. The results show that， compared with the circular trajectory rotary forging， the spiral trajectory rotary forging may weaken the radial metal flowing and tangential metal flowing， enhance the axial metal flowing， so as to obtain the high-rib thin-plate components with uniform rib heights. 

Research on Pulse Current-assisted Tensile Deformation of SUS304 Ultra-thin Strips

FAN Wanwan, LIU Qi, LIU Wenwen, WANG Tao, WANG Tianxiang

2023, 34(04):  475-480，489.  DOI: 10.3969/j.issn.1004-132X.2023.04.012

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To study the effects of pulse current on the tensile deformations of SUS304 ultra-thin strips， room temperature tensile， electric tensile and electric air-cooled tensile tests were carried out. The effects of thermal effect and non-thermal effect on the macro-mechanics properties and microstructure were analyzed. The results show that thermal effect and non-thermal effect exist simultaneously in the processes of pulse current-assisted tensile deformation of SUS304 ultra-thin strips， and the thermal effect leads to the reduction of flow stress. The non-thermal effect restrains the TRIP effect， promotes the TWIP effect and changes the plastic deformation mechanism of the SUS304 ultra-thin strips. There is no coordinated plastic deformation of high-strength martensite， which leads to the premature plastic instability of samples， where the tensile strength of the sample decreases by 12.2% and the elongation at break decreases by 44.7%. The non-thermal effect makes the strip recover and recrystallize at a lower temperature. The pulse current induces the transition of SUS304 ultra-thin strips from ductile fracture to ductile-brittle fracture mode， and promotes the formation of deformed texture. 

Sensitivity Analysis and Adaptive Tracking Control of Electro-hydraulic Active Suspensions

CHEN Hao, GONG Mingde, ZHAO Dingxuan, ZHANG Wei, ZHANG Yue, HAO Chunyou,

2023, 34(04):  481-489.  DOI: 10.3969/j.issn.1004-132X.2023.04.013

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 Emergency rescue vehicles carried heavy loads and travel on complex roads and the response and control accuracy of output forces of electro-hydraulic active suspensions were very important to attenuate vibrations. Firstly， the mathematical model of electro-hydraulic active suspension system was established. Secondly， the trajectory sensitivity equation of the system was established to give the sensitivity of the main parameters with the force step response， so as to provide a theoretical basis for the performance optimization. Thirdly， considering the large load characteristics of electro-hydraulic active suspensions and the sensitivity analysis results， a reference model adaptive controller was designed. Finally， the adaptive control effectiveness was verified by experiments. The results show that the proposed control method effectively improves the tracking performance and the force control accuracy of the electro-hydraulic active suspension actuator units. It will help the vehicle active suspension system to realize various advanced control algorithms. 

Semi-active Control of Hydro-pneumatic Suspensions for Mining Dump Trucks Based on Grey Wolf Algorithm

SUN Dong, WANG Ruochen, DING Renkai, CHEN Yijie

2023, 34(04):  490-497.  DOI: 10.3969/j.issn.1004-132X.2023.04.014

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 A valve-controllable semi-active hydro-pneumatic suspension system was proposed to coordinate the contradictions between the ride comfort and road friendliness of a mining dump truck. The AMESim physical models of the hydro-pneumatic spring considering the friction were established for the first time. The polynomial mechanics models of the controllable damping valve were built. The modified skyhook control strategy was designed by taking the driving voltage of the controllable damping valve as the semi-active control object. And two key control parameters of the strategy were optimized based on the grey wolf optimization algorithm. The co-simulation results show that the body acceleration of the proposed suspension systems is decreased by 11.4% while the tire dynamic load is slightly deteriorated by 1.1% on the D-class random roads. Compared with the traditional skyhook control， the modified skyhook strategy attains the better trade-off between the ride comfort and road friendliness of a mining dump truck. The hardware-in-loop test results also verify the effectiveness and feasibility of the proposed control scheme. 

Preventive Maintenance Decision Model for EMU Components Considering Dynamic Depreciation Costs

LI Jing, WANG Hong, HE Yong, XIONG Lü, QI Yankun

2023, 34(04):  498-503.  DOI: 10.3969/j.issn.1004-132X.2023.04.015

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Aiming at the components that needed to be replaced during the EMU maintenance(Level Ⅳ), the influences of the value change of the components on the maintenance decision were studied. Based on the current multi-level imperfect maintenance actions of EMU in China, a bi-level imperfect preventive maintenance optimization model was established considering dynamic depreciation costs. The proposed model calculated the depreciation costs of components through the equivalent service age. And the maintenance decisions were further investigated considering the relationship between depreciation costs and the failure rate. It is shown that compared with the maintenance model without considering the depreciation costs, the proposed model takes into account the influences of the production operations and maintenance activities on the maintenance decisions. It may better balance the preventive maintenance cost and failure maintenance cost，and achieve more economical.