Table of Content

25 April 2024, Volume 35 Issue 04

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Review on Management at Mechanical Design and Manufacturing Discipline of National Natural Science Foundation of China in 2023

YE Xin, HUANG Zhiquan, ZHANG Junhui,

2024, 35(04):  571-579.  DOI: 10.3969/j.issn.1004-132X.2024.04.001

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 The applications, evaluations, and funding of several types of projects that were classified into the talent and exploratory funding categories at mechanical design and manufacturing discipline (division Ⅱ of engineering science) of the National Natural Science Foundation of China in 2023, as well as the research progresses and findings 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 2024 was introduced．

Vibration and Lubrication Characteristics of Railway Vehicle Axle Box Bearings under Wheel-rail Excitation

MA Qiaoying, YANG Shaopu, LIU Yongqiang,

2024, 35(04):  580-590.  DOI: 10.3969/j.issn.1004-132X.2024.04.002

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An axle box bearings coupled with a railway vehicle model was developed based on Hertz contact and elastohydrodynamic lubrication theory. The effects of wheel-rail excitations on the vibration and oil film stiffness characteristics of axle box bearings were investigated. MATLAB/Simulink and UM were used to establish the bearing dynamic model and the railway vehicle model, respectively. The coupling relationship between the two was realized through the interaction force. The typical fault forms of bearings and wheelsets were simulated, and the impacts of these faults on bearing vibration and lubrication characteristics were analyzed in detail. The results show that lubrication may effectively reduce bearing vibrations. The partial bearing faults may increase the oil film stiffness, and bearing faults and wheel flats have a significant impact on lubrication. In addition, wheel-rail excitations reduce the vibration ratio of the bearing outer ring while increasing the vibration of other vehicle components and little effects on the vibrations of the car body.

Research on Dynamic Modeling and Decoupling Methods of Planetary Gear Trains in Wind Turbine Gearboxes with Journal Bearings

TANG Hao, TAN Jianjun, LI Hao, ZHU Caichao, YE Wei, SUN Zhangdong

2024, 35(04):  591-601.  DOI: 10.3969/j.issn.1004-132X.2024.04.003

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In the dynamic modeling of planetary gear trains, the influences of nonlinear oil film forces or linear stiffness damping forms on system dynamics characteristics were often considered. The former had high simulation accuracy but high computational costs, and the latter had high computational efficiency but ignores the time-varying effects of oil film forces and journal sleeve eccentricity, resulting in limited simulation accuracy. Therefore, a 2MW wind turbine gearbox was taken as the research object herein. A time-varying linear stiffness damping model of the journal bearing was established, and a calculation method for the additional eccentricity correction force of the journal bearing considering the time-varying eccentricity of the journal sleeve was proposed. Then, the time-varying linear stiffness damping model was coupled with the additional eccentricity correction force by using the coordination relationship between the carrier-pin and planet. Finally, a dynamic model of the planetary gear trains in wind turbine gearboxes using journal bearings was established, and the effects of operating conditions and bearing parameters on the calculation accuracy and dynamic system responses were compared and verified through experiments. The results indicate that the fluctuation of dynamic meshing force in gear pairs may cause periodic changes in the stiffness damping coefficient and additional eccentricity correction force of journal bearings. The proposed model may effectively predict system responses, especially planetary gear vibration responses, under stable and transient operating conditions. Reducing the width-diameter ratio and gap, increasing input torque may improve the system's load sharing performance.

A GPU-accelerated High-efficient Multi-grid Algorithm for ITO

YANG Feng, LUO Shijie, YANG Jianghong, WANG Yingjun,

2024, 35(04):  602-613.  DOI: 10.3969/j.issn.1004-132X.2024.04.004

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 An efficient multi-grid equation solving method was proposed based on the h-refinement of splines to address the challenges posed by large-scale ITO computation and low efficiency of traditional solving methods. By the proposed method, the weight information obtained through h-refinement interpolation between coarse and fine grids was used to construct the interpolation matrix of the multi-grid method, thereby enhancing the accuracy of mapping information for both coarse and fine grids and improving computational efficiency. Additionally, a comprehensive analysis of the multi-grid solving process was conducted, culminating in the development of an efficient GPU parallel algorithm. Numerical examples illustrate that the proposed method outperforms existing methods, demonstrating speedup ratios of 1.47, 11.12, and 17.02 in comparison to the linear interpolation multi-grid conjugate gradient method algebraic multi-grid conjugate gradient method, and pre-processing conjugate gradient method respectively. Furthermore, the acceleration rate of GPU parallel solution surpasses that of CPU serial solution by 33.86 times, which significantly enhances the efficiency of solving large-scale linear equations.

Design and Parameter Optimization of Slicing Machines Based on New Rotary-straight Line Reciprocating Mechanisms

HU Fuqing, SUN Jianghong, SUN Yingjie, SUN Yutong, MA Chao, ZHOU Fuqiang,

2024, 35(04):  614-623，635.  DOI: 10.3969/j.issn.1004-132X.2024.04.005

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Aiming at the problems of low slicing efficiency and quality of the existing pastry slicing machines, the design analysis and parameter optimization of a slicing machine was carried out based on the new rotary-linear reciprocating mechanisms. Firstly, the design of the slicing mechanisms and the calculation of the length-diameter ratio and speed of the elliptical guide rail was carried out. Secondly, the kinematics and the statics analyses were carried out, then, based on the simulation analysis of different aspect ratios and rotational speed dynamics, the cubic polynomial fitting equation of the mean and root mean square value of the cutter acceleration was constructed as the objective function. The NSGA-Ⅱ genetic algorithm was used to optimize the long and short diameter multi-objective parameters, and the rotational speed was selected. Finally, a prototype was built to complete the comparative experiments of different speeds and the performance tests of corn cake slices. The results show that the optimal long and short diameters and rotation speeds are as 190 mm, 120 mm and 20 r/min respectively. After optimization, the cutter efficiency is increased by 75%, the maximum and average errors of the cutter feeding acceleration are reduced by 26% and 49% respectively, and the maximum and arerage errors of retract acceleration are reduced by 60% and 63% respectively. The corn cake section is neat and beautiful, which verifies the feasibility of the design.

Study on Influences of Milling Process Optimization on Residual Stress Distribution for Machining Nickel-based Superalloys

ZHANG Jinyang, XU Weichun, WANG Xiaohan, JIANG Xiaohui, GAO Shan

2024, 35(04):  624-635.  DOI: 10.3969/j.issn.1004-132X.2024.04.006

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The distribution of machining residual stress of nickel-based superalloys had a significant influence on the product quality. To achieve the control method of residual stress, the effects of processing parameters, tool parameters and mechanics-thermal coupling on the residual stress distribution of nickel-based superalloys were studied by means of simulation and experiments. It is found that the change of cutting depth will affect the radial and tangential residual stresses at the same time, and the change of feed rate per tooth mainly affects the residual stress in the feed direction. When the rotating speed increases, the temperature field becomes stronger, the materials are softened, the milling forces are decreased, and the thermal stress is gradually increased. The optimal proportioning scheme is obtained by the method of parameter combination proportioning. Taking the machining of engine blade parts as an example, the method based on parameter optimization may effectively control the residual stress of Nickel-based superalloys.

Experimental Study of Matching of Brush Seal Friction Pairs Based on Frictional Heating Effects

YANG Yixiao, SUN Dan, LAN Kexin, ZHAO Huan, FENG Yuzhong, ZHANG Jieyi,

2024, 35(04):  636-645，690.  DOI: 10.3969/j.issn.1004-132X.2024.04.007

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The frictional heating effects caused by the interaction between brush seal wire and rotor coating directly affected the sealing performance and service life of brush seals. The theory of frictional heating effects between brush seal frictional pairs was analyzed. The experimental device of frictional heating effects between brush seal frictional pairs was designed and built. Six brush seal experimental parts with different structural parameters and brush wire materials and four frictional turntables with different coating materials were designed and processed. The effects of working condition parameters, structural parameters and different frictional pair materials on the frictional heating effects of brush seals were studied experimentally. By comparing and analyzing the maximum temperature of brush seals and the wear morphology and wear amount of frictional pairs before and after wear, the matching relationship between brush wire and rotor coating material was obtained. The results show that the maximum temperature of brush seals increases rapidly and then tends to be stable with the increase of friction time, and increases with the increase of interference. When the interference increases from 0.3 mm to 0.4 mm, the average maximum temperature of brush wires rises to 39.96 ℃. The maximum temperature increases with the increase of the brush thickness and decreases with the increase of the rear baffle protection height. When the brush wire material is cobaltbased superalloy GH605, the best rotor coating material is WC; when the brush wire material is nickelbased superalloy GH4169, the best rotor coating material is ZrO2.These two matching materials may produce lower friction heat under the same working conditions, and the wear resistance is higher than that of other matching materials.





Research on Thermal Characteristics of Auxiliary Bearing in AMBs and Friction Reduction Design

LI Yingchun, NIE Aonan, YANG Mingxuan, ZHU Dingkang, QIU Ming, YANG Gengsheng

2024, 35(04):  646-655.  DOI: 10.3969/j.issn.1004-132X.2024.04.008

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 The rotor of the AMBs and the auxiliary bearing might produce huge impacts， vibrations and friction heat during the rotor falling which was easy to make the auxiliary bearing fail. The thermal characteristics during the vertical rotor drop on auxiliary bearings were studied， and the main factors leading to the auxiliary bearing failure during the rotor falling were analyzed herein. Subsequently， a method of reducing friction was proposed to deposit solid lubricating film(GLC) on the key surfaces of auxiliary bearings by magnetron sputtering technology， and the rotor drop tests of coated and uncoated auxiliary bearings were performed. The results show that the maximum temperature of the auxiliary bearing is as 210.60 ℃ at a drop speed of 20 000 r/min， which appear in the high-speed rubbing stage between the rotor and the inner ring end face of the bearing. The temperature is higher than the tempering temperature of bearing steel of 160 ℃， which will lead to the failure of the bearing burn. The surface appearance of the channel and end face of the self-lubricating auxiliary bearings coated with GLC film is obviously better than that of the uncoated ordinary auxiliary bearing after the drop tests. The hardness decrease of the inner ring end face caused by friction and heating is lighter， the trajectory of the center of mass and axial displacement are more stable， and the temperature rise is lower. The GLC films play a key role in self-lubrication， wear resistance and friction reduction， the service life and service reliability of the auxiliary bearings are improved. It also provides an idea and method to solve the problems of auxiliary bearing failures easily in AMBs. 

Optimal Design of Piezo-based Actuated Systems in Tunable Diode Lasers

ZHANG Meng, ZHANG Songlin, LIU Yuwei, LIU Shicheng, FAN Pengju

2024, 35(04):  656-665.  DOI: 10.3969/j.issn.1004-132X.2024.04.009

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 In view of the ubiquitous problems in tunable diode lasers, such as small tuning range of output optical frequency without mode hopping, low scanning frequency and complex structure, the dynamic characteristics of the internal piezo-based actuated systems of tunable diode lasers were studied. Based on the design goals of improving rotation accuracy and reducing axis offset, a multi-leaf parallel star-shaped flexible mechanism structure was proposed. After that, based on the Lagrange equation and Duhamel integral, the differential equation of motion and the vibration equation of the piezo-based actuated systems were respectively established.Then, the dynamics model of the flexible mechanisms was established and the structural parameters were optimized. Finally, a test platform was built to explore the mechanical response characteristics of the piezo-based actuated systems and the tunable range of tunable diode lasers. The experimental results show that the first-order natural frequency of piezo-based actuated systems is as 2187 Hz. The maximum axis offset of the flexible mechanisms is as 0.947 mm. In the mode-hop-free tuning performance tests of tunable diode lasers, a mode-hop-free tuning range of 103.5 GHz is achieved at a tuning frequency of 20 Hz. 

Effect of Heat Treatment on Temperature and Stress Distribution during Laser Cladding of 316L Steels

LI Yanle, PAN Zhongtao, QI Xiaoxia, CUI Weiqiang, CHEN Jian, LI Fangyi

2024, 35(04):  666-677.  DOI: 10.3969/j.issn.1004-132X.2024.04.010

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In order to study the control effectiveness of different heat treatment processes on the residual stress of laser cladding, a thermo-mechanics coupling model was established by using ANSYS finite element analysis software. The temperature and stress fields during the laser cladding of 316L stainless steel were simulated under the conditions of preheating(22~900 ℃) before cladding, annealing treatment(200~1000 ℃) after cladding and combined heat treatment before and after cladding. The results show that preheating has the greatest influence on the temperature of molten pool. The temperature of the molten pool increases with the increase of the preheating temperature. Annealing treatment has the best effect on improving the residual stress of laser cladding, and the residual stress is reduced by about 50% at 800 ℃. Comparatively, followed by preheating and annealing treatment, the residual stress is reduced by about 35%. In addition, preheating treatment may also effectively adjust the residual stress, with a reduction of 20% at 500 ℃. 

Fusion Research of Trajectory Tracking Energy-saving Control of Unmanned Hybrid Vehicles

LIU Junling, FENG Ganghui, ZHANG Junjiang, YANG Kai

2024, 35(04):  678-690.  DOI: 10.3969/j.issn.1004-132X.2024.04.011

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In order to further improve unmanned hybrid vehicles trajectory tracking accuracy and energy consumption economy, this paper proposed a trajectory tracking energy-saving control fusion strategy. Firstly, the vehicle kinematics model was established, and the trajectory tracking control of the vehicle was carried out by using the model predictive control strategy. Then, with velocity as the interactive variable, a three-stage dynamic programming energy-saving control strategy was proposed. In this way, the optimal economic function was optimized online to reduce the total cost of energy consumption of the vehicles. Finally, the independent pure pursuit trajectory tracking algorithm and the power following energy-saving control were selected for comparison strategies. The results show that the proposed trajectory tracking energy-saving control fusion strategy improves the trajectory tracking effectvieness and reduces the total cost of vehicle energy consumption. The trajectory tracking errors are reduced 70.47%. The total cost of energy consumption decreases 4.52% and 25.10% in pure electric drive mode and hybrid drive mode, respectively.

Integrated Casting Triangular Beam Lightweight Improving with Multi-performance Constraints of Body Systems

SU Yonglei, ZHANG Zhifei

2024, 35(04):  691-699.  DOI: 10.3969/j.issn.1004-132X.2024.04.012

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 An optimization method of integrated casting structures was constructed systematically, and based on the super-element model of body system, body casting part lightweight improving with multi-performance constraints was realized. Firstly, complex body systems were reduced, the sub-system division principle and method were proposed for continuous body structure. Super-element reduction of the sub-system was conducted to ensure analysis accuracy and improve calculation efficiency, laying the foundation for rapid optimization. Secondly, performances of casting structures and body systems were considered simultaneously, the compromise programming methods were used to normalize static and dynamic sub-targets and construct the comprehensive objective function, weight coefficients of sub-targets were obtained by analytic hierarchy process(AHP), and then multi-model topology optimization was carried out to determine position distribution of reinforcements. Furthermore, designability and manufacturability were considered simultaneously, parametric definition of variable thickness drawing surface of casting structure was carried out, manufacturing constraints were applied during optimization processes, and then thickness parameter design was completed based on combined surrogate model. The results show that, under the premise of ensuring the analysis accuracy, reduced body system models improve computing efficiency greatly, and save 97.3% of computing resources. Casting triangular beam lightweight may be achieved while improving related performance by conducting structure optimization, which indicates correctness and practicability of the proposed method. 

Study on Damage Mechanism of Water Jet Guided Laser Cutting of CFRP

CHEN Zhongan, BAO Binying, ZHANG Guangyi, CHAO Yang, , WANG Yufeng, YAO Zhehe, JIAO Junke, ZHANG Wenwu,

2024, 35(04):  700-710.  DOI: 10.3969/j.issn.1004-132X.2024.04.013

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After water jet guided laser machining, CFRP exhibited thermal damages on the cut groove surfaces and cross-sections, which was an important factor affecting the materials mechanics properties and reducing the service performance. To address these issues, the influences of machining parameters on the geometric and surface morphology of grooves were analyzed, and the formation mechanism of surface and cross-sectional thermal damages was investigated herein. The results indicate that high laser power, low pulse frequency, and low cutting speed may effectively increase the depth of the grooves. The interaction between the laser and the material, as well as the flushing action of the water jet, are the main reasons for the formation of thermal damages on the groove surface. In the cutting experiment of 2 mm thick CFRP, it is found that the width of the heat affected zones in the cross-sections is related to the arrangement of the fibers. The heat affected zone width is the largest for 0° carbon fibers, followed by 45° and 135° carbon fibers, which have similar widths, and the width is the smallest for 90° carbon fibers. In addition, increasing the water jet velocity is beneficial for suppressing the expansion of the thermal affected zones. When the water jet velocity is increased from 80 m/s to 120 m/s, the maximum width of the thermal affected zones decreases by 35.7%.

Modeling and Prediction of Central Damages in Cross Wedge Rolling Based on Continuous Damage Mechanics

PENG Wenfei, ZHANG Cheng, LIN Longfei, HUANG Minghui, YU Feng

2024, 35(04):  711-720,751.  DOI: 10.3969/j.issn.1004-132X.2024.04.014

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Due to the cumulative central damage behavior in cross wedge rolling, it was prone to form central porosity defects, thus it was of great significance for high-performance manufacturing of cross wedge rolling shaft parts to accurately predict the formation conditions of central damages. The hot tensile tests were conducted under different conditions to obtain the main factors that affected material damages. Subsequently, the coupled damage constitutive models considering temperature, strain rate and stress triaxiality were proposed based on continuous damage mechanics. Furthermore, experiments on cross wedge rolling with different area reduction were conducted to calibrate the material fracture threshold of the damage constitutive model and verify the prediction accuracy of the damage model. The models were used to predict the influence laws of area reduction, spreading angle, and forming angle on central damage, which provided references for parameter selection. The results show that temperature, strain rate and stress triaxiality all significantly affect material damage behavior, and the established coupled damage constitutive models may effectively predict the evolution processes of central damages in cross wedge rolling. The central damages of cross wedge rolling are inversely proportional to the forming angle, and is directly proportional to the spreading angle and area reduction. The degree of influence of each parameters, from small to large, is in order of area reduction, spreading angle, and forming angle.

Influence of Rivet Coating on Formation and Mechanics Performances of SSFR Joints

HAN Xiaohui, LIN Sen, FANG Xifeng, WANG Zhenzhong, SUN Zhaogang, YU Feilong, LI Lei, MA Yunwu, LI Yongbing,

2024, 35(04):  721-730.  DOI: 10.3969/j.issn.1004-132X.2024.04.015

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Rivet coating was a key factor influencing the formation and mechanics performances of riveted joints. The SSFR processes were used to join 6005A-T6 and 6A01-T5 aluminum alloy sheets herein. Three types of rivets including non-coated, Zn coated, and ZnNi coated were utilized to study the evolution laws of riveting force, energy input, and formation of the SSFR joints. Moreover, the remaining thickness of the coating layers at different positions in the joints and the diffusion of coating elements at the rivet/sheet interfaces was analyzed, and the influences of the rivet coating on the tensile-shear and cross-tension performances of the joints were investigated. The results indicate that the coating reduces the energy input generated by rivet rotation, thereby reducing the heat-affected zones of aluminum alloy materials. However, the decrease in energy input is not conducive to the formation of solid phase bonding between aluminum alloy materials in the rivet cavity, resulting in a decrease in the tensile-shear and cross-tension performances of the joints. Compared with Zn coating, the ZnNi coating has stronger wear resistance, and the remaining thickness still exceeds 40% after the stirring friction caused by high-speed rotation of rivets, which helps to improve the corrosion resistance of joints.

Longitudinal and Lateral Coordination Control of Cars with Aerodynamic Interference of Wind-vehicle-bridge System

YUAN Zhiqun, LI Yuehan, LIN Li, SUN Pengfei, ZHANG Yi,

2024, 35(04):  731-741.  DOI: 10.3969/j.issn.1004-132X.2024.04.016

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To enhance the driving safety caused by cross-wind, the transient analysis model of a car overtaking truck on cross-sea bridge was established using a coupling method of composite wind and moving mesh, and the mechanism of aerodynamic interaction between “wind-vehicle-bridge” in the overtaking processes of a car and the influences on the aerodynamic characteristics of the car were revealed. The overtaking trajectory planning models were developed using a fifth degree polynomial interpolation algorithm, and the longitudinal and lateral coordination motion controllers were developed, using dual fuzzy PID control method for the longitudinal controllers and sliding mode control method of radial basis function network for the lateral controllers. The path tracking capability analysis and driving stability evaluation of the overtaking processes of a car under cross-wind were carried out. The results show that the aerodynamic interference is significantly related to the travelling lanes and positions. The longitudinal and lateral coordination motion controllers have better accuracy and robustness in controlling the path tracking, and the cross-wind stability is significantly improved.

Dynamic Performance Analysis of High-speed Double Deck EMUs with Inter-car Rolling Damping Devices

WANG Xin, DAI Liangcheng, YANG Dongxiao, LUO Yun, CHI Maoru, GUO Zhaotuan, ZENG Pengcheng

2024, 35(04):  742-751.  DOI: 10.3969/j.issn.1004-132X.2024.04.017

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Double deck EMUs were equipped with amplifiers for secondary lateral damping to mitigate the vibrations caused by primary hunting behaviour. However, increased secondary lateral damping could negatively impact the lateral ride quality of the vehicles. In order to solve the problem of poor lateral ride quality in high-speed double deck EMUs, a mathematical model of the inter-car rolling damping devices was created by taking into account the working principle of the damper as well as the rolling and yaw state of the carbody, and the simulation models of the damper established in AMEsim software were verified with the bench tests. Finally, the key parameters of the inter-car rolling damping devices were optimized by establishing a co-simulation model between the inter-car rolling damping device and the vehicle model, without changing the existing suspension parameters of the vehicles. The simulation results show that the device may effectively improve the lateral ride quality of the double deck EMUs without affecting the vertical ride quality of the vehicles and ensure the safety of curve operations.

Shear Failure Mechanism Analysis and Optimum Design of 850 Ton Cold Shear Based on Orthogonal Test

QI Maofu, SUN Yuantao, TIAN Chunlei, FENG Jiaqi

2024, 35(04):  752-759.  DOI: 10.3969/j.issn.1004-132X.2024.04.018

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In order to reduce the shear force of 850 ton cold shears, the shearing mechanism and characteristics of the cold shear were studied, the effects of shear parameters such as shear clearance, blade inclination, shear velocity, blade width and blade overlap on shear force were analyzed by orthogonal test. Variance, range and significance were used as the indexes of influencing factors, and the priority of them were given to optimize the shear parameters and reduce the shear force. The experimental verification of the cold shear before and after the optimization of shear parameters were carried out in the workshops which show that the errors between the measured and simulated values of the shear force of the cold shear before and after optimization were within 5%, which verifies the reliability of the simulation analysis. By setting the optimal shear parameters and shearing the same steel bar, the maximum shear force of the upper shear blade is reduced by 5.84 kN, about 13%. The maximum shear force of the lower shear blade is reduced by 4.77 kN, about 9.7%. Feedbacks from workshops show that the optimization greatly prolongs the period of blade broken and blunt and improves the blade life and shearing efficiency. The results are of great significance for improving the economy and production efficiency of the equipment, and may be applied to the engineering design of the same type of cold shears.