Table of Content

25 November 2023, Volume 34 Issue 22

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Study on Influencing Factors of Stress at Roots of Autonomous Sailboat Wing Sail Mast and Its Influencing Laws

NIU Wenchao, SUN Zhaoyang, SHENG Zhongqi, YU Jiancheng, ZHAO Baode, ZHAO Wentao,

2023, 34(22):  2647-2658.  DOI: 10.3969/j.issn.1004-132X.2023.22.001

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In order to study the influencing factors and influencing laws of the wing sail mast root stress, a numerical calculation model of the root stress of the wing sail masts was proposed based on the equivalence principle, and the accuracy of the proposed model was verified by finite element calculation. Based on the numerical calculation model of mast root stress, it was derived that there were 4 external parameters and 3 body parameters which affect the mast root stresses, the external parameters contain autonomous sailboat rolling period , rolling amplitude, rolling angle and deflection angle of wing sails. The body parameters contain mast center of gravity height, wing sail mass and the eccentric distance of wing sail. Based on the numerical calculation model, the influences of the above factors on the root stress of the masts were analyzed, and it is found that the stress values have a decreasing negative quadratic power function relationship with the rolling period , which is proportional to the rolling amplitude, the wing sail center of gravity height, the eccentric distance and wing sail mass, and the change curve of stress values with deflection angle coincides with the sinusoidal curve, and the stress value curve shows a sinusoidal waveform in one roll cycle. Finally, a method of adding stiffeners to optimize the structure was proposed for the stress concentration in the roots of the mast, and it was verified by the finite element calculation and the experimental analysis of turntable shaking. It is found that this method may reduce the stress value of the roots effectively during the working processes of the wing masts.

A Non-uniform Damage Accumulation Model Considering Load Interactions

WU Zhifeng, GAO Jianxiong, XU Rongxia, ZHU Pengnian

2023, 34(22):  2659-2664，2673.  DOI: 10.3969/j.issn.1004-132X.2023.22.002

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 In order to study the evolution law of fatigue damage of metal components， a non-uniform damage accumulation model and life prediction theory were established considering the interaction of loads. First， a non-uniform fatigue damage model was proposed based on residual life under constant amplitude loading. Secondly， the loading sequence effect was expounded， and it was proved that the proposed load loading sequence effect might be considered in the non-uniform damage model. Then， the interaction among loads was verified， and it was proposed that there was mutual influence between adjacent two-level loads， the load interaction factor was defined and introduced， and a new equivalent damage model was established. Finally， combining the non-uniform damage model with the new equivalent damage model， a non-uniform damage model was constructed under multi-level variable amplitude loads. Life prediction was carried out with the test data of 30NiCrMoV12 steel and Al-2024-T45 alloy under two-level loading. By comparing with various models， it was verified that the proposed model may predict fatigue life well. The proposed model has a certain reference value for the damage evolution law of metals. 

Research on Dynamic Modeling and Solving Method of Integrated Transmission System under Time-varying Conditions

ZHANG Dingge, WANG Liyong, LI Le, ZHANG Jinle

2023, 34(22):  2665-2673.  DOI: 10.3969/j.issn.1004-132X.2023.22.003

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In order to meet the demands of real time monitoring of load characteristics and the demands of health management of the special vehicle integrated transmission system under actual complex conditions， by using the matrix analysis method and numerical solution method of planetary transmission mechanisms， and taking the real vehicle sensor data as the model input， a dynamic model of integrated transmission system was established to rapidly and continuously solve the transmission output speed and torque under time-varying conditions. The kinematic matrix， differential equation and torque balance equation of the planetary transmission mechanisms were constructed. The fast continuous solution method of the dynamic model under time-varying conditions and the method for solving road load under the conditions of missing road load information were proposed. The calculated transmission output speed and torque were compared with the bench test results under the three typical conditions of launching， shifting and acceleration. The results show that the dynamic model may realize the dynamic simulation calculation of the output characteristic of the integrated transmission under the conditions of missing road load information. It provides support for real-time monitoring， dynamic control and intelligent operation and maintenance of special vehicle integrated transmission systems. 

Identification of Blade Leading and Trailing Edges and Study on Polishing Processes by Flag Wheel

JU Chun, LIU Jia, YANG Shengqiang, ZHANG Jingjing, ZHAO Xuhui,

2023, 34(22):  2674-2683，2692.  DOI: 10.3969/j.issn.1004-132X.2023.22.004

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Aiming at the structural difficulties of the thin thickness of the leading and trailing edges of the blades and the sharp change of the curvature, the least square method was used to fit the ellipse of the discrete points of the blade section including the leading and trailing edges and part of the blade body. By setting the three error constraints of the average distance, maximum distance and subtraction of slope, the boundary of the leading and trailing edges was identified. The elastic tool flag wheel suitable for the leading and trailing edge polishing was selected, and the polishing model of the flag wheel was simplified. Starting from the polishing of a single abrasive particle, the relationship between the compression of the flag wheel and the polishing force during the polishing processes was explored. Based on the Hertz contact theory and the improved equal chord height error method, the step spacing was determined. Finally, the blade was clamped by the robot, and the comparison experiments of lateral polishing and longitudinal polishing were carried out by means of flag wheel polishing. Both polishing methods may ensure that the values of surface roughness are less than 0.4 μm and the profile errors are less than 0.08 mm, which may meet the dimensional accuracy and surface quality requirements of the blades.

Study on EDM of PCD by Mixing Iron Powders

JIA Zhixin, ZHANG Kaiyue, WANG Jin

2023, 34(22):  2684-2692.  DOI: 10.3969/j.issn.1004-132X.2023.22.005

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In order to improve the efficiency of EDM PCD, the spark discharge was promoted by mixing iron powders into kerosene working fluid. The mechanism of PCD in EDM of mixed iron powders was analyzed. The effects of iron powder concentration, peak current, pulse width, pulse and servo voltage on workpiece MRR and machining surface roughness were studied by experiments, and the reasons were analyzed. The experimental results show that kerosene mixed with a certain concentration of iron powders may improve the MRR of EDM PCD. The MRR increases with the increase of peak current, increases first and then decreases with the increase of pulse width, increases first and then decreases with the increase of pulse, and decreases with the increase of servo voltage. The surface roughness of EDM PCD is less affected by the concentration of iron powder, peak current, pulse width, pulse interpulse and servo voltage. The optimal combination of electrical parameters is obtained by orthogonal test: peak current 20 A, pulse width 125 μs, pulse interpulse 75 μs and servo voltage 27.5V.

Research on Drag Torque Characteristics of Wet Clutchs under High Linear Speed Conditions

LI Jie, MA Chao, WANG Xiaoyan

2023, 34(22):  2693-2703，2710.  DOI: 10.3969/j.issn.1004-132X.2023.22.006

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In order to study the mechanism and the change law of the belt discharge torque of the friction plates under the no-load condition of the wet clutchs at high linear speed, a belt was established based on the hydrodynamics model considering the influences of the surface tension of the lubricating oil film and the oil-gas two-phase flow at high linear speed. The mathematical model of the drag torque was used to establish the volume fraction of air and oil two phases flow simulation for the oil film with an exhaust gap to analyze and verify the change of the oil film. The analysis of the model shows that the oil-gas two-phase flow of the friction plate produces part of drag torque at high linear speed, which is the main reason for the recovery of drag torque. Drag torque tests was did in high-speed belt-row test system for friction components. The influences of direction, lubricating oil temperature, flow rate, belt-row gap, and friction plate size on drag torque were analyzed.

Design and Performance Research of Asymmetric Scroll Profiles with Equal Wall Thickness Using Base Circle Involute

HOU Caisheng, LI Jinhu, LIU YuMA Hui

2023, 34(22):  2704-2710.  DOI: 10.3969/j.issn.1004-132X.2023.22.007

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 In view of the problems of low compression ratio and small displacement volume of equal wall thickness profiles， the gas force of the variable wall thickness profile changed greatly and it was difficult to machine and measure， a design method of asymmetric equal wall thickness profiles was proposed using base circle involute. Using this method， the fully engaged asymmetric scroll teeth with equal wall thickness were established， and the calculation formula of the working chamber volume was derived. The dynamic change processes of the axial， tangential and radial gas forces exerted on the orbiting scroll tooth were obtained with the spindle angles. The results show that compared with the traditional scroll profiles with equal wall thickness and variable wall thickness profile， the displacement volume of the newly constructed asymmetrical scroll profiles with equal wall thickness is increased by 25.99% and 7.82% respectively， and the compression ratio is increased by 19.70% and 2.04% respectively. While the variation range of the axial， tangential and radial gas forces is significantly reduced. It also shows that the asymmetric scroll profiles with equal wall thickness may give better consideration to the advantages of the traditional profiles， and has more superiorities in volume performance and dynamic performance. 

Modeling and Experimental Research of Ground Workpiece Surface Topography after Grinding with Structured Grinding Wheels

YI Jun, YI Tao, CHEN Bing, DENG Hui, ZHOU Wei,

2023, 34(22):  2711-2720.  DOI: 10.3969/j.issn.1004-132X.2023.22.008

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 The rough surface modeling method was employed to establish the surface topography model of a straight groove structured grinding wheel, considering the influences of structural characteristic parameters on the continuity of the grinding wheel surface through actual measurements. Based on the kinematics relationship between the grinding wheel and workpiece, as well as the trajectory equation of cutting edge, a prediction model for workpiece surface topography after grinding was formulated. Grinding experiments were conducted using both electroplating CBN and brazing CBN straight groove structured grinding wheels. The results show that relative errors between predicted Ra values and experimental ones are below 10%, while relative errors between predicted Rz values and experimental ones are below 12%, thereby validating the accuracy of the prediction model. Furthermore, the influences of various structural parameters on the surface topography of the workpiece were investigated. When the groove width of the grinding wheel remaines constant, an increase in the intermittent ratio of the grinding wheel resultes in an elevation of workpiece surface roughness. Conversely, when the intermittent ratio is held constant, variations in groove width have a minimal effect on workpiece surface roughness. Additionally, it is observed that roughness of the grinding wheel itself is a significant factor determining ground workpiece surface roughness. Among the three characteristic parameters of the grinding wheel surface topography investigated herein, it is observed that the skewness of the grinding wheel surface height exerts the most significant influence on the ground workpiece surface roughness.

Covariance Process Monitoring Scheme for Multi-mode Multivariate Unknown Distributions

ZHAO Yu, LI Yanting, WU Zhenyu, ZHOU Di, HU Jie

2023, 34(22):  2721-2736，2757.  DOI: 10.3969/j.issn.1004-132X.2023.22.009

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Aiming at the challenges of multi-mode, high dimension and nonnormality of industrial process data, a multi-mode online monitoring method was designed herein based on covariance tests considering time constraints. Firstly, the covariance matrix of the data to be detected was estimated using a cross-validated linear shrinkage estimation method. Secondly, the sparse principal eigenvalue test statistic was calculated based on the estimated covariance matrix. Subsequently, an EWMA（exponentially weighted moving-average） control chart with sliding window was designed based on the sparse principal eigenvalue test statistic: the MSPEWMA control chart, and the final test statistic was obtained by combining the mode transition constraints. Through Monte Carlo simulation, the performance of the MSPEWMA control chart under different conditions(variable dimension, drift size, control sample size, transition constraint parameters, and observation data distribution) was investigated. The results show that the newly proposed control chart has better monitoring results under large drift and non-normal conditions compared with other control charts based on covariance tests. Finally, the effectiveness of the method was demonstrated using real SCADA data of wind turbines.

Classification Test of Tire Tread Wear of Passenger Cars Based on In-wheel Acceleration

TAO Liang, TANG Yu, QI Wenjie, ZHANG Dashan, LU Rui, ZHANG Xiaolong

2023, 34(22):  2737-2745.  DOI: 10.3969/j.issn.1004-132X.2023.22.010

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In light of the issue that the tread depth of passenger car tires was shallow and the conventional identification of wear characteristics were not obvious based on acceleration time-domain signals. This paper aimed to explore the classification and estimation of tire wear through the analysis of frequency-domain features of internal tire acceleration. Firstly, an intelligent tire test system was built by self-developed special rim assembly and data collector, and a three-axis accelerometer was arranged in the tire inner liner. The acceleration values were obtained by wired method, and the sampling frequency was 50 kHz. Secondly, based on the built test system, the typical tire pure rolling test was carried out on the Flat Trac bench, and the data was analyzed to clarify the parameters of the classification algorithm and construct the data set. The test tires included new tire, semi-grinding tire and full-grinding tire. The data analyses show that the circumferential acceleration Ax and radial acceleration Az of tires with different wear degrees are significantly different in the frequency domain of 5 kHz. Therefore, the vibration amplitude of Ax and Az in the frequency domain of 5 kHz was extracted at an interval of 10 Hz as the feature point, and the frequency domain data sets FDAx and FDAz were established respectively with vertical load, speed and tire pressure. Finally, the random forest algorithm was used to train and predict the two data sets respectively. When the number of decision trees and the minimum number of leaves are 20 and 20 respectively, the model classification effectivenes is the best. The results show that the average classification accuracy of the frequency domain data set FDAz is 95.1543%, which is higher than that of the data set FDAx. Compared with the time domain data sets TDAx and TDAz constructed by extracting Ax and Az time domain features from the same experimental data, the classification accuracy is increased by 16.18% and 10.08% respectively. At the same time, the feature values of the FDAz data set are optimized to obtain the optimal model classification accuracy and real-time performance when the feature frequency band and the number of feature points are within 1000 Hz and 100, respectively. The research shows that it is feasible to identify the degree of tire wear based on the frequency domain signals of the acceleration in the tire, which provides an effective means for the identification of the degree of tire wear of passenger cars.

Optimization of Variable Gauge Train Wheel Treads Based on Reverse Design Method

ZHANG Xiao, CHI Maoru, XIE Yuchen, WANG Huansheng, CAI Wubin, DAI Liangcheng

2023, 34(22):  2746-2757.  DOI: 10.3969/j.issn.1004-132X.2023.22.011

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According to the research of the dynamics of Chinese-Russian variable-gauge trains, it was found that a single wheel tread might not be suitable for multiple types of rails, resulting in issues such as low conicity shaking, low critical speed, and poor wear performance. Based on the wheel-rail contact relationship, vehicle dynamics theory, and a reverse design recursive algorithm for wheel treads, a method for designing balanced and adaptable wheel treads for multiple types of steel rails was proposed. Based on this approach, the LMAopt wheel tread was obtained by optimizing the LMA treads. When the LMAopt treads were matched with Russian P65 steel rail, the low conicity shaking phenomenon is effectively suppressed, lateral ride index is improved, and the critical speed of the vehicle is increased by 22%. When matched with Chinese CHN60 steel rail, the dynamics performance is comparable to the LMA tead. The wear performance of the LMAopt profile under the influences of both types of steel rails is also improved, ensuring better dynamics performance throughout the service life of the vehicles. In conclusion, the LMAopt tread is a more suitable optimized wheel tread for variable-gauge trains.

Simulation and Experimental Study on Slip Bearing Performance and Pipe Wall Damage Characteristics of Pipeline Plugging Robots

TANG Yang, ZHANG Wudi, ZHANG Yulin, WANG Yuan,

2023, 34(22):  2758-2771.  DOI: 10.3969/j.issn.1004-132X.2023.22.012

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The problems such as setting failure and tube wall damage were easy to occur in the deceleration and setting processes of pipeline plugging robot slips. Aiming at the ploughing effectiveness and hard contact phenomenon of slip in the deceleration and setting processes, the force of the slip deceleration and setting and the damage factors of pipe wall were analyzed. The finite element simulation model of slip deceleration and setting processes was established, and the influences of structural parameters such as slip tooth apex angle, tooth inclination angle and tooth number on the bearing performance and tube wall damage characteristics were analyzed. Four kinds of slips with the optimal combination of the key structural parameters of tooth apex angle, tooth dip angle and tooth number were obtained by using the method of multi-factor orthogonal experimental analysis. The simulation experiments of slip deceleration and setting processes were designed and built. Four kinds of slips with optimal combined structural parameters were processed, and the experimental test of friction between slip and tube wall during slip deceleration and setting was completed. Through the comparative analysis of the results of the pressure bearing performance and the damage degree of tube wall obtained by simulation and experiments, the optimal structural parameter combination of slip is optimized as tooth apex angle θ=65°, tooth dip angle γ=60°, and tooth number m=18.