Table of Content

25 December 2023, Volume 34 Issue 24

Previous Issue   

Analysis of Causes for Rail Corrugation on Steel Spring Floating Slab Tracks of Metro Small Radius Curves

WANG Zhiqiang, LEI Zhenyu

2023, 34(24):  2899-2908.  DOI: 10.3969/j.issn.1004-132X.2023.24.001

Asbtract ( )   PDF (10660KB) ( )  

References | Related Articles | Metrics

 In order to explore the causes of corrugation on the steel spring floating slab track with the small radius curves of metro, the formation processes of rail corrugation were explained from the perspective of wheel-rail stick-slip vibrations. Firstly, according to the basic situation of the line, a three-dimensional finite element model of wheelset-floating slab track was established. Then, the wheel-rail contact stick-slip features and rail longitudinal wear characteristics were analyzed using the above model to quantify the occurrence trend of corrugation. Finally, the relationship between the natural vibration properties of wheel-rail system and the formation of corrugation was studied based on the complex modal theory. The results show that the stick-slip distribution of the inside wheel-rail interface changes periodically during the operation of the wheelset, indicating that the inside wheel-rail system has experienced periodic stick-slip vibrations, which may lead to periodic wavy wear on the inner rails, and finally form rail corrugation; the stick-slip distribution of the outside wheel-rail interface has not changed significantly in general, which indicates that there is no stick-slip vibrations in the outside wheel-rail systems, so it is not easy to form rail corrugation. In the longitudinal direction of the rail, the slip of the inner rail is significantly greater than that of the outer rail, illustrating that the longitudinal wear of the inner rail is greater; in the transverse direction of the rail, there is little difference between the slip of inner and outer rails, illustrating that the transverse wear of inner and outer rails is similar. The distribution of longitudinal and transverse slip nephograms of inner and outer rails shows a certain degree of periodicity, especially the longitudinal slip nephogram of the inner rail, with a wavelength of 28 mm close to the measured corrugation wavelength of 25 mm, which is consistent with the periodic characteristics of the contact stick-slip state of the inside wheel-rail interface, and further shows that the inner rail is more prone to serious periodic wear, namely rail corrugation. Combining the analysis results of wheel-rail contact stick-slip and wear features and wheel-rail system vibration characteristics, it may be concluded that the inner rail corrugation on the floating slab track with the small radius curves of metro is caused by the stick-slip vibrations induced by the unstable vibration modes of wheel-rail system corresponding to 664.1 Hz and 665.8 Hz, and the unstable modes are all presented as the bending vibrations of the inner wheel relative to the track. The sensitivity analysis of parameters indicates that properly increasing the vertical stiffnesses of the fastener and the steel spring may play a positive role in the control of corrugation.

Comprehensive Performance Optimization of High Pressure Threaded Plug-in Relief Valves

CHEN Junxiang, KONG Xiangdong, XU Kelong, AI Chao,

2023, 34(24):  2909-2919,2926.  DOI: 10.3969/j.issn.1004-132X.2023.24.002

Asbtract ( )   PDF (4914KB) ( )  

References | Related Articles | Metrics

In views of the coupling of structural parameters affecting different performance of high-pressure threaded plug-in relief valves, it was difficult to optimize the comprehensive performance, a multi-objective particle swarm optimization algorithm was proposed to optimize the comprehensive performance. Based on the structural characteristics of high-pressure threaded plug-in relief valves, the mathematical models of opening and closing characteristics, pressure regulation deviation and stability were established. Based on the first-order sensitivity analysis of the influences of structural parameters on the dynamic response, according to the mapping relationship between structure and performance, with the opening rate, pressure regulation deviation, stability and dynamic response performance improvement as the optimization objectives and coupling structure parameters as variables, a comprehensive performance optimization model was established, and the optimal solution of coupling structural parameters was obtained in the form of Pareto set by particle swarm optimization algorithm. The experimental results show that after optimization, the pressure oscillation of the high pressure threaded plug-in relief valves is reduced by 22.7%, the opening rate is increased by 1.5%, the pressure flow gradient is reduced by 14.58%, the pressure overreach in front of the valves is reduced by 14.1%, the response time is shortened by 9.52%.

Effects of Tool Wear on Milling Surface Integrity and Fatigue Properties of Allvac 718Plus Superalloy

GOU Ruijie, ZHANG Xiaofeng, ZHANG Hongbin, YAO Jun, LI Xun

2023, 34(24):  2920-2926.  DOI: 10.3969/j.issn.1004-132X.2023.24.003

Asbtract ( )   PDF (4539KB) ( )  

References | Related Articles | Metrics

Based on the premise of Allvac 718Plus superalloy milling tool wear law, the influence rules of tool wear on the indicators of fine milled surface integrity were studied，and combined with specific fatigue performance tests of specimens, the influence rules and mechanism of tool wear on the fatigue performance of specimens were analyzed. It is obtained that the control range of flank face tool wear under the parameters of Allvac 718Plus fine milling is less than 0.15 mm, and the main influencing factors on fatigue performance of the specimens are also obtained. The relevant research results provide a reference for controlling the surface integrity and tool wear of Allvac 718Plus specimens in fine machining.

An Evaluation Method for Tooth Surface Load Capacity of Polymer Gears Based on Nominal Gear Equivalent Load

HU Xinlei, LIU Huaiju, WEI Peitang, LU Zehua, LIAO Changjun, ZHU Jiazhan

2023, 34(24):  2927-2935.  DOI: 10.3969/j.issn.1004-132X.2023.24.004

Asbtract ( )   PDF (6709KB) ( )  

References | Related Articles | Metrics

The current evaluation methods for the tooth surface load capacity of polymer gears still rely on the methods for metal gears, which did not comprehensively consider the influences of material type, lubrication condition and stress of the polymer gears. This would lead to significant reliance on engineering experience for material selection, strength design and loading capacity evaluation in practical engineering applications. Therefore, a polymer gear tooth surface load capacity evaluation method was proposed based on the nominal gear equivalent load. Over 169 sets of data and more than 6000 hours of durability tests on polymer gears were obtained, considering different lubrication conditions, gear materials, and machining methods. The results show that oil lubrication may significantly improve the tooth surface load capacity of plastic gears, and the tooth surface load capacity of PEEK(polyether ether ketone) gears is more than 30% higher than that of POM(polyoxymethylene) and PA66(polyamide) gears under oil lubrication, which provides an evaluation method and basic data support for active design and transmission power applications of polymer gears.

Mechanism Analysis and Experimental Study of EDM in Boric Acid Solution

ZHENG Qian, ZHANG Yaou, GAO Qiang, LU Juncheng, YANG Xiangjun, ZHAO Wansheng,

2023, 34(24):  2936-2945.  DOI: 10.3969/j.issn.1004-132X.2023.24.005

Asbtract ( )   PDF (16363KB) ( )  

References | Related Articles | Metrics

In-reactor maintenance of nuclear power plant components was typically performed by immersion in boric acid solution. In order to verify the feasibility of the EDM in boric acid solution, 2200 mg/L boric acid solution was used as the discharge medium for processing experiments. DOE were adopted to explore the effects of processing parameters on material removal rate, inlet diameter of hole, surface quality and electrode loss in boric acid environment, the small hole forming was realized under optimal electrical parameters, and the size accuracy of small holes and the distribution law of recast layer were analyzed. The results show that the discharge process of boric acid solution as the working medium is intense and produces a lot of bubbles. The bubble-assisted discharge and the mechanism of promoting chip removal may improve the material removal rate of EDM in boric acid solution. Under the optimal parameters of peak current I=24 A, pulse width Ton=20 μs and interpulse Toff=20 μs, the thickness of recast layer on the pore surface is small and there is no crack. Boric acid solution is suitable as the working medium of EDM. The research results may provide theoretical support for EDM of in-reactor parts maintenance in nuclear power plants.

A Bionic Bouncing Robot Design and Made Inspired by Locusts

WANG Kaidi, CHEN Suifan, TANG Wei, QIN Kecheng, LI Qipeng, YANG Zhan, LIU Yang, ZOU Jun

2023, 34(24):  2946-2951.  DOI: 10.3969/j.issn.1004-132X.2023.24.006

Asbtract ( )   PDF (3896KB) ( )  

References | Related Articles | Metrics

 In order to improve the mobility of small robots and increase the diversity of movement gait, a jumping robot imitating locust bouncing was designed based on the body structure and movement mechanism of locusts, and the main body was made by 3D printing. And for reproducing the locusts bouncing mechanism, a torsion spring was installed at the joints of the robot body to simulate the locusts SLP(semilunar energy storage) mechanism. When the robot met an obstacle, the torsion spring released the stored elastic potential energy and generated a ground reaction force, which realized the robots bouncing and thus crossed the obstacle. The robot might imitate the locusts jumping actions, and simulate the locusts flexibility to a certain extent. It was experimentally verified that the robot has good jumping performance, with a jumping distance of up to 100 cm and a jumping height of up to 120 cm which is about 15 times of the own length.

Static Stiffness Analysis of Double-nut Ball Screws Considering Dimensional Errors and Radial Loads

CHEN Guangyu, WENG Zhiwei, ZHANG Song,

2023, 34(24):  2952-2962.  DOI: 10.3969/j.issn.1004-132X.2023.24.007

Asbtract ( )   PDF (11432KB) ( )  

References | Related Articles | Metrics

A calculation model of the axial static stiffness for a preloaded double-nut ball screw was improved by considering both the dimensional errors and radial loads. Firstly， based on Hertz theory， the ball load distribution and axial static stiffness model were improved considering the dimensional errors in the manufacturing processes and the radial loads caused by factors such as improper assembly. Secondly， the Newton-Raphson iterative method was used to calculate the axial static stiffnesses of the double-nut ball screws， and the loading deformation tests were carried out on the self-developed test bench to verify the correctness of the model. Finally， the influences of axial loads， radial loads and ball dimensional errors on the axial static stiffnesses of double-nut ball screws were studied by simulation analysis. The results show that the static stiffness model established has a good effect on describing the axial deformation displacements and axial static stiffnesses， which has a good reference significance for guiding the bearing capacity evaluation and precision design of the preloaded double-nut ball screw under static or low-speed conditions. 

A Method for Identifying and Predicting Energy Consumption of Machine Tools by Combining Integrated Models and Deep Learning

XIE Yang, DAI Yiqun, ZHANG Chaoyong, LIU Jinfeng

2023, 34(24):  2963-2974.  DOI: 10.3969/j.issn.1004-132X.2023.24.008

Asbtract ( )   PDF (9506KB) ( )  

References | Related Articles | Metrics

In response to the problems of multi-source influences, high quality feature extraction and selection, complexity and nonlinearity in identification methods for energy consumption processes, a method for identifying and predicting energy consumption of machine tools was proposed by combining integrated models and deep learning. Taking CNC milling as an example, an energy consumption model was established based on different cutting periods, and signals were preprocessed by wavelet transform. The preprocessed signals were used to train and predict the energy consumption of the model combining RF and LSTM neural network(RF-LSTM model). Meanwhile, the RF was used to identify the cutting stages and realize the energy consumption classification prediction. The effectiveness and superiority of the proposed method were demonstrated through practical cases, and the RF-LSTM model was used to compare with the other four schemes, which verify that this recognition method may accurately predict different operating states and energy consumption of the machine tools.

Experimental Study of High-speed Turning of Hardened Bearing Steels under High-pressure Cryogenic CO2 Jet Cooling Conditions

LI Xiaorui, ZHAO Wei, LI Hao, SHI Weiqi, HE Ning

2023, 34(24):  2975-2985.  DOI: 10.3969/j.issn.1004-132X.2023.24.009

Asbtract ( )   PDF (16046KB) ( )  

References | Related Articles | Metrics

In the high-speed hard turning processes for hardened bearing steels, there were some problems such as rapid tool wear, serious chip entanglement and poor machined surface quality. The high-speed hard turning tests of GCr15 bearing ring were carried out with PCBN tools using high-pressure cryogenic CO2 jet as cooling medium, and compared with high-pressure emulsion and high-speed dry cutting, and the effects of cooling conditions and cutting parameters on cutting performances and machined surface quality were analyzed. The results show that within a certain range of the cutting parameters, the use of high-pressure cryogenic CO2 jet assisted cutting may effectively reduce tool wears and improve chip breakings, but it is also more likely to chipping when the tools are in the stage of severe wear. When the cutting speed is high, the high pressure cryogenic CO2 jet may improve the surface quality of the workpieces more significantly, effectively reduce the surface roughness of the workpieces, increase the residual compressive stresses and surface microhardnesses.

Multi-point 3D Hot Stretch-Bending Process of Titanium Alloy Profiles and Their Microstructure Evolution

GAO Song, SUN Yingli, LI Qihan, YING Liang, HAO Zhaopeng, ZHANG Bangcheng

2023, 34(24):  2986-2995,3014.  DOI: 10.3969/j.issn.1004-132X.2023.24.010

Asbtract ( )   PDF (20050KB) ( )  

References | Related Articles | Metrics

In order to solve the problems of 3D bending and forming of difficult-to-machine material profiles such as titanium alloy, a multi-point 3D hot stretch-bending process was proposed and the forming equipment was developed. The effects of the processing parameters such as pre-stretching amount, post-stretching amount and forming temperature on the 3D hot stretch-bending of L-shaped cross-section profiles for TC4 titanium alloy were explored through the forming tests. Among them, the forming temperature is the most important factor affecting the springback deformation. The best forming conditions are achieved when the pre-stretching amount is as 100%εs and the post-stretching amount is as 20%εs (εs is the yield strain parameter) at a certain temperature. Based on the results of forming tests and material mechanics property tests, a finite element simulation model was established to predict the forming processes and springback processes of multi-point 3D hot stretch-bending process, and the errors of springback prediction are less than 15%, which verifies the validity of the model. In addition, the microstructures of TC4 titanium alloy before and after forming processes were observed. The results show that compared with the initial undeformed sample, the phase transformation of TC4 titanium alloy after 3D hot stretch-bending is produced, the (101-0) grain surface texture intensity is significantly increased, the two-phase grain sizes are reduced, the plastic deformation ability of TC4 titanium alloy formed parts is improved, and the geometrically necessary dislocation density is increased.

Multi-field Coupling Simulation and Analysis for Resistance Spot Welding of Three-layer Dissimilar Unequal-thickness Steels

LI Kunhang, ZHANG Siqi, WU Wei, HU Mingzhuo, SUN Yaling, XIONG Xin, HUANG Hong

2023, 34(24):  2996-3003.  DOI: 10.3969/j.issn.1004-132X.2023.24.011

Asbtract ( )   PDF (12519KB) ( )  

References | Related Articles | Metrics

A finite element model was established for resistance spot welding of DC01 with a thickness of 1.0 mm, DP590 with thicknesses of 1.2 mm and 1.5 mm. The energy distribution and stress-strain during the spot welding processes were analyzed using the multi-field coupling of thermal field, electric field, and force field. The test results show that the numerical simulation results are in good agree with the test ones. The peak current density decreases with time, and the distribution area is different from that of the two-layer plates, with a significantly larger area of distribution in the upper and lower plates compared with the middle plate. The potential changes indicate that initial heat generation in spot welding is mainly through contact resistance, which later transforms into bulk resistance. The temperature distribution on dissimilar unequal-thickness plates is uneven, with nucleation preferentially occurs on the lower part of the middle plate and on the DP590/DP590 contact surfaces. After the formation of the nugget, the middle part is under compressive stress, while the base material zone is under tensile stress at the nugget zone. The maximum strain value exists at the DP590/DP590 location.

Thermo-mechanical Fatigue Life Prediction and Optimization Design Method Based on Equivalent Component Model of Cylinder Head

YANG Wenjun, PANG Jianchao, KANG Xin, WANG Lei, LI Sicheng, ZHANG Zhefeng

2023, 34(24):  3004-3014.  DOI: 10.3969/j.issn.1004-132X.2023.24.012

Asbtract ( )   PDF (9409KB) ( )  

References | Related Articles | Metrics

In order to predict the fatigue life of cylinder heads of internal combustion engines more efficiently and simply and further to develop the optimization design, a thermo-mechanical fatigue life prediction and optimization design method was proposed based on the equivalent component model of cylinder heads. Numerical modeling of simulated components was achieved successfully by geometric characteristics of flame deck. Then applying the Sehitoglu theory, the effects of service loads on the thermo-mechanical fatigue damage were investigated. The results indicate that working speed has the most significant effect on the thermo-mechanical fatigue life, and mechanical damage is much dominant among the three damage types. Finally, based on the simulated components and response surface test design method, the optimization design of cylinder head components was carried out. The results show that the maximum stress is decreased by 7% at the region of nose bridge, fatigue life reaches 6.7×104 cycles, and the fatigue damage characteristics of cylinder heads are improved, which may provide a theoretical basis for the thermo-mechanical fatigue life prediction and structural optimization of cylinder heads under service conditions.

Numerical Analysis Method and Test for Contact Stress of Cycloidal Gear in RV Reducer

HUANG Xiangmao

2023, 34(24):  3015-3023.  DOI: 10.3969/j.issn.1004-132X.2023.24.013

Asbtract ( )   PDF (8857KB) ( )  

References | Related Articles | Metrics

The effective contact area and circumferential load distribution of cycloid gear tooth surfaces under specific loads were calculated by taking into account the elastic deformations and backlash of cycloid tooth surfaces. A mathematical model of contact stress in the tooth width direction of cycloidal gears was established by using force balance equation and deformation coordination equation, and the calculation procedure and flow chart were given. The mathematical model was a nonlinear equation set, by solving the nonlinear equations, the stress distribution and contact width in the tooth width direction of cycloidal gears were obtained. The mathematical model of contact stress and computational procedures were given to simulate the contact tooth width and contact stress distribution of cycloidal gear under ideal conditions and alignment errors. And the correctness and feasibility of the proposed method were verified by combined with testing and simulation results.