Table of Content

25 July 2021, Volume 32 Issue 14

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Two-way Fluid-Solid Coupling Simulation and Experimental Research of Sealing Rings Based on MpCCI Method

GONG Ran, ZHANG Zhenyu, CHENG Zhigao, XU Yi, ZHANG He

2021, 32(14):  1639-1646.  DOI: 10.3969/j.issn.1004-132X.2021.14.001

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To predict the fluid-solid coupling characteristics of sealing systems in transmission of heavy-duty off-road vehicles, the stress state of sealing rings in small confined spaces and the flow characteristics in flow fields of rotating sealing gaps were taken into account, and then the numerical models of two-way fluid-solid coupling for sealing systems were established and the solving methods were presented. The multi physics code coupling tool MpCCI was combined with FLUENT and Abaqus to carry out the numerical calculations of two-way fluid-solid coupling of rotary sealing systems. According to the fluid-solid coupling calculations, the flow states of oil in flow fields of rotary sealing gaps were obtained. The effective characteristics of sealing ring deformations on the leakage of rotary sealing systems and the friction torques of sealing rings were studied. The influences of transmission system working conditions on sealing ring performances were explored by two-way fluid-solid coupling dynamic simulation. Experimental investigations were performed in sealing performance test rig for sealing rings of vehicle transmission systems. Comparisons of numerical and experimental results show a good consistency of their change rules, which verifies the correctness of sealing fluid-solid coupling numerical models and calculation results.

Similarities Detection and Analysis of Tire Patterns Based on Similarity Theory

LI Hongling, DONG Yude, HUANG Zhihao, GAO Haoyu, TAO Senwang

2021, 32(14):  1646-1652.  DOI: 10.3969/j.issn.1004-132X.2021.14.002

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Based on the similarity theory, the characteristics of tire pattern structures were analyzed. Using image processing method such as gray histogram, aHash algorithm and co-occurrence matrix method, a 2D similarity detection system for tire patterns was built in MATLAB software. The similarities of the existing tire patterns were detected by the system, and the similarities of the specified patterns with local change and the original patterns were detected. Results show the stability and the reliability of the system. It may provide a basis for similarity quantization of different tire patterns.

A Fault Diagnosis Method of Rotating Machinery Based on LBDP

SHI Mingkuan, ZHAO Rongzhen

2021, 32(14):  1653-1658,1668.  DOI: 10.3969/j.issn.1004-132X.2021.14.003

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Aiming at the problems of classification difficulty caused by multi-class and high-dimensional complex characteristics of rotor fault data, a LBDP dimensionality reduction algorithm was proposed. First of all，the mixed features of the rotor vibration signals were extracted from multiple angles in time domain, frequency domain and time-frequency domain，and the high-dimensional feature sets were constructed. The original feature sets were fused by LBDP algorithm, and the low-dimensional sensitive feature subsets which might best reflect the intrinsic information of the faults were selected. Then the low-dimensional feature subsets were input into K-nearest neighbor(KNN) classifier for training and fault classification. The effectiveness of the proposed method was verified by the vibration signal sets of a double-span rotor systems, and it is proved that the method may extract the local discriminant information comprehensively and make the difference among fault categories clearer. 

Design and Adsorption Performance Optimization of Non-contact Variable Magnetic Gap Type Permanent Magnet Absorption Mechanisms of Pipe Climbing Robots

GUO Denghui, CHEN Yuan

2021, 32(14):  1659-1668.  DOI: 10.3969/j.issn.1004-132X.2021.14.004

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A non-contact variable magnetic gap type climbing robot was designed, which was adaptive adsorb tubes with different diameters. A magnetic field distribution model and magnetic adsorption force model of adsorption mechanisms were established by vector magnetic position method and finite element method. Based on equilibrium equation of space force system, the mechanics model of the robot was established and the minimum magnetic adsorption force was obtained. Based on the theoretical model of magnetic field and magnetic adsorption force and Maxwell simulation, the optimal magnet width and magnetic adsorption force were obtained by discrete combination method. After comparing different magnetic fields and magnetic adsorption forces, when the optimal magnet width is as 80 mm, the magnetic attraction force per unit volume of approximate circular arc mechanisms is as 0.0078 N/mm3, which is larger than 0.0047 N/mm3 of rectangular magnet. The magnetic adsorption force satisfies the load requirements of the minimum magnetic adsorption force of 2100 N. Finally, the magnetic adsorption force characteristics of the magnetic adsorption mechanisms were obtained by experiments. The results prove the feasibility of the optimization design of magnetic adsorption mechanisms.

Study on Thermal Coupling Durability of Mechanical Elastic Wheels under Random Loads

ZHANG Chen, ZHAO Youqun, ZHENG Xin, DU Yiyan

2021, 32(14):  1669-1676.  DOI: 10.3969/j.issn.1004-132X.2021.14.005

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In order to predict the maximum driving range of mechanical elastic wheels under random loads caused by uneven road surfaces under straight driving conditions, the durability of mechanical elastic wheels was studied. A finite element model for durability research was established based on structure characteristics of the wheels. Considering uneven roads, the relationships of speeds, dynamic loads and dynamic load coefficients of the wheels were determined, and the equivalent cyclic loads were applied to the wheels. Based on fatigue damage theory and fatigue test methods, the FE-safe software was used to predict the durability of wheels, and the maximum driving range is as 8787 km. The thermal coupling durability of the clasps was analyzed, and the minimum life position is the middle pin ear, and the maximum driving range is as 5258 km.

Generation Mechanism of Grinding Marks Based on Grinding Trace Simulations

CHEN Bing, LUO Liang, JIAO Haowen, DENG Zhaohui, YAO Honghui

2021, 32(14):  1677-1685.  DOI: 10.3969/j.issn.1004-132X.2021.14.006

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Because grinding marks would remain on spherical and aspherical surfaces in cross grinding, so generating mechanism of grinding marks was investigated based on grinding trace simulations. Distribution equation of grinding traces was established. Generation and distribution mechanism of grinding traces on ground surfaces was analyzed in cross grinding, and the generation mechanism of grinding marks caused by alteration of grinding parameters was revealed. From the results of simulations, it may be found that the distribution of grinding traces is dense at central areas and sparse at outer areas of ground surfaces, and the distributions are periodic and radial. Length regularity, shape regularity, and distribution regularity of all the grinding traces remained on the ground surfaces were similar, except a certain phase angle is varied among grinding traces. When ratio of grinding wheel rotary speed to workpiece rotary speed is as integer, the worst grinding traces of two adjacent periods are connected together end-to-end, which leads to coupling and propagation of cracks at the junction. And then, breakage situation of ground surfaces is aggravated. Finally, the broken grinding traces are connected together, and the grinding marks are generated.

Fixed-point Rubbing Characteristics of Magnetic Suspended Dual-rotor Systems

WANG Dongxiong, WANG Nianxian, CHEN Kuisheng

2021, 32(14):  1686-1699.  DOI: 10.3969/j.issn.1004-132X.2021.14.007

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Impact forces of magnetic suspended dual-rotor systems(MSDS) in fixed-point rubbing processes were described with Lankarani-Nikravesh model. Vibration characteristics and contact processes of the MSDS with fixed-point rubbing were analyzed based on MSDS dynamic model established with finite element method. Research results indicate that, when rotation frequencies of inner rotors and outer rotors are integer multiple of the rotational frequency difference, integer frequency components of rotational frequency difference are observed when rubbing occurs. As the degree of rubbing increases, the fractional frequency components of rotational frequency difference appear. Maximum contact depth and impact forces in the rub-impact processes depend on initial impact speed. Moreover, suitable proportional coefficient making the system angular velocity speeds far away from critical angular velocity and large differential coefficient may significantly reduce the severity of the rub-impact.

Nonlinear Modal Analysis of Parallel Pointing Mechanisms Considering Time-varying Clearances

SUN Jing, HAN Xueyan, WEI Yuanhao, CHEN Shuang, LI Shihua,

2021, 32(14):  1700-1708,1715.  DOI: 10.3969/j.issn.1004-132X.2021.14.008

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Aiming at the problems that it was difficult to establish the vibration model of the complex space mechanisms, a simple modeling method of the vibration model of the parallel pointing mechanisms was proposed based on the number axis method, and the feasibility of the method was proved by the ANSYS modal analysis. In order to study the dynamic influences of the clearances of the kinematic pair on the modal characteristics of the mechanisms, considering the residual stiffness of the kinematic pairs, an improved method for establishing the nonlinear equivalent stiffness coefficient of the kinematic pairs with clearances was proposed. The improved nonlinear equivalent stiffness coefficient was embedded in the mechanism vibration model, and a nonlinear vibration model was established considering the clearances of the time-varying kinematic pairs. The ADAMS was used to simulate the dynamics of the mechanisms considering the clearances. According to the simulation data, the nonlinear modal characteristics of the mechanisms affected by the time-varying clearances were analyzed. The research results may provide a theoretical basis for the dynamic performance optimization, vibration suppression and fault diagnosis of the parallel pointing mechanisms.

Fatigue Crack Growth Prediction Based on NPF Algorithm

GU Zhenhua, LI Ke, GU Jiefei, , SU Lei, SU Wensheng

2021, 32(14):  1709-1715.  DOI: 10.3969/j.issn.1004-132X.2021.14.009

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A fatigue crack growth prediction method was proposed based on NPF algorithm, aiming at solving the problems that traditional Paris fatigue crack growth model had low accuracy and could not take the influences of various uncertain factors in the crack growth processes into consideration. State space equations were used to characterize crack growth processes based on Paris formula. Observation space equations were established using monitoring technology based on Lamb waves.The real-time observation information was used to modify the predicted values of the model. Finally, the effectiveness of the method herein was verified by the fatigue crack growth experiments of Q235 steel specimens. Experimental results show that the NPF algorithm may effectively correct prediction errors of Paris formula in fatigue crack growth prediction. The prediction accuracy is better than that of the extended Kalman filter and particle filter(PF) algorithms, and the algorithm efficiency is significantly better than that of PF algorithm.

Programming by Demonstration with Virtual Fixture Assistance for Robotic Machining of Complex Surfaces

GE Kedi, ZHAO Huan, CHEN Pengfei, DING Han

2021, 32(14):  1716-1725.  DOI: 10.3969/j.issn.1004-132X.2021.14.010

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 In order to solve the difficulties of virtual fixture construction and adaptive adjustment according to the operators intention in robot programming by demonstration for complex surface machining,a Programming by Demonstration (PbD) strategy for virtual fixture generation and iterative updating was proposed. A prior virtual fixture was constructed offline by demonstrating surface manifold. If the prior virtual fixture matched the surfaces to be machined, the spring-damping system was used to online compensate the path deviations of demonstration. Otherwise, the iterative correction was realized by adaptive adjustment of virtual fixture stiffness and flexibility. The results show that the construction of virtual fixture based on surface manifold is simple and has generalization characteristics, which improves the construction efficiency of complex surface virtual fixtures; in the auxiliary demonstrating processes of the virtual fixtures by using the sinusoidal and fan track , the position and orientation errors of auxiliary demonstrated path may be decreased at least by 84% and 81% respectively, and the virtual fixture may be adjusted adaptively according to the operators intention to better match the target surfaces.

Influences of Service Conditions on Fatigue Properties of Stainless Steel Spot Welding and Cracking Analysis

JIANG Yunlu, YANG Liang, HAN Xiaohui, XU Ye, CHEN Huaining, CAI Guixi

2021, 32(14):  1726-1731.  DOI: 10.3969/j.issn.1004-132X.2021.14.011

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Joints of resistance spot welding on stainless steel body frame was used as research objects to find out the influences of temperature (-40 ℃, room temperature, 70 ℃), stress ratio(0.1，0.5) and 3.5% NaCl environmental medium on joint fatigue lifes. The electron back-scattered diffraction(EBSD) technology, scanning electron microscopy(SEM), instrumented ball indentation system(IBIS) and tensile-shear experiment were used to analyze the grain orientation, residual stress distribution, appearance of fatigue fractures and the mechanics properties. Results show that the fatigue property is better due to the increasing of material strength under low temperature conditions. And the high-cycle fatigue property is better due to the improvement of plastic property under 70 ℃. The fatigue property of stress ratio of 0.1 is better than that of 0.5. Corrosion medium and tensile stress may accelerate the strress corrosion, cracking and rapid dissolution of anode regions of crack top ends, accelerate the initiation and extension of the cracks，and may significantly reduce fatigue life of spot welding joints. The fatigue cracks are nucleated on the stress concentration interfaces, the cracks grow up along the softening zones and extend to the plate surfaces until fracture failure.

Multi-scale Analysis of LVI and CAI Behaviors of Plain Woven Carbon-fiber-reinforced Composites

ZHAO Qiaoli, HOU Yuliang, LIU Zeyi, LI Cheng

2021, 32(14):  1732-1742.  DOI: 10.3969/j.issn.1004-132X.2021.14.012

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A multi-scale modeling strategy was proposed to investigate LVI and CAI behaviors of plain woven carbon-fiber-reinforced composites. The multi-scale modeling strategy mainly consisted of microscale, mesoscale and macroscale models. Firstly, the microscale representative volume element of “carbon fibers and matrix” was constructed to predict effective mechanics parameters of yarns. Moreover, the mesoscale unit cell model of “yarns and matrix” was built based on the internal geometric configuration of plain woven composites and the obtained effective mechanics parameters. Various loading scenarios were performed on the mesoscale model by periodic boundary conditions to predict effective mechanics properties of the mesoscale unit cell model. Meanwhile, the mesoscale unit cell model was simplified as an equivalent cross-ply laminate(ECPL) model with 0° and 90° layers using local homogenization method. And then, the array of ECPL model was extended to macroscale model, aiming to study the LVI and CAI behaviors. Finally, the validity of the proposed model was verified by the comparisons between the experimental and numerical values of LVI and CAI tests under different impact energy levels respectively.

Research Progresses on Influences of Alloying Elements on Formation of Bainite and Mechanical Properties for High-strength Steel Weld Metals

ZHANG Tianli, WU Wen, YU Hang, LIN Sanbao, LI Zhuoxin

2021, 32(14):  1743-1756.  DOI: 10.3969/j.issn.1004-132X.2021.14.013

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In welding processes of high-strength steels, it was difficult to match the strength and toughness between weld metal and base metal. Thus it was urgent to refine regulation and control systems for alloying elements and improve strengthening and toughening mechanism of high-strength steel weld metals. Bainite is the important microstructure and had a significant influence on the toughness of high-strength steel weld metals, so formation mechanism of typical bainite and bainite analysis methods were summarized. The influences of alloying elements on the microstructure and mechanical property of high-strength steel weld metals were reviewed. Values of each alloy element were recommended, which aimed to give reference for regulation and control systems for alloying elements of high-strength steel weld metals. 

Development of Non-rigid Support FSW Repair Equipment for Aluminum Alloy Car Bodies

WANG Wen, JIN Taotao, ZHANG Jun, MA He

2021, 32(14):  1757-1763.  DOI: 10.3969/j.issn.1004-132X.2021.14.014

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The existing FSW repair equipment was mostly fixed gantry structure, and needed rigid back support, the mobility adaptability was poor. Aiming at the problems of repairing the damaged aluminum alloy freight car bodies, a scheme of on-line repair by FSW was proposed, and a mobile non-rigid support FSW repair equipment was designed. In order to solve the problems of insufficient support and large deformation in the welding repair of non-rigid support, the rotating telescopic arm, petal type anvil plate and other structures were designed to provide enough jacking forces for welding, and the structure of petal type cutting board was optimized by finite element analysis to improve the support effectiveness. An automatic adjustment structure of milling welding radius was designed for repair welding of different sizes of damages. The non-rigid support FSW mobile repair equipment could repair 6 mm thick aluminum alloy bodies without disassembling the body plate. Practical applications show that the welding repair effectiveness is good by using non-rigid support FSW, the welding surfaces are smooth without burrs, and there are no groove tunnel defects inside. Besides, the tensile property of the weld is about 71.6% that of the base metal.