Table of Content

25 November 2021, Volume 32 Issue 22

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Tool Wear and Remaining Useful Life Estimation of Difficult-to-machine Aerospace Alloys：a Review

LUO Huan, ZHANG Dinghua, LUO Ming

2021, 32(22):  2647-2666.  DOI: 10.3969/j.issn.1004-132X.2021.22.001

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 Due to the special application requirements, such as light weight designs, strength,in aeronautical manufacturing field, a large number of difficult-to-machine materials such as titanium alloy and nickel-based alloy were used, and the cutting tools wore fast. Excessive tool wear would affect product quality. Under the premise of ensuring product quality, it was urgent to monitor tool wear states and to predict tool remaining useful life in order to make full use of the cutting tools. The definition, classification and models of the cutting tool remaining useful life estimation were described herein. Meanwhile tool wear monitoring was the basis and prerequisite of tool life prediction, the main steps and common models were briefly described. The remaining useful life prediction models might be categorized into physics-based models, data-driven models and hybrid models. The advantages and disadvantages of different prediction methods and their application scenarios were summarized , and the future research directions were discussed.

Random Failure Model and Multi-element Damage Assessment of Long Endurance Aircrafts

BAI Shuwei, JIANG Nan, TONG Mingbo, CHANG Wenkui

2021, 32(22):  2667-2672.  DOI: 10.3969/j.issn.1004-132X.2021.22.002

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To evaluate the multi-element damages that occured during the aircraft services, a random failure model was established based on element fatigue characteristics, and the average behavior of widespread fatigue damages were calculated based on element failure life to determine the time for aircraft inspection and repair. The validity of the model was verified by a five-frame fuselage section example, and the influences of simulation times and distribution model on the repair time of multi-element damage structures were studied. According to the fatigue test results of the seven-frame fuselage section, multi-element damage assessment was performed, the structural inspection and repair time were given. The results show that the evaluation results are in good agreement with the calculation example data, and normal regression may better simulate structural failure characteristics.

Preparation and Properties of MREATs

XU Zhiqiang, WANG Qiuliang, WU Heng, WANG Jun, ZHANG Gaofeng

2021, 32(22):  2673-2680.  DOI: 0.3969/j.issn.1004-132X.2021.22.003

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MREAT, a new flexibility-controlled material used for grinding and polishing was developed to solve the problems of low machining efficiency, causing surface damages and difficulty in polishing complex curved surfaces in the ultra-precision machining processes. The influences of external magnetic fields on the microstructure and properties of MREAT were studied. A heat-magnet-force coupled device was designed to prepare anisotropic and isotropic MREATs with and without magnetic fields. Then the influences of external magnetic fields on the microstructure, compression mechanics properties and material removal properties of the new abrasive tool were analyzed. The results show that the magnetic field applied during the preparation processes causes the interior of the MREAT to appear as microscopic chains composed of carbonyl iron particles. After the preparation is complete, the compressive elastic modulus and polishing performance of the MREAT continue to increase with the increase of the magnetic fields. By analyzing the influences of the magnetic fields on the microstructure and performance of the MREAT, it is proved that the MREAT may realize the magnetically controlled flexible polishing processes.

Multiple Support Point Reaction Force Calculation Considering Virtual Elastic Stiffness of Support Surfaces

XU Jinshuai, QI Zhaohui, ZHUO Yingpeng, LIU Haibo, GAO Lingchong

2021, 32(22):  2681-2688，2696.  DOI: 10.3969/j.issn.1004-132X.2021.22.004

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Based on the objective physical fact that the supporting surface would make the supporting point move slightly, the micro variable degrees of freedom independent of the macro constraints were introduced to describe the gap function at the support points, and the virtual elastic stiffness of the support surfaces was introduced to describe the resistance of the support surfaces. In order to overcome the difficulty of numerical solution caused by the "switch effect" of virtual elastic stiffness, the transition function was introduced to smooth that. According to the macroscopic force condition, the equilibrium equation was established, and the support reaction of the support points was obtained by solving the nonlinear equations. A variety of support reactions were calculated and compared with the experimental data to verify the effectiveness of the proposed method.

Research on Friction and Wear Characteristics and Simulation of Microstructures Surface Unfolding Wheels

PAN Chengyi, TONG Yuanqi, CAO Guanqun, ZHAO Yanling

2021, 32(22):  2689-2696.  DOI: 10.3969/j.issn.1004-132X.2021.22.005

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In order to improve the service life and detection accuracy of the unfolding wheels in the AVIKO series steel ball inspection system, and to improve the surface friction coefficient while redu-cing wear, the surface microstructures were applied to the unfolding wheels to study the friction and wear characteristics. Three kinds of pit microstructures with different diameter parameters were processed on the outer surfaces of the test pieces by laser, and the friction coefficient and wear amount were obtained through the tests with a self-designed friction and wear tester, and the distribution of stress and wear depth were obtained by numerical simulation. Compared and analyzed with smooth surface test pieces, the results show that the friction coefficient of the microstructure surface test pieces is larger and the wear amount is smaller under dry sliding friction conditions. The microstructure surface reduces wear and improves wear resistance by changing the stress distribution and dispersing the position of wear points. The established numerical simulation wear model may be used to predict the wear depth of microstructure surface, which provides a basic theory for the life prediction of microstructure surface unfolding wheels.

Lightweight Mobile Hole-drilling System Positioning Method Based on Redundant Reference Holes

ZHANG Haowei, CHEN Wenliang, WANG Min, PAN Jinwei, HUANG Wen

2021, 32(22):  2697-2704.  DOI: 10.3969/j.issn.1004-132X.2021.22.006

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In the automatic assembly processes of aircrafts, the precise positioning of the hole-drilling system would directly affect the assembly accuracy. Generally, the reference hole was manually prepared in advance, the position of the reference hole under the hole-drilling systems was detected, and the spatial conversion relationship was obtained by comparing with the position in the products to complete the system positioning. In order to improve the positioning accuracy of the lightweight mobile hole-drilling system, a positioning method of the lightweight mobile hole-drilling system was proposed based on redundant reference holes. The space conversion relationship was reconstructed by using Rodrigues matrix, and the deviation filtering algorithm of redundant reference holes was proposed, thus judging the large deviation hole position in the redundant reference hole that affected the space conversion accuracy, improving the accuracy of the conversion relationship, and improving the positioning accuracy of the hole making system. A calculation example was analyzed and the experimental verification was carried out. It is demonstrated that the method may accurately screen and remove large deviation hole positions in redundant reference holes, and increase the space conversion errors are reduced to less than 0.12 mm. According to the error transfer theory, the positioning accuracy of the hole-drilling system is improved by approximately 20%.

Study on Anti-rollover of Counterbalanced Forklift Trucks Based on Extension Hiearchical Control

ZHANG Yang, XIA Guang, TANG Xiwen, WANG Shaojie, SUN Baoqun

2021, 32(22):  2705-2715.  DOI: 10.3969/j.issn.1004-132X.2021.22.007

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 Based on the analysis of the structural characteristics and the rollover mechanism of the counterbalanced forklifts， an anti-rollover control strategy for counterbalanced forklifts was proposed based on extension decision， and the anti-rollover extension hierarchical controller including upper layer extension control and lower layer execution control was designed. The upper layer extension controller divided the forklift anti-rollover control domains into a classic domain， a extension domain， and a non-domain， and determined the weight coefficients of the lower layer execution controller. The lower layer execution controller received the weight coefficients determined by the upper layer extension controller， performed control weight distribution on the yaw rate controller and the lateral acceleration controller， and executed the commands to realize the anti-rollover extension control of the counterbalance forklifts. The European standard condition simulation and real vehicle test results show that the anti-rollover control strategy of the counterbalance forklifts based on the extension decision may effectively reduces the roll ranges of the forklifts under high-speed emergency steering conditions， prevents the forklift from rolling over and improves the stability and active safety of the counterbalance forklift trucks. 

Gear Fault Diagnosis Based on Deep Learning and Subdomain Adaptation

JIE Zhenguo, WANG Xiyang, GONG Tingkai

2021, 32(22):  2716-2723.  DOI: 10.3969/j.issn.1004-132X.2021.22.008

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Aiming at the insufficient labeled fault data in real cases, a method was proposed based on deep learning and subdomain adaptation. The domain-shared one dimensional CNN was first used to extract transferable features from the fault data. Then, the multi-kernel local maximum mean discrepancy was used to measure the distribution discrepancy of the learned transferable features relevant subdomains, and the measured distribution discrepancy was added to the objective function for training. Finally, the trained model was used to identify the health conditions of the target domain. The results show that the proposed method may achieve high accuracy in the case of target domain data without label.

Local Scanning Point Cloud Localization of Aircraft Skins Based on Multi-descriptor Voting

ZHANG Yiming, LI Hongwei, ZHAO An'anX, IE Qian, WANG Jun

2021, 32(22):  2724-2730,2771.  DOI: 10.3969/j.issn.1004-132X.2021.22.009

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In order to improve efficiency of digital aircraft skin detection, aiming at the alignment problems of local aircraft skins and the digital model, a local scanning point cloud localization algorithm was proposed based on multi-descriptor voting. The localization region on the digital model was determined by various 3D point cloud descriptors, since they had discrepancy in recognition ability. A weighted voting point method was proposed to decrease deviation. A well-designed comparision experiment and a concrete example on real data were conducted. The results are as follows: compared with the methods based on single descriptor, the localization accuracy is improved by 37.5% on average. The algorithm is feasible in practical engineering.

Simulation of Corrugated Rolling of Mg/Al Composite Plates and Analysis of Microstructure Evolution in Deformation Zone

SHEN Hongzhuo, LIU Yuanming, LIU Yanxiao, WANG Tao, LIU Yanping,

2021, 32(22):  2731-2738.  DOI: 10.3969/j.issn.1004-132X.2021.22.010

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By establishing the thermal-mechanical coupled finite element model of corrugated rolling of Mg/Al composite plates, the rolling block experiment was carried out. The effects of stress, strain and temperature on metal deformation and microstructure evolution were analyzed. The results show that the composite plates are bonded near the exit of deformation zones when the initial rolling temperature is as 400 ℃ and the average reduction rate is as 35%. The thickness of diffusion layer at the trough is as 3.3 μm, and the diffusion layer at the peak is as 2.7 μm. The increases of equivalent strain and temperature promote the dynamic recrystallization of the deformed grains of magnesium alloy. The microstructure mainly includes equiaxed grains, twins and dynamic recrystallization grains. The average grain sizes are as 3.71 μm and 6.92 μm at the trough and peak respectively.

Microstructure and Mechanics Property Variations during MDIF of Ti-6Al-4V Alloy with a Martensitic Microstructure

ZHANG Zhixiong, ZHANG Juntao, HAN Jianchao, ZHANG Changjiang, ZHANG Shuzhi, WANG Tao,

2021, 32(22):  2739-2748.  DOI: 10.3969/j.issn.1004-132X.2021.22.011

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The as-cast Ti-6Al-4V alloy was subjected to a heat treatment condition to obtain a typical α′ martensitic microstructure. After two-step isothermal forging, a homogeneous equiaxed grained microstructure with an average grain size of 1.5 μm was achieved. The refined microstructure led to a significant mechanics property improvement. The fine grained Ti-6Al-4V alloys exhibited high yield strength(906 MPa), high ultimate tensile strength(954 MPa), and good ductility(16.7%). The finer grain size and better mechanics properties indicate that the phase transformation of α′/α+β strongly contributed to the microstructure refinement during isothermal forging of Ti-6Al-4V alloys. After the first step forging, the microstructure near the center of the forging is highly deformed, while very little deformations are present in the center regions near the die due to the effects of die chilling and friction. After the second step forging, α lamellae are fully globularized and the microstructure is homogeneous. The crystal rotations of the grains near the center are larger than that of the grains in the midway from the center to the outer edge.

Adaptive Fitting for Blade Tip Timing Signal's Trend Terms

LIU Zhibo, DUAN Fajie, YE Dechao, FENG Junnan, XIONG Bing

2021, 32(22):  2749-2756,2764.  DOI: 10.3969/j.issn.1004-132X.2021.22.012

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Blade tip timing measurement was a key measurement technology in aero-engine blade vibration monitoring systems. As an important part of timing signal preprocessing, the trend term fitting was the basis and premise of high-precision parameter identification of the blade vibrations. Under the continuous variable operating conditions of aero-engines, the current trend item fitting method could not adaptively adjust the width of the fitting windows, resulting in the poor quality of eliminating the trend items and seriously affecting the subsequent blade vibration analyses. Aiming at the problems of timing signal trend item fitting under continuing variable operating conditions, this paper used correlation coefficient as the evaluation of trend item fitting quality, and proposed a trend item fitting method with the window widths of adaptive adjustment. The tip-timing test data of an aero-engine high-pressure compressor was used for verification. The results show that the method may ensure the optimal fitting quality of the trend item due to adaptively adjusting the widths of the window. Under the premise of removing the trend item, the original vibration information may be completely retained, which is of great significance to achieve high-precision parameter identification of the blade vibrations.

Analysis of Safe Adsorption Conditions and Motion Characteristics of Rolling Sealed Tracked Wall-climbing Robot

JIANG Dezheng, HU Jun, ZHONG Heng, WANG Hongguang, SONG Yifeng, YUAN Bingbing,

2021, 32(22):  2757-2764.  DOI: 10.3969/j.issn.1004-132X.2021.22.013

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To complete the defect detection of the Three Gorges Dam channel, a crawler wall climbing robot with a rolling seal structure was designed and developed. The robot used a flexible track as a sealing skirt to achieve rolling sealing, which was with the characteristics of excellent wear resistance of the sealing structure, good trafficability and strong adaptability to the wall surfaces. As the adsorption stability is the key to the design of the robot，the sliding parameters and other indexes were proposed as the stable adsorption conditions of the rolling seal wall climbing robot based on the dynamics modeling method，which were used to investigate the adsorption stability and movement accuracy of the robots in the moving states, especially in the sliding steering states. The relationship between the key design parameters and the adsorption stability of the robots was established by discussing the influences of the vacuum pressure on the slip and stable adsorption of the robots. The simulation and experimental results show that the proposed safe adsorption condition can be used as the theoretical basis for the optimal design of the motion performance of the wall climbing robots, and also provide a reference for the establishment of the corresponding control model.

Development of Booming Performance of Rear-drive Vehicles Based on Multi-body Dynamics Models

WANG Kun, NI Xiaobo, LI Honggeng, HE Jiayang, HUANG Yuanyi, HOU Gaojie

2021, 32(22):  2765-2771.  DOI: 10.3969/j.issn.1004-132X.2021.22.014

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In response to the unusually obvious booming problems of the rear-wheel drive vehicles during operation, the booming tests were conducted on the entire vehicle to confirm the booming states. At the same time, the bench sweep frequency tests were performed on the transmission systems of the rear-drive vehicles to study the influences of the transmission system resonance mode on the booming vibrations. Building the multi-body dynamics model of the vehicles with the help of ADAMS software, using the model after the benchmarking to perform modal analysis calculations to study the mechanism of booming vibrations, and then a plan was formulated to improve the booming vibrations, and to verify the booming vibrations on the actual vehicles. The results show that the improvement plan for the clutch stiffness and the vibrations of the drive shafts may effectively solve the booming problems of the rear-drive vehicles.