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2016 Vol. 42, No. 2

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Volume 42 Issue22016
2016 Year 42 Volume 2 Issue E-journal
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Experimental analysis on micro-structure of three-dimensional full five-directional braided composites
LIU Zhenguo, YA Jixuan, LIN Qiang, WANG Yibo, HU Long
2016, 42(2): 211-217. doi: 10.13700/j.bh.1001-5965.2015.0084
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The micro-structure of three-dimensional (3D) full five-directional braided composite is investigated.Three-dimensional full five-directional braided composite is a new kind of braided composite. The micro-structure plays an important role in predicting performance of the material. Micro-computed tomography (micro-CT) is used to get the cross-section images of the three-dimensional full five-directional braided composites. Glass fiber as tracer yarns is mixed into the sample made of carbon fiber to improve its contrast in the images. The solid model of tracer yarns created by 3D reconstruction with these images is used to study the cross-sections and orientations of the fiber tows through CAD technology. The results show that the cross-sections of braiding yarns and axial yarns change with the regions and the heights in one pitch of the material; the spatial orientations of braiding yarns are not the same in different regions. The axial yarns are almost straightened in space. The surface of the axial yarns has helical indentation because of the extrusion of braiding yarns on axial yarns.
Transfer learning for activity pattern in smart environment
WANG Chengliang, WANG Yunpeng
2016, 42(2): 218-226. doi: 10.13700/j.bh.1001-5965.2015.0085
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Due to huge costs and operational difficulties in learning and mining activity patterns in smart environment, we propose a framework for activity pattern transfer. The process of activity pattern transfer is divided into two parts: trajectory transfer and trigger duration transfer. Firstly, fuzzify the trajectories and trigger durations in the existing activity patterns. Secondly, generate alternative trajectory set through alternative path set generation (ATSG) algorithm in a new environment. Finally, map the trajectories from activity patterns and trajectories from alternative trajectory set through similarity computing (SC) algorithm, and transfer activities' information through trajectory mapping (TM) algorithm and trigger duration transfer (TDT) algorithm. Thus, activity patterns are transferred to the new environment. Theoretical analysis and experimental results show that, compared to frequent pattern mining, the method in our paper can substantially reduce time overhead of obtaining activity patterns in new environment. At the same time, it performs well in recognizing activities.
Failure criterion and durability characteristics of metal rubber under static compression load
MA Yanhong, ZHANG Qicheng, ZHANG Dayi, ZHU Haixiong, LU Hongwei, HONG Jie
2016, 42(2): 227-235. doi: 10.13700/j.bh.1001-5965.2015.0081
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Metal rubber(MR) is widely applied in vibration control, vibration isolation and shock resistance areas because of its characteristics of elasticity, damping, reliability and adaptation to the operational environment. It is critical for the system safety to accurately define the failure criterion and forecast the failure of MR in engineering. The failure criterion and durability property of MR under long-term static compression load were studied through the experimental method. The result shows that it is feasible to determine the MR failure by the structure deforming factor and mechanical property decaying factor, besides, the failure status and durability life can be determined by confirming the thresholds of these factors. The failure criterion factors of MR shows multi-stage property varying with loading time,denoting the change of MR inner micro structure and forced state with continuous loading time. In the test result of this paper, the metal rubber specimens exhibit no deforming failure under different static load status. However, under larger static load condition, the durability life of MR can be greatly decreased, resulting in excessively large tangent modulus decaying factor and obvious failure of MR mechanical properties.
Influence of hydro-ski load reducing performance corresponding on some parameters
GAO Xiaopeng, SUN Peicheng, DONG Zushun, WU Bin, WEI Keke
2016, 42(2): 236-242. doi: 10.13700/j.bh.1001-5965.2015.0079
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The impact load of amphibious aircraft could be reduced efficiently by use of hydro-ski, and the load reducing effect of hydro-ski is obviously relevant with some motion parameters of the aircraft. General coupling method was used to simulate the water landing performance of an amphibious aircraft and the comparison between the calculated results and the model test ones was carried out to prove the effectiveness of the simulation method. The study analyzed the influence of hydro-ski touch attitude angle,aircraft touch horizontal velocity and vertical velocity on load reducing performance of the hydro-ski. Conclusion could be obtained that the influence of the above three factors on hydro-ski load reducing performance is relatively remarkable, and the impact load could be reduced more efficiently with the proper hydro-ski attitude angle and velocities.
Pseudo-multi-source-sampling complex domain FastICA for impact location
YUAN Mei, NIU Ben, DONG Shaopeng, YU Liang
2016, 42(2): 243-250. doi: 10.13700/j.bh.1001-5965.2015.0096
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Using the sensor array to locate impact can help to detect damage and its potential threats for structure materials, and to ensure structural safety. Sensor array signals are preprocessed by blind source separation (BSS). A single-channel pseudo-multi-source-sampling method is proposed, and data sequences of one sensor in different periods are used as multi-source observation signals of this sensor. The signals of all sensor arrays are used as inputs of complex domain FastICA impact extraction algorithm. Shock signals with phase information are separated from each sensor. The coordinates of impact events on test plane are solved by using the threshold time delay localization method. theoretical analysis and numerical simulation verify the effectiveness of the combined impact location algorithm. Experiment on the impact location platform shows that designed algorithm can separate out the impact from the signals mixed with vibration. It is suggested that the algorithm improves the precision of time delay analysis for impact location in the sensor array. It also provides a practicable solution for the underdetermined blind source separation problem while the number of sensors is less than the sources.
Analysis on aircraft cylinder seal property based on mixed lubrication theory
OUYANG Xiaoping, XUE Zhiquan, PENG Chao, GUO Shengrong, ZHOU Qinghe, YANG Huayong
2016, 42(2): 251-257. doi: 10.13700/j.bh.1001-5965.2015.0387
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Aimed to investigate the influences of working conditions such as different pressures, temperatures and velocities on the performance of the seal of the aircraft cylinder, the Turcon VL seal from Trelleborg AB was analyzed based on the mixed lubrication theory. The macro and micro multi-field coupling model based on the mixed lubrication theory was built, which mainly includes fluid model with cavitation and fluid factors in Reynolds equation, micro contact model of Greenwood-Williamson(G-W) and heat transfer model of Fourier. By computing the model with finite volume method, the characteristics of macro contact pressure, micro contact pressure and oil pressure distribution under different fluid pressures were analyzed. The research results show that the seal leakage and friction increases nearly linearly with the fluid pressure increasing, the seal has no leakage at 25℃ but has some at 135℃, and the seal friction decreases but leakage increases with the cylinder velocity increasing.
Influence of rotor-stator interaction on rotor blade flutter characteristics
YANG Hui, LI Zhenpeng
2016, 42(2): 258-264. doi: 10.13700/j.bh.1001-5965.2015.0094
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A full-annulus multi-row coupled fluid-structure simulation on a certain high pressure compressor was conducted by an in-house program to analyze the influence of inlet guide vane (IGV) on rotor blade flutter stability in different operation conditions and geometry models. The effectiveness of the program in the field of turbomachinery flutter was verified by numerically simulating the aeroelastic standard configuration 4 for the IGV-rotor model and isolated rotor model respectively, detailed fluid-structure interaction analyses were performed at near choked, near design and near stall operation points to assess the effect of nodal diameter on the flutter stability. The least unstable vibration form of blade can be presented. By the comparison of the results, the influence of IGV varies with the operation conditions. At the near choked point, the rotor aerodynamic damping of the first bending mode increases by 130.63% via the IGV. The results indicate that the existence of the guide vane causes the unsteady pressure wave reflection, which can enhance the unsteady oscillating pressure amplitudes on the rotor blade surface and improve the flutter stability of the bending mode. Flutter analyses based on isolated rotor model will give inaccurate aerodynamic damping values.
Oil film analysis of swash plate/slipper pair based on CFD
MA Jiming, SHEN Yayong, LI Qilin
2016, 42(2): 265-272. doi: 10.13700/j.bh.1001-5965.2015.0107
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The 3-D Navier-Stokes equations and arbitrary Lagrangian-Eulerian (ALE) method are firstly used to present the oil film analysis method based on computational fluid dynamics (CFD), which can describe the correlation among slipper structure parameters, running conditions and oil film thickness. Then, the oil film thicknesses of a slipper bearing under 24 different running conditions are obtained by simulation method. A function is consequently obtained based on the simulation results, which can express the relationships between running conditions (temperature, rotation speed, and outlet preesure) and oil film thickness. Furthermore, an equation of hydraulic dynamic parameter is provided and used to express the oil film thickness analytically. Based on the CFD simulation results, the parameter is proven to be only related with the oil viscosity (temperature) under fixed design structure, and unrelated with other running conditions, such as rotation, pressure, and so on. It is convenient for designer to derive the oil film thickness expression equation. Finally, we compared the oil film thicknesses obtained from analytical and CFD methods, and the results show that the presented method is feasible.
Sequential-image-based space object 3D reconstruction
ZHANG Haopeng, WEI Quanmao, ZHANG Wei, WU Junfeng, JIANG Zhiguo
2016, 42(2): 273-279. doi: 10.13700/j.bh.1001-5965.2015.0117
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Space object 3D reconstruction is of important significance for both space situational awareness and theoretical study. A new structure from motion method was proposed to avoid the reconstruction error caused by the symmetrical structure and similar texture of space targets. In this method, new images were added sequentially for reconstruction using the imaging time as a priori knowledge. In addition, image simulation of space target and ground imaging simulation experiment were carried out for the lack of space target image data. And experiments on the simulated space target images, in which the motion analysis results are accurate and robust to noise, and the recovery 3D point cloud can express the structural information of the target to a certain extent, have demonstrated the effectiveness of the approach proposed, and the boundary conditions of multi-frame-image for 3D reconstruction are acquired as well.
Simulation of prey stopping process by spider webs based on finite element method
YU Hui, YANG Jialing, LIU Hua
2016, 42(2): 280-286. doi: 10.13700/j.bh.1001-5965.2015.0089
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In order to discover the mechanical characteristics of spider webs to capture a flying prey, the actual stopping process is investigated based on the theoretical and finite element methods (FEM). First, the stress-strain relationships were built for radial silks and capture spirals in the orb web from the existing experiments. Then, the dynamic response of a single silk thread under transverse impact was solved theoretically. The problem was also simulated using the LS-DYNA software and the numerical results were in good agreement with the theoretical solution. Finally, the actual process for the real web stopping a flying prey was simulated by the LS-DYNA software. The predicted maximal strain of silks in the web and the energy curves agree with the existing experiment results. The numerical simulation shows that the radial silk plays an important role in absorbing the kinetic energy of the flying prey. The stress of radial silks near the impact point is rather low, which is helpful in localizing the damage of radial threads in contact with the prey and repairing the web. When the prey impacts the web with large kinetic energy, the best intercept area is near the middle region of radial threads.
Test and numerical simulation on shear property of 3D braided composite straight pin
HU Long, LIU Zhenguo, WANG Yibo, LIN Qiang, YA Jixuan
2016, 42(2): 287-293. doi: 10.13700/j.bh.1001-5965.2015.0105
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Joining technique using composite fasteners is one of the key technologies for the manufacturing of composite structures. Test and numerical research on the shear property of 3D braided composite straight pin fastener is presented. Three-dimensional full five-directional braided technology is used to fabricate the specimens. The shear tests of the specimens are preformed to study the ultimate bearing capacity and failure style of the 3D braided composite straight pin. A homogenization method is used to predict the elastic constants of the straight pin specimens. A strength analysis method is established to describe the strength characteristics of the 3D braided composite straight pin specimens. The modified Tsai-Hill failure criterion and continuum damage theory are introduced into the method. According to this method, a finite element model is developed to simulate the progressive damage process of the specimens. Good agreements are achieved in the load-deflection curves and damage distributions between test and numerical results under shear load, indicating that the proposed analysis method is effective and feasible in predicting the macroscopic strength of 3D braided composite structures.
Calculation method of blade element aerodynamic loads based on small perturbation theory
WANG Wei, LI Dongsheng, LIU Chun
2016, 42(2): 294-302. doi: 10.13700/j.bh.1001-5965.2015.0087
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A calculation method of blade element aerodynamic loads based on small perturbation theory is established for helicopter flight simulation application. The method synthesizes flap-lag-torsion elastic rotor blade mode, couples rotor dynamic inflow, unsteady aerodynamics model with dynamic stall and rotor trimming model. The entire model is developed in a standard state-space form. To verify this model, the UH-60A helicopter is taken as an example, and the effects of yaw flow on rotor aerodynamic performance are studied at low speed flight and high speed flight. It is shown that yaw flow has a greater effect on rotor aerodynamic performance at high speed flight. Blade induced velocity fields and aerodynamic loads are simulated, and the results are compared with flight test data. It is shown by the results that the method can accurately predict the unsteady aerodynamic rotor loads in steady flight by capturing its variational characteristics along blade azimuthal locations, and it is still applicable for high speed flight.
Representation of complex geological velocity model based on level set method
ZHANG Jianxing, YANG Qin, MENG Xianhai, LI Jigang
2016, 42(2): 303-309. doi: 10.13700/j.bh.1001-5965.2015.0106
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The difficulties in the expression of geological velocity model are the accurate description of complex geological phenomena and the effective support for the forward and inverse applications. We presented a novel representation method for describing velocity models. Velocity discontinuity was embedded into model in the form of zero-value contour of an implicit function. Multi-copy strategy was to properly handle the contradictory interpolation of velocity value at the boundary of discontinuities. The representation method can be applied to describe very complicated velocity models such as the faulted interface with non-manifold nature and multiple value surfaces. In applications based on the ray theory, signed distance field and velocity discontinuity binary tree enable fast access to velocity information of arbitrary point and easy detection of ray-interface intersection. The model can make the ray propagate positively and honor Snell's law strictly when facing velocity interface and thus improve the accuracy of ray path. Two groups of ray tracing examples verify the effectiveness of the method.
Object detection and segmentation algorithm in complex dynamic scene
XU Bing, NIU Yanxiong, LYU Jianming
2016, 42(2): 310-317. doi: 10.13700/j.bh.1001-5965.2015.0113
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In complex conditions of dynamic scenes, it is difficult to detect and segment objects accurately in image sequence. According to the image characteristics of the object in complex conditions, we propose an object detection and segmentation model which was fused with scale invariant feature transform (SIFT) Flow characteristics in dynamic scene. Through analyzing the advantages of the movement characteristic information by SIFT Flow, and combining the color and brightness information in Commission Internationale de L'Eclairage (CIE) Lab, we establish a four-dimensional vector space. We utilize the improved multi-scale center-surround comparison method to generate salient map in each channel and fuse by linear superposition, then establish the dynamic scene saliency object model in image sequence. Finally, mean-shift clustering algorithm and morphology are used to achieve object segmentation accurately. Experimental results indicate that the proposed method can segment more complete object region than the traditional method in complex dynamic scenes and aerial video. And it also has good robustness and high segmentation accuracy.
Tensile performances of mechanically fastened repairs of composite laminates
NIE Hengchang, TAN Riming, GUO Xia, GUAN Zhidong
2016, 42(2): 318-327. doi: 10.13700/j.bh.1001-5965.2015.0116
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Composite laminates with a damage hole, whose strength will reduce by about 55% under tensile loads, need to be repaired in order to recover their mechanical properties and meet the usage requirements. Mechanically fastened repair projects of composite laminates with a circular hole were designed and the repair effects were evaluated by tensile tests. Finite element models were established according to test condition, from which the effects of different repair projects on the failure loads, failure modes, stress distributions, and bolt load distributions were analyzed. The results of tests and finite element analysis (FEA) show that the recovery rate of failure strength of bolted repaired laminates will reach about 55%-60%. The areas beside the outermost bolt holes in the repair area of the laminates mainly produce stress concentration. The final failure mode of the laminates is breaking along the outermost bolt holes in the repair area. Methods such as double patch repair, adding fastened bolts, using a metal patch and increasing the thickness of patch properly can reduce stress concentration, improve bolt load distributions and enhance the recovery rate of structural failure strength.
Gene backup number selection method for embryonics cell
ZHU Sai, CAI Jinyan, MENG Yafeng, PAN Gang
2016, 42(2): 328-336. doi: 10.13700/j.bh.1001-5965.2015.0122
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The existing structures of embryonics cell's genome memory were analyzed, and a reliability model was developed considering the effect of the gene backup number on self-repair process. The hardware overhead model was built depending on the implementations of genome memories. Based on the reliability model and hardware overhead model, the relationship among reliability, hardware overhead and gene backup number was analyzed, and a gene backup number selection method was proposed. The genome memory structure, gene backup number and the size of embryonics array, taking into account the system reliability and hardware overhead, can be selected with the proposed method,according to the design requirement of reliability and hardware overhead of target circuit. So the proposed method can be introduced to the engineering application. At last, the method is verified through a circuit's gene backup number selection.
Research on flying quality of unmanned helicopter
CHEN Nanyu, MENG Zhijun, HUANG Jun
2016, 42(2): 337-344. doi: 10.13700/j.bh.1001-5965.2015.0125
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Considering the growing attention for flying qualities of unmanned helicopter while with little work and poor results in this field, the basic aspects of flying quality requirements of unmanned helicopter were discussed systematically, from the view of automatic flying control, such as the definition, research contents,influencing factors, indicators and so on; meanwhile, by rational improvements based on ADS-33E, a three-dimensional frame and the corresponding evaluation criteria suited to unmanned helicopter flight quality assessment were presented. It could provide guidance for the development and evaluation of a new unmanned helicopter system, or reference for the flying quality specification of unmanned helicopter being introduced early.
Analysis on contact characterizations of new looseproof pipeline connection
LIU Yu, WANG Jianjun
2016, 42(2): 345-350. doi: 10.13700/j.bh.1001-5965.2015.0131
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The contact characterizations of new lock pipeline connection, which is used in aircraft engine, were investigated in the installation and loosening process. Firstly, the entire installation and loosening process was divided into three stages. The friction and contact pressure in the three stages were respectively deduced,and the variation of friction and contact pressure was analyzed. Secondly, the axisymmetric finite element model of pipeline connection was established, and nonlinear transient analysis was made. Finally, the displacement load was applied to the finite element model to simulate the installation and loosening process, and the variations of slippage, connection pressure, friction, and contact stresses were analyzed. Besides, the influences of different preloads on the contact stresses of pipeline connection were studied. The analysis results show that the loosening process can be divided into two stages before and after the sliding point; the contact characterizations of the two stages differ obviously. The contact characterizations of pipeline relate only to the parameters of contact surface and the value of preload, but not to the radius of pipeline, materials or any other thing. The variation of contact characterizations of the installation and loosening process can be applied to the pipeline connection designing.
Collocation interval analysis method for gust response
LYU Zheng, QIU Zhiping
2016, 42(2): 351-359. doi: 10.13700/j.bh.1001-5965.2015.0132
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Latest aircraft design advances have started to recognize the important significance of defining multiple types of uncertainty. An important issue faced in the previous aeroelastic theory is how to deal with uncertain parameters in gust and structure. We describe the governing equation of the structural response of elastic wing in atmosphere due to gust excitation. The uncertain parameters describing the gust model and the wing structure are modeled as interval sets before the unified treatment of the uncertainties. A collocation interval analysis method (CIAM) for gust response based on the first Chebyshev orthogonal polynomials, interval collocation scheme and finite element method is proposed. The formula of CIAM is derived. The method does not require the sensitivities of the objective function with respect to uncertain variables and the assumption of narrow interval is also not needed. The proposed method can be used to solve gust response problems with uncertainties. Numerical example demonstrates that CIAM gives tighter gust response bound including exact response by comparing its results with Taylor interval analysis method (TIAM), which illustrates the efficiency and significant engineering value of the proposed method.
Analysis on aerodynamic characteristics of morphing wing with flexible trailing edge
CHENG Chunxiao, LI Daochun, XIANG Jinwu, SHI Qinghua
2016, 42(2): 360-367. doi: 10.13700/j.bh.1001-5965.2015.0083
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The wing applying active variable camber trailing edge technology can improve aircraft's aerodynamic performance, and the study of aerodynamic characteristics is of great significance to the design of the morphing wing. Choosing the 2D variable camber wing with flexible trailing edge as the object of study, the compressible Navier-Stokes equation and Spalart-Allmaras (S-A) turbulence model were applied to investigate the aerodynamics of morphing wing numerically by using the software Fluent. Aerodynamic characteristics were studied from the perspective of pressure distribution, flow field structure and the deformation mode. The numerical results show that the morphing wing has almost the same slope of lift curve and maximum lift coefficient with the conventional wing with simple flap, but has lower stall angle of attack. It has higher lift coefficient, lift-to-drag ratio, and higher nose-down pitching moment coefficient than conventional wing before the occurrence of stall. When flexible trailing edge deflects downward to a special angle, trailing edge vortex is suppressed to expand forward. The lift coefficient slowly rises after the stall, which increases the range of effective angle of attack of morphing wing and leads to a good stall characteristic.
Failure mode and effects analysis method based on fuzzy TOPSIS
DU Hanheng, PENG Chong
2016, 42(2): 368-374. doi: 10.13700/j.bh.1001-5965.2015.0088
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Aiming at the defect of traditional failure mode and effects analysis (FMEA) in evaluating the effect factors of the failure mode and calculating the risk priority number, a FMEA method based on fuzzy technique for order preference by similarity to ideal solution (TOPSIS) is proposed. This method uses fuzzy belief structure to express the evaluation of the effect factors, and adopts defuzzification and the weighted average to establish the clear belief matrix. Moreover, considering the importance of the weights of the effect factors on analysis result, the weights are determined by the combination the subjective weighting method and the objective weighting method, then the weighted normalized matrix can be constructed, and the risk level of each failure mode is ranked in the order of the relative closeness. An example is taken to validate feasibility and effectiveness of the method.
Group-target signal separation based on time-frequency enhancement and total variation
LI Jingqing, FENG Cunqian, ZHANG Dong, CHEN Rong
2016, 42(2): 375-382. doi: 10.13700/j.bh.1001-5965.2015.0110
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To solve the problems of weak time-frequency orthogonality and the complexity of separation on group-target echo acquired by low-resolution radar, a group-target signal separation algorithm based on total variation (TV) is proposed as a precondition of time-frequency enhancement. The necessity of time-frequency enhancement is indicated by analyzing the sparsity of group-target signal on the basis of rotating model. According to the differences between the micro-motion periods of different sub-targets, the multi-view group-target echoes are respectively enhanced in time-frequency domain by two-way delay processing. Ultimately, on the basis of the distribution property of energy region for group-target echo, the group-target echo is separated with high fidelity via the regional TV fusion method in conjunction with principal component analysis. The simulation results validate that the algorithm can be used to separate and extract weak signals from some strong signals more easily when the sampling rate is lower. And the fusion resolution of the proposed algorithm is also superior to the fusion method based on TV norm.
Evaluation and analysis method of aviation seat crashworthiness
LI Mengxiao, XIANG Jinwu, REN Yiru, ZHANG Xiaoyu, LUO Zhangping
2016, 42(2): 383-390. doi: 10.13700/j.bh.1001-5965.2015.0086
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In order to research the structural response characteristics of an aviation seat under crash scenarios, an evaluation and analytical method of aviation seat crashworthiness was proposed for a seat/occupant system. A finite element model of the seat was established based on actual seat geometry and reasonable simplifying assumptions, then the seat model was coupled with a 50th Hybrid Ⅲ multi-rigid-body dummy model. A crashworthiness simulation of this seat/occupant system was carried out according to airworthiness regulations which define dynamic impact test methods and qualification requirements for crew seats in general aviation aircraft in consideration of the cabin floor deformation. Seat deformations and energy-absorption, as well as occupant injury indicators under typical loading conditions were obtained. The results show that the seat/occupant system suffers more serious damage under forward and lateral loading, and the plastic deformation of the front seat beams increases when the backrest adjustment mechanism is too rigid. Cabin floor deformation aggravates seat structure damage. Compared with pitch deformation, roll deformation of the cabin floor causes greater damage. Modifications for the seat structure are proposed to improve its crashworthiness.
Thermal-structure coupling analysis and research of MSCMG
HAN Weitao, LIU Gang, SUN Jinji, TANG Jiqiang
2016, 42(2): 391-399. doi: 10.13700/j.bh.1001-5965.2015.0097
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As a novel actuator for spacecraft attitude maneuver, magnetically suspended control moment gyroscope (MSCMG) operates in a high vacuum with high speed rotor suspended, leading to poor dissipating heat conditions and high system temperature, which result in the larger thermal stress and weaken the structure strength of MSCMG. To reduce the influence of temperature field on the strength of MSCMG components and improve the reliability of MSCMG structure, finite element method is applied to calculate the temperature field of MSCMG under the working state and analyze the stress distribution in MSCMG components based on the temperature field to understand the influence of temperature field on the mechanical properties of MSCMG components. Moreover, the thermal network model of MSCMG is established. The heat flux path and the factors influencing temperature are analyzed according to the thermal network model and the thermal network equations. And then, the optimization measurements are put forward. After optimization, the maximum temperature of stator assembly decreases from 66.5℃ to 49℃ and that of rotor assembly decreases from 91.7℃ to 76.9℃.In addition, the safety factor of stator assembly increases from 1.52 to 1.73 (increases by 13.8%) and that of rotor assembly increases from 1.32 to 1.56 (increases by 18.2%).
Effects of Ni particles with different morphologies on electro-optical properties of nematic liquid crystal
XU Lihong, ZHAO Dongyu, LIU Bin, ZHOU Wei, GUO Lin
2016, 42(2): 400-405. doi: 10.13700/j.bh.1001-5965.2015.0126
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Twisted nematic (TN) liquid crystal display mode cells doped with different Ni particles were prepared, such as Ni bowls-like particles, Ni flowers particles and Ni spheres particles. The effects of different Ni particles on the threshold voltage, saturation voltage, contrast ratio and response time of nematic liquid crystal (NLC) display mode cells were investigated with a liquid crystal display parameters tester. It is found that the addition of Ni particles with different morphologies decrease the threshold voltage and the saturation voltage, increase the cantrast ratio and reduce the response times significantly. Especially, the TN cells doped with the Ni bowls-like particles have the best properties, the driving voltage could be reduced by 13.77%, the contrast ratio increases by 35.55% and response times decreases to 9.390 ms. The experiments indicate that the different shapes, structures and surface area of Ni particles have obvious effects on the electro-optical properties of liquid crystals. The larger the surface areas and the curvature of the bowls-like shape are, the better the electro-optical properties are.
5-axis tool path smoothing to improve machine tool motion
LI Xiaodong, NING Tao, CHEN Zhitong
2016, 42(2): 406-412. doi: 10.13700/j.bh.1001-5965.2015.0138
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An optimization model of tool path smoothing in 5-axis CNC machining is built to improve the machine tool acceleration condition in the tool path corner transition motion in linear interpolation. Considering the difference of the five axis acceleration abilities, the ratio of one axis' maximal acceleration in corner transition motion and its allowed maximal acceleration is used to evaluate its acceleration condition, and the root-mean-square value of the five axis acceleration ratios is used to evaluate the machine tool acceleration condition, decreasing which can increase the stability of machine tool motion. The shortest lines method is used to build an admissible domain for tool axis tilt and yaw angles at each cutter contact point in the initial tool path in order to make the tool path respect the cusp height and no gouging constraints after smoothing. An example is given to demonstrate the feasibility of this method in improving the machine tool acceleration condition and increasing the stability of machine tool motion by smoothing the tool path.
Fractional tap-length algorithm for adaptive filters under maximum correntropy criterion
LIU Chunhui, QI Yue, DING Wenrui, ZHANG Wenqiu
2016, 42(2): 413-420. doi: 10.13700/j.bh.1001-5965.2015.0137
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Accurate estimation of the optimum tap-length for the adaptive filter provides a good balance between the steady-state performance and the complexity of the adaptive algorithm. The convergence performance of the variable tap-length least mean square (LMS) adaptive filters under the minimum mean square error (MMSE) criterion deteriorates in the non-Gaussian noise environment. A fractional tap-length (FT) algorithm for the maximum correntropy criterion (MCC) adaptive filters, named FT-MCC algorithm, is proposed to solve the above problem. The proposed algorithm is based on the concept of the optimum tap-length for the MCC adaptive filters. The difference of the correntropy between adaptive filters with different tap-lengths is used to achieve the tap-length update. Both theoretical analysis and simulation result show that the proposed algorithm has strong robustness in non-Gaussian noise environment compared with other variable tap-length LMS algorithm and the optimum tap-length can be well estimated with proper parameter selection.

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