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Description to wear debris boundaries by radar graph fractal method

Chinese Science Bulletin 2007年第16期52卷 2285-2290页

作者： liu hongtao1,2 & ge shirong1 1 institute of tribology and reliability engineering,china university of mining & technology,xuzhou 221008,china 2 College of Mechanical and Electrical engineering,china university of mining & technology,xuzhou 221116,china institute of tribology and reliability engineering China University of Mining & Technology Xuzhou China College of Mechanical and Electrical engineering China University of Mining & Technology Xuzhou China

In this paper,radar graph fractal method is introduced to describe wear debris boundaries. Research results show that it is a nice way to describe wear debris boundaries. Since the longest axis is selected as the first coordinate axis,its center point selected as the center point of the radar graph,and the co-ordinate value of wear debris boundary selected as the measure parameter,the limitations existing in Yard fractal measure method can be avoided. For any wear debris,its radar graph fractal dimension value is one and only,and as the wear debris shape changes from round to strip,the radar graph fractal dimension value also changes from low to high,showing strong uniqueness and independence. Due to the fact that the researched wear debris is gotten in different wear states,the results also prove that radar graph fractal dimension value is correlated with frictional pairs work condition and wear state. Radar graph fractal method is compared with Yard fractal measure methods,and results show that ra-dar graph fractal dimension values gotten from different wear debris have enough value grads to avoid effect of errors,and provide higher sensitivity for wear debris shape. This paper also discusses the influencing factors for radar graph fractal method. With the increase of the decomposing degree value,the radar graph fractal dimension tends to keep stable at one certain value,showing the typical characteristic of the fractal theory. All this proves that radar graph fractal method is an effective description method for wear debris boundaries.

关键词：磨粒边界雷达图表分形法

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Relations between thickness of UHMWPE’s wear debris and positive pressure of tribological system

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Chinese Science Bulletin 2008年第9期53卷 1435-1443页

作者： liu hongtao1,2,3 & ge shirong1,3 1 institute of tribology and reliability engineering, china university of mining & technology, xuzhou 221116, china 2 College of Mechanical and Electrical engineering, china university of mining & technology, xuzhou 221116, china 3 Biotribology Center, State Key Laboratory of tribology, xuzhou 221116, china institute of tribology and reliability engineering China University of Mining & Technology Xuzhou China College of Mechanical and Electrical engineering China University of Mining & Technology Xuzhou China Biotribology Center State Key Laboratory of Tribology Xuzhou China

MiaoXAM2.5X-50X Ultrahigh Precision Surface 3D Profiler is introduced to research the relations be- tween thickness of UHMWPE’s wear debris and positive pressure of tribological system. Research re- sults show that thickness of wear debris owns evident classification, and the first grade thickness math model and the second grade thickness math model are built. By the second grade thickness math model, the true force condition in the tribological system can be gotten, and the model can be used as a tool to modify simulating parameters of the tribological system, and it is an important inspecting method to the airtight system which cannot be examined in real time. The first grade thickness math model can describe the true working load and surface condition of work piece in the tribological sys- tem, and is an effective description method for the running condition of frictional pairs. The research results at different lubricating conditions testify the relations between thicknesses of wear debris and positive pressure of the tribological system. The fractal relation between maximal thickness of wear debris and positive pressure is discussed. The conceptions of the immutability principle and charac- teristic granularity of wear debris thickness are brought forward and discussed. In conclusion, as a stable tribological parameter owning mechanical theory basis, wear debris thickness will play an im- portant part in fault diagnosis, especially for the airtight system such as artificial joint.

关键词：摩擦学磨损面厚度分形数学模型

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Friction behavior of coupling motion for natural articular cartilage by reciprocating rotation

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Chinese Science Bulletin 2009年第4期54卷 576-583页

作者： QIAN ShanHua1,2,3 & ge shirong1,3 1 College of Mechano-electronic engineering, china university of mining & technology, xuzhou 221116, china 2 institute of tribology and reliability engineering, china university of mining & technology, xuzhou 221116, china 3 Biotribology Center, State Key Laboratory of tribology, xuzhou 221116, china College of Mechano-electronic engineering China University of Mining & Technology Xuzhou China institute of tribology and reliability engineering China University of Mining & Technology Xuzhou China Biotribology Center State Key Laboratory of Tribology Xuzhou China

Based on the irregular surface of natural cartilage configurations, the tribological characteristics of coupling motion between natural cartilage pairs were investigated by the variation of rotated offset and velocity. Contact displacement, contact load, friction force and coefficient of friction from natural cartilage pairs were measured by a UMT-2 testing machine. In order to obtain the steady part and wavy part, the contact load and contact displacement were decompounded by the five-point sliding average method. These results showed that the contact load was composed of steady load and wavy load. And the contact displacement was composed of cartilage deformation and surface outline. The steady load was similar to exterior load while natural cartilage deformation increased nonlinearly with the sliding time. Wavy load had the correlative coefficient 0.235 with surface outline due to the irregular surface of friction configurations. The coefficient of friction from cartilage friction configurations was less influenced by smaller magnitude in rotated parameters. A few strange summits were obtained in the area of coef-ficient of friction, and significantly related with local minimal values corresponding to the contact loads. The rotated offsets had clear impact on contact load and a slight impact on contact displacement. Larger offset produced higher wavy magnitude of the contact load. The rotated velocities played an evident role in cartilage deformation, but had a less influence on contact load. Lower velocity brought larger cartilage deformation.

关键词：软骨构造关节软骨摩擦系数软骨变形接触装

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Wettability Modification for Biosurface of Titanium Alloy by Means of Sequential Carburization

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Journal of Bionic engineering 2009年第3期6卷 219-223页

作者： Yong Luo~(1,2) Shi-rong ge~1 Zhong-min Jin~21.institute of tribology and reliability engineering,School of Material Science and engineering,china university of mining and technology,xuzhou 221008,P.R china2.institute of Medical and Biological engineering,School of Mechanical engineering,university of Leeds,Leeds LS2 9JT,UK institute of tribology and reliability engineering School of Material Science and Engineering China University of Mining and Technology Xuzhou P. R. China institute of Medical and Biological engineering School of Mechanical Engineering University of Leeds Leeds UK

Microporous titanium carbide coating was successfully synthesized on medical grade titanium alloy by using sequential *** in the surface morphology of titanium alloy occasioned by sequential carburization were characterized and the wettability characteristics were ***,the dispersion forces were calculated and *** results indicate that sequential carburization is an effective way to modify the wettability of titanium *** the carburization the surface dispersion force of titanium alloy increased from 76.5×10^(-3)J·m^(-2) to 105.5×10^(-3) J·m^(-2),with an enhancement of 37.9 %.Meanwhile the contact angle of titanium alloy decreased from 83° to 71.5°,indicating a significant improvement of wettability,which is much closer to the optimal water contact angle for cell adhesion of 70°.

关键词： biotribology wettability titanium alloy sequential carburization biosurface

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reliability analysis of ship structure system with multi-defects

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Science china(Physics,Mechanics & Astronomy) 2010年第11期53卷 2113-2124页

作者： AN Hai 1,AN WeiGang 1 & ZHAO WeiTao 2 1 School of Aerospace and Civil engineering,Harbin engineering university,Harbin 150001,china 2 School of Aeronautics and Astronautics,Shenyang institute of Aeronautical engineering,Shenyang 110034,china School of Aerospace and Civil engineering Harbin Engineering University Harbin China School of Aeronautics and Astronautics Shenyang Institute of Aeronautical Engineering Shenyang China

This paper analyzes the influence of multi-defects including the initial distortions,welding residual stresses,cracks and local dents on the ultimate strength of the plate element,and has worked out expressions of reliability calculation and sensitivity analysis of the plate *** analysis is made for the system with multi-defects plate *** mechanism,failure paths and the calculating approach to global reliability index are also worked *** plate elements with multi-defects fail,the formula of reverse node forces which affect the residual structure is deduced,so are the sensitivity expressions of the system reliability *** ensures calculating accuracy and rationality for reliability analysis,and makes it convenient to find weakness plate elements which affect the reliability of the structure ***,for the validity of the approach proposed,we take the numerical example of a ship cabin to compare and contrast the reliability and the sensitivity analysis of the structure system with multi-defects with those of the structure system with no *** approach has implications for the structure design,rational maintenance and renewing strategy.

关键词： initial distortions welding residual stresses cracks and local defects ultimate strength reverse node forces sensitivity expression reliability analysis

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A study on compressive shock wave propagation in metallic foams

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Science china(Physics,Mechanics & Astronomy) 2010年第2期53卷 279-287页

作者： WANG ZhiHua1,2,ZHANG YiFen2,REN HuiLan1 & ZHAO LongMao2 1 State Key Laboratory of Explosion Science and technology,Beijing institute of technology,Beijing 100081,china 2 institute of Applied Mechanics and Biomedical engineering,Taiyuan university of technology,Taiyuan 030024,china State Key Laboratory of Explosion Science and technology Beijing Institute of Technology Beijing China institute of Applied Mechanics and Biomedical engineering Taiyuan University of Technology Taiyuan China

Metallic foam can dissipate a large amount of energy due to its relatively long stress plateau,which makes it widely applicable in the design of structural crashworthiness. However,in some experimental studies,stress enhancement has been observed when the specimens are subjected to intense impact loads,leading to severe damage to the objects being protected. This paper studies this phenomenon on a 2D mass-spring-bar model. With the model,a constitutive relationship of metal foam and corresponding loading and unloading criteria are presented; a nonlinear kinematics equilibrium equation is derived,where an explicit integra-tion algorithm is used to calculate the characteristic of the compressive shock wave propagation within the metallic foam; the effect of heterogeneous distribution of foam microstructures on the shock wave features is also included. The results reveal that under low impact pulses,considerable energy is dissipated during the progressive collapse of foam cells,which then reduces the crush of objects. When the pulse is sufficiently high,on the other hand,stress enhancement may take place,especially in the heterogeneous foams,where high peak stresses usually occur. The characteristics of compressive shock wave propagation in the foam and the magnitude and location of the peak stress produced are strongly dependent on the mechanical properties of the foam material,amplitude and period of the pulse,as well as the homogeneity of the microstructures. This research provides valuable insight into the reliability of the metallic foams used as a protective structure.

关键词： aluminum foam heterogeneous intensive pulse loading stress enhancement

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Morphology and reaction force of toes of geckos freely moving on ceilings and walls

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Science china(Technological Sciences) 2010年第6期53卷 1688-1693页

作者： WANG ZhouYi1,2,GU WenHua1,2,WU Qiang1,2,JI AiHong1 & DAI ZhenDong1 1 institute of Bio-inspired Structure and Surface engineering,Nanjing university of Aeronautics and Astronautics,Nanjing 210016,china 2 College of Mechanical and Electrical engineering,Nanjing university of Aeronautics and Astronautics,Nanjing 210016,china institute of Bio-inspired Structure and Surface engineering Nanjing University of Aeronautics and Astronautics Nanjing China College of Mechanical and Electrical engineering Nanjing University of Aeronautics and Astronautics Nanjing China

The 3-dimensional interactions between toes of a gecko and substrates (ceilings or walls) were measured when it moves on ceilings or walls by using a 3-dimensional force measuring array,and the correspondent morphology of the gecko toes was recorded by a high speed *** study aims to understand the relationship between adhesive and shear forces generated by the toes of the gecko and the locomotion behavior when it walks on walls and *** showed that shear force is along the toe-only 12.6° and 3.1° away from the toe for wall-climbing and ceiling-crawling,respectively while the adhesion is big enough to balance the body weight and *** shear forces generated by the first and the fifth toes are in opposite directions;this redundant force increases the reliability of adhesion and stability of *** support angles of toes are equal approximately for ceiling-crawling and *** study greatly inspires the design of a gecko-like robot.

关键词： reaction force of toe morphometrics ceiling redundant force gecko-like robot

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Parameter identification theory of a complex model based on global optimization method

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Science china(Physics,Mechanics & Astronomy) 2008年第11期51卷 1722-1732页

作者： QU Jie1, JIN QuanLin2 & XU BingYe3 1 College of Automotive engineering, South china university of technology, Guangzhou 510640, china 2 Beijing Research institute of Mechanical and Electrical technology, Beijing 100083, china 3 Department of engineering Mechanics, Tsinghua university, Beijing 100084, china College of Automotive engineering South China University of Technology Guangzhou China Beijing Research institute of Mechanical and Electrical technology Beijing China Department of engineering Mechanics Tsinghua University Beijing China

With the development of computer technology and numerical simulation technology, computer aided engineering (CAE) technology has been widely applied to many fields. One of the main obstacles, which hinder the further application of CAE technology, is how to successfully identify the parameters of the selected model. An elementary framework for parameter identification of a complex model is provided in this paper. The framework includes the construction of objective function, the design of the optimization method and the evaluation of the identified results, etc. The parameter identification process is described in this framework, taking the parameter identification of the superplastic constitutive model considering grain growth for Ti-6Al-4V at 927°C as an example. The objective function is the weighted quadratic sums of the difference between the experimental and computational data for the stress-strain relationship and the grain growth relationship; the designed optimization method is a hybrid global optimization method, which is based on the feature of the objective function and incorporates the strengths of genetic algorithm (GA), the Levenberg-Marquardt algorithm and the augmented Gauss-Newton algorithm. The reliability evaluation of parameter identification result is made through the comparison between the calculated and experimental results and between the theoretical values of the parameters and the identified ones.

关键词： constitutive model parameter identification theory inverse analysis global optimization

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Hybrid microsystem with functionalized silicon substrate and PDMS sample operating microchannel: A reconfigurable microfluidics scheme

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Science china(Technological Sciences) 2010年第8期53卷 2272-2277页

作者： LEI YinHua 1 ,XIE Fei 1 ,WANG Wei 1,2 ,WANG HaiBin 3 &LI ZhiHong 1,2 1 institute of Microelectronics,Peking university,Beijing 100871,china 2National Key Laboratory of Science and technology on Micro/Nano Fabrication,Beijing 100871,china 3 No.302 Hospital,Beijing 100039,china institute of Microelectronics Peking University Beijing China National Key Laboratory of Science and technology on Micro/Nano Fabrication Beijing China No. 302 Hospital Beijing China

A hybrid microsystem with separately functioned temperature controlling substrate and sample operating fluidic microchannel was developed to demonstrate a reconfigurable microfluidics *** temperature controlling substrate integrated a micro heater and a temperature sensor by using traditional silicon-based micromechanical system(MEMS)technique,which guaranteed high performance and robust reliability for repeatable *** sample operating fluidic microchannel was prepared by poly-(dimethylsiloxane) (PDMS)based soft lithography technique,which made it cheap enough for disposable *** PDMS microchannel chip was attached to the temperature controlling substrate for reconfigurable thermal applications.A thin PDMS film was used to seal the microchannel and bridge the functionalized substrate and the sample inside the channel,which facilitated heat transferring and prevented sample contaminating the temperature controlling *** by a one dimensional thermal resistance model,the thin PDMS film was important for the present reconfiguration *** performance of this hybrid microsystem was examined,and the experimental results demonstrated that the chip system could work stably over hours with temperature variation less than *** PDMS microchannel chips were tested on one heating substrate sequentially with a maximum intra-chip temperature difference of *** extracted from serum of a chronic hepatitis B virus(HBV)patient was amplified by this hybrid microsystem and the gel electrophoresis result indicated that the present reconfigurable microfluidic scheme worked successfully.

关键词： reconfigurable microfluidics hybrid microdevice thin PDMS film

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Towards a degradation-based mechanism for adaptive overload control

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Science china(Information Sciences) 2012年第12期55卷 2708-2722页

作者： WANG ZiYou 1,2,ZHOU MingHui 1,2 & MEI Hong 1,2 1 Software institute,School of Electronics engineering and Computer Science,Peking university,Beijing 100871,china 2 Key Laboratory of High Confidence Software Technologies(Peking university),Ministry of Education,Beijing 100871,china Software institute School of Electronics Engineering and Computer Science Peking University Beijing China Ministry of Education Key Laboratory of High Confidence Software Technologies (Peking University) Beijing China

Uncontrolled overload is one of the major causes of the system's decline in reliability and performance for web *** also harms the construction of trustworthy *** paper presents a degradationbased mechanism to adaptively control overload in complex,dynamic web *** our mechanism,the bottlenecks in the application's performance are determined by internally monitoring the performance and resource utilization state of the application,which is decomposed into a set of *** locating the bottlenecks,two decision algorithms are proposed to dynamically and adaptively generate proper degradation plans without *** degrading the service which consumes critical resources and has a low priority from the perspective of business logic,the application can keep providing key services even when overload *** implement a prototype and conduct a case study on a wiki *** also evaluate our approach and demonstrate its effectiveness in simulated overload *** handling overload,we make a breakthrough in building trustworthy software in an open,dynamic and rapidly changing environment.

关键词： overload service degradation resource monitoring performance management

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