Axisymmetric mechanical analysis of ceramic heads for total hip replacement

An axisymmetric, mechanical analysis of conical press-fit ceramic heads is performed. The head strength and its fracture modes are assessed experimentally. The stress field is examined by finite element, strain gauge and photoelastic methods. An alternative head design, characterized by a cylindrical engagement with the stem, is analysed with the same techniques and its merits are explored.     

数控设备机械结构的故障排查分析研究

数控设备机械结构的一个零件发生故障,会迅速波及到其它零件.将小世界网络引入机床本体零部件的复杂网络拓扑结构中,并建立了机械结构的故障排查模型.利用神经网络算法求解故障扩散的最佳路径,找出机械结构的薄弱环节,为故障的排查提供较好的依据.     

Multibody approach for tolerance analysis and optimization of mechanical systems

A multibody approach is suitable for tolerance analysis of mechanical systems since multibody formulation can directly consider part-level tolerance variables. In this study, procedures for performing tolerance analysis and corresponding sensitivity analysis for spatial multibody systems are proposed. First, statistical formulation for performing multibody system tolerance analysis is developed to obtain system level tolerance for given part-level tolerances. One very useful aspect of the proposed formulation is that in the process of computing system tolerance, the sensitivity of system tolerance with respect to part-level tolerances can be additionally obtained. The kinematics of spatial multibody systems has been redefined in terms of both generalized coordinates and part-level tolerance variables. Tolerances in geometry of a body are specified in terms of the variations in relative locations of joint definition points and relative distance between them. Tolerances in the joint kinematics are defined through variations in vector closure equations and orthogonality equations that are two fundamental constraint equations for most kinematic joints. To demonstrate the validity and effectiveness of the proposed tolerance analysis procedure, tolerance analysis of a spatial 4-bar mechanism and tolerance optimization are performed.     

Reliability analysis and micromechanics: A coupled approach for composite failure prediction

This work aims at associating two classical approaches for the design of composite materials: first, reliability methods that allow to account for the various uncertainties involved in the composite materials behaviour and lead to a rational estimation of their reliability level; on the other hand, micromechanics that derive macroscopic constitutive laws from micromechanical features. Such approach relies on the introduction of variabilities defined at the microscale and on the investigation of their consequences on the material macroscopic response through an homogenization scheme. Precisely, we propose here a systematic treatment of variability which involves a strong link between micro- and macroscales and provides a more exhaustive analysis of the influence of uncertainties. The paper intends to explain the main steps of such coupling and demonstrate its interests for material engineering, especially for constitutive modelling and composite materials optimization. An application case is developed throughout on the failure of unidirectional carbon fibre-reinforced composites with a comparative analysis between experimental data and simulation results.     

Shock machine for the mechanical behaviour of hip prostheses: a description of performance capabilities

The aim of this study was to describe the behaviour of a shock machine designed for testing hip prostheses. A microseparation between head and cup occurs inducing a shock of several times the body weight, leading to fracture of ceramic femoral components. Femoral heads and cups of diameter 32 mm manufactured from alumina were tested in dry and wet conditions. Implants were subjected to shocks with a load profile of 9 kN load at 2 Hz and various microseparations. Position is monitored and force is measured with two acquisition systems. The working range and the device capabilities were investigated. Only cups tested in dry conditions failed. Observations by scanning electron microscopy revealed intergranular and transgranular fractures. Two wear stripes were observed on the heads. Three‐dimensional roughness of wear stripes was measured. Since experimental results are in good agreement with retrieved femoral heads, the shocks machine reproduces the in vivo degradations. Copyright © 2011 John Wiley & Sons, Ltd.     

An approach for mechanical fault classification based on generalized discriminant analysis

To deal with pattern classification of complicated mechanical faults, an approach to multi-faults classification based on generalized discriminant analysis is presented. Compared with linear discriminant analysis (LDA), generalized discriminant analysis (GDA), one of nonlinear discriminant analysis methods, is more suitable for classifying the linear non-separable problem. The connection and difference between KPCA (Kernel Principal Component Analysis) and GDA is discussed. KPCA is good at detection of machine abnormality while GDA performs well in multi-faults classification based on the collection of historical faults symptoms. When the proposed method is applied to air compressor condition classification and gear fault classification, an excellent performance in complicated multi-faults classification is presented. __________ Translated from Journal of Vibration Engineering, 2005, 18(2) (in Chinese)     

机械故障诊断计算机辅助铁谱分析方法研究

针对传统的铁谱分析方法主要依靠具有丰富经验的专业人员目测,分析结果客观性差、准确性低等不足,进行了计算机辅助铁谱分析方法研究,开发了铁谱图像智能识别系统.该系统能够快速、准确地对磨屑种类、形状以及粒度进行分析与识别,大大提高了分析的效率和准确性.系统现已应用于南京扬子石化公司,经使用达到了预期的目的,取得了良好的效果.     

对一起起重机保养事故的分析

1事故经过 某机械工程公司对一塔式履带起重机进行保养,连接钢丝绳的U型绳卡压卡突然断裂,由于副臂自重作用,之前松弛后叠放在地面的钢丝绳迅速被回抽,造成处于钢丝绳圈内作业的保养人员卷起后被抛甩落机身亡。     

Brake torque analysis of fully mechanical parking brake system: Theoretical and experimental approach

The effect of the drum brake temperature reduction on the clamping force of the parking brake system has not been well addressed despite the fact that it may result in vehicle roll away. In view to this, a parking brake model that takes into account the temperature reduction of the drum brake has to be developed and more importantly, it must comply with the applicable standards or regulations such as Federal Motor Vehicle Safety Standard (FMVSS) 135. This paper develops a one dimensional (1D) model of leading-trailing drum-type parking brake model. This brake model is then verified with experiments carried out on a test bench that has been verified with the hand brake system in the vehicle. The results from the experiments show a good correlation with the predicted results from the brake model. It is also found that the existing parking brake design meets the standard requirements. Another finding is that the brake torque slightly increases as the drum temperature increases. With the verified brake model, parametric studies can be carried out as one of the tools during the design process. From the studies, it is found that rollaway will not happen even with the maximum vehicle weight and friction coefficient at drum/lining interface above 0.2.     

Analysis of a conducting crack in an electrostrictive ceramic under combined electric and mechanical loading

A conducting crack in an electrostrictive ceramic under combined electric and mechanical loading is investigated. Analysis based on linear dielectric model predicts that the surfaces of the crack are not open completely but they are contact near the crack tip. The complete solution for the crack with a contact zone in a linear electrostrictive ceramic under combined electric and mechanical loading is obtained by using the complex variable formula. The asymptotic problems for a semi-infinite crack with a partial opening zone as well as for a fully open semi-infinite crack in a nonlinear electrostrictive ceramic are analyzed in order to investigate the effect of the electrical nonlinearity on the stress intensity factor under small scale nonlinear conditions. Particular attention is devoted to a finite crack in the nonlinear electrostrictive ceramic subjected to combined electric and mechanical loading. The stress intensity factor for the finite crack under small scale nonlinear conditions is obtained from the asymptotic analysis.     

Envelope dynamic analysis: a new approach for milling process monitoring

Vibration analysis has long been used for the detection and identification of the condition of machine tools. This paper proposes a method for vibration analysis in order to monitor online the milling process quality based on synchronous envelope analysis. Adapting envelope spectral analysis to characterize the milling tool is an important contribution for qualitative and quantitative characterization of milling capacity. It is a stage in modeling the three-dimensional cutting process. To determine different parameters, to understand the phenomenon which takes place during the cutting process, and to validate the monitoring algorithm, it was necessary to build and to use a complex analysis system. An experimental protocol was designed and developed for the acquisition, processing, and analyzing the three-dimensional signal. The vibration envelope analysis is proposed to detect the cutting capacity of the tool with the optimization application of cutting parameters. This purpose is reached by a detailed dynamic study of the manufacturing system divided into two parts. The first one concerns the complete analysis of the machine, of the main spindle. A dynamic analysis method is developed to completely characterize the various components of machine tools. The second is concentrated on the cutting process to condition monitoring and diagnosis. The research is focused on fast Fourier transform optimization of vibration analysis and vibration synchronous envelope to evaluate the dynamic behavior of the machine/tool/workpiece.     

A connector-based approach to the modular formulation problem for a mechanical product

To respond to marketing competition, companies strive to provide a large variety of products to meet consumers requirements. With more choices in products, such variety brings the company closer to the consumers. However, manufacturers are facing a new challenge. The assembly and partitioning of components and subassembly are becoming increasingly more complicated, which cause not only a proliferation of subassemblies but also increases the difficulty in manufacturing. To solve this problem, modular design is a key issue.This study presents a methodology for the formulation of modules on the basis of the connector concept. Based on the information entry in the assembly network sequence proposed by Tseng and Li [12], a modular partition based on the connector concept is explored. Moreover, the problem of assigning components after partitioning and the evaluation of the partitioning results are discussed.In this study, the definition and representation of connectors are described first. Then, the algorithm for the formulation of modules is discussed. Finally, a case study with a detailed analysis is provided to illustrate the application of the proposed methodology.     

Linear mass balance equilibration: a new approach for an old problem

Interval analyses are well known in the mathematics literature but have found few applications in control engineering. Based on the interval concept, we present here a methodology for data reconciliation and mass balance equilibration which is a very classical problem in mineral and chemical engineering. Indeed, this problem is solved with the view of inequality constraints which allows us to represent measurements by interval without particular knowledge and hypothesis about the density probability function of the measurement errors. As a main result, the paper gives a set of solutions for the reconciled data under an interval form and not only one solution as is the case with classical approaches.     

The third-body approach: A mechanical view of wear

The third-body approach highlights the many features which are common to different types of materials in different types of rubbing contacts. It suggests that a picture which is globally coherent from a mechanical point of view, in that it obeys as a first step the laws of equilibrium and continuity, can be presented. That picture, which is strongly inspired by lubrication theory, is presented together with its many implications in both fundamentals of tribology and industrial solutions.     

起重机接触式行程限位器的故障分析

行程限位器是起重机大车（柔性组合式悬挂起重机除外）和小车（电动单梁起重机、电动悬挂起重机和柔性组合式悬挂起重机除外）行走机构应设置的1种安全防护装置。这种行程限位器主要有接触式和非接触式2种形式。接触式行程限位器比较直观,由机体、连杆和滚动碰头组成,机体内部有拉伸弹簧、触点、接线端子。在起重机大、小车运行轨道两端的极限位置上安装行程开关,并在与其相对运动的运动部件（大、小车）上安装碰块（行程开关与碰块也可以是相反安装位置）。     

A framework for automated finite element analysis with an ontology-based approach

To obtain accurate and reliable results of finite element analysis (FEA) requires a high level of expertise and the full-scale physical context information, which are bottlenecks restricting the application of achievements of FEA in industry. This paper proposes an ontology-based framework including a hierarchy transfer approach and a three-stage automated finite element analysis method to solve these problems. The hierarchy transfer approach is proposed to create different transfer formats according to the data, information, and knowledge, to carry out the integration at different levels. The knowledge found in design and FEA theories is presented by ontology in order to uniformly describe the physical phenomenon with the same semantic meanings. This involves the development of a shared design and FEA ontology, as well as, specific application ontologies in the Ontology Web Language (OWL). The three-stage automated finite element analysis method is applied to mark up artifact in problem definition, to reuse domain knowledge in problem formulation, and to enable the automation of the FEM analysis process in the solution routine with the application of AI techniques. The feasibility and effectiveness of the framework and concepts are empirically validated by a case study.     

3D crack network analysis during a scratch test of a polymer: A combined experimental and multigrid X-FEM based numerical approach

The scratch behavior of a thermoset solid polymer exhibiting brittle behavior in tension is investigated. The surfaces are scratched and an imaging system is used to record real time photographs. The 3D crack pattern is analyzed using fluorescence confocal laser scanning microscopy. A finite element simulation is performed to determine the indenter/specimen contact conditions. They are used as input data for the 3D crack network analysis based on combined 3D localized multigrid and X-FEM/level set techniques. The computed stress distributions within the 3D cracked specimen are of great interest to understand the crack network formation observed during the experiments.     

Variation risk analysis: MEMS fabrication tolerance for a micro CMM probe

This paper describes a methodology of variation risk analysis for microsystems using analytical modelling and simulation, a key characteristic (KC) method and statistical analysis considering MEMS fabrication tolerances. This methodology is applied to an innovative design for a micro co-ordinate measuring machine (CMM) probe utilising piezoelectric actuation and sensing currently being developed at the National Physical Laboratory. Analytical modelling is used to investigate the individual effects of dimensional parameters on the sensors’ open-circuit voltage output, which is a KC of the micro CMM probe. A computer simulation is performed using the finite-element method and compared with the analytical model. The KC variation is predicted and the variation contribution of the probe manufacturing processes is presented. This KC is mainly influenced by the thickness of the piezoelectric layer associated with the composite sol gel deposition process. Variation risk analysis results can be used to implement a variation risk mitigation strategy.     

Learning motor control in the upright position: a mechanical engineering approach.

Motor control problems that result from damage to the central nervous system can make it difficult to learn functional activities. Although several therapeutic approaches attempt to address such problems there is little evidence of their efficacy. Targeted Training is a new approach, based on a biomechanical analysis of the problem, which usually relies on specifically designed equipment. This paper describes the underlying theory, the development of functional specifications, the translation of these specifications into an engineering design and the clinical results of applying the equipment. The promotion of head and trunk control provides an example of the process.     

Wear analysis of a ceramic on ceramic hip endoprosthesis

The authors have analyzed the wear of a ceramic-on-ceramic hip joint prosthesis retrieved after 25 years of use. Severe wear and flattening of the femoral head was revealed, while the acetabular component was less worn. Three wear zones can be seen on the femoral head depending on surface topography. The wear patterns of the ceramic components of the prosthetic head indicate the role of microseparation that occurs during implant functioning.