Visualization and interaction of finite element analysis in augmented reality

In this paper, augmented reality (AR) is used to enhance the visualization and interaction of finite element analysis (FEA) of structures. An integrated simulation system is proposed which acquires input data using sensors and uses AR technology to visualize FEA results in the real world. A number of intuitive interaction methods have been devised and implemented in this system. The user can perform real-time FEA simulation to investigate structural behavior under different loading conditions either through manipulating virtual loads or creating different loading conditions. Exploration of FEA results is enhanced through natural interfaces for manipulating, slicing and clipping the result data. Moreover, the user can modify the FE models of the structures through simplified operations for different purposes, e.g., adding structural members for stiffening and performing local mesh refinement. The modified model can be re-analyzed automatically. A prototype system has been built and a case study has been implemented to demonstrate the innovative interaction methods and evaluate the system performance.     

管道J型铺设参数和安装特性的有限元仿真

为提高海洋工程作业效率,应对海上多变的环境条件,针对管道J型铺设建立包括作业船、管线和海床在内的有限元仿真模型并实现三者之间的相互作用.开展静态和动态分析,完成关键作业参数选取和管线的结构完整性评估.利用静态分析得到不同残余张力下管线的铺设姿态和等效应力分布,用于指导海上工程作业,提高作业效率;采用动态分析方法评估环境条件对工程作业过程的影响.J型铺设安装过程的有限元仿真可为保证管线铺设安全可靠地执行、降低海洋工程作业的风险提供参考.     

Real-time finite element structural analysis in augmented reality

Conventional finite element analysis (FEA) is usually carried out in offsite and virtual environments, i.e., computer-generated graphics, which does not promote a user’s perception and interaction, and limits its applications. With the purpose of enhancing structural analysis with augmented reality (AR) technologies, the paper presents a system which integrates sensor measurement and real-time FEA simulation into an AR-based environment. By incorporating scientific visualization technologies, this system superimposes FEA results directly on real-world objects, and provides intuitive interfaces for enhanced data exploration. A wireless sensor network has been integrated into the system to acquire spatially distributed loads, and a method to register the sensors onsite has been developed. Real-time FEA methods are employed to generate fast solutions in response to load variations. As a case study, this system is applied to monitor the stresses of a step ladder under actual loading conditions. The relationships among accuracy, mesh resolution and frame rate are investigated.     

基于动力学仿真的系留气球鼻锥有限元分析

针对系留气球进行了动力学仿真分析,在此基础上对一种用于固定球体的新型鼻锥结构进行了结构有限元分析,以确定其强度与刚度.首先采用计算流体力学CFD求得特定风速下系留气球所受的气动力,随后通过多体动力学软件Adams进行动力学仿真分析,确定作用在鼻锥上载荷的大小,并以此作为有限元分析的载荷边界条件;然后采用有限元分析的方法对鼻锥结构进行静力学和动力学分析;最后确定极限风速下艇首与鼻锥连接处的变形、载荷及应力情况.通过分析,为新型鼻锥结构进一步的设计改进与优化提供了参考依据.     

Predicting uncertain behavior of industrial system using FM—A practical case

As such the reliability of system is affected by many factors such as design, manufacturing, installation, commissioning, operation and maintenance. Consequently it may be extremely difficult if not impossible to model, analyze and predict the failure behavior of system.To this effect, the authors presented a structured framework which makes use of fuzzy methodology (FM), an approximate reasoning tool to deal with the imprecise, uncertain and subjective information related to system performance. The component related objective events are modeled with the help of the Petri net model of the system. Various parameters of managerial importance such as repair time, failure rate, mean time between failures, availability and expected number of failures are computed to quantify the uncertain behavior of system. Further, to improve upon the reliability characteristics of the system, in-depth qualitative analysis of unit is carried out using failure mode and effect analysis (FMEA) by listing all possible failure modes and their causes. A decision support system based on fuzzy set theory is developed to counter the limitations of traditional FMEA. The framework has been applied to model and analyze a real complex industrial system from paper mill.     

Performance Evaluation Criterion for Characterizing Video-Surveillance Systems

In the last decade, video surveillance systems have been developed to guard remote environments in order to detect and prevent dangerous situations. In general, such systems are very complex and their performances rely strongly on the values taken on by the parameters regulating the behavior of surveillance algorithms. This makes it difficult to compare performances to select the most suitable system for the problem considered. Moreover, parameters are set during the installation phase, but a good selection requires time and experience. In this paper, we present an evaluation method for characterizing video-surveillance systems in order to provide an easy way of system installation. The proposed procedure is based on the definition of Receiver Operating Characteristic (ROC) curves traced for different parameter sets and for different system working conditions. Examples are given that concern an indoor video-based surveillance system for detecting, recognizing and tracking moving objects; the system has been characterized and evaluated for different scenarios. Results prove the validation of the proposed evaluation procedure though a comparison of the performances obtained in a laboratory with the ones achieved in real working environments, after system installation following the guidelines provided by the proposed methodology.     

Design and analysis of a reconfigurable discrete pin tooling system for molding of three-dimensional free-form objects

This paper presents the design and analysis of a new reconfigurable tooling for the fabrication of three-dimensional (3D) free-form objects. The proposed reconfigurable tooling system comprises a set of matrices of a closely stacked discrete elements (i.e., pins) arranged to form a cavity in which a free-form object can be molded. By reconfiguring the pins, a single tool can be used in the place of multiple tools to produce different parts with the involvement of much lesser time and cost. The structural behavior of a reconfigurable mold tool under process conditions of thermoplastic molding is studied using a finite element method (FEM) based methodology. Various factors that would affect the tool behavior are identified and their effects are analyzed to optimally design a reconfigurable mold tool for a given set of process conditions. A prototype, open reconfigurable mold tool is developed to present the feasibility of the proposed tooling system. Several case studies and sample parts are also presented in this paper.     

复杂分布仿真系统桥接方案性能评价研究

复杂分布仿真系统往往需要基于异构网络环境互连的方法搭建,以满足不同仿真实体间通信的实时性要求,这时系统的瓶颈变为不同网络环境的桥接模块;目前有多种桥接方案,但实际搭建系统时,要求在有限的时间和资源条件下预测系统性能;针对现有性能评估方法不能很好提供类似评价的特点,提出了一种网关互连方案的性能评估方法;该方法结合专门设计的实验模型及以经典排队论为基础的数学模型,使得协议的性能分析既基于真实实验数据,又具有预测能力;最后在实际的科研相目中结合项目特点使用该评价模型为依据进行网关方案选型,通过应用结果表明,该方法是可行的。     

Using three-dimensional finite element analysis in time domain to model railway-induced ground vibrations

For the prediction of ground vibrations generated by railway traffic, finite element analysis (FEA) appears as a competitive alternative to simulation tools based on the boundary element method: it is largely used in industry and does not suffer any limitation regarding soil geometry or material properties. However, boundary conditions must be properly defined along the domain border so as to mimic the effect of infinity for ground wave propagation. This paper presents a full three-dimensional FEA for the prediction of railway ground-borne vibrations. Non-reflecting boundaries are compared to fixed and free boundary conditions, especially concerning their ability to model the soil wave propagation and reflection. Investigations with commercial FEA software ABAQUS are presented also, with the development of an external meshing tool, so as to automatically define the infinite elements at the model boundary. Considering that ground wave propagation is a transient problem, the problem is formulated in the time domain. The influence of the domain dimension and of the element size is analysed and rules are established to optimise accuracy and computational burden. As an example, the structural response of a building is simulated, considering homogeneous or layered soil, during the passage of a tram at constant speed.     

Docking at pool and sea by using active marker in turbid and day/night environment

Nowadays, autonomous underwater vehicle (AUV) is playing an important role in human society in different applications such as inspection of underwater structures (dams, bridges). It has been desired to develop AUVs that can work in a sea with a long period of time for the purpose of retrieving methane hydrate, or rare metal, and so on. To achieve such AUVs, the automatic recharging capability of AUVs under the sea is indispensable and it requires AUVs to dock itself to recharging station autonomously. Therefore, we have developed a stereo-vision-based docking methodology for underwater battery recharging to enable the AUV to continue operations without returning surface vehicle for recharging. Since underwater battery recharging units are supposed to be installed in a deep sea, the deep-sea docking experiments cannot avoid turbidity and low-light environment. In this study, the proposed system with a newly designed active—meaning self-lighting—3D marker has been developed to improve the visibility of the marker from an underwater vehicle, especially in turbid water. Experiments to verify the robustness of the proposed docking approach have been conducted in a simulated pool where the lighting conditions change from day to night. Furthermore, sea docking experiment has also been executed to verify the practicality of the active marker. The experimental results have confirmed the effectiveness of the proposed docking system against turbidity and illumination variation.     

An object-oriented framework for finite element pavement analysis

In this study, we developed an object-oriented (OO) framework with interactive graphics to assist pavement studies using finite element analysis (FEA). FEA has been proven to be effective in studying various pavement failure problems; however, it is time consuming and error prone to manually generate the load sequences where non-regular tire footprints, non-uniform tire-pavement contact stresses, and transverse wheel wander distributions are used. After FEA, extracting the deformations for failure analysis is necessary but tedious. The OO framework developed in this study handles the preprocessing and postprocessing tasks for the FEA of pavements. It has a graphical user interface and is platform independent. It was successfully used in developing a new criterion for characterizing pavement failures that involved approximately four hundred different FEA simulations.     

基于昆虫毛状感触器的微型流速传感器有限元模拟分析

给出一种基于昆虫毛状感触器的微型仿生传感器,用以测量低速气体流动.分析昆虫毛状感触器和这种微型仿生传感器的工作机理.采用ANSYS的多场耦合模型进行模拟以充分考虑到固体场与流体场的相互作用,提出有限元分析中流体模型的边界条件和尺寸选择的标准.有限元模拟证实,低速气体的流速与应变片测量的薄膜根部应力在微尺度范围内有良好线性关系.而且简单分析和初步探讨基于悬臂梁的薄膜的尺寸对于根部应变的影响.     

Shape optimization of heavy load carrying components for structural performance and manufacturing cost

This paper addresses the trade-off between structural performance and manufacturing cost of heavy load carrying components by incorporating virtual machining (VM) technique in computer-aided design (CAD)-based shape optimization problem. A structural shape optimization problem is set up to minimize total cost, subject to the limits on structural performance measures. For every design iteration, finite element analysis (FEA) is conducted to evaluate structural performance, and VM is employed to ascertain machinability and estimate machining time. Design sensitivity coefficients of objective function and constraints are computed and supplied to the optimization algorithm. Based on the gradients, the algorithm determines design changes, which are used to update FEA and VM models. The process is repeated until specified convergence criterion is satisfied. Application programs developed to integrate commercially available CAD/CAM/FEA/Design optimization tools enable implementation in virtual environment and facilitate automation. The application programs can be reused for similar design problems provided that the same set of tools is used.     

机械结构多机分布式优化的集成策略研究

为了解决复杂机械结构的优化集成问题,提出了跨广义优化平台与有限元分析平台的多计算机分布式优化的集成策略及系统总体框架,详细探讨了实现集成的一些关键技术,包括在有限元前处理中的边界载荷条件的自动施加、网格自动修改、数据通讯问题、远程控制技术等,提出了相应的解决方案,并已有效地用于求解液压挖掘机的广义优化模型。     

Numerical analysis of the early age behavior of concrete structures with a hydration based microplane model

To simulate the early age behavior of concrete structures composed of young concrete, a finite element analysis (FEA) was implemented with the hydration based microplane model. Structural behaviors were investigated with concrete age for a massive concrete wall and slab. From FEA, it was found that surface cracking at early age occurred via different crack driving mechanisms. In the case of combined hydration heat and shrinkage, later surface cracking was produced by differential drying shrinkage. A numerical analysis performed with the hydration based microplane model successfully simulated the typical cracking patterns due to edge restraint in the concrete slab.     

基于工程管理的南海地质数据库

从南海地质数据资源、工程实例出发,结合高级语言设计和开发了基于工程管理的南海地质信息数据库系统.该系统设计实现了南海地质信息数据共享、数据融合、数据分析,简单快捷的结合到工程实例中,并应用ADO、DAO、OLE等计算机技术实现的数据资源快速导入、导出便于工程应用的目的.对工程中土的性质做详细的介绍,包括随深度的下降有效重度、抗剪强度、单位表面摩阻力、单位桩端阻力的变化情况.可以按层号、深度、土体性质等不同的条件进行查找.汇总功能可以绘制曲线,比较同一工程土体参数和不同工程之间的参数等,对工程设计和施工进行指导.     

动态海缆机械性能有限元分析

为探究动态海缆在剧烈交变环境载荷下的疲劳寿命,基于环境载荷响应,开展动态海缆系统的整体分析。基于有限元方法,研究海水中悬浮的动态海缆在服役过程中承受的极端载荷,分析破断力和侧压力工况,提取关键部位的应力、应变分布并进行校核。研究结果可为动态海缆材料选型、结构优化以及疲劳分析和测试提供理论依据。     

Design of mirror system in digital single lens reflex camera for high-speed continuous shooting

This research explores anti-vibration mechanisms for mirror systems in DSLR cameras through numerical methods such as explicit/implicit finite element analysis (FEA) and multi-body dynamics (MBD). Kinematic design of the movable mirrors, which guide incoming light, is carried out through MBD, and a two-dimensional mirror system geometry that increase the mirror area while allowing fast swing-up speeds can be obtained. The dynamic behaviors of mirror systems are predicted via explicit FEM and verified with modal analysis using implicit FEM. In addition, a prototype based on FEA results has been manufactured, and improved anti-vibration performance is confirmed via measurements of the dynamic behavior of the mirror system.     

3-D image measurement of the sea for disaster prevention

To reduce the loss of human life in disasters, we have developed an early warning system for typhoons and tsunamis. The system is designed to monitor the change of the sea level from a distance of 20 km. And it can alert a coming tsunami 20 min before reaching the coast. Now, GPS Buoys and observation networks are used to forecast tsunami. However, the GPS buoys are not conducive to monitoring wide ranges of the sea. The observation networks have the disadvantages of high installation costs and difficult maintenance. In this paper, a measurement system of long distance sea level height for disaster prevention has been constructed based on a 3-D image measurement technique. First, to monitor a wide range of the sea surface, this system utilizes the pan and tilt stages and angle sensors to rotate the cameras. To improve the accuracy of long distance 3-D image measurement, a long-distance calibration method of camera system has been proposed based on the scale poles. In addition, all the equipment can be put in one place so it is very convenient to maintain. In this experiment, a dynamic threshold method is proposed in blocks to extract the waves automatically, accompanied by a wave feature matrix matching method in two long-distance images. Finally, the average value of wave height is used as the height of sea level. As a practical use result, a comparison has been made between the measurement results and the data of Japan Meteorological Agency (JMA).