基于接触模型的球头挂环仿真分析与优化方法研究

球头挂环作为输电线路的关键部件,起到保证输电线路安全运行的作用。为了对 球头挂环进行优化研究,在顺风向水平力作用下,基于Abaqus 有限元软件对球头挂环进行了 非线性静力仿真分析,通过建立2 种不同型号的球头挂环接触模型,设置不同的网格密度、接 触面宽度,接触类型采用面-面接触,讨论了球头挂环尺寸、网格密度和接触面宽度对最大应力 的影响规律。计算结果表明,2 种型号球头挂环在不同网格密度下的接触宽度与最大应力变化 规律基本相同,最大应力值随着接触面宽度的增大而逐渐减小,可分为急速下降区、缓慢下降 区、平稳区3 个阶段。平稳区的最大应力及波动幅度均较小,可作为理想的球头挂环接触面宽 度,其可为今后球头挂环的优化设计提供理论指导依据。     

±800kV直流换流站阀厅典型金具表面电场分布特性

换流站承担交直流间相互转换的工作,是特高压直流输电工程中的核心。换流站阀厅内各种设备的连接处容易出现电场畸变需要加装球型金具进行屏蔽,设计时会针对换流站内典型金具进行表面电场的计算校验,确保金具表面电场强度满足工程设计要求的控制场强,因此精确计算金具表面电场分布具有重要意义。本文建立了青海电科院高压大厅全尺寸三维模型,计算得到了不同间隙距离下不同类型金具表面电场分布特性,结果表明:不同电极类型下,金具表面电场强度分布不同;同一间隙类型下,间隙距离越小,金具表面最大场强越大;同一间隙类型下施加电压在不同金具上,金具表面最大场强范围也不同。     

基于COMSOL的低熔点合金电连接头力学性能分析

针对输配电线路电连接头异常发热导致能源损耗甚至引发供电事故的问题,分析了影响电连接件异常发热的原因。本文以输配电线路接续金具中典型实用的耐张线夹为研究对象,低熔点合金材料为接触界面添加材料,采用三维建模对其接触部分进行建模,通过COMSOL有限元分析软件对连接试样进行结构力学和固流耦合仿真分析,对比研究接续金具耐张线夹试样界面结构改变前后受张力的情况。仿真结果表明:在添加低熔点合金前后输配电线路接续金具受到的导线的张力变化很小,满足电力金具的机械性能。     

基于外积FLNN的非线性系统辨识

函数型连接神经网络通过对输入模式预先进行非线性扩展,增强了输入信号的模式表达,从而大大简化网络结构,降低计算复杂度。本文提出一种外积扩展型连接神经网络,用于辨识幂函数非线性系统,并与MLP和CFLNN网络对比,仿真结果表明,外积型辨识幂函数非线性系统结构简单、计算量低、性能最优。     

京沪高铁弓网系统动态接触仿真及预紧力优化

弓网接触状态直接影响电气化列车的受流性能,良好的弓网接触是高速列车安全运行的重要保证.采用Marc有限元软件及其子程序实现吊弦刚度的非线性特性模拟,并建立弓网动态接触的有限元模型,通过合理的单元类型的选用以及边界条件的定义进行仿真、分析和计算.对时速350 km/h列车和3组预紧力下的弓网接触关系进行仿真和分析,仿真计算得出较优的预紧力合理值.     

基于MFLNN的变参数非线性系统辨识

函数型连接神经网络的网络结构简单，计算复杂度低。该文提出了一种外积扩展型连接神经网络（MFLNN），用于辨识变参数非线性系统，仿真结果表明，MFLNN实现了变参数非线性系统的辨识，效果显著。     

预紧力和螺栓位置对螺栓群连接构件的影响

为研究螺栓群连接构件的力学性能,以某高速列车中较具代表性的螺栓群连接构件为研究对象,利用非线性有限元接触算法和等效外载法施加预紧力,分别对不同螺栓预紧力和不同螺栓布置位置情形下的连接构件进行仿真.通过对孔周应力的比较,得出最佳螺栓布置位置和螺栓预紧力.     

电力施工包裹导线新型软铝片的设计与开发

输电线路导线在微风作用下会产生振动,振动节点往往位于导线与金具的连接固定处。但输电线路运行中长时间的弯折和受压会使导线产生疲劳。为避免金具和导线的长期接触摩擦,开发设计一种可紧密包裹住导线的新型软铝片,可更好防护导地线受损,缓解故障电流电弧灼伤导线和金具,避免在长期风荷载、疲劳振动等不可抗力因素作用下产生金具滑移、导线断股风险,有效解决作业中铝包带缠绕松散、预绞丝护线条耗时耗力的施工工艺问题。     

销钉连接叶片固有特性分析有限元模型研究

计算销钉连接转子叶片动频需采用有限元接触技术,而非线性接触分析难度和计算量都较大,因此提出两种线性简化工程模型,将求解非线性问题转换为求解线性问题,从而大大降低了分析难度和计算量.经检验其计算结果精度可满足工程分析要求.同时对简化柔度矩阵法及面约束简化模型有限元法计算的动频结果进行了分析,对发动机叶片固有振动特性分析有帮助.     

基于模糊微分对策多机空战组内协同的U解

鉴于协商微分对策多具有强非线性和不确定性特点,为避免非线性问题等带来求解上的困难和能处理不确定信息,基于T-S模糊微分对策的思想,对非线性的基于Utilitarian解(简称U解)的协商微分对策的状态方程和性能分别进行了模糊化和二次型化,构造出面向U解的协商微分对策的模糊线性化模型,研究了协商U解模型中加权系数的确定,并进一步探讨了在模糊线性协商微分对策系统下相应于U解的控制器的设计方法.研究工作和仿真结果可以说明,相对于Nash协商解,协商理论的U解更能反映整体效果,更易于推广.     

Intelligent Fixture Design through a Hybrid System of Artificial Neural Network and Genetic Algorithm

In designing fixtures for machining operations, clamping scheme is a complex and highly nonlinear problem that entails the frictional contact between the workpiece and the clamps. Such parameters as contact area, state of contact, clamping force, wear and damage in the contact area and deformation of the component are of special interest. A viable fixture plan must include the optimum values of clamping forces. Along research efforts carried out in this area, this comprehensive problem in fixture design needs further investigation. In this study, a hybrid learning system that uses nonlinear finite element analysis (FEA) with a supportive combination of artificial neural network (ANN) and genetic algorithm (GA) is discussed. A frictional model of workpart–fixture system under cutting and clamping forces is solved through FEA. Training and querying an ANN takes advantage of the results of FEA. The ANN is required to recognize a pattern between the clamping forces and state of contact in the workpiece–fixture system and the workpiece maximum elastic deformation. Using the identified pattern, a GA-based program determines the optimum values for clamping forces that do not cause excessive deformation/stress in the component. The advantage of this work against similar studies is manifestation of exact state of contact between clamp elements and workpart. The results contribute to automation of fixture design task and computer aided process planning (CAPP).     

A contact friction algorithm including nonlinear viscoelasticity and a singular yield surface provision

A finite element solution method for two-dimensional boundary value problems involving nonlinear viscoelasticity and contact friction is presented. The simulation of ceramic composites at elevated temperatures is the motivation of coupling viscoelasticity and contact friction. Three major topics are discussed; (i) the time-integration scheme developed for coupling the interface contact friction with nonlinear viscoelasticity in the surrounding continuum, (ii) the spatial discretization of a generalized two-dimensional deformation field using finite elements, and (iii) two methodologies for treating the nonlinearities introduced by the contact friction. The implementation of the contact friction utilizes a penalty method coupled with an incremental plasticity formulation. This formulation results in a highly nonlinear problem, and many solution techniques have difficulty with convergence due to a directional sensitivity arising from the unknown slip direction in the case of three-dimensional contact friction (or the unknown slip direction for hardening or dilatant two-dimensional friction problems). This directional sensitivity is illustrated along with an algorithm which alleviates this difficulty. Also, an algorithm based upon proportional stressing is developed to eliminate problems created by a singular yield surface for idealized Coulomb friction.     

Dynamic contact model of shell for multibody system applications

In a multibody system consisting of shell structures, the contact may appear in any area of shells. It is difficult to simulate the contact of shells with large deformation because of the geometric nonlinearity of deformation and the boundary nonlinearity of contact. This study presents a rotation-free shell formulation and an extended contact discretization in multibody systems using a corotational frame. This model is different from previous formulations in the definition of the local frame and the processing of local large curvature. In order to deal with the shell contact, a unified contact discretization scheme including edge-to-edge contact for facet triangle shell elements is proposed to solve the large penetration problem. A series of numerical examples of multibody dynamics have validated the approach of the nonlinear shell model and contact treatments. Moreover, a practical application of deployment of solar cells shows the capability of the proposed formulation in solving large-scale problems of flexible multibody system with large deformation and contact.     

An experimental study of the dimple/gimbal interface in a hard disk drive

The contact of the dimple/gimbal interface in a hard disk drive was studied experimentally. Two types of dimples with different surface roughness and several types of gimbal materials were investigated. The load?Cdisplacement curves for the contact of the dimple and the gimbal exhibit hysteresis, which is related to the plastic deformation of the asperities, during the first few load/unload cycles. The roughness of dimple and gimbal samples was measured before and after load?Cunload testing using an AFM. The plasticity index was determined based on the roughness measurement. The results show that the roughness and plasticity index of the non-polished dimple decrease with the number of load/unload cycles significantly, i.e., the contact surface becomes smoother than the original surface due to plastic deformation. The roughness and plasticity index of the laser-polished dimple change slightly before and after the load?Cunload test.     

A new physical model with multilayer architecture for facial expression animation using dynamic adaptive mesh

This paper presents a new physically-based 3D facial model based on anatomical knowledge which provides high fidelity for facial expression animation while optimizing the computation. Our facial model has a multilayer biomechanical structure, incorporating a physically-based approximation to facial skin tissue, a set of anatomically-motivated facial muscle actuators, and underlying skull structure. In contrast to existing mass-spring-damper (MSD) facial models, our dynamic skin model uses the nonlinear springs to directly simulate the nonlinear visco-elastic behavior of soft tissue and a new kind of edge repulsion spring is developed to prevent collapse of the skin model. Different types of muscle models have been developed to simulate distribution of the muscle force applied on the skin due to muscle contraction. The presence of the skull advantageously constrain the skin movements, resulting in more accurate facial deformation and also guides the interactive placement of facial muscles. The governing dynamics are computed using a local semi-implicit ODE solver. In the dynamic simulation, an adaptive refinement automatically adapts the local resolution at which potential inaccuracies are detected depending on local deformation. The method, in effect, ensures the required speedup by concentrating computational time only where needed while ensuring realistic behavior within a predefined error threshold. This mechanism allows more pleasing animation results to be produced at a reduced computational cost.     

预冷器在水压试验中管板严重变形原因

为确定高压原料天然气预冷器在水压试验中严重变形的原因,利用ANSYS得到受接触约束的换热管的临界失稳载荷,并将换热管简化为非线性弹簧单元,完成预冷器在换热管失稳后的水压试验过程的数值模拟。数值结果与水压试验数据吻合良好,表明换热管的失稳是水压试验中管板严重变形的主要原因。研究成果可为改进预冷器的设计提供参考。     

Analysis of Flexible Multibody Systems with Intermittent Contacts

This paper is concerned with the dynamic analysis of flexible,nonlinear multibody systems undergoing intermittent contacts. Contact isassumed to be of finite duration, and the forces acting between thecontacting bodies which can be either rigid or deformable are explicitlycomputed during simulation. The modeling of contact consists of threeparts: a number of holonomic constraints that define the candidatecontact points on the bodies, a unilateral contact condition which istransformed into a holonomic constraint by the addition of a slackvariable, and a contact model which describes the relationship betweenthe contact force and the local deformation of the contacting bodies.This work is developed within the framework of energy preserving anddecaying time integration schemes that provide unconditional stabilityfor nonlinear, flexible multibody systems undergoing intermittentcontacts.     

Gradient Domain Mesh Deformation - A Survey

This survey reviews the recent development of gradient domain mesh deformation method. Different to other deformation methods, the gradient domain deformation method is a surface-based, variational optimization method. It directly encodes the geometric details in differential coordinates, which are also called Laplacian coordinates in literature. By preserving the Laplacian coordinates, the mesh details can be well preserved during deformation. Due to the locality of the Laplacian coordinates, the variat...     

Contact and Deformation Modeling for Interactive Environments

Contact and deformation modeling for interactive environments has seen many applications, from surgical simulation and training, to virtual prototyping, to teleoperation, etc., where both visual feedback and haptic feedback are needed. High-quality feedback demands a high level of physical realism as well as a high update rate in rendering, which are often conflicting requirements. In this paper, we present a unique approach to modeling force and deformation between a rigid body and an elastic object under complex contacts, which achieves a good compromise of reasonable physical realism and real-time update rate (at least 1 kHz). We simulate contact forces based on a nonlinear physical model. We further introduce a novel approximation of material deformation suitable for interactive environments based on applying Bernoulli-Euler bending beam theory to the simulation of elastic shape deformation. Our approach is able to simulate the contact forces exerted upon the rigid body (that can be virtually held by a user via a haptic device) not only when it forms one or more than one contact with the elastic object, but also when it moves compliantly on the surface of the elastic object, taking friction into account. Our approach is also able to simulate the global and local shape deformation of the elastic object due to contact. All the simulations can be performed in a combined update rate of over 1 kHz, which we demonstrate in several examples.     

充气梁展开仿真研究

充气展开结构的动力学仿真主要涉及柔性结构非线性接触,基于有限变形的柔性多体动力学等关键问题,以充气梁为模型给出了适合仿真的材料模型、单元算法、接触算法和充气展开算法.利用软件LS-Dyna成功模拟了折叠充气梁的展开过程,推导出充气梁的弯曲刚度与压力的关系并给出计算结果,同时报告了充气展开仿真分析中,压力过高会导致充气梁失稳的现象,接着考察了压力对充气结构固有频率的影响,最后比较了不同压力下的冲击响应.仿真结果表明该方法研究充气结构动力学是可行的,有效的.