基于ANSYS的某航空零件的有限元分析

某航空零件为环型薄壁结构,在较大铣削力和夹紧力的作用下,容易发生弹性变形。结合工厂工况,采用有限元分析方法,利用经验公式计算出铣削力和夹紧力的大小并运用ANSYS软件,定量分析出工件弹性变形对加工精度的影响。同时为后续分析影响航空零件加工精度的主要因素提供理论依据。     

典型薄壁铝件的数控加工工艺

本文介绍了典型薄壁铝件的机加工方法及加工工艺方案的确定,并以薄壁铝件的数控加工工艺为例,结合自己多年的铝件加工经验,精辟地介绍了该种薄壁铝件铣削加工工序的编制,希望对工程技术人员有一定的帮助和借鉴作用。     

夹紧顺序、夹具布局和夹紧力对装夹变形影响与同步优化分析研究

为减小工件装夹变形,提高薄壁件加工精度,以薄壁零件装夹变形最小化为目标 函数,通过遗传算法和有限元方法相结合,提出夹紧顺序、装夹布局和夹紧力同步分析方法。用 该方法对一航空薄壁零件装夹进行优化分析,优化结果与经验设计及传统分析结果进行对比,有 效地降低了工件因装夹不当引起的变形,验证了夹紧顺序、夹具布局和夹紧力同步优化方法的 有效性。     

基于BP神经网络与遗传算法的航空薄壁件装夹位置选择

航空薄壁件具有厚度小、刚度低、易变形的特点。在装配过程中装夹位置选择是航空薄壁件产生变形的重要因素之一。根据实际装配工况,建立航空薄壁件装配过程有限元分析模型,通过对航空薄壁件在不同的装夹位置装配进行有限元分析,获得航空薄壁件的装夹面上表面平均变形值及神经网络训练样本。以航空薄壁件在装配过程中上表面平均变形值最小为目标,利用BP神经网络非线性映射能力构建预测模型,遗传算法优化BP神经网络训练模型,获取最佳装夹位置。使用航空薄壁件上表面所有点的平均位移来代替平均变形量,以典型航空薄壁件I型桁条为案例验证该方法的可行性。试验结果表明,BP神经网络与遗传算法预测值和有限元仿真值误差符合实际工程需要。     

基于改进混沌粒子群算法的薄壁件铣削参数优化

为提高薄壁框体结构件铣削加工精度及加工效率,提出一种薄壁框体结构件铣削加工工艺参数 优化方法。针对标准粒子群算法存在易陷入局部最优解,且不能自适应调整权重系数等问题,将混沌算法与多 目标粒子群算法结合,建立了以铣削力和单位时间材料去除率为优化目标,以铣削 4 因素为优化变量,以机床 主轴转速、进给量、铣削深度和表面粗糙度为约束条件的多目标约束优化模型。利用有限元仿真准确计算每个 优化解的加工误差,将结果及时反馈到优化算法中,进而找到最优加工工艺参数组合。以典型薄壁结构侧壁铣 削为例,分别采用试验参数、标准粒子群优化参数和本文所提算法优化结果进行仿真模拟,对仿真结果进行分 析比较,证明了该方法的有效性。     

基于UG的高速加工技术

高速加工通常指的是在合理的切削速度和较高的表面进给速度下进行的立铣加工.高速铣削主轴转速高、切削进给速度高、切削量小,但单位时间内的材料切除量却增加3～6倍.高速铣削在工件本身刚度不足(如薄壁件和细长杆件)、复杂曲面加工、难加工材料以及精密切削等加工领域中都得到了充分的应用.     

分体式叶片零件的数控加工

一、叶片结构特点 该叶片材料为30CrMnSiA,经热处理后,其强度相当大,且从零件的结构来看,后缘的导圆半径仅为0.1mm,属于典型的薄壁件,易产生加工变形,如图1所示.     

覆盖件成形缺陷的数值仿真实例分析

为研究汽车大型覆盖件成形规律,并分析其缺陷成因,介绍了板料成形动态显式有限元数值仿真技术的应用现状、基本理论及应用步骤.通过实例研究了采用有限无数值仿真技术进行覆盖件成形缺陷成因仿真分析的途径.仿真结果表明,采用数值仿真可以分析覆盖件变形规律,了解冲压过程中应力、应变分布及方向,成形极限图分布及缺陷情况,进而改进模具结构和冲压工艺,消除成形缺陷、提高产品质量.数值仿真技术是解决大型汽车覆盖件成形缺陷问题的有效工具.     

薄壁塑料件工艺规划与自动编程

本文以薄壁塑料件工艺规划和自动编程为例,结合自己多年的塑料件加工经验,介绍了该种薄壁塑料件铣削加工工序的编制,希望对工程技术人员有一定的帮助和借鉴作用。     

机床滚珠丝杠温度场热特性分析

机床加工过程生成热导致滚珠丝杠热变形,影响加工精度.以往的研究主要通过传统的解析方法计算得到滚珠丝杠热变形量,并没有考虑机床运行过程生成热引起机件热变形的影响.考虑热源的温度场影响,应用有限元分析法建立模型,并进行仿真,从而得到滚珠丝杠的热变形量和热变形的影响因素.研究结果为分析滚珠丝杠热变形对加工精度的影响和提高机床加工精度的优化设计提供了参考,为机床加工的误差补偿提供了理论依据.     

有限元分析在数控铣床热变形方面的研究

在多种热源的作用下,数控铣床产生热变形,影响工件与刀具间的相对位移,造成加工误差,从而影响零件的加工精度,因此减小热误差对提高机床的加工精度至关重要。控制机床热误差涉及到如何查找敏感点,然而找出机床敏感点是个非常棘手的问题。本文在对数控铣床热边界条件进行分析的基础上,应用有限元分析软件ANSYS,对ZK7640数控铣床进行整机热特性分析,为机床敏感点的查找提供依据,对数控机床热误差进行了定量计算,并通过实验检测验证其正确性。     

基于ANSYS的机床模态分析

振动现象是机床设计中所面临的问题之一,它能造成加工误差,影响零件的加工精度。模态分析主要用于确定结构或机器部件的振动特性。本文建立了某型立铣床床身的三维有限元模型,并利用大型有限元分析软件ANSYS进行了模态分析,得出了床身前十阶固有频率和振型。     

An error analysis approach for laminated composite plate finite element models

Errors in laminated composite plate finite element models occur at both the individual element level and at the discretization level. This paper shows that parasitic shear causes individual element errors and that its sources must be eliminated if numerically and physically correct results are to be provided by the finite element analysis. In addition, discretization errors occur when the behavior of the continuum is represented by a finite number of degrees of freedom. A procedure to estimate discretization errors in laminated composite plate finite element models and guide refinement, in order to achieve an acceptable level of accuracy, is developed. The error estimator built is based on the energy norm of the error in stress resultants.     

Lower Bounds for Eigenvalues of Elliptic Operators: By Nonconforming Finite Element Methods

The paper is to introduce a new systematic method that can produce lower bounds for eigenvalues. The main idea is to use nonconforming finite element methods. The conclusion is that if local approximation properties of nonconforming finite element spaces are better than total errors (sums of global approximation errors and consistency errors) of nonconforming finite element methods, corresponding methods will produce lower bounds for eigenvalues. More precisely, under three conditions on continuity and approximation properties of nonconforming finite element spaces we analyze abstract error estimates of approximate eigenvalues and eigenfunctions. Subsequently, we propose one more condition and prove that it is sufficient to guarantee nonconforming finite element methods to produce lower bounds for eigenvalues of symmetric elliptic operators. We show that this condition hold for most low-order nonconforming finite elements in literature. In addition, this condition provides a guidance to modify known nonconforming elements in literature and to propose new nonconforming elements. In fact, we enrich locally the Crouzeix-Raviart element such that the new element satisfies the condition; we also propose a new nonconforming element for second order elliptic operators and prove that it will yield lower bounds for eigenvalues. Finally, we prove the saturation condition for most nonconforming elements.     

Accuracy of some finite element models for arch problems

This paper presents a theoretical accuracy study of some finite element models for thin arches. As is well known, the selection of finite elements for curved members is quite a delicate problem. We obtain order estimates of errors of finite element solutions by means of the perturbation theory of mixed models and the technique of asymptotic expansion. In particular, we theoretically show that certain finite element models may suffer from the so-called locking phenomenon. Numerical results are also given to be compared with the theoretical error estimates.     

Inherited error in finite element analyses of structures

Mathematicians are quick to point out that round-off and truncation errors induced by the digital computer are only half of the manipulation errors in numerical analyses. The other half are the errors in quantizing the mathematical problem for computer solution: errors inherited for the equation solving process.This paper examines the relevance of inherited errors in structural analyses using the finite element concept and the digital computer. It illustrates error magnitudes using numerical experiments of simple structures. It constructs a theory explaining the errors for these systems. Having identified the most significant controllable computer error source, it describes a process for minimizing its contribution to the inherited error.The paper concludes that orders of magnitude between errors reported by various investigators can be explained by differences in inherited error. The most significant effect of these errors can be identified with inconsistency in problem formulation. These inconsistencies can be eliminated by exploiting the existence of rigid body states in the finite element models. Thereby, solution errors introduced by inherited errors can be reduced to intrinsic errors in parameters defining the geometry, material characteristics, and boundary conditions.     

Complementary error bounds for foolproof finite element mesh generation

The use of complementary variational principles in finite element analysis is examined. It is shown that complementary finite element solutions provide an element by element measure of the accuracy of the solution. By solving a problem repeatedly, beginning with a coarse mesh and refining those elements having the largest errors, an automatic, foolproof finite element mesh generation procedure is developed. Finite element solutions obtained by the new procedure have the property that the finest elements are concentrated in regions of greatest need while large elements are found in less important regions. A computer program which implements the new algorithm is described and examples of finite element solutions generated by the program are presented.     

An a posteriori error estimate and a comparison theorem for the nonconforming <Emphasis Type="Italic">P</Emphasis><Subscript>1</Subscript> element

A posteriori error estimates for the nonconforming P ₁ element are easily determined by the hypercircle method via Marini’s observation on the relation to the mixed method of Raviart–Thomas. Another tool is Ainsworth’s application of the hypercircle method to mixed methods. The relation on the finite element solutions is also extended to an a priori relation of the errors, and the errors of four different finite element methods can be compared.      

Transverse distribution law of airflow excitation force for SI-FLAT contactless shapometer

Aiming at the shape problems in production, the finite element model was built with the Fluent software to analyze the transverse distribution laws of airflow excitation force under different factors which affected the detection precision. For analyzing the shape errors caused by the non-uniform transverse distribution of airflow excitation force, the finite element model of strip is built with the ANSYS12.0 software. It is found in the study results that the airflow excitation forces display the same distribution laws under different rolling conditions, i.e. have an obvious attenuation at the edge of strip, which causes large shape measurement errors. For reducing shape errors, the compensation project is put forward, and it gives a good foundation for improving the detection precision.     

Dimensional and geometrical errors of three-axis CNC milling machines in a virtual machining system

Virtual machining systems are applying computers and different types of software in manufacturing and production in order to simulate and model errors of real environment in virtual reality systems. Many errors of CNC machine tools have an effect on the accuracy and repeatability of part manufacturing. Some of these errors can be reduced by controlling the machining process and environmental parameters. However geometrical errors which have a big portion of total error need more attention. In this paper a virtual machining system which simulates the dimensional and geometrical errors of real three-axis milling machining operations is described. The system can read the machining codes of parts and enforce 21 errors associated with linear and rotational motion axes in order to generate new codes to represent the actual machining operation. In order to validate the system free form profiles and surfaces of virtual and real machined parts are compared in order to present the reliability and accuracy of the software.