整体叶轮应力分析的一种有效方法

整体轴流叶轮、离心叶轮等是中小型航空发动机中的关键部件，其设计正朝着转速更度、重量更轻的方向发展。随着轮体重量的减轻，叶片与轮盘之间的耦合越来越紧，相互影响和作用也越来越大。这类结构的强度问题更为突出，对强度分析的要求也越来越高。为此本文提出采用壳单元与环单元耦合的方法对整体叶轮进行分析。由于此方法考虑了叶片与轮体之间的耦合关系，同时对叶片采用壳单元进行逼真模拟，对于轮体采用轴对称环单（２Ｄ）或半     

变厚度壳单元的旋转叶片振动响应分析

以一个扭型、变截面旋转叶片为研究对象,基于ANSYS有限元软件,采用变厚度的壳单元来建立了叶片的有限元模型,并与实体单元进行对比,通过二者的固有频率和固有振型,验证本建模方法的准确性。随后分析了离心力和气动力共同作用下,实体建模和壳建模叶片的振动位移和等效应力随转速的变化规律。研究结果表明,采用变厚度壳单元可以很好的模拟叶片的固有频率和振动响应,但在计算等效动应力时和实体单元存在较大的误差。研究结果可为叶片结构设计提供理论依据。     

一种可应用于板壳成形过程模拟的绝对-相对自由度壳单元

相对自由度壳单元是采用有限元法分析板壳成形过程的一种有效单元形式。它不仅可以解决采用实体单元模拟板壳成形过程所存在的问题 ,同时它与主从自由度壳单元相比还具有简单易用的特点。然而 ,目前尚未见到对该单元边界条件如何进行具体处理的方法的报道。作者的研究表明 ,该类单元应用于模拟薄壁件成形过程时尚不能直接采用置“1”法或置大数法处理其边界条件。为此 ,本文在该单元的基础上提出了一种绝对自由度和相对自由度相结合的壳单元。将该单元应用于薄壁管弯曲过程模拟的结果表明 ,它不仅继承了相对自由度壳单元的优势 ,而且可直接采用置“1”法或置大数法处理边界条件。     

可调式动叶片振动特性及动应力计算

根据可调式动叶片的结构特点，建立了叶片振动特性和动应力进行计算的有限元力学模型。采用空间单元使叶片型线部分及叶根和叶柄能准确离散并建立统一的计算方法，既解决了体单元刚度过大的问题，又避免了采用不同种类单元分别离散叶型和叶根叶柄所产生的困难。给出了某风机可调式动叶片的算例。     

失谐对叶片一轮盘结构振动特性的影响

研究了失谐对叶片一轮盘结构系统振动特性的影响。将叶片模拟为固定在轮盘上的悬臂梁模型，采用Hamilton变分原理和Galerkin方法，导出了系统的运动方程表达式。求解状态方程的特征值问题获得系统的特征向量。以一个含16个叶片的叶片一轮盘结构为例，分析了它的振动模态。结果表明，失谐会导致系统的振动模态出现局部化现象。分析了叶片的失谐量和轮盘的转速对结构振动模态局部化的影响。     

焦炭塔结构模态分析及应用

运用ANSYS软件对焦炭塔固有频率分析,分别采用了实体单元和板壳单元进行分析比较。分析结果表明,在低阶时两种单元结果相近,超过6阶以后两种方法差异明显,采用板壳单元更能准确地模拟塔体的膨胀变形。同时研究了焦炭塔的临界风速及抗震性。     

结构振动分析的板壳单元有限元模型修正

基于ＳＡＰＳ结构分析程序的板壳单元，推导结构固有振动频率对板壳单元厚度的灵敏度公式。通过改变板壳单元厚度，模拟某轻型客车动力总成中离合器壳两端螺栓连接部分的建模误差，修正了该动力总成弯曲振动分析的有限元模型。     

机匣静叶耦合振动分析的有限元建模方法研究

悬臂静子叶片连同机匣是航空发动机静子系统的典型结构.应用有限元法分析结构周向弯曲振动的模态频率和振型,分别采用实体单元建模、梁壳单元建模、质量单元取代叶片的三种建模方法建立结构的有限元模型.通过对比分析三种有限元模型的计算结果和计算规模,结构的梁壳有限元模型有较好的计算精度并减小计算规模;在分析低阶模态中用质量单元取代叶片的建模方法满足计算精度,有限元的计算规模大为减小.     

大型风力机复合材料叶片铺层设计及结构特性研究

近些年来,风力发电发展迅速,复合材料的设计与研制是风力发电的关键技术之一。基于复合层压板理论和有限元分析方法,对风力机复合材料叶片进行分析。利用ANSYS软件中壳单元模拟叶片铺层,然后对铺层叶片进行强度分析和模态分析。通过叶片质量、重心等计算值与实测值的比较,证明了所提出的铺层设计方法的合理性。分析比较了flapwise和edgewise两个方向的不同变形,为叶片铺层优化工作提供了依据。     

有限元中体壳单元的耦合问题研究

由于转动自由度的不连续,使得体单元与壳单元之间的耦合成为有限元计算中比较难以解决的问题.通常在工程实践中采用MPC(Multipoint Constraint)法.文中提出了约束体壳单元连接处共用节点的某一旋转自由度的方法.通过与MPC法的计算对比,证明了该方法在便于实现的同时,同样有着很高的精确度.这为有限元分析中体壳单元的耦合处理提供了一种很好的借鉴方法.     

Semi-analytical solution of magneto-thermo-elastic stresses for functionally graded variable thickness rotating disks

In this paper, a semi-analytical solution for magneto-thermo-elastic problem in functionally graded (FG) hollow rotating disks with variable thickness placed in uniform magnetic and thermal fields is presented. Stresses and perturbation of magnetic field vector in FG rotating disks are determined using infinitesimal theory of magneto-thermo-elasticity under plane stress conditions. The material properties except Poisson’s ratio are modeled as power-law distribution of volume fraction. The profile of disk thickness is assumed to be a parabolic function of radius. The non-dimensional distribution of temperature, displacement, stresses and perturbation of magnetic field vector throughout radius are shown. Effects of material grading index, geometry of the disk and magnetic field on the stress and displacement fields are investigated. The results of stresses and radial displacements for two different boundary conditions with and without the effect of magnetic field are compared for a FG rotating disk with concave thickness profile. It has been found that imposing a magnetic field significantly decreases tensile circumferential stresses. Therefore the fatigue life of the disk will be significantly improved by applying the magnetic field. Results of this investigation could be applied for optimum design of FG hollow rotating disks with variable thickness.     

面向敏捷制造的集成产品开发要素研究

敏捷制造被认为是２１世纪制造企业的主要发展模式。分析了敏捷制造模式下企业实施产品集成开发的若干要素,包括企业动态联盟、过程重构、ＩＰＴ组织与管理、企业信息合理化工程、信息分类编码与标准化技术等;探讨了面向敏捷制造的并行产品开发模式;提出了支持企业动态联盟集成产品开发的信息框架概念,阐述了其集成体系结构和工作原理。     

Systematic experimental based modeling of a rotary piezoelectric ultrasonic motor

In this paper, a new method for equivalent circuit modeling of a traveling wave ultrasonic motor is presented. The free stator of the motor is modeled by an equivalent circuit containing complex circuit elements. A systematic approach for identifying the elements of the equivalent circuit is suggested. The Levenberg-Marquardt parameter estimation algorithm is used to model the alteration of the admittance after placing the rotor on the stator. Thereafter, theoretical assessments and experimental measurements are used to account for the speed reduction that is caused by placing the rotor on the stator and applying the load torque. Finally, the effects of temperature changes and the resultant response of the motor are computed. Results of the experiments and measurements are used to verify and validate the precision of the new modeling method.     

Air Bearing Simulation for Bit Patterned Media

Patterned media are being considered as a promising approach for achieving storage densities beyond 1 Tb/in² on hard disks. Patterned media reduce cross talk of adjacent bits and improve thermal stability of the media. In this investigation, the flying characteristics of femto-type sliders over bit patterned media (BPM) are investigated. The discrete bits of the disk are modeled as isolated conical protrusions on the disk surface.     

压气机轮盘简化结构强度的数值仿真分析

背景:压气机轮盘是发动机的重要组件,工作环境的应力条件复杂,其结构性能对发动机工作将产生很大的影响。目的:针对发动机轮盘进行受力分析,有利于进行轮盘结构优化设计,进而提高发动机推重比。方法:本文采用理论分析与有限元仿真相结合,基于对称假设下的轮盘简化结构强度给出径向与周向最大应力的理论解。同时,运用有限元软件ANSYS获得对应的数值仿真解。结论:经理论解与仿真解对比分析表明,本文提供的方法可用于压气机轮盘简化结构强度的求解分析。     

A Lagrangian-extended finite-element method in modeling large-plasticity deformations and contact problems

In this paper, a Lagrangian-extended finite-element (FE) method is presented in modeling large-plasticity deformations and contact problems. The technique is used to model arbitrary interfaces in two-dimensional (2D)/three-dimensional (3D) large deformations. The material interfaces are represented independent of the FE mesh and the process is accomplished by integrating enriched elements with a larger number of Gauss points, whose positions are fixed in the element. The large elasto-plastic deformation formulation is employed within the eXtended Finite-Element Method (X-FEM) framework to simulate the nonlinear behavior of materials. The interface between two bodies is modeled by using the X-FEM technique and applying modified level set and Heaviside enrichment functions. Finally, several numerical examples of arbitrary material interfaces are modeled to demonstrate the efficiency of the Lagrangian X-FEM technique in large deformation of plasticity and contact problems.     

Effects of gradient on stress distribution in rotating functionally graded solid disks

This paper presents the elastic analysis of a rotating sandwich solid disk composed of three-layered perfectly-bonded composites. The center and outer regions of the solid disk are two homogeneous isotropic media, and the middle region is a transition zone made of functionally graded materials (FGM). Two cases are considered. One is on FGM with power-law gradient. For this case, explicit expressions for full elastic fields are derived. The other is on FGM with any radial nonhomogeneity, for which an analytic approach is proposed to reduce the problem into a Fredholm integral equation. The validity of the latter method is ensured by comparing numerical results of the elastic fields with the exact ones for the case of power-law gradient. For a general case, the current study presents the influences of the gradient, width variation of the FGM, and rotational velocity on the distribution of the radial and hoop stresses for a rotating composite disk made of aluminum and zirconia. The method presented in this paper may help engineering designers in choosing appropriate gradients and materials to acquire the optimal state of a rotating functionally graded disk.     

平板波导凹面衍射光栅设计方法研究

提出了一种平板波导凹面衍射光栅的设计方法,即改进的刻槽位置递推计算方法。该方法是对原有刻槽位置递推计算方法的改进,利用该改进方法可实现平板波导凹面衍射光栅的精确设计,特别是一些特殊光栅结构的设计。光栅的刻槽位置可通过一组约束方程表示,利用递推方法可求得约束方程的数值解。为提高计算精度,在方程组的数值求解过程中引入牛顿迭代算法。设计了两种特殊的光栅结构,即平接收场结构和平顶频谱响应结构,模拟结果证明了采用该方法进行设计的必要性和有效性。     

Damping response analysis for a structure connected with a nonlinear complex spring and application for a finger protected by absorbers under impact forces

This paper describes the dynamic response of a finger protected by a pair of viscoelastic absorbers under impact forces. The restoring forces of the finger and the absorbers are measured using the levitation mass method proposed by Fujii. In this study, we carry out numerical analysis of the dynamic response of a finger protected by absorbers under the same conditions as in the experiment. The absorbers and the finger are modeled by nonlinear concentrated springs using the power series of the elongations. Nonlinear complex spring constants are used to represent the changes in hysteresis as elongation progresses. This nonlinear spring is connected to a levitated block, which is modeled by three-dimensional finite elements. The experimental data are compared with the data calculated using our proposed finite element method.