基于Abaqus的发动机缸体缸盖耦合仿真分析

为了解缸体缸盖的温度分布、强度、疲劳性能以及缸垫等的性能,对缸体缸盖进行耦合分析是十分必要的.利用Abaqus和Fire软件联合分析模型的温度场分布,确保各部件的温度性能满足要求,进一步分析各部件的强度以及疲劳性能,确保满足设计要求.     

某柴油机缸盖强度计算

以某4缸轿车用柴油机铝合金缸盖为研究对象,用某CFD软件计算得到水套表面的温度和对流换热系数,用Abaqus计算缸盖稳态温度场、装配载荷下冷机的应力分布、装配状态下的热机应力分布和各缸爆发时刻缸盖的应力分布,结果表明缸盖强度低于材料屈服极限.基于应力结果计算缸盖的高周疲劳安全因数和低周循环次数,结果表明缸盖疲劳安全因数满足使用要求.     

发动机缸体线性与非线性对比分析

采用线性分析发动机缸体时,在螺栓接触和绑定的位置会出现明显的应力集中点,且计算得到疲劳安全因数远远低于合理值.在考虑材料非线性的基础上对发动机缸体进行非线性分析,发现在螺栓接触和绑定位置处的应力明显降低,计算得到的疲劳安全因数也趋于合理.通过汽油机缸体线性与非线性对比分析可以发现,缸体非线性模型的计算结果更合理.若要改善螺栓孔周边的安全因数,一定要保证螺栓绑定和接触位置接近实际情况,特别在2个面过渡的位置不能绑定,这样可以避免造成应力集中.     

某缸盖高周疲劳分析

基于有限元法和应力疲劳理论,通过Abaqus和FEMFAT软件对某发动机缸盖进行温度场和结构耐久性计算分析.计算结果表明:在当前的载荷下,从温度分布和高周疲劳角度考虑,此缸盖可以满足安全运转需求,但是对于进一步提升发动机性能,其潜在承受能力较小.     

某发动机曲轴箱有限元分析

基于有限元分析和应力疲劳理论,通过Abaqus和FEMFAT软件,对某发动机缸体曲轴箱进行结构强度分析,得到其应力分布、接触情况和高周疲劳安全因数分布.结果表明此曲轴箱结构满足设计要求.     

机翼机身对接接头非线性有限元分析

接头是飞机结构中常见的结构连接形式,也往往是强度破坏或疲劳破坏的部位.有时为了更大的挖掘接头结构的承载能力,甚至还要考虑结构局部进入塑性区应力分布,属于材料非线性和力边界非线性的耦合问题.试图通过直接求解偏微分方程得到接头接触问题的解析解是很难的,甚至可以说是不可能的.基于非线性有限元分析方法,借助大型通用有限元软件MARC的弹塑性接触分析模块,通过不断细化网格的方法来对机翼机身对接接头进行非线性耦合分析.建立了对接接头的弹塑性接触有限元模型,给出了接头的应力分布以及屈服状况.数值模拟结果与实际情况相符,数值模拟结果为机身机翼对接接头的设计提供了重要的数据.     

分布式数据采集系统及其在坦克发动机测试中的应用

在内燃机的测试中，发动机缸体和缸盖的测试对于保证系统的正常运转至关重要。本文介绍一种采用分布式结构的数据采集系统，它特点适用于大型非运动部件的应力（场）、温度（场）、振动等各种参数的实况测试。文章最后给出了实际测试的结果和几种发动机异常诊断的方法。     

飞机结构整体优化和细节分析

飞机结构复杂,部件众多,连接形式复杂,传统的单一计算方法已很难满足计算要求,为更好地挖掘飞机的承载能力,还要考虑结构局部进入塑性区应力分布.对飞机结构进行有限元分析,有时需同时考虑整体和局部,大型结构采用较密的网格会耗费大量时间、资源等,甚至会导致计算不收敛;局部结构须划分较细的网格才能得到局部构件的细节应力.以某型飞机机翼为例,简单介绍开展飞机结构整体优化和细节分析的方法与流程.     

基于JSTAMP/NV的冲压模具变形分析

随着高强度钢在汽车车身上的广泛应用,冲压模具结构变形问题也日益突出.采用JSTAMP/NV和HyperMesh,对冲压成形和模具结构进行解耦有限元分析,研究模具各部件在成形过程中的应力分布规律和变形结果.结果表明：最大等效应力发生在曲率比较大的区域,而且不一定发生在模具的最终闭合阶段.该分析结果为优化模具结构设计和模具疲劳校核提供参考.在冲压成形仿真过程考虑模具结构变形的影响,结果显示模具结构的变形对材料的流入有很大影响,最终影响制品的成形精度.     

基于试验和仿真的缸盖疲劳耐久性研究

以发动机缸盖疲劳耐久性设计为研究对象,对缸盖材料进行不同温度下的疲劳测试,获取详细的缸盖高、低周疲劳材料属性,然后结合CAE疲劳分析方法和理论,进行缸盖金属温度场仿真、高周疲劳分析和低周疲劳寿命预测。该缸盖疲劳分析方法结果可靠,可有效指导缸盖疲劳耐久性设计和优化。     

磁道预留技术

磁盘操作是机械操作．基于磁盘的存储子系统是计算机主要瓶颈．在磁盘的操作中，磁头的寻道是磁盘操作的主要浪费，由于用户对数据的访问是偏斜的，提出磁道预留技术，将访问频率高的只读数据集中起来，并在预留磁道中进行复制；而对于写请求，磁盘驱动器可以就数据写入磁盘的空磁道或预留磁道．针对单盘与多盘的情况，分别研究了n-way预留与n-d-way预留策略．模拟试验表明，磁道预留技术能减少30％以上的寻道时间．     

车用发动机气缸盖与气缸套温度场测试系统设计

发动机工作时燃烧室内的温度很高,其缸盖和缸体内有循环水为其降温,水腔的设计直接决定发动机缸盖和缸套的降温效果,如果能够测试到燃烧室内壁温度,将对发动机缸盖、缸套水腔设计的降温效果提供有力数据。介绍了为得到某发动机气缸盖和气缸套的温度场分布规律而设计的基于存储测试技术的温度场测试系统。该测试系统获取了多种工况下气缸盖和气缸套上多个测点的温度变化规律。列出了部分通过实验得到的发动机不同转速和功率下的温度数据,并进行了简单分析。该测试系统测试通道多、同步性好,测试结果准确可靠。     

Transient performance of flow over a rotating object placed eccentrically inside a microchannel—numerical study

Industrial applications today are demanding the implementation of microelectromechanical systems (MEMS) into their products. These are mechanical devices that are able to perform work, and yet have characteristic lengths less than 1 mm. As a result, the Reynolds number is typically low, which indicates the dominance of viscous forces. When a cylinder is placed eccentrically inside a microchannel, where the rotor axis is perpendicular to the channel axis, a net force is transferred to the fluid as a result of the unequal shear stresses on the upper and lower surfaces of the rotor. Consequently, this causes the surrounding fluid in the channel to displace towards the microchannel outlet. The present numerical investigation is a comparative study of transient flow behavior in a microchannel with rotating cylinders with different cross-sectional geometries. The effects of channel height, eccentricity, Reynolds number, and pump load were studied, as well as the development of their respective streamlines and pressure contours. The steady state results were compared with existing numerical and experimental results, and the comparisons showed very good agreement.List of symbols C_D cylinder drag coefficient - C_L cylinder lift coefficient - C_M cylinder moment coefficient - d diagonal length of rotor (m) - F_L lift force on cylinder per unit length (N/m) - F_D drag force on cylinder per unit length (N/m) - h channel height (m) - L perimeter of rotor (m) - M moment on cylinder (N m) - ṁ mass flow rate (kg/s) - P_in inlet pressure (Pa) - P_out outlet pressure (Pa) - P* non-dimensional pressure - P channel pressure rise (Pa) - P* non-dimensional pressure rise - Q non-dimensional volume flow rate - Re Reynolds number - R normal distribution ratio - S curve length (m) - S non-dimensional channel height - t time (s) - t* non-dimensional time - t time step size (s) - ū average velocity inside microchannel (m/s) - u* non-dimensional average velocity - U cylinder surface velocity (m/s) - fluid velocity vector (m/s) - y_c distance from channel axis to cylinder center (m)Greek letters body forces per unit mass (m/s²) - rotor eccentricity - fluid dynamic viscosity (Pa s) - fluid kinematic viscosity (m²/s) - angle sweep over surface, =s/L (rad) - fluid density (kg/m³) - fluid shear stress (Pa) - * non-dimensional fluid shear stress - rotor angular velocity     

Simple Reconstruction of Tree Branches from a Single Range Image

3D modeling of trees in real environments is a challenge in computer graphics and computer vision, since the geometric shape and topological structure of trees are more complex than conventional artificial objects. In this paper, we present a multi-process approach that is mainly performed in 2D space to faithfully construct a 3D model of the trunk and main branches of a real tree from a single range image. The range image is first segmented into patches by jump edge detection based on depth discontinuity. Coarse skeleton points and initial radii are then computed from the contour of each patch. Axis directions are estimated using cylinder fitting in the neighborhood of each coarse skeleton point. With the help of axis directions, skeleton nodes and corresponding radii are computed. Finally, these skeleton nodes are hierarchically connected, and improper radii are modified based on plant knowledge. 3D models generated from single range images of real trees demonstrate the effectiveness of our method. The main contributions of this paper are simple reconstruction by virtue of image storage order of single scan and skeleton computation based on axis directions.     

Steady flow around and through a permeable circular cylinder

The steady flow around and through a porous circular cylinder was studied numerically. The effects of the two important parameters, the Reynolds and Darcy numbers, on the flow were investigated in details. The recirculating wake existing downstream of the cylinder is found to either penetrate into or be completely detached from the cylinder. It is also found that, contrary to that of the solid cylinder, the recirculating wake develops downstream of or within the porous cylinder, but not from the surface of it. These new findings provide additional evidence to Leal’s conclusion (Leal LG. Vorticity transport and wake structure for bluff bodies at finite Reynolds number. Phys Fluids A 1989;1:124) that the appearance of recirculating wakes at finite Reynolds number is due to vorticity accumulation, but not a result of the same physical phenomena associated with separation in boundary layers in adverse pressure gradients. Also presented in the current study are the variation of the critical Reynolds number for the onset of a recirculating wake as a function of Darcy number and the variation of a newly defined parameter, the penetration depth, as a function of the Reynolds number and Darcy number.     

基于广义柱面和线性插值的植物茸毛模拟

目前对植物器官细节化模拟的研究多集中在植物器官的整体表现,而对类似植物茸毛的细节模拟很少。针对该问题,提出一种基于广义柱面和线性插值的植物茸毛模拟方法。采用广义柱面生成植物器官和单个茸毛,通过线性插值的方法将茸毛附着在器官表面。实验结果表明,使用该方法模拟器官的茸毛,可视化效果较好。     

基于PDM的液压缸CAD系统的研究与开发

PDM是CAx信息集成的平台,本文在分析了PDM系统的功能模块以及PDM与CAD系统之间的信息集成关系的基础之上,应用VB6.0、ACCESS、AUTOCAD2004进行了系统的开发。系统主要由三部分组成液压缸辅助设计部分计算机辅助绘图部分和产品信息管理部分。实现了液压缸产品设计、计算、绘图以及产品数据管理的一体化,提高了产品设计水平和企业的信息化水平。     

基于PLC的装缸机控制系统的设计与实现

针对普通液压装缸机的控制精度低、不能实时监测参数变化以及智能化水平低的缺点,设计了基于PLC控制器和伺服控制技术的装缸机控制系统。介绍了以欧姆龙CP1H型PLC和台达伺服驱动器为核心的控制系统原理,给出了PLC和伺服控制器的硬件结构以及系统中各个传感器的电路设计。详细介绍了系统软件对各传感器的数据采集和处理流程,及各个伺服电机的动作控制流程。最后对系统进行了测试。结果表明,系统能够完成油缸的装配,保证装配的精度,可投入使用。     

Fourth-Order Semi-Compact Scheme for Flow Past a Rotating and Translating Cylinder

In the present investigation, the newly developed Higher Order Semi-Compact (HOSC) finite difference scheme has been tested for its capability in capturing the very complex flow phenomenon of unsteady flow past a rotating and translating circular cylinder. The physical problem has been modeled in stream function and vorticity formulation and the obtained governing equations are transformed into curvilinear coordinates using body fitted coordinate system to enable the developed scheme to handle the non-rectangular geometry of the problem. Qualitative and quantitative comparisons have been done at low-rotation parameters and found that the results obtained are in excellent agreement with the existing literature. Then simulations have been carried out at high-rotation parameters and noticed that the HOSC scheme is able to simulate some of the flow features known experimentally but not simulated numerically to the present date.     

两种脱粒滚筒的玉米籽粒损伤试验研究

脱粒是玉米种子加工的关键环节，也是影响种子质量的一个重要因素。尽量减少脱粒过程中的机械损伤是研制玉米种子脱粒机的关键指标。通过两种脱粒滚筒的脱粒对比试验表明：改变脱粒部件的机械作用力能有效地降低籽粒损伤，为改进脱粒方法及新型玉米种子脱粒机的研制提供参考。