基于CAE的模态综合法误差分析

为研究用模态综合法进行发动机舱前端模型NVH分析时的误差,用整体计算法和模态综合法分别进行截止频率为100,200,300,1 000,2 000和3 000 Hz的模态计算,并基于模态计算结果进行原点传递函数计算.结果表明:考虑静态补偿的模态综合法计算误差小于不考虑静态补偿的计算误差;子系统模态计算截止频率大于2倍原点传递函数频率时,模态综合法计算误差小于10%;当传递函数频率是截止频率的1/3时,误差可以降低到5%。     

混合建模方法在某叉车方向盘振动分析中的应用

本文采用混合建模方法,将某叉车主要结构部件的试验模态和有限元模态综合起来,并使用自由界面的模态综合法完成主要部件装配后的系统级模态分析,模态分析的结果用于分析此叉车方向盘机构的振动问题,最后找到影响方向盘振动的主要原因,并提出改进方案,取得了良好的工程应用效果。     

基于ANSYS的螺纹连接法兰结构模态分析

运用工程分析软件ANSYS分析了螺纹连接法兰结构的模态。本文通过建立有限元模型对其进行模态分析得到固有频率、振型,对比分析不同固有频率对结构的影响,为螺纹连接法兰结构的有限元模型简化以及进一步的动力学分析、非线性接触分析提供了理论依据。     

基于ANSYS的车桥耦合振动分析

为准确分析车桥之间的相互作用,根据模态综合法推导车桥系统动力平衡方程,基于ANSYS前后处理器的桥梁建模和结果后处理功能,结合自主程序VBDIP(Vehicle Bridge Dynamic Interaction Program),形成1个通用工具用于分析车桥耦合振动问题.以单自由度质-弹系统通过简支梁桥模型为例,计算车桥的动力响应.所得结果与相关文献结果吻合良好,表明该方法正确有效,可用于分析各种车桥耦合振动问题.     

基于混合模态综合法的耦合分析软件开发

为实现大型复杂航天器结构的有限元动力学分析,运用Patran/MSC Nastran的二次开发语言PCL与DMAP开发基于混合模态综合法的分析软件模块.该软件模块将自编算法无缝嵌入到通用有限元软件中,计算精度和效率较高,可以为不同部门间的协同产品设计提供有效的解决方案.     

水下复杂声源结构自振特性分析

为解决水下复杂声源结构--潜艇的湿模态提取和扩展问题,用ANSYS非对称模态算法对其研究. 重点阐述浸没于水中的潜艇有限元建模方法,包括结构与流场的一体化单元划分、边界条件施加以及结构与流体耦合界面的处理等.通过仿真计算得到的潜艇湿模态和空气中干模态的分析结果,为潜艇外水域辐射声场预测提供重要参考依据.     

某磁浮飞轮转子系统有限元分析

为更好地分析计算磁浮飞轮转子系统的动力学特性,对其进行有限元仿真.基于已有的磁浮轴承控制律,根据相关参数计算出转子系统平衡位置处的线性化位移刚度,建立弹性支撑的磁浮飞轮转子有限元模型,用ANSYS对转子进行模态分析,研究支撑刚度和离心应力对转子系统模态和频率的影响.结果可为磁浮飞轮的信号测试和模态控制提供参考.     

110kV电力变压器绕组模态研究

变压器绕组等效的机械结构体,一旦发生改变,其模态将发生相应变化,此时对其振动信号进行频率响应分析,即可检测绕组轻微变形.对变压器绕组进行模态分析:利用ANSYS对绕组进行幅向建模分析,分别得到了绕组故障与正常情况下频响曲线的变化规律.开展真实110 kV变压器模态实验,并与ANSYS仿真结果对比,进一步验证了仿真结果的正确性,同时,为下一步研制振动检测系统奠定了基础.     

基于子结构的风力发电高塔系统的动力特性分析

采用子结构模态综合(Component Mode Synthesis,CMS)法和频响综合(Frequency response function-Based Substructure,FBS)法分析大型高耸装配结构风力发电高塔系统动力特性.通过子结构模态或频率响应函数(Frequency Response Function,FRF)信息综合成整体的模态或FRF信息,在保证整体分析精度的条件下提高计算效率,同时解决风电塔系统模态和FRF信息不易获得的问题.建立风电塔系统各个子结构的有限元模型和整体模型,分别使用MSC Nastran和LMS Virtual.Lab对各个子结构进行模态综合和频响综合分析,并将综合的结果与整体建模计算的结果进行对比,验证采用子结构CMS法和FBS法分析风力发电高塔系统的可行性和正确性.     

含参数多自由度非线性系统的降维方法研究

研究一类具有一定结构特点的含参数多自由度非线性系统,以固定界面动态子结构方法为基础,借助于灵敏度分析的基本思路,提出一种实用的降维方法首先根据实际系统的结构特点将其划分为若干子系统,使其中部分子系统是线性的,其余子系统是非线性的基于灵敏度分析的相关理论导出线性部分子系统的频率、模态对于参数的依赖关系,采用固定界面模态综合法将线性部分子系统的截断模态与非线性子系统进行综合,最终得到具有较低维数的含参数非线性动力系统结合具体算例,将降维前后的非线性动力系统随参数值变化时的对应的幅频特性曲线进行了比较算例表明,采用这里提出的降维方法所得到的低维系统可以较为准确地反映原系统的动力学特性．     

Current dynamic substructuring methods as approximations to condensation model reduction

Condensation Model Reduction (CMR) theory, when viewed as a dynamic substructuring method, is shown to encompass much of the existing dynamic substructuring methods as special cases of a single unified approach. Dynamic substructuring refers to the partitioning of a semi-discrete (continuous-in-time) mathematical model with respect to its dependence on the discretized independent variables (usually spatial) with the typical intention of eliminating most of the degrees-of-freedom in each partition (substructure) of a subset of isolated partitions. As an example, a contiguous subset of finite elements could be viewed as a substructure (superelement). One important use of dynamic substructuring is, hence, to analyze complex dynamic systems that are too large for current computers by reducing their size. The three currently used methods of dynamic substructuring are referred to as Guyan, Improved Reduced System (IRS), and Component Mode Synthesis (CMS) reduction, the latter having several variants. (The related Modal Reduction method was not considered here since, in that method, the work associated with reducing a particular substructure is not limited to that substructure.) In contrast to the current methods, the accuracy of CMR can be systematically improved by the inclusion of nonmodal higher order terms (as well as by the inclusion of additional modes). It is shown that the transformation matrices associated with both IRS and the Craig-Bampton (fixed interface) version of CMS approximate corresponding special cases of CMR. (The reduced-degree-of-freedom mass, damping, and stiffness matrices are different from those of CMR because CMR does not reduce the matrices via a matrix transformation.) In addition, the appearance of modes in CMR occurs as a natural consequence of the theory and not, as in CMS, as a heuristic inclusion to the transformation matrix. Classic Guyan reduction, in its entirety, is also shown to approximate a special case of CMR.     

基于柔性轮对的轨道车辆动力学仿真分析

为研究柔性轮对对轨道车辆动力学性能的影响,应用ANSYS创建轮对实体有限元分析模型,并选用Guyan缩减法和Lanczos分块法对其进行子结构模态分析.联合SIMPACK创建柔性轮对车辆仿真模型,此模型的构架、车体等部件仍视作刚性体.与刚体车辆仿真模型对比分析出在中国高铁谱和美国六级谱激励作用下两模型的动力学性能的差异.分析结果表明:轮对采用柔性体的车辆非线性临界速度较全刚体车辆的非线性临界速度稍稍降低.在两激励线路下,轮对采用柔性体对车辆的平稳性和曲线通过性能也有一定程度的影响.     

An improved method of substructure analysis

Substructure method is an established way of overcoming the difficulty of large dimensionality in analysing structures. An improved substructure analysis method suitable for structures like multi-storied buildings and towers is presented in this paper. The method is based on peculiar geometry of these structures which could be used for numbering the boundary joints for a substructure either in the beginning or towards the end. Extra advantage could also be taken of the substructures identical in terms of geometry and loading both or in terms of geometry alone. Special static condensation and substitutions routines are developed. The method is shown to be more efficient than any of the existing substructure analysis methods.     

New integration of preventive maintenance and production planning with cell formation and group scheduling for dynamic cellular manufacturing systems

This paper proposes a new integration method for cell formation, group scheduling, production, and preventive maintenance (PM) planning problems in a dynamic cellular manufacturing system (CMS). The cell formation sub-problem aims to form part families and machine groups, which minimizes the inter-cell material handling, under-utilization, and relocation costs. The production planning aspect is a multi-item capacitated lot-sizing problem accompanied by sub-contracting decisions, while the group scheduling problem deals with the decisions on the sequential order of the parts and their corresponding completion times. The purpose of the maintenance sub-problem is to determine the availability of the system and the time when the noncyclical perfect PM must be implemented to reduce the number of corrective actions. Numerical examples are generated and solved by Bender’s decomposition pack in GAMS to evaluate the interactions of the proposed model. Statistical analysis, based on a nonparametric method, is also used to study the behavior of the model’s cost components in two different situations. It is shown that by adding the PM planning decisions to the tactical decisions of the dynamic CMS, the optimal configuration and production plans of the system are heavily affected. The results indicate that omitting the PM actions increases the number of sudden failures, which leads to a higher total cost. Finally, it is concluded that the boost in the total availability of the dynamic CMS is one of the main advantages of the proposed integrated method.     

子结构方法在汽车约束系统固定点强度模拟中的应用

子结构方法是有限元仿真中只关注局部模型物理特性的一种重要的简化计算方法。它通过读取初始模型定义的子结构单元节点信息实现对整体模型的简化。通过这种简化可以节省大量的建模时间和计算时间,从而提高计算效率。本文介绍了子结构方法的基本原理和使用Pam-crash解算器的计算流程,并通过实例介绍了子结构方法在汽车约束系统固定点强度模拟中的应用,验证了该方法在汽车开发的实际仿真计算工况中的可行性和准确性。     

高炉炉壳结构力学分析软件开发

为探索基于ANSYS平台开发各类工程结构分析软件的通用方法,以高炉炉壳结构力学分析软件包为例,用VC＋＋编写程序并实现对ANSYS的封装．该方法可修改ANSYS的APDL数据文件中的输入参数,自动运行ANSYS的APDL批处理程序,利用ANSYS的OUT结果文件进行后处理,也可借助其他后处理软件进行后处理操作．该方法可使用户在不必熟练掌握ANSYS模块的情况下,利用ANSYS进行工程有限元问题的分析计算．     

门式起重机在特殊危险工况下的安全性能分析和评价

为全面分析和评价门式起重机在特殊危险工况下的安全性能,用MSC Adams进行虚拟样机动力学分析,用ANSYS进行有限元应力分析.结合实际运行情况和典型事故原因分析,提出门式起重机涉及吊重突然卸载、吊重自由跌落后紧急制动、大车碰撞轨道端部止挡、歪拉斜吊、台风下防风抗滑装置失效和吊物碰撞支腿等6种特殊危险工况;分析和评价...     

Advanced optical methods for safe image reproduction on automotive displays

Modern cars are equipped with camera monitor systems (CMSs), such as a backup camera or side-mirror replacement. These systems are expected to perform optimally and achieve high safety levels (ASIL). Currently, only digital data are supervised in CMSs and safety mechanisms for such systems are individually derived on a case-by-case basis which is not effective. This study proposes generic optical supervision for displays of automotive CMS. This paper introduces “light-to-light” (camera to display output) protection for both in-car CMS and remote operator monitors used in autonomous car fleet operation centers. The first method is based on photodiodes attached to the display to optically supervise, for instance, the speedometer of vehicles. By combining intensities of photodiodes with calibration data, we can compare the measured speed with the value from CAN (Controller Area Network) data. The second method that entails capturing the display content using a camera enables top safety levels for both in-car displays and remote operator monitors. This safeguarding was successfully verified by conventional image processing and artificial intelligence (AI)-based analysis methods. Our results demonstrate that AI methods allow a substantial reduction in the wireless transmission bandwidth from a car to a remote operator compared with conventional image processing.     

BLISS/S: a new method for two-level structural optimization

The paper describes a two-level method for structural optimization for a minimum weight under the local strength and displacement constraints. The method divides the optimization task into separate optimizations of the individual substructures (in the extreme, the individual components) coordinated by the assembled structure optimization. The substructure optimizations use local cross-sections as design variables and satisfy the highly nonlinear local constraints of strength and buckling. The design variables in the assembled structure optimization govern the structure overall shape and handle the displacement constraints. The assembled structure objective function is the objective in each of the above optimizations. The substructure optimizations are linked to the assembled structure optimization by the sensitivity derivatives. The method was derived from a previously reported two-level optimization method for engineering systems, e.g. aerospace vehicles, that comprise interacting modules to be optimized independently, coordination provided by a system-level optimization. This scheme was adapted to structural optimization by treating each substructure as a module in a system, and using the standard finite element analysis as the system analysis. A numerical example, a hub structure framework, is provided to show the new method agreement with a standard, no-decomposition optimization. The new method advantage lies primarily in the autonomy of the individual substructure optimization that enables concurrency of execution to compress the overall task elapsed time. The advantage increases with the magnitude of that task. Received December 5, 1999?Revised mansucript received April 26, 2000