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排序方式: 共有3616条查询结果,搜索用时 15 毫秒
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Bulge is a defect that causes geometrical inaccuracy and premature failure in the innovative incremental sheet forming (ISF) process. This study has two-fold objectives: (1) knowing the bulging behavior of a Cu clad tri-layered steel sheet as a function of forming conditions, and (2) analyzing the bending effect on bulging in an attempt to identify the associated mechanism. A series of ISF tests and bending analysis are performed to realize these objectives. From the cause-effect analysis, it is found that bulge formation in the layered sheet is sensitive to forming conditions in a way that bulging can be minimized utilizing annealed material and performing ISF with larger tool diameter and step size. The bending under tension analysis reveals that the formation of bulge is an outgrowth of bending moment that the forming tool applies on the sheet during ISF. Furthermore, the magnitude of bending moment depending upon the forming conditions varies from 0.046 to 10.24 N·m/m and causes a corresponding change in the mean bulge height from 0.07 to 0.91 mm. The bending moment governs bulging in layered sheet through a linear law. These findings lead to a conclusion that the bulge defect can be overcome by controlling the bending moment and the formula proposed can be helpful in this regards. 相似文献
3.
P. A. Boucard L. Champaney 《International journal for numerical methods in engineering》2003,57(9):1259-1281
The aim of the present work is to develop an application of the LArge Time INcrement (LATIN) approach for the parametric analysis of static problems with multiple contacts. The methodology adopted was originally introduced to solve viscoplastic and large‐transformation problems. Here, the applications concern elastic, quasi‐static structural assemblies with local non‐linearities such as unilateral contact with friction. Our approach is based on a decomposition of the assembly into substructures and interfaces. The interfaces play the vital role of enabling the local non‐linearities, such as contact and friction, to be modelled easily and accurately. The problem on each substructure is solved by the finite element method and an iterative scheme based on the LATIN method is used for the global resolution. More specifically, the objective is to calculate a large number of design configurations. Each design configuration corresponds to a set of values of all the variable parameters (friction coefficients, prestress) which are introduced into the mechanical analysis. A full computation is needed for each set of parameters. Here we propose, as an alternative to carrying out these full computations, to use the capability of the LATIN method to re‐use the solution to a given problem (for one set of parameters) in order to solve similar problems (for the other sets of parameters). Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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一个基于优化的有限元模型修正方法 总被引:10,自引:5,他引:5
本文提供了一个基于一阶搜索优化的有限元模型修正方法。它只需利用结构模态试验的部分固有频率,就能获得较精确的有限元模型。文中附有某无人机上垂尾有限元模型修正的实例。根据上垂尾前二阶试验的固有频率,采用本文方法,对有限元模型进行了修正。修正后有限元模型的前二阶固有频率与试验值的相对误差在2.35%以内,而第三阶固有频率与试验值的相对误差仅为5.81%。它不仅大大地缩小了用修正前有限元模型算得的固有频率与试验值的相对误差,而且还能较精确地预测无试验结果的高阶固有频率值。 相似文献
5.
Haitao Zhang Zonghai Chen Yongji Wang Ming Li Ting Qin 《International Journal of Adaptive Control and Signal Processing》2006,20(2):53-76
Laguerre Functional Model has many advantages such as good approximation capability for the variances of system time‐delay, order and other structural parameters, low computational complexity, and the facility of online parameter identification, etc., so this model is suitable for complex industrial process control. A series of successful applications have been gained in linear and non‐linear predictive control fields by the control algorithm based on Laguerre Functional Model, however, former researchers have not systemically brought forward the theoretical analyses of the stability, robustness, and steady‐state performance of this algorithm, which are the keys to guarantee the feasibility of the control algorithm fundamentally. Aimed at this problem, we introduce the principles of the Incremental Mode Linear Laguerre Predictive Control (IMLLPC) algorithm, and then systemically propose the theoretical analyses and proofs of the stability and robustness of the algorithm, in addition, we also put forward the steady‐state performance analysis. At last, the control performances of this algorithm on two different physical industrial plants are presented in detail, and a number of experimental results validate the feasibility and superiority of IMLLPC algorithm. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
6.
预测控制算法的统一格式及其在电加热炉的应用 总被引:4,自引:0,他引:4
本文根据常用的两类预测控制算法推出一种新型预测控制算法。并将其应用于一双输入/双输出的力学持久机电加热炉的温度控制系统上,获得了满意的结果:控温精度为±1.5℃/300℃,且适用于非最小相位系统。 相似文献
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In a series of experiments, participants were required to keep track of 1 or 2 working memory (WM) objects, having to update their values in 80% of the trials. Updating cost, defined as the difference between update and non-update trials, was larger when 2 objects were involved compared with when there was only 1 object was involved. This finding was interpreted as evidence that the updating process encompasses both objects in WM, even though only 1 of them is actually updated. This feature of WM updating is limited to objects defined as "updateable," throughout the trial sequence. The results are explained by the need to reprogram the phonological loop when updating or the need for desynchronization followed by resynchronization of WM contents. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
Mou Weimin; Biocca Frank; Owen Charles B.; Tang Arthur; Xiao Fan; Lim Lynette 《Canadian Metallurgical Quarterly》2004,10(4):238
In 3 experiments, the authors investigated spatial updating in augmented reality environments. Participants learned locations of virtual objects on the physical floor. They were turned to appropriate facing directions while blindfolded before making pointing judgments (e.g., "Imagine you are facing X. Point to Y"). Experiments manipulated the angular difference between the learning heading and the imagined heading and between the actual heading and the imagined heading. The effect of actual-imagined on pointing latency was observed for naive users but not for users with brief training or instructions concerning the fact that objects can move with body movements. The results indicated that naive users used an environment-stabilized reference frame to access information arrays, but with experience and instruction the nature of the representation changed from an environment stabilized to a body stabilized reference frame. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.
机械结构结合部精确建模是对含结合部的机械结构进行动态分析和优化设计的关键问题之一。文章主要研究块体结构和平板由螺栓联接后构成的固定结合部的动力学建模问题。将结合部区域的刚度特性用结合部的材料机械特性参数等效表达,提出了虚拟接触材料的结合部刚度表达模型。通过模态实验和模型修正识别出不同结合面工况下虚拟接触材料的弹性模量,建立了含结合部动力特性的有限元模型。该模型可方便用于含结合部结构的有限元计算,经试验验证满足实际工程应用要求。 相似文献