板料成形中的回弹计算和模具修正

利用动力显式有限元计算程序MSC／DYTRAN,采用动力松弛法模拟了板料成形及回弹过程,计算出板料成形后的回弹量：提出“位移描述－结点修正”法,以回弹量为依据通过反向位移补偿和插值算法,编制程序自动对模具网格结点进行修正,通过反复迭代计算,最终可获得生成理想形状制件所必需的凸,凹模尺寸。     

An Investigation of the Process Parameters for Calibre Rolling Using a Complex Analytical Model

Calibre rolling is a complex 3D boundary problem. Several analytical methods were applied to analyse this topic and some progress was achieved. However, it was difficult to include both analytical precision and CPU time saving in the calibre rolling analysis. In this paper, the simplicity of the 3D slab method and the precision of 3D rigid-plastic finite element method were combined to develop a complex analytical model. This model can rapidly simulate calibre rolling and the results obtained match well with the experimental ones. A complex analytical model can be used for discussing the influence of each process parameter on calibre rolling, which can assist the efficient process design of calibre rolling and find the optimal combination of each process parameter.     

An accelerated springback compensation method

Part shape error due to springback is usually considered to be a manufacturing defect in sheet metal forming process. This problem can be corrected by adjusting the tooling shape to the appropriate shape and/or active process control. In this paper, the focus will be on tooling shape design. The traditional trial-and-error methods are inefficient for complex dies. Several analytical methods have been proposed in recent years. Each of these has their advantages and disadvantages. As expected, all these methods required a few iteration steps before converting to the desired tooling shape. Here, we put all of these proposed methods under the same framework. Additionally, built upon existing methods, a new methodology is proposed by incorporating pure geometry correction with fundamental mechanics analysis. Consequently, the convergence becomes much faster and certain. Tooling design results from the new method, together with three existing methods, are compared with each other and an experiment.     

基于有限元法的螺栓连接结构模态参数识别

通过有限元预紧力单元模拟螺栓预紧力的方法计算量较大,不太适合大型螺栓连接结构的工程计算。基于有限元软件MSC./Patran,将螺栓连接结构视为层单元,应用层单元法和多点约束技术对典型的L形螺栓连接结构建立了有限元模型,并完成了模态分析,将模态计算结果与完全刚性连接的一体化简化模型的模态分析结果及实际结构的模态实验结果进行了比较。研究表明,该方法的计算结果与实验结果较一致,且计算量小,为有预紧力作用下螺栓连接结构的有限元计算提供了准确可靠的计算方法。     

ANALYSIS OF SLAB EDGING BY A 3-D RIGID VISCO-PLASTIC FINITE ELEMENT METHOD

0 INTRODUCTIONin order to expand a synchroulsed opeT'ationbetWeen the continuous slab casting and hot rollingprocesses, heaVy breadth reduchon is widely obtainedby either rolling or Pressing in roughing theins of hotstriP Inills. So the vwhcal-horizonta rolling process isstin twortan for obtaining high precise width ofstriP [l;]. Some researchers have sinuhad the slabedgin with flat rolling [3'4J and the whole vedcaLhorizonta rolling [sl by FEM. However there havebeen problems wAn pr…     

Estimation of region of attraction for polynomial nonlinear systems: A numerical method

This paper introduces a numerical method to estimate the region of attraction for polynomial nonlinear systems using sum of squares programming. This method computes a local Lyapunov function and an invariant set around a locally asymptotically stable equilibrium point. The invariant set is an estimation of the region of attraction for the equilibrium point. In order to enlarge the estimation, a subset of the invariant set defined by a shape factor is enlarged by solving a sum of squares optimization problem. In this paper, a new algorithm is proposed to select the shape factor based on the linearized dynamic model of the system. The shape factor is updated in each iteration using the computed local Lyapunov function from the previous iteration. The efficiency of the proposed method is shown by a few numerical examples.     

复杂型面板料件冲压仿真有限元建模技术研究

探讨了具有复杂型面的大型板料件冲压仿真有限元建模过程中的一些关键技术问题。针对此类零件具有几何形状复杂的特点 ,利用造型功能强大的三维造型软件对由扫描测量机测到的离散数据进行拟合和光顺处理 ,得到零件的精确曲面 CAD模型 ,然后通过标准数据转换接口 ,将 CAD模型转入仿真软件的前处理器中 ,再利用软件的曲面网格划分功能对其进行网格划分 ,最终建立起冲压仿真所需的有限元模型。以轿车门内板冲压仿真有限元模型建模为例 ,说明了复杂型面板料件冲压仿真有限元建模技术的实际应用。     

Shape optimization of mobile phone folder module for structural strength

The mobile phone has become thinner even while its functionalities are ever increasing. Therefore, the importance of structural design to prevent structural failure is of increasing importance. To address this situation, a systematic optimization approach for shape design of a mobile phone folder module is utilized in this research. The structural strength and the exactness of the folder module assembly are considered as performance requirement of the optimization problem. Five shape parameters of the folder module assembly are used as design variables. In this research, the finite element method (FEM) is used to acquire the structural strength of the folder module assembly, and the morphing technique is applied to change the shape of the finite element (FE) model. However, manually performing the morphing and FEM for the simulation model is complex and time consuming especially for a model with complicated shape such as the mobile phone. Therefore, shape optimization involving FEM is known to be very difficult task for actual industrial applications. To overcome this deficiency, two types of approaches are applied in this research. First, process integration and design optimization (PIDO) technology is applied to integrate and automate the analysis processes needed for evaluating structural performances. In addition, a metamodel that can substitute for expensive simulation is employed for the optimization process. From this research, an optimum design for the folder module of a mobile phone enhancing the structural strength is acquired. In addition to the optimum solution, a metamodelbased shape optimization procedure which is applicable to practical engineering problem is established.     

改进的生物生长法及其在离心叶轮三维形状优化设计中的应用

考虑到传统生物生长法只能对简单形状进行优化的局限性,结合复杂结构的三维形状优化设计,对生物生长法提出三点改进:①不直接采用修正后节点坐标来调整网格,利用B样条函数描述修改后结构的外边界。②构造出在满足应力和几何条件下可使结构重量最轻的目标函数,进而大大增强了生物生长法在处理复杂结构形状优化设计方面的能力。③在生物生长法形状优化过程中,采用罚方法对违反约束条件的个体给予惩罚。作为工程实例,该方法被用于某三维离心叶轮的结构形状优化设计。计算结果表明,该方法可在较短时间内得到满足各种应力和几何约束的重量最轻解。     

Hybrid radial basis function/finite element modelling of journal bearing

This paper presents a novel approach through the combination of radial basis function (RBF) with Galerkin finite element method (FEM), to determine the solution of journal bearings. We divide the flow field into several subdomains. Local weak integration form of Reynolds equation is developed. The new model uses the point interpolation based on RBF to obtain the shape functions in each subdomain. The global solution is set up on the base of the local solutions of each subdomain. We demonstrate the efficiency and accuracy of the new method in detail using a statically loaded bearing example and by numerical comparisons among RBF method, FEM method and the hybrid method. We found that the large node and element number problem, the large matrix condition number problem, and the shape parameter-sensitivity problem all decrease. We also simulate the self-excited instability phenomenon and unbalance response of a flexible rotor-bearing system with the new model successfully.     

RIGID-PLASTIC/RIGID-VISCOPLASTIC FEM BASED ON LINEAR PROGRAMMING—THEORETICAL MODELING AND APPLICATION FOR AXISYMMETRICAL PROBLEMS

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3D ECT reconstruction by an improved Landweber iteration algorithm

Electrical capacitance tomography (ECT) is a relatively mature non-invasive imaging technique that attempts to map dielectric permittivity of materials. Recently, 3D ECT has gained interest because of its potential to generate volumetric images. The study of a fast and accurate image reconstruction algorithm is a challenge task, especially for 3D reconstruction. In this paper, we propose an improved Landweber iteration algorithm. We incorporate an additional acceleration term into the cost function and apply an adaptive threshold operation to the image obtained in each iteration for reducing artefacts. The algorithm proposed is tested by the noise-free and noise-contaminated capacitance data. Sensitivity matrixes and capacitance data of a 3D ECT sensor are obtained by using the finite element (FE) method. Extensive simulations in 3D reconstruction are carried out. The results verify the effectiveness of these improvements. Both the reconstruction time and the artefacts in the reconstructed image are reduced obviously. The experimental results of 3D reconstruction of objects in the shape of letters U and L confirm the effectiveness of the proposed algorithm further.     

重型卧式卡盘结构分析与优化

建了重型卧式四爪卡盘的有限元模型,确立了相应的载荷和边界条件;通过有限元分析,获得了重型卧式四爪卡盘应力分布与变形分布状况;通过进一步分析结构各部分的受力特性,提出了优化设计方案.该方案在保证盘体刚度增大、最大变形位移减少的情况下,可以使盘体的总重鲢减少10%,取得了良好的效果.     

轮腿式机器人轮-腿高效移动策略优化

复杂地形下的高效移动策略是轮腿式机器人研制过程中的技术难点。本文在常规移动策略的基础上，通过引入关节空间状态量描述支腿相对于机身的位姿，引入位姿转换量描述相邻时序的位姿状态量间的运动过程，进而建立起移动策略与时间和能耗的数学模型，并以移动时间最短和能耗最低为目标，建立了移动策略的优化模型，通过优化迭代形成轮-腿高效移动策略。复杂地形下的越障仿真表明，机器人采用轮-腿高效移动策略可实现越障功能，与常规移动策略相比，移动时间及能耗均明显降低，验证了轮-腿高效移动策略的有效性。     

Carbody structural lightweighting based on implicit parameterized model

Most of recent research on carbody lightweighting has focused on substitute material and new processing technologies rather than structures. However, new materials and processing techniques inevitably lead to higher costs. Also, material substitution and processing lightweighting have to be realized through body structural profiles and locations. In the huge conventional workload of lightweight optimization, model modifications involve heavy manual work, and it always leads to a large number of iteration calculations. As a new technique in carbody lightweighting, the implicit parameterization is used to optimize the carbody structure to improve the materials utilization rate in this paper. The implicit parameterized structural modeling enables the use of automatic modification and rapid multidisciplinary design optimization （MDO） in carbody structure, which is impossible in the traditional structure finite element method （FEM） without parameterization. The structural SFE parameterized model is built in accordance with the car structural FE model in concept development stage, and it is validated by some structural performance data. The validated SFE structural parameterized model can be used to generate rapidly and automatically FE model and evaluate different design variables group in the integrated MDO loop. The lightweighting result of body-in-white （BIW） after the optimization rounds reveals that the implicit parameterized model makes automatic MDO feasible and can significantly improve the computational efficiency of carbody structural lightweighting. This paper proposes the integrated method of implicit parameterized model and MDO, which has the obvious practical advantage and industrial significance in the carbody structural lightweighting design.     

静电拉伸薄膜反射镜的多电极成形控制

针对现有薄膜反射镜成形控制方法存在求解复杂,工程实用性差等问题,提出了基于反演求解的半解析成形控制方法.首先,基于Karman方程和静电场理论推导了所要拉伸的抛物面面形与施加压强分布的关系及实验所需的离散电极环电压值;其次,利用有限元软件建模和分析,验证所推导的压强分布;最后,在口径为300 mm的三环电极的静电拉伸反射镜实验平台上进行了验证实验.实验显示,拉伸面形最大变形量与理论值基本吻合,面形误差与传统均匀压强下的相比有所减少,最好的实验结果得到的PV值和RMS值较均匀压强下的值分别减少了9.76％和15.38％.仿真及实验结果表明:所描述的方法可以控制面形并提高面形精度,与传统的成形控制方法相比较具有简单实用等优点.     

Lumped parameter modeling and analysis of hybrid magnet engine valve actuator

The hybrid magnet engine valve actuator (HMEVA) composed of two types of magnets (permanent magnet and electromagnet) and two balanced springs is a promising tool for implementing innovative engine management strategies for variable valve timing. Finite Element Method (FEM), a favored actuator design tool due to its high accuracy, was utilized to analyze the electromagnetic actuator, but it consumes a lot of time especially in computation iterations for optimization. Accordingly, the magnetic equivalent circuit analysis can be an alternative tool to FEM because of its computation iteration capability with fair accuracy. In this paper, an equivalent magnetic circuit model of an HMEVA is developed considering the reluctances, external magnetic forces and so on, and the simulation results are presented. In addition, the result of lumped parameter analysis (LA) is compared with those obtained from finite element analysis for verification.     

等温弹流润滑点接触问题有限元解法

弹流润滑点接触问题数值解大多采用有限差分法对雷诺方程进行求解 ,本文采用有限元法对等温弹流润滑点接触问题进行探讨 ,采用直接法迭代得出给定工况下该问题的数值解包括油膜形状与接触区的压力分布。所用解法与结果可作为对弹流点接触问题数值解研究的补充与比较     

改进的动力学参数迭代辨识方法

迭代的辨识方法考虑了物理可行性约束、异常采样数据的去除和更符合实际的摩擦模型,因此可以获得更准确的动力学参数。针对需要辨识的参数多导致迭代时间成本高的问题,提出一种改进的动力学参数迭代辨识方法,通过引入 F 统计量剔除对机器人关节力矩几乎没有贡献的参数,降低迭代中需要辨识的参数的维度,以减少辨识时间、提高辨识效率。实验结果表明,在 Chin7 机器人上,该方法能在不影响力矩计算精度的前提下将辨识的计算时间减少 45% 。