共查询到20条相似文献,搜索用时 804 毫秒
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主要介绍了RTM工艺树脂充模过程的流动模式、充模过程模拟的流动模型和模拟方法。讨论了不同模拟情况下所需的合理假设、边界条件的设置以及采用的不同数值计算方法。同时,介绍了目前基于数值计算的RTM仿真软件,提出了RTM充模仿真研究的未来发展趋势。 相似文献
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本文建立了描述气体辅助注射成型充模流动过程的数学模型,并采用有限元/有限差分混合算法进行数值求解,在对移动边界的处理上采用控制体积法对充模过程中的两类移动边界:熔体前沿、熔体-气体边界进行跟踪,从而实现气体辅助注射成型充模过程的数值模拟。通过对一平板带厚筋结构进行数值分析验证了本文给出的理论算法及软件的可靠性。 相似文献
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塑料注射充模过程流动分析的隐式控制体积法 总被引:4,自引:3,他引:1
为了改善充模过程流动分析隐式方法的迭代过程,提出了一种基于界面更新的隐式方法。该方法只对已注满结点进行求解,然后更新界面结点的体积函数以便决定是否要更新界面。计算表明了隐式方法性能良好,计算速度比显式方法有量级程度的改进。 相似文献
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借鉴塑料熔融注射技术,研究了胶料粘弹性引起的入口附加压力降和固体壁面滑移速度对充模过程的影响,从而建立了橡胶在薄矩形模腔内充模流动的数学模型。采用有限单元和有限差分混合方法求数值解。通过计算程序预测了充模过程中前锋线的移动及流动场,并根据模拟计算结果,分析讨论了各因素对充模压力的影响。 相似文献
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采用Level Set两相流方法模拟了熔体充模过程,避免了处理复杂的边界以及用Ghost方法将熔体内的速度值外推到熔体外的情况。分别对型腔水平中面与垂直中面的充模过程进行了模拟。讨论了不同注射速度、不同注射口数量以及不同Reynolds数对充模过程的影响,得出了不同时刻各种情况下熔体界面的位置与充模过程刚结束时型腔内的压力分布,分析了熔体在型腔内运动的不同阶段的特点及形成不同阶段的原因。结果表明,在注射口宽度与型腔宽度相差不大的情况下,如果采用中低速充模,则整个充模运动过程以比较平稳的扩展性运动为主,充模较完全,熔体不发生破裂,制件效果较好。充模速度越大,熔体达到平稳流动的时间越短,充模过程越短。数值模拟结果与实验结果一致,同时表明Level Set两相流方法在求解拓扑性质发生较大变化问题时具有很大的优势。 相似文献
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通过数值求解长方体塑料注射模腔中纤维运动的Fokker-Planck方程,得到纤维在塑料熔体中三维取向张量.计算结果表明:模腔界面附近纤维主要沿流动方向取向,模腔对称的中心面附近主要发生厚度方向的取向,而且3个方向取向中,流动方向的纤维取向度最高.此外,考虑了影响纤维取向的工艺因素,如熔体入口温度和模腔壁温、充模时间.其中,充模时间的影响较显著. 相似文献
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注塑流动与传热分析的自适应隐式控制体积法 总被引:1,自引:1,他引:1
在注塑流动与传热分析中采用自适应隐式控制体积法,利用自动控制的参数识别方法来自动调节时间步长,在每个时间步长流动将向前推进大约半个单元大小的距离,厚度方向的温度采用契比雪夫配点法进行计算,压力方程的求解方法是预条件共轭梯度法。计算结果表明,自适应隐式控制体积法的时间复杂度是结点数目的平方,而且1h之内可以求解10000结点规模的问题。 相似文献
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An interface‐update‐based implicit algorithm for mold filling simulation of liquid composite molding
In this article, a new implicit numerical algorithm has been presented for mold filling simulation in liquid composite molding process. The new implicit numerical algorithm is based on the update of flow interface to track flow front for each time step. Nodes of mesh are divided into three groups, i.e. filled nodes, interface nodes (or partially filled nodes), and empty nodes. Governing equations of filled nodes are solved to obtain pressure distribution; filling fractions of interface nodes are checked to determine if any node is needed to be added to filled nodes or be removed from filled nodes. The local LU factorization solver and preconditioned conjugated gradient iterative solver were employed to investigate the new implicit algorithm. Case studies demonstrated the performance of the proposed implicit algorithm. The new implicit algorithm reduced the computational complexity to below 2.0 power order of problem sizes. POLYM. COMPOS., 27:271–281, 2006. © 2006 Society of Plastics Engineers. 相似文献
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基于超稳定理论克服对象扰动自适应递归滤波辨识新算法 总被引:1,自引:1,他引:0
结合超稳定理论与自适应逆控制理论,提出了一种新的能够克服对象扰动的自适应递归滤波辨识算法。由于该算法前向方块为1,已满足严格正实条件,省去了求解前向方块严格正实的计算;反向方块中用超稳定理论求出的参数迭代适应律,克服了用传输函数形式表示的递归滤波器采用梯度法时可能陷于局部极小的缺陷,解决了证明参数收敛问题,并且在模型与对象完全匹配时消除了系统扰动,辨识出的模型更精确实用。仿真结果证实了.算法的可行性。 相似文献
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Adaptive PID control with an adjustable identification interval is proposed. The difficulty of choosing a suitable sampling time for control systems is prevented. The identification algorithm depends on that the identification interval is different from the sampling interval. Tuning of the PID controller is based on an adaptive first-order plus dead time model at each identification step. The model is obtained directly from an identified second-order one. Two illustrative examples are presented to show the considerable promise that the method exhibits. 相似文献
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An adaptive parallel tempering method for the dynamic data‐driven parameter estimation of nonlinear models
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Matthew J. Armstrong Antony N. Beris Norman J. Wagner 《American Institute of Chemical Engineers》2017,63(6):1937-1958
An adaptive parallel tempering algorithm is developed in a user‐friendly fashion that efficiently and robustly generates near‐optimum solutions. Using adaptive, implicit, time‐integration methods, the method allows fitting model parameters to dynamic data. The proposed approach is relatively insensitive to the initial guess and requires minimal fine‐tuning: most of the algorithm parameters can be determined adaptively based on the analysis of few model simulations, while default values are proposed for the few remaining ones, the exact values of which do not sensitively affect the solution. The method is extensively validated through its application to a number of algebraic and dynamic global optimization problems from Chemical Engineering literature. We then apply it to a multi‐parameter, highly nonlinear, model of the rheology of a thixotropic system where we show how the present approach can be used to robustly determine model parameters by fitting to dynamic, large amplitude, oscillatory stress vs. shear rate, data. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1937–1958, 2017 相似文献
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A simulation of the polymerization of methylmethacrylate in a CSTR is adaptively controlled by two types of pole-placement algorithms. The strongly nonlinear polymerization process, exhibiting multiple steady states, presents difficult control problems for conventional feedback controllers. The performance of an adaptive explicit SISO controller and that of an adaptive implicit multivariable controller are compared and evaluated as applied to this process. The plant is identified by a recursive least squares estimator. Modifications made to the estimation algorithm help to maintain adequate closed-loop results. A simple warm-up procedure is introduced that successfully initializes the controller and estimator during plant start-up. Good servo and regulatory control are achieved by both pole-placement schemes. 相似文献
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黄风立;许锦泓;顾金梅;娄勇坚 《中国塑料》2009,23(12):60-64
针对注射成型过程中的两个品质指标(翘曲量和收缩率),提出了基于综合关联度、Kriging模型及自适应遗传-蚁群算法的注射成型工艺参数优化方法。首先给出了综合关联度的定义及计算方法,然后给出了Kriging模型的拟合方法和自适应遗传-蚁群的优化算法。在结合带凸沿杯子的注射成型具体实例研究中,首先给出了注射成型工艺参数的范围,其次给出了基于正交实验的设计变量确定方法,然后基于超拉丁立方实验及Kriging方法进行模型近似,最后利用自适应的遗传-蚁群算法进行优化求解。模流分析及实际注塑实验表明,注射成型工艺参数优化的结果可靠,具有较好的实际意义。 相似文献
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Five methods are described for reducing or eliminating the error oscillations resulting from the application of the Peaceman-Rachford alternating direction implicit algorithm to disk electrode simulation problems involving an initial discontinuity, such as results from a potential jump at an electrode. The methods are: (a) the straight-forward application of the Peaceman-Rachford ADI algorithm, using sufficiently small time intervals so that the oscillations are damped at times for which accurate current values are needed; (b) using the first-order alternating direction implicit algorithm by Douglas and Rachford; (c) subdivision of the first simulation time interval into subintervals; (d) beginning the simulation with a few steps of the Douglas-Rachford algorithm followed by the Peaceman-Rachford method; and (e) presetting a reasonable approximation to the concentration profile at the end of the first simulation step and simulating from there on.Methods (d) and (e) are found clearly to be the most efficient at damping the oscillations, but method (b) also eliminates oscillations and leads to reasonable computation times, about one third of those needed for a sparse matrix solution of a two-dimensional system. 相似文献
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A feedforward plus feedback control method (FFC) and an adaptive feedforward plus feedback control method (AFFC) were proposed in this study to control the extrudate thickness of polymer extrusion. They were tested by step changes of screw speed and feedstock, and square wave type of screw speed changes. It is found that these feedforward control methods worked very well for various load disturbances but they required a good process model and accurate on-line measurements of manipulated variables and load variables. The feedback function was necessary to compensate the over- or under-corrections of the feedforward controllers and to handle other disturbances which were not considered in the feedforward model. 相似文献