共查询到18条相似文献,搜索用时 134 毫秒
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注塑模充模过程动态分析 总被引:2,自引:0,他引:2
注塑成型是利用型腔模制造理想制品主要的成型加工方式 ,塑料熔体的流动行为将直接影响着最终塑件的质量 ,塑料熔体在三维薄壁型腔内的流动属于带有运动边界的粘性不可压缩流体的流动 ,本文针对塑料注塑成型特点 ,经过量纲分析和引入合理而必要的假设 ,得到了适合于充模分析的数学模型。控制方程的求解主要包括三个阶段 :压力场、温度场和流动前沿位置的确定。数值求解采用有限元法求解压力场、有限差分法求解温度场、并利用控制体积法跟踪熔体前沿 ,实现了充模过程的动态模拟 相似文献
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建立了三维粘性不可压非牛顿流体流动的控制方程,采用Level Set/Ghost/SIMPLEC方法模拟了注塑成型充模阶段的三维流动过程;追踪到了不同时刻的熔体前沿界面,预测并分析了流动过程中不同时刻的压力、速度等重要的流动特征参数,并与牛顿流体相应的流动特征参数做了对比.研究结果表明:Lovol Set/Ghost/SIMPLEC方法可以准确追踪非牛顿熔体前沿界面:幂律熔体在流动过程中的压差明显大于牛顿熔体的压差,沿横截面的速度分布也有明显的差别. 相似文献
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基于实体的注射成型流动模拟 总被引:4,自引:0,他引:4
提出了应用中面模型技术模拟实体模型的注射成型流动过程的新方法。对实体模型的表面进行二维网格划分,将结点在厚度方向上配对.配对点之间添加虚拟热流道单元,建立二维有限元分析的网格模型。将HeleShaw流动应用于非等温条件下的粘性、不可压缩流体,建立基于中面模型流动分析的数学模型,用充填园子的输运方程描述流动前沿。用有限元计算充填过程的压力场.有限差分计算温度场,高阶的Taylor展开式计算每一时间步长的充填因子。针对Han设计的试验模具,用相同的材料及工艺条件,比较中面模型和实体模型的模拟结果。算例分析表明,这种方法可以有效地模拟基于实体模型的注射成型流动过程。 相似文献
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黏性不可压缩流体流动前沿的数值模拟 总被引:1,自引:0,他引:1
提出了模拟注射成型中黏性、不可压缩流体流动前沿的新方法. 将Hele-Shaw流动应用于非
等温条件下的黏性、不可压缩流体,建立了流动分析模型,用充填因子的输运方程描述流动
前沿. 应用高阶Taylor展开式计算每一时间步长的充填因子,用Galerkin方法导出了计算
充填因子各阶导数的递推公式. 给出了时间增量的选取方法,证明了它的稳定性. 针对Han
设计的试验模具,用相同的材料及工艺条件模拟充填过程,比较了传统方法和该方法的模
拟结果与实验结果的差异. 算例分析表明,该方法可以有效地提高注射成型中流动前沿的
模拟精度和计算效率. 相似文献
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基于气体穿透机理和Hele-Shaw流动模型,对管状模腔中气体冲破熔体前沿形成中空制品气辅成型过程进行了研究,推导出反映充模流动压力梯度比、非牛顿幂率指数等影响因素与计算表层熔体厚度比之间关系的数学公式,建立了熔体前沿和气体前沿速度与位移演化关系的数学模型,分别得出了牛顿流体和非牛顿流体选取不同影响参数时熔体前沿和气体前沿速度、位移的演化曲线.模拟结果表明,所建数学模型能较好的反映熔体前沿和气体前沿速度、位移演化关系.在气体冲破熔体前沿以前,气体接近匀加速运动,前沿位移梯度逐渐增加;熔体前沿的速度几乎保持不变,位移随时间接近线性增长.当气体冲破熔体前沿时,熔体和气体前沿的速度和位移均急速上升. 相似文献
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Wei Cao Changyu Shen Chunjie Zhang Lixia Wang 《Archive of Applied Mechanics (Ingenieur Archiv)》2008,78(5):363-377
A numerical approach is introduced to solve the viscoelastic flow problem of filling and post-filling in injection molding.
The governing equations are in terms of compressible, non-isothermal fluid, and the constitutive equation is based on the
Phan–Thien–Tanner model. By introducing some hypotheses according to the characteristics of injection molding, a quasi-Poisson
type equation about pressure is derived with part integration. Besides, an analytical form of flow-induced stress is also
generalized by using the undermined coefficient method. The conventional Galerkin approach is employed to solve the derived
pressure equation, and the ‘upwind’ difference scheme is used to discrete the energy equation. Coupling is achieved between
velocity and stress by super relax iteration method. The flow in the test mold is investigated by comparing the numerical
results and photoelastic photos for polystyrene, showing flow-induced stresses are closely related to melt temperatures. The
filling of a two-cavity box is also studied to investigate the viscoelastic effects on real injection molding. 相似文献
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To simulate filling flow in injection moulding for viscoelastic fluids, a numerical method, based on a finite element method and a finite volume method, has been developed for incompressible isothermal viscoelastic flow with moving free surfaces. The advantages of this method are, first, good applicability to arbitrarily shaped mould geometries and, second, accurate treatment for boundary conditions on the free surface. Typical filling flows are simulated, namely filling flow into a 1:4 expansion cavity with and without an obstacle. Numerical results predict the position of weld lines and air-traps. The method also indicates the effects of elongational flow on molecular orientation. 相似文献
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聚合物熔体在模具中的均匀性决定板材成型的质量。熔体具有非线性记忆性的粘弹效应,同时流道十分复杂。为准确、简便地分析熔体流动情况,针对板材机头流道的特点,提出了流动计算新的方法——有限柱半解析法,即在流道的厚度方向采用富氏级数描述流动分布,把三维有限元方程简化成为二维,得到以流量和压力为未知量的有限元方程。同时采用K-BKZ积分型本构模型描述熔体的非线性记忆性,给出求解非线性方程组的迭代方法,取得较好的收敛性。对两种典型的板材模具进行了分析计算,得出模具出口处的流量分布,通过把结果与三维有限元分析的结果相比较,表明该方法可以准确地分析板材模具中熔体的流动。 相似文献
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成型充填过程的ALE有限元模拟 总被引:2,自引:0,他引:2
在ALE框架中提出了一个用于成型充填过程有限元数值模拟的模型。应用ALE参考构形及ALE参考粒子速度描写充填过程中的熔体质量运动。摒弃了Hele-Shaw近似假定,因而所提出的模型能用于非薄壁型腔中高分子材料充填过程的数值模拟。应用基于时域分步算法的Taylor-Galerkin方法,对控制成型充填过程的守恒方程建立了弱形式。对移动自由面附近的充填材料区构造了网格生成算法与网格重划分方案。给出了在几种不同形状的典型腔体中充填过程的数值模拟结果,表明了所提出的ALE有限元模型模拟充填过程的有效性。 相似文献
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A mixed finite element formulation for viscoelastic flows is derived in this paper, in which the FIC (finite incremental calculus) pressure stabilization process and the DEVSS (discrete elastic viscous stress splitting) method using the Crank-Nicolson-based split are introduced within a general framework of the iterative version of the fractional step algorithm. The SU (streamline-upwind) method is particularly chosen to tackle the convective terms in constitutive equations of viscoelastic flows. Thanks to the proposed scheme the finite elements with equal low-order interpolation approximations for stress-velocity-pressure variables can be successfully used even for viscoelastic flows with high Weissenberg numbers. The XPP (extended Pom-Pom) constitutive model for describing viscoelastic behaviors is particularly integrated into the proposed scheme. The numerical results for the 4:1 sudden contraction flow problem demonstrate prominent stability, accuracy and convergence rate of the proposed scheme in both pressure and stress distributions over the flow domain within a wide range of the Weissenberg number, particularly the capability in reproducing the results, which can be used to explain the "die swell" phenomenon observed in the polymer injection molding process. 相似文献
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An innovative computational model, developed to simulate high‐Reynolds number flow past circular cylinders in two‐dimensional incompressible viscous flows in external flow fields is described in this paper. The model, based on transient Navier–Stokes equations, can solve the infinite boundary value problems by extracting the boundary effects on a specified finite computational domain, using the projection method. The pressure is assumed to be zero at infinite boundary and the external flow field is simulated using a direct boundary element method (BEM) by solving a pressure Poisson equation. A three‐step finite element method (FEM) is used to solve the momentum equations of the flow. The present model is applied to simulate high‐Reynolds number flow past a single circular cylinder and flow past two cylinders in which one acts as a control cylinder. The simulation results are compared with experimental data and other numerical models and are found to be feasible and satisfactory. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Extensive experimental data on the birefringence in converging and diverging flows of a polymeric melt have been obtained. The birefringence and pressure drop measurements were carried out in working cells of planar geometry having different contraction angles and contraction ratios. For investigation of diverging or abrupt expansion flow, the direction of flow in the cells was reversed. The theoretical predictions are based upon the Leonov constitutive equation and a finite element scheme with streamwise integration.In contrast to Newtonian and second-order fluids, viscoelastic fluids at high shear rates show significant differences in pressure drop and birefringence (i.e. stresses) in converging and diverging flows. For a constant flow rate, the pressure drop is higher and the birefringence smaller in diverging flows than in converging flows. This difference increases with increasing flow rate. Further, for the same contraction ratio but different contraction angles, the birefringence maximum increases considerably with contraction angle. In addition, an increase in contraction ratio has the same effect.The viscoelastic constitutive equation of Leonov has been shown to describe all the above viscoelastic effects observed in the experiments. In general, a reasonable agreement between theory and experiment has been obtained, which shows the usefulness of the Leonov model in describing actual flows. 相似文献