共查询到19条相似文献,搜索用时 187 毫秒
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直接利用表面网格的几何信息计算最佳浇口位置,可显著提高浇口位置优化算法的计算速度与有效性。基于流动平衡的定义和权值流动长度,建立了优化目标函数。根据一定假设条件,将表面网格转化为带权值的无向图,结合遗传算法与爬山算法的优点,建立了Generic-Hillclimbing(GH)浇口位置搜索方法,并利用最短路径算法求解目标函数值。与Moldflow浇口优化功能相比较的实例表明,该方法能够高效准确地得到优化的浇口位置。 相似文献
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以某车型白车身为研究对象,首先建立白车身结构有限元模型并验证其有效性;随后通过对模型进行等效辐射声功率分析,得到白车身关键板件对车内的辐射噪声水平,并识别贡献量较大的结构位置;再根据分析结果构建白车身形貌优化模型并进行计算求解;最后将优化前后白车身等效辐射声功率进行对比,优化后辐射噪声在分析频段内整体降低,且最大响应峰值降低3.8 d B。研究结果表明,在汽车白车身设计阶段,基于等效辐射声功率分析和形貌优化设计可以有效地抑制结构的辐射噪声。该方法和思路可为工程领域相关的结构噪声分析和控制提供参考。 相似文献
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为了克服传统注塑成型过程的不可见性,在模具或者注塑机的料筒上人为添加视窗,在视窗位置用石英玻璃代替传统的金属材料,使用摄像机来记录聚合物的填充或塑化过程。主要介绍了物理可视化技术在模塑成型中的应用:利用高速摄像机拍摄得到熔体的充模过程,选取一定数量的图片,根据图片的时间差和流动前沿的位置变化,可以获得熔体流动前沿的填充形态和填充速度;利用椰果壳活性炭颗粒作为示踪粒子,可以得到熔体内部流场的流动轨迹和流动速度等重要参数;利用物理可视化技术结合模具关键位置的温度压力传感器,可以直观地解释填充不平衡现象产生的原因和规律。 相似文献
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对于《钢与混凝土组合结构设计施工手册》中关于T形截面实腹型钢砼梁抗弯承载力的计算假定提出了若干改进建议:按照中和轴与组合截面相对位置的不同,给出了较为完整的中和轴位置的判定准则:采用等效应力法计算此类构件抗弯承载力,得到了相关计算式。 相似文献
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提高汽车空调性能的主要方式是提高热交换器的换热效率. 由于汽车内部空间的限制,不能单纯依靠增加热交换器体积的方法来提高热效率,因此对热交换器结构优化设计将具有现实意义. 利用Flnent求解和正交设计的方法对汽车暖风机热交换器进行优化设计. Fluent软件可以模拟热交换器的流动和传热过程,正交设计的方法可以建立回归方程,因此可以得到出口温度的数学模型,该模型定量地描述了翅片间距、翅片高度及水管间距对换热效率的影响,优化汽车暖风热交换器的结构,最后通过试验证明了优化设计结果的准确性.优化热交换器的结构参数:翅片间距为1.1 mm,翅片高度为6.9 mm,管距为5.2 mm.根据Fluent模拟仿真得到出口温度的回归方程:Y=307.308+2.333X1 +0.677X2+0,561X3-2.501X12,影响出口温度的因素依次为翅片间距、翅片高度和水管间距.Fluent模拟仿真和正交试验设计相结合的方法有助于产品结构分析和优化设计. 相似文献
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船舶管路系统弹性支承在冲击作用下的位置优化设计 总被引:1,自引:0,他引:1
在强冲击作用下 ,船舶的管路系统会发生剧烈的振动 ,从而导致管路系统的破坏。本文拟采用不同边界条件的直梁模型 ,模拟管路系统 ,利用等效最优控制特性法建立系统的状态方程 ,进而得到直梁模型在多约束情况下的动态响应。经过对该模型冲击作用后在持续性周期荷载、随机荷载作用下的振动响应优化分析指出 ,合理布置弹性支承位置可以有效的避开共振区 ,改善弹性支承的减振效果。本文所得图表和结论对于管路系统弹性支承的位置设置提供了理论上的参考依据。 相似文献
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《Composites Part A》2002,33(9):1263-1272
In liquid composite molding (LCM) processes the resin is injected into a mold cavity containing pre-placed reinforcement fabrics through openings known as gates, and the air leaves the mold through openings called as vents. The gate and vent locations play a crucial role as to whether the resin covers all empty spaces between the fibers in the mold, which dictates the quality and the properties of the final product. Optimization methods are used to find the gate and vent locations that will create a favorable flow that will prevent dry spots. In this paper, branch and bound search is adapted to mold filling in LCM processes and is used to find the optimal injection gate location that fulfill two different objectives. First, to find the gate locations that will yield the shortest fill time. Second, to find the auxiliary gate locations that will counteract a disturbance during filling and minimize the size of the dry spot. In each case, three geometries have been studied. The results are compared with exhaustive search and genetic algorithms results to illustrate the efficiency and accuracy of branch and bound search method. 相似文献
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Pavel Simacek Suresh G. Advani 《International journal for numerical methods in engineering》2004,61(9):1501-1519
Mold filling in polymer and composite processing is usually modelled as a special case of Darcy flow in porous media. The flow pattern and the time necessary to fill the mold depend on the ‘gate’ locations where resin is injected into the closed mold. In composite manufacturing, these are commonly outlets of small tubes transporting resin from a reservoir and their diameters are several orders of magnitude smaller than the mold dimensions. Similar size issue is also encountered in other applications of flow through porous media, such as oil and water pumping and drilling. Traditionally, these inlets are modelled by pressure or flow rate boundary condition as applied at a node of the finite element mesh that represents the injection gate. The omission of the inlet radius in the model results in a mathematical singularity as the mesh gets refined. The computed pressure or flow field depends on the mesh size and does not converge to the accurate solution, as the finite element mesh is refined. It is possible to deal with this phenomenon by modelling the inlet geometry more accurately but this approach is inefficient, as it requires additional degrees of freedom and, above all, significantly complicates the modelling process if the inlet location is not fixed a priori. This paper presents a more efficient alternate solution. It uses special ‘gate’ elements embedded in the mesh around the injection locations. Instead of adjusting the geometrical modelling of the injection location, the adjacent elements use modified shape functions to accurately model pressure field in the neighbourhood of small radial inlet. The proper pressure field shape‐functions for ‘gate’ elements based on linear finite elements are derived. The implementation in an existing mold filling simulation and how the ‘gate elements’ are automatically selected is described. An example to demonstrate the use of ‘gate’ elements and convergence towards the accurate solution with mesh refinement is presented. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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《Composites Part A》2002,33(4):471-481
Resin transfer molding (RTM) is considered a promising manufacturing process for high performance composite materials. In the RTM process, gate/vent location is one of the most important variables in process design. It has a great impact on mold filling time and resin flow pattern, thus affects the process efficiency and product quality. Many studies have been conducted on optimization of RTM mold filling process to determine the locations of gates and vents. Most of them approached the optimum process design problem via numerical method-based process simulations. Due to the extensive computations involved, such approaches are difficult to be implemented for large and complex parts. This paper introduces a new approach to optimum arrangement of gates and vents for two-dimensional or two and a half-dimensional parts based on the mesh distance concept. With the assumption that the resin first fills the nodes closest to gates, the vent locations that minimize the area of trapped air can be determined. With the objective of minimizing the maximum distance between gates and vents and avoiding dry spot formation, genetic algorithm was employed to carry out the gate location optimization. The new RTM process design approach was tested on numerous cases obtained from the literature. It was found that the new approach was very efficient and effective in finding the optimal locations for gates and vents. The resulting gate and vent locations lead to satisfactory process performance as indicated by the optimal process performance index. The computational time required by the new approach was only a fraction of that reported by those simulation-based methods in the literature. 相似文献
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In Resin Transfer Molding (RTM) processes, liquid resin is injected into a dry reinforcement structure to create a composite part within given time limits. To reduce the fill time, resin may be injected into the mold through multiple gates. The minimum number of gates and their locations needs to be determined. To reduce the number of scenarios to be simulated, an iterative method is implemented for multiple-gate injection optimization. The inlet nodes on the mesh surface are used to generate a Voronoi Diagram of the mold geometry. Then the optimal Centroidal Voronoi Diagram (CVD) of the mold surface is searched iteratively. It is shown that the generation points associated with the optimal CVD correspond with the gate locations that yield the shortest fill time. The results are compared with exhaustive search and genetic algorithms results to illustrate the efficiency and accuracy of CVD method. 相似文献
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树脂传递成型加工工艺是一种先进复合材料加工的方法。虽然计算机数值模拟的研究已经取得了很大进步,但计算机数值模拟非常耗时间。本文中提出了一种树脂传递成型工艺注射口位置的快速优化方法。该法假设树脂首先注满离注射口近的节点,再根据溢料口的位置安排要求避免干点的出现这一点来决定溢料口位置;如果设计的溢料口数量比计算出来的必须的溢料口数量少,则会出现干点区。把干点区的面积作为罚函数加入目标函数中,目标函数的主体是从注射口到溢料口的距离。因此,笔者是在固定溢料口和注射口数量的前提下优化注射口的位置,获得注射口位置后,经过计算将获得溢料口位置。由于注射口位置是在离散的节点位置上,优化的变量是节点编号,所以优化方法采用功能很强的遗传算法来进行。针对五种模型进行了优化,优化的结果说明了本方法的可行性。 相似文献
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This paper studies the effects of gate size on the cavity filling pattern and residual stress of injection molded parts. A total of three rectangular gates with different sizes were used. Experiments were carried out by using a dynamic visualization system. A flow visualization mold was specially designed and made for this study. A high-speed video camera was used to record the mold filling phenomena of cavities with different gate size and different processing parameters. In addition, a Stress Viewer was used to characterize the residual stress of molded samples. It was found that the undersized gate has many adverse effects on the filling behavior and residual stress of molded parts. With a larger gate, the cavity will be filled faster and residual stress of parts may be smaller. The result of the study also indicates that nozzle temperature and injection rate can significantly affect the above two aspects. 相似文献
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Sara Liparoti Andrea Sorrentino Giuseppe Titomanlio 《Materials and Manufacturing Processes》2019,34(4):422-430
An accurate mold temperature control during injection molding processes allows obtaining objects with better surface finishing, more accurate surface replication, and reduced frozen-in orientation. The control of these properties is particularly important when the thickness of the molded part is very small as in the case of microinjection. In this work, thin multilayer heaters are adopted to obtain a very fast mold surface temperature evolution during the process of an isotactic polypropylene (iPP). The effect of mold temperature history on the pressure developed inside the cavity is analyzed and correlated to both gate solidification and mold deformation. Results confirmed that, with a fast control of the cavity surface temperature, a reduction of the injection pressure is achieved, without affecting the cycle time. The understanding of the phenomena that occur during the fast temperature evolution on the cavity surface can allow the microstructural calibration of the molded parts. 相似文献