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微型塑件注射成型充模流动过程中,与宏观塑件相比,塑料熔体黏度随剪切速率的变化对流动的影响有很大的不同.对比微观和宏观黏度模型,运用流体分析软件Fluent,对微注塑充模流动过程熔体黏度的影响规律进行了研究.分析了熔体黏度的分布规律,结果表明微尺度降低了熔体黏度.研究了微尺度熔体黏度模型对熔体速度场、温度场和压力场的影响规律,结果表明:微尺度黏度模型的速度相对较大,近壁面区熔体温度相对较高,对微通道中的压力分布几乎没有影响.总体而言,由于通道微尺度而造成的熔体黏度变化有利于微注塑成型. 相似文献
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基于改进有限体积法的三维注塑成型充模过程数值模拟 总被引:1,自引:0,他引:1
根据界面两侧相邻有限体积流动切应力相等的原则,考虑到相邻有限体积内黏度系数的差异,改进传统有限体积法,并推导改进的有限体积中心速度梯度、界面速度和速度梯度的新的离散格式和计算格式。新的离散格式和计算格式能适用于注塑成型充模过程中型腔内塑料熔体黏度差异较大的情形,避免因黏度的变化导致界面两侧相邻有限体积内塑料熔体流动切应力的急剧变化。同理,根据界面两侧热流量相等的原则,推导有限体积中心温度梯度、界面温度梯度的新的离散格式和计算格式。改进有限体积法能有效提高数值模拟的稳定性和计算精度。采用改进的有限体积法分别模拟圆柱内稳态流动以及盒形件、带凹槽平板、一般三维特征的塑料制品的塑料熔体充模过程,模拟结果与理论精确解、试验结果、商业软件模拟结果吻合。数值算例表明改进的有限体积法能较准确地模拟注塑成型充模过程,也可应用于黏度变化比较大的其他单一流体或多种流体的耦合数值模拟,具有重要的理论和实用价值。 相似文献
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注塑成形流动模拟技术的新进展——从中面流到双面流再到实体流 总被引:1,自引:0,他引:1
李德群 《机械工人(冷加工)》2002,(4):20-21,51
1.概述 注塑成形流动模拟技术旨在预测塑料熔体流经流道、浇口并填充模具型腔的过程,计算浇注系统及模具型腔的压力场、温度场、速度场、剪切应变速率场和剪切应力场的分布,并将分析结果以图表、等值线图和真实感图的方式直观地反映在计算 相似文献
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《机电产品开发与创新》1996,(3)
本成果从流体流动与传热过程的结合上研究解决了目前的流动场计算方法在速度场、压力场、边界处理、流体进程计算自由表面处理等方面存在的诸项技术问题,并编制了铸件充型过程三维数值模拟软件和相应的后处理软件。三维计算软件由正个主程序和18个子程序构成,应用FORTURN语言编写,计3000句左右,主要功能包括:计算金属充型过程中三维瞬态速度场变化、压力场变化及金属波在型腔内的充填顺序;计算充型过程中及型胶充满后金属液和铸型的温度场变化,对铸件中可能出现的卷气、夹渣、冷隔、缩孔、缩松、V偏析和A偏析加以预测。后处理软… 相似文献
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超薄塑件注塑成形特性的试验研究与数值模拟 总被引:4,自引:1,他引:3
薄壁注塑成形技术具有节约材料、降低成本、减少制品重量和外形尺寸等优点,可促进移动电话等电子产品的迅速发展,特别是超薄塑件的注塑成形技术在微机电领域具有巨大的应用潜力。但随着制品厚度的减小也使注射成形难度加大,填充过程更为复杂,成形特性有待探索。设计制造出可成形超薄塑件的模具,利用正交试验方法(田口方法)进行充模试验和数值模拟技术研究各工艺参数(注射速度、注射压力、熔体温度、注射量和制品厚度等)对超薄塑件注塑成形充模过程的影响。研究结果表明,制品厚度对超薄塑件的填充起决定性作用;注射量及注射速度对超薄塑件注塑成形的填充起主导作用,提高注射速度能大幅度地提高填充率;熔体温度和注射压力相对于注射量和注射速度只起次要作用,但在填充过程中,高的熔体温度和注射压力也是必要的。 相似文献
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随着3D打印的发展,模型的轻量化建模已成为该领域的一个研究热点。提出一种"弱平衡"轻量化建模方案来生成3D打印模型的内部填充结构。该方案能够根据结构分析自动生成内部密度变化的填充。该方法主要包括三个步骤:利用基于截面结构分析的方法来分析模型的应力分布及薄弱部分;利用一种混合的网格偏置技术向内部偏置模型,生成壳体模型。根据模型的应力分布,提出一种改进的泊松圆盘采样技术在偏置模型表面生成连续的密度分布点,在应力大的区域,点的分布密集,而在应力较小的区域,点的分布较稀疏;提出一种"弱平衡"八叉树技术对采样点进行空间划分,利用体心立方结构及Delaunay 3D算法将偏置模型生成四面体网格模型。在该四面体网格模型中,单元四面体的体积从外部到内部渐变,且在物体薄弱部分填充密度较大。这些单元四面体被用来直接生成"框架-结点"结构。所提出的"弱平衡"轻量化方案允许根据应力分析在模型不同的部分生成不同密度的填充,从而取得全局优化的填充。 相似文献
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微流挤出成形工艺是基于陶瓷3D打印技术的兴起而出现的一种新兴制造工艺,其具有微米级高精度的特点,适用于高精度陶瓷制造领域。而在微流挤出成形工艺中,挤出结构设计是提高陶瓷零件成形性能的关键因素,将直接影响到成形能否顺利进行。在比较了几种目前国内外使用较为广泛的陶瓷3D打印挤出结构后,提出了一种以微型螺杆泵为核心部件的新型挤出结构。微型螺杆泵具有稳定的压力,可以输送高固含量的介质,并且能够根据转速调节流量,能够满足3D打印的稳定控制、高精度的工艺要求。还详细介绍了微型螺杆泵的工作原理,性能参数,对其应用在微流挤出自由成形工艺上的可行性以及入口压力、转速对其挤出流量的影响。 相似文献
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塑料注射成形过程仿真软件的开发和应用 总被引:6,自引:1,他引:5
智能型3维注射成形过程仿真系统HSCAE 3D解决了用3维实体/表面模型取代中性层模型的关键性技术难题,通过数值计算与人工智能技术的结合,使仿真软件由传统的被动式计算工具提升为主动式优化系统。实验和实践证明,HSCAE 3D为注塑制品与模具的虚拟制造奠定了坚实的理论和技术基础,构成了注塑制品成形质量全面控制的核心技术,已在模具行业中得到了很好的应用。 相似文献
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Dr M. C. Wu S. R. Jen 《The International Journal of Advanced Manufacturing Technology》1996,11(5):325-335
This paper presents a neural network approach to the classification of 3D prismatic parts based on their global shape information modelling. In this approach, a 3D part is modelled by the contours of its three projected views, which are approximately represented by three rectilinear polygons. The global shape information of each polygon is modelled by its simplified skeleton, which originally is of a tree structure and can be represented by several vectors by a conversion method. These vectors are the input to a polygon classifier which is constructed on the basis of the back-propagation neural network model. The classification results of polygons can be used to group the 3D prismatic parts into families in a hierarchical manner, by setting different levels of similarity criteria. The proposed method for classifying 3D workpieces can be used to enhance the productivity of design and manufacturing processes. By retrieving and reviewing similar parts from the part families, the designers or process planners could be greatly assisted in performing a new task. That is, they can avoid the reinvention of an existing design and can create a new design by modifying existing ones. 相似文献
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Rheology forming is a novel semi-solid processing method, which is different from traditional mold forging and conventional casting processes. The rheological behavior of metallic alloys containing both solid and liquid phases investigated the low and high solid fraction ranges. Rheology forming has several obvious advantages including its excellent forming ability resulting in the easier production of complex work pieces, more flexibility in shaping pieces, and more compact inner quality because of its high pressure. This research paper presents the theory of the rheology forming process and the results of a finite element simulation of rheology forming for aluminum alloys. The algorithms for both a single- and two-phase flow model, developed for this study, gives the die filling patterns, velocities, temperatures and solid fractions of the rheology material during the rheology process. To calculate the velocity and temperature fields, the respective governing equations corresponding to the liquid and solid regions were used. Therefore, the respective numerical models that take the co-existing solid and liquid phases within the rheology material into consideration have been developed to predict the defects of parts manufactured by the rheology process. This study compares of the velocity, temperature, and solid fraction between the single- and two-phase flow models. And, to predict the liquid segregation in the parts, the deviation of velocity between the liquid and solid regions in the two-phase flow model was analyzed. 相似文献
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Heng Wang Ruxin Ning Yan Yan 《The International Journal of Advanced Manufacturing Technology》2006,29(9-10):1019-1025
In current research of computer aided tolerancing (CAT), how to build models with tolerance and how to generate 3D dimension chains automatically have been tough problems and still unsolved. This paper builds a simulated toleranced CAD geometrical model (STCAD model) based on the feature-based original idealized CAD geometrical model (OICAD model), which can simulate real parts with manufacturing dimension errors from different aspects. Further more, an automatic generation method of 3D dimension chains based on some newly proposed definitions is put forward. In this method, firstly the conception of part instantiation (PI) is realized, secondly performance feature is defined, thirdly through building STCAD models, drive dimensions can be obtained which are vectorized to build drive dimension skeleton model (DDSM), and finally 3D dimension chains can be obtained by DDSM and the method of space projection. This method can generate 1D, 2D, and 3D dimension chains of parts or assemblies. It is verified in our own-developed automatic generation system of 3D dimension chains . 相似文献