Simulation of casting deformation based on mold surface element method

Deformation of casting during the solidification process has puzzled many engineers and scientists for years. In order to attain the goal of near-net forming by casting, numerical simulation is a powerful tool. Traditional methods compute the thermal stress of both the casting and the mold. This method suffers the problem of massive calculation and failure of convergence. This paper proposes an improved Mold Surface Element Method, the main idea of which is to use the surface elements instead of body elements to express the interactions between the casting and the mold. The proposed method shows a high computation efficiency and provides satisfactory precision for engineering. Two practical casting products were used to verify the proposed method. The simulated results agree well with those observed in practical products. The proposed method is believed to benefit production practice and to provide theoretical guidance.

Forming Mechanism of Gaseous Defect in Ti-48Al-2Cr-2Nb Exhaust Valves Formed with Permanent Mold Centrifugal Casting Method

A method combining theoretical analysis with experiment is adopted and the flowing process of Ti-48A1-2Cr-2Nb alloy melt poured in a permanent mould during the centrifugal casting process has been analyzed. A mathematical model of the filling process is established and the forming mechanism of internal gaseous defect is summarized. The results of calculation show that the melt fills the mould with varying cross-section area and inclined angle. The filling speed of the cross-section is a function of filling time. The cross-section area is directly proportional to the filling speed and the inclined angle is inversely proportional to the filling speed at a given rotating speed of the platform. Both of them changes more obvious near the mould entrance. The gaseous defect can be formed in several ways and the centrifugal field has an important influence on the formation of the defect. In addition, the filling process in centrifugal field has been verified by wax experiments and the theoretical analysis are consistent with experimental results.

Interfacial microstructure and mechanical properties of Ti-6Al-4V/Al7050 joints fabricated using the insert molding method

Ti-6Al-4V/Al7050 joints were fabricated by a method of insert molding and corresponding interfacial microstructure and mechanical properties were investigated. The interfacial thickness was sensitive to holding temperature during the first stage, and a good metallurgical bonding interface with a thickness of about 90 μm can be obtained at 750°C. X-ray diffraction, transmission electron microscopy, and thermodynamic analyses showed that the interface mainly contained intermetallic compound TiAl_3 and Al matrix. The joints featured good mechanical properties, i.e., shear strength of 154 MPa, tensile strength of 215 MPa, and compressive strength of 283 MPa, which are superior to those of joints fabricated by other methods. Coherent boundaries between Al/TiAl_3 and TiAl_3/Ti were confirmed to contribute to outstanding interfacial mechanical properties and also explained constant fracture occurrence in the Al matrix. Follow-up studies should focus on improving mechanical properties of the Al matrix by deformation and heat treatment.

Applications of the Finite Element Method to PDC Mold Design

This paper describes the structure of the molds for making polycrystalline diamond compact （PDC） drilling bits. It represents the mold shapes by using the Finite Element technique, and compares the analytical results with available experimental data. Based on the results of Finite Element analysis, some areas of stress concentrations are determined, and modifications made, to the PDC （polycrystalline diamond compact） mold. A displacement plot and several stress contour plots are presented. Techniques of the mold design are discussed.

基于Moldex3D的油漆桶桶盖注塑成型过程分析

利用模流分析软件Moldex3D模拟油漆桶桶盖注塑成型过程,研究桶盖模具使用阀式热流道与开式热流道两种不同浇注方案的成型差异,并结合仿真结果设计热流道。通过设计Taguchi DOE实验的因素与水平,优化桶盖产品的注塑工艺参数。结果表明:设定工艺参数为熔体温度250℃,保压时间2 s,冷却时间18 s时,产品没有短射、包封等外观质量问题;优化后的注塑工艺参数有效降低了产品的冷却时间。

Thermal stress analysis method considering geometric effect of risers in sand mold casting process

Solidif ication and f luid f low analysis using computer simulation is a current common practice. There is also a high demand for thermal stress analysis in the casting process because casting engineers want to control the defects related to thermal stresses, such as large deformation and crack generation during casting. The riser system is an essential part of preventing the shrinkage defects in the casting process, and it has a great inf luence on thermal phenomena. The analysis domain is dramatically expanded by attaching the riser system to a casting product due to its large volume, and it makes FEM mesh generation diff icult. However, it is diff icult to study and solve the above proposed problem caused by riser system using traditional analysis methods which use single numerical method such as FEM or FDM. In this paper, some research information is presented on the effects of the riser system on thermal stress analysis using a FDM/FEM hybrid method in the casting process simulation. The results show the optimal conditions for stress analysis of the riser model in order to save computation time and memory resources.

A New Method to Track Resin Flow Fronts in Mold Filling Simulation of RTM Process

A new method to track resin flow fronts, referred to as the topological interpolated method (TIM), which is based onfilling states and topological relations of adjacent nodes was proposed. An experiment on the mould filling process wasconducted. It was compared with exact solutions and the experimental results, and good agreements were observed.Numerical and experimental comparisons with the conventional contour mathod were also carried out, and it showedthat TIM could enhance the local accuracy of flow front solutions with respect to the contour method when mergingflow fronts and resin approaching the mold wall were involved.

Liquid-Gas Two-Phase Flow Simulation in Mold Filling Process with Level Set Method

Air entrapped in liquid metal during the mold filling process seriously affects the casting quality, thus it is important to track its behavior in the mold cavity. A liquid-gas two-phase flow model is developed to describe the mold filling process and predict the air entrapment defect. The model is based on the combination of SOLA and Level Set Method. The pressure and velocity fields are calculated by SOLA,and the interface movement is simulated by Level Set method as the most common interface tracking method in recent years.In order to validate the feasibility of the model,the liquid-gas two-phase simulation results were tested by the broken dam problem and the S-shaped experiment. Comparison between the experiments and simulation results show that Level Set method might be a very promising tool in two-phase flow simulation during the mold filling process.

Numerical Simulation of Mold Filling in Resin Transfer Molding Using Isoparametric Method

The mold filling of RTM was simulated based on the control volume finite element method (CV/FEM). The formulat ion using isoparametric transformation was discussed in detail and a computation al code based on isoparametric technique was developed. The simulation results w ere compared with experimental data. Different isoparametric elements, quadrilat eral and triangular, were compared in the simulation.It demonstrates that the us e of bilinear quadrilateral isoparametric elements in simulating the process can produce a higher precision and cost a less time than the use of triangular ones .

基于Moldflow的车身后护板微孔发泡注塑工艺多目标优化

使用Moldflow软件模拟车身后护板注塑工艺,采用正交试验及灰色关联分析结合熵权法优化注塑工艺参数,并进行了实际试模验证。结果表明:使用微孔发泡注塑成型可实现车身后护板减重及降低翘曲变形量;优化的工艺参数为熔体温度235℃,模具温度35℃,充填时间3.5 s,充填体积百分比92%,初始气体含量1.2%(w),所制零件总质量为1362.2 g,z方向翘曲变形量为1.006 mm,较采用微孔发泡默认工艺组合分别减少了18.4 g,0.478 mm;采用灰色关联分析结合熵权法对工艺优化能满足产品减重和降低翘曲变形量的要求。

基于Moldflow软件的短射法气辅成型数值分析及优化

使用数值成型对短射法气辅成型进行分析及优化。依据经验设计,对塑料扶手设计了3种进气方案,仿真结果表明:设置进气点位于浇口位置附近(方案3),气体虽未能充满所有部位熔体内部,但气道质量最佳。以方案3为基础,优化工艺参数,得到最佳方案为熔体注射量40%,气体延迟时间2.5 s,此时气体充满熔体内部,熔体壁厚减小且壁厚均匀,气道质量较好。以翘曲变形量为考察对象,运用正交试验法继续优化其他工艺参数,得到了最佳工艺方案为:熔体温度240℃,模具温度60℃,保压压力3 MPa,保压时间10 s。

基于Moldflow和Taguchi方法的汽车长饰条工艺参数优化

运用Moldflow软件,结合Taguchi方法,分析在注塑过程中模具温度、熔体温度、保压压力、保压时间对汽车长饰条变形量的影响。通过四因素三水平的正交试验,得出模具温度为70、熔体温度为260、保压压力为注射压力的80%、保压时间为10s是最佳注射工艺参数。优化后翘曲变形量为1.214mm,比优化前降低了37个百分点。经过试模,得到了高达93%以上的尺寸合格率。

Moldflow在导光板外框注塑模设计中的应用

将几何作图法和CAE软件分析法相结合,解决了导光板外框塑料件点浇口的数目及位置难以确定的问题。利用几何作图法初步确定浇口数目及位置,借助Moldflow软件的分析结果得到最佳方案。采用Moldflow软件对模具的冷却系统进行了优化设计。通过调整管路位置、优化保压曲线、改变模具温度和环境温度等措施解决了塑料件边角处翘曲变形量过大的问题。

基于UG NX 6.0 Mold Wizard的侧向抽芯直接分模方法

针对一需侧向抽芯的塑件,在UG NX 6.0中的Mold Wizard模块中,准确设置分型线,合理将分型面进行组合,快捷巧妙生成型芯、型腔及侧抽芯等,从而获得了实际应用的操作方法。使用该分模技术,有利于降低分模难度,提高模具设计精确度,掌握Mold Wizard分模的特点,为模具设计人员提供便利。

基于Moldex3D的电器壳体注射模设计

以塑料电器壳体为例论述了基于Moldex3D模流分析CAE的塑料注射模设计方法。针对该薄壳类塑件的塑料注射成型工艺进行了研究,包括电器壳体使用的ABS树脂材料性能分析,聚碳酸酯(PC)材料性能分析,塑件的注射成型工艺过程分析,针对该薄壳类塑件的侧向分型注射模的设计与制造研究及相关技术图纸资料分析等。

基于Moldflow注塑模具设计方案优化研究

以模具设计对注塑产品生产成本及质量的影响为研究目标,以Moldflow作为主要分析研究工具,建立了正交试验方案;以型腔数、流道直径、浇口直径及流道布局为模具设计方案技术参数;通过模拟试验及结果解析,考察技术参数在不同水平下对材料利用率、型腔压差比及单时出件数指标的影响,并对重要性进行了排序,应用综合加权评分法确定了设计方案技术参数的最佳组合,并进行了再模拟验证。

Rapid Springback Compensation for Age Forming Based on Quasi Newton Method

Iterative methods based on finite element simulation are effective approaches to design mold shape to compensate springback in sheet metal forming. However, convergence rate of iterative methods is difficult to improve greatly. To increase the springback compensate speed of designing age forming mold, process of calculating springback for a certain mold with finite element method is analyzed. Springback compensation is abstracted as finding a solution for a set of nonlinear functions and a springback compensation algorithm is presented on the basis of quasi Newton method. The accuracy of algorithm is verified by developing an ABAQUS secondary development program with MATLAB. Three rectangular integrated panels of dimensions 710 mmx750 mm integrated panels with intersected ribs of 10 mm are selected to perform case studies. The algorithm is used to compute mold contours for the panels with cylinder, sphere and saddle contours respectively and it takes 57%, 22% and 33% iterations as compared to that of displacement adjustment （DA） method. At the end of iterations, maximum deviations on the three panels are 0.618 4 mm, 0.624 1 mm and 0.342 0 mm that are smaller than the deviations determined by DA method （0.740 8 mm, 0.740 8 mm and 0.713 7 mm respectively）. In following experimental verification, mold contour for another integrated panel with 400 ram^380 mm size is designed by the algorithm. Then the panel is age formed in an autoclave and measured by a three dimensional digital measurement devise. Deviation between measuring results and the panel＇s design contour is less than 1 mm. Finally, the iterations with different mesh sizes （40 mm, 35 mm, 30 mm, 25 mm, 20 mm） in finite element models are compared and found no considerable difference. Another possible compensation method, Broyden-Fletcher-Shanmo method, is also presented based on the solving nonlinear fimctions idea. The Broyden-Fletcher-Shanmo method is employed to compute mold contour for the second panel. It only takes 50% iterations compared to that of DA. The proposed method can serve a faster mold contour compensation method for sheet metal forming.

基于Moldflow的绘图板注射成形优化设计

绘图板的注塑件在注塑过程中易产生翘曲变形。为此,基于Moldflow注塑模拟分析软件和正交试验方法,对不同工艺条件下的注塑过程进行了模拟分析,并运用隶属函数对分析所得的翘曲变形量进行评判。通过采用极差法分析出各因素对该塑件翘曲变形的影响程度和趋势,同时绘制因素水平影响趋势图,分析得到一组最佳的工艺参数组合方案,经过模拟验证后最终可指导绘图板注塑成形,生产出理想的绘图板产品。

Non-uniform heat transfer behavior during shell solidification in a wide and thick slab continuous casting mold

By employing a two-dimensional transient thermo-mechanical coupled finite element model for simulating shell heat transfer behaviors within a slab continuous casting mold, we predicted the evolution of shell deformation and the thermal behaviors, including the mold flux film dynamical distribution, the air gap formation, as well as the shell temperature field and the growth of carbon steel solidification, in a 2120 mm × 266 mm slab continuous casting mold. The results show that the shell server deformation occurs in the off-corners in the middle and lower parts of the mold and thus causes the thick mold flux film and air gap to distribute primarily in the regions of 0–140 mm and 0–124 mm and 0–18 mm and 0–10 mm, respectively, from the corners of the wide and narrow faces of the shell under typical casting conditions. As a result, the hot spots, which result from the thick mold flux film filling the shell/mold gap, form in the regions of 20–100 mm from the corners of the wide and narrow faces of the shell and tend to expand as the shell moves downward.