铸件凝固过程中热应力场及热裂的数值模拟研究分析

简述了铸件凝固过程数值模拟的研究现状 ,重点介绍了铸件凝固过程中热应力场及热裂数值模拟研究的方法和发展趋势 ;指出了基于流变学模型的热应力场和热裂数值模拟是今后的热点研究方向之一。     

基于凝固过程数值模拟的水轮机下环件微裂纹成因分析

针对某重型设备公司铸造的下环铸件出现的类似微裂纹的铸造缺陷,采用数值模拟方法,从凝固过程热应力角度对缺陷产生的原因进行了分析.利用ANSYS软件计算了下环件凝固过程中的三维应力场.根据热裂形成机理,提出了适当的热裂倾向性预测方法,重点考察了铸件凝固过程中准固相区的受力情况,从而确定热裂倾向性严重的区域.模拟结果与铸件中实际的缺陷分布状况相吻合.分析了缺陷产生的原因,提出了工艺优化措施.     

基于FDM/FEM联合的铸件凝固过程热应力数值模拟的研究

为了模拟铸件凝固过程的热应力场，开发了基于华铸CAE（FDM）和ANSYS（FEM）联合的铸件凝固过程热应力场数值模拟集成系统，并计算了应力框试件的应力和位移。应力框的变形模拟与公认结果符合较好，实现了FDM／FEM联合进行铸件凝固过程的热应力数值模拟，为进一步模拟分析热应力和进行热裂预测奠定了一定的基础。     

铸件三维温度场及热应力场数值计算及实验研究

铸造系统凝固过程温度场、热应力场数值计算正在推动铸造业的发展。对铸件三维温度场、热应力场有限元模型进行分析,建立了基于ANSYS软件的铸件三维温度场及热应力场分析程序,并对应力框进行模拟,计算结果与实测值吻合。表明用数值计算法分析铸件凝固过程的温度场、热应力场是行之有效的。     

K418合金车用增压涡轮熔模铸造过程数值模拟及热裂预测

针对K418合金车用增压涡轮铸件极易出现热裂缺陷的现象,结合工厂实际生产条件,应用ProCAST铸造模拟软件对K418合金车用增压涡轮的充型过程、凝固时间以及凝固过程中的温度场、缩孔缩松形成过程和应力场进行了模拟。基于分析的结果,预测了涡轮中存在的热裂缺陷,模拟结果与实际生产情况吻合良好。分析结果表明,涡轮叶梢处容易产生热裂纹的主要原因是凝固过程中热应力不均引起的。     

铝合金电解阴极横梁凝固数值模拟及其应力分析

利用铸造仿真软件ProCAST对铝合金电解阴极横梁金属型铸造过程进行了数值模拟,得到其温度场和应力场;分析了倾斜浇注竖直凝固铸件的应力场及位移分布.模拟结果显示阴极横梁应力集中位置主要在其两端过渡凸台端面连接处区域;铝横梁的变形方式为在纵向方向上类似S型变形.通过对铸件凝固过程热应力数值模拟可以更好地预测铸件凝固过程中应力和变形的动态变化,为实际生产提供科学指导.     

基于有限差分法的铸件凝固过程热应力场数值模拟的研究

基于有限差分法（FDM）对铸件凝固过程执应力场进行了三维数值模拟研究，开发了基于微机和Windows平台的通用FDM／FDM铸件热应力场数值模拟原型系统。并采用典型应力框试件和实际铸件对所开发的系统进行了验证同叶进行了涤注试验。并测量了试件的残余应力。结果表明该系统可以用来模拟铸件残余应力的形成和预测热裂产生的倾向。对铸造应力应变分析与传热分析使用同一FD离散模型，避免了采用不同模型进行热—力耦合分析时的结点匹配问题，减小由此产生的单元温度载荷传递误差；同时使得流动场、温度场、应力场数值模拟统一于差分格式下。     

基于有限单元法的铸件热应力场数值模拟

重点论述了基于有限单元法(FEM)对铸件热应力场进行数值模拟的理论基础和实际方法,开发了基于有限单元法的铸造热应力场模拟程序.采用典型试件进行了算例验证,并与ANSYS的模拟结果及实际铸件浇注结果进行了对比,结果吻合.研究表明,开发的基于有限单元法的铸件热应力场数值模拟程序,模拟结果精确,运行可靠.     

大平板类铝合金壳体铸件铸造工艺优化与设计

针对大平板类铝合金壳体铸件的外形尺寸大、结构复杂等特点，通过三维温度场数值模拟来揭示铸件的凝固过程。根据准固态力学行为和流变行为，进行应力场模拟，进而预测铸件在凝固过程中产生缩松、缩孔以及热裂和变形等倾向，合理地实现了铸件的铸造工艺优化设计。     

基于MATLAB平台有限单元法的铸造热应力数值模拟

采用有限单元法(FEM)对铸件凝固过程热应力场进行了三维数值模拟研究,开发了基于MATLAB平台的FEM铸造热应力场模拟程序,采用典型应力框试件对所开发的算法和程序进行了算例验证,并与采用商品化软件ANSYS进行模拟的结果进行了对比,二者吻合良好.结果表明,所采用的算法及开发的程序能较好地预测铸件变形及热应力的集中位置.     

Using finite difference method to simulate casting thermal stress

Thermal stress simulation can provide a scientific reference to eliminate defects such as crack,residual stress centralization and deformation etc., caused by thermal stress during casting solidification. To study the thermal stress distribution during casting process, a unilateral thermal-stress coupling model was employed to simulate 3D casting stress using Finite Difference Method (FDM), namely all the traditional thermal-elastic-plastic equations are numerically and differentially discrete. A FDM/FDM numerical simulation system was developed to analyze temperature and stress fields during casting solidification process. Two practical verifications were carried out, and the results from simulation basically coincided with practical cases. The results indicated that the FDM/FDM stress simulation system can be used to simulate the formation of residual stress, and to predict the occurrence of hot tearing. Because heat transfer and stress analysis are all based on FDM, they can use the same FD model, which can avoid the matching process between different models, and hence reduce temperature-load transferring errors. This approach makes the simulation of fluid flow, heat transfer and stress analysis unify into one single model.     

镁合金薄壳压铸件充型凝固与热应力数值分析

以镁合金航空仪表壳为例,建立三维模型和有限差分模型,通过数值模拟镁合金薄壳在高压铸造过程中的充型温度场、凝固过程温度场及凝固过程应力场。分析模拟结果发现:在压铸过程中铸件局部温降梯度大的部分容易引起凝固过程的不一致,导致铸件局部应力过大,加大铸件的热裂倾向,通过分析结果预测铸件裂纹发生的区域,预测结果与实际情况吻合,并对原工艺提出相应的改进措施。     

热物性值对铸钢件温度场数值模拟计算精度的影响

本文研究了铸件和铸型的热物性值对铸钢件凝固过程温度场数值模拟精度的影响,指出铸型的热物性值较铸件的热物性值对模拟计算精度的影响更大。计算时,必须正确掌握不同铸造工艺条件下确切的热物性值。     

Modeling and simulation of 3D thermal stresses of large-sized castings in solidification processes

When heavy machines and large scaled receiver system of communication equipment are manufactured, it always needs to produce large- sized steel castings, aluminum castings and etc. Some defects of hot cracking by thermal stress often appear during solidification process as these castings are produced, which results in failure of castings.Therefore predicting the effects of technological parameters for production of castings on the thermal stress during solidification process becomes an important means. In this paper, the mathematical models have been established and numerical calculation of temperature fields by using finite difference method (FDM) and then thermal stress fields by using finite element method (FEM) during solidification process of castings have been carried out. The technological parameters of production have been optimized by the results of calculation and the defects of hot cracking have been eliminated. Modeling and simulation of 3D thermal stress during solidification processes of large-sized castings provided a scientific basis, which promoted further development of advanced manufacturing technique.     

Correlative thermal methodology for castability simulation of ductile iron in ADI production

The present paper investigates the simulation analysis of simultaneous mold filling and solidification of ductile iron casting in a permanent mold by virtue of its thermal characteristics. Thermal analysis was performed to determine the solidification behavior and nature of alloy of the melt during its solidification. It revealed the variation in the nature of alloy due to the variations in eutectic freezing and carbon equivalent of the melt. The obtained thermal parameters from the thermal analysis were further used for the casting simulation of the melt. The simulation results show a progressive solidification behavior of the casting. There is a significant decrease in the overall heat transfer coefficient with time during the solidification process. The simulation results were further verified experimentally. The experimental results show porosity defects at the top section of the casting. Two distinct zones (center and outer) were observed on the produced samples based on the average graphite nodule counts and average graphite nodule size.     

数值模拟技术在摇枕铸造工艺设计中的应用

利用数值模拟软件ZCAST,计算摇枕铸件充型和凝固过程中的速度场和温度场,发现铸造工艺设计过程中可能存在的问题.通过数值模拟研究和实践验证表明,采用数值模拟技术,可以有效提高铸造工艺设计的水平,减少或简化试验,对于提高铁路货车铸件结构和工艺设计质量以及节约研发成本都有着重要的指导意义.     

灰铸铁机床床身应力与变形的测试研究

利用数值模拟软件对铸件的充型、凝固过程及铸件内部热应力分布情况进行模拟分析。通过测试灰铸铁机床床身多个测点在热时效前后、加工前后及振动前后的残余应力值,发现残余应力随CE和Si/C比提高而降低;热时效能大幅度降低铸件残余应力,热时效温度越高,铸件残余应力降幅越大,且降温时段降温速度对残余应力有较大影响;加工会产生较大残余应力,热时效后进行其它时效对残余应力影响不大。     

铝合金铸件凝固过程效应力数值模拟

通过铝硅合金准固态力学行为和流变性能的测试，获得了该合金铸件凝固过程应力应变本构方程。并在此基础上开发了考虑材料高温力学性能，分析三维轴对称铸件凝固过程热粘弹塑性问题的热应力模拟程序，对带热节铝硅合金铸件的计算表明，计算结果与实验结果吻合较好。