DEFORMATION ANALYSIS OF SHEET METAL SINGLE-POINT INCREMENTAL FORMING BY FINITE ELEMENT METHOD SIMULATION

Single-point incremental forming （SPIF） is an innovational sheet metal forming method without dedicated dies, which belongs to rapid prototyping technology. In generalizing the SPIF of sheet metal, the deformation analysis on forming process becomes an important and useful method for the planning of shell products, the choice of material, the design of the forming process and the planning of the forming tool. Using solid brick elements, the finite element method（FEM） model of truncated pyramid was established. Based on the theory of anisotropy and assumed strain formulation, the SPIF processes with different parameters were simulated. The resulted comparison between the simulations and the experiments shows that the FEM model is feasible and effective. Then, according to the simulated forming process, the deformation pattern of SPIF can be summarized as the combination of plane-stretching deformation and bending deformation. And the study about the process parameters＇ impact on deformation shows that the process parameter of interlayer spacing is a dominant factor on the deformation. Decreasing interlayer spacing, the strain of one step decreases and the formability of blank will be improved. With bigger interlayer spacing, the plastic deformation zone increases and the forming force will be bigger.

Application of SSOR-PCGM with improved iteration format in FEM simulation of massive concrete

In this study, for the purpose of improving the efficiency and accuracy of numerical simulation of massive concrete, the symmetric successive over relaxation-preconditioned conjugate gradient method （SSOR-PCGM） with an improved iteration format was derived and applied to solution of large sparse symmetric positive definite linear equations in the computational process of the finite element analysis. A three-dimensional simulation program for massive concrete was developed based on SSOR-PCGM with an improved iteration format. Then, the programs based on the direct method and SSOR-PCGM with an improved iteration format were used for computation of the Guandi roller compacted concrete （RCC） gravity dam and an elastic cube under free expansion. The comparison and analysis of the computational results show that SSOR-PCGM with the improved iteration format occupies much less physical memory and can solve larger-scale problems with much less computing time and flexible control of accuracy.

Numerical simulation and response analysis of microspherical focused logging in inclined micro-fractured formation

Tight and unconventional reservoirs have become the focus with the progress of petroleum exploration and development.Micro-fractures in these reservoirs can effectively improve reservoir permeability,and well-developed micro-fractures can serve to directly improve productivity.Compared with the centered electrical well logging method,the Micro Spherical Focused Logging(MSFL)is more suitable for microfracture identification due to its high resolution and near borehole wall measuring method.In this study,an anisotropic model is used to depict micro-fractured formation.First,a forward model with microfractured formation,borehole,logging instrument and surrounding rock is established.Subsequently,MSFL responses under different micro-fracture porosity,resistivity,dip angle and borehole radius,are calculated based on the finite element method(FEM).Finally,the MSFL responses under different microfracture parameters are analyzed with the response laws clarified.

Contrast of FEM and FVM in simulation of complex aluminum extrusion

Extrusion is the key technology to manufacture aluminum profiles and involves complicate metal deformation coupled with temperature changes. The choice of numerical technique plays an important role and is related to the accuracy and effectiveness of extrusion process analyses. In this paper, the extrusion processes of two complex aluminum profiles are simulated with FEM and FVM respectively. The merit and disadvantage of these two methods are analyzed. The finite element method exhibits higher calculation efficiency in the simulation of a lock catch extrusion process. However, due to frequent rezoning in simulation of complex extrusion process, sharp distortion of finite element mesh can decrease computational accuracy. Therefore the volume loss in FEM simulation is larger than that in FVM simulation by five percent. Based on Euler description, the finite volume method employs structured element mesh covering entire material flowing area, which makes it more robust in the simulation of complicate extrusion process. The deformation configuration with FVM is much smoother than that with FEM in the extrusion simulation of a thin-walled aluminum profile, although FVM requires more computation time.

ALE FINITE ELEMENT ANALYSIS OF NONLINEAR SLOSHING PROBLEMS BASED ON F LUID VELOCITY POTENTIAL

Base d on fluid velocity potential, an ALE finite element formulation for the analysi s of nonlinear sloshing problems has been developed. The ALE kinemat ical description is introduced to move the computational mesh independently of f luid motion, and the container fixed noninertial coordinate system is employed to establish the governing equations so that the mesh is needed to be updated in this coordinate system only. This leads to a very simple mesh moving algorithm which makes it easy to trace the motion of the moving boundaries and the free su rface without producing undesirable distortion of the computational mesh. The fi nite element method and finite difference method are used spacewise and timewise , respectively. A numerical example involving either forced horizontal oscillati on or forced pitching oscillation of the fluid filled container is presented to illustrate the effectiveness and the robustness of the method. In additi on, this work can be extended for the fluid structure interaction problems.

COUPLED NUMERICAL SIMULATION ON COLD ROLLER'S TEMPERATURE FIFLD-PHASE TRANSFORMATION - STRESS FIELD DURING ITS QUENCHING PSOCESS

Complicated changns occur inside the steel parts during quenching process. The abruptly changed boundary conditions make the temperature field,micro - structure and stress field change dramatically in very short time, and these variables take a contact interactions in the whole process. In this paper, a three dimensional non - linear mathematical model for queeching process has been founded and the numerical simulation on temperature field,microstructre and stress field has been realized.In the FEM analysis, the incremental iteration method is used to deal with such complicated nonlinear as boundary nonlinear, physical property nonlinear,transformation nonlinear etc.The effect of stress on transformation kinetics has been considered in the calculation of microstructure. In the stress field anal- ysis,a thermo- elasto - plastic model has been founded, which considers such factors as transforma- tion strain,transformation plastic strain, themal strain and the effect of temperature and transforma- tion on mechanical propertier etc. The transient temperature field, microstructure distribution and stress field of the roller on any time can be displayed vividly,and the cooling curve and the changes of stress on any position can also be given.

Numerical simulation on the microstress and microstrain of low Si-Mn-Nb dual-phase steel

According to the stress-strain curves of single-phase martensite and single-phase ferrite steels,whose compositions are similar to those of martensite and ferrite in low Si-Mn-Nb dual-phase steel,the stress-strain curve of the low Si-Mn-Nb dual-phase steel was simulated using the finite element method（FEM）.The simulated result was compared with the measured one and they fit closely with each other, which proves that the FE model is correct.Based on the FE model,the microstress and microstrain of the dual-phase steel were analyzed. Meanwhile,the effective factors such as the volume fraction of martensite and the yield stress ratio between martensite and ferrite phases on the stress-strain curves of the dual-phase steel were simulated,too.The simulated results indicate that for the low Si-Mn-Nb dual-phase steel, the maximum stress occurs in the martensite region,while the maximum strain occurs in the ferrite one.The effect of the volume fraction of martensite（fm） and the yield stress ratio on the stress-strain curve of the dual-phase steel is small in the elastic part,while it is obvious in the plastic part.In the plastic part of this curve,the strain decreases with the increase of f_M,while it decreases with the decrease of the yield stress ratio.

Numerical simulation of the dual laterolog for carbonate cave reservoirs and response characteristics

Cave carbonate formations are characterized by heterogeneity, which makes electrical log prediction difficult. It is currently important to know how to use the dual laterolog to accurately identify and quantitatively evaluate caves. Using numerical simulation to calculate electrical log responses can provide a theoretical basis for cave identification and evaluation. In this paper, based on the dual laterolog principles, we first study different size spherical cave models using the finite element method （FEM）, determine a relation between resistivity and cave filling after comprehensively studying the log responses of cave models with different filling material, and finally study the dual laterolog responses on caves filled with shale, limestone, conglomerate, and thin laminated formation of sand and shale. The numerical results provide a theoretical basis for identification and evaluation of carbonate cave reservoirs.

Numerical Simulation on the Resistance Performance of Ice-Going Container Ship Under Brash Ice Conditions

Ice resistance prediction is a critical issue in the preliminary design of ships navigating brash ice conditions, which is closely related to the safety of a ship to navigate encounter brash ice, and has significant effects on the kinds of propellers and motor power needed. In research on this topic, model tests and full-scale tests on ships have thus far been the primary approaches. In recent years, the application of the finite element method(FEM) has also attracted interest. Some researchers have conducted numerical simulations on ship–ice interactions using the fluid–structure interaction(FSI) method. This study used this method to predict and analyze the resistance of an ice-going ship, and compared the results with those of model ship tests conducted in a towing tank with synthetic ice to discuss the feasibility of the FEM. A numerical simulation and experimental methods were used to predict the brash ice resistance of an ice-going container ship model in a condition with three concentrations of brash ice(60%, 80%, and 90%). A comparison of the results yielded satisfactory agreement between the numerical simulation and the experiments in terms of both observed phenomena and resistance values, indicating that the proposed numerical simulation has significant potential for use in related studies in the future.

基于HCT-FEM和3D电磁模型的SAW滤波器性能仿真系统

该文基于分层级联有限元(HCT-FEM)和三维电磁模型构建了一套声表面波(SAW)滤波器性能仿真系统。采用Matlab协同COMSOL建立的HCT-FEM模型计算声学元件导纳,用ANSYS建立的三维电磁模型计算含芯片走线、引线/金属球、封装外壳及测试电路的外部电磁S参数,并在ADS软件中对SAW滤波器频率响应进行复原。将该系统应用于一款芯片级封装(CSP)的普通SAW滤波器和一款表贴封装(SMD)的单晶薄膜SAW滤波器电性能仿真,仿真与实测结果吻合较好。

Numerical Simulation of Projection Welding Processes for Door Hinge of Automobile Based on Coupled Fields Analysis

Projection welding is a variation of electric resistance welding with the dynamic changes of the flow paths for heat and electrical properties with changing temperature caused by the large plastic deformation collapse of projection. As the joint type between the auto door hinge and the inner plate, projection welding may bring welding distortions and would affect the assembly quality of auto body. A comprehensive electric-thermal-mechanical numerical simulation was performed to quantitatively simulate the processes of projection welding by using a coupled finite element method. The mechanism of projection collapse and the formation process of nugget were discussed and good conclusions have been achieved comparing with the test results.

电磁计算与电磁工业软件

概要介绍了电磁计算与电磁工业软件的研究进展。1)介绍了电磁计算方法的研究进展,对解析方法、高频近似方法、全波计算方法、快速计算方法,以及近年发展起来的混合方法进行了阐述;2)概述了基于时域有限差分方法(FDTD)、有限元法(FEM)、矩量法(MoM)等全波计算方法的3款国际主流商业电磁计算软件的特点和发展历程;3)介绍了我国具有自主知识产权的“摇光”高频电磁工业软件的算法体系、软件功能以及实际应用情况;4)对电磁计算与电磁工业软件的未来发展进行了总结和展望。

基于LSTM的勘察器外壁温度反演方法研究

对于星壤物质物化特性的反演是深空探测中最重要的一环,星壤的热导率、热容参数等热特性是研究星壤组成的科学依据,而温度测量是基于侵彻式的星壤原位探测的重要参数。针对月壤勘察器侵彻过程的外表面温度无法直接测量的问题,开展了基于LSTM神经网络算法的勘察器外表面温度反演方法的研究。借助ANSYS/LS-DYNA有限元软件实现侵彻过程的仿真模拟以获取多组勘察器弹头部内外表面温度数据,依据有限差分法离散热传导方程选取数据,采用长短期记忆神经网络来建立反演模型。通过模拟实验进行分析,该方法反演所得曲线和实验曲线相比均方根误差为12.9℃,最大相对误差不超过10%。实验结果表明本文所研究的方法可以实现勘察器外表面温度的反演。

基于离散元与有限元耦合的料斗衬板磨损分析

针对转运系统转载物料过程中料斗衬板的磨损影响运输效率的问题,改用新型钢基陶瓷复合衬板来代替传统耐磨钢,采用离散元法(distinct element method,DEM)描述颗粒物料运动过程,通过Archard磨损模型分析预测不同工况条件下衬板磨损规律,并通过磨损规律和磨损特征验证了磨损模型的合理性。基于DEM的有限元法(finite element method,FEM)耦合方法分析了衬板应力与变形特性。研究结果表明:料斗衬板的最大磨损深度随颗粒度增大而减小,随传送带带速、衬板安装高度、衬板安装倾角的增大而增大。结合实际来看,衬板在粒径25mm、带速2.8m/s、高度3000mm、角度60°的工况下磨损最小。铁矿石散料对衬板的摩擦和冲击作用造成的应力较大的位置主要集中在衬板连接的螺栓孔周围,磨损最严重的位置多为颗粒与衬板优先接触区域,因此,为了降低应力集中,应该在衬板连接处加强螺栓孔的强度并进行圆角设计。

基于3D几何特征深度表达学习的物理系统仿真

针对现有深度学习方法在物理系统仿真中无法处理几何边界与初始条件同时变化的场景的问题,提出将几何边界约束的表达与物理系统仿真解耦的技术思路,设计了几何特征表达学习和物理系统仿真双步骤的技术路线。在构建与外部物理条件无关的几何特征提取模块之后,融合提取的几何特征与物理特征,最后设计基于神经网络的物理系统仿真方法。在应力场预测实验中,所提方法的预测时间为2.63 ms,远低于有限元法(FEM)的0.6 s,且平均绝对误差(MAE)仅为MeshNet的0.389倍。实验结果表明,所提方法能够保持较高仿真精度,同时能够较好地适应不同的几何边界与初始条件。

基于有限元法的水下航行器地磁异常模拟研究

为改进水下航行器磁异常探测技术中磁异常实测数据难获得、现有磁体模型计算精度不高等问题,基于有限元仿真探讨建立无需区分近、远场的高精度混合磁体模型方法。应用有限元数值方法仿真复杂结构水下航行器的空间磁异常分布,以磁场数值解为收敛目标,建立以偶极子阵元数目、位置及磁矩为参数的均匀磁化椭球体与偶极子阵列混合的航行器磁异常解析模型,采用非线性最小二乘算法求解模型系数。仿真结果表明,基于该模型得到磁异常计算值与全空间内数值解的拟合度较高,测试平面平均误差为3%。该模型在磁场延拓、高精度建模等方面可以进一步应用。

基于FDM/FEM的挤压铸造收缩缺陷数值模拟

建立了模拟挤压铸造凝固过程中收缩缺陷形成的有限差分/有限元计算模型,该模型包括了凝固过程中的潜热释放和体积收缩效应。在温度场模拟中采用了交替隐式算法,在应力场模拟中采用了热粘弹塑性本构模型。为验证模型的正确性,对A356铝合金挤压铸造凝固过程进行了模拟计算,模拟结果与实验结果一致。

Galerkin-based quasi-smooth manifold element(QSME)method for anisotropic heat conduction problems in composites with complex geometry

The accurate and efficient analysis of anisotropic heat conduction problems in complex composites is crucial for structural design and performance evaluation. Traditional numerical methods, such as the finite element method(FEM), often face a trade-off between calculation accuracy and efficiency. In this paper, we propose a quasi-smooth manifold element(QSME) method to address this challenge, and provide the accurate and efficient analysis of two-dimensional(2D) anisotropic heat conduction problems in composites with complex geometry. The QSME approach achieves high calculation precision by a high-order local approximation that ensures the first-order derivative continuity.The results demonstrate that the QSME method is robust and stable, offering both high accuracy and efficiency in the heat conduction analysis. With the same degrees of freedom(DOFs), the QSME method can achieve at least an order of magnitude higher calculation accuracy than the traditional FEM. Additionally, under the same level of calculation error, the QSME method requires 10 times fewer DOFs than the traditional FEM. The versatility of the proposed QSME method extends beyond anisotropic heat conduction problems in complex composites. The proposed QSME method can also be applied to other problems, including fluid flows, mechanical analyses, and other multi-field coupled problems, providing accurate and efficient numerical simulations.

基于力学响应的碳纤维夹层结构可设计性的应用分析

碳纤维夹层结构以轻质高强度和耐腐蚀特性广泛应用航空航天领域。提出一种以最优力学响应特性为目标,对碳纤维铺层角度进行设计,利用有限元分析软件进行仿真验证的设计方法。结果表明,文中方法可充分利用碳纤维夹层结构可设计性,为电子产品结构设计提供参考。

ETAP软件在孟加拉国帕德玛水厂项目的电气设计应用

以孟加拉国帕德玛水厂项目电气设计中ETAP软件的工程应用为例,针对海外工程设计工作遇到的当地供电电网供电质量较差、电压波动较大,气候环境严苛,操作人员技术水平低下的现实情况,设计院需要一套国际业主认可的电力电气综合分析系统,以计算机仿真与分析方法代替传统的人工计算和设计工作,提高设计效率,节省人工时,确保按时高质量履约。介绍了该海外给水项目中取水泵站、净水厂、加压泵站3个场站的电气设计和仿真计算。总结了工程中电气设计的主要应用成果,对今后市政行业电气工程应用ETAP完成仿真计算起到推广和借鉴作用。