锻造成形有限元数值模拟技术

数值模拟是目前塑性成形分析最有效的方法.通过有限元数值模拟,可以预测金属流动规律,获得应力场、应变场及温度场等场量分布及变化,进而揭示出复杂的变形机理.介绍锻造成形有限元法以及模拟中的关键技术,并以基于DEFORM软件的热-力耦合模拟实验为例,探讨了数值模拟技术在工程实际中的指导意义.     

Applying forming simulation to process and tooling designs for minimizing springback in split dowel manufacturing

In this study, FEA simulations were conducted to analyze the forming and springback of a split dowel forming process. Through 96 simulations, the best dimensional quality product from the current production tooling was obtained. However, it still cannot meet the customer’s geometrical requirement, so a metal finish process (secondary operation) is required. In order to minimize manufacturing cost and time, the secondary operation is not desired. Therefore, a new forming process and die design were developed through many iterative FEA simulations. This new design adds a short coin bead on the seam line area of the split dowel. It has been found that the springback amount is almost eliminated and the product quality exceeds the customer’s geometry requirement. Through this real industry case study, it is shown that FEA simulation can be used to not only optimize the current process but also design a new process and tooling.     

冷成形精密螺钉数值分析与工艺优化

利用有限元数值模拟仿真技术对精密微型螺钉的模具设计和成形工艺进行优化 ,对优化结果进行试验研究 ,并对成形缺陷进行金属学分析 ,讨论影响缺陷产生的因素 ,从理论上寻找缺陷产生的原因 ,从实践上印证理论分析和有限元模拟结果 ,最终得到可以消除裂纹和折叠缺陷的模具和工艺设计。     

线材热轧过程的三维热力耦合有限元模拟

运用有限元软件MSC.MARC及其接触分析技术,准确模拟了高速线材中轧区五道次热连轧过程.采用真实尺寸,计算并分析了轧制过程中的金属流动、轧制力、轧制力矩、应力、应变以及温度场等的变化规律,模拟结果为工艺参数的优化提供了依据,也对实际生产有重要的参考价值.     

汽车侧翼厢门外板成形模拟分析及工艺设计优化

针对汽车侧门外板在传统生产中需凭借经验大量反复试冲确定方案,造成生产成本过大的问题,采取塑性有限元方法,运用钣金成形数值模拟软件Dynaform进行成形参数优化.分别对模具底部圆角半径及拉深筋高度和排布进行优化,得到了一组工艺参数,并以此为依据进行生产实践,获得合格产品.为成形曲率不大钣金覆盖件在成形中如何有效避免拉深欠充分、拉裂问题提供工艺参考.     

Operation element-based efficiency for process plans and designs

In previous work the authors have developed graph-theoretic efficiency measures of process plans for rotational parts. The measures assess the technical efficiency under which a particular design can be manufactured, i.e. its manufacturability. This paper extends the earlier work by incorporating geometric dimensioning and tolerancing and developing a new technique for assessing the manufacturability of any part (prismatic and rotational). The aim is to develop an automated technique for assessing part designs.     

Numerical simulation of single particle acceleration process by SPH coupled FEM for abrasive waterjet cutting

The existing numerical simulations of hydrodynamic characteristics of abrasive waterjet in a cutting head were mainly based on Eulerian grid or arbitrary Lagrange–Eulerian grid method to establish computational fluid dynamics models. However, using these two methods, the abrasive and water were premixed and given an identical initial velocity, which were different from the mixing and acceleration processes of abrasive in the cutting head. This paper presents a more suitable numerical model that the abrasive particle enters into the mixing chamber in a low velocity and is accelerated in the focus tube by a high-speed waterjet from the orifice. In order to model this mixing-and-acceleration process of abrasive and high-speed waterjet, the smooth particle hydrodynamics (SPH) coupled finite element method (FEM) is adopted, in which SPH particles are used to model the high-speed waterjet to adapt its extremely large deformation and FEM is applied to model the discrete abrasive particle, cutting head, and workpiece. As a result, evolution of abrasive and waterjet velocities along focus tube is analyzed; trajectory of single abrasive particle in focus tube is sighted; the relationships between abrasive particle velocities and different water pressures are described; the rule of outlet velocities of abrasive particle vs. dimensionless ratio of diameter is conducted; depth of penetration caused by single abrasive particle impact is obtained. The current model is validated by the existing theoretical and experimental data.     

业务流程建模标注可配置建模技术

为了解决当前业务过程建模语言场景描述能力较差和模型执行时图元利用率低的问题,提出一种可配置的建模语言方案.基于图论及过程模型扩展途径的研究,通过建立可配置图元并为其增加可配置属性,对现有的过程建模语言BPMN进行可配置扩展.建立了基于控制流可配置的C-BPMN语言,并给出了该语言的形式化描述.通过给出C-BPMN的语法规则,验证了扩展后的可配置建模语言的成立条件.     

多传感器优化融合模型的理论与仿真研究

研究具有分层多级变结构、部分优化和FDIR功能的多传感器信息融合模型和算法.在进行系统理论分析和仿真试验时,以惯性/卫星/多卜勒/星光组合导航系统为对象进行了分层多级部分优化融合模型的仿真分析.仿真结果表明,应用优化算法进行融合后可使综合性能优于联邦滤波基本融合模型.     

喷射复合粉飞行燃烧过程中的温度场数值模拟

利用有限元方法,对自反应喷射成形制备Ti(C,N)-TiB2复合陶瓷坯件过程中单个喷射复合粉在火焰场中反应熔融的温度场变化过程进行了数值模拟研究.结果表明:粒径50μm的喷射复合粉粒子沿轴线进入火焰场0.35ms后,粒子表面温度即达到体系的引燃温度,复合粉开始发生自蔓延高温合成(Self-propagation High-temperature Synthesis,简称SHS)反应,此期间复合粉粒子升温速率约为2.82×106℃.s-1.反应开始后,受火焰加热与反应放热双重作用,复合粉粒子的升温速率进一步加快,之后由于复合粉粒子温度升高,超过火焰温度,并由吸热变为向外散热而使升温速率大幅下降(约为1.20×106℃.s-1),复合粉粒子在0.88ms后完成反应并达到最高温度2 920℃.反应结束后粒子由外向内快速冷却,在0.34ms后粒子表面达到复合陶瓷产物的理论共晶熔点2 620℃,之后粒子在一定过冷度下开始凝固,很快完全凝固成为陶瓷颗粒.喷射粒子在反应前、中、后阶段的温度场数值模拟结果与粒径约为50μm的喷射粒子在相应阶段的水淬熄实验结果相符较好.数值模拟结果基本体现了复合粉粒子在喷射过程中历经受热、反应放热及冷却凝固的热过程及相应的温度变化规律.     

板带热轧三维有限元热力耦合仿真分析

采用更新的Langrange方法及大变形热力耦合有限元法对热轧过程进行了热力耦合仿真分析,经过多道次轧制仿真后,得出了轧件的温度场和轧制力分布以及每道次轧件入口与出口温度大小及轧制力的大小,并进行了现场工业实验对仿真结果进行了验证,计算结果表明,仿真所得结果与实测结果误差很小,均在5%之内,从而证明模型是正确的,能够很好的运用于热轧过程的参数计算和研究,并对以后热轧工艺参数匹配规律研究以及板形控制研究提供重要的分析平台和起到重要的指导作用.     

电感耦合等离子体(ICP)深刻蚀的模型与模拟

为对交替复合深刻蚀过程进行工艺仿真,本文利用鞘层近似模型,以离子辅助刻蚀和直接粒子刻蚀的组合来实现交替复合深刻蚀过程中的刻蚀步骤,辅以各向同性钝化过程,对电感耦合等离子体深刻蚀（硅片）进行了建模.本文采用单一的二维廓线＂线算法＂模型实现对刻蚀材料的区分,进而实现了对电感耦合等离子体深刻蚀的二维模拟和三维带状显示.其优点是相比元胞及混合模型算法统一,运行效率高、速度快,且模拟结果与实验相比较为理想.     

An integrated framework of statistical process control and design of experiments for optimizing wire electrochemical turning process

Design of experiments (DOE) and statistical process control (SPC) have been separately used in many traditional and non-traditional machining processes, but recently these two approaches are being combined and reevaluated for more effective use and accurate conclusions. DOE and SPC are very efficient tools to maintain the process on target and within boundaries of natural variations and to achieve the maximum accuracy and effectiveness of an experimental program. This paper proposes an integrated framework of SPC and DOE to execute the experimental procedures and to investigate a reliable mathematical model for optimizing the wire electrochemical turning process (WECT). WECT is a non-traditional machining process which has tremendous applications in modern industries especially in the aerospace and military industries. Response surface methodology is used to determine the sufficient number of experiments and also the recommended values of the input parameters. Univariate and multivariate control charts are used to assess the statistical control of the output parameters. Multi-objective optimization is conducted for determining the optimum values of the input parameters.     

Triboengineering properties of composite coating sputtered with vacuum plasma techniques

The triboengineering behavior of polymeric and carbon composite coatings deposited from the active gas phase is considered. The alloying of diamond-like coatings with titanium or copper reduces the wear of the counterbody tenfold and improves the durability of the coating itself. It is demonstrated that the introduction of nanoparticles of polymers of different origin, metals, or carbon, into the polymeric layer reduces the friction coefficient and promotes wear resistance.     

玻璃器皿压制成型的建模与仿真

玻璃器皿的压制成型过程是一个非常复杂的热力耦合弹塑性变形过程,其具有材料非线性和几何非线性的大变形特征。在对玻璃材料进行了传热分析以及受力分析等理论分析的基础上,利用专业有限元CFD软件GAMBIT进行有限元建模;利用POLYFLOW对玻璃器皿压制过程中的温度场、应力场进行有限元数值模拟,得到玻璃熔体和凸凹模的温度分布及应力分布图;最后利用FIELD-VIEWER显示模拟结果,并结合实际对其结果进行分析,以期为优化产品及模具的设计、提高产品的质量提供参考和指导。     

Design and simulation of dust extraction for composite drilling

Due to its high strength-to-weight ratio, composite materials have been widely applied in aerospace manufacturing. However, some challenges are facing in fabrication and assembly of the parts with composite materials. One of them is how to collect the dwarf and dust generated from the drilling operation, especially in an open environment when the composite parts are assembled, since a large number of holes need generating to rivet the parts together when the parts with composite materials are assembled in an aircraft structure. The efficiency of dust extraction is crucial to the healthy operating environment and the quality of the assembled component. In this paper, three conceptual designs of automatic dust extraction are proposed and compared, and the best design with the hood fastened on the drilling spindle has been selected and analyzed. Its design parameters have been identified; a systematic procedure has been proposed for the design optimization; the process of the dust extraction has been modeled and simulated using the COSMOSFloWorks. Taguchi method is applied to optimize the design. The process of the dust extraction has been validated through animation.     

Collaborative simulation method with spatiotemporal synchronization process control

When designing a complex mechatronics system, such as high speed trains, it is relatively difficult to effectively simulate the entire system’s dynamic behaviors because it involves multi-disciplinary subsystems. Currently, a most practical approach for multi-disciplinary simulation is interface based coupling simulation method, but it faces a twofold challenge: spatial and time unsynchronizations among multi-directional coupling simulation of subsystems. A new collaborative simulation method with spatiotemporal synchronization process control is proposed for coupling simulating a given complex mechatronics system across multiple subsystems on different platforms. The method consists of 1) a coupler-based coupling mechanisms to define the interfacing and interaction mechanisms among subsystems, and 2) a simulation process control algorithm to realize the coupling simulation in a spatiotemporal synchronized manner. The test results from a case study show that the proposed method 1) can certainly be used to simulate the sub-systems interactions under different simulation conditions in an engineering system, and 2) effectively supports multi-directional coupling simulation among multi-disciplinary subsystems. This method has been successfully applied in China high speed train design and development processes, demonstrating that it can be applied in a wide range of engineering systems design and simulation with improved efficiency and effectiveness.     

制造过程管理仿真技术的研究

在制造企业实施过程管理包括BPP成功率很低的情况下，寻找一种有效的分析评价工具或手段来提高制造企业实施过程管理包括BPP的成功率是制造领域所关心的热门话题之一，过程仿真作为一种新兴的技术可以用来帮助理解、分析、优化制造过程，可帮助制造企业提高实施过程管理的成功率，是制造企业实施过程管理的理想工具。本文首先系统地讨论了过程仿真和过程建模的区别，分析研究了制造过程的特点，提出了进行制造过程仿真的策略、处理方法、基本原理及一般步骤，最后结合实例分析讨论了如何在制造企业中应用现有的过程仿真技术(工具)来进行过程仿真，描述评价和改进制造过程。     

General geometric modelling approach for machining process simulation

Machining process simulation systems can be used to verify NC (numerically controlled) programs as well as to optimise the machining phase of the production. These systems contribute towards improving the reliability and efficiency of the process as well as the quality of the final product. Such systems are particularly needed by industries dealing with complex cutting operations, where the generation of NC code represents a very complex and error-prone task. A major impediment to implementing these systems is the lack of a general and accurate geometric method for extracting the required geometric information. In this paper, a novel approach to performing this task is presented. It uses a general and accurate representation of the part shape, removed material, and cutting edges, and can be used for any machining process. Solid models are used to represent the part and removed material volume. Bezier curves (in 3D space) are used to represent cutting edges. It is shown that by intersecting the removed material volume with the Bezier curves, in-cut segments of the tool cutting edges can be extracted. Using these segments, instantaneous cutting forces as well as any other process parameters can be evaluated. It is also shown that by using B-rep (Boundary representation) polyhedral models for representing solids, and cubic Bezier curves for representing cutting edges, efficient, generic procedures for geometric simulation can be implemented. The procedure is demonstrated and verified experimentally for the case of ball end-milling. A very good agreement was found between simulated cutting forces and their experimental counterparts. This proves the validity of the new approach.Notation cx ₃,cx ₂,cx ₁,cx ₀ parameters of cubic polynomialx(t) - cy ₃,cy ₂,cy ₁,cy ₀ parameters of cubic polynomialy(t) - cz ₃,cz ₂,cz ₁,cz ₀ parameters of cubic polynomialz(t) - bx _i ,by _i ,bz _i x-,y-, andz-coordinates of ith control point, respectively - b _i ith control point - R tool radius (m) - angular position of point on cutting edge measured from positivex-axis in case of flat end mill (°) - helix angle of cutting edge on flat end mill (°) - A, B, C, D parameters of the equation of a plane - td _i ,tu _i lower end and upper end of theith in-cut segment (before updating) - n number of in-cut segments (before updating) - td _j ,tu _j lower end and upper end of theith in-cut segment (after updating) - m number of in-cut segments (after updating) - dF _t , dF _r tangential and radial components of the infinitesimal cutting force (N) - K _t ,K _r empirical constants in tangential force and radial force equations (N/m²) - b thickness of axial infinitesimal element of cutting edge (m) - h instantaneous chip thickness of axial infinitesimal element of cutting edge (m) - _s shear strength of workpiece (N/m²) - dA _c cross-section area of undeformed chip on the infinitesimal element of cutting edge (m²) - shear angle (°) - _e effective rake angle (°) - friction angle (°) - or (t) angular position of point on cutting edge of ball nose of ball end mill (rad) - u _j , d _j lower end and upper end ofjth in-cut segment (rad) - t parameter