Modeling and simulation of material removal in planarization process

In planarization processes, material removal analysis is essential to the estimation of the wear rate and non-uniformity. A model that describes the material removal of a pad with rough surface grinding by using abrasive grains is developed. A collection of micro-contact spots is identified and the deformation approach is subsequently calculated. Elastic-plastic theory and the wear model are used to construct the expression for the magnitude of material removal as a function of the indentation depth. First, the indentation depth of micro-contact spots in the asperity of the pad and the deformation of the flat part of pad are obtained by using elastic-plastic theory. Then, the material removal caused by individual micro-contacts is calculated with the help of wear theory. Finally, the macroscopic wear volume is found by summing the volumetric wear of each individual micro-contact. Moreover, the pad dressing process is introduced to demonstrate the developed model for material removal. A parametric study is conducted to explore the influence on the material removal results and the planarization interfacial phenomena of operational parameters. These parameters compose of the applied down force, rotational speed of dresser, and the density of abrasive grains. The results provide a detailed picture of the interface phenomena and yield an insight into the physical effects of the operating parameters in the planarization processes.     

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。     

Modeling and simulation of magnetic abrasive finishing process

Magnetic abrasive finishing (MAF) is one of the advanced finishing processes, which produces a high level of surface quality and is primarily controlled by a magnetic field. In MAF, the workpiece is kept between the two poles of a magnet. The working gap between the workpiece and the magnet is filled with magnetic abrasive particles. A magnetic abrasive flexible brush (MAFB) is formed, acting as a multipoint cutting tool, due to the effect of the magnetic field in the working gap. This paper deals with the theoretical investigations of the MAF process. A finite element model of the process is developed to evaluate the distribution of magnetic forces on the workpiece surface. The MAF process removes a very small amount of material by indentation and rotation of magnetic abrasive particles in the circular tracks. A theoretical model for material removal and surface roughness is also proposed accounting for microcutting by considering a uniform surface profile without statistical distribution. Numerical experiments are carried out by providing different routes of intermittent motion to the tool. The simulation results are verified by comparing them with the experimental results available in the literature.     

Modeling and simulation of magnetic abrasive finishing process

Magnetic abrasive finishing (MAF) is one of the advanced finishing processes, which produces a high level of surface quality and is primarily controlled by a magnetic field. In MAF, the workpiece is kept between the two poles of a magnet. The working gap between the workpiece and the magnet is filled with magnetic abrasive particles. A magnetic abrasive flexible brush (MAFB) is formed, acting as a multipoint cutting tool, due to the effect of the magnetic field in the working gap. This paper deals with the theoretical investigations of the MAF process. A finite element model of the process is developed to evaluate the distribution of magnetic forces on the workpiece surface. The MAF process removes a very small amount of material by indentation and rotation of magnetic abrasive particles in the circular tracks. A theoretical model for material removal and surface roughness is also proposed accounting for microcutting by considering a uniform surface profile without statistical distribution. Numerical experiments are carried out by providing different routes of intermittent motion to the tool. The simulation results are verified by comparing them with the experimental results available in the literature.     

酮苯脱蜡溶剂回收系统模型与仿真

本文从酮苯脱蜡溶剂回收系统机理分析出发,建立了三级蒸发系统的实用机理模型。用实际数据对模型进行了校验和仿真,结果表明模型是合理和有效的。     

Modeling and numerical simulation of multi-gripper flexible stretch forming process

Multi-gripper flexible stretch forming (MGFSF) is a recent technological innovation of sheet metal forming process. Straight jaws in traditional stretch forming machines are substituted for a pair of opposed clamping mechanisms movable relative to each other during the forming process. In this paper, spherical part is selected as the study object, and numerical simulations of the MGFSF process under two representative loading paths of horizontal-vertical (HV) loading path and horizontal-tilting-vertical (HTV) loading path have been carried out using a commercially available FEM software (ABAQUS). Four levels of horizontal forces in HV loading path are selected to investigate their influences on strain and forming error distributions of the simulated parts. In addition, four levels of tilting forces in HTV loading path are also taken into consideration. The simulation results reveal that HV loading path would result in a larger strain but a smaller forming error in the forming zone. In contrast, HTV loading path would result in a smaller strain but a larger forming error in the forming zone. Finally, experimental validations are conducted on self-developed apparatus, and the experimental results show a good correlation with the simulation results.     

曲面铝合金锤击平整技术研究

以曲面铝合金为例,利用工业机器人锤击的方式对曲面类零件表面进行平整,并探究各锤击工艺参数对其表面的粗糙度、硬度及表面形貌的影响.将锤击装置装夹到工业机器人上,控制工业机器人以矩形光栅式运动路径对曲面铝合金表面进行锤击加工,并对锤击后表面的粗糙度、硬度及表面形貌进行测量观察.结果表明:经锤击加工后的铝合金表面粗糙度可达0...     

虚拟数控加工过程物理仿真模型的研究

首先阐述了虚拟数控加工过程物理仿真的迫切要求及其内容体系,重点论述了近些年国内外所建立的切削力、刀具磨损与变形、加工误差、颤振和切屑形戍过程仿真的数学模型.最后就物理仿真今后的研究方向提出了四点建议.     

轿车车身冲压生产线加工过程的建模与仿真

轿车车身冲压生产线的加工过程仿真是采用虚拟制造技术对现代轿车车身冲压生产线进行研究的组成部分。这里以一条具体的冲压生产线为例对加工过程仿真的总体流程及各个步骤环节进行了研究,阐述了加工过程仿真的关键技术。仿真采用Pro/ENGINEER造型软件和UltraSpot仿真软件。     

Modeling and simulation of cold rolling process for double groove ball-section ring

Double groove ball-section ring (DGBR) is an important part of bearing rings. Cold DGBR rolling is an advanced continuous and local plastic forming technique by reducing cross section and increasing the diameter of ring blanks between rotating roll, and can directly obtain the DGBR with good mechanical properties. In this paper, the cold DGBR rolling processes from some initially rectangular blanks are investigated by using 3D-FE numerical simulation to reveal its deforming rules. Firstly, by analyzing the dimension relationship between rectangular blank and deformed ring, a new blank size design method is proposed based on rolling ratio and the volume conservation law, and thus a series of different original blanks can be precisely designed under different rolling ratios for a same final required DBGR. Secondly, under the ABAQUS/Explicit software environment, a reliable guide roll adaptive control-based 3D-FE model for cold DGBR rolling process is built via elastic–plastic dynamic explicit finite element method. Finally, several rectangular blanks are designed under different roll ratios and the deforming behaviors of cold DGBR rolling process are investigated with thorough numerical simulation. The results show that: (1) the maximum radial thickness of ring H reduces firstly slowly and then rapidly after the ball groove achieves its final shape; (2) the diameters of the ring expand gradually during the whole process and no sudden change occurs just when the final shape of the ball groove is completely formed; (3) the largest deformation occurs around the ball groove all the time under small rolling ratio; while under large rolling ratio, it occurs first around the ball groove and then gradually transfers to the ring outer surface; and (4) the inhomogeneous deformation degree increases with the progress of the process, and for final parts, it increases slowly first with the increasing of roll ratio and then fast when the roll ratio is greater than a certain value. These results will not only reveal the forming mechanisms of cold DGBR rolling process but also provide a basis to blank optimum design and process adaptive control of the relevant profiled ring rolling processes.     

Developing a neural network-based run-to-run process controller for chemical-mechanical planarization

A new neural network-based run-to-run process control system (NNRtRC) is proposed in this article. The key characteristic of this NNRtRC is that the linear and stationary process estimator and controller in the exponentially weighted moving average (EWMA) run-to-run control scheme are replaced by two multilayer feed-forward neural networks. An efficient learning algorithm inspired by the sliding mode control law is suggested for the neural network-based run-to-run controller. Computer simulations illustrate that the proposed NNRtRC performs better than the EWMA approach in terms of draft suppression and adaptation to environmental change. Experimental results show that the NNRtRC can precisely trace the desired target of material removal rate (MRR) and keep the within wafer non-uniformity (WIWNU) in an acceptable range.     

Developing a neural network-based run-to-run process controller for chemical-mechanical planarization

A new neural network-based run-to-run process control system (NNRtRC) is proposed in this article. The key characteristic of this NNRtRC is that the linear and stationary process estimator and controller in the exponentially weighted moving average (EWMA) run-to-run control scheme are replaced by two multilayer feed-forward neural networks. An efficient learning algorithm inspired by the sliding mode control law is suggested for the neural network-based run-to-run controller. Computer simulations illustrate that the proposed NNRtRC performs better than the EWMA approach in terms of draft suppression and adaptation to environmental change. Experimental results show that the NNRtRC can precisely trace the desired target of material removal rate (MRR) and keep the within wafer nonuniformity (WIWNU) in an acceptable range.     

Modeling and simulation of polymer melts flow in the extrusion process of plastic profile with metal insert

The extrusion technology of plastic profile with metal insert is recently an advanced plastic processing method whose products keeps rising today for their excellent performance. However, the related fundamental research on polymer forming mechanism in the extrusion process of plastic profile with metal insert is lagging behind. With the development of computational fluid dynamics (CFD) theory, numerical method becomes an effective way to investigate such complex material forming problems as in the polymer extrusion process. In the present study, the mathematical model for three-dimensional non-isothermal viscous flow of the polymer melts obeying a Carreau model is developed based on the CFD theory. The Williams–Landel–Ferry equation is employed to involve the temperature dependence of material parameters. A decoupled numerical algorithm based on the penalty finite element method is conducted to predict the rheological behaviors of polymer melts within the complex flow channel. The streamline upwind/Petrov–Galerkin scheme is employed to improve the computational stability for the calculation of temperature field. Based on the theoretical model, the essential flow characteristics of polymer melts in the extrusion process of plastic profile with metal insert is investigated. The distributions of principal field variables like flow velocity, melt temperature, flow stress and pressure drop are predicted. The effects of die structure parameters including the intake angle and the distribution section length upon the melts flow patterns are further discussed. The variations of melt rheological properties versus different processing conditions like the volume flow rate and the metal insert moving velocity are also investigated. Some advice on practical processing operations of the extrusion process of plastic profile with metal insert is accordingly put forward based on the numerical results.     

Effect of conditioner load on the polishing pad surface during chemical mechanical planarization process

During the Chemical mechanical planarization (CMP), the pad conditioning process can affect the pad surface characteristics. Among many CMP process parameters, the improper applied load on the conditioner arm may have adverse effects on the polyurethane pad. In this work, we evaluated the pad surface properties under the various conditioner arm applied during pad conditioning process. The conditioning pads were evaluated for surface topography, surface roughness parameters such as Rt and Rvk and Material removal rate (MRR) and within-wafer non-uniformity after wafer polishing. We observed that, the pad asperities were collapsed in the direction of conditioner rotation and blocks the pad pores applied conditioner load. The Rvk value and MRR were founded to be in relation with 4 > 1 > 7 kgF conditioner load. Hence, this study shows that, 4 kgF applied load by conditioner is most suitable for the pad conditioning during CMP.

     

机器人贴装涂胶过程建模与时序分析

空间太阳电池帆板的贴装生产过程目前在国内依旧采用单一手工操作,很难保证质量.该文对太阳电池帆板自动贴装机器人的涂胶过程进行了流动特性建模与时序状态分析,确定了机器人单片涂胶周期和串联涂胶周期,得到了机器人任一涂胶拐点处的时序值,及任意时刻机器人对应的涂胶位置坐标.通过对机器人的涂胶过程分析,得到了针管内胶体流动的速度场模型,并确定了胶体流量算式,给出了不同变量条件下涂胶过程的速度场模型及涂胶流量模型,为空间太阳帆板的自动贴装涂胶生产提供了可靠的数据模型.     

分件供送变螺距螺杆的建模与仿真

给出了四段组合式变螺距螺旋线的数学模型,提出了一种绘制变螺距螺杆螺旋槽的解析作图法,并通过Mat-lab开发了绘制螺旋槽的图形用户界面,利用Pro/E的扫描混合功能,构造了变螺距螺杆的三维实体模型,并通过AD-AMS进行了运动仿真分析,证明了设计的变螺距螺杆与供送件不会发生干涉,运行平稳,仿真结果与理论数据相吻合,验证了模型建立的正确性。为今后变螺距螺杆的设计提供了理论依据。     

基于RFID的汽车总装物料配送过程的Petri网建模与仿真

分析准时化生产环境下汽车制造企业总装现场物料配送过程.将射频识别技术融入准时化生产管理模式,研究了基于射频识别技术且与装配流程协同运作的总装现场物料配送过程.用赋时着色Petri网对该过程建立模型并进行仿真分析,所获得的结果可为描述与分析基于射频识别技术的汽车总装现场物流配送过程提供一定的参考和依据.