A novel chatter stability criterion for the modelling and simulation of the dynamic milling process in the time domain

The modelling of the dynamic processes in milling and the determination of chatter-free cutting conditions are becoming increasingly important in order to facilitate the effective planning of machining operations. In this study, a new chatter stability criterion is proposed, which can be used for a time domain milling process simulation and a model-based milling process control. A predictive time domain model is presented for the simulation and analysis of the dynamic cutting process and chatter in milling. The instantaneous undeformed chip thickness is modelled to include the dynamic modulations caused by the tool vibrations so that the dynamic regeneration effect is taken into account. The cutting force is determined by using a predictive machining theory. A numerical method is employed to solve the differential equations governing the dynamics of the milling system. The work proposes that the ratio of the predicted maximum dynamic cutting force to the predicted maximum static cutting force can be used as a criterion for the chatter stability. Comparisons between the simulation and experimental results are given to verify the new model.     

Design and fabrication of a novel polishing tool for finishing freeform surfaces in magnetic field assisted finishing (MFAF) process

Surface finish is a critical requirement for different applications in industries and research areas. Freeform surfaces are widely used in medical, aerospace, and automobile sectors. Magnetic field assisted finishing process can be used very efficiently to finish freeform surfaces. In this process, magnetorheological fluid is used as the polishing medium and permanent magnet is used to control its rheological properties to generate finishing force during polishing. To avail sufficient magnetic field in the finishing zone, it is necessary to design an optimum polishing tool. In the present study, a specially designed polishing tool is designed using a finite element based software package (Ansys Maxwell^®) based on Maxwell equations. At first, dimension of the permanent magnet is determined for designing optimum tool geometry. After that, dimension and configuration of the magnet fixture are optimized. A special type of metal named mu-metal which is a nickel-iron based alloy is selected for magnet fixture due to its magnetic-field shielding property. Mu-metal directs the magnetic flux lines in such a way that in the finishing zone the magnetic flux can be concentrated on the workpiece surface required for finishing. Also, the Mu-metal magnet fixture shields the magnetic field from outside environment so that MR fluid as well as any surrounding magnetic materials do not stick to the polishing tool. Experiments are carried out to validate the Maxwell simulation results to compare the magnetic flux distribution on the workpiece surface which shows good agreement between them. Also, finishing of flat titanium workpieces are carried out and it is found that the novel polishing tool has the capability to finish the workpieces in the nanometer range.     

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.     

Effective process design and robust manufacturing for hydroformed parts

A general trend and one of the important strategies in the automotive industry is reducing the lead time of a new car development. In order to obtain this goal the efficient use of simulation software is needed to effectively design a hydroformed part. The stages of the design chain are integrated in one simulation tool. The outcome of this feasibility analysis is a virtual prototype saying that it is possible to produce the part. In fact one process point has been defined whereas when going into production a process window must be know to guarantee a stable production process. In order to achieve this latter we are suggesting a process performance analysis. Based on multiple simulations the influence and sensitivity various process parameters on the forming process can be identified. Besides combining the analysis with statistical process control evaluation the process capability (Cpk-values) can be defined. This design chain analysis will be applied on a hydroformed part. The process performance analysis is the identification of the process window and process capability in advance, so before any tool has been milled. This will be demonstrated on a second hydroformed part.     

A simulation of the comminution process of homogenized lithium-ion battery models

The simulation of the comminution process of a lithium-ion battery model and evaluation of the performance of three cylindrical battery models derived from previous studies were achieved in the present study. The finite element method (FEM) was used along with dynamic simulation procedures. The models were classified based on the battery material model parameters used in the analysis, namely type A, B, and C models. The battery material models of type A and C were unable to provide results that were consistent with real-world circumstances. In contrast, the type B model gives a realistic battery dynamic reaction. Additional testing on the type B model was performed in terms of battery shard size, fracture energy, comminution pressures, element displacement, battery element velocity, and device capacity calculation. The simulation results revealed that the type B model in this study is capable of properly predicting the dynamic response of the battery, notably when compared to the other two models. The study in the present research could be used in the future to identify the proper cutting tool geometry, estimate the size of the comminution product, and play an important role in the design and optimization of the comminution machine.

     

Optimum blank design by the predictor-corrector scheme of SLM and FSQP in the deep drawing process of square cup with flange

This paper presents a more accurate predictor-corrector scheme that combines the stream line method (SLM) and feasible sequential quadratic programming (FSQP) using the explicit dynamic finite element method (FEM) to design the optimum blank in the deep drawing process of square cup with flange. It is clear that faster convergence and better results of calculating optimum blank shape are guaranteed when FSQP uses a better initial guess. But it is not easy to guess the initial blank shape due to the variation of blank thickness, material anisotropy, and friction on the flange area at the beginning in the deep drawing process. SLM can obtain a preliminary prediction of the optimum blank shape with a little computational effort, so with SLM it is feasible to predict the initial guess of optimum blank with the assumption of fixed height of square cup with flange. FSQP can continue to adopt the predictor obtained by SLM to correct the optimum blank efficiently and accurately. Then the optimum blank is used in the final simulation and experiment. From comparison of the target shape between the simulated and experimental results, a good correspondence is confirmed. Other comparisons of the punch load, punch stroke, and wall thickness of the target square cup also show good agreement.     

基于MATLAB的电液力伺服系统设计与优化

采用经典控制理论设计电液力伺服系统,并将二次型最优控制理论引入其中。通过计算机仿真分析,比较优化前后系统的动态性能,从而找出其中较为合理的设计方法。通过分析得出,采用最优二次型理论设计电液力伺服系统可减少设计程序,避免经典控制理论中系统设计的试凑和图解法的麻烦,为系统设计提供了方便。利用MATLAB／SIMULINK软件工具箱中提供的系统分析和设计的交互式工具,可以大大简化分析和设计的过程。     

基于模糊技术的自动离合器起步控制研究

针对自动离合器起步控制进行研究,建立了离合器的接合动力学模型和离合器动态摩擦力矩模型,分析了离合器的接合过程。应用模糊控制技术对自动离合器在车辆起步时的接合过程进行控制,并通过建立SIMULINK模型对控制系统进行仿真。结果表明,该控制系统避免了起步冲击和不能很好适应驾驶员起步意图的问题。     

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。     

Optimization techniques applied to single point incremental forming process for biomedical application

Single point incremental forming (SPIF) process has the potential to replace conventional sheet forming process in industrial applications. For this, its major defects, especially poor geometrical accuracy, should be overcome. This process is influenced by many factors such as step size, tool diameter, and friction coefficient. The optimum selection of these process parameters plays a significant role to ensure the quality of the product. This paper presents the optimization aspects of SPIF parameters for titanium denture plate. The optimization strategy is determined by numerical simulation based on Box–Behnken design of experiments and response surface methodology. The Multi-Objective Genetic Algorithm and the Global Optimum Determination by Linking and Interchanging Kindred Evaluators algorithm have been proposed for application to find the optimum solutions. Minimizing the sheet thickness, the final achieved depth and the maximum forming force were considered as objectives. For results evaluation, the denture plate was manufactured using SPIF with the optimum process parameters. The comparison of the final geometry with the target geometry was conducted using an optical measurement system. It is shown that the applied method provides a robust way for the selection of optimum parameters in SPIF.     

泵车泵送系统LabVIEW建模方法研究

LabVIEW软件是一种图形化的编程工具,人机交互界面方便且带有仿真与控制设计模块,可以进行系统的数学建模与仿真.为此,在深入研究某款THB38型号混凝土泵车液压系统工作原理的基础上,采用功率健合图与LabVIEW软件相结合方法建立了其泵送系统的数学建模,并进行了正常泵送和发生混凝土堵管故障两种工况下的仿真分析.仿真结果表明:该建模方式能满足仿真精度要求,可以用来方便地研究泵送系统故障发生前、后系统动态特性的变化,以便达到全面掌握混凝土泵车液压系统动态特性的目的.希望该建模方式对其他系统的建模能提供一些参考和指导.     

Integration of advanced process control and full-scale dynamic simulation

In the process control industry, multivariable model predictive controller and dynamic simulation for operator training are usually available in separate packages. It is very difficult for the operators and plant engineers to find good tools for them to get trained in multivariable advanced process control. This paper presents a system, which integrates the advanced process control and full-scale dynamic simulation. The advanced process control uses multivariable model predictive control techniques. The model used in the predictive control algorithms is generated from the dynamic simulated process. The advanced process controller can control the simulated plant directly, or through a DCS system to control the simulated plant. The combined system provides an excellent environment for training operators in process operation with multivariable advanced process control. The same environment is also very useful for engineers in designing and tuning the advanced process controllers, and in testing communication between the advanced process controller and the DCS systems, or the other type of process control systems.     

System identification and admittance model-based nanodynamic control of ultra-precision cutting process

The control of diamond turning is usually achieved through a laser-interferometer feedback of slide position. The limitation of this control scheme is that the feedback signal does not account for additional dynamics of the tool post and the material removal process. If the tool post is rigid and the material removal process is relatively statie, then such a non-collocated position feedback control scheme may suffice. However, as the accuracy requirement gets tighter and desired surface contours become more complex, the need for direct tool-tip sensing becomes inevitable. The physical constraints of the machining process prohibit any reasonable implementation of a tool-tip motion measurement. It is proposed that the measured force normal to the face of the workpiece can be filtered through an appropriate admittance transfer function, providing an estimated depth of cut. This can be compared to the desired depth of cut to generate the adjustment control action in addition to position feedback control. In this work, the design methodology on admittance model-based control with a conventional controller is presented. The recursive least-squares algorithm with forgetting factor is proposed to identify the parameters and update the cutting process in real time. The normal cutting forces are measured to identify the cutting dynamics in the real diamond turning process using a precision dynamometer. Based on the parameter estimation of cutting dynamies and the admittance model-based nanodynamic control scheme, simulation results are shown.     

基于价值流图的车载面板车间优化

价值流图是一种实施精益生产的工具,但是因价值流图不能详细描述生产系统的动态行为,导致其在精益生产应用方面存在局限性,通过结合仿真技术能够克服价值流图的静态局限性.针对D公司车载面板车间,首先运用价值流图识别车间存在的问题,并制定改善设计方案;接着,建立改善后的车间仿真模型,并以基本存储定量在制品控制策略(Base St...     

Optimization of contact forces in tailor-welded blanks forming process

To attain the objective of minimizing the harmful movement of the weld joint in tailor-welded blanks (TWBs) forming, a novel optimization methodology based on dynamic explicit finite element simulation is presented to determine optimum contact forces. In this methodology, forming limit diagram (FLD) models developed for different types of TWBs are treated as a criterion of constraint in optimizations. Due to the highly nonlinear nature of the forming process, response surface methodology (RSM) is utilized to construct sequential response surfaces to approximately describe the objective the constraint functions and the optimum contact forces of TWBs stamping are obtained with some successive iterations. However, a large number of numerical simulation runs are needed for optimization with higher-order approximate models or many design variables. To improve the efficiency of optimization, the space mapping (SM) technique utilizing surrogate models is integrated with RSM. Two examples are used to validate this algorithm: one optimization for TWBs stamping with the same thickness but different materials, and the other optimization for TWBs stamping with the same material but different thicknesses. The results demonstrate that the method is efficient and effective in solving contact forces optimization problems.     

Integrated simulation method for interaction between manufacturing process and machine tool

The interaction between the machining process and the machine tool (IMPMT) plays an important role on high precision components manufacturing. However, most researches are focused on the machining process or the machine tool separately, and the interaction between them has been always overlooked. In this paper, a novel simplified method is proposed to realize the simulation of IMPMT by combining use the finite element method and state space method. In this method, the transfer function of the machine tool is built as a small state space. The small state space is obtained from the complicated finite element model of the whole machine tool. Furthermore, the control system of the machine tool is integrated with the transfer function of the machine tool to generate the cutting trajectory. Then, the tool tip response under the cutting force is used to predict the machined surface. Finally, a case study is carried out for a fly-cutting machining process, the dynamic response analysis of an ultra-precision fly-cutting machine tool and the machined surface verifies the effectiveness of this method. This research proposes a simplified method to study the IMPMT, the relationships between the machining process and the machine tool are established and the surface generation is obtained.     

Optimum process conditions on shrinkage of an injected-molded part of DVD-ROM cover using Taguchi robust method

Plastic injection molding is an important process to produce thin-shell parts. However, the difficulty in adjusting optimum process conditions may cause defects of the injected-molded parts such as shrinkage. This study investigates on the optimum combinations of process conditions on shrinkage of an injected-molded part of the DVD-ROM cover based on Taguchi method. In doing this, a series of Moldflow analyses have been performed as per L₂₇ orthogonal array design with each analysis by means of the process conditions of mold temperature, melt temperature, injection pressure, injection time, and cooling time. In the meantime, signal-to-noise (S/N) ratio is utilized to determine the optimum combinations of the process conditions for shrinkage through analysis of variance (ANOVA). ANOVA is further used to find which of the process conditions are statistically significant. Finally, confirmation tests at the optimum combinations of the process conditions were executed to verify the robustness and the effectiveness of Taguchi method within 95% confidence interval. From the findings, it can be stated that Taguchi method is a powerful tool for evaluating the defect of shrinkage in the plastic injection molding.     

FEA-aided design of multi-stage drawing process and tooling for production of a miniature sheet metal component

This paper presents the design of multi-stage drawing process and tooling aided by finite element analysis (FEA) for fabrication of a miniature sheet metal component, made of a cold-reduced carbon steel material (SPCC). To design such a tooling, it is essential to figure out how many intermediate drawing steps are needed to produce the final part without deformation defect. First of all, a four-stage drawing process and a set of four-station tooling are designed. This pre-designed process is then analyzed by simulation, and the deformation behavior and formability in each stage is revealed. Based on the revealed deformation behavior and formability, the design of the process and tooling is confirmed. The reasonable drawing ratio and drawing depth in each drawing operation are determined. The size, clearance, and the corner radii of punch and die in each stage are also identified. The designed process and tooling are finally implemented. Through experiment, the “right design in the first time” is realized, and the simulation and experiment are found to have a good agreement. The research further demonstrates that the FEA simulation can be used as an effective tool to aid the design of metal-formed component, tooling, and process in upfront design process.     

AMESim在带式输送机停机过程设计中的应用

利用AMESim软件建立带式输送机仿真模型,通过仿真分析带式输送机停机时头部和尾部重要参数在不同工况的变化情况,并利用AMESim仿真软件图形化的开发环境来优化设计参数,有利于提高设计效率。仿真过程和理论结果基本一致,取得良好的效果,说明利用AMESim仿真能为输送机制动过程的分析和控制以及输送机系统的优化设计提供一种新的分析手段和设计方法。