SOME ALGORITHMS FOR NC MACHINING SIMULATION AND VERIFICATION

This paper presents an approximation method to display realistic pictures of numerical control (NC) machining simulation very quickly. T he tool movement envelope is divided into many small regions and the normal to t hese small regions is calculated. The system saves the calculated result in a fi le before starting animation display. When the system starts displaying machinin g animation, it does not need to calculate small triangular facets normal to the workpiece surface. It only needs to find out what part of the cutter cuts the w orkpiece surface and to read the normal from the file. A highly efficient NC cod e verification method is also presented in this paper. The method first detects the error in z direction. If some points are reported to be out of the tolerance , the system divides neighborhood of these points into smaller grids and calcula tes the normal surface at each grid intersection and the error in the normal ve ctor direction.

Detailed analysis and simulation verification for reconstruction of plasma optical boundary with spectrometric technique on HL-2M tokamak

The plasma optical boundary reconstruction technique based on Hommen's theory is promising for future tokamaks with high parameters. In this work, we conduct detailed analysis and simulation verification to estimate the ‘logic loophole' of this technique. The finite-width effect and unpredictable errors reduce the technique's reliability, which leads to this loophole. Based on imaging theory, the photos of a virtual camera are simulated by integrating the assumed luminous intensity of plasma. Based on Hommen's theory, the plasma optical boundary is reconstructed from the photos. Comparing the reconstructed boundary with the one assumed, the logic loophole and its two effects are quantitatively estimated. The finite-width effect is related to the equivalent thickness of the luminous layer, which is generally about 2-4 cm but sometimes larger. The level of unpredictable errors is around 0.65 cm. The technique based on Hommen's theory is generally reliable, but finite-width effect and unpredictable errors have to be taken into consideration in some scenarios. The parameters of HL-2M are applied in this work.

Numerical simulation and experimental verification of the restraint intensity of pipeline girth welding joint

The restraint intensity （RI） of the pipeline girth welding joint was investigated using finite element method and experimental method to predict the cold cracking susceptibility of pipeline steel. The distribution of RI along the girth weld was investigated to study the influence of welding position on the RL Subsequently, the effects of outer diameter （OD） and wall thickness of pipeline on the RI were studied with ABAQUS software. The results show that the RI is almost independent of welding position. The RI increased with the increasing wall thickness but decreased with the increasing OD. A prediction model of Rl was developed based on the effects of the OD and the wall thickness. It has been found that the predicted RIs were in good agreement with the experimental values. The maximum fractional error between the predicted RI and the experimental values was just about 10%. h was indicated that the errors were mainly caused by the heterogeneous of the weld bead.

Determination method of mesh size for numerical simulation of blast load in near-ground detonation

In order to improve the overall resilience of the urban infrastructures, it is required to conduct blast resistant design for important building structures in the city. For complex terrain in the city, it is recommended to determine the blast load on the structures via numerical simulation. Since the mesh size of the numerical model highly depends on the explosion scenario, there is no generally applicable approach for the mesh size selection. An efficient method to determine the mesh size of the numerical model of near-ground detonation based on explosion scenarios is proposed in this study. The effect of mesh size on the propagation of blast wave under different explosive weights was studied, and the correlations between the mesh size effect and the charge weight or the scaled distance was described. Based on the principle of the finite element method and Hopkinson-Cranz scaling law, a mesh size measurement unit related to the explosive weight was proposed as the criterion for determining the mesh size in the numerical simulation. Finally, the applicability of the method proposed in this paper was verified by comparing the results from numerical simulation and the explosion tests and was verified in AUTODYN.

Verifying Stacks and Queues Using Symbolic Simulation Techniques

This paper presents a formal verification method based on logic simulation. In our method, using symbolic values even circuits which include data paths can be verified without abstraction of data paths. Our verifier extracts a transition relation from the state graph (given as a specification) which is expressed using symbolic values, and verifies based on simulation using those symbolic values if the circuit behaves correctly with respect to each transition of the specification. If the verifier terminates with "correct", then we can guarantee that for any applicable input vector sequences, the circuit and the specification behaves identically. We have implemented the proposed method on a Unix workstation and verified some FIFO and LIFO circuits by using it.

Co-Simulation模式软硬件协同仿真体系结构及实现

介绍和对比了HDL Co-Simulation、Vector、Transaction三种主要的软硬件协同仿真模式的执行流程及性能,并对其中的Co-Simulation模式软硬件协同仿真方法进行了体系结构的设计和功能部件的划分,描述了各部分组件的主要功能,并通过软、硬件试验平台对其进行了建模和编程实现,测试了其仿真性能。通过实验表明,该体系结构能够适用于任何Co-Simulation以及Vector模式的软硬件协同仿真实验,并可在保留基奉框架的情况下,通过部分功能的扩充,满足Transaction模式软硬件协同仿真的需求。

A Review on Aspects of Climate Simulation Assessment

This paper reviews some aspects of evaluation of climate simulation, including the ITCZ, the surface air temperature （SAT）, and the monsoon. A brief introduction of some recently proposed approaches in weather forecast verification is followed by a discussion on their possible application to evaluation of climate simulation. The authors suggest five strategies to extend the forecast verification methods to climate simulation evaluation regardless significant differences between the forecasts and climate simulations. It is argued that resolution, convection scheme, stratocumulus cloud cover, among other processes in the atmospheric general circulation model （AGCM） and the ocean-atmosphere feedback are the potential causes for the double ITCZ problem in coupled models and AGCM simulations, based on the system- and component-level evaluations as well as the downscaling strategies in some recent research. Evaluations of simulated SAT and monsoons suggest that both coupled models and AGCMs show good performance in representing the SAT evolution and its variability over the past century in terms of correlation and wavelet analysis but poor at reproducing rainfall, and in addition, the AGCM alone is not suitable for monsoon regions due to the lack of air-sea interactions.

Numerical simulation and land subsidence control for deep foundation pit dewatering of Longyang Road Station on Shanghai Metro Line 18

In terms of controlling groundwater in deep foundation pit projects, the usual methods include increasing the curtain depth, reducing the amount of pumped groundwater, and implementing integrated control, in order to reduce the drawdown and land subsidence outside pits. In dewatering design for confined water, factors including drawdown requirements, the thickness of aquifers, the depth of dewatering wells and the depth of cutoff curtains have to be considered comprehensively and numerical simulations are generally conducted for calculation and analysis. Longyang Road Station on Shanghai Metro Line 18 is taken as the case study subject in this paper, a groundwater seepage model is developed according to the on-site engineering geological conditions and hydrogeological conditions, the excavation depth of the foundation pit as well as the design depth of the enclosure, hydrogeological parameters are determined via the pumping test, and the foundation pit dewatering is simulated by means of the three-dimensional finite difference method, which produces numerical results that consistent with real monitoring data as to the groundwater table. Besides, the drawdown and the land subsidence both inside and outside the pit caused by foundation pit dewatering are calculated and analyzed for various curtain depths. This study reveals that the drawdown and the land subsidence change faster near the curtain with the increase in the curtain depth, and the gradient of drawdown and land subsidence changes dwindles beyond certain depths. In this project, the curtain depth of 47/49 m is adopted, and a drawdown-land subsidence verification test is completed given hanging curtains before the excavation. The result turns out that the real measurements basically match the calculation results from the numerical simulation, and by increasing the depth of curtains, the land subsidence resulting from dewatering is effectively controlled.

Simulation of the Hydraulic Behavior of a Bionic-Structure Drip Irrigation Emitter

The bionic structure drip irrigation emitter(BSDE)is a new-type emitter,by which better hydraulic performances can be obtained.In the present work,twenty-five sets of orthogonal test schemes were implemented to analyze the influence of the geometric parameters of the flow channel on the hydraulic characteristics and energy dissipation efficiency of this emitter.Through numerical simulations and verification tests,the flow index and energy dissipation coefficient were obtained.According to the results,the flow index of the BSDE is 0.4757-0.5067.The energy dissipation coefficient under the pressure head of 5-15 m is 584-1701.The verification test has shown that the relative errors among measured values,simulated values and estimated values are less than 3%,which indicates that the flow index can be estimated reliably.

Heat transfer analysis and experimental verification of cast heat exchanger

From the viewpoints of environmental conservation and energy efficiency,seawater-source heat pump system(SWHP) to provide district cooling and heating is applied in coastal areas.Based on the system,a heat transfer model was established for cast heat exchanger(CHE) adopted by SWHP systems.The CHE consists of pipes immersed in the seawater and used for transferring heat between the seawater and the heat exchanger pipes of SWHP system.An experimental study was carried out to test the validity of the model.A program was developed in VB language and the effects of inlet temperature,flow rate of the secondary refrigerant and length of CHE on the results were investigated.The results of the numerical simulation are in consistence with the experiments in both winter and summer conditions.As a result,application of SWHP systems with CHE in coastal areas in China is feasible due to the favorable geographical conditions and environment.

A Cooperative Activity on Quenching Process Simulation Japanese IMS-VHT Project on the Benchmark Analysis and Experiment

Japanese IMS-VHT project on the Virtual Heat Treatment tool for monitoring and optimising HT process in relation with the international cooperative programs is briefly introduced. This project motivates to develop virtual tools for computer to optimize the heat treatment condition and to support decision for HT operation by knowledge based database in addition to process simulation. As one of the activities with the cooperation of the Society of Materials Science, Japan and the Japan Society for Heat Treatment, a benchmark project is undergoing. This includes simulation of carburized quenching process of a cylinder, disc, and ring as well as a helical gear by use of common data of materials properties and cooling characteristics by several available simulation programs. A part of the newly obtained results is presented as an interim report.

Simulation Analysis and Optimization of Rolling Process of Steel Rim

In order to solve the problems of rolling forming accuracy and fillet thinning of alloy steel rim, a three-dimensional model of three pass rolling process was established, and the influence of different process parameters on forming quality was analyzed by using the finite element software, and the optimal process parameter combination was obtained. On this basis, the simulation results of wheel rim stress and strain for each pass rolling are analyzed, and the particle tracking technology is introduced to analyze the variation rule of stress in each incremental step. Finally, the simulation and experimental results show that the simulation thickness is basically consistent with the actual thickness, which improves the accuracy of rim rolling forming, and further verifies the correctness of rolling process simulation.

Reform and Practice in Education for Marine Hydrodynamic Course Based on Experiment Verification

In view of problems on the traditional education for marine hydrodynamic course, such as obsolete course content and methods of instruction, disjointed theory and experiment, and obscure effects, this paper explores and proposes a new reform and practice strategy for the marine hydrodynamic course using numerical simulation and experiment verification. The reform in education based on experiment verification focuses on the high-level theory, the experiment research and the professional skills. The results show that innovative potential and independent learning ability of students are aroused and cultivated, which satisfy the teaching requirements in the new era.

Valve Train Dynamic Design and Verification

Valve train dynamic behaviors need to be considered at the beginning of the engine mechanical design,especially during choosing valve spring parameters.From parameter definition to simulation,the valve train parameters around dynamic performance are determined step by step.The valve train dynamic test is done finally to verify the design result since it is a such important facet for valve train design.And reliability from mass production and product life view must be considered during whole design process too.

Matching and Simulation of Power Parameters of Electric Transporter based on Cruise Software

In view of the characteristics of warehouse or freight yard carrying out transfer and loading conditions,the performance parameter matching of the power system of an electric transfer vehicle was studied,and the driving motor and power battery of the key components of the vehicle were reasonably selected.Cruise software was used to simulate the loading process of the vehicle.The results show that the performance design of the power system of the electric transport vehicle and its key components is reasonable,meeting the requirements of maximum speed,climbing performance and starting driving performance,and providing a reference and credible basis for the design of the power system of the vehicle.

基于代码生成技术的Matlab/Simulink实验教学改革

针对Matlab/Simulink实验教学中存在仿真实验内容单一、缺少系统性和整体性、缺少项目化训练的问题,以PID控制和电机控制为教学案例,实现理论与实践相结合,将实践环节内容系统化、可视化,将学生所学的知识用于实际可操作、可控制的系统,使学生了解从软件仿真到硬件控制功能的实现过程,加强并拓宽学生对Matlab/Simulink应用范围的掌握,提高相关方面实验动手能力和编程能力。

叶顶间隙对离心蒸汽叶轮气动性能影响分析

旨在探究大流量高速离心蒸汽叶轮中叶顶间隙的影响及其机理问题。通过数值模拟和实验验证的方法,分析了六种不同叶顶间隙条件下对蒸汽叶轮性能的影响。研究结果显示,在制造工艺可行范围内,随着叶顶间隙的增大,等熵效率以及压比整体呈现下降的趋势。0.9 mm比0.6 mm等熵效率降低了0.88%,总压比降低了0.72%;1.2 mm比0.6 mm等熵效率降低了1.94%,总压比降低了1.51%。叶顶间隙的增大也导致蒸汽在叶轮前盖侧提前发生分离,侧漏流影响区域扩大,叶轮出口前盖侧尾迹区增大。

危化品罐车制动冲击对罐体的影响

为了保障罐车的运输安全,针对罐车在制动过程中罐内液体的冲击特性进行了研究。采用标准的κ-ε模型对罐车罐体内液体的晃动冲击过程进行了数值模拟。分析显示,填充率、填充介质、外界激励对罐内液体晃动的影响最为显著。对上述3种主要影响因素分别进行了数值模拟,结果表明:随着填充率的增加,液体晃动产生的冲击力随之减小;随着填充介质的密度的增大,晃动冲击力也随之增大,而填充介质的粘度对晃动冲击力的影响可以忽略不计;随着外界激励的增大,液体晃动激烈,晃动冲击达到峰值的时间随之提前,晃动冲击力也随之增大。最后通过缩比实验验证了仿真模型的有效性。该研究对于保证危化品罐车的安全运行具有重要的参考价值。

新型侧挂式磁悬浮系统的稳定性分析

为了突破磁悬浮地球仪的传统结构,提出了一种新型的侧挂式磁悬浮系统。介绍了系统的基本结构并进行结构选型。从系统磁力分布的角度,对系统的稳定悬浮原理进行分析。建立了系统的数学模型,为了验证系统的静动态性能,对其进行阶跃位移与阶跃干扰下的控制仿真。搭建侧挂式磁悬浮系统的实验样机,对其进行稳定悬浮性能实验与位移跟踪性能实验。实验结果表明,系统存在轻微的振荡现象,但能够长时间稳定悬浮。当系统受到垂直向下0.5 N的干扰力时,在0.54 s的短暂调节后,系统仍能够保持稳定悬浮的状态,稳态位移误差不超过0.2736 mm;在垂直方向上施加0.5 mm的阶跃位移,系统能够稳定地跟随参考位移信号,响应时间为0.73 s,跟踪位移误差不超过0.4321 mm。

基于显式预测的高速多体船纵向减摇控制

多体船高速航行过程中会产生较大幅度的升沉和纵摇运动,而减摇附体具有较为严格的攻角输入幅值约束,文中提出一种卡尔曼滤波估计和显式预测结合的多体船纵向减摇方法。首先,建立包含T型翼和压浪板的多体船纵向运动控制模型,对外界海浪干扰进行白化处理,并采用卡尔曼滤波方法获得系统状态估计值。其次,将线性化后的估计误差引入预测模型,从而提高模型精度。最后,采用显式预测控制方法将在线滚动优化转化为离线计算,有效提高控制系统实时性。通过数值仿真验证了算法的有效性,结果表明升沉和纵摇量分别减少42.4%和52.1%。