计算机数值模拟技术在大型锻件淬火过程中的应用

大型锻件淬火过程中，温度场和组织场分布及其变化极不均匀，因此产生较大的瞬时应力和残余应力，进而使工件产生较大的变形甚至开裂，造成巨大的经济损失。开展大锻件淬火过程中温度场、组织场及应力场的研究，弄清它们与淬火工艺的关系，从而合理地制定淬火工艺，对提高大锻件热处理后的性能及减少废品有很大帮助。淬火过程计算机数值模拟技术利用数值分析技术、可视化技术，基于传热学、力学及金属相变等理论进行淬火温度场、组织场和应力场的模拟仿真。     

PAG淬火介质在合金结构钢前轴余热淬火中的应用

淬火介质对保证淬火工艺实施有重要作用。采用水或油作为淬火介质,均存在一定缺陷,不能满足合金结构钢前轴锻件热处理的需要。通过分析理想淬火介质的冷却曲线,发现一种新型PAG淬火介质的冷却特性可以满足要求。介绍了这种新型淬火介质的冷却原理、使用条件及技术要点。并结合实践,介绍了该介质在合金结构钢前轴锻件(42CrMo材质中重型前轴,120~140kg)热处理生产过程中的使用情况。     

带有缺陷的大型轴类锻件热处理过程中的计算机辅助安全评估

用计算机计算大型轴类锻钢件在热处理过程中的温度场、应力场,并根据超声波探伤检测出的大型锻件的冶金缺陷,运用断裂力学的方法对锻件在热处理过程中的开裂行为进行预测,针对材料在不同热处理状态下相态及性能的不同,测定了两种钢(70Cr3Mo 和26Cr2Ni4MoV)淬火过程和回火过程中的断裂韧度。本方法曾试用于大型锻钢支承辊喷雾淬火热处理并得到了验证。     

42CrMoA风电主轴热处理工艺

正风电主轴为大型锻件,热处理工艺为调质,工件淬火出炉后采用不同的淬火冷却介质及淬火冷却时间来满足生产使用要求。淬火是热处理工艺中的重要工序,为保证大型锻件足够深的淬硬层来满足轴向性能及切向性能,整个工件截面必须有合理的温度梯度分布,也可减小淬火过程中的应力。42CrMoA风电主轴的热处理工艺有很多可参考,但是并不是照搬就可以满足所有产品的性能要求,为此我们再一次对其进行了分析和研究,通过不断调整参     

大型曲臂锻件模锻成形工艺模拟研究

针对大型曲臂锻件的结构特点和性能要求,提出采用了预锻-终锻两步成形方法模锻成形大型曲臂锻件。采用DEFORM-3D有限元软件对此工艺方法的成形过程进行模拟,并对应力、应变、温度场的分布特点和时间-载荷曲线进行分析。结果表明,采用此方法能够在8万吨水压机上饱满成形大型曲臂锻件,得到金属流动合理、锻造流线完整的锻件。     

淬火中喷雾冷却效果的数值模拟分析

通过对大型锻件淬火冷却中常用淬火介质的对比分析,探讨不同淬火介质的优缺点。针对中国一重生产的大型锻件,利用MATLAB编制的程序模拟锻件在淬火过程中经过喷雾冷却后的温度场变化,将喷雾冷却的计算结果与油冷和水冷的试验数据对比,以验证数值模型的有效性及模拟结果的准确性,分析喷雾时间和水流密度对喷雾冷却过程的影响。     

基于分段冷压法7050大型铝合金锻件残余应力的消减

采用分段冷压法对7050大型铝合金锻件的淬火残余应力进行消减,通过Deform-3D有限元软件模拟了分段冷压前后锻件残余应力的大小和分布,并采用盲孔法对分段冷压前后锻件的残余应力进行测试。结果表明:分段冷压使铝合金锻件的残余应力得到大幅度消减,实测得到的残余应力均小于130 MPa,消减幅度达到70.3%~97.4%,且非搭接区域残余应力的消减效果比搭接区域的好,模拟结果与测试结果相吻合。     

筒形锻件在立式车床加工中的定心方法

介绍筒形锻件的余量检测方法,并结合大量的生产实践经验,以矢量分析做为理论依据,采用AutoCAD辅助软件,对筒形锻件在立式车床加工时的定心规律进行分析,总结出一套准确实用的定心方法。该方法能够广泛地应用到各种筒形锻件的加工准备工序中,能够有效保证筒形锻件在加工内、外圆周前加工余量的分布处于最佳状态,为后序生产加工提供有力保障。     

车桥桥壳锻造成形过程的数值模拟分析

针对车桥桥壳精锻成形难度大的问题,利用DEFORM-3D软件对桥壳的锻造成形过程进行模拟仿真分析。讨论了锻件坯料尺寸形状对其成形性的影响,分析了成形过程中等效应力、应变分布以及载荷行程曲线,研究了锻件形状对金属材料流动规律的影响,利用研究结果优化模具结构及工艺参数,并在实际生产中验证了工艺方案的正确性。     

基于Visual C ++交互仿真软件的重轨淬火应力场数值模拟分析

针对重轨淬火工艺难以制定的问题,对重轨淬火的应力场及其有限元模型的建立进行了分析,并基于Visual C++开发了针对重轨淬火应力场分析的仿真软件。在实际应用中,只需要在该仿真软件上输入相应的参数,包括重轨淬火的材料热物性、工况条件等,该仿真软件就会在后台自动调用有限元软件对重轨淬火过程进行有限元数值模拟,获得其应力场分布,通过对比分析得到最佳加热时间,并制定出较优的重轨淬火工艺。仿真后,通过对比3种工况的分析结果表明:加温时间设置为40 s,保温时间设置为25 s,淬冷时间设置为35 s是较优的重轨淬火工艺路线,为不了解有限元软件甚至没有使用过有限元软件的重轨淬火工作人员对重轨淬火工艺进行分析时提供了方便,对实际生产具有重要意义。     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

基于多目标非支配解提取法的电力系统无功优化

针对传统的电力系统多目标粒子群优化算法采用权重系数法将多目标转化为单目标,从而忽视了各目标函数间的竞争关系这一问题,提出将非支配解提取法运用到电力系统多目标无功优化中,并设定了一套提取规则,以电力系统中的有功网损、电压偏差和电压稳定裕度为目标,使目标在充分竞争的情况下得出Pareto最优解,利用IEEE-14节点系统对多目标非支配解提取法的电力系统无功优化进行了仿真测试。研究结果表明,该算法一次运行可以得出多组非支配解,既有偏向单个目标的解也有兼顾所有目标的解,克服了权重系数法的盲目性和单一性,可使电力决策者根据实际问题选择最优解,具有较好的灵活性与多样性。     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

Hybrid inversion method for equivalent electric charge of thunder cloud based on multi-station atmospheric electric field

This article proposes the hybrid method to inverse the equivalent electric charge of thunder cloud based on the data of multi-station atmospheric electric field. Firstly,the method combines the genetic algorithm( GA) and New ton method through the mosaic hybrid structure. In addition,the thunder cloud equivalent charge is inversed based on the forw ard modeling results by giving the parameters of the thunder cloud charge structure. Then an ideal model is built to examine the performance compared to the nonlinear least squares method. Finally,a typical thunderstorms process in Nanjing is analyzed by Genetic-New ton algorithm with the help of weather radar. The results show the proposed method has the strong global searching capability so that the problem of initial value selection can be solved effectively,as well as gets the better inversion results. Furthermore,the mosaic hybrid structure can absorb the advantages of tw o algorithms better,and the inversion position is consistent with the strongest radar echo.The inversion results find the upper negative charge is small and can be ignored,w hich means the triple-polarity charge structure is relatively scientific,w hich could give some references to the research like lightning forecasting,location tracking.     

虚拟式流体参量集成测试系统及其实现

为了实现对流体参量的自动测量,运用虚拟仪器设计思想,采用组件技术、海量数据存储技术及仪器通用化设计方法,设计并实现了虚拟式流体参量集成测试系统.该系统能同时对流体的温度、压力和流量等进行动态测试.实验室演示表明,该集成测试系统性能稳定,操作简单,功能较强大.     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

COMPUTER SIMULATION OF CONTINUOUS ELECTROMAGNETIC STIRRING FOR MAKING RHEOLOGIC SEMI-SOLID SLURRY OF ZL112Y ALUMINUM ALLOY

To realize the technology of fabricating the rheologic semi-solid slurry of ZL112Y aluminum alloy via continues electromagnetic stirring process, ANSYS software was used to simulate electromagnetic force field and fluid velocity field in the alloy melt in a crucible tube in three coils. In the first section of the paper, eletromagnetic force field and fluid velocity field caused by single coil were simulated. The result of this simulation gives an average velocity of 3.2 cm/s and it is called critical velocity because a fluid velocity over it will cause a fine and spherical structure of solid primary a in a semi-solid melt. And, from this result, a reasonable temperature of semi-solid of the alloy and an electrical current intensity were established. The electrical current intensity of the result of this simulation corresponded to the current intensity used in a practice experiment, in which the primary α was obviously refined and sphericized. Based on this simulation of single coil electromagnetic stirring, in the second section of the paper, eletromagnetic force field and fluid velocity field caused by three coils were simulated. The result of the simulation shows that, 1） there is a semi-solid zone of 32 mm from bottom of the crucible tube to the upper; 2） the electrical current intensities of three coils of 400 A, 600 A, and 400 A, which were set to top range, middle range and bottom range of the tube, respectively, were the optimum parameters of electromagnetic current intensity under the condition of this investigation; and 3） under effect of these electromagnetic current intensity, the fluid velocities of the melt in the tube were 6.3 cm/s in top range, 3.75 cm/s in middle range, and 3.9 cm/s in bottom range of it, respectively.