基于混合磨损模型的模具轮廓优化设计

针对成形过程模具的磨损剧烈,模具寿命低的问题,采用混合磨损模型对模具轮廓进行优化设计。以轮毂锻造成形过程中上模芯磨损为例,对上模芯轮廓进行分析,确定待优化的3个设计参数。根据黏着磨损、磨粒磨损及氧化磨损这3个磨损模型建立新磨损计算模型,并通过有限元软件数值模拟获取模具轮廓各处的磨损,以等磨损量作为模具轮廓磨损均匀的评判标准。在此基础上,以有限元软件数值模拟数据作为训练样本,采用BP神经网络建立上模芯轮廓设计参数与模具等磨损量的非线性映射关系。最后,结合训练好的函数映射关系和遗传优化算法,对轮毂锻模的上模芯进行形状优化设计,反求出磨损最均匀状态下的上模芯设计参数。研究结果表明:优化后上模芯等磨损量比优化前减少了29.65%,且最大磨损下降了12.59%,上模芯磨损更均匀且最大磨损量更小。     

基于遗传算法的挤压模具型腔形状优化设计

以磨损为目标建立优化数学模型,采用B样条函数插值描述模具型腔轮廓形状,基于有限元和修正的Archard磨损模型计算结果训练BP神经网络,建立模具型腔控制点与目标函数之间的映射关系,计算遗传算法的适应度值,优化模具型腔．研究结果显示：采用本方法得到的模具型腔形状,与锥形模相比,沿其表面最大磨损深度降低了63．9％,磨损深度分布均匀,说明此设计方法可行．     

DP780高强钢板的弯曲凹模圆角曲形优化

针对冲压成形过程中模具磨损及零件表面黏模等问题,以DP780高强度钢板U型弯曲成形为例,采用有限元数值模拟及工艺试验相结合的方法,对弯曲成形模具凹模圆角区域进行磨损区域预测及凹模圆角优化设计。研究结果表明:基于FEM-Archard磨损模型预测的弯曲成形黏模区域与试验结果相吻合;凹模圆角和形状对模具圆角表面磨损深度影响很大,凹模圆角半径越大,磨损深度越小;偏差-椭圆弧比标准圆弧、椭圆弧具有更好的抗成形黏模性能。     

叉头一模两件预成形过程的数值模拟分析

锻造成形过程是一个非常复杂的弹塑性大变形过程,有限元法是用于锻造成形过程模拟中一种有效的数值计算方法.通过数值模拟技术分析叉头锻件改成一模两件的预成形过程,优化预成形模具型腔,获得合理的生产工艺,达到提高原材料利用率和生产班产量,并获得合格终锻件的目的.     

直齿圆柱齿轮精锻模具设计及有限元分析

针对某直齿圆柱齿轮,进行了带浮动式凹模的精密锻造模具的设计.并结合此浮动式模具结构,利用刚塑性理论方法建立了该直齿圆柱齿轮精锻的合理有限元模型,采用DEFORM-3D软件对整个成形过程进行有限元数值模拟.得到了变形区的速度场分布、坯料的damage分布等,分析了其分布规律.由此验证了带浮动式凹模的精锻模具结构的合理性,为有效地进行工艺研究、优化工艺参数提供了方法和依据.     

铝型材挤压模具导流孔结构优化

基于MATLAB平台,将BP人工神经网络、遗传算法和数值模拟技术应用于铝型材挤压模具的导流孔形状优化设计。由正交实验法安排模拟实验组合,采用SuperForge软件对进行型材挤压过程进行数值模拟,并以挤压时金属流出模口平面的z向质点流速的均方差作为模型目标值;将模拟结果作为人工神经网络的输入样本对进行网络训练并建立网络知识源;通过遗传算法求得模型的全局优化解;最后通过有限体积法数值模拟技术验证并比较优化所得导流孔形状与经验法确定的导流孔形状对金属流动均匀性的影响。分析结果表明,通过调整导流孔形状能使金属流出模口的速度分布更均匀,表明对挤压模具导流孔形状的优化是有效的。     

基于滚动调度的冲压模具磨损数值模拟分析

为了提高冲压模具磨损数值的量化分析精度,提出基于滚动调度的冲压模具磨损数值模拟方法。采用动态轮廓采样法进行冲压模具磨损数值采集,结合多传感器融合采样方法进行冲压模具磨损数值采样后的滚动调度,建立冲压模具磨损数值信息融合和特征提取模型,提取冲压模具磨损数据的谱特征量,采用谱分析的方法进行冲压模具磨损数值拟合和自适应调度,建立冲压模具磨损数值模拟的滚动调度模型,从运动学角度建立了冲压模具磨损的滚动调度运动分析模型,采用工件表面形貌自适应预测方法,实现冲压模具磨损数值模拟。仿真结果表明,采用该方法进行冲压模具磨损数值模拟的精度较高,拟合性较好,提高了冲压模具磨损数值模拟和参数估计能力。     

载重汽车用直齿轮冷挤压组合凹模的优化设计

为提高载重汽车用直齿轮冷挤压组合凹模的使用寿命,以组合凹模的齿形腔等效内径、直径比和过盈系数为设计变量,以降低模芯内壁等效应力为优化目标,建立组合凹模结构参数与等效应力的Kriging模型。应用Kriging模型结合粒子群算法,在可行变量空间内寻优,得到组合凹模最佳结构尺寸为:模芯外径D_2=107.485 mm,中圈外径D_3=187.215 mm,外圈外径D_4=274.839 mm,模芯与中圈的单边径向过盈量U_1=0.134 mm,中圈与外圈的单边径向过盈量U_2=0.253 mm,采用优化后的组合凹模进行数值模拟。研究结果表明:在模芯消气带齿槽处等效应力最大,其值为1 870 MPa。优化方法为齿类零件冷挤压成形组合凹模设计提供了定量的确定方法。     

BP神经网络和遗传算法用于曲轴填充性能的优化设计

针对曲轴空间分模模具存在的深型腔难填充结构,提出了采用楔形飞边槽结构改善填充性能的方法。基于MATLAB平台,将BP 人工神经网络与遗传算法应用于楔形飞边槽结构参数优化设计。首先利用正交试验设计安排试验样本,对所得的样本进行有限元模拟,获得各方案坯料的最小未填充距离,作为BP神经网络训练的导师信号。再结合遗传算法,以最小未填充距离为目标,得到楔形飞边槽结构的最优参数。最后通过数值模拟验证并比较遗传算法预测结果与数值模拟结果的误差。结果表明,误差在5%以内。将优化参数应用于实际生产,坯料能够完全充满模具型腔     

端盖热挤压成形方案优化设计及多目标模具磨损失效的分析

为了优化端盖零件的成形质量,为端盖零件的实际生产加工提供理论依据,本文设计采用模拟端盖零件的2种成形方案及过程,对最优方案利用追踪点的方法获取符合加工挤压件要求的直径,并基于正交试验与数值模拟技术研究多目标参数对凸模模具磨损的影响以及凸模磨损的具体位置,最后利用反求法探寻加工后凸模是否发生损坏或者继续加工是否会造成凸模损坏。模拟结果表明:利用方案一成形方法加工端盖零件效果最好,Φ27. 54、Φ27. 62两种直径下端盖的成形效果最为理想,符合加工要求;端盖在热挤压成形过程中以凸模磨损深度为判断依据的最优水平为C1D4组合,即挤压速度为100 mm/s,凸模初始硬度为60 HRC;挤压速度为100 mm/s时凸模的抗磨损能力比300 mm/s时提高1. 3倍以上;凸模初始硬度为60 HRC时其抗磨损能力比52 HRC时提高1. 3倍以上,在很大程度上增加了模具使用寿命; P3、P6点位置的凸模磨损最严重,但模具的表面压强、表面温度等均符合加工要求,故凸模磨损符合生产要求。上述结果表明:本文端盖热挤压成形的优化设计符合生产加工要求。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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