基于渐变凹模圆角半径的高强钢扭曲回弹补偿

为减少高强钢冲压成形扭曲回弹,提出一种基于渐变凹模圆角半径的模具补偿方法。以高强钢TRIP780双C件为研究对象,采用板料冲压成形仿真软件DYNAFORM对该双C件的冲压、扭曲回弹过程进行数值模拟。提出一种评价双C件扭曲回弹程度的指标,并进行双C件扭曲回弹试验,通过三坐标测量仪测量扭曲回弹角,对有限元模型进行了验证。以冲压成形后的扭曲回弹为优化目标,结合相关的工艺参数,利用BP神经网络,基于正交试验,建立凹模圆角半径渐变量、工艺参数与扭曲回弹角之间的网络模型。最后采用遗传算法对该模型迭代寻优获得最优凹模圆角半径渐变量和工艺参数。通过对比优化前后的扭曲回弹角,证明了优化流程有效地减少了双C件扭曲回弹。该方法为扭曲回弹的控制提供了一种新的思路。     

基于神经网络的板料冲压回弹预测系统的研究

文中以NUMISHEET’93标准考题中U形板料作为研究对象,将正交试验法和数值模拟法结合,产生各工艺参数组合下的冲压回弹量,以这些仿真试验结果作为神经网络的训练样本,在NeuroSolution软件环境下建立输入为工艺参数、输出为冲压回弹量的神经网络模型预测模型,以测试样本验证模型的预测精度作为反馈信息,构成闭环系统。该方法为板料冲压工艺参数的优化提供了有效的工具。     

基于多目标遗传算法优化板料拉深成形工艺参数

利用人工神经网络构建了板料拉深成形的目标函数模型,建立了板料拉深成形工艺参数和性能评价指标之间的映射关系.以多种工艺参数(压边力、摩擦因数等)作为优化变量,多种成形缺陷(起皱、破裂等)作为优化目标,结合多目标遗传算法和数值模拟,建立了板料拉深成形工艺参数的优化设计模型,大大提高了优化的效率.以油底壳下盖为例,对其拉深成形工艺参数进行了优化,通过对优化结果进行数值模拟可以看出,该优化参数完全避免了各种缺陷的产生,这说明该优化算法具有较好的优化结果.     

基于蚁群神经网络的冲压成型回弹预测

拉伸是板料冲压成型的关键工艺,回弹是拉伸过程中的控制难点。笔者以板料拉伸为对象,选择材料各项异性系数、硬化指数、压边力、摩擦系数、及凹模圆角为试验参数,借助正交试验工具,进行了冲压成型数值模拟试验,并在此试验基础上建立了基于BP神经网络的回弹预测模型。针对BP算法的不稳定性,易陷入局部最优值的缺陷,设计了一种基于蚁群算法的BP网络优化算法,该优化算法融合了蚁群算法的全局性能、启发式优点和神经网络的泛化性能。利用该算法建模并将其应用于冲压成型回弹预测,结果表明:此模型可将预测误差控制在5%以内,满足工业应用标准。     

基于全局和声搜索优化的平版印刷油墨预置

采用最小二乘支持向量机建立平版印刷油墨预置模型,并提出一种全局和声搜索的优化算法来对该模型的参数进行优化。和声搜索算法是一种模拟乐队调音获得完美和声过程的元启发优化算法。将粒子群优化算法中基于种群最优来修正个体的思想与常规的和声搜索算法相结合,以实现全局和声搜索,并应用于油墨预置模型参数的优化。根据实际印刷机数据进行了仿真实验,结果验证了所提算法的有效性。     

覆盖件冲压仿真参数化建模方法

针对在覆盖件冲压成形领域对快速、自动化的有限元网格建模方法的迫切需求,提出一种快速的汽车覆盖件冲压仿真建模的思路与方法.将覆盖件冲压工艺设计与冲压成形仿真前处理集成,使用散乱三角面片模型,在自主开发的CAE前处理软件中,进行参数化的工艺补充面和压料面设计.模型的网格剖分与冲压工艺设计同时进行,自动生成整套模具的网格模型供冲压仿真计算.为了真实地模拟板料网格的流动,提出了参数化的真实拉深筋的模型建模方法和板料网格的预细分方法.完成了相关软件的开发.多个汽车覆盖件冲压工艺设计和冲压仿真计算实例说明了该方法的有效性.     

基于Dynaform的钢制车轮轮辐冲压成形有限元模拟

板料成形技术是工业领域中最重要的一种金属加工方式。利用"分解-综合"原理,对反拉深成形工步进行工艺分析,在对预拉深成形型面进行优化的同时,改进了轮辐冲压成形工艺方案。基于Dynaform冲压成形软件,建立了汽车轮辐反拉深有限元模型,并对有限元模型进行数值模拟,验证了优化过的模具型面和新工艺路线的合理性和可行性。最后,针对轮辐翻孔成形减薄严重,设计了四因素、四水平的正交试验表,通过极差分析找到了一组轮辐轴孔翻边成形最佳工艺参数。     

高强度钢冲压成形中扭曲回弹仿真与工艺参数优化

板料冲压成形过程中易出现起皱、破裂、回弹缺陷,其中高强度钢冲压件的回弹问题更为严重,通过采用板料成形仿真软件Dynaform对某汽车结构件的回弹过程进行模拟分析,结合均匀实验设计方法,用二次多项式拟合了该件扭曲回弹角与冲压速度、压边力、凸凹模间隙和摩擦系数的回归模型,得出控制扭曲回弹最优的工艺参数组合,并对回归模型进行了瞬态的灵敏度分析,结果表明,采用优化后的工艺参数使零件扭曲回弹控制良好,为预测和控制该类零件的冲压成形质量提供了良好的指     

基于有限元逆算法的拉深筋工艺设计和优化

汽车覆盖件拉深成形中，一般通过设置适当的拉深筋控制成形过程中的板料塑性流动规律来提高覆盖件成形质量。针对覆盖件工艺设计需求，提出一种基于有限元逆算法的拉深筋工艺优化算法。该算法以灵敏度优化方法为基础，考虑了板料的成形度、破裂和起皱等成形缺陷。在板料成形模拟FASTAMP系统中，开发了拉深筋优化模块，并以实际覆盖件为例，验证了该算法能快速准确地模拟等效拉深筋力的布置情况以及优化板料的成形性。     

基于人工神经网络构建优化板料拉延成形工艺模型

利用人工神经网络构建了板料拉深成形的目标函数模型,建立了板料拉深成形工艺参数和性能评价指标之间的映射关系,为各参数的研究和优化提供了重要参考.通过正交试验法对模型的训练,得到了高精度的神经网络模型.并以某后壁板为例进行拉深成形建模,通过对训练后的网络进行测试,网络误差小于5%,验证了所建网络模型的正确性和实用性,为工艺优化提供了行之有效的手段.     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.