高强钢板U形件热冲压技术及有限元分析

高强钢板热冲压技术是解决其冷冲压缺陷的新型加工技术.建立了U形件的热冲压有限元模型,采用热力耦合分析方法得到了热冲压过程中板料的温度、厚度及应力的分布规律,并研究板料和模具的初始温度对热冲压后制件的温度及应力分布规律的影响.结果表明,U形件压边区域、圆角处温度下降较慢,中心区域和两侧壁温度下降很快;两侧壁和圆角处减薄较大;凸模圆角处应力最大,压边区域和底部中心区域应力值最小;模具初始温度不变,板料初始温度增加,冲压结束时制件的最低温度、应变最大值随之增加,厚度最小值、应力最大值随之减小;板料初始温度不变,模具初始温度增加,冲压结束时制件的最低温度、应变最大值随之增加,厚度最小值、应力最大值随之减小.     

汽车侧门防撞杆热冲压有限元仿真分析

建立了防撞杆热冲压的力学模型和有限元分析模型,时整个热冲压成形过程进行有限元数值模拟,分析了压边力、摩擦系数等工艺参数对热冲压模拟的影响,得到了相关部件的应力、应变以及温度场分布规律.     

基于正交试验的汽车覆盖件冲压工艺参数优化

将正交试验设计方法与冲压数值模拟相结合,综合评估了冲压过程中的压边力、摩擦系数、模具间隙和冲压速度等对汽车覆盖件冲压成形质量的影响,并确定优选的工艺参数组合.以汽车翼子板为例,建立了冲压件和模具的计算机辅助工程模型.运用正交试验方法进行仿真计算方案的设计,通过对仿真数据的方差等分析,找到了最优的工艺参数组合.所得结论对冲压工艺的设计具有指导意义.     

汽车横梁拉深成形的有限元分析

建立了汽车横梁拉深的有限元三维模型，对其拉深成形过程进行了数值模拟，并与实验结果对比分析，说明数值模拟方法的可行性。在此基础上讨论了摩擦润滑条件、压边力和凸模的虚拟冲压速度对板料拉深过程的影响。通过有限元模拟分析方法得到最佳压边力数值，然后通过综合分析数值模拟结果和拉深实验结果确定了实际拉深过程中的最佳压边力。结果表明，在实际拉深过程中要尽量减小模具和板料的摩擦；在模拟拉深成形时，当虚拟冲压速度大于一定值时，会使模拟结果严重失真，因此，汽车横梁拉深数值模拟时最大虚拟冲压速度不要大于2000mm／s。     

基于有限元的高强度钢板冲压成形数值模拟应用研究

先进复杂高强度钢零件一般采用热冲压技术成形。以高强度硼钢板22Mn B5为研究对象,研究其在高温下的流变行为,对热冲压中常采用的Arrhenius本构模型进行简单的线性回归。以汽车B柱上段为研究对象,利用有限元软件对高强度钢板热冲压成形工艺进行分析,分析模具结构和压边力对成形过程的影响。从数值模拟的结果分析压边力和模具结构对板料的影响,避免成形零件出现开裂起皱现象,减少模具磨损,提高工件精度。     

汽车模具的虚拟调试

以汽车行李箱铰链安装板的模具设计为分析对象,进行了基于AUTOFORM的模具虚拟调试的研究。其中包括冲压成形数值模拟和分析,制订冲压工艺方案、确定工艺补充形式、确定合理的冲压参数,根据模拟的厚度变化、应力应变和材料FLD等方面的数据,以及成型过程中破裂和起皱的时间、部位及其几何尺寸,调整凸凹模圆角、毛坯料的尺寸、摩擦力、压边力、拉延筋的形状大小和工艺补充等相关参数,通过模具的虚拟调试,消除了冲压缺陷。     

基于LS-DYNA的板料成形数值仿真及其在轴承冲压保持架中的应用

在论述板材冲压数值模拟数学方法的基础上,运用Dynaform模拟仿真分析轧机轴承冲压保持架的弯曲、拉深、整形等冲压工艺过程,并图示给出了板料实际变形过程中发生的如起皱、拉裂、板厚变化等现象,优化了毛坯尺寸、压边力、润滑方案、模具结构等工艺设计,提出了改进模具和工艺参数的措施.     

基于正交试验的方形盒冲压工艺参数优化

以天地盖方形盒件为例，针对其冲压成形过程中常有的起皱问题，采用Autoform软件和正交试验相结合的方法，对工件分组进行仿真分析，以降低工件起皱作为优化目标，选取冲压过程中的压边力、摩擦因数、冲压速度和坯料形状4个工艺参数作为考察因素，进行工艺参数优化。模拟仿真结果表明，以上4种因素对方形盒起皱的影响程度为：毛坯形状>摩擦因数>冲压速度>压边力；且得出方形盒冲压的最佳工艺参数组合为：压边力为20 kN、摩擦因数为0.18、冲压速度为15mm/s，毛坯形状选取圆角形。     

盒型件拉深工艺参数优化设计研究

针对盒型拉深件在拉深中出现的零件起皱问题,采用正交试验方法研究凸凹模间隙、压边力、摩擦因数和冲压速度这4个因素对零件起皱的影响。利用Dynaform软件对试验进行模拟仿真,考察最大增厚率与这4个因素之间的关系,得到的成形该零件的最佳工艺参数为：凸凹模间隙1 mm、摩擦因数0.15、压边力60 kN、冲压速度6 000 mm/s。根据所得到的优化参数改进了模具结构,从而解决了零件的起皱问题。     

基于Dynaform的圆筒拉深件数值模拟

以Dynaform为模拟分析平台,对典型圆筒件拉深成形过程进行了模拟。用正交实验的方法评定了压边力、冲压速度、凸凹模间隙三个因素对零件成形质量的影响,并得到一组优化的参数值。圆筒件拉深成形相关参数的最优值压边力为20kN,冲压速度为2000mm/s,凸凹模间隙为1.1mm。     

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.