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。     

数值模拟分析工艺参数与拉深件壁厚变化的关系

在分析板料拉深成形有限元理论的基础上建立数值模拟的分析模型,利用数值模拟技术系统地对拉深过程进行模拟。主要研究模具圆角半径、摩擦因数、压边力与模具间隙等工艺参数与拉深件壁厚最大变薄率的内在关系。     

多目标质量的覆盖件成形工艺参数优化

覆盖件冲压是复杂的塑性变形过程,成形工艺参数较多,难以精确地建立工艺参数与成形质量之间的关系。选取优化合理的工艺参数匹配是保证无破裂、无起皱和板料厚度均匀分布等成形质量的关键。通过将压边力、拉深筋高度、凸筋圆角半径、凹筋圆角半径、摩擦因数作为自变量的条件下,以正交试验为设计方案,模拟轮包覆盖件成形,获得成形质量目标破裂、起皱、厚度最大变薄率的数据。通过层次分析法计算多质量目标的权重,利用灰色系统理论,分别计算成形质量对理想单目标值的关联系数和多目标函数的关联度,进一步计算获得各成形工艺参数的平均关联度,用优化的工艺参数进行有限元模拟验证,最终指导设计、试模,板料冲压结果表明成形的质量明显提高。     

钛合金薄壁壳体强旋热力耦合有限元分析

钛合金薄壁壳体强力热旋是一个多因素耦合作用下的复杂成形过程.合理的有限元模型建立是获得该成形过程中温度场、应力场和应变场等信息的关键,从而为揭示其成形机理、合理选择工艺参数和提高成形质量提供依据.在合理地施加温度边界条件模拟外加热源,并考虑各种热效应的基础上,基于通用有限元软件ABAQUS的dynamic、temp-disp和explicit模块建立符合实际的钛合金薄壁壳体强旋热力耦合三维弹塑性有限元模型,分析TA15钛合金薄壁壳体热旋过程中温度场、应力场、应变场和壁厚的分布及旋轮圆角半径对贴模性能的影响.结果表明,摩擦生热和接触换热的作用使在旋压区沿厚度方向形成较大的温度梯度,产生明显的不均匀变形;等效应力最大值前期大多在圆角过渡区,后期大多在旋轮与板料接触区,且后期板料表面出现应力集中;越靠近零件口部,不贴模趋势越明显;随着旋轮圆角半径减小,贴模性能越好.     

基于非线性有限元的钣金件成形极限研究

用非线性有限元软件包 SHEET- FORMING研究橡皮成形工艺的模具圆角半径和板料厚度对钣金件凹凸翻边成形极限的影响 ,建立了用于预测橡皮成形工艺成败和分析其原因的极限翻边高度 h、模具圆角半径 r凹 / r凸 、板料厚度 t的曲面关系 ,用非线性有限元法有效地取代了坐标网应变法。文中主要论述 ,以圆框为对象 (L Y12 M)和用试验得到的成形极限曲线作判据 ,选取合适参数范围作正交设计 ,用动力显式算法对凹翻边破裂数值模拟并与生产型试验结果进行对比基本吻合。     

基于ANSYS的铝制错列锯齿翅片成形回弹研究

以铝制错列锯齿翅片为研究对象,利用ANSYS/LS-DYNA非线性动力有限元求解功能,模拟了翅片成形过程与卸载后回弹变形的全过程,得到了成形过程中任意时刻各处的应力、应变和卸载后板料的回弹结果。研究翅片成形过程中压边力、板料厚度、冲压速度、刀具齿形组合、刀具圆角半径等对回弹的影响。利用回弹规律进行模具补偿设计,以此优化专用翅片成形机及模具的结构参数和工艺参数,从根本上提高铝制错列锯齿翅片的制造精度,为翅片的结构优化设计提供了可靠的依据。     

拼焊板方盒件成形参数优化

通过数值模拟与正交优化的有效结合,对影响拼焊板方盒件成形因素:板料厚度比、凹模圆角半径以及坯料形状和尺寸等进行了研究.最终提高了拼焊板方盒件冲压成形深度并减小了焊缝移动.由实际冲压试验也表明:此正交设计优化方法对拼焊板方盒件冲压成形参数优化是有效可行的.     

基于Dynaform的汽车覆盖件拉延模具设计

以板料成形非线性有限元分析软件Dynaform为平台,介绍汽车覆盖件拉延模具型面设计过程,对某种汽车引擎盖冲压成形过程进行数值模拟,根据模拟结果进行成形性分析,为优化工艺参数和模具结构提供强有力的工具.     

汽车油底壳成形工艺数值模拟

采用Dynaform软件对某汽车油底壳的拉深成形过程进行了数值模拟.研究了压边力、凹模圆角半径以及有无拉延筋时对零件冲压成形的影响,通过FLD,厚薄图和成形结果对比,调整成形时压边力和凹模圆角半径,得到了优化的压边力和凹模圆角半径,为同类零件以及模具的设计提供参考.     

打火机外壳多次拉深成形的数值模拟

应用先进的有限元板料冲压分析软件Dynaform,对打火机外壳多次拉深成形过程进行数值模拟,分析模具参数及软件中参数设置的选取对成形的影响,得到合适的拉深工艺参数,为模具设计提供重要的参考.     

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...     

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。     

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.     

Fractional order nonsingular terminal sliding mode control for flexible spacecraft attitude tracking

This paper investigates a fractional terminal sliding mode control for flexible spacecraft attitude tracking in the presence of inertia uncertainties and extern...     

奥氏体不锈钢表面双辉等离子渗锆的动力学

利用双辉等离子渗金属技术在0Cr18Ni9Ti奥氏体不锈钢表面制备了一层均匀、致密、呈良好冶金结合的渗锆合金层,并对1 060℃下的渗锆动力学进行了研究。结果表明:随着距锆合金层表面距离的增加,锆元素的含量呈梯度递减,扩散系数逐渐减小,而扩散激活能逐步增大;在1 060℃采用双辉等离子技术渗锆时,渗锆合金层表层的空位密度为2.945×(1012~1013)cm-2,与相同温度下采用常规渗金属工艺相比,提高了1~2个数量级。     

气化炉三维扫描测量与数据处理

以德士古气化炉耐火砖的内壁蚀损检测设备为基础,对采集到的点云数据做了进一步处理.通过对数据的筛选和剔除,实现了数据点的平滑降噪细化和精简.然后利用点云对整、网格划分和分色显示等方法,最终完成了内壁腐蚀情况的三维建模.重点讨论了点云数据的预处理及后处理的方法,并根据内壁耐火砖的腐蚀阈值,提出了一种气化炉内壁腐蚀区域的识别与分割方法.对耐火砖的腐蚀分析、气化炉的生产与维修提供了可靠依据,并在工程应用中获得了一致认可.