基于Voronoi方法的梯度点阵结构力学性能的研究

通过设计不同梯度的结构，可提高点阵结构强度，改善其抗冲击、吸能减振等力学性能。利用Voronoi方法，在欧拉几何空间域内产生随机点，形成基本单元结构，并设定不同梯度单元结构的分布形式，最终生成具有不同梯度的点阵结构。共设计“向内”梯度和“向外”梯度两种形式，每种形式又分别设计了梯度等级为0.5、0.6、0.7、0.8和0.9共五个不同的点阵结构。当梯度等级为1时，是均匀点阵结构，即结构的梯度随等级变大逐渐呈现均匀化。利用Abaqus有限元分析软件对不同梯度的点阵结构进行压缩力学性能仿真分析。利用3D打印技术制备点阵结构，并进行力学压缩试验，验证有限元分析结果。有限元和压缩试验结果表明，与均匀点阵结构相比，具有梯度的点阵结构力学性能更好；在“向内”梯度点阵结构中，梯度等级为0.6的点阵结构力学性能最佳，具有很好的抗冲击和减振性能；“向外”梯度点阵结构中，梯度等级为0.8的点阵结构更有利于抵抗冲击力，起到吸能减振的作用；“向外”梯度点阵结构整体性能要优于“向内”梯度点阵结构。基于Voronoi方法设计的梯度点阵结构具有高强度、抗冲击和吸能减振等良好的力学性能，点阵结构的力学性能与梯度等级有...     

基于SLM工艺的变截面四棱锥点阵结构建模与试验研究

球型增强变截面四棱锥点阵结构（Spheriform graded body-centered cubic,S-GBCC）可以有效改善常规四棱锥点阵结构（Body-centered cubic,BCC）节点应力大、梁受力不均等缺陷,是一种力学性能更优的点阵构型,但其力学特性受单胞尺寸、梁的截面特性、节点连接方式等影响。考虑变截面梁和连接球体的几何构型,完成S-GBCC点阵结构的几何拓扑分析;基于铁木辛柯梁理论建立其力学与数学模型,得到点阵尺寸参数与相对密度、等效弹性模量、等效屈服强度之间的函数关系。利用选区激光熔融（Selective laser melting,SLM）工艺制备同一相对密度条件下,不同曲率半径的S-GBCC点阵结构,分析不同规格打印试样的形貌特征,形成考虑SLM工艺成形精度影响的S-GBCC点阵结构等效力学模型。完成该点阵结构静态压缩试验,分析其形变特性和力学性能,结果表明较传统BCC点阵结构有显著提升,理论与试验结果吻合较好。     

基于正交试验的液冷板散热性能的研究

根据电子设备工作时局部热耗过大的状况,设计了小通道液冷冷板。利用ICEPAK仿真软件,分别对小通道冷板和普通S型流道冷板进行散热性能研究,研究发现小通道冷板的散热效果明显优于普通S型流道冷板。对小通道结构参数（肋片间距、厚度）及进口处流量进行单因素分析,研究其对冷板散热性能的影响。通过正交试验的极差分析,各因素的影响顺序为：进口流量>肋片厚度>肋片间距。该分析结果为高功耗电子设备的散热设计提供理论参考。     

SLM制备的Ti6Al4V轻质点阵结构多目标结构优化设计研究

体心立方(Body-centered cubic,BCC)点阵结构作为目前被广泛关注的点阵材料构型,其拓扑类型简单、SLM(Selective laser melting,SLM)成型可靠性好、压缩失效形式单一,但存在着承载能力相对较差的缺点。为探寻兼具轻质与高强性能的点阵构型,首先解除BCC点阵单胞各向尺寸相同的约束,提出体心四方(Body-centered tetragonal,BCT)点阵结构一般模型。然后,以BCT单胞构型尺寸为设计变量,以点阵材料尺寸与成型工艺为约束条件,以相对密度、初始刚度、塑性破坏强度为多目标评价函数,建立BCT点阵结构构型尺寸的多目标优化数学模型,采用理想点法求解得到BCT点阵单胞综合最优构型尺寸,并与BCC参照结构进行实例仿真对比分析,论证BCT优化结构相比BCC参照结构在性能上的优势。最后,采用Ti6Al4V材料通过SLM方法制备BCT优化结构与BCC参照结构的实验样件,并进行准静态单向压缩性能实验,验证理论分析结果的正确性,为轻质点阵结构材料的设计与研究提供了理论参考。     

基于能量均匀化的高剪切强度周期性点阵结构拓扑优化

传统多孔结构构型型式单一、缺乏科学设计方法的指导,为了从拓扑构型角度设计抗剪切性能更优的周期性点阵结构,基于拓扑优化技术,以周期性单胞为研究对象,以其切变模量最大为目标,以结构的材料用量和力学控制方程为约束条件,利用能量均匀化方法建立基于宏观力学性能的细观点阵结构的优化模型,通过改进的优化算法求解模型,得到了一种宏观上的拓扑边界清晰的周期性点阵结构。然后根据优化结果,在考虑胞元非等壁厚和横向剪切变形影响条件下进行等效材料力学性能分析,得到剪切性能关于微结构胞元几何参数的表征,同时加工制造了优化得到的周期性点阵结构,并进行了剪切力学性能测试。从理论分析和性能试验两个方面与六边形蜂窝结构相应的切变模量进行对比,结果表明,经优化得到的周期性点阵结构切变模量有大幅提升、抗剪切性能更优越。验证了所提出方法能有效地应用于周期性点阵结构抗剪切性能的优化设计。     

某新型液冷机箱热设计的数值研究

针对目前机箱整体散热性能较差的问题,根据机箱内部安装插件热耗的不同,采用新型并联S型流道液冷散热模式。通过在冷板合适位置布置散热翅片,优化了流道的结构形式,成功设计了一款新型液冷机箱。利用数值模拟与试验相结合的方法对机箱散热性能进行分析,结果表明,新型并联S型流道设计改善了流道流场,提高了上、下冷板的传热系数,使机箱的整体散热能力得到了有效增强。同时,该机箱将三维立体流道降为二维平面流道,成型简单可靠,从而使机箱具有更高的环境适应性。通过热设计分析可知,该液冷机箱可容纳多个高热流密度的插件,具有一定的工程应用价值。     

高功率雷达冷板的流动性及散热性研究

针对某型雷达高功率且热流密度大模块,采用液冷强迫对流方式解决系统散热问题,分析了影响液冷冷板流量分布特性和散热特性的因素;基于搅拌摩擦焊技术的复杂流道焊接工艺,提出了三种流道结构形式冷板。依据单一变量原则,分别以流道宽度、深度、冷却液等效入口流速为变量,对不同流道结构冷板进行流动性及散热性研究,试验表明了为提高冷板流动性能和散热性能,应综合考虑冷板流道宽度、深度、冷却剂流速等因素影响;另外,O型结构冷板的综合流动性能和散热性能优于其他两种结构形式冷板。     

一种弹载电子产品储热装置的设计与试验

为满足某弹载电子产品在高温环境中工作的需求,设计了一种储热装置对该产品进行有效温控。根据该产品的工作特性和相关技术要求进行储热装置的结构设计,分别用H62黄铜、5A06铝合金和泡沫铜基石蜡相变材料制作了具有同样结构外形的储热装置。设计制作与产品热耗一致的模拟热源用于储热装置的性能试验,对3 种储热装置的储热能力、导热能力等物理性质进行对比分析。结果表明,相变材料储热装置可以满足温控需求,并在储热能力和重量上有明显优势,值得在同类型产品平台中推广和应用。     

微通道冷板的加工工艺及散热性能研究

文中阐述了微通道冷板的结构设计原则,给出了一种适用于微通道冷板的机械加工及焊接工艺方案.对冷板试验样件进行了焊接质量、密封性及强度检测试验,确定了其结构设计变量的合理取值.通过对比两种工艺性结构形式下冷板试验样件的散热性能数据,得到了微通道冷板焊接方案的选用方法,相关结论可为同类型的冷板设计提供工程设计参考.     

一种全封闭蒙皮点阵支撑结构的优化设计与试验验证

随着人类航天活动范围的不断扩大,复杂航天任务对于结构轻量化技术提出了更高的要求。在传统的结构形式基础上,单纯通过应用高性能材料等手段已经无法满足后续航天任务对于航天器载荷支撑结构轻量化的要求。提出一种封闭蒙皮包裹三维点阵层级结构的设备支撑结构形式,建立设备支撑结构的拓扑优化设计模型,并对优化后的结构进行封闭蒙皮包裹三维点阵化设计。运用激光选区熔化方法制备了支撑结构实物,并进行了振动力学试验验证,试验结果表明设备支撑结构比采用传统设计及制造方法的结构减重46.4%,实物已应用于某型号卫星载荷支撑任务。提出的封闭蒙皮包裹三维点阵的结构形式可以有效提高支架类结构的设计效率,在航天器结构轻量化方面具有推广应用前景。     

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.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.