基于流体动力学的弯管应力有限元分析

由直管弯制而成的弯管几何形状和结构复杂,在流体作用下受力复杂,准确的应力分析是进行强度计算和弯管设计的重要前提。使用ANSYS流体-固体有限元分析软件,建立了管内流体动力学分析和弯管结构应力三维分析模型,利用两种不同物理环境的转换,得出了弯管在流体不均匀压力作用下的应力分布,讨论了流量、弯管加工缺陷对弯管应力的影响。     

导流管的流速分析

流速分析是弯管结构可靠性分析和寿命分析的重要前提。文中主要讨论使用ANSYS有限元分析软件,建立弯管内流体动力学分析和结构应力分析模型,数值模拟分析弯管的受力状况及边界条件,对弯管进行二维非线性应力分析,同时探讨了弯管结构、流体流量参数对弯管应力的影响。     

基于流固耦合的弯管应力有限元分析

弯管在流体作用下受力复杂,准确的应力分析是进行强度计算和弯管设计的重要前提.本文使用ANSYS流体-固体有限元分析软件,建立了管内流体动力学分析和弯管结构应力三维分析模型,利用两种不同物理环境的转换,得出了弯管在流体不均匀压力作用下的应力分布.     

基于流固耦合的泥浆泵剪切阀出口弯管应力与疲劳分析

泥浆泵剪切阀出口直角弯管在流体作用下受力复杂,准确地研究直角弯管内流体的流场以及分析弯管的应力和疲劳强度,对弯管结构可靠性分析和寿命分析起到非常重要的作用.运用软件FLUENT和ANSYS,采用物理环境顺序耦合法进行流固耦合数值模拟,得出了弯管内的流场分布以及弯管在不均匀压力下的应力分布和疲劳寿命规律.该方法对钻井现场施工的安全评估具有重要的意义.     

平板折弯节能型扰流子对弯管压力降影响的数值模拟

高速流体流过弯管时,在弯管内侧面出现分离流和二次流现象,导致流体能量损失。为了降低由于流体碰撞管壁造成的能量损失,以直径300mm的管道为研究对象,设计了一种安装在弯管前端的异形扰流子,以期减小弯管处压力损失。运用计算流体力学软件FLUENT,采用RNG k-ε模型和SIMPLE算法求解不可压缩Navier-Stokes方程,在5种雷诺数下对加装不同结构参数扰流子的弯管进行全流场数值计算,分析扰流子叶片转角、叶片长度和扰流子安装距离对弯管进出口压力降的影响。结果表明:在不同雷诺数情况下,未加装扰流子弯管数值模拟结果与理论计算结果基本一致;扰流子叶片转角α和长度L均对弯管压力影响显著,能够有效降低弯管进出口压力损失。     

液流冲击作用下的管道振动特性研究

研究了弯管在阀门快速开启过程的振动现象,对流体选用S-A(Spalart-AIlmaras)湍流模型进行了流动模拟,建立了弯管和流体的有限元模型;对阀门进行流固耦合仿真,分析研究了三种不同流速下的弯管振动情形,并绘制了相关节点的位移-时间曲线.结果表明,随着弯管内流体的流速增大,弯管所受应力增大,弯管振动也更激烈.     

飞机复杂燃油管路压力动态研究

为研究飞机加装管路系统传输过程中的压力瞬变特性，文章通过分析给出了流体及结构的动特性方程，提出了研究流体结构相互作用（FSI）的MOC-MOC和MOC-FEM方法。该方法应用于管末端设有加油控制活门的单直管及弯管的管路系统，对在加油控制活门快速关闭时水锤诱发的流体动态压力进行分析，并充分考虑长管道连接部位的FSI现象。试验结果表明仿真与实际结论吻合良好，验证了分析方法的合理性和正确性。     

基于Fluent的混合弯管流场的数值模拟

弯管在工业生产的各个领域正得到越来越广泛的运用。以工业生产最常见的一种弯管体为研究对象,利用计算流体力学技术,首先对弯管体进行物理建模,设定各项基本参数,通过FLUENT软件对弯管内温度、压力、速度等参数做了全面详细的二维数值模拟,最后将计算结果进行图形化显示,得到了各项设计指标的极值及其所在部位等重要的设计及优化依据,形象具体的研究分析了弯管内流体状态。     

TBM液压弯管动态特性分析

针对硬岩掘进机(Tunnel boring machines,TBM)上外激励改变弯管动态特性导致其传递效率降低的问题,利用双向流固耦合的方法,建立了流体域和固体域的仿真模型。运用有限元分析软件求解了弯管的应力,发现求解结果和试验结果具有很好的一致性。对比分析了有无基础振动下弯管的动态特性;研究了不同的外激励基础振动参数和弯管的结构参数对弯管动态特性的影响规律。结果表明:应用双向流固耦合的方法更清晰地反映了弯管在强振动环境下的动态特性,为弯管的设计和选型提供一定的参考。     

应用ISIGHT的大型弯管环柔性焊接技术可靠性研究

针对现有焊接技术未考虑大型弯管的各项参数变化，导致焊接结果难以满足实际产品性能要求的问题，提出引入ISIGHT软件，构建大型弯管环柔性焊接技术可靠性优化方案。利用ISIGHT中多目标优化算法自动确定目标权重值，计算出最优解集；再根据6Sigma设计方法和蒙特卡洛抽样技术分析大型弯管的可靠性和质量，并将裂纹、未焊透、残余应力和孔穴四种缺陷作为参数和目标，分别计算出每一种缺陷的许用值和性能函数，在此基础上完成焊接技术可靠性优化模型。通过仿真实验结果表明，使用所提方法进行优化后，各项参数得以提升，应力和位移均在阈值以上，相比文献[3]方法和文献[4]方法，这里方法应力具有较高的可靠性，能够满足工程设计条件。     

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.