深孔钻削双锥面负压系统研究

通过对现有DF深孔钻削系统的结构及工作原理的理论分析,研究新型双锥面负压射流结构、负压机理及排屑特性,提供一种排屑能力更强、工艺性更好、加工精度和生产效率更高、孔径实用范围更广的新型深孔钻削双锥面负压装备,应用于ZK2138深孔钻床,结合理论分析,进行正交化设计试验,最终确定新型双锥面负压射流通道的合理几何参数.     

深孔钻削双锥面负压排屑系统数值模拟与试验研究

以深孔加工单锥面负压排屑系统为设计依据,根据流体力学理论设计双锥面深孔负压排屑系统,并建立流体力学模型与数学模型.利用计算流体力学(FLUENT)技术,对一系列不同负压结构进行了数值模拟.模拟过程入口与出口均采用压力边界条件.分析排屑通道压力与速度变化曲线,得出排屑通道内流体的压力与速度变化规律.通过与实验结果进行对照发现,射流喷嘴大小以及角度是影响深孔排屑的重要因素,而且与单锥面负压排屑系统相比,双锥面负压抽屑效能明显增强.     

深孔加工负压排屑系统的优化设计仿真研究

在机械制造业中,孔加工是一大难点,深孔加工又是最困难的一种。研究负压排屑系统对深孔加工的排屑这一难题有重要意义,尤其在准干式深孔加工中。通过对已有深孔钻削负压系统工作原理的理论分析,且对深孔加工负压系统中的流体建立了数学模型,文中提出一种新型高效的双曲面负压系统,并利用Fluent软件进行流体运动的压力场和速度场仿真分析。通过对比负压系统的总压速度云图、总压和速度XY散点图,研究结果表明:双曲面结构比锥面结构的负压效果更明显,试验结果与理论分析相吻合。     

深孔加工负压系统优化设计

负压系统对深孔加工排屑这一难题有重大意义,尤其是在准干式深孔加工中。通过对已有深孔钻削负压系统工作原理的理论分析,文章提出一种新型高效的双曲面负压系统。并利用Fluent软件进行流体运动仿真,且将此负压系统应用于ZK2138深孔钻床进行试验。研究结果表明:相对于锥面负压系统,双曲面负压系统的负压效果更加显著,试验结果与理论分析相吻合。     

负压排屑装置楔形结构优化设计与仿真

为解决超大长径比深孔加工排屑困难问题,在分析DF系统负压排屑作用机理的基础上,建立负压射流模型,通过采用填充部分前/后分离区所占区域的方法,设计了一种位于射流喷嘴处的楔形结构,以减少前/后分离区的能量损耗。理论计算及Fluent仿真优化实验结果表明,该楔形尺寸在长度L1=75 mm、宽度L2=1 mm时效果最好,切削液流速增大约10.07%,湍流动能增大约11.39%,负压区压力值减小约79.26%,该楔形结构提高了负压排屑能力,最大程度地减少了前/后分离区的能量损耗。     

深孔加工前置射流孔负压抽屑装置优化设计

为解决大长径比深孔加工排屑困难问题,在分析DF系统负压排屑作用机理基础上,建立负压射流模型。针对前分离区涡流现象导致的能量损耗,提出采用两级喷射方式,在前分离区位置增加射流孔,使部分射流油液通过该孔进入前分离区,减小前分离区不必要能量损耗,从而增大负压值,通过理论分析及Fluent仿真优化实验,证明射流孔位于主喷嘴前部1 mm,排布方式为周向12个,直径0. 3 mm时效果最好,前分离区域最小,负压区域最大,负压区压力值降减小低约25%,最大程度的降低了前分离区域能量损耗,增强了负压排屑能力。     

深孔加工脉冲负压排屑装置的设计研究

深孔DF系统的负压排屑装置采用恒压供油,易产生堵屑现象.针对此问题,设计了一种脉冲式供油装置,建立了该装置的脉冲流体数学模型.基于FLUENT软件对脉冲式供油时,不同射流速度产生的负压效果进行了仿真试验,得出了脉冲式供油能使排屑通道中产生不断变化的负压值.研究结果表明:基于负压排屑理论设计的脉冲负压排屑装置能有效改变排...     

深孔加工负压排屑装置收缩环状结构优化设计

为解决超大长径比深孔加工排屑困难问题,在分析DF系统负压排屑作用机理的基础上,建立负压射流模型。采用一种位于射流喷嘴前部收缩环状切削液通道,取代前分离区所占体积的方法,降低该区域造成的能量损耗。通过理论计算以及Fluent仿真优化试验,证明该收缩环状通道设计的椭圆尺寸在长半轴x=20mm、短半轴长y=2mm时效果最好,切削液流速提高约9%,湍流动能提高约6. 75%,负压区压力值降低约70. 43%,最大程度地降低了前分离区域能量损耗,增强了负压排屑能力。     

基于FLUENT软件的深孔加工负压抽屑装置分析研究

负压抽屑装置是保障深孔加工排屑顺畅的有力手段。本文提出建立充分考虑流量、流速、间隙宽度、喷射夹角等影响因素的负压抽屑数学模型,分析这些因素对抽屑效果的影响,并利用FLUENT软件对有无负压抽屑装置情况下分别进行仿真对比,量化研究其抽屑效果。结果表明:射流喷嘴的间隙和喷射角是影响负压抽屑效果的关键因素;无负压装置时,切屑在排屑通道中只受到推力,并且随位移逐渐减弱;当推力减小到小于阻力时,切屑容易在排屑口尾部滞留,发生堵屑现象;加载负压抽屑装置时,在排屑通道尾部形成压力差,产生3倍于排屑通道推力的吸力,使切屑在通道尾部受到一个强力的加速度,克服切屑阻力,排屑效果提高了200%。     

深孔机床DF系统射流间隙的结构与参数分析

为提高深孔机床的排屑性能,以现有深孔机床DF(Double Feeder)系统为基础,应用Fluent软件对DF系统射流间隙的结构进行仿真研究。将射流间隙由直线型改为锥线型,并且设置合适的喷嘴收缩角、过渡段长度与出口直径比后,可以使射流间隙造成的能量损失最小。所做研究可以为提高深孔机床DF系统的负压抽吸效果与结构参数优化提供理论参考。     

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...     

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.     

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....     

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.     

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.