双泡径级配发泡管的研究

通过将发泡液雾化喷嘴与气泡发生器相结合,提出了一种能同时发出两种不同泡径泡沫发泡机的设计思路,并以六方最密填充理论为依据,建立了两种直径泡沫堆积的模型,以此堆积模型分析发泡管中大小泡沫的理论直径比以及体积比,小泡与大泡直径比为0.1716,大泡与小泡的体积比为10.7。将此双泡径泡沫应用于泡沫砼时,使制得的泡沫混凝土在不影响强度的条件下其容重变得更轻,节省了原材料。并根据此理论模型设计了双泡径级配发泡管的技术参数。     

聚乙烯泡沫单填充纸蜂窝夹层管的轴向缓冲吸能特性

借鉴波纹管、夹层管和泡沫填充管等设计思想,利用纸蜂窝和聚乙烯泡沫这两种优质缓冲吸能材料,提出聚乙烯泡沫单填充正多边形纸蜂窝夹层管的设计思路.通过静态和动态轴向压缩试验分析,研究这类结构的轴向缓冲吸能特性,探讨结构参数、跌落冲击参数对变形特征和关键吸能指标的影响,为其结构设计与性能优化提供参考.结果表明,在轴向静态压缩情...     

接触强度和诱导槽对泡沫铝锥管耐撞性分析

针对汽车前纵梁耐撞部件吸能盒结构形式,研究了功能密度梯度泡沫铝填充铝合金锥管在低速冲击下的耐撞性模型优化。通过对泡沫铝填充锥管的轴向低速压溃仿真分析,获得仿真变形状态、载荷及比吸能量对位移的曲线,并对比分析仿真和实验数据,证明仿真模型的有效性。以泡沫铝内核与锥管的接触强度为研究对象,研究其对泡沫铝填充锥管吸能性能的影响。最后提出基于强粘结接触模型的含有诱导槽的功能密度梯度泡沫铝填充模型,并研究其耐撞性。研究表明,具有诱导槽的强粘结泡沫铝填充锥管在碰撞中的峰值载荷更低,载荷变化更平稳,比吸能更大,是一种在汽车制造工程应用中可以考虑的新型吸能结构。     

带颗粒减振剂的碰撞阻尼器实验

带减振剂的碰撞阻尼器是在传统碰撞阻尼器的基础上发展而来,它解决了传统碰撞阻尼器能量无法完全耗散,对低频振动效果差等问题。但由于该阻尼器在加入减振剂后,决定其减振性能的参数也随之增多,各参数之间相互影响,无法找到一个最佳取值,使阻尼器的减振性能无法得到充分发挥。为此通过在悬臂梁上对带减振剂的碰撞阻尼器的实验研究,最后得出阻尼器填充率,间隙,填充介质等参数之间的联系。实验结果表明,不能单纯考虑填充率和间隙对阻尼器的影响,要综合考虑两者之间的关系,当阻尼器中冲击器的活动范围为其自身几何尺寸的1.4倍左右时减振效果最好,并且填充粒径更小的减振剂其减振效果更好。通过填充合适的的减振剂可以使阻尼器的减振性能得到最大的发挥。     

双泡发泡管的发泡动力学分析研究

孔板是双泡径级配发泡管中重要的阻力平衡元件,其厚度、开孔率、孔径大小、布孔方式等结构参数的设计都会对发泡管的系统阻力平衡产生重大影响,同时会对气液发泡材料的均匀分布产生影响。通过对发泡管管路中系统阻力平衡的研究,得出结论:需要不同的泡径比时,要求不同的填充状态和不同的孔板结构,每种填充状态下的管路都有一个对应的最佳孔板结构,使管路系统能按设计的泡径要求进行发泡,同时使系统阻力平衡,从而使发泡效果最优。     

新型混泡管的数值模拟研究

通过计算流体力学(CFD)软件FLUENT,采用多相流mixture模型对使用不同混泡结构单元的混泡管进行了三维数值模拟,在现有的混泡技术上进行改进和创新,进一步优化泡沫混凝土混泡设备参数。结果表明,两种高粘度的非牛顿流体进行多相流混合时,不同的混合元件的混合效果是不同的。螺旋和扭转类混合元件的混泡效果明显好于扇叶结构,可在较短的混泡管内快速均匀的实现水泥浆体与泡沫流体的混合。但是分段扭转片状的混合元件可以实现更加稳定的混合效果,同时沉降作用最小。确定了该结构参数下的最佳混泡管长度为700mm。数值模拟可详细描述混泡管内的混合过程,并为新型混泡管的研发提供数据参考,为提高泡沫混凝土生产效率和产品质量提供有力的理论支持。     

泡沫铝填充结构机床工作台结构优化设计

为了最大限度地提升泡沫铝填充结构机床工作台的轻质性和静、动态性能,对前期设计的该结构工作台进行优化设计。优化设计过程中设定工作台的总体质量最小为目标函数,铸铁层外壳的厚度尺寸为优化变量,工作台的最大应力和最大变形量为约束条件。然后对优化前后的泡沫铝填充结构机床工作台的静、动态特性进行有限元仿真分析,对其质量进行计算,并将两种结构工作台的静、动态特性和质量进行比较。结果表明,优化后的泡沫铝填充结构机床工作台的轻质性和高静、动态性能更显突出。     

基于COMSOL的泡沫铝阻性消声器消声性能研究

基于Delany-Bazley-Miki多孔介质声学模型,运用COMSOL有限元软件计算了泡沫铝阻性消声器的传递损失,研究和分析了消声器内部穿孔管穿孔率、壁厚、孔径以及泡沫铝吸声材料厚度、流阻率、空气背衬等结构参数对其消声性能的影响。结果表明传递损失随结构参数的变化基本呈现周期性规律,其中穿孔管穿孔率较小时消声性能较差,泡沫铝材料厚度在不同频段时对其传递损失的影响不同。     

高孔率泡沫金属的孔结构保形铣削加工研究

为避免高孔率泡沫金属的孔结构在加工过程中变形,提出一种利用填充材料进行泡沫金属固化后再进行孔结构保形铣削加工的新方法。首先对不同填充材料的泡沫铜进行铣削加工试验,然后利用SEM图进行表面形貌分析,选用孔径保形率、孔嵴保形率以及透气性来评价泡沫金属铣削加工的保形效果。基于中心组合试验,以孔径大小和0.7 kPa压力下的流量值为指标,建立二次回归方程并计算出在选定填充材料条件下的泡沫铜的优化加工参数。研究结果表明,以氢化松香-硬脂酸钠按质量比4:1混合的固化填充材料可以使得泡沫铜在铣削加工过程中获得较好的保形效果。孔径保形率、孔嵴保形率以及透气性性能均随主轴转速、进给速度呈先增加后降低的趋势。同时,在选择优化填充材料的条件下,主轴转速为311 r/min,进给速度为165 mm/min时,铣削加工泡沫铜具有较好的保形效果,其孔径保形率可达96.3%,且在0.7 kPa的压力下,流量值达7.36 L/min,具有较好透气性,实现了具有较好保形效果的泡沫铜的铣削加工过程。     

钢纤维树脂混凝土填充结构机床基础件研究

以CW6163E机床床身为实例,初步设计了钢纤维树脂混凝土填充结构机床床身(为方便起见,以下简称为填充结构床身),并通过ANSYS对原型床身和填充结构床身的静动态性能进行分析,验证填充结构床身可提高机床的静动态性能.对填充结构床身进行了结构优化,并对优化后床身静动态性能进行静分析,结果表明,优化后的填充结构床身在提高机床静动态特性、节省能源、降低成本、利于环保等方面可更显优越性.     

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.