考虑发动机系统耦合振动影响的配气机构动力学分析

配气机构的动力学性能研究是发动机开发的重要组成部分。为研究发动机系统耦合振动对配气机构动力学性能的影响,基于运动机构的振动响应分析方法,建立了配气机构、活塞、连杆、曲轴和机体的发动机耦合振动分析模型,计算了配气机构的动力学性能参数。通过与配气机构单体分析模型的结果进行对比分析,明确了发动机零部件弹性振动对凸轮-挺柱接触应力、凸轮轴扭转及弯曲振动、气门开启及落座过程中的振动冲击、气门落座后的残余振动、气门弹簧颤振的影响机理。     

浅谈发动机配气机构优化改进设计

配气机构是发动机重要的组成,配气机构功能要按照发动机各气缸工作循环与发火次序要求对进、排气门进行定时开启与关闭。发动机动力和经济的性能是不是具有优越性和可靠性,将噪声和振动控制到较低限度内,这都与配气机构的设计有着直接的关系。配气机构要具备良好换气性能和良好运动学、动力学的性能,保持平稳工作和低振动,小噪声。本文通过对配气机构的研究与优化改进设计,将理论与实际应用结合,为发动机配气机构的设计积累经验。     

基于模糊综合评判的部件失效区域的确定

应用模糊方法评估部件振动可靠性时，需构建部件振动的模糊共振区域及相应的隶属函数和模糊强度失效区域及相应的隶属函数。针对航空发动机关键部件振动可靠性评估中影响部件模糊共振失效区域及其隶属函数、模糊强度失效区域及其隶属函数确定的众多复杂的、非确定的、时变的因素，将二级模糊综合评判方法应用于航空发动机关键部件模糊共振失效区域及其隶属函数、模糊强度失效区域及其隶属函数的确定，采用层次分析法(AHP法)确定评价指标权重，建立确定模糊共振失效区域及其隶属函数、模糊强度失效区域及其隶属函数的数学模型和流程。结果表明，该方法能够解决航空发动机关键部件模糊共振失效区域及其隶属函数、模糊强度失效区域及其隶属函数确定中一些复杂因素的处理问题。     

基于CAD/CAE集成的发动机配气机构数值研究

通过建立发动机配气机构数值研究流程,将传统的经验设计理论与先进的专业软件应用结合起来,并将配气机构的设计、运动学分析、动力性分析、发动机换气过程优化、凸轮轴有限元分析以及配气机构对整机噪声和振动的影响等完全融合在一起,探讨了一种新颖的、基于CAD/CAE集成开发的发动机配气机构数值研究的思路和方法。     

基于多失效模式相关分析的技术特征综合配置方法

通过分析机械可靠性设计相关研究工作的研究成果与不足,提出新的基于可靠性功能配置的技术特征配置方法。该方法利用可靠性功能配置的矩阵分解结构描述失效发生机理、软失效和硬失效模式三者之间的复杂关联关系。从考虑零部件多失效模式相关性的角度,提出各失效模式对零部件整体造成的可靠性损失的定义,并建立了可靠性损失的分析与计算模型。按可靠性损失的大小将零部件可靠性指标值分配给各个失效模式。在可靠性指标值分配基础上,利用逆可靠度法求解零部件技术特征值。以加工中心传动系统的研发为例,说明了所提方法的可行性和有效性。     

应用模糊方法计算构件振动可靠性

分析影响构件振动可靠性的不确定性和模糊性因素，定义构件振动模糊安全状态，构建构件振动的模糊共振失效区域及相应的隶属函数、模糊强度失效区域及相应的隶属函数，建立构件振动可靠性计算的模糊模型，并将其应用于某航空发动机压气机、涡轮叶片的振动可靠性计算。研究结果表明，应用模糊方法评估构件振动可靠性是可行的。     

内燃机配气机构技术现状及发展

配气机构控制内燃机的换气过程,其设计的优劣直接影响内燃机的可靠性及性能。介绍了内燃机配气机构的国内外研究状况;通过分析配气机构的工作原理,提出设计配气机构时存在的矛盾以及当前已得到广泛应用的配气机构的研究方法。对现代发动机配气机构采用的先进技术进行总结分析,对其发展方向进行展望,从而为配气机构的相关性能研究提供判断依据．为内燃机配气机构的优化设计提供参考。     

探析内燃机配气机构的技术现状及发展

内燃机可靠性及性能的发挥主要是靠配气机构控制内燃机的换气过程的结构来决定的,笔者整理了国内外内燃机配气机构的研究现状,然后研究配气机构的工作方法,并指出设计配气机构时存在的问题以及目前已被证明和广泛推广的配气机构的研究方法,最后选择先进的技术对当代发动机配气机进行分析,为内燃机配气机的合理设计提供依据。     

随机结构系统振动的频率可靠性分析

根据随机结构的固有频率与激振频率差的绝对值不超过规定值的关系准则，定义随机结构振动问题的可靠性模式和系统的可靠度，提出避免共振的频率可靠性分析方法，应用随机摄动技术和可靠性理论，对随机结构系统共振问题的准失效分析方法进行探索。     

斯特林发动机配气活塞与气缸的间隙设计与仿真

随着能源危机的加剧和斯特林发动机技术的提高,斯特林发动机在车辆上的应用具有重要的意义,其中配气活塞与气缸间隙的合理设计是斯特林发动机设计的一个重要课题。首先,分析了影响配气活塞与气缸工作间隙的各个因素所造成的间隙特征,提出了配气活塞与气缸的间隙设计方法,利用该设计方法确定了发动机的配缸间隙,并利用ADAMS软件进行了仿真验证,得到活塞与气缸的最小配缸间隙为0.168mm,稳态振动中活塞与气缸的最小径向间隙为0.0145mm,为该类型发动机设计提供了参考依据。     

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.