发动机附件机匣振动分析与故障排除方法

针对典型的发动机附件机匣振动超限情况,分析PULSE振动分析仪采集的振动信号,确定了固有频率共振是引起发动机附件机匣振动超限的主要原因.应用锤击法进行的试验证明,固有频率共振是由振动传感器、振动支架安装到发动机附件机匣上以后产生的,4轴对应的齿轮啮合频率振动激发了系统固有频率共振,使其振动超限.工程上采取两种方法降低附件机匣振动,一是在振动支架上安装辅助重物改变系统固有频率,避免产生固有频率共振;二是调整发动机附件机匣安装状态,降低基础振动水平.     

配气台管路系统气固耦合振动特性分析

针对配气台管路振动问题,采用传递矩阵法和有限元模态分析法,建立管道系统振动频率的计算模型。运用MATLAB,ANSYS和AMESim软件分析计算,得到气柱固有频率、结构固有频率及扰动频率三者之间的关系,确定配气台管路振动的原因,并提出有效的解决措施。研究表明:由于扰动频率与管路内气柱低阶固有频率相近,激发配气台管路剧烈共振,通过增加阻尼孔板和增加管路支撑,改变了管路内气柱固有频率和结构固有频率,有效的解决了配气台管路共振问题。     

金刚石圆锯片振动模态及频率可靠性分析

为提高金刚石圆锯片的锯切性能,降低其工作时的振动,防止锯片共振,通过锤击振动试验法,分析锯片固有频率的概率特性.依据结构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,定义了锯片振动问题的可靠性模式和可靠度,提出避免锯片共振的频率可靠性分析方法.并通过对不同转速下的锯片可靠度的分析,得到了防止共振的工作转速,提高了金刚石圆锯片的使用寿命.     

压缩机进气洗涤罐的固有频率计算

对于工作压力较高的洗涤罐,其固有频率不是太高,为了防止固有频率与气流脉动频率发生共振,就应对固有频率进行计算,适当调整洗涤罐的结构尺寸,使其固有频率不是气流脉动频率的整倍数,从而避免共振.     

高固有频率构件分频共振时效的分析计算

利用力学、线性和非线性振动理论,对高固有频率构件进行振动时效的新方法－－分频共振的原理和应用进行了讨论。指出对同一构件进行振动时效处理,要达到相同的时效效果。分频共振方法所用的激振力比直接共振方法所用的激振力要大些。从理论上说明了分频的方法是行之有效的方法。     

电梯系统动态固有频率分析

以某型号电梯为参考原型,详细介绍了电梯在运行过程中出现的振动现象,在分析和合理简化的基础上,建立了电梯系统振动数学模型,运用振动理论分析了发生振动的原因,找出了系统共振发生的频率带,提出了变刚度电梯模型补偿策略的解决方法,结果表明改进后的电梯系统固有频率与曳引机激振频率一直不会相同,有效地防止了共振的发生,同时也减少了工作中的振动,提高了电梯的运行性能和安全性能,为以后的研究提供了一种有益的方法。     

基于模态分析方法的风机底座结构优化

针对某风机运行时机脚振动偏大的问题,通过试验研究发现风机底座的固有频率值接近风机机脚振动峰值频率,因此认为两种频率共振是引起机脚振动偏大的主要原因之一。通过加强底座刚度设计了四种底座优化结构。利用有限元软件进行模态计算,选取最优的底座结构,比较优化前后的机脚振动,发现优化后底座的机脚振动值降低了2.1dB(线性计权)。     

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。     

基于质点模型的船用空压机振动诊断与分析

针对某船用空压机出现的振动故障问题，进行设备振动测试，得出振动的主要频率为空压机的基频。通过建立质点有限元模型，进一步明确振动的具体原因是空压机基频激励引起的系统共振。经过分析给出具体的振动控制措施，通过调整隔振器刚度改变空压机隔振系统的固有频率，从而避免空压机额定转速激励下的共振现象。在实船对空压机进行振动复测，设备振动速度总值由原先的船宽方向61.3 mm/s、船长方向28.4 mm/s、垂向33.5 mm/s，降低到船宽方向22.7 mm/s、船长方向19.3 mm/s、垂向26.2 mm/s，振动水平满足标准限值要求，说明振动问题得到有效解决。该研究可为船用机械设备出现异常振动时的判断、识别以及治理提供十分有益的参考。     

圆筒浮标式波浪发电装置的共振系统分析

为了分析圆筒浮标式波浪发电装置振幅随激扰频率的变化情况。通过对共振系统建立自由振动微分方程和在浮筒位移激励下的振动方程并求得共振系统稳态解,最后对共振系统参数确定并对共振系统进行仿真分析。研究结果表明:通过对自由振动微分方程和在浮筒位移激励下得振动方程求解,根据重锤的振幅和共振理论,计算出弹簧的弹性系数k=26.40N/mm和系统阻尼系数c=37.83,通过matlab仿真分析,能够清晰的得到重锤的振幅随激扰频率的变化情况,因此可以通过合理的设计影响参数,改变使发电机构的固有频率等于或接近波浪的固有频率,俘能装置发生共振,使其驱动的性能大大提升,从而提高发电效率。     

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.     

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....     

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。     

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.