动力响应问题的摄动Riccati传递矩阵方法

基于Riccati传递矩阵法,给出了一维不确定参数结构系统动力学响应问题的二阶摄动计算方法。该方法在用于一维结构系统动力响应问题的摄动分析时,不需要按振型展开,避免了基于有限元的矩阵摄动方法所带来的模态截断误差问题,提高了分析结果的精度。以多跨转子——轴承系统为模型,导出了动力响应问题摄动R iccati传递矩阵法的具体计算公式,并编制了相应的计算分析程序。算例对弹性支承的等截面梁的动力响应问题进行了摄动分析,摄动计算结果和精确计算结果吻合良好。     

一维结构系统重频特征问题的摄动传递矩阵法

基于传递矩阵法，给出一维结构系统重频振动特征问题的二阶摄动计算方法，该方法适用于一般的一维结构系统的实数和复数重频振动特征问题的摄动分析，并且可避免模态截断误差的影响。只要知道某阶重频的特征值和它的特征向量，用该方法便可准确地计算出其特征值和特征向量的一阶与二阶摄动。算例对弹性支承梁的复数重频振动特征问题进行摄动分析，摄动计算结果和精确计算结果吻合良好。     

一维随机参数结构的特征值问题

基于摄动传递矩阵的理论，给出一维随机参数结构系统特征值和特征向量的计算分析方法。用一个具有随机质量密度和截面直径的简支梁的理论结果，验证文中方法的正确性。     

不确定声场分析的区间矩阵分解摄动有限元法

针对修正一阶区间摄动有限元法存在的一阶Taylor展开误差较大和求解摄动逆矩阵时计算效率不高的缺陷,提出区间矩阵分解摄动有限元法(Decomposed interval matrix perturbation finite element method, DIMPFEM)。该方法将系统动态刚度矩阵分解为若干系统子矩阵之和,每个系统子矩阵的摄动矩阵用摄动因子和常量矩阵的乘积表示,避免了摄动矩阵的Taylor展开误差;采用Epsilon算法求解摄动逆矩阵的修正Neumann级数,有效提高了计算效率。将DIMPFEM应用于具有区间参数的二维管道和二维商务车声腔模型的声压响应分析,分析结果表明,与修正一阶区间摄动有限元法比较,DIMPFEM获得了更高的计算精度和计算效率。     

基于矩阵摄动的随机结构动态载荷识别技术

基于矩阵摄动和正则化方法提出一种随机结构动态载荷识别的分析方法。在时域内将动态载荷表示为时间和随机参量的函数,并以结构动力响应的卷积分关系式建立随机结构动态载荷识别的正问题。在离散化卷积分的基础上,利用基于泰勒展开的矩阵一阶摄动方法将随机结构的载荷识别问题转化为两类确定性反求问题,即结构随机参量取均值时动态载荷的反求和动态载荷关于各随机参量灵敏度的反求。当测量响应中带有噪声时,利用改进的正则化及L曲线方法克服反求过程中的病态性问题,实现两类确定性问题的稳定近似反求和动态载荷统计特征的有效评估。数值算例表明,针对随机结构该方法能稳定有效地实现动态载荷的识别和评估。     

失谐叶盘系统受迫振动响应摄动法比较研究

基于质量-弹簧模型,研究了在不同系统参数下,经典摄动法、修正摄动法和自适应摄动法求解失谐叶盘系统受迫响应的应用特点。通过对3种摄动法计算结果的比较分析,确定了3种摄动法对不同失谐强度、耦合强度、粘性阻尼比等参数的适用条件和应用特点。因此,本文的结论对于应用不同摄动法在求解失谐叶盘系统受迫响应问题时具有指导意义。     

重频结构大修改动力重分析的矩阵摄动法

为拓展矩阵摄动法在结构重分析中的适用范围,提高重分析计算精度,针对重频结构参数大修改提出了重频结构动力重分析的矩阵摄动法。采用高次增量法将反映重频结构参数改变的质量矩阵和刚度矩阵的增量分别表示为小参数ε的一次与二次幂项之和,根据矩阵摄动理论推导得到重特征值的二阶摄动解及相应特征向量的一阶摄动解。数值算例表明,所提出方法极大提高了重频结构大修改下的动力重分析计算精度。     

液固混合介质隔振系统的主共振分析

研究一类具有分段线性—非线性非光滑特性液固混合介质隔振器的主共振解析解。采用摄动法求解非线性段的瞬态响应,由常微分方程理论给出了线性段的瞬态响应。根据响应的连续性与周期性条件,联合接缝法与摄动法分析周期激励作用下系统的主共振响应。而后基于弹性恢复力的傅里叶展开,给出谐波平衡法求解非光滑隔振系统响应的一般步骤,并得到了一阶和二阶近似解。采用龙格—库塔算法对解析方法的有效性进行验证,结果表明:接缝法和数值计算的结果较为吻合,而谐波平衡法的二阶近似比一阶近似解更为精确。     

受损悬臂梁的模态分析研究

基于Euler-Bernoulli梁的自由振动方程,利用一阶摄动方法,对受损悬臂梁进行了模态分析计算,并利用Pro/MECHANICA有限元结构分析软件对悬臂梁受损前后的模态进行分析,与摄动数值计算方法进行比较,验证摄动理论分析的正确性。通过具体算例,得出悬臂梁在受损前后前四阶固有频率,以及在各个固有频率下的位移、应力云图,从而验证了基于摄动法理论分析的正确性,为利用动力学特性对悬臂梁的损伤监控和检测提供了理论依据。     

基于摄动传递矩阵法的随机参数系统振动分析

随机参数对多刚柔体结构动态特性具有一定影响,含随机参数系统的振动特性分析是现代多刚柔体结构研制与动态性能设计的重要环节之一。基于多体系统传递矩阵法和摄动方法,推导了含随机参数系统零阶、一阶和二阶摄动总传递方程,建立了含随机参数的多体系统特征值问题的分析方法,实现了含随机参数柔性结构振动特性快速分析。分别应用文中方法与Monte Carlo方法对某含随机参数的柔性结构和平面振动多刚柔体系统特征值问题进行了分析,两种方法的计算结果吻合较好,证明了文中方法的有效性和高效性。     

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.     

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.