大截面圆锥形超声变幅杆的设计及负载特性分析

通过瑞利近似理论假设,对大截面圆锥形变幅杆的纵向振动固有频率进行修正,得到了修正频率表达式,同时研究了负载对大截面圆锥变幅杆的放大系数和谐振频率的影响。利用有限元法对一组大截面的圆锥形变幅杆进行模态分析和负载特性研究,结果表明:修正后的结果与一维理论相比更接近有限元模拟值,其适用范围更大;随着负载直径和长度的增加系统频率将逐渐减小,而放大系数在不断增加,比较可得直径的影响较长度要更显著。研究结果对大截面的圆锥形超声变幅杆的工程计算和此类复合变幅杆的设计和实际应用提供理论依据。     

超声变幅杆的动态性能分析

根据变截面杆纵向振动的波动方程,推导悬链形超声变幅杆的频率方程,应用有限元法对变幅杆进行模态分析,得到共振频率、横向振动频率、位移节点、放大系数等重要参数。与理论计算值比较表明,有限元法可获得很高精度。     

超声变幅杆的模态分析

根据变截面杆纵向振动的波动方程,推导了悬链形超声变幅杆的频率方程,应用有限元法对变幅杆进行了模态分析,得到了共振频率、横向振动频率、位移节点和放大系数等重要参数。与理论计算值的比较表明,有限元法获得了很高的精度。     

基于四端网络法的超声珩齿振动系统设计

从变截面杆作一维纵振动的运动方程出发,建立机械四端网络的数学模型及传输特性方程,导出了超声珩齿复合振动系统的频率方程和放大系数计算公式。将小端接圆柱杆的复合圆锥形变幅杆与被加工齿轮组成复合振动系统,将齿轮简化为圆柱杆,采用四端网络方法,得出了复合振动系统的频率方程与放大系数公式。     

圆锥形变幅杆节点的动力学分析及优化设计

变幅杆节点位置的选取直接影响着声学系统的传输效率,圆锥形复合变幅杆节点位置随着变幅杆的直径比N、长度l和外激频率f三个变量的变化而变化,固定其中任意两个变量,利用有限元软件MATLAB对第三个变量进行抽样计算得到节点样本值并将其拟合成图。应用有限元软件对其进行仿真,通过位移云图发现节点处径向截面外轮廓处位移并不为零。为了提高传输效率,降低节点位置选取所带来的振动,通过有限元软件MATLAB对节点进行优化设计。实验结果表明:以谐振频率20k Hz为例,优化后的振幅有所增大,传输效率进一步提高,谐振频率更加接近设计频率。     

超声辅助冲击强化装置及复合变幅杆优化设计

基于超声喷丸原理设计制作了利用伺服系统进行数控进给的旋转辅助超声冲击强化装置;利用波动方程和传统复合变幅杆设计理论,设计了圆锥复合变幅杆,用ANSYS软件对其进行了模态分析、谐响应分析和动力学分析。用该装置对镁合金试件表面进行冲击强化试验。结果表明,旋转辅助有利于提高试件表面冲击覆盖率;经ANSYS分析优化后的变幅杆结构合理,阻抗分析结果显示振动性能较好;在输入端直径相同的情况下,放大系数和最大应力值随着变幅杆过渡段长度的增大而不断减小。     

超声珩齿复合变幅器设计及其动力学研究

在超声珩齿加工中,由变幅杆和被加工齿轮组成的变幅器的设计是一项关键技术,探索新型变幅器显得非常重要。基于变截面复合变幅杆纵向振动波动方程和中厚圆环板弯曲振动位移方程,根据复合变幅杆与中厚圆环组成的超声珩齿复合变幅器的非谐振性和边界条件,推导了系统的谐振频率方程,利用数值计算对设计参数、谐振频率、变幅杆及圆环振幅分布等进行研究,同时分析了变幅器几何参数对系统谐振频率的影响。结果表明,有限元分析结果与理论计算结果和实验测试基本一致,系统谐振频率随复合变幅杆各段长度的增加而减小;当复合变幅杆大小端半径比和各段长度保持不变时,系统谐振频率随两端半径成比例地增加而增加;其他参数不变时随圆环厚径比地增加而增加,其结论不仅证实了非谐振理论的正确性,而且为超声珩齿变幅器的设计和应用提供了理论依据。     

超声振动的挤滚压光整加工变幅特性分析及应用

提出了一种针对机械加工中轴类零件外圆表面加工的新型超声振动挤滚压式加工方法。介绍了超声振动挤滚压式强化的加工原理及特点;分析了该工艺的加工特性与超声换能的聚能作用;进一步从金属表面微观塑性变形机理等方面进行探索;同时利用数学模型建立变截面杆纵向振动的波动方程,推导出圆锥型复合变幅杆频率方程和放大系数的计算公式;阐述了变幅杆的变幅特性及其设计参数间相互的关系,并通过实例验证变幅杆的尺寸设计参数。结果表明,该方法能提高零件表面加工质量。     

带中心孔的复合超声变幅杆设计及性能分析

带中心孔的变幅杆可以实现旋转超声加工的中心供冷却液或气体,具有良好的冷却和排屑效果。针对单一形状变幅杆难以实现大振幅的超声振动,对带中心孔的复合超声变幅杆的设计原理和方法进行研究。根据任意截面杆的波动方程,得到带中心孔单一形状变幅杆的传输方程和传输矩阵,并通过对总体四端网络的传输方程和传输矩阵的运算,推导出带中心孔的圆锥过渡复合变幅杆的频率方程和放大倍数的一般公式。根据推导出的频率方程,设计出典型的复合变幅杆,并对所设计的变幅杆进行频率测试,测得的变幅杆频率与理论计算频率的误差在5%以内。研究带中心孔的圆锥过渡复合变幅杆各段长度及中心孔直径对变幅杆频率的影响规律,为复合变幅杆设计和调整提供了理论依据。     

圆锥形复合变幅杆纵-扭复合振动的实现

为解决纵-扭复合振动超声加工中复合振动的实现难题,对单激励纵-扭复合振动圆锥形复合变幅杆展开研究。基于变截面杆一维纵向振动和扭转振动理论,推导出圆锥形复合变幅杆纵向振动和扭转振动的频率方程,并确定其振动特性参数。阐释了单激励下圆锥形复合变幅杆纵-扭复合振动的实现机理,并通过应用实例给予验证。理论计算、数值分析与测试结果表明,选择合适的几何结构参数,圆锥形复合变幅杆可以实现纵-扭复合振动。     

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.