轴类零件纵-扭复合振动超声深滚加工运动学研究

基于纵-扭复合振动超声深滚加工原理,构建了轴件纵-扭复合振动超声深滚加工运动学模型,分别给出了普通深滚和纵-扭复合振动超声深滚加工中工具头的运动方程;研究了振动参数和滚压工艺参数对工具头运动轨迹的影响及对系统设计和加工质量的影响。研究成果可为纵-扭复合振动超声深滚加工系统设计和加工工艺参数的优化选择提供理论依据。     

纵-扭复合振动超声深滚加工表面形貌研究

将纵-扭复合超声振动引入到传统深滚加工中,创建纵-扭复合振动超声深滚加工工艺,阐述其加工原理;分析其滚压过程;建立其表面形成模型并理论分析表面形貌形成机理;试验对比研究两种滚压方式下工件表面的微观形貌。试验结果表明:在相同的工艺参数下,辅助纵-扭复合振动后,工件的表面微观形貌优于传统深滚加工所获得,试验结果与理论分析结果相吻合。     

纵-扭复合振动超声深滚加工工艺试验

采用正交试验法对Q235钢端面进行了纵-扭复合振动超声深滚加工,探索了工艺参数对表面粗糙度和显微硬度的影响,并基于试验结果构建了表面粗糙度和显微硬度的预测模型。试验结果表明：经纵-扭复合振动超声深滚加工后,工件表面粗糙度值显著减小,而显微硬度有大幅提高;表面粗糙度值随静压力增大先增后减,随进给量的增大而急剧增大,而随滚压速度的增大变化不明显,且进给量对表面粗糙度的影响最显著;显微硬度随静压力的增大而提高,随进给量和滚压速度的增大有微小波动,且静压力对显微硬度的影响最显著;基于t-检验与相关系数计算结果发现,进给量与静压力的交互作用对表面粗糙度的影响最大,而静压力与滚压速度的交互作用对显微硬度的影响最大。基于正交试验结果和预测模型获得了最优工艺参数,两者的结果接近,表明预测模型可靠。     

工程陶瓷纵扭复合超声振动螺旋磨削 制孔表面质量研究

针对工程陶瓷传统磨削制孔存在表面质量较差等问题,对超声振动辅助加工及螺旋加工的工艺优势进行了归纳分析,提出了纵扭复合超声振动螺旋磨削制孔的加工方法。利用超声加工机床和白光干涉仪及马尔表面轮廓仪,对纵扭复合超声加工、纵向超声加工和普通磨削加工对孔表面质量的影响情况进行了研究;并进一步探究了施加纵扭复合超声振动后超声振幅、螺距、主轴转速、螺旋进给速度对加工孔表面质量的影响规律。研究结果表明:相比纵向超声加工和普通加工,纵扭复合超声加工有利于提高制孔表面质量;纵扭超声螺旋磨削加工超声振幅、螺距对孔底和孔壁表面粗糙度的影响趋势相似,主轴转速及螺旋进给速度对两者表面粗糙度的影响趋势总体上相反。     

超声纵扭辅助铣削高强铝合金表面润湿性能研究

针对超声辅助加工在工件表面形成微刻划表面可以提高高强铝合金表面的微结构性能的现象,进行了单激励旋转超声纵扭复合铣削表面微观结构的试验,基于水接触角理论和纵扭铣削运动学理论分析了加工参数对水接触角的影响;搭建了单激励超声纵扭铣削试验平台,采用正交试验法研究了不同加工参数对表面粗糙度、铣削力以及表面润湿性能的影响。结果表明：超声振幅为4μm时表面质量最佳,切削速度和进给量与表面粗糙度和水接触角呈正相关的关系;超声加工方式下的表面水接触角较普通方式更大,而在超声加工时低振幅加工比高振幅加工的表面水接触角大,当转速达到一定值时,高振幅和低振幅所加工的表面水接触角差别不大。合适的加工参数条件下超声纵扭加工方式可以降低加工表面的粗糙度,改变表面的润湿性。     

非均匀介质超声铣削系统振动特性研究

采用纵扭复合超声振动铣削进行加工时,由于加工中心等空间受限场合对超声振动系统的尺寸限制,利用四分之一波长理论设计集换能器和复合变幅杆为一体的非均匀介质超声振动变幅系统,在变幅杆部分设计螺旋槽结构实现纵扭共振,并研究纵扭模态转换理论。对非均匀介质变幅系统进行有限元分析,仿真结果表明纵振系统固有频率理论值与仿真值接近,偏差仅为0.245%;对螺旋槽结构进行仿真发现槽深对其对超声变幅系统固有频率、扭纵幅值比例影响较大,螺旋角的影响次之,槽宽影响最小,振动系统测试实验表明固有频率和扭纵幅值比的仿真结果与实验结果变化趋势一致。分别对TC4钛合金和C/C碳纤维进行纵扭超声振动铣削和传统铣削实验对比,结果显示相对于传统铣削,在纵扭超声振动铣削加工中两组材料表面粗糙度值Ra分别下降78%和47%。纵扭复合非均匀介质超声振动铣削系统结构简单紧凑、振动幅值和方向可控性较好,采用纵扭超声振动铣削能有效提高工件表面加工质量。     

纵-扭复合振动超声深滚加工残余应力场数值分析

为研究平面试件在纵-扭复合振动超声深滚加工后材料应力分布及变化规律,采用有限元方法对Q345钢进行了纵-扭复合振动超声深滚加工残余应力场数值模拟。首先分析了加工后试件材料各应力分量沿深度方向的分布情况,然后研究了静压力、滚压速度、振幅和相位差对加工后材料残余应力的影响规律。结果表明:经纵-扭复合振动超声深滚加工后材料表层残余应力分布较均匀,表面为压应力,压应力沿试件深度方向先增后减;试件最大残余压应力及最大横向残余压应力深度和残余压应力层深度随静压力的增大而增大,随滚压速度的增大而减小,而表面残余压应力和最大纵向残余压应力深度无显著变化;试件横向残余压应力层深度随振幅的增加小幅度地增大,但最大残余压应力幅值和深度和纵向残余压应力层深度几无变化;相位差对残余应力影响可忽略不计。     

电弧微铸锻增材制造AlMgSc合金纵扭复合超声振动干铣削加工特性研究

对电弧微铸锻增材制造AlMgSc合金进行纵扭超声复合干铣削加工特性试验研究,探讨超声铣削工艺参数对切削力、表面形貌、加工硬化及刀具磨损等AlMgSc合金干铣削成形特性的影响规律。结果表明：与锻造和常规电弧增材成形铝合金相比,微铸锻增材制造AlMgSc合金由于具备更加致密的微观组织、更高的强度和硬度而在超声干铣削成形过程中会产生更大的铣削力,更容易发生加工硬化。与常规干铣削相比,采用纵扭复合超声干铣削可以获得更小的表面粗糙度,并有利于减轻刀具磨损。     

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。     

螺旋沟槽参数对纵-扭变幅杆振动分量的影响

为更好地探究纵-扭复合超声振动加工技术在硬脆材料加工中的优势,提出一种新型扭转振动测评方法,设计纵-扭复合超声变幅杆。首先,理论推导了螺旋沟槽结构的纵-扭模态转换,揭示了纵、扭振动分量对变幅杆振动轨迹的影响;然后,在有限元分析中定义了扭纵分量比j,并分析了螺旋沟槽数目n、螺旋角度θ和槽宽d等参数对扭纵分量比j的影响规律。结果表明:扭纵分量比j随螺旋沟槽数目n及槽宽d的增加而变大,随螺旋角度θ的增加而先变大后减小,并利用正交参数的极差分析法得到各参数对其影响力度大小的主次。通过实验验证了有限元分析结果。     

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.