复杂陡峭曲面分段式螺旋刀路的设计

针对现有螺旋刀轨在实际应用中限制较多、无法直接应用于复杂陡峭曲面加工的局限,提出一种分段式螺旋刀轨。通过对流线驱动刀轨、曲面驱动刀轨和螺旋复合曲线驱动刀轨的有机整合,对复杂陡峭曲面的不同部位采用不同的加工方式,工艺针对性更强。同时,对作为流线的边界曲线采用提取、光顺和替换的方式进行重构,使得流线驱动螺旋刀轨更加光顺。实际加工和VERICUT软件仿真的结果表明,分段式螺旋刀轨能够满足高速加工刀轨连续光顺的要求,在生产中可操作性强。     

面向高速加工的复合曲线螺旋轨迹生成方法

针对现有螺旋切削方式仅仅适合圆形或类圆形边界曲面的问题,提出了一种复合曲线螺旋切削法,利用直线圆弧构建规则形状的辅助边界以包容不规则的曲面原始边界,以辅助边界构建光顺网格曲面作为螺旋线的投影曲面,然后桥接投影曲线与平面螺旋线作为驱动曲线从而生成复合螺旋刀路,在避免边界尖角影响的同时保留了刀轨连续的优点,适用于各种具有不规则边界的平坦曲面。软件模拟和实际加工结果表明,复合曲线螺旋切削法有效解决了刀轨的连续性和矢量突变问题,特别适合复合曲面的高速加工。     

数控四轴旋转刀轨优化技术的研究

现有数控四轴加工编程适应性差,无法获得与曲面特征形状一致的分层连续刀轨,进刀和出刀轨迹过多,同时由于存在切削盲区,使得精加工余量很不均匀,这已经成为数控四轴加工中的瓶颈问题。本文提出了一种数控四轴旋转刀轨,通过提取曲面边界并展开为平面轮廓线;然后以平面轮廓线为边界获得相应的平面铣刀轨,平面铣刀轨可以通过相应的后处理输出为DAT数据文件,导入DAT数据文件生成平面样条曲线,最后将平面样条曲线缠绕于目标曲面上作为驱动曲线,从而生成连续光顺的分层刀轨。刀轨模拟和实际加工结果均表明,数控四轴旋转刀轨显著提高了四轴加工的效率和质量,在生产中实用性很强。     

基于NURBS直纹面拟合敏感点的空间凸轮侧铣刀轨算法优化

基于NURBS直纹面拟合敏感点的空间凸轮侧铣刀轨算法优化原理,提出了拟合误差敏感点的选择方法,根据NURBS曲面重构的原理,将曲面曲率最值点和拟合误差最大点定义为理论加工刀轨曲面误差敏感点。利用曲率敏感点,在理论非等径刀轨曲面规划离散网格,得到初始数据点。通过最小二乘优化方法重构NURBS刀轨直纹面,再根据误差敏感点定义的等参数曲线来调整刀轨直纹面形状。构建了理论加工误差模型,并通过实例的仿真计算和数值模拟说明了该算法的有效性。     

中点误差控制刀位算法的改进

中点误差控制刀位算法通过引入抬刀量的概念,将刀具抬离曲面极小的距离,然后调整前倾角与侧偏角以提高刀具与曲面的贴合程度来获得较大加工行宽。文中提出一种将刀触点处侧偏角进行预处理的方法,以避免因一行刀轨内侧偏角不光顺带来的刀轨波动问题。首先对曲面进行分析并选取采样点,然后对采样点处进行刀位优化算得最优侧偏角,以采样点处侧偏角值构造侧偏角二维渐变模型,通过该模型可以计算曲面上任意刀触点处的侧偏角,再通过优化抬刀量和前倾角实现刀触点处行宽最大化。以某航空发动机叶片叶身曲面为例进行了刀位优化。实验结果表明,该方法生成加工刀轨较光顺,证实了该算法的有效性。     

面向高速加工的复杂曲面螺旋刀路优化

针对现有螺旋切削轨迹对曲面形状适应性较差,无法直接应用于复杂曲面的局限,提出一种基于曲面重构的螺旋曲线切削法。对于复杂曲面根据各自的特点分别采用曲面提取、修补、延伸等方法重构目标曲面,以重构后的曲面作为圆柱螺旋线的投影对象获取驱动曲线,在CAM软件中以曲线驱动方式生成螺旋曲线轨迹并进行优化。VERICUT软件仿真和实际加工的结果表明:复杂曲面采用曲面重构螺旋切削法可以获得满足高速加工要求的光顺切削路径,扩展了先进螺旋切削方式的应用范围。     

复杂曲面五轴数控加工关键技术研究

曲面驱动是复杂曲面加工中的一种高效刀轨规划方法。以典型的复杂曲面零件——"佛像"为载体,介绍了曲面驱动方法下的刀轨规划的原理,以及驱动面的设计思路和制作流程;同时对编程中的关键技术以及试制过程中的工艺工装进行了总结。该零件主要由多个复杂不规则曲面组成,采用"曲面驱动"进行刀轨规划,能获得与曲面近似的走刀轨迹和光顺的刀轴矢量。经试制,采用该刀轨规划策略和工艺方案,有效地提高了零件的表面质量,达到了设计和精度要求。     

上冠流道面开槽的数控加工研究

介绍水轮机转轮模型上冠流道面配合槽的数控加工方法,指出上冠流道面配合槽的作用、加工难点和解决方法。使用三维区域清除的加工策略实现高速、安全的开粗加工,克服了粗加工中的碰撞和磨损刀具的现象,大幅提高了加工的效率。通过SWARF精加工策略,用驱动曲线控制产生高效、光顺、均匀的刀具路线轨迹,减少空走刀的数量,达到非常优化的加工;通过三维偏置精加工完成曲面的槽底,在实际加工中效果良好。     

整体叶轮叶片根部特征刀具轨迹规化研究

针对整体叶轮叶片根部特征加工过程中极易产生过切和欠切的问题,提出了适合光滑过渡曲面区域的叶轮叶片根部特征的精加工的刀具轨迹规划优化方法。该方法首先对叶根曲面进行划分,定义加工曲面类型;然后对加工曲面进行刀具轨迹规划,计算出最佳走刀步长和行距;最后在保证刀具不与被加工表面发生过切和欠切的基础上,使得刀具与被加工曲面在刀触点处平面上每个方向的曲率相匹配,并使生成的刀轨光顺简洁,改善曲面加工精度与加工效率。通过对某叶片根部的仿真实例加工验证了该方法的正确性。该方法在多轴数控加工中具有重要的实用价值。     

叶片曲面的光顺拟合

为解决叶片曲面不光顺性造成刀轨计算失败的问题,根据叶片的实际设计、生产和检测经验,光顺拟合了叶片曲面,可以满足叶片曲面特殊的边界约束条件.以某航空发动机叶片为实例,光顺后的叶片曲面满足设计与加工工艺要求,验证了该方法的有效性.     

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.