机械式轴向深孔振动钻削系统的设计

深孔的钻削加工过程中,经常生成带状切屑,堵塞在孔内,对加工质量产生影响,特别是经常发生卡钻或断钻事故。如在钻削过程中,对切屑进行周期性断屑,并与负压抽屑装置配合使用,解决了深孔加工过程中断屑排屑困难的问题。设计一种机械式深孔振动钻削装置,对深孔进行振动钻削,可通过改变电机的转速调整其钻削频率,改变滑块的位置可调整振幅,显著特点是结构简单,振幅与频率调整方便,提高深孔的加工质量。     

电磁式深孔振动钻削装置的设计

深孔钻削中,经常会有连续的带状切屑导致断钻事故。设计一种电磁式深孔振动钻削装置,通过改变交流电的频率调整其钻杆频率与振幅,并与负压抽屑装置配合使用,可解决了深孔加工过程中断屑排屑困难的问题,并提高深孔的加工质量。     

超声轴向振动钻削断屑机理分析与试验研究

基于振动钻削原理对振动断屑机理进行了研究,建立了振动钻削数学模型,并分析了轴向动态切削厚度变化规律及保证断屑时所需的振幅条件。在设计的超声轴向振动钻削试验装置上进行了深小孔超声振动钻削与普通钻削的对比试验。试验结果表明与普通钻削相比,振动钻削加工得到的孔具有较小的扩孔量和较好的断屑、排屑效果。     

深孔加工轴向振动装置设计

深孔加工在孔加工中占有较大的比重,深孔加工技术的难点之一是连续自动排屑。本文基于振动钻削机理,结合现有轴向振动钻削装置,在此基础上进行改进,设计了一套轴向振动装置。装置中使用压电陶瓷致动器有效地避免了机械传动所产生振动的不稳定性。基于Deform-3D软件对轴向振动钻削进行切屑模拟实验,并通过实验验证了轴向振动钻削较普通钻削而言在断屑方面及孔表面质量方面所具有的优势。     

小直径内排屑深孔振动钻削试验与分析

目前,国内外采用振动钻削来加工小直径深孔,但都存在着两类问题：一是振动钻削系统中,多数振动装置的振幅是不可调节的,或凋幅十分困难和麻烦;二是小直径深孔钻头的设计与制造,大部分是采用外排屑枪钻,很少采用内排屑深孔钻。由于小直径枪钻制造工艺上的困难,国内主要采用进口枪钻,价格昂贵,设备要求较高,很难在生产中推广使用。对此我们设计了振幅连续可调、操作简便的振动装置和制造工艺简单的小直径排屑深孔钻,并进行了φ8×300mm和φ6×50Omm的小直径深孔加工工艺试验,试验效果良好。一、振动钻削系统与内排屑深孔钻振动…     

孔加工振动切削的断屑机理

分析孔加工中常用的麻花钻、扩孔钻、深孔单刃钻等振动切削的断屑机理,得出各种钻头振动切削的最佳条件,包括振动发生器的最小振幅、振动频率和工件转速断屑的最佳比值及各种情况的断屑层图。     

钳工操作中深孔的钻削实践分析与改进

在金属切削加工过程中,钻削深孔一直是个难题,尤其是加工精度难以保证。深孔钻削的关键是解决断屑、排屑问题。从教学角度结合实践操作,针对钻削深孔加工存在的问题,设计了一种新型的内排屑深孔钻头。以钻头的结构和刃磨特点为切入点,结合生产实践进行了振动钻削实验,实现了断屑、排屑的流畅,达到了钻头应具备的良好性能。     

深孔加工振动断屑装置设计

针对深孔加工过程中切屑形态不稳定所形成的排屑不畅问题,基于振动钻削理论,设计振动断屑装置,有效控制切削形态,保证顺利排屑。通过给刀具施加轴向周期振动,振动断屑装置可实现变切厚钻削和钻头轴向振动,使切屑易断,并在一定程度上提高了表面加工质量。通过实验探究了切屑形态与切削参数的关系,分析了振动断屑装置的最佳工作参数。     

低频振动钻削CFRP/钛合金叠层材料试验研究

在叠层材料一体化制孔过程中,CFRP制孔质量极易受到钛合金切屑排出的影响,出现入口撕裂、孔径超差等加工缺陷。为了提高叠层材料的制孔质量,本文分析了振动钻削的运动学特征,确定了理论最小断屑振幅,通过低频振动钻削和传统钻削叠层材料的对比试验重点探讨了不同振幅参数对切削力、切削温度以及制孔质量的影响。结果表明:随着振幅增大,钻削平均轴向力小幅下降,最大轴向力呈现上升趋势;当振幅大于最小断屑振幅时,低频振动钻削在实现有效断屑排屑的同时能够显著降低切削温度,提高孔壁质量和孔径精度;CFRP入口撕裂受振幅的影响最为明显,加工振幅过大会导致入口撕裂的扩大;当振幅为30μm时,入口撕裂区域最小,孔壁粗糙度达到R_a2.16μm,叠层材料总体制孔质量最好,切削温度同时降低了20.8%。     

深孔振动钻削的断屑条件研究

本文通过建立深孔振动钻削的数学模型,在振动钻削相邻两转间的断屑条件的基础上推导出更为一般的断屑条件式,为振动钻削断屑过程的参数匹配提供了理论依据,并得到了振动钻削加工试验的证明。     

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.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.