仪器化压入仪深度测量随动盘模态分析

建立了高精度仪器化压入仪深度测量随动盘的三维实体模型,并利用有限元分析软件ABAQUS计算了该模型的固有频率和振型.结果表明:深度测量随动盘第(1～6)阶的固有频率均处于低频范围(小于20Hz),这就要求高精度仪器化压入仪的驱动部件应选用具有平滑线性力/行程控制特性的音圈电机,将压入测试时的加/卸载过程控制在准静态状态.此外,高精度仪器化压入仪应配备具有较好低频振动隔离特性的隔振台.分析对高精度仪器化压入仪的设计和改进以及工作环境的选择有一定指导意义.     

材料弹性模量压入识别的“纯能量改进方法”

为最大程度地减少"尺寸效应"对弹性模量仪器化压入识别结果的影响,文中采用状态参数代替过程参数对材料弹性模量仪器化压入"纯能量法"进行改进,并通过量纲分析和有限元数值仿真建立了"纯能量改进方法"。     

高精度仪器化压入仪设计与应用

研制了一款试样参照型高精度仪器化压入仪。该仪器采用3个探头式电容位移传感器与深度测量随动盘相结合的压入深度测量方式,排除了试样小角度倾斜、机架变形以及试样支撑或夹持变形对压入深度测量的影响,从原理上保证了仪器化压入测试中最关键的基础数据即金刚石压头压入试样深度的测量准确性。压入仪的驱动装置与载荷传感器采用分离式设计方案,避免了载荷测量的热漂移问题,保证了载荷基础数据的测试精度。仪器采用自主研发的系列材料力学性能测试新原理和新方法,解决了目前国际上商用仪器化压入仪采用传统测试原理及方法所带来的力学性能参数测试精度不高的问题。利用所设计的"高精度仪器化压入仪",对6061铝合金和S45C碳钢2种材料进行了杨氏模量的仪器化压入测试,验证了所设计仪器的测试精度。     

仪器化压入仪机架受力变形及模态的有限元分析

利用ABAQUS分析软件,对高精度仪器化压入仪机架受力变形情况及模态进行了有限元分析。得到了机架受力时倾斜角度的变化规律以及机架的固有频率和振型。分析结果表明:机架倾斜造成的载荷测量值与真实压入载荷之间的百分比误差处于10-8量级,机架倾斜对压入载荷的测试精度基本不构成影响。机架前六阶的固有频率均处于低频范围,因此,测试时高精度仪器化压入仪的加/卸载过程应控制在准静态状态,且高精度仪器化压入仪应配备具有较好低频振动隔离特性的隔振台。研究为高精度仪器化压入仪机架的设计和改进提供了依据。     

弹性模量仪器化压入测试方法比较分析

文中以弹性模量仪器化压入测试方法的力学模型、传感器性能指标对测试结果的影响、数据处理方法对测试结果的影响为切入点,对三种仪器化压入测试方法进行分析比较.纯能量方法建立的力学模型准确地解释了仪器化压入过程,对测试传感器性能参数和数据处理方法的敏感程度较低,具有一定的鲁棒性.     

纳米压入法MEMS材料力学能测量与评定标准化的初步设想

根据纳米压入法测量与评定MEMS材料力学性能的原理,对诸如测量仪器、压头、评定模型、测试条件等影响力学性能测量精确度、测量结果的可比性的主要原因因素进行了分析。在此基础上,提出对MEMS材料力学性能测量与评定进行标准化的初步设想。     

AAS法测定纯铪中痕量元素钠

研究了用AAS法测定纯铪中痕量元素钠。优化了原子吸收光谱测量条件,研究了酸及其用量,基体铪对测定钠的影响,编制了分析方法。测量钠的相对标准偏差不大于5.18%,测定范围为0.001%~0.005%,方法检出限为0.0041μg/mL。结果表明,本法不仅准确可靠而且简便快速。     

家用燃气灶热工性能测量及不确定度评定

依据GB30720—2014《家用燃气灶具能效限定值及能效等级》中热负荷和热效率的测量方法和步骤,对三个燃气灶的测量结果的不确定度进行GUM法(测量不确定度指南)和MCM法(蒙特卡洛法)两种方法的评定,结果显示用两种方法评定的结果一致。将三个燃气灶评定结果的平均值作为最终评定值,热负荷的相对扩展不确定度为0.76%,热效率为0.74%。此外试验时间的测量不确定度对热负荷测量结果不确定度的影响最大;当量加水量的测量不确定度对热效率测量结果不确定度的影响最大。     

反应堆辐照后铪同位素质谱分析研究

铪常用作反应堆控制棒材料,在反应堆辐照下产生半衰期较短(42.39d)的181Hf和半衰期很长(9×106a)的182Hf.曾有报道采用热电离质谱(TIMS)对天然铪同位素[1,2]和利用加速器质谱(AMS)对182Hf同位素进行测量[3],但未见用热电离质谱测量181Hf与182Hf的报导.因此,用TIMS测量反应堆辐照后铪同位素的变化,对反应堆物理研究有重要意义.但铪的电离电位很高,用TIMS测量有一定难度.本工作拟研究铪的质谱测量条件,包括消除同量异位素182W对测量干扰的方法.     

仪器化压入刚性压头有限元模型适用性问题分析

文中利用有限元软件ABAQUS分别对基于刚性压头和弹性压头的仪器化压入模型进行了建立与计算,并将刚性压头的模型仿真所得的压入比功We/Wt及仪器化压入Oliver-Pharr硬度HO-P与理想弹性压头的模型仿真结果进行对照。结果表明,刚性压头模型仿真识别压入比功We/Wt的相对误差变化范围为-2.6%~-31.8%,Oliver-Pharr硬度HO-P的相对误差变化范围为-0.3%~26.5%,其中对低强度材料进行仿真的结果与弹性压头模型相近,误差一般不超过5%,而随着材料强度的升高,其仿真误差显著增大,对于超高强度的材料的仿真计算压头弹性不可忽略,刚性压头模型应谨慎选用。     

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.