42CrMo钢淬火数值模拟及试验验证

在标准端淬法的基础上,研制了末端喷油淬火设备来测试42CrMo的淬透性,仍按照标准端淬法对试样端面进行喷油淬火,直至试样冷却。采用热处理数值模拟软件COSMAP,对42CrMo钢的末端喷油淬火过程进行了数值模拟计算,模拟过程中充分考虑了相变的影响及温度一组织一应力／应变三场耦合,得到淬火过程中不同时刻的温度场、组织场、应力场和硬度场。对计算的温度和硬度变化结果进行了试验验证,模拟结果同试验结果基本吻合。     

数值仿真在金属热加工相变中的应用

热处理能够改善材料的组织及性能分布,数值仿真能较好地指导和优化热处理工艺。构建了热加工相变的计算模型,阐述了热处理过程中温度、相变和应变间的关系和计算所需考虑因素。讨论了热处理计算过程中考虑了相变过程中的热传导方程、弹塑性本构方程、有扩散和无扩散的相体积分数方程及扩散模型。结合Deform软件,介绍了热处理中尺寸变形、淬火相变和晶粒长大演变在数值仿真方面的应用。     

基于热传导角的机械密封环温度分布计算方法

机械密封端面温度分布是影响机械密封性能的一个重要因素,端面温度近似解析计算能够很容易地分析温度对密封的影响。热量以热传导形式在动静环内部传递,在动静环与介质接触区域以对流传热形式进行传递,同时考虑明确定义的热传导角,热量在动静环上的分配,基于热传导理论,获得一种确定动静环内部温度分布的计算方法。对比分析解析计算结果与数值模拟结果,表明近似解析解与数值模拟计算结果的温度平均误差均随端面距离和半径的增加呈下降趋势。     

尼龙6选区激光烧结温度场的数值模拟

采用ANSYS软件对尼龙6粉末材料激光烧结过程温度场进行了三维数值模拟,计算模型中,考虑了材料热物性随温度变化的非线性特征,采用更接近实际的高斯热源模型,并利用APDL参数化设计语言实现热源的移动控制,用焓处理相变潜热的影响。模拟结果显示,烧结点的温度随着扫描线的增加,先逐渐升高后趋于稳定,烧结点最高温度滞后于光斑中心到达该位置时刻,烧结区域边界最高温度小于内部的最高温度。最后进行了试验验证,与试验结果较吻合。     

A6061铝合金脉冲MIG焊T型接头应力场有限元模拟

基于B样条拟合非线性曲面的优势建立B样条焊缝模型，根据脉冲熔化极惰性气体保护(MIG)焊接基-峰值电流热输入特点建立高斯面+锥形体组合热源模型，采用该模型模拟A6061铝合金脉冲MIG焊T型接头的温度场及应力场，并进行了试验验证。结果表明：模拟所得T型接头熔池的熔深和熔宽以及特征点峰值温度与试验结果间的相对误差不大于1.4%,验证了模型的准确性。在距焊缝中心约10 mm和30 mm处的纵向残余应力模拟结果与试验结果间的相对误差分别为28.0%和20.6%,其计算精度比采用简化焊缝及双椭球热源模型至少提高了15.7%。     

等离子体弧金属表面强化处理的数值模拟

给出了用有限元方法对金属材料等离子体弧金属表面强化处理过程数值模拟的数学模型。模型考虑了工件材料的热物理性质随温度的变化以及处理参数的影响。根据模型可以得出工件横截面的温度分布图像，可以预测强化处理的相变硬化层深度和硬化带形状，并可以据此优化强化处理的参数选择。通过与实验值的对比，验证了模型计算的合理性。     

正交接管焊接残余应力的三维有限元模拟

对正交接管焊接接头的温度场和应力场进行了数值模拟。选用三维实体单元,考虑材料物理性能随温度的变化和相变的影响,采用内部热生成和振幅曲线的加载方法模拟焊接热源的移动,运用单元生死技术模拟多道焊过程。获得了焊接温度场和应力场的动态变化过程,并对计算结果进行了分析。     

双列螺旋槽液膜密封相变特性分析

考虑由动压槽造成的端面压力变化所带来的影响,探讨双列螺旋槽液膜密封的相变特性。基于均质混合物理论建立液膜密封相变模型,使用有限体积法对控制方程进行离散,分析液膜相变对密封性能及端面压力分布的影响。结果表明:相变发生后黏度明显降低,导致外侧螺旋槽挤压效应与泵送能力减弱,在其与相变的耦合作用下,开启力先减小后增大,泄漏量先增大后减小,相比于全液膜时密封性能有所下降;内侧螺旋槽产生的高压抑制了相变,压力分布规律未发生变化,外侧螺旋槽内相变区域较大,压力变化趋势明显改变。     

柴油机齿轮斜孔工装设计

正我公司在加工L型1624柴油机过程中,发现该型号机体输出端齿轮安装面有1处5mm斜油孔非常难加工。该孔位于输出端齿轮安装孔内,孔轴线距端面型腔距离201.5mm,角度30°,如图1所示。图1加工该孔时,需要占用公司五轴机床约2h,且需要购买5mm、不干涉长约300mm的钻头,加工成本非常高,为减少五轴机床占机时间,降低加工成本,通过设计斜孔工装,极好地解决了这个问题。     

粗糙液膜机械密封液汽相变研究

以逆向重构的确定性粗糙表面机械密封模型为依据，建立机械密封微间隙三维粗糙液膜流动计算模型；联立黏温效应与流体物性参数，对比光滑模型和粗糙模型的流速、端面压力、温度和相态规律；研究粗糙模型在不同载荷和转速下对液膜密封汽化相变特性以及密封性能关键参数的影响。研究结果表明：粗糙模型受温度变化程度更大，从478 K增加到了493 K;相态分布均随温度的升高而增大，其中同一温度下，粗糙模型的汽相分布更多，且在493 K之后出口相变程度就达到了100%,最大相体积分数增加11.73%。从而推断出：随着压力升高，端面汽相占比逐渐降低，而转速增加促进了汽化的发生。     

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.