切削-挤压翅片管成形过程的研究

采用无屑切削-挤压成形技术加工翅片管。对翅片的成形过程和加工刀具的特点进行了研究,建立了翅片尺寸的理论模型;通过单因素试验,获得了主偏角、切削深度、进给量、切削速度等工艺参数对翅片尺寸的影响规律;以正交试验为基础,获得了翅片高度和厚度的经验公式。理论和试验研究表明,切削用量参数和刀具几何参数的精确匹配是翅片成形的关键。     

板式翅片滚压成形过程仿真

采用一种新型滚压工艺进行板式翅片加工,简述了板式翅片的成形原理及滚压刀具的设计原则;利用DEFORM-3D软件对其成形过程进行模拟仿真,获得了理想的模拟翅片结构;分析了成形过程中工件的应力应变状态和滚压刀具在成形中的受力状况,通过加工实验验证了该方法的可行性。     

板式翅片滚压成形过程仿真

采用一种新型滚压工艺进行板式翅片加工,简述了板式翅片的成形原理及滚压刀具的设计原则;利用DEFORM-3D软件对其成形过程进行模拟仿真,获得了理想的模拟翅片结构;分析了成形过程中工件的应力应变状态和滚压刀具在成形中的受力状况,通过加工实验验证了该方法的可行性。
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波纹形翅片成形过程的有限元模拟与分析

为了提高波纹形翅片成形刀具的设计成功率与效率,通过显式动力学软件ANSYS/LS-DYNA对翅片的成形过程进行了有限元模拟,仿真结果与实际加工结果吻合。分析了刀具的参数、装配误差及刀具与铝片间的摩擦因数对翅片成形尺寸的影响规律。发现刀具的重合度不宜过大,否则会导致翅片的成形尺寸误差过大和翅片的外形发生畸形。刀具的中心距装配误差除了影响成形翅片的长度尺寸外,还会影响翅片顶弧长度与斜边长度的比例。刀具与铝片间的摩擦因数大小同样影响翅片成形尺寸。     

工艺参数对外翅片管成形过程影响的研究

采用无屑滚压—犁切复合成形工艺加工三维外翅片管。对翅片的成形过程和加工的特点进行了研究,并建立了翅片尺寸的预测模型;通过切削实验,获得了进给量、主偏角、切削深度等工艺参数对翅片高度和间距的影响规律。经理论预测和实验研究,对切削用量参数和刀具几何参数的合理选择进行了分析。     

钛合金蜂窝瓦楞板的成形工艺

以两个成形齿轮作为辊压模具,用与瓦楞板外轮廓参数完全相同的齿形模具作为校形模,采用辊压/校形复合工艺制备了钛合金蜂窝瓦楞板;运用Ansys/Ls-Dyna软件对瓦楞板的成形过程进行有限元模拟,探讨了上下成形齿轮间隙与成形质量的关系,得到了优化工艺,并用试验对成形工艺进行了验证。结果表明:用辊压/校形复合工艺制备高精度钛合金瓦楞板是可行的,瓦楞板尺寸的最大误差仅为1.8%;辊压成形时齿轮的最大间隙值是影响瓦楞板成形精度的关键参数之一,当最大间隙值为0.2mm、校形压力为3 000 MPa、校形时间为30s时,瓦楞板的成形质量最好;采用可调式箱体来控制成形齿轮的平行度及最大间隙值,可有效降低对辊压装置的加工及装配精度要求。     

板式翅片滚压成型的数值模拟

针对板式翅片加工现状,提出一种板式翅片滚压成型新方法。阐述了该方法的成形原理;在三维软件中建立了滚压刀具和工件的有限元分析模型,采用Deform-3D有限元分析软件对板式翅片滚压成型过程进行了数值仿真,获得了理想的翅片形状;分析了成形过程中工件的应力状态及滚压刀具的受力情况,为板式翅片滚压成型方法的研究和应用提供了重要理论依据。     

三维强化外翅片换热管加工机构设计

为了改善当前外翅片换热管加工设备效率不高、成形翅片强度不足和自动化程度不足等问题,对三维强化外翅片换热管的加工机构设计进行了研究。设计了一种装有刨刀阵列的翅片管加工机构,并对该机构进行了结构分析,阐述主要零件之间的相对运动及约束情况。根据预期翅片的形状,给出了刨刀刀尖的预期轨迹,对加工机构动作的临界状态进行了力学分析,给出了加工机构的相关参数的取值依据。最后通过研制加工机构样机进行换热管翅片加工,验证了设计的可行性。     

双面犁法加工整体翅片管的成形数学模型

建立了双面犁法加工整体翅片管的成形数学模型 ,推导了翅片结构参数与加工用量及刀具几何参数之间的关系 ,为优选翅片结构参数以达到最佳传热效果提供了理论依据。理论分析和试验结果均表明 ,对于某一刀具 ,翅片高度和平均翅厚均随挤压深度和进给量的增加而增大     

双面梨法加工整体翅片管的成形数学模型

建立了双面犁法加工整体翅片管的成形数学模型，推导了翅片结构参数与加工用量及刀具几何参数之间的关系，为优选翅片结构参数以达到最佳传热效果提供了理论依据。理论分析和试验结果均表明，对于某一刀具，翅片高度和平均翅厚均随挤压浓度和进给量的增加而增大。     

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.