轧机压下系统螺纹副面力场的有限元分析

为了改善型钢轧机压下系统中螺纹副的应力分布,提出在螺母上下表面车制环形槽的方法,并结合大型有限元软件Marc强大的非线性功能,建立了螺纹副改造前后的有限元模型.计算结果表明:螺母改造后螺纹副内的应力场分布更趋向于均匀,且降低了应力峰值,提高了压下系统的承载能力.研究成果对提高螺纹副的承载能力和材料的利用率有一定的指导意义.     

轧机压下螺纹副回松机理试验和铜螺母螺牙塑扁鼓包分析

为定量解明中厚板轧机压下螺纹副回松机理和铜螺母螺牙顶端塑性压缩变形鼓包现象,制作中厚板轧机螺纹副1/8实物模型,进行螺纹副压下螺钉回松量测试、振动试验和铜螺母螺牙塑性压扁及顶端鼓包的有限元数值分析.轧机压下螺纹副采用大间隙中径定位力学约束.在轧制及间歇振动及咬、甩钢载荷工况下,由于螺纹副力学约束定位而侧隙控制的不可靠性,每当发生压下螺钉与平衡机构之间的不同步运动场合,诱发压下螺钉回松或螺牙顶端产生塑性压扁鼓包现象.提出主/副复合螺母结构,副螺母靠螺牙背面对压下螺钉实现几何约束以取代中径定位力学约束,有效地防止螺纹副动态侧隙的发生而分离,实现压下螺钉自平衡,减小压下螺钉的回松量,防止铜螺母螺牙产生塑扁鼓包.同时,减缓铜螺母的磨损,成倍增加螺纹副工作寿命.     

基于热-结构耦合的轧机压下螺纹副强度分析

基于Ansys有限元软件建立了轧机压下螺纹副的三维模型,计算了常温下压下螺纹副结构的承载特性,通过提取出每扣螺牙等效应力的最大值,验证了轧机压下螺纹副螺牙根部的等效应力分布呈U形的规律。利用间接耦合法分别计算了60℃、100℃温度下热-结构耦合的螺纹副承载特性,对比了不同温度下压下螺纹副螺牙根部的等效应力及螺牙面的接触压力。结果表明,接触压力及等效应力的最大值均发生在第1扣螺牙;当温度为100℃时,压下螺母等效应力的最大值接近于螺母材料的屈服极限。     

基于有限元方法的传动螺纹螺牙轴向载荷分布规律分析

采用有限元方法,通过改变螺旋副的受力方式、螺母结构、螺杆螺母弹性模量比及螺纹设计参数建模不同的螺旋副,求得不同模型下螺牙轴向载荷对螺旋副总轴向载荷的百分比.在大量模型分析及对计算结果后处理工作的基础上,总结了螺母结构及螺纹设计参数对传动螺纹螺牙轴向载荷分布的影响规律,为螺旋副的结构优化和摩擦学优化设计提供依据.     

有限元接形状优化触分配和形状化在提高受压螺纹载荷分配均匀性上的应用

通过对轧钢机压下螺纹副的弹性接触有限元分析计算,得出了载荷沿轴向在各螺牙上的分配。在此基础上为既降低最大螺牙载荷又提高螺牙载荷分配的均匀性,运用有限元形状优化中的变刚度法对螺母结构进行了优化设计。     

轧机压下螺纹副承载特性测试研究

依据相似准则，制作3500mm中厚板轧机电动压下传动螺纹副1／3的测试模型，采用电测法获取悬臂螺牙弯曲应变值，模拟实际轧制力和过平衡力作用下螺纹副螺牙各层载荷大小及分布。螺纹副测试结果和边界元、有限元法数值计算结果相比，螺牙层载荷大小和分布规律基本吻合，证明电测法可行、直观且可靠。通过测定数据，证实了轻重两种载荷工况的不同承载特性，还发现螺母与丝杆轴线错移或倾斜的微尺度行为对载荷大小及分布影响极大的重要现象，为提高压下传动螺纹副寿命及可靠性提供了重要思路。     

螺母刚度对压下丝杆副中载荷分布的影响

本文从实际受载情况出发，对轧钢机压丝杆和螺母体刚度对螺纹副载荷分布系数的位置将随丝杆和螺母体刚度之间的比值而变；和一般受拉螺纹副不同，螺母体刚度过大非但不能改善载荷分布，反而会加剧载荷分布的不均匀性。当螺母体刚度和螺杆体刚度基本一致时，螺纹副中的最大载荷分布系数将达到最小值。所以在压下丝杆副设计中应注意等刚度设计的应用。     

螺纹载荷分布计算方法研究及有限元分析

针对国内现有的螺纹设计没有系统的理论,提出了螺纹展开法的理论分析方法。介绍了现有的螺纹载荷分布研究方法,采用螺纹展开法进行了分析,推导出了沿螺纹啮合线方向的载荷比例公式,分别讨论了螺栓参数对螺纹承载比例的影响。通过ANSYS Workbench静力学模块,对螺栓拧紧时螺纹副应力分布情况进行了有限元分析,通过SOPWITH和YAMAMOTO两种分析法,验证了螺母轴向力之比分布;将螺纹牙承载比例分布分析结果与螺纹展开理论分析法结果进行了验证对比,并用螺母变形量试验验证了螺母展开法的可靠性;通过三维有限元分析法,系统地考察了螺纹牙弹性模量比E_s/E_b、螺距P、螺纹副摩擦系数μ、内外螺纹牙型对螺母载荷分布的影响规律。研究结果表明:螺栓参数E_s/E_b、P/D、牙型是影响承载分布的主要参数,选用外螺纹应选用弹性模量较大的材料;内螺纹应选用弹性模量较小的材料,可减小螺纹载荷分布不均的问题。     

不同工作温度下行星滚柱丝杠副载荷分布研究

为揭示不同工作温度下行星滚柱丝杠副载荷分布规律,考虑不同安装方式对载荷分布的影响,基于有限元方法建立了行星滚柱丝杠副有限元分析模型。通过在工作载荷作用下有限元解和理论结果对比,验证了模型的正确性。在此基础上,综合考虑行星滚柱丝杠副不同安装方式和受力状态,系统分析了不同工作温度下行星滚柱丝杠副载荷分布规律。结果表明,温度对丝杠侧载荷分布的影响程度大于螺母侧,对受拉侧影响大于受压侧;温度改变丝杠和螺母在轴向的累积变形是影响载荷分布规律的重要因素。考虑温升及两侧载荷分布的相互作用,在丝杠和螺母同时承受压应力时,两侧载荷分布均匀程度最优。     

螺纹副承载的分布规律

介绍螺纹副载荷分布特点以及螺纹副承载分布的解析方法、光弹试验方法和有限元法。基于ANSYS平台建立参数化的螺纹副承载分布有限元模型,通过SOPWITH和YAMATOTO两种解析方法验证螺母轴力计算结果,将各扣螺纹牙承载比例与光弹冻结试验结果进行对比,以验证有限元模型的可靠性。接着系统考察螺纹类型、螺距P、螺纹副径向尺寸系数d/D、啮合扣数N、摩擦因数μ和螺纹副材料弹性模量比Eb/En等因素对螺纹副承载分布的影响,并对主要影响因素进行回归分析。     

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.