电镀CBN锥砂轮磨削齿面残余应用的研究

从磨削表面生成过程出发,对电镀CBN锥砂轮磨齿表面残余应力进行了定性分析,并对其与陶瓷CBN锥砂轮在不同工艺参数组合下磨削后齿面残余应力状态做了对比试验。结果表明,电镀CBN锥砂轮磨削后齿面处于残余应力状态,且在相同金属去除率时电镀CBN锥砂轮比陶瓷CBN锥砂轮磨削后齿面的残余压应力值更大。     

电镀 CBN 锥砂轮磨削齿面残余应力的研究

从磨削表面生成过程出发,对电镀CBN锥砂轮磨齿表面残余应力进行了定性分析,并对其与陶瓷CBN锥砂轮在不同工艺参数组合下磨削后齿面残余应力状态做了对比试验。结果表明,电镀CBN锥砂轮磨削后齿面处于残余压应力状态,且在相同金属去除率时电镀CBN锥砂轮比陶瓷CBN锥砂轮磨削后齿面的残余压应力值更大。     

基于力热耦合作用的磨齿残余应力研究

根据磨齿残余应力的产生机理,运用热弹塑性理论,得出了影响螺旋锥齿轮磨齿残余应力的磨齿基本参数、磨削力和磨齿热等特征参量的数学模型。在单齿3D有限元模型基础上,磨削力的处理采用小步距移动法,力热耦合运用间接法,对螺旋锥齿轮进行了磨齿残余应力的有限元模拟与分析。结果表明：磨削后的螺旋锥齿轮齿面呈现残余压应力,里层为残余拉应力,其大小随磨削条件和磨削用量等因素的不同,呈现一定的变化规律;磨齿残余应力随磨削深度和砂轮速度的增大而增大,而随展成速度的增大而减小;湿磨比干磨可明显减小磨齿残余应力。最后,试验验证了力热耦合有限元分析螺旋锥齿轮磨齿残余应力的有效性,并与直齿圆柱齿轮的磨齿残余应力进行了试验对比分析。研究结果为螺旋锥齿轮磨齿质量的控制提供了依据。     

应用有限元法的磨齿过程热状态研究

磨齿加工不但在工件表面产生较高的温度,而且还会在工件表层内产生梯度很大的温度场,这是形成磨削残余应力以及造成磨齿工件表层金相组织变化的主要原因.因此,正确地确定工件表层内的温度场及表面温度,能够预测磨齿残余应力,了解表层金相组织变化,进而可合理运用磨齿工艺,进行表面质量控制.采用的有限元法为磨齿过程热状态分析提供了一种全新的研究方法.     

预应力淬硬磨削工件表面层质量试验研究

从抗疲劳制造与绿色制造的观念出发,融合预应力磨削与磨削淬硬技术原理,提出了将残余应力控制、表面淬火及磨削三者集成于一体的预应力淬硬磨削技术理论与方法。对45钢试件进行了预应力淬硬磨削加工试验,以工件淬硬层表面残余应力、硬度及粗糙度为研究对象,与相同条件下的磨削淬硬工艺试验结果进行了对比分析。结果表明：预应力淬硬磨削工艺可增大工件表面残余压应力,减小拉应力,其工件表面残余应力状态优于磨削淬硬工艺;预应力淬硬磨削工件表面硬度可以达到基体硬度的3倍左右,而工件表面粗糙度小于磨削淬硬工艺工件表面粗糙度。因此,在相同的加工条件下,预应力淬硬磨削工艺比磨削淬硬工艺具有更好的抗疲劳性、耐腐蚀性及表面完整性。     

磨齿表面烧伤与裂纹的产生机理及预防措施

齿轮热处理质量是造成齿面磨削烧伤与裂纹的内在因素,齿面磨削温度是造成磨削烧伤与裂纹的主要外在诱发因素。通过控制渗碳与淬火过程、调整回火工艺等方式,改善渗碳层的碳浓度与碳含量梯度,碳化物的大小、数量、形态,马氏体形态和残余奥氏体数量等渗碳组织与齿面残余应力状况。基于磨齿工艺降低磨削温度的方法主要包括合理选用砂轮、适当控制磨齿余量与磨削用量以及合理选用冷却液与冷却方式等。     

摆线轮多齿成形磨削热力耦合仿真分析

摆线轮多齿成形磨削为齿轮精加工工艺,一次可完成个齿槽的加工。在高速磨削过程中,齿轮表面会产生瞬间高温,高温可能会造成齿面烧伤,磨削温度场产生的温度梯度会使齿面形成残余应力,使摆线轮齿面金相组织出现变化,影响齿轮的磨削加工精度。通过有限元法模拟摆线轮多齿成形磨削温度场,再采用热力耦合分析方法,得到摆线轮成形磨削温度场和热应力的数值仿真云图,通过对磨削区主应力分析可知,应力主要集中在磨削中心靠齿根部,磨削区呈现热压应力,在已磨削区域,热压应力转变为热拉应力,并逐渐形成残余拉应力,且随着磨削工艺参数变化,节点应力也发生相应变化。研究结论对预测多齿成形磨削温度场和热应力场分布情况和合理选择磨齿工艺参数有一定的研究意义。     

轴承钢顺次磨削表面残余应力离散度试验研究

以轴承钢顺次磨削表面的残余应力离散度为研究对象,基于X射线衍射法顺次测试了轴承套圈淬硬热处理、粗磨、精磨和超精磨削后,轴承滚道表面环向和轴向残余应力.测试结果表明,淬硬热处理工件的残余应力标准差约为超精工序的3倍;淬硬热处理轴承套圈经超精磨削工序,其表面的环向和轴向残余应力离散度降至20 MPa.研究表明淬硬轴承钢热处理及同一道磨削工序工件表面残余应力存在较大离散性,"粗磨-精磨-超精"顺次磨削工艺叠加后,工件表面残余应力离散度呈现收敛性;淬硬热处理轴承套圈经过顺次磨削工序叠加加工后,表面残余压应力平均值获得大幅提高.这为进一步系统揭示磨削工艺对淬硬轴承钢套圈表面残余应力及其离散度影响规律提供了科学数据.     

航空齿轮主轴式滚磨光整表面完整性试验研究

采用主轴式滚磨光整工艺对14CrMnSiNi2MoA航空圆柱直齿轮进行光整加工试验,对航空齿轮滚磨光整前后的表面形貌、残余应力、显微硬度、微观组织等进行了系统研究。结果表明,对磨削后的航空齿轮进行滚磨光整,可以显著改善齿轮表面完整性;滚磨后齿面粗糙度可以降低到0.2μm以下,齿面平均残余压应力可以提高约45%,提高了齿面硬度;滚磨前后齿面粗糙度与残余应力分布表明,主轴式滚磨齿面残余压应力增加量和粗糙度降低量呈现为从齿根往齿顶逐渐升高。试验结果为齿轮滚磨光整工艺参数制定提供了理论依据。     

超声辅助磨削后纳米ZrO_2陶瓷的表面残余应力

在自行研制的二维超声辅助磨削系统下对纳米ZrO2陶瓷进行了磨削加工,采用X射线衍射仪对其表面残余应力进行了测试,研究了磨削参数对其残余应力的影响,并与普通磨削后的表面残余应力进行了比较。结果表明:两种磨削方式下表面残余应力皆为压应力,且随着磨削深度的增大,两种磨削方式下表面残余应力均呈现出减小趋势,但超声辅助磨削后表面残余压应力的减小趋势较普通的缓慢;相同条件下,超声辅助磨削后表面残余压应力大于普通磨削的;其他参数不变,随着砂轮磨料尺寸的增大,两种磨削方式的表面残余压应力都呈上升趋势。     

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.