球轴承外圈沟道ELID成形磨削工艺参数优化

为了优化球轴承外圈沟道ELID(Electrolytic In?process Dressing)成形磨削工艺参数,通过多因素正交试验研究了ELID成形磨削过程中磨削参数和电解参数对砂轮磨损和工件表面粗糙度的影响规律,综合砂轮径向磨损量和工件表面粗糙度两个指标对磨削试验进行了综合评估.结果表明,磨削参数中的径向进给速度对砂轮径向磨损量的影响最大,砂轮转速对工件表面粗糙度影响最大;电解参数中的占空比对砂轮径向磨损量的影响较大,电解电压对工件表面粗糙度影响较大;砂轮转速为18000 r/min,工件转速为100 r/min,径向进给速度为1μm/min,占空比为50％,电解电压为90 V(6.7Ω)时,综合效果最优.     

超硬涂层磨削工艺实验研究

针对核主泵关键部件材料镍基碳化钨涂层,采用三种磨粒粒度金刚石砂轮进行平面磨削试验,研究工艺参数、磨粒粒度对涂层材料磨削力、表面粗糙度和表面残余应力的影响规律。实验结果表明:不同粒度砂轮磨削时,随着磨削深度和工件进给速度增加,法向磨削力和切向磨削力均逐渐增大,表面粗糙度值呈现先增大、后减小再增大的趋势,平行和垂直磨削方向的表面残余压应力逐渐增大,且垂直磨削方向应力值更大。综合考虑磨削力、表面粗糙度、磨削表面残余应力和磨削加工效率,600目砂轮具有较好的加工效果,其对应的优化磨削参数为:磨削深度为10μm,工件进给速度为8 m/min。     

38CrMoAl渗氮钢微晶刚玉砂轮摆线磨削工艺试验研究

在实际磨削38CrMoAl渗氮钢过程中,存在磨削烧伤情况。本文分别采用白刚玉砂轮和微晶刚玉砂轮磨削38CrMoAl渗氮钢,对比研究了不同磨料类型刚玉砂轮对磨削力和表面粗糙度的影响规律。试验结果表明：相较于白刚玉砂轮,微晶刚玉砂轮磨削时磨削力降低了14.2%。基于正交试验方法,通过微晶刚玉砂轮平面磨削试验,探究了磨削工艺参数对磨削力和工件表面粗糙度的影响。结果分析表明：磨削深度对磨削力影响最大,其次是工件进给速度和砂轮转速;对于工件表面粗糙度而言,工件进给速度的影响最大,其次是砂轮速度和磨削深度。最终采用微晶刚玉砂轮对38CrMoAl渗氮钢齿轮样件进行批次加工,结果显示无磨削烧伤发生,且磨削表面质量得到了显著提高。     

氮化硅陶瓷轴承套圈滚道的高效高质量磨削试验研究

为提高氮化硅陶瓷圆柱滚子轴承套圈滚道的表面质量及磨削效率,使用超高速万能外圆磨床对套圈滚道进行高速磨削试验,分析了工件线速度、砂轮线速度和进给速度等磨削参数对套圈滚道磨削表面质量与磨削效率的影响机制与规律。试验结果表明,套圈滚道表面粗糙度随着工件线速度及砂轮线速度的增大呈先减小后增大的趋势,随着进给速度的增大而增大;当磨削速比为200时,随着砂轮线速度的增大,套圈滚道表面粗糙度变化不大,比磨除率增大,磨削效率提高;当砂轮线速度为150 m/s、工件线速度为0.75 m/s时,进给速度的增大使比磨除率增大,但套圈滚道表面质量变差;在试验条件下,套圈滚道高速磨削后表面粗糙度值在0.065 0～0.098 5μm范围内,满足精密加工要求。为提高磨削效率,推荐磨削速比为200、砂轮线速度为120～150 m/s和进给速度为18～28μm/min。     

硬质合金立铣刀螺旋槽磨削表面粗糙度模型研究

基于立铣刀螺旋槽的加工原理,根据安装参数确定砂轮磨削螺旋槽的磨削接触区;分析螺旋槽磨削接触区内砂轮与工件的等效直径和有效速度,发现立铣刀螺旋槽磨削既有外圆磨削的特点也有内圆磨削的特征。考虑硬质合金工件材料塑性隆起和砂轮速度与工件速度之间夹角对表面粗糙度的影响,建立立铣刀螺旋槽磨削表面粗糙度计算模型,分析砂轮直径、砂轮速度和工件进给速度对磨削表面粗糙度的影响。在五轴联动数控工具磨床上使用金刚石平行砂轮进行螺旋槽磨削试验。使用超景深显微镜对立铣刀螺旋槽磨削表面形貌进行分析,使用白光干涉仪测量螺旋槽磨削表面粗糙度大小。试验结果验证了硬质合金立铣刀螺旋槽磨削表面粗糙度计算模型的正确性。该模型为其他整体式刀具螺旋槽磨削表面粗糙度的计算提供了理论参考。     

不锈钢超高速磨削试验研究

为避免不锈钢磨削中发生砂轮堵塞,减轻磨削烧伤的程度,提高加工效率,优化加工工艺,对不锈钢进行超高速磨削试验研究。在高速/超高速磨削条件下,研究了不同砂轮线速度、工件进给速度和进给量对不锈钢磨削的磨削力、表面粗糙度和表面形貌的影响作用,并检测了不同工况下的砂轮表面状态。研究结果表明,不锈钢在超高速磨削状态下,选择合理的工作台速度和磨削深度能有效提高加工效率,同时又能保证磨削质量。
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主动测量磨削过程中加工尺寸精度的试验研究

本文对主动测量外圆切入磨削过程中的加工尺寸精度进行了试验研究。考察了工件初始尺寸输入误差、工艺系统固有误差、切入进给速度对加工尺寸精度的影响。研究结果认为:在外圆切入磨削过程中,主动测量控制方式能很好地消除工艺系统的热变形、砂轮磨损、修整补偿误差等因素的影响,使工件初始尺寸输入误差和工艺系统的有关系统性误差不成为影响加工误差的主要因素;切入进给速度对加工尺寸精度有一定的影响。     

某航天型号轴类工件的ELID精密磨削加工工艺技术研究

为了探究SiCp/Al复合材料轴类工件精密加工的新途径,采用ELID精密超精密磨削加工技术,对其进行精密加工试验,并分析加工机理及试验影响因素。试验结果表明:砂轮转速、进给量、磨削深度和进给速度是影响表面加工质量的主要因素。当砂轮转速在1 500 r/min、磨削深度是3μm和进给量为0. 25μm时,磨削效果最佳,可以有效地提高加工效率,改善工件表面加工质量,得表面粗糙度R_a为0. 163μm、圆柱度为0. 85μm的已加工表面。     

磨削工艺参数对硬质合金刀具磨制损伤的影响

硬质合金刀具被广泛应用于航空航天、汽车、冶金等高端制造领域。硬质合金刀具的生产通常采用金刚石砂轮磨削加工,因此,砂轮的磨削工艺参数对刀具的成品质量有重要影响。本试验通过改变砂轮的线速度及进给速度加工硬质合金麻花钻,加工完成后,采用超景深显微镜、白光干涉仪和扫描电镜对钻头的磨削表面以及亚表面进行检测,分析砂轮进给速度及线速度对加工损伤的影响。结果表明：砂轮进给速度和线速度越大,锯齿量越大;当线速度与进给速度较小时,钻头的主切削刃易出现微崩刃现象;砂轮进给速度越大,钻头后刀面表面粗糙度越大;砂轮线速度越大,钻头后刀面表面粗糙度越小;钻头后刀面处的亚表面最大损伤深度随线速度的增大而减小;当线速度30m/s、进给速度160mm/min时,钻头的磨削损伤最小。     

基于表面粗糙度均匀性的曲面磨削研究

针对曲面磨削中不同曲率处的表面粗糙度不均匀的问题,基于等残留高度法,分析了砂轮圆弧半径、砂轮进给速度、工件转速以及工件曲率对残留高度的影响.结果显示,为得到较小的残留高度,应尽量保持低的砂轮进给速度,并且提高工件转速.曲率半径越小,粗糙度差异越大,改变砂轮进给速度可改善这一问题.砂轮的进给速度与曲率半径大小成正比.采用金刚石滚轮法以及砂轮变速进给可有效改善曲面磨削的表面粗糙度均匀性.     

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.