特殊晶体材料飞刀切削加工工艺的分析与优化

采用二次通用回归旋转组合设计方法,对KDP晶体的切削加工工艺进行优化设计;利用单点金刚石飞刀切削(single point diamond turning,SPDT)技术对其进行切削。对试验结果进行测量与分析,确定合理的试验因素及水平,分析加工工艺参数的单因素和交互因素对KDP晶体表面粗糙度的影响规律。最后得到最优工艺参数组合:刀具圆弧半径为5 mm,转速为800 r/min,进给量为1μm/r,背吃刀量为21μm,加工出的KDP晶体表面粗糙度值为0.017μm。     

KDP晶体表面质量主要影响因素的研究

针对KDP晶体超精密加工过程中出现的表面波纹度和粗糙度问题,采用二次通用回归旋转组合优化设计法及单点金刚石飞刀切削(SPDT)技术,对KDP晶体进行切削实验,对加工过程进行在线监测,利用多因素交互作用分析KDP晶体表面波纹度和粗糙度的影响规律。最后利用偏最小二乘法及lingo软件获得最佳加工工艺参数组合,即当刀具圆弧半径为9mm;转速为800 r/min;进给量为9.184μm/r;背吃刀量为21μm时,加工出KDP晶体的表面波纹度值为0.020μm,表面粗糙度值为0.017μm,对后续能够加工出更大口径(400×400)mm的高质量KDP晶体以满足航空航天领域应用具有重要的实际意义。     

KDP晶体表面波纹度的分析与研究

针对工艺参数对KDP晶体表面波纹度值的影响问题,基于二次通用回归旋转组合方法优化KDP晶体单点金刚石飞刀切削工艺参数组合,采用单因素和多因素法分析各因素对表面波纹度的影响规律,并以此为基础优化工艺参数,进行KDP晶体切削实验。试验表明:各因素对表面波纹度的影响程度大小顺序为:进给量二次项、进给量、转速、转速与进给量的交互作用。优化出表面波纹度值最小时的加工工艺参数组合:刀具圆弧半径为9mm;转速为633r/min;进给量为11.8μm/r;背吃刀量为21μm,利用此组工艺参数加工出KDP晶体的表面波纹度为0.02μm。     

KDP晶体表面波纹度的监测与分析

采用二次通用回归旋转组合设计方法和单点金刚石飞刀切削(Single Point Diamond Turning,简称SPDT)技术,对KDP晶体进行切削试验。利用声发射技术对KDP晶体不同表面波纹度的信号进行采集,对试验结果进行测量与分析。通过时域分析可得到:均方值可作为KDP晶体加工过程中表面波纹度在线监测的重要时域特征量;通过频域分析可得到:150~200 k Hz可作为在线监测KDP晶体表面波纹度度的特征频段。     

KDP晶体超精密加工技术的研究

通过对KDP晶体等脆性材料的塑性域切削进行理论分析，研究实现脆性材料塑性域切削的条件。激光核聚变KDP晶体的3项主要技术指标是：表面粗糙度、波纹度和透射波前。通过分析影响这3项技术指标的因素。提出了实现KDP晶体精密加工的超精密机床和工艺参数。通过理论分析与实验。研究了晶向、刀具前角、刀具圆弧半径和进给量等参数对表面粗糙度的影响，最终给出KDP晶体精密加工的最佳工艺参数。     

KDP晶体超精密加工切削力的实验研究

KDP晶体是一种常用的非线性光学材料,广泛应用于激光变频、电光调试和光快速开关等高技术领域。文中通过实验研究了KDP晶体超精密切削加工的切削力特性,分析了切削深度、进给量对切削力的影响,并对KDP晶体和铝合金的切削力进行了比较。研究结果表明,立轴平面铣削KDP晶体的切削力Fz、Fy随着切削深度和进给量的增加而增加,但增加的速度远小于铝合金的切削力Fz、Fy增加速度。实验证明了在生产实际中加工KDP晶体时,在不影响加工表面质量的前提下,可以适当加大切削深度和进给量,从而提高切削效率。     

KDP晶体微塑性域增强金刚石切削方法研究

针对KDP在SPDT切削过程中容易产生凹坑、划痕、裂纹等表面缺陷问题,提出利用热激励的方式增大KDP晶体塑性切削域深度,降低各向异性、机床运动误差、环境振动等因素对加工过程的影响,进而提高SPDT切削加工过程稳定性的方法。通过纳米压痕试验获得了KDP晶体表面在不同温度状态下的硬度和脆塑性转变深度变化规律,并在SPDT机床上采用金刚石刀具开展了KDP晶体飞切划痕实验,进一步验证了适当提高KDP晶体温度可以增大KDP晶体脆塑性转变临界切削深度。在此基础上,对KDP晶体开展了不同温度状态下的切削实验,实验结果表明在相同工艺参数下,随着温度的升高,表面粗糙度Sa值从3.2nm降低至1.6nm。     

KDP晶体光学零件超精密加工技术研究的新进展

KDP晶体作为优质的非线性光学材料 ,被广泛的应用于激光非线性光学领域。由于大型KDP晶体具有一系列不利于光学加工的特点 ,因此被公认为是最难加工的光学零件。本文概述了KDP晶体超精密磨削和磁流变抛光的加工方法 ,阐述了KDP晶体光学零件单点金刚石加工技术的研究现状 ,并详细地分析了单点金刚石切削加工时机床精度、加工工艺参数、装夹变形、晶格方向变化、金刚石刀具几何参数、冷却液等对加工表面质量 (平面度、表面粗糙度、小尺度波纹等 )的影响     

KDP晶体各向异性对切削力的影响研究

对KDP晶体单点金刚石切削中动态切削力产生的原因及变化规律进行深入研究,以揭示材料各向异性对KDP晶体超精密加工切削力的影响。以微观塑性力学和断裂力学理论为基础,建立了切削力新模型,并优选出最佳晶体切削方向,以降低由材料各向异性引起的切削力波动对加工表面质量的影响。     

晶体已加工表面频率特征对亚表层温度场的影响

为了更加准确地分析表面形貌对KH2PO4(KDP)晶体元件激光损伤和使用性能的影响，通过功率谱密度和连续小波变换对KDP晶体已加工表面存在的实际频率特征进行提取和重构。利用波动光学理论分析经入射波长1.064 μm、功率20 MW/μm2的激光束照射1 ns后，表面频率特征对KDP晶体亚表层光场及温度场的影响。结果表明，当表面频率特征的波长越接近入射光波长1.064 μm，KDP晶体亚表层的光场畸变现象越严重，会造成局部聚焦，温度越高；当波长超过20 μm时，在振幅不变的情况下，最高温度随着波长的增加基本不变。通过切削实验获得的KDP晶体已加工表面上明显存在的波长分别为14 μm、50 μm和140 μm，对KDP晶体亚表层造成的温升分别为56 K、22 K和12 K。当波长相同时，KDP晶体的最高温度与表面频率幅值成线性关系。随着表面频率波长的增加，温度最高点的位置向KDP晶体内部延伸。     

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...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

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.     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

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....     

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.