灰色理论在慢走丝线切割加工中的应用

慢走丝电火花线切割中工艺指标与工艺参数之间具有高度非线性关系,难以实现电火花多工艺参数优化,针对此问题,以电火花线切割SKD11模具钢为试验对象,选用水压、脉冲宽度、脉冲间隔、峰值电流和进给速度为可变因素,表面粗糙度(Ra)和材料去除率(MRR)为工艺指标,设计田口试验,采用灰色关联分析方法研究加工参数对工艺指标的影响关系;建立改进的灰色神经网络模型对Ra和MRR预测,其平均相对误差分别为7.92%和8.13%。结果表明,该模型能反映出电火花线切割SKD11模具钢的工艺规律并能成功预测出Ra和MRR,为电火花线切割SKD11模具钢工艺参数的选择提供了依据。寻找的一组优化参数对SKD11模具钢的线切割加工具有一定的参考意义。     

线切割加工中多目标优化算法的应用

为了解决慢走丝线切割加工中难以同时获得较快加工速度和较优表面质量的问题,从其加工参数与加工指标之间的高度非线性关系入手;选取水压(WP)、脉冲时间(T_(on))、脉冲间隔(T_(off))、电极丝张力(WT)、丝速(WS)和伺服参考电压(SV)作为优化参数,以表面粗糙度(Ra)、材料去除率(MRR)作为优化指标,设计正交实验;创新运用支持向量机回归(SVMR)结合粒子群优化算法(PSO)建立其多目标预测优化模型,得到最优加工参数;实验结果表明,所建立的多目标预测优化模型预测精度高、优化效果显著。     

电极超声复合混粉电火花加工TC4试验研究

为了提高电火花加工TC4合金的加工效率、表面质量,在混粉电火花加工的基础上设计了一套工具电极超声振动装置。以工件去除率MRR和表面粗糙度Ra为工艺指标设计了Box-Behnken试验,应用响应面法建立了加工参数与工艺指标之间的二次回归模型,分析了加工参数对工艺指标的影响;通过对比试验,得出电极超声振动使混粉电火花加工去除率平均值提高了29%;粗糙度Ra值降低22%。对去除率及表面粗糙度进行了多指标优化,参数最优组合为:电极直径为4mm,峰值为20A,脉冲间隔为39μs,铝粉浓度为15.3(g·L~(-1))。试验表明:在大脉冲环境下,电极超声混粉电火加工花仍能获得较好的表面质量。     

高速钢线切割加工试验研究及工艺参数优化

通过单因素实验和正交试验设计,研究四个工艺参数(脉冲宽度、脉冲间距、峰值电流和走丝速度)对两个工艺指标(材料去除率和表面粗糙度)的影响规律。结合多量纲归一化法和加权平均法,通过极差分析对试验数据进行优化,确定各工艺参数对工艺指标影响的主次顺序,获得了线切割高速钢的最优工艺参数组合。对优化后的参数进行试验验证,结果表明:MRR比优化前提高了12.92%,R_a值比优化前减小了13.96%,验证了优化参数的合理性。此研究改善了线切割高速钢的加工性能,为后续科研实践提供可靠的理论依据。     

线切割加工中切缝宽度与材料去除率的优化研究

在精密制造业中,切缝宽度对尺寸精度的影响尤为显著,而材料去除率是影响加工效率的最重要指标,其与切缝宽度之间关系复杂且相互制约,一组加工参数难以同时获得较小的切缝宽度和较高的材料去除率。针对此问题,运用BP神经网络与粒子群算法(PSO)的混合算法建立多目标预测优化模型;以Ti6Al4V合金为实验对象,以水压、脉冲时间、脉冲间隙、伺服电压和电极丝张力为工艺参数,以切缝宽度(Kerf)和材料去除率(MRR)为工艺目标,设计田口实验。结果显示,Kerf和MRR的预测平均相对误差分别为5.32%和6.14%,优化得到单目标和多目标最优工艺参数,Kerf同比降低11.10%,MRR同比提高27.37%,表明对切缝宽度和材料去除率的预测与参数优化效果显著。     

放电参数对短电弧铣削TC4加工性能影响的研究

短电弧加工技术(SEAM)是一种实现难加工导电材料高效去除的新型放电加工方法。采用不同电极材料,开展钛合金TC4短电弧铣削加工试验,探究在不同放电参数(电压、频率和占空比)下对加工过程中材料去除率(MRR)、相对电极相对损耗率(RTWR)的影响规律;并进一步分析工件宏微观形貌、元素变化及硬度测定。试验表明：影响MRR和RTWR的因素为脉冲电压>脉冲占空比>脉冲频率;紫铜电极具有高的材料去除率和好的表面质量;加工后表面存在重铸层、熔滴和微孔等结构;其表面显微硬度由重铸层向基体逐渐降低,并在距离工件表面深度90μm处趋于稳定。由此证明,金属电极材料更适合SEAM加工钛合金材料,这为后续SEAM加工钛合金零部件提供了理论依据。     

基于响应曲面法的不锈钢电解质等离子体抛光工艺参数优化

采用响应曲面法中的Box-Behnken(三因素三水平)实验设计方法,根据实验结果分别建立电压、温度和电解质浓度3个工艺参数下的表面粗糙度和材料去除率响应曲面分析模型;通过研究表面粗糙度Ra和材料去除率MRR在各工艺参数相互影响下的响应曲面和等高线图,得到工艺参数对响应因子即表面粗糙度Ra和材料去除率MRR的影响规律,以及相应目标下的最优工艺参数组合;对最优工艺参数组合进行实验验证并检验模型的准确性。单目标参数优化结果显示,当电压为262 V、温度为80℃及电解质浓度为3.5 wt%时,表面粗糙度Ra达到最小值0.055μm;当电压为239 V、温度为71℃及电解质浓度为4.0 wt%时,材料去除率MRR达到最大值4.766μm/min。双目标参数优化结果显示,当电压为238 V、温度为72℃及电解质浓度为3.8 wt%时,表面粗糙度Ra和材料去除率MRR分别为0.071μm和4.413μm/min。实验验证结果显示,单目标优化时样品的表面粗糙度Ra=0.057μm、材料去除率MRR=4.980μm/min;多目标优化时样品的表面粗糙度Ra=0.078μm,材料去除率MRR=4.292...     

热处理工艺对工件线切割加工性能的影响

热处理工艺在现代制造业中占有极其重要的地位,为了探究热处理工艺对工件线切割加工性能的影响,运用田口实验设计方法,分析了SKD61热作模具钢在不同热处理工艺下线切割加工的加工性能。实验结果表明,热处理工艺对工件的材料去除率(MRR)和表面粗糙度(Ra)均有较大的影响,在线切割加工中不能忽视这一影响因素且必须予以足够地重视;同时运用主效应分析方法分析了热处理方式及其它加工参数对MRR和Ra的影响规律,实验结论对于进一步指导实际加工具有一定的参考意义。     

放电成型加工中的单晶硅材料去除率建模分析与实验研究

在半导体材料放电加工可行性的基础上,分析了影响材料去除率的几个主要因素,其中包括空载电压、峰值电流、脉冲宽度以及脉冲间隔。采用中心组合设计实验,考察峰值电流、脉冲宽度、脉冲间隔这3个因素对单晶Si放电加工的材料去除率的影响,建立了单晶Si放电加工的材料去除率的响应模型,进行响应面分析。方差分析结果表明模型具有很好的拟合程度和适应性。采用满意度函数(DFA)确定了单晶Si放电加工的最佳工艺参数,当峰值电流取18.5A、脉冲宽度取358.62μs、脉冲间隔取20μs时,满意度为0.912,此时材料去除率的最优值为76.26 mm~3/min。用所确定的最佳工艺参数在电火花成型机床上重复多次实验,测得P型单晶硅的平均MRR为73.86 mm~3/min。模型预测结果与最佳工艺参数下的实验结果平均相对误差为3.2%,验证实验表明该模型能实现相应的半导体材料放电加工过程的材料去除率预测。     

WEDM-HS高效率低损耗加工技术的研究

分析了WEDM-HS(高速走丝电火花线切割机床)加工中,电流阶梯波脉冲对优化极间放电能量分配的作用,研究了脉冲上升沿斜率对提高加工效率和降低电极损耗的影响。设计出单片机电流斜率控制脉冲电源,进行了一系列加工试验,确定了优化的高效率低损耗加工参数。     

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.