复合Si3N4刀具切削高锰钢时的磨损、破损机理

研究了复合Si3N4刀具切削难加工的高锰钢时的磨损、破损机理。通过试验测量了刀具后刀面磨损宽度分别与切削时间和切削速度的关系，用扫描电镜显微分析了复合Si3N4的磨损和破损形貌和元素变化。结果表明，随着切削时间的延长，Si3N4刀具表面依次出现积屑瘤、扩散磨损和机械、扩散、粘结复合型磨损形式；刀具的破损形式分别发生在高速切削初期的脆性断裂和长时间切削导致的热震破裂；刀具的最佳切削速度为60-70m/min。     

新型刀具材料切削大型高锰钢托轮的试验研究

用于露天煤矿大型托轮的高锰钢属于难加工材料。本文采用新型复合SiC、复合Si3N4和TiN涂层硬质合金刀具对高锰钢进行了切削加工对比研究。试验表明:复合SiC刀具是切削高锰钢的较理想刀具,在切削效率和经济效益上均优于TiN涂层硬质合金和复合Si3N4刀具。高锰钢在脆化温度范围内(400℃～800℃)极易导致TiN涂层硬质合金和复合Si3N4脆性破裂,而复合SiC在此时仅发生机械磨损;在切削温度高于高锰钢的脆化温度时,复合SiC和复合Si3N4都会发生扩散磨损。     

新型Al_2O_3基陶瓷刀具材料加工淬硬40Cr的切削行为

采用自主研制的两种新型Al_2O_3基微米复合陶瓷刀具AC2N和纳微米陶瓷刀具AC2Nn2切削淬硬40Cr合金钢,以LT55为对比刀具,选用不同的切削速度和不同进给量进行干式连续切削,研究了两种新型Al_2O_3基复合陶瓷刀具的切削行为。结果表明:在加工淬硬40Cr的试验中,新型Al_2O_3基陶瓷刀具的切削性能和抗磨损性能优于LT55;微米陶瓷刀具AC2N适合在小进给量条件下加工淬硬40Cr,纳微米陶瓷刀具AC2Nn2适合在高速、大进给量条件下加工淬硬40Cr。在v=260m/min、f=0.12mm/r、a_p=0.1mm的试验条件下,AC2N陶瓷刀具的磨损形貌以磨粒磨损和扩散磨损为主,AC2Nn2陶瓷刀具的磨损形貌以磨粒磨损和氧化磨损为主。     

PCBN刀具切削GCr15淬硬轴承钢时刀具磨损的研究

通过切削实验，研究了PCBN刀具切削淬硬轴承钢时刀具磨损形态及磨损机理。实验表明。PCBN刀具前刀面的磨损为月牙洼磨授，后刀面的磨损为机械磨损，其磨损程度与工件硬度呈非线性关系，并随着切削速度的提高磨损量减少。     

PCBN刀具高速切削抗氢钢HR-2的性能研究

采用不同CBN含量和晶粒结构的PCBN刀具,在不同切削速度下进行了HR-2抗氢钢的高速精密切削试验。通过对PCBN刀具前、后刀面的显微形貌特征进行观测,分析了刀具的失效磨损机理,研究了不同CBN含量及不同切削速度对刀具使用寿命的影响。对刀具磨损的测量结果表明,PCBN刀具高速切削HR-2时,CBN含量高的刀具显示出更长的使用寿命,且在130-200m/min区间为最佳切削速度区域。SEM和EDS分析结果表明,高速精密切削HR-2的磨损机理为氧化磨损、扩散磨损、粘结磨损,同时存在磨粒磨损以及引起的微崩刃现象。     

涂层刀具高速铣削高强钢刀具磨损及加工成本分析

选用PVD-TiAlN+TiN复合涂层硬质合金刀具高速铣削高强钢AISI4340,探讨了铣削参数对后刀面磨损的影响,并分析了加工成本。通过响应优化器得到具有95%置信度的理论最佳加工参数,采用Gilbert方法计算了加工成本,验证了该涂层刀具在高速铣削AISI4340时的经济可行性。结果表明,切削速度对后刀面磨损的影响最为显著,径向切深没有统计上的显著性,但径向切深在1～3 mm时,后刀面磨损随径向切深的增加而增加。PVD-TiAlN+TiN复合涂层硬质合金刀具高速铣削AISI4340钢在最佳切削参数vc=350 m/min,fz=0. 03 mm/z,ap=0. 6 mm,ae=4 mm条件下的刀具寿命为31. 30 min,估计加工成本为17. 35。该研究对高强钢的高效低成本加工具有指导意义。     

硬质合金刀具切削Ti6Al4V的磨损机理及特征

为研究硬质合金刀具在不同切削速度下切削钛合金时,刀具材料中的合金成分对刀具磨损机理及特征的影响,采用YG8、YT15和YW2三种牌号的硬质合金刀具进行干切削Ti6Al4V试验。研究切削速度分别为48 m/min、71 m/min、100 m/min时,三种硬质合金刀具的磨损形貌与磨损机理,分析在低、中、高速切削时三种刀具的磨损机理对其磨损速度的影响。结果表明:低速切削时三种刀具均以黏结磨损为主;高速切削时YG8刀具仍以黏结磨损为主,YT15刀具在发生黏结磨损的同时会产生一定程度的扩散磨损和氧化磨损,YW2刀具的磨损中黏结磨损、扩散磨损和氧化磨损占据同样地位;高速切削时选用YW类刀具更为适合。     

PCD刀具干式车削Ti6Al4V的正交试验研究

通过正交试验法研究PCD刀具干式车削Ti6Al4V时切削速度、进给量和切削深度对工件表面粗糙度和刀具后刀面磨损的影响。试验结果表明,切削速度为120-160m/min、进给量为0.15mm/r、切削深度为0.15mm时,可以获得理想的工件表面粗糙度和刀具后刀面磨损量。     

加工含镍球墨铸铁时梯度陶瓷刀具的失效机理

研究了Al2O3／TiC梯度陶瓷刀具干切削含镍球墨铸铁的切削性能及损坏机理。结果表明,梯度陶瓷刀具的寿命约为硬质合金YS10刀具的1—2倍,且切削速度愈高,梯度陶瓷刀具的优越性愈显著;其损坏形式：低速切削时,为磨粒磨损;高速切削时,为剥落及粘结磨损。     

超耐热合金的高速切削试验

<正> 山德维克公司对Inconel 718进行切削加工试验,阐明了切削速度对刀具磨损的影响。试验切削参数为进给量0.15mm/r,切削深度1.5mm,切削速度150m/min。切削10分钟后进行观察,发现纤维增强氧化铝陶瓷刀具已出现后面磨损、边界磨损和崩刃等缺陷;当切削速度为450m/min时,则仅在刃部出现磨损。用     

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.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.