准双曲面齿轮动态啮合性能的有限元分析研究

研究准双曲面齿轮动态啮合有限元分析模型的构建方法,建立了合理的有限元模型。基于接触动力学的基本理论和显式有限元分析方法,对准双曲面齿轮的动态啮合性能进行了研究,得到啮合接触冲击特性、齿面接触区域、齿面接触应力及齿根弯曲应力等在轮齿动态啮合过程中的变化规律。以转速和负载两个典型的工作条件为变量,建立对比分析模型,研究转速和负载对准双曲面齿轮动态啮合性能的影响。转速对准双曲面齿轮动态啮合性能影响显著,而负载对准双面齿轮的动态啮合性能影响则跟转速有关,随着转速的增大,相同的负载变化对动态啮合性能的影响逐渐减弱。     

A new approach for estimation of defects detection with infrared thermography

A new approach is proposed for a priori ascertaining the suitability of infrared thermography for the non-destructive evaluation purposes of materials. The novelty regards a cause/effect relationship between the thermal signature perceived by the infrared camera and a dimensionless group, which includes geometrical and thermal characteristics of the defect and host material. Such relationship, which was experimentally assessed through the evaluation of several specimens, is helpful to predict the thermal contrast associated with a type of defect embedded inside a certain material. This prediction of course is useful in decision making about the use of infrared thermography without preliminary feasibility tests and thus with economic benefits.     

Evaluation of gluing of CFRP onto concrete structures by infrared thermography coupled with thermal impedance

Carbon Fiber Reinforced Polymers (CFRPs) have been increasingly employed for structural strengthening, and are attached to structures using bonding adhesives. The aim of this work is to characterize defects in the bond between CFRP and concrete (after they are located by pulse infrared thermography), and assign the defects a “numerical value” (ranging from 0 for a complete air–gap to 1 for a fully glued bond). Quantitative characterization is performed by measuring the thermal impedance, and then identifying the thermophysical parameters of the system through fitting the measured impedance to a theoretical model. An inversion procedure is carried out to estimate the unknown parameters, without prior knowledge of sample properties. In particular, it is possible to estimate more accurately both the amount of glue within a defect and the thermal contact resistance.     

Crack detection of plastic gears using a convolutional neural network pre-learned from images of meshing vibration data with transfer learning

Forschung im Ingenieurwesen - In this paper, a crack detection method of plastic POM (Polyoxymethylene) gears using a deep convolutional neural network is proposed. The vibration...     

Investigation on the flank surface durability of gears with increased pressure angle

Within a funded research project (reference number 0325244C, BMWi – Federal Ministry for Economic Affairs and Energy of Germany), the load-carrying capacity of alternative involute gears was investigated. To find qualified variations for use in gear drives, increased pressure angles (α_n > 20°) and/or asymmetric tooth shapes (α_n < 20° and α_n > 20°) have been examined experimentally. Optimization goals were the power to weight ratio of the transmission and the power density in the drive train.In this report gears with reference tooth shape (α_n = 20°) as well as gears with modified tooth shape (α_n = 28°) are discussed with focus on the load carrying capacity of the tooth flank with special regard to the damage mechanisms pitting, micro-pitting and scuffing. The results of experimental and test accompanying studies are shown. They allow a direct comparison between standard and special gears as well as a classification in context of the actual state of knowledge.     

Investigation of the oxidation of sialons with infrared reflection spectroscopy

Hot-pressedβ-sialons (Si_6-z Al _z O _z N_8-z formed in the Si₃N₄-Al₂O₃-AIN and Si₃N₄-SiO₂-AIN systems have been investigated using infrared reflection spectroscopy (IRRS). Asz increases, the IRRS bands decrease in frequency. The decrease can be explained by the decrease in the force constants of the chemical bondings. IRRS has been applied to the study of the oxidation sialons at 1200 and 1300°C as a function of time. The technique has sensitively detected cristobalite, mullite and glass phases on the oxidized surface. This is considered to be effective for understanding the oxidation kinetics of sialons.     

Global and local characterization of the thermal diffusivities of SiCf/SiC composites with infrared thermography and flash method

Two types of SiC_f/SiC composites with different matrix quantities are prepared by CVR from pyrolyzed Carbon/resin composites. Experiments based on transient, space-resolved infrared thermography are developed; various assessment methods are implemented to measure simultaneously transverse and in-plane thermal diffusivities, globally and locally; the emphasis is set on the accuracy of the estimations. The material anisotropy is revealed and the influence of matrix volume fraction on the global thermal diffusivities is evaluated. Gradients of the properties are clearly visible in the samples, by use of the local analysis. The global heat conductivity values are discussed with respect to previous works.     

Switching transient analysis of a metal/ferroelectric/semiconductor switch diode with high speed response to infrared light

A thin PbTiO(3)-n-p(+) silicon switch diode has been developed, in which the switching voltage (the turned-on voltage) changes in proportion to the infrared light power. The diode has a rapid response time of 0.65 mus compared with other conventional infrared sensors. It is attributed to the rapid switching device structure and the smaller pyroelectric layer thickness, 50 nm. In this paper, we have analyzed the rapid switching transient response by using heat conduction and switching theory successfully. The experimental results are in agreement with the theoretical analysis.     

Investigation of optical properties of benzocyclobutene wafer bonding layer used for 3D interconnects via infrared spectroscopic ellipsometry

Benzocyclobutene (BCB) used for bonding silicon wafers to enable 3D interconnect technology is characterized using spectroscopic ellipsometry (SE). SE is a non-destructive technique that has been used to characterize the thickness and dielectric properties of BCB. The infrared (IR) absorption spectrum was used to calculate the percentage of curing of BCB on 300 mm bare and bonded wafers. The percentage of curing in BCB is a key parameter that impacts the bond strength and bond quality. This study presents the potential application of IRSE for measurements on bonded wafers to characterize the chemical information, curing percentage, bond quality and thickness of the BCB bonding layer. One of the key issues in the process development and characterization of BCB bonding for 3D interconnects of 300 mm wafers is the presence of dendrites and voids between the bonded wafers. The presence of dendrites and voids was identified by using scanning acoustic microscopy (SAM) and imaged by scanning electron microscope (SEM).     

Investigation of the oxidation of a carbon-ceramic composite with infrared reflection spectroscopy

Journal of Materials Science Letters -     

Enhanced infrared response of ultra thin amorphous silicon photosensitive devices with Ag nanoparticles

Small silver (Ag) nanoparticles (with diameter smaller than 50 nm) can lead to a resonant light absorption accompanied by an enhanced electromagnetic field in their vicinity when they are irradiated by light due to so-called localized surface plasmon. In order to study the influence of metal nanoparticles in thin-film silicon solar cells in more detail, a photosensitive test structure based on a-Si:H and consisting of a TCO/(nanoparticles)/i/n/TCO layer stack was realized. A higher quantum efficiency of the test structure is achieved for wavelengths longer than 800 nm compared to the structure without nanoparticles. As a-Si:H only efficiently absorbs light for wavelenghts of up to 800 nm, the enhanced photocurrent cannot be explained by improved light absorption in a-Si:H.     

红外高发射陶瓷涂层发射率与厚度关系

红外陶瓷涂层在满足高发射率设计要求的前提下, 应尽量降低涂层厚度, 以满足力学性能要求, 节约原料, 减轻器件重量。因此探索厚度与发射率之间的定量关系, 是高发射率涂层研制中的一项重要内容。本文作者通过在水解法制备的氧化铝溶胶中加入高发射率填料, 制备了高发射率涂料, 并采用喷涂和旋涂工艺得到几种不同厚度的高发射复合陶瓷涂层。通过实验测试考察了复合陶瓷涂层的发射率随涂层厚度的变化规律, 确定了复合涂层的临界厚度。在均匀涂层发射率与厚度关系模型的基础上, 结合Maxwell-Garnett理论, 建立了复合涂层发射率与厚度的理论关系模型。该模型对发射率的计算结果与实验值吻合较好, 表明该模型可以用于实际复合涂层的发射率或临界厚度的预报。      

瞬时高能量加热法的红外无损检测技术模拟

在传热学基础上,分别针对含不同深度缺陷的混凝土和铬钢试件建立了二维传热模型,并从理论上对试件采用瞬时高能量加热,在2ms的时间内对试件表面施加4.8kJ热量.在此基础上,利用大型数值计算软件Matlab对试件表面瞬态温度场进行了计算分析,确定了在瞬时高能量加热下缺陷深度与表面温差的关系及最佳检测时间;同时对不同材料缺陷检测效果进行分析比较,发现以混凝土为代表的非金属材料,对于距表面10mm以内的缺陷,可以在不到3分钟的时间内检测出;对于金属材料,表面温升很小,只有当缺陷在距表面5mm内,可以进行检测分辨,且对检测时间要求较高.     

不同形貌ZnO的制备、表征及8～1μgm红外发射率研究

采用低温水热法，分别用溴化十六烷基三甲基铵（CTAB）和聚乙二醇（PEG-400）作为表面活性剂，合成了具有新颖结构的花瓣状和针状ZnO。采用X射线衍射仪（XRD）、扫描电镜（SEM）对花瓣状、针状以及四针状ZnO样品进行结构、形貌表征，用红外吸收光谱（IR）分析样品的红外吸收特性，通过IR-2型发射率测试仪测试样品在8～14μm波段的红外发射率。测试结果表明，花瓣状ZnO发射率最高，针状其次，四针状最低。利用粒子散射机制对形貌与发射率的关系进行了分析。     

Investigation of submerged turbulent gas jets with different densities

The results obtained in measuring the parameters in transverse sections and along the axis of submerged helium, air, and Freon jets are given along with the trends in the variation of the apparent additional mass of these jets.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 34, No. 3, pp. 493–499, March, 1978.     

带温度补偿结构的高灵敏度光读出红外成像阵列器件设计

本文提出了一种光读出红外成像阵列器件的结构设计,该设计提高了器件的热-机械灵敏度,同时能有效降低周围环境温度变化所带来的影响.理论计算表明,该阵列器件的关键性能指标热-机械灵敏度和噪声等效温差分别为2.39×10-3和2.42,此外,ANSYS模拟仿真的结果验证了该设计能抑制周围环境温度波动对器件红外目标探测的影响.     

Investigation of Fe2O3–Al and Cr2O3–Al reactions using a high speed video camera

Abstract

Self propagating high temperature synthesis is a simple, fast and energy efficient process with a wide range of applications, one of which is the coating of the internal surfaces of steel pipes using a centrifugal thermit process. The process involves a highly exothermic reaction between powder reactants distributed around a steel tube rotating at high speed. Although the process has been widely studied, important features, particularly how the reaction propagates, have not been completely revealed due to extremely high reaction rates and temperatures. In the present work, Fe₂O₃–Al and, to a lesser degree, Cr₂O₃–Al reactions were studied under stationary (non-rotating) and rotating conditions using a high speed video camera by which the centrifugal thermit process was, for the first time, recorded optically. Video recordings clearly demonstrate that, in contradiction to current belief, the reaction does not always propagate in a well ordered (spiral) pattern, but involves multiple, randomly distributed ignition sites.     

Preparation of single conjugated polymer nanofibers with high opto-electric response

Single pristine poly(p-phenylene vinylene) (PPV) nanofibers were prepared by electrospinning. The fibers were characterized by fluorescence microscopy, scanning electron microscopy, and polarized fluorescence spectra. The results indicated that the fibers were stretched and oriented toward to rollup direction during the electrospinning process and PPV polymer molecules were oriented with their conjugated backbones along the PPV fiber direction. The parallel array of countable PPV nanofibers was assembled into a photoconductor device. The device shows much higher sensitivity to photo detection than device with PPV film, indicating efficient carrier transport in the well-oriented polymer fibers. This facile, easily operated method for the fabrication of well-oriented fibers indicates its potential application in optoelectronic devices.     

Solvability and thermal response of cellulose with different crystal configurations

Cellulose is a biodegradable and renewable natural material that it is naturally resistant to breaking and modification. Moreover, the crystalline structure of cellulose is a major factor restricting its industrial utilization. In this study, cellulose polymorphs were prepared from natural cellulose, and their solvability and thermal response were investigated. Using liquid- and solid-state NMR signals, the distinct types and dissolving states of cellulose polymorphs were identified. The thermal behavior of the polymorphic forms of cellulose-d was also evaluated, and cellulose II exhibited the poorest thermal stability and a unique exothermic reaction.