•Calculate the wear depth of high-speed gears using the Archard's equation.•Establish the dynamic model of a gearbox with wear and tooth contact temperature.•Analyze the effects of contact ...temperature and comprehensive transmission error.•Study dynamic wear characteristics of high-speed gears considering contact temperature.
This paper aims to reveal the relationship between the high-speed gear wear and nonlinear dynamics for a wind turbine gearbox considering the tooth contact temperature. The temperature and deformation of the tooth surface are calculated respectively using the Blok's flash temperature theory and thermal deformation formula, and the meshing stiffness caused by the tooth contact temperature is obtained using the Hertz theory. The wear depth and time-varying meshing stiffness of high-speed gears are calculated using the Archard's equation and potential energy method, respectively. The nonlinear dynamic model of the gearbox is established to study the characteristics, and the frequency domain values of gear wear are compared with experimental data. The results show that the tooth contact temperature makes the time-varying meshing stiffness decrease, then affecting the dynamics of the system, the stability decreases with the increase of comprehensive transmission error, and for the gearbox considering the contact temperature, the gear wear makes the chaotic motion occur in advance and its region increase obviously. The research provides a basis for the wear fault diagnosis and detection of gear transmission systems.
•Analytical expressions for the parameters ε0, T0 and the corresponding uncertainties of measurements are obtained by three methods: (1) Wien approximation, (2) hybrid method with Fisher estimation, ...(3) hybrid method with covariance matrix calculation.•It is shown that the measurement uncertainties obtained by calculating the covariance matrix are practically identical to the results of the Fisher estimate for the hybrid method.•A significant difference was found in the values of the measurement uncertainties obtained by the Wien method and the hybrid method. At low temperatures, T < 2000 K, the Wien approximation gives the worst result, especially for the emissivity when using a spectrometer operating in the visible range. Large relative error values ΔT/T and huge values Δ ε/ε at temperatures below 1300 K means that the linearization and the corresponding nonlinear coordinate transformation do not lead to good estimates of T и ε and corresponding measurement uncertainties of ΔT и Δε.•The results of the study make it possible to obtain an optimal strategy for determining temperature using spectrometric methods, which requires (a) the least number of calculations and (b) gives the least statistical error. The proposed strategy consists of three steps: (1) The temperature of the radiating body is found using the Wien approximation, TW. (2) The resulting TW value is used as an initial approximation for a one-dimensional “hybrid” minimization. The minimization is performed by one of the numerical methods of one-dimensional minimization. As a result, the values of ε0 and T0 can be found. (3) Measurement uncertainties are determined by calculating the covariance matrix. For the chosen confidence level, the confidence bounds of the parameters ε0 and T0 are found using formula.
The aim of this report is the analysis of the uncertainties of non-contact measurement of temperature and emissivity determined by the least sum of squares (LSS) method. Analytical expressions are obtained for the uncertainties of the temperature T and the emissivity ε by three methods: (1) linear regression using the Wien approximation, (2) non-linear regression with covariance matrix calculation using the Planck’s equation, and (3) hybrid method that combines linear and non-linear regression methods. It was found that the better the condition for the Wien’s approximation is fulfilled, the worse the accuracy of the emissivity measurement compared to the accuracy of the temperature measurement. The new optimal strategy is proposed to determine the T and the emissivity ε for non-contact measurements. It consists of three steps: (1) the temperature of the radiating body is found by the Wien approximation, TW; (2) the obtained value TW is used as an initial approximation for one-dimensional “hybrid” minimization. Minimization is carried out by one of the numerical methods of one-dimensional minimization. As a result, the values of ε0 and T0 are found at with the sum of the squared residuals, S0, reaches a minimum; (3) Measurement uncertainties are estimated using the covariance matrix method.
It is important to take contact temperatures into account when developing friction and wear tests for potential tribomaterials and when analyzing the results of those tests. This paper presents some ...of the most useful analytical and numerical methods that can be used to predict surface temperature rises in dry or boundary lubricated pin-on-disk tribotests. The objective is the development of relatively simple, accurate, and easy-to-use expressions that can be used to predict contact temperatures in pin-on-disk sliding contacts. Results of the methods are compared for several different cases, and experimental verification of the predictions are also presented. The resulting expressions are applied to investigate wear of a ceramic (zirconia), metal (stainless steel) and polymer (polyethylene) in pin-on-disk tests.
•Simplified equations are developed for contact temperature estimation in pin-on-disk testers.•Results compare well with contact temperatures determined by finite element analysis.•Results clarify wear transitions for intermetallic pins against metallic and ceramic disks.•Contact temperatures are used in planning accelerated pin-on-disk tests of polymer pins.
The KYb(MoO4)2: Er3+, Y3+ phosphors were synthesized by high temperature solid state reaction method. By further doping Y3+ ions, the near-infrared (NIR, 804 nm, 4I9/2 → 4I15/2) luminescence of ...KYb(MoO4)2: 0.1 % Er3+ phosphor is greatly enhanced. Based on the upconversion luminescence (UCL) spectra, the optimal doping concentration of Y3+ ions were 7.5 %. Its near-infrared UCL intensity is about 26.9 times that of undoped Y3+ ions. Through a series of characterization methods, we find that the enhancement of NIR upconversion emission is due to the generation of defect bands. It plays a crucial role in facilitating the transfer of energy from green light level (2H11/2, 4S3/2) to red light level (4F9/2) and near-infrared level. To explain the luminescence mechanism, the power dependence, UV-VI-NIR absorption spectra, excitation spectra at 804 nm and emission spectra at 380 nm were studied. In addition, the 804 nm single near-infrared UCL intensity of KYb (MoO4)2: Er3+, Y3+ shows a linear variation with temperature in the temperature range of 298 K–673 K. The maximum sensitivity is 0.13 % K−1. This study provides a new method and theoretical support for the application of near-infrared UCL in optical temperature measurement.
The friction heat generated at the wheel-shoe interface during tread braking operations leads to a temperature rise of the wheel tread surface. Fast cooling as well as residual thermal stresses and ...strains can cause damages to the wheel surface, thus negatively affecting the vehicle dynamic behaviour and strongly reducing the wheel life. Modelling the thermo-mechanical interaction of the wheel-block pair is thus of paramount importance to improve the reliability of braking manoeuvres. The paper shows the development of a decoupled thermo-mechanical model and its implementation in ANSYS Mechanical APDL, which can compute the contact pressure at the wheel-shoe interface and the resulting wheel temperature field produced during braking operations, considering friction heating, air convection cooling and the rail chill effect.
•Presentation of a finite element model simulating the wheel-block interaction.•The mechanical and thermal problems are decoupled to speed up the computation.•Tangential stresses are considered to calculate the normal contact pressure.•1Bg and 2Bg brake block configurations are compared in a drag braking operation.•The 1Bg arrangement is more critical from the thermal point of view.
Phosphor thermometry has been viewed as a promising method for non-contact temperature measurement. This article explores the temperature dependence of the Dy-doped phosphors: YAG: Dy, Al2O3:Dy, and ...Y2SiO5:Dy. The phosphors were energized at 355nm from a 3rd-harmonic-generation Nd:YAG laser. The intensity of YAG:Dy was much stronger than the other phosphors, and the I458nm/I497nm intensity ratios had high temperature resolution over a wide range of temperatures. Although Al2O3:Dy and Y2SiO5:Dy had weaker intensity, the temperature resolution of intensity ratios was as substantial as YAG:Dy. The uncertainty in measured temperature of Dy-doped phosphors was evaluated using linearized error propagation theory, based on the noise-to-signal ratio and temperature sensitivity, revealing that the measurement uncertainty of YAG:Dy was less than the other two phosphors, and thus was the most reliable thermographic phosphor. In addition, the optimization of the bandpass filter combination was explored at each temperature range with YAG:Dy phosphor. Consequently, each temperature can be precisely measured by dividing the integrated intensity between 441 and 475nm as a counter peak range and 476–500nm as a main peak range. Thus, ideal bandpass filters are relatively constant throughout all temperatures.
This paper proposes a thermal network model to predict the contact temperature of spur gears. A crucial parameter in gear scuffing evaluation is the contact temperature, which comprises the bulk and ...flash temperatures. Herein, thermal network models of gear bulk temperature and flash temperature are established, by dispersing tooth into multiple temperature elements connected by the thermal resistances of heat conduction and heat convection. The thermal network model of gear bulk temperature is verified by the finite element model and previous work, and the presented model for gear flash temperature is validated by Blok flash temperature formula. Following ISO standard, gear scuffing is evaluated by comparing the contact temperature with scuffing critical temperature. The effects of geometric and operating parameters on the gear temperature are subsequently investigated. Contact temperature is found to decrease with increased tooth width, pressure angle and module, but increases with increased rotational velocity and input torque. These findings indicate that reasonable geometric and operating parameter matching are beneficial for increasing gear-scuffing resistance.
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•A novel thermal network model for predicting the contact temperature of spur gears is proposed.•The gear bulk and flash temperature models are respectively established and verified.•A method of dispersing gear into multiple temperature elements is presented.•The reasonable geometrical and operating parameters matching is found to improve gear scuffing resistance.
Under high-temperature, high-speed, heavy-duty, and extreme lubrication operating conditions, such as those found in gearboxes of aviation engines and electric vehicles, gear scuffing failure has ...emerged as a critical issue and a primary technical challenge in the mechanical transmission field. As test methodologies, evaluation criteria, and load-carrying capacities related to gear scuffing are yet to reach full maturity in response to these demanding operating environments, this article examines existing literature on gear scuffing failure and its control, incorporating insights from industry practices and academic studies. The discussion encompasses the development of gear scuffing theories, experimental investigations, and practical applications, ultimately providing an overview of the most recent developments in gear anti-scuffing technologies. The ultimate goal of this work is to elucidate failure mechanisms of gear scuffing and establish effective design approaches for gear anti-scuffing.
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New lanthanide-doped nanoparticles with unique optical characterisics are highly desirable for non-contact thermal sensing and advanced optical anticounterfeiting. The fluorescence ...intensity ratio (FIR) nanothermometers with higher relative temperature sensitivity (Sr) offer several advantages over traditional contact-based temperature sensors, including high sensitivity, fast response times, and non-invasive measurement. Herein, we describe the synthesis of nanocrystalline SrMoO4:RE3+ (RE3+= Tb3+ and Eu3+) using co-precipitation method for various optical applications, such as temperature sensing and anti-counterfeiting. These phosphors nanoparticle emit multi-colors by varying the percentage of Eu3+ and Tb3+ ions incorporated into SrMoO4. The maximum absolute sensitivity for multi-mode non-contact temperature measurement based on FIR and the distinct thermal behaviour of Eu3+ and Tb3+ ions was reached at 0.055 K−1. The maximum relative sensitivity is reached at 1.8 % K−1, with a minimum temperature resolution δT of 0.043 K at 300 K and maximum δT of 0.272 K. The developed nanophosphors emit green light when it doped Tb3+ and emit red light when it doped with Eu3+, and both demonstrate distinct changes in their response to temperature variations. The color change with temperature elucidates a real base for potential application in advanced anti-counterfeiting. The co-precipitation method we used to synthesize the nanophosphors is easy to scale up for industrial applications. So, the developed nanophosphors with multicolor emissions is of scientific and technological relevence.
