CHALLENGES AND METHODS IN ANALYZES OF THE HEAT TRANSFER IN POLYMER DRY BEARINGS

Tribologia ◽  
2018 ◽  
Vol 282 (6) ◽  
pp. 71-78
Author(s):  
Krzysztof KASZA ◽  
Łukasz MATYSIAK ◽  
Artur KRÓL
Keyword(s):  
Numerical Model ◽  
Measurement Errors ◽  
Temperature Sensors ◽  
Temperature Gradients ◽  
Maximum Temperature ◽  
Large Temperature ◽  
Internal Temperature ◽  
Require Temperature ◽  
Polymer Bearing ◽  
Load Conditions

Heat generation and dissipation in dry polymer bearings are important aspects in their design and operation, because the overheating may lead to fast wear or product damage. The estimation of the maximum temperature under defined load conditions is crucial, but it is also a challenging task. Firstly, it is difficult to measure temperature directly at the contact surface between the bearing and the shaft. Secondly, thermocouples that are commonly used as the temperature sensors might create measurement errors. The work presented in this paper utilizes the numerical model of a polymer bearing for the analysis of the internal temperature field. The model is validated with use of experimental data; and, in order to mitigate the measurement errors of the thermocouple sensor, their geometry and properties are included in the simulation model. The achieved agreement between simulation and experimental temperatures is 10% on average, and it is judged that the numerical model may be applied for thermal analysis of the polymer bearing. The obtained results confirm the influence of the thermocouples with metallic sheaths on the temperature distribution inside the tested polymer bearing. It is shown that the value of the measurement errors depends on the layout of thermocouples and might be significantly reduced by their proper arrangement. It is believed that the presented approach for the analysis of thermal performance of dry polymer bearings might be applied to similar cases, which are characterized by large temperature gradients and require temperature sensors, that are made of the materials of high thermal conductivity.

Role of substrate shape on thermal energy transmission in robotized wire and arc additive manufacturing

2019 ◽  
Vol 25 (7) ◽  
pp. 1285-1294 ◽  
Author(s):  
Rong Li ◽  
Jun Xiong
Keyword(s):  
Additive Manufacturing ◽  
Temperature Gradient ◽  
Thermal Energy ◽  
Molten Pool ◽  
Temperature Gradients ◽  
Maximum Temperature ◽  
Large Temperature ◽  
Energy Transmission ◽  
Content Type ◽  
Thin Walled

Purpose The purpose of this study is to present how the thermal energy transmission of circular parts produced in robotized gas metal arc (GMA)-based additive manufacturing was affected by the substrate shape through finite element analysis, including distributions of thermal energy and temperature gradient in the molten pool and deposited layers. Design/methodology/approach Three geometric shapes, namely, square, rectangle and round were chosen in simulation, and validation tests were carried out by corresponding experiments. Findings The thermal energy conduction ability of the deposited layers is the best on the round substrate and the worst on the rectangular substrate. The axial maximum temperature gradients in the molten pool along the deposition path with the round substrate are the largest during the deposition process. At the deposition ending moment, the circumferential temperature gradients of all layers with the round substrate are the largest. A large temperature gradient usually stands for a good heat conduction condition. Altogether, the round substrate is more suitable for the fabrication of circular thin-walled parts. Originality/value The predicted thermal distributions of the circular thin-walled part with various substrate shapes are helpful to understand the influence of substrate shape on the thermal energy transmission behavior in GMA-based additive manufacturing.

A Constitutive Model for Commercially Pure Titanium

1995 ◽  
Vol 117 (2) ◽  
pp. 139-144 ◽  
Author(s):  
J. Y. Sheikh-Ahmad ◽  
J. A. Bailey
Keyword(s):  
Shear Strain ◽  
Temperature Rise ◽  
Pure Titanium ◽  
Torsion Test ◽  
Temperature Gradients ◽  
Maximum Temperature ◽  
Large Temperature ◽  
Strain Rates ◽  
Commercially Pure Titanium ◽  
Deformation Heating

Flow stress data for CP titanium were obtained using the torsion test in the temperature range from ambient to 750°C and at shear strain-rates in the range from 0.192 to 122.0 s−1. The temperature rise because of deformation heating was calculated numerically. It was found that the temperature rise is insignificant for strain rates below 0.192 s−1 where the deformation conditions are essentially isothermal while for strain rates above 27.0 s−1 deformation conditions are adiabatic. Large temperature gradients exist in the longitudinal direction of the specimen with the maximum temperature occurring at the middle of the gage length. The temperature gradients in the radial direction are much smaller and can be neglected for most practical applications. Isothermal shear stress-shear strain curves for CP titanium were obtained from the experimental torsion test data by accounting for the temperature rise produced by deformation. It was found that the data exhibits a good fit to a Johnson-Cook relationship with exponential thermal softening. The work emphasizes the importance of the need to consider the role of deformation heating when interpreting data on the effect of strain rate and temperature on the mechanical properties of materials.

scholarly journals Thermoregulation in colonies of africanized and hybrids with Caucasian, Italian and Carniolan Apis mellifera honey bees

1999 ◽  
Vol 42 (4) ◽  
Author(s):  
Vagner de Alencar Arnaut de Toledo ◽  
Regina Helena Nogueira-Couto
Keyword(s):  
Apis Mellifera ◽  
Honey Bees ◽  
Maximum Temperature ◽  
Tropical Region ◽  
Internal Temperature ◽  
Africanized Honey Bees ◽  
Significant Difference ◽  
The Mean ◽  
One Year ◽  
Brood Nest

This experiment was carried out to study the internal temperature regulation of a colony of Africanized honey bees (AFR), compared with hybrid Caucasian (CAU), Italian (ITA), and Carniolan (CAR) bees, during the period of one year and different size hives located in a sub-tropical region. The instant internal temperature, 33.7 ± 1.5° C for the AFR, 33.5 ± 1.4° C for the CAU, 33.7 ± 1.5° C for the ITA and 33.8 ± 1.4° C for the CAR, did not show any significant difference (P>0.05). The maximum temperature (36.1 ± 2.3° C) was statistically different (P<0.05) from the minimum (27.6 ± 5.3° C). There was no difference (P>0.05) in the mean internal temperature, between the nucleus (31.7 ± 6.3° C) and the brood nest (32.1 ± 5.3° C) measured between two and four o'clock in the afternoon.

Design and Fabrication of a Magnetocaloric Microcooler

2005 ◽  
Author(s):  
Sangchae Kim ◽  
Bharath Bethala ◽  
Simone Ghirlanda ◽  
Senthil N. Sambandam ◽  
Shekhar Bhansali
Keyword(s):  
Magnetic Field ◽  
Ambient Temperature ◽  
Temperature Change ◽  
Entropy Change ◽  
Temperature Sensors ◽  
Experimental Results ◽  
Maximum Temperature ◽  
Alternative Technology ◽  
Temperature Conditions ◽  
Si Wafer

Magnetocaloric refrigeration is increasingly being explored as an alternative technology for cooling. This paper presents the design and fabrication of a micromachined magnetocaloric cooler. The cooler consists of fluidic microchannels (in a Si wafer), diffused temperature sensors, and a Gd5(Si2Ge2) magnetocaloric refrigeration element. A magnetic field of 1.5 T is applied using an electromagnet to change the entropy of the magnetocaloric element for different ambient temperature conditions ranging from 258 K to 280 K, and the results are discussed. The tests show a maximum temperature change of 7 K on the magnetocaloric element at 258 K. The experimental results co-relate well with the entropy change of the material.

Optimization of the Case Depth of a Cylinder Made With 4340 Steel by a Control of the Laser Heat Treatment Parameters

2018 ◽  
Author(s):  
Rachid Fakir ◽  
Noureddine Barka ◽  
Jean Brousseau
Keyword(s):  
Heat Treatment ◽  
Numerical Model ◽  
Surface Temperature ◽  
Laser Power ◽  
Case Depth ◽  
Maximum Temperature ◽  
Laser Heat Treatment ◽  
Laser Heat ◽  
4340 Steel ◽  
Cylindrical Workpiece

This paper presents a numerical model able to control the temperature distribution along a 4340 steel cylinder heat-treated with Nd: YAG laser. The numerical model developed using the numerical finite element method, was based on a study of surface temperature variation and the adjustment of this temperature by a control of the heat treatment laser power. The proposed analytical approach was built gradually by (i) the development of a numerical model of laser heat treatment of the cylindrical workpiece, (ii) an analysis of the results of simulations and experimental tests, (iii) development of a laser power adjustment approach, and (iv) proposal of a laser power control predictor using neural networks. This approach was made possible by highlighting the influence of the fixed (non-variable) parameters of the laser heat treatment on the case depth, and has shown that it is possible by controlling the laser parameters to homogenize the distribution of the maximum temperature reached on the surface for a uniform case depth. The feasibility and effectiveness of the proposed approach leads to a reliable and accurate model able to guarantee a uniform surface temperature and a regular case depth for a cylindrical workpiece of a length of 50-mm and with a diameter of between 16-mm and 22-mm.

scholarly journals The impact of the air temperature on measuring the zenith angle during the year in the ground layer of the atmosphere for the needs of engineering surveying

2021 ◽  
Vol 61 (3) ◽  
pp. 476-488
Author(s):  
Tomáš Suk ◽  
Martin Štroner
Keyword(s):  
Czech Republic ◽  
Numerical Model ◽  
Central Europe ◽  
Air Temperature ◽  
Zenith Angle ◽  
Geographical Area ◽  
Temperature Gradients ◽  
The Czech Republic ◽  
Different Seasons ◽  
The Impact

This paper presents the results of over a year-long experiment dealing with a temperature measurement to calculate the theoretical effect of the atmosphere on the measured zenith angle in engineering surveying. The measurements were performed to determine the accurate and specific temperatures (temperature gradients), which can be recorded in different seasons in the low level of the atmosphere (up to 2 m above the ground, where most Engineering Surveying measurements take place) for the geographical area of Central Europe - specifically the Czech Republic. A numerical model was then applied to the resulting determined temperature gradients to calculate the path of the beam passing through an inhomogeneous atmosphere. From these values, the apparent vertical shifts caused by refraction in a given environment and time were finally determined.

scholarly journals A Computer Programme With Temperature Gradient Capability for the Network Analysis of Hybrid Circuits

1980 ◽  
Vol 6 (3-4) ◽  
pp. 227-229
Author(s):  
Carl R. Zimmer
Keyword(s):  
Thermal Analysis ◽  
Input Data ◽  
Steady State Solution ◽  
Temperature Gradients ◽  
Large Temperature ◽  
Computer Programme ◽  
System Operation ◽  
Linear Network ◽  
Periodic Inputs ◽  
Additional Option

A modified version of the computer programme SINC-S is described which permits the user to specify independently up to 30 different device temperatures in a given problem when the proper control statement is included. An additional option is an algorithm for the steady-state solution of a non-linear network with periodic inputs, so that realistic system operation may be simulated. The programme may be used to provide more accurate simulation of circuits where large temperature gradients are present, and to furnish input data for other thermal analysis programmes

Maximum Condensable Pressure in a Sealed Container With Arbitrary Temperature Distribution

2020 ◽  
Author(s):  
J. I. Watjen ◽  
M. T. Schifano ◽  
M. N. Sexton
Keyword(s):  
Temperature Distribution ◽  
Internal Pressure ◽  
Strong Relationship ◽  
Pressure Vessels ◽  
Large Temperature ◽  
Internal Temperature ◽  
Seal Integrity ◽  
Arbitrary Temperature ◽  
Vapor Mixtures ◽  
Saturated Boiling

Abstract Pressure vessels and sealed canisters are designed to maintain seal integrity under a maximum internal pressure. When the temperature inside the canister rises, the internal pressure rises accordingly. The presence of condensable liquid-vapor mixtures can create a strong relationship between the pressure and temperature. An isothermal container admits a straightforward thermodynamic pressure calculation; however, large temperature gradients inside the container require complex multiphase conjugate heat transfer calculations to predict accurate pressures. A simplified prediction using the peak internal temperature to find the saturated pressure of the condensable fluid may introduce unrealistic pressures when significant fluid mass exists in a cooler location of the container. This work presents methodology to calculate the pressure of a condensable fluid in a sealed container with large internal temperature differences using a two-temperature approach to predict saturated boiling and superheating of the vapor phase. An arbitrary temperature distribution allows for pressure calculations by considering the expected location of the liquid mass and the peak internal temperature. An enthalpy balance provides the effects of the temperature distribution and the peak pressure condition is easily predicted using the proposed method. This work provides a means to calculate the maximum internal pressure of a sealed container with a condensable fluid without the need for complex multiphase computer modeling.

METHOD FOR IMPROVING THE ACCURACY OF MEASURING INPUT SIGNALS IN A MICROCONTROLLER CONTROL UNIT

2021 ◽  
pp. 82-86
Author(s):  
Р.Ю. Кузьменко ◽  
И.И. Таболин ◽  
А.О. Тищенко ◽  
А.Д. Данилов
Keyword(s):  
Total Error ◽  
Control Unit ◽  
Temperature Sensors ◽  
Temperature Error ◽  
Maximum Temperature ◽  
Practical Implementation ◽  
Analog To Digital Converter ◽  
Digital Converter ◽  
Analog To Digital ◽  
Software Compensation

Приводится методика программно-аппаратного способа компенсации теплового дрейфа напряжения, возникающего в измерительных каналах резистивных датчиков давления и температуры в блоке управления зарядно-разрядным устройством никель-водородной аккумуляторной батареи. Рассмотрена проблема повышения точности и надежности измерения контролируемых параметров для более точного управления режимами батареи в системе энергоснабжения при колебаниях температуры окружающей среды. Показана функциональная схема тракта преобразования аналогового сигнала в цифровую форму с использованием встроенного аналого-цифрового преобразователя микроконтроллера. Приведены экспериментальные данные исследований влияния температуры на точность измерения сигналов, а также графические иллюстрации максимальной приведенной погрешности 40 каналов измерения. Исследован разброс характеристик температурных датчиков, реализованных в кристаллах нескольких микроконтроллеров. На основании полученных данных выявлены узлы и элементы, вносящие максимальную температурную погрешность в каналы измерения датчиков давления и температуры аккумуляторной батареи. Разработана методика для программно-аппаратной компенсации температурной погрешности преобразования сигналов датчиков. Описаны алгоритм и условия практической реализации метода компенсации суммарной погрешности канала измерения с использованием аналого-цифрового преобразователя микроконтроллера. Проведена экспериментальная оценка примененного метода расчета в узле формирования телеметрии управления блока электроники, предназначенного для преобразования аналоговых сигналов с датчиков давления и температуры в цифровой код The article presents the method of hardware-software compensation of thermal voltage drift in the measuring channels of resistive pressure and temperature sensors in the control unit of the charging and discharging device of a nickel-hydrogen battery. We considered the problem of increasing the accuracy and reliability of the measurement of controlled parameters for more precise control of the operating modes of the batteries in the power supply system when the ambient temperature changes. We show the functional diagram of the path for converting an analog signal into a digital form using the built-in analog-to-digital converter of the microcontroller. We present experimental data on the influence of temperature on the accuracy of signal measurement, as well as graphic illustrations of the maximum reduced error of 40 measuring channels. We investigated the spread of the characteristics of temperature sensors implemented in the crystals of several microcontrollers. Based on the obtained data, we determined the nodes and elements that make up the maximum temperature error in the measurement channels of the pressure and temperature sensors of the battery. We developed a method of hardware-software compensation of the temperature error of the sensor signal conversion. Here we describe the algorithm and conditions of practical implementation of the method of compensation of the total error of the measuring channel using the analog-to-digital converter of the microcontroller. We carried out an experimental evaluation of the applied calculation method in the telemetry generation unit of the electronics unit designed to convert analog signals of pressure and temperature sensors into a digital code

scholarly journals Textile-Integrated Thermocouples for Temperature Measurement

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 626 ◽  
Author(s):  
Waleri Root ◽  
Thomas Bechtold ◽  
Tung Pham
Keyword(s):  
Output Signal ◽  
Temperature Sensors ◽  
Temperature Sensing ◽  
Temperature Gradients ◽  
Thermoelectric Effects ◽  
Support Materials ◽  
Conductive Materials ◽  
Voltage Output ◽  
Cold Junction ◽  
Polymeric Carbon

The integration of conductive materials in textiles is key for detecting temperature in the wearer´s environment. When integrating sensors into textiles, properties such as their flexibility, handle, and stretch must stay unaffected by the functionalization. Conductive materials are difficult to integrate into textiles, since wires are stiff, and coatings show low adhesion. This work shows that various substrates such as cotton, cellulose, polymeric, carbon, and optical fiber-based textiles are used as support materials for temperature sensors. Suitable measurement principles for use in textiles are based on resistance changes, optical interferences (fiber Bragg grating), or thermoelectric effects. This review deals with developments in the construction of temperature sensors and the production of thermocouples for use in textiles. The operating principle of thermocouples is based on temperature gradients building up between a heated and a cold junction of two conductors, which is converted to a voltage output signal. This work also summarizes integration methods for thermocouples and other temperature-sensing techniques as well as the manufacture of conductive materials in textiles. In addition, textile thermocouples are emphasized as suitable and indispensable elements in sensor concepts for smart textiles.

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