scholarly journals Temperature-dependent thermo-elastic parameter identification for composites using thermal modal data

2019 ◽  
Vol 11 (10) ◽  
pp. 168781401988416 ◽  
Author(s):  
Dong Jiang ◽  
Yu Xu ◽  
Donghui Zhu ◽  
Zhifu Cao
Keyword(s):  
Temperature Distribution ◽  
Parameter Identification ◽  
High Sensitivity ◽  
Relative Sensitivity ◽  
Elastic Parameter ◽  
Temperature Perturbation ◽  
Temperature Dependent ◽  
Elastic Parameters ◽  
Modal Data ◽  
Thermal Expansion Coefficients

To accurately determine the temperature-dependent parameters of composites, a thermo-elastic parameter identification approach using thermal modal data is proposed in this article. The investigation is based on two hypotheses: (1) the structure is at steady-state temperature field, which means the temperature distribution is time independent; (2) temperature distribution can be determined in advance of thermo-elastic parameter identification, and thermal-related large deformation is not considered. The thermal-dependent elastic constants and thermal expansion coefficients are expressed as intermediate functions with the independent variable of temperature, perturbation method is adapted to calculate the sensitivity of thermal modal frequencies with respect to the intermediate variables, and variables with high sensitivity are selected as the identifying parameters. By constructing the intermediate function and calculating the relative sensitivity, thermo-elastic parameters are identified by minimizing the residual between experimental and analytical natural frequencies under thermal circumstance. Two different types of composite models are employed to verify the strategies of parameter identification. Results show that on the basis of the intermediate function, the proposed approach can be applied to identify the thermo-elastic parameters effectively.

Electrothermal analysis of integrated circuits: a realization by infrared thermography

2021 ◽  
Author(s):  
Farnoos Farrokhi
Keyword(s):  
Temperature Distribution ◽  
Integrated Circuits ◽  
Power Dissipation ◽  
Electronic Device ◽  
Power Measurement ◽  
Device Under Test ◽  
Distribution Analysis ◽  
Ir Thermography ◽  
Temperature Dependent ◽  
Run Time

The International Technology Roadmap for Silicon (ITRS) predicted that by the year 2016, a high-performance chip could dissipate as much as 300 W/cm² of heat. Another more noticeable thermal issue in IC's is the uneven temperature distribution. Increased power dissipation and greater temperature variation highlight the need for electrothermal analysis of electronic components. The goal of this research is to develop an experimental infrared measurement technique for the thermal and electrothermal analysis of electronic circuits. The objective of the electrothermal analysis is to represent the behavior of the temperature dependent characteristics of electronic device in near real work condition. An infrared (IR) thermography setup to perform the temperature distribution analysis and power dissipation measurement of the device under test is proposed in this reasearch. The system is based on a transparent oil heatsink which captures the thermal profile and run-time power dissipation from the device under test with a very fine degree of granularity. The proposed setup is used to perform the thermal analysis and power measurement of an Intel Dual Core E2180 processor. The power dissipation of the processor is obtained by calculating and measuring the heat transfer coefficient of the oil heatsink. Moreover, the power consumption of the processor is measured by isolating the current used by the CPU at run time. A three-dimensional fininte element thermal model is developed to simulate the thermal properties of the processor. The results obtained using this simulation is compared to the experimental results from IR thermography. A methodology to perform electrothermal analysis on integrated circuits is introduced. This method is based on coupling a standard electrical simulator, which is often used in the design process, and IR thermography system through an efficient interface program. The proposed method is capable of updating the temperature dependent parameters of device in near real time. The proposed method is applied to perform electrothermal analysis of a power MOSFET to measure the temperature distribution and the device performance. The DC characteristics of the device are investigated. The obtained results indicated that the operating point, I-V characteristics and power dissipation of the MOSFET vary significantly with temperature.

scholarly journals A Highly Sensitive, Polarization Maintaining Photonic Crystal Fiber Sensor Operating in the THz Regime

Photonics ◽  
2018 ◽  
Vol 5 (4) ◽  
pp. 40 ◽  
Author(s):  
Sohel Rana ◽  
Nirmala Kandadai ◽  
Harish Subbaraman
Keyword(s):  
Photonic Crystal ◽  
Photonic Crystal Fiber ◽  
High Sensitivity ◽  
Relative Sensitivity ◽  
Computational Technique ◽  
The Finite Element Method ◽  
High Birefringence ◽  
Crystal Fiber ◽  
Highly Sensitive ◽  
Imaging And Spectroscopy

In this paper, a high sensitivity, polarization preserving photonic crystal fiber (PCF), based on circular air holes for sensing in the terahertz (THz) band, is presented. The finite element method, a practical and precise computational technique for describing the interactions between light and matter, is used to compute the modal properties of the designed fiber. For the designed PCF, comprising of circular air holes in both the cladding and in the porous core, a relative sensitivity of 73.5% and a high birefringence of 0.013 are achieved at 1.6 THz. The all circular air-hole structure, owing to its simplicity and compatibility with the current fiber draw technique for PCF fabrication, can be realized practically. It is anticipated that the designed fiber can be employed in applications such as detection of biological samples and toxic chemicals, imaging, and spectroscopy.

scholarly journals Temperature-dependent structural behaviour of samarium cobalt oxide

2017 ◽  
Vol 32 (S2) ◽  
pp. S38-S42
Author(s):  
Matthew R. Rowles ◽  
Cheng-Cheng Wang ◽  
Kongfa Chen ◽  
Na Li ◽  
Shuai He ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Cobalt Oxide ◽  
Sol Gel ◽  
Linear Thermal Expansion ◽  
Rietveld Analysis ◽  
Structural Behaviour ◽  
Temperature Dependent ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients ◽  
Sol Gel Synthesis

The crystal structure and thermal expansion of the perovskite samarium cobalt oxide (SmCoO3) have been determined over the temperature range 295–1245 K by Rietveld analysis of X-ray powder diffraction data. Polycrystalline samples were prepared by a sol–gel synthesis route followed by high-temperature calcination in air. SmCoO3 is orthorhombic (Pnma) at all temperatures and is isostructural with GdFeO3. The structure was refined as a distortion mode of a parent $ Pm{\bar 3}m $ structure. The thermal expansion was found to be non-linear and anisotropic, with maximum average linear thermal expansion coefficients of 34.0(3) × 10−6, 24.05(17) × 10−6, and 24.10(18) × 10−6 K−1 along the a-, b-, and c-axes, respectively, between 814 and 875 K.

scholarly journals Multifunctional Textile Platform for Fiber Optic Wearable Temperature-Monitoring Application

Micromachines ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 866 ◽  
Author(s):  
Ziyang Xiang ◽  
Liuwei Wan ◽  
Zidan Gong ◽  
Zhuxin Zhou ◽  
Zhengyi Ma ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Temperature Sensor ◽  
High Sensitivity ◽  
Wavelength Shift ◽  
Heat Sources ◽  
Time Dynamic ◽  
Textile Sensor ◽  
Fbg Sensors ◽  
Comfort Parameters ◽  
Monitoring Application

Wearable sensing technologies have been developed rapidly in the last decades for physiological and biomechanical signal monitoring. Much attention has been paid to functions of wearable applications, but comfort parameters have been overlooked. This research presents a developed fabric temperature sensor by adopting fiber Bragg grating (FBG) sensors and processing via a textile platform. This FBG-based quasi-distributed sensing system demonstrated a sensitivity of 10.61 ± 0.08 pm/°C with high stability in various temperature environments. No obvious wavelength shift occurred under the curvatures varying from 0 to 50.48 m−1 and in different integration methods with textiles. The temperature distribution monitored by the developed textile sensor in a complex environment with multiple heat sources was deduced using MATLAB to present a real-time dynamic temperature distribution in the wearing environment. This novel fabric temperature sensor shows high sensitivity, stability, and usability with comfort textile properties that are of great potential in wearable applications.

Die Spektralsensitivität von Insekten-Komplexaugen im Ultraviolett bis 290 mμ

1959 ◽  
Vol 14 (4) ◽  
pp. 273-278 ◽  
Author(s):  
Jost Bernhard Walther ◽  
Eberhard Dodt
Keyword(s):  
Ultraviolet Light ◽  
Periplaneta Americana ◽  
Light Adaptation ◽  
Compound Eye ◽  
Monochromatic Light ◽  
High Sensitivity ◽  
Relative Sensitivity ◽  
Calliphora Erythrocephala ◽  
Sensitivity Curves ◽  
Fly Eye

Behaviour experiments have shown that insects react to ultraviolet light. Almost no data are available within this spectral range, however, on the sensitivity of their light sense organs.In this investigation the relative spectral sensitivity (1/Q) of the compound eye of the fly, Calliphora erythrocephala, and various areas of the compound eye of the cockroach, Periplaneta americana, was measured including the ultraviolet range down to 290 mμ. Equal amplitudes of the electroretinogram indicated equal efficiencies of the stimuli.The sensitivity curve in both species shows, besides the known maximum in the blue green, a second maximum in the ultraviolet. This second maximum was found between 341-369 mμ depending on the species and the particular area of the eye. At still shorter wave lengths sensitivity decreases. In the fly eye and the upper part of the cockroach eye the sensitivity maximum in the ultraviolet is higher than in the bluegreen, whereas in the ventral part of the cockroch eye it is lower. Monochromatic light adaptation selectively influences the relative sensitivity of the upper part of the cockroach eye.The sensitivity curves are discussed with regard to visual pigments and types of receptors. Fluorescence of the eye media is considered to have only negligible if any influence on the high sensitivity for ultraviolet light.

Electromagnetic and thermal parameter identification method for best prediction of temperature distribution on transformer tank covers

2015 ◽  
Vol 34 (2) ◽  
pp. 485-495 ◽  
Author(s):  
Patricia Penabad Durán ◽  
Paolo Di Barba ◽  
Xose Lopez-Fernandez ◽  
Janusz Turowski
Keyword(s):  
Temperature Distribution ◽  
Measurement Error ◽  
Parameter Identification ◽  
Objective Function ◽  
Measurement Errors ◽  
Optimization Algorithms ◽  
Identification Problem ◽  
Content Type ◽  
Identification Method ◽  
Wide Range

Purpose – The purpose of this paper is to describe a parameter identification method based on multiobjective (MO) deterministic and non-deterministic optimization algorithms to compute the temperature distribution on transformer tank covers. Design/methodology/approach – The strategy for implementing the parameter identification process consists of three main steps. The first step is to define the most appropriate objective function and the identification problem is solved for the chosen parameters using single-objective (SO) optimization algorithms. Then sensitivity to measurement error of the computational model is assessed and finally it is included as an additional objective function, making the identification problem a MO one. Findings – Computations with identified/optimal parameters yield accurate results for a wide range of current values and different conductor arrangements. From the numerical solution of the temperature field, decisions on dimensions and materials can be taken to avoid overheating on transformer covers. Research limitations/implications – The accuracy of the model depends on its parameters, such as heat exchange coefficients and material properties, which are difficult to determine from formulae or from the literature. Thus the goal of the presented technique is to achieve the best possible agreement between measured and numerically calculated temperature values. Originality/value – Differing from previous works found in the literature, sensitivity to measurement error is considered in the parameter identification technique as an additional objective function. Thus, solutions less sensitive to measurement errors at the expenses of a degradation in accuracy are identified by means of MO optimization algorithms.

Coupled Electro-Thermal Mechanical Analyses for SMM Actuators Development

2004 ◽  
Author(s):  
C. Channy Wong ◽  
Randy R. Lober ◽  
Jason D. Hales
Keyword(s):  
Electrical Resistivity ◽  
Temperature Distribution ◽  
Joule Heating ◽  
Temperature Dependent ◽  
Strongly Coupled ◽  
Mechanical Responses ◽  
Thermal Actuators ◽  
Micro Actuators ◽  
And Performance

A coupled-physics analysis code has been developed to simulate the electrical, thermal, and mechanical responses of surface micromachined (SMM) actuators. Our objective is to optimize the design and performance of these micro actuators. Since many new designs of these electro-thermal actuators have shuttles or platforms between beams, calculating the local Joule heating requires a multi-dimensional electrostatics analysis. Moreover, the electrical solution is strongly coupled to the temperature distribution since the electrical resistivity is temperature dependent. Thus, it is essential to perform a more comprehensive simulation that solves the coupled electrostatics, thermal, and mechanical equations. Results of the coupled-physics analyses will be presented.

scholarly journals Numerical modelling approach for the temperature dependent forming behaviour of Ti-6Al-4V

2018 ◽  
Vol 190 ◽  
pp. 12004
Author(s):  
Thomas Papke ◽  
Matthias Graser ◽  
Marion Merklein
Keyword(s):  
Elevated Temperature ◽  
Temperature Distribution ◽  
Numerical Modelling ◽  
Tensile Test ◽  
Numerical Simulations ◽  
Numerical Models ◽  
Uniaxial Tensile ◽  
Temperature Dependent ◽  
Inhomogeneous Temperature ◽  
Forming Behaviour

Titanium alloys offer several beneficial characteristics, such as high specific strength, metallurgical stability at elevated temperature, biocompatibility and corrosion resistance. With regard to these superior properties, Ti-6Al-4V is a commonly used titanium alloy for aerospace components and medical products. The production of parts made of Ti-6Al-4V can be done in various ways. One approach is forming at elevated temperature, which requires a focused design of parts, processes and numerical modelling of the forming process. Essential input parameters for the numerical models are temperature dependent material parameters. Since, the yield stress and Young's modulus of the material decrease significantly at elevated temperature, the forming limits are enhanced. For the characterization of the forming behaviour, uniaxial tensile tests at temperatures from 250 °C to 400 °C have been conducted. The samples are heated by conduction in a thermal-mechanical simulator for the tensile test. However, the resulting inhomogeneous temperature distribution along the longitudinal axis of the specimen is a challenge in order to measure proper material properties. Inhomogeneous temperature distribution leads to varying mechanical properties and temperature dependent forming behaviour. To overcome this issue, simple numerical models based on experimental data are necessary, which allow the estimation of the influence of the inhomogeneous temperature distribution. In this paper, therefore, the temperature distribution and the subsequent tensile test are investigated using electrical-thermal and mechanical numerical simulations of the tensile test at elevated temperature. With the combined approach of experimental tests and numerical simulations, the forming behaviour of Ti-6Al-4V can be modelled.

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