Influence of the Material and Thickness of the Specimen on an Infrared Stress Image

2004 ◽  
Vol 261-263 ◽  
pp. 1641-1646
Author(s):  
Kenji Machida ◽  
Mamtimin Gheni
Keyword(s):  
Thermal Conductivity ◽  
Hybrid Method ◽  
Thermal Conduction ◽  
Crack Problem ◽  
High Stress ◽  
High Accuracy ◽  
Problem Analysis ◽  
Principal Stresses ◽  
Distribution Form ◽  
Stress Components

The thickness dependency of the temperature image obtained by an infrared thermography was investigated using specimens with three kinds of materials and four kinds of the thickness of the specimen. Only the sum of the principal stresses which is the first invariant of stress tensor is measured, and it is impossible to measure individual stress components directly. Then, the infrared hybrid method was developed to separate individual stress components. Although the form of the contour line of low stress side differs greatly, the distribution form of high stress side was considerably alike. The stress intensity factor of material with low thermal conductivity can be estimated with high accuracy by the infrared hybrid method. On the crack problem, it was elucidated that the influence of thermal conduction is large and an inverse problem analysis is required.

Evaluation of the J Integral of a Surface Crack by the Three-dimensional Local Hybrid Method

2006 ◽  
Vol 321-323 ◽  
pp. 28-31
Author(s):  
Kenji Machida ◽  
Gaku Mizukami ◽  
Hirohisa Oyama
Keyword(s):  
Stress Field ◽  
Relative Error ◽  
Hybrid Method ◽  
Surface Crack ◽  
Three Dimensional ◽  
High Accuracy ◽  
Problem Analysis ◽  
J Integral ◽  
Uniform Load ◽  
Bending Load

To evaluate the 3-D stress field inside a specimen from displacement data on the free surface obtained from the 2-D intelligent hybrid method, we developed the 3-D local hybrid method based on inverse problem analysis. In a previous study, when a uniform load was applied to a structure with a surface crack, it was demonstrated that the stress field was analyzed with high accuracy. In this study, the 3-D local hybrid method was applied to a structure with a surface crack subjected to bending load. However, a suitable solution was not able to be obtained on a bending problem. Therefore, another method was applied. The relative error between the J integral value of the whole model and the local model was compared, and accuracy was investigated. First, the variation of accuracy with width and thickness was examined. If thickness is increased, the relative error decreases as found in the uniform load case. Moreover, as width increases, the relative error decreases. However, even if width and thickness become large, accuracy does not necessarily become better. Therefore, the relative error was compared and a suitable hybrid size was examined.

Thermal conduction characteristics of silicone composites including ultrasonic-treated graphite

2021 ◽  
pp. 002199832110595
Author(s):  
Weontae Oh ◽  
Jong-Seong Bae ◽  
Hyoung-Seok Moon
Keyword(s):  
Thermal Conductivity ◽  
Ultrasonic Treatment ◽  
Thermal Conduction ◽  
Light Emitting Diode ◽  
Thermal Interface Material ◽  
Ultrasonic Power ◽  
Lighting System ◽  
Thermal Interface ◽  
Light Emitting ◽  
Inorganic Oxides

The microstructural change of graphite was studied after ultrasonic treatment of the graphite. When the graphite solution was treated with varying ultrasonic power and time, the microstructure changed gradually, and accordingly, the thermal conductivity characteristics of the composite containing the as-treated graphite was also different with each other. Thermal conductivity showed the best result in the silicone composite containing graphite prepared under the optimum condition of ultrasonic treatment, and the thermal conductivity of the composite improved proportionally along with the particle size of graphite. When the silicone composite was prepared by using a mixture of inorganic oxides and graphite rather than graphite alone, the thermal conductivity of the silicone composite was further increased. A silicone composite containing graphite was used for LED (light emitting diode) lighting system as a thermal interface material (TIM), and the temperature elevation due to heat generated, while the lighting was actually operated, was analyzed.

scholarly journals Design and Implementation of a Laboratory Equipment for Studying Heat Transfer by Conduction

2019 ◽  
Vol 11 (1) ◽  
pp. 153-156
Author(s):  
István Padrah ◽  
Judit Pásztor ◽  
Rudolf Farmos
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Conduction ◽  
Thermal Conduction ◽  
Transfer Mechanism ◽  
Measuring Instrument ◽  
Heat Transfer Mechanism ◽  
Laboratory Equipment ◽  
Insulating Materials ◽  
Design And Implementation

Abstract Thermal conduction is a heat transfer mechanism. It is present in our everyday lives. Studying thermal conductivity helps us better understand the phenomenon of heat conduction. The goal of this paper is to measure the thermal conductivity of various materials and compare results with the values provided by the manufacturers. To achieve this we assembled a measuring instrument and performed measurements on heat insulating materials.

Enhanced thermal conductivity of epoxy composites by constructing thermal conduction networks via adding hybrid alumina filler

2021 ◽  
Author(s):  
Zhong‐Yu Wang ◽  
Xiao‐Nan Zhou ◽  
Zi‐Xuan Li ◽  
Song‐Song Xu ◽  
Liu‐Cheng Hao ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Conduction ◽  
Epoxy Composites ◽  
Enhanced Thermal Conductivity

Improvement of Thermal Conductivity for Carbon Fabric Composites Base on the Fabric Structure

2021 ◽  
Vol 1037 ◽  
pp. 161-166
Author(s):  
Phone Thant Kyaw ◽  
Pyae Phyo Maung ◽  
Galina V. Malysheva
Keyword(s):  
Thermal Conductivity ◽  
Thermal Analysis ◽  
Thermal Load ◽  
Thermal Conduction ◽  
Thermal Calculation ◽  
Carbon Fabric ◽  
Fabric Structure ◽  
Fabric Composites ◽  
Load Calculation ◽  
Fabric Structures

This paper presents the development of methods for improving the thermal conductivity of fiber reinforcing materials based on the fabric structures. The thermal analysis of fabric structure in thermal load calculation is performed by Fourier’s Law of Thermal Conduction and Steady-State Thermal calculation in Siemens NX. This study leads to the development of thermal conductivity in manufacturing technology of fiber reinforcing materials. Keywords: Thermal conductivity, fabric structure, polymer composite materials

A 3D Optimized Frequency–Wavenumber (FK), Time–Space Optimized Symplectic (TSOS) Hybrid Method for Teleseismic Wave Modeling

2021 ◽  
Author(s):  
Weijuan Meng ◽  
Dinghui Yang ◽  
Xingpeng Dong ◽  
Jian Ma
Keyword(s):  
High Resolution ◽  
Seismic Wave ◽  
Hybrid Method ◽  
High Efficiency ◽  
Reference Model ◽  
3D Models ◽  
Realistic Model ◽  
High Accuracy ◽  
Memory Requirement ◽  
Time Space

ABSTRACT Although teleseismic waveform tomography can provide high-resolution images of the deep mantle, it is still unrealistic to numerically simulate the whole domain of seismic wave propagation due to the huge amount of computation. In this article, we develop a new three-dimensional hybrid method to address this issue, which couples the modified frequency–wavenumber (FK) method with the 3D time–space optimized symplectic (TSOS) method. First, the FK method, which is used to calculate the semianalytical incident wavefields in the layered reference model, is modified to compute the wavefields efficiently with a significantly low-memory requirement. Second, 3D TSOS method is developed to model the seismic wave propagating in the local 3D heterogeneous domain. The low memory requirement of the modified FK method and the high accuracy of the TSOS method make it feasible to obtain highly accurate synthetic seismograms efficiently. A crust–upper mantle model for P-, SV-, and SH-wave incidences is calculated to benchmark the accuracy and efficiency of the 3D optimized FK-TSOS method. Numerical experiments for 3D models with heterogeneities, undulated discontinuous interfaces, and realistic model in eastern Tibet, illustrate the capability of hybrid method to accurately capture the scattered waves caused by heterogeneities in 3D medium. The 3D optimized FK-TSOS method developed shows low-memory requirement, high accuracy, and high efficiency, which makes it be a promising forward method to further apply to high-resolution mantle structure images beneath seismic array.

Increasing heat transfer performance of thermoplastic polyurethane by constructing thermal conduction channels of ultra-thin boron nitride nanosheets and carbon nanotubes

2020 ◽  
Vol 44 (43) ◽  
pp. 18823-18830
Author(s):  
Yue Ruan ◽  
Nian Li ◽  
Cui Liu ◽  
Liqing Chen ◽  
Shudong Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Tensile Strength ◽  
Thermal Conduction ◽  
Heat Transfer Performance ◽  
Thermoplastic Polyurethane ◽  
Transfer Performance ◽  
Boron Nitride Nanosheets ◽  
Thermally Conductive

The TPU-based thermally conductive composite reaches a thermal conductivity of 1.35 W m−1 K−1 and increases the tensile strength by at least 300%.

Three-Dimensional Stress Analysis by Three-dimensional Local Hybrid Method

2006 ◽  
Vol 306-308 ◽  
pp. 523-528 ◽  
Author(s):  
Kenji Machida
Keyword(s):  
Stress Intensity ◽  
Hybrid Method ◽  
Three Dimensional ◽  
Domain Size ◽  
Problem Analysis ◽  
Specimen Thickness ◽  
Speckle Photography ◽  
Error Assessment ◽  
Optimal Analysis ◽  
Hybrid Domain

In the displacement measurement inside a specimen by speckle photography, it is not easy to get clear Young's fringes images. Stress-intensity factors of mixed mode can be estimated by embedded speckle photography. However, the error of the stress intensity factor inside a specimen was considerably large. To evaluate the 3-D stress field inside the specimen from displacement data on the free surface obtained from the 2-D intelligent hybrid method, we developed the 3-D local hybrid method based on an inverse problem analysis. The accuracy of the 3-D local hybrid method varies depending on the depth of the plane of error assessment, hybrid domain size, and specimen thickness. Hence the optimal analysis conditions were discussed.

Measurement of Specific Heat Using Bayesian Inference to Account for Uncertainties in the Calorimeter Performance

2006 ◽  
Author(s):  
A. F. Emery ◽  
K. Abernethy
Keyword(s):  
Thermal Conductivity ◽  
Bayesian Inference ◽  
Specific Heat ◽  
High Accuracy ◽  
Temperature History ◽  
Good Precision ◽  
Precise Characterization ◽  
Transient Conduction ◽  
Measured Specific Heat

One way of estimating thermal conductivity is to measure the temperature history for transient conduction. Unfortunately, the property estimated is usually not the conductivity but the thermal diffusivity, α = k/ρcp. While α can often be estimated with good precision, and ρ is usually well defined, the specific heat is often poorly known. As a consequence the uncertainty in the conductivity can be large. This paper reports the use of a calorimeter designed to measure the specific heat with high accuracy. The accuracy depends upon a precise characterization of the thermal performance of the calorimeter. Even when much care is taken, the calorimeter's behavior introduces uncertainty in the measured specific heat. The effects of these uncertainties are accounted for by using Bayesian inference to estimate the confidence intervals of the specific heat.

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