Characterization of applied tensile stress to carbon epoxy composites by measuring the variation of transverse thermal conductivity using transmission thermography

2019 ◽  
Vol 54 (10) ◽  
pp. 1363-1372
Author(s):  
M Bayat ◽  
MS Safizadeh
Keyword(s):  
Thermal Conductivity ◽  
Tensile Stress ◽  
Applied Stress ◽  
Longitudinal Direction ◽  
Sample Thickness ◽  
Beam Sample ◽  
Step Heating ◽  
Transverse Thermal Conductivity ◽  
Simulation Results ◽  
Thermal Conductivity Variation

Using the method of step heating thermography, this study seeks to detect and characterize the existence of stress in a beam sample of carbon epoxy composite with the stacking sequence of [08] aided by empirical and simulation approaches. The applied stress in the longitudinal direction of sample, while considering the Poisson’s ratio, changes the lateral dimensions of sample. Furthermore, it is shown that the thermal conductivity along the sample thickness varies as a result of stress existence. Accordingly, to obtain a relation between transverse thermal conductivity and longitudinal tensile stress, one should calculate and eliminate the effect of lateral deformation caused by stress. To this end, by combining the experimental and simulation results of composite sample under the action of different tensile loads, an equation describing the variation of thermal conductivity along the sample thickness with respect to applied stress is developed. Using the relation of transverse thermal conductivity variation in terms of applied stress, the finite element modeling is again carried out by rectifying the values of thermal conductivity. Simulation results are compared with experimental ones, indicating very good agreement between the two approaches.

scholarly journals Schemes for and Mechanisms of Reduction in Thermal Conductivity in Nanostructured Thermoelectrics

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Xiaoliang Zhang ◽  
Ming Hu ◽  
Konstantinos P. Giapis ◽  
Dimos Poulikakos
Keyword(s):  
Thermal Conductivity ◽  
Energy Conversion ◽  
Conversion Efficiency ◽  
Longitudinal Direction ◽  
Energy Conversion Efficiency ◽  
Nonequilibrium Molecular Dynamics ◽  
Boundary Scattering ◽  
Nanowire Surface ◽  
Simulation Results ◽  
Nanocomposite Structures

Nonequilibrium molecular dynamics (NEMD) simulations were performed to investigate schemes for enhancing the energy conversion efficiency of thermoelectric nanowires (NWs), including (1) roughening of the nanowire surface, (2) creating nanoparticle inclusions in the nanowires, and (3) coating the nanowire surface with other materials. The enhancement in energy conversion efficiency was inferred from the reduction in thermal conductivity of the nanowire, which was calculated by imposing a temperature gradient in the longitudinal direction. Compared to pristine nanowires, our simulation results show that the schemes proposed above lead to nanocomposite structures with considerably lower thermal conductivity (up to 82% reduction), implying ∼5X enhancement in the ZT coefficient. This significant effect appears to have two origins: (1) increase in phonon-boundary scattering and (2) onset of interfacial interference. The results suggest new fundamental–yet realizable ways to improve markedly the energy conversion efficiency of nanostructured thermoelectrics.

Numerical Simulation & Experimental Investigation of SMT Laser Microsoldering Thermal Process

1991 ◽  
Vol 226 ◽  
Author(s):  
Wang Chunqing ◽  
Qian Yiyu ◽  
Jiang Yihong
Keyword(s):  
Thermal Conductivity ◽  
Numerical Simulation ◽  
Experimental Investigation ◽  
Thermal Process ◽  
Light Wave ◽  
Light Reflection ◽  
Lead Wire ◽  
Wire Surface ◽  
Conductivity Variation ◽  
Thermal Conductivity Variation

AbstractIn this paper,a numerical simulation of thermal process in the SMT laser microsoldering joint has been developed, in which, the influence on thermal process of the factors such as the thermal conductivity variation of solder with temperature, light reflection coefficient of the lead wire surface, and heat exchange on the surface of SMT materials all have been considered. In order to carry this numerical calculation practice and prove it's results,the reflexive characteristic of light wave to the SMT materials has been gauged,and the dynamic temperature process of laser microjoint has been measured by a new experimental method which was invented by the authors.The results of numerical simulation have been borne out by the tests, and the influences of heating parameters on thermal process has been analysed in this paper.The conclusions will be advantageous to the further study of the microjoint quality control in the SMT laser microsoldering.

scholarly journals Numerical modeling of microwave heating

2010 ◽  
Vol 42 (1) ◽  
pp. 99-124 ◽  
Author(s):  
A.K. Shukla ◽  
A. Mondal ◽  
A. Upadhyaya
Keyword(s):  
Thermal Conductivity ◽  
Numerical Modeling ◽  
Temperature Distribution ◽  
Microwave Heating ◽  
Two Dimensional ◽  
Conventional Furnace ◽  
Microwave Furnace ◽  
Simulation Results ◽  
Heating Behavior ◽  
Cylindrical Samples

The present study compares the temperature distribution within cylindrical samples heated in microwave furnace with those achieved in radiatively-heated (conventional) furnace. Using a two-dimensional finite difference approach the thermal profiles were simulated for cylinders of varying radii (0.65, 6.5, and 65 cm) and physical properties. The influence of susceptor-assisted microwave heating was also modeled for the same. The simulation results reveal differences in the heating behavior of samples in microwaves. The efficacy of microwave heating depends on the sample size and its thermal conductivity.

scholarly journals Thermal properties of closed-cell aluminum foam with circular pores

2014 ◽  
Vol 18 (5) ◽  
pp. 1619-1624 ◽  
Author(s):  
Guo-Yun Lu ◽  
Bu-Yun Su ◽  
Zhi-Qiang Li ◽  
Zhi-Hua Wang ◽  
Wei-Dong Song ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Property ◽  
Cell Size ◽  
Aluminum Foam ◽  
Slight Effect ◽  
Apparent Thermal Conductivity ◽  
Closed Cell ◽  
Simulation Results

The thermal property of closed-cell aluminum foam is studied numerically and the effects of the distribution of the circular pore on the thermal property are studied theoretically. When the convection and radiation are ignored, the effects of porosity, cell size, and distribution forms of pore on the apparent thermal conductivity are investigated. Moreover, the effects of air in the pore on the thermal property are analyzed as well. Simulation results show that apparent thermal conductivity linearly increases with the increase of porosity, while the cell size and the distribution have negligible effects on the thermal property. By comparison, thermal conductivity of air has slight effect on thermal property of foamed aluminum in the context of small size pore.

Thermal Transport in Nanocrystalline Materials

2005 ◽  
Author(s):  
Zhanrong Zhong ◽  
Xinwei Wang
Keyword(s):  
Thermal Conductivity ◽  
Specific Heat ◽  
Thermal Transport ◽  
Nanocrystalline Materials ◽  
Large Scale ◽  
Md Simulation ◽  
Fundamental Physics ◽  
Grain Sizes ◽  
Simulation Results ◽  
Thermal Phenomena

In this work, thermal transport in nanocrystalline materials is studied using large-scale equilibrium molecular dynamics (MD) simulation. Nanocrystalline materials with different grain sizes are studied to explore how and to what extent the size of nanograins affects the thermal conductivity and specific heat. Substantial thermal conductivity reduction is observed and the reduction is stronger for nanocrystalline materials with smaller grains. On the other hand, the specific heat of nanocrystalline materials shows little change with the grain size. The simulation results are compared with the thermal transport in individual nanograins based on MD simulation. Further discussions are provided to explain the fundamental physics behind the observed thermal phenomena in this work.

Multi-scale numerical prediction of flow-induced thermal conductivity variation in micro-injection molded heat sink

2016 ◽  
Vol 24 (3) ◽  
pp. 566-573
Author(s):  
杨灿 YANG Can ◽  
曹泽卫 CAO Ze-wei ◽  
尹晓红 YIN Xiao-hong ◽  
阚君武 KAN Jun-wu ◽  
程光明 CHENG Guang-ming ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Sink ◽  
Numerical Prediction ◽  
Multi Scale ◽  
Conductivity Variation ◽  
Injection Molded ◽  
Thermal Conductivity Variation
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