A MATHEMATICAL MODEL FOR THE ESTIMATION OF THERMAL STRESS AND DEVELOPMENT OF COLD INJURIES ON THE EXPOSED ORGANS OF HUMAN BODY

2016 ◽  
Vol 16 (05) ◽  
pp. 1650062 ◽  
Author(s):  
M. A. KHANDAY ◽  
FIDA HUSSAIN ◽  
AIJAZ NAJAR ◽  
KHALID NAZIR
Keyword(s):  
Mathematical Model ◽  
Finite Element ◽  
Thermal Stress ◽  
Human Body ◽  
Thermal Damage ◽  
Cell Damage ◽  
Bioheat Equation ◽  
Peripheral Tissues ◽  
Thermoregulatory System ◽  
Extreme Cold

The severe ambient temperature always disrupts the normal thermoregulatory system of the human body. The decrease in core temperature leads to hypothermia and the development of cold injuries takes place at the exposed shells of the human body. The intensity of the cold exposure and its duration leads to various degrees of frostbites and resulting cell damage and fluid passage from the necrotic regions. In this paper, variational finite element has been employed to estimate the thermal damage due to severe cold conditions. The formulation of the model is based on Pennes’ bioheat equation and mass diffusion equation. Moreover, the fluid passage from the cold injuries at the peripheral tissues of the human body with respect to extreme cold conditions has been analyzed in relation with other parameters.

Tissue necrosis and passage of fluid due to cold stress from the thermally damaged human body peripherals: A mathematical model

2015 ◽  
Vol 04 (02) ◽  
pp. 1550012
Author(s):  
M. A. Khanday ◽  
Fida Hussain ◽  
Khalid Nazir
Keyword(s):  
Mathematical Model ◽  
Finite Element ◽  
Heat Equation ◽  
Cold Stress ◽  
Human Body ◽  
Human Subjects ◽  
Diffusion Equations ◽  
Tissue Necrosis ◽  
Cold Temperatures ◽  
Element Technique

The development of cold injury takes place in the human subjects by means of crystallization of tissues in the exposed regions at severe cold temperatures. The process together with the evaluation of the passage of fluid discharge from the necrotic regions with respect to various degrees of frostbites has been carried out by using variational finite element technique. The model is based on the Pennes' bio-heat equation and mass diffusion equations together with suitable initial and boundary conditions. The results are analyzed in relation with atmospheric temperatures and other parameters of the tissue medium.

Numerical Study on Electric Characteristics and Thermal Stresses of Solid Oxide Fuel Cells

2012 ◽  
Author(s):  
Pengfei Fan ◽  
Xiongwen Zhang ◽  
Guojun Li
Keyword(s):  
Mathematical Model ◽  
Finite Element ◽  
Thermal Stress ◽  
Fuel Cell ◽  
Solid Oxide Fuel Cells ◽  
Temperature Profile ◽  
Potential Distribution ◽  
Electrical Potential ◽  
Solid Oxide ◽  
Oxide Fuel

A generalized, three-dimensional (3D) mathematical model of solid oxide fuel cells (SOFCs) for various geometries is constructed in this paper. A finite-volume method is applied to calculate the electric characteristics, which is based on the fundamental conservation law of mass, energy and electrical charge. The electrical potential distribution, the current density distribution, the concentrations distribution of the chemical species and the temperature profile are calculated by solving the governing equations of a single-unit model with double channels of co-flow and counter-flow pattern using the commercial computational fluid dynamic software Fluent. The internal steam reforming and the water shift reactions are taken into account in the mathematical model. The Knudsen diffusion is considered for computation of the gases diffusion in the porous electrodes and the concentration overpotential. The Butler-Volmer equation and the function of the reaction gases composition for the exchange density are used in the model to analyze the activation overpotential. Numerical simulations are performed for a planar geometry solid oxide fuel cell and the detailed features of the temperature, the electrical potential distribution and the gases composition are illustrated. The simulation results agree well with the Benchmark results for planar configuration. With the simulated temperature profile in the planar SOFC, the finite-element method is employed to calculate the thermal stress distribution in the planar solid oxide fuel cell. A 3D finite-element model consists of positive electrode-electrolyte-negative electrode (PEN) and interconnects assembly is constructed by using commercial finite-element code Abaqus. The effects of temperature profile, electrodes and electrolyte thickness, and coefficients of thermal expansion (CTE) mismatch between components are characterized. The calculated results indicate that the maximum stress appears on the electrode and electrolyte interface. The value and distribution of the thermal stress are the functions of the applied materials CTE, applied temperature profiles and the thicknesses of electrode and electrolyte. The calculated results can be applied as the guide for the SOFC materials selection and the SOFC structure design.

TEMPERATURE DISTRIBUTION AND THERMAL DAMAGE OF PERIPHERAL TISSUE IN HUMAN LIMBS DURING HEAT STRESS: A MATHEMATICAL MODEL

2016 ◽  
Vol 16 (05) ◽  
pp. 1650064 ◽  
Author(s):  
MIR AIJAZ ◽  
M. A. KHANDAY
Keyword(s):  
Finite Element ◽  
Temperature Distribution ◽  
Heat Generation ◽  
Thermal Damage ◽  
Subcutaneous Tissue ◽  
The Body ◽  
Bioheat Equation ◽  
Metabolic Heat ◽  
Metabolic Heat Generation ◽  
Living Tissues

The physiological processes taking place in human body are disturbed by the abnormal changes in climate. The changes in environmental temperature are not effective only to compete with thermal stability of the system but also in the development of thermal injuries at the skin surfaces. Therefore, it is of great importance to estimate the temperature distribution and thermal damage in human peripherals at extreme temperatures. In this paper, the epidermis, dermis and subcutaneous tissue were modeled as uniform elements with distinct thermal properties. The bioheat equation with appropriate boundary conditions has been used to estimate the temperature profiles at the nodal points of the skin and subcutaneous tissue with variable ambient heat and metabolic activities. The model has been solved by variational finite element method and the results of the changes in temperature distribution of the body and the damage to the exposed living tissues has been interpreted graphically in relation with various atmospheric temperatures and rate of metabolic heat generation. By involving the metabolic heat generation term in bioheat equation and using the finite element approach the results obtained in this paper are more reasonable and appropriate than the results developed by Moritz and Henriques, Diller and Hayes, and Jiang et al.

Laser-Induced Thermal Damage to K9 Glass on Finite Element Method

2013 ◽  
Vol 444-445 ◽  
pp. 1422-1426
Author(s):  
Li Zi Chen ◽  
Chun Yuan Jing ◽  
Xiao Wei Guan
Keyword(s):  
Finite Element ◽  
Temperature Field ◽  
Thermal Stress ◽  
Stress Field ◽  
Thermal Damage ◽  
Laser Damage Threshold ◽  
Element Analysis ◽  
Finite Element Software ◽  
Thermal Stress Field ◽  
K9 Glass

Based on the theory of the thermal conduction and the thermal elastic equations, does some researches in view of the thermal Damage of K9 glass by finite element analysis. The distribution of temperature field and thermal stress field of the ideal K9 glass which irradiated by 100W pulsed-Nd: YAG laser are simulated with finite element software. The result shows that the temperature of the surface of glass doesnt reach the melting and the thermal stress of it doesnt get to the requirement for fracture strength. Then, the model of K9 glass containing inclusions has be built. The simulation result indicates that inclusions may affect the distribution of temperature field and thermal stress field of the K9 glass, which makes the injected laser beams energy centralize on a small area around the inclusions owing to the existence of the strong absorbing, thus leading to K9 glass laser damage threshold reduction and easier to thermal damage.

Simulation of the Effect of Solar Radiation on Hardening and Hardened Concrete Wall

2010 ◽  
Vol 163-167 ◽  
pp. 1489-1494
Author(s):  
Dong Hui Huang ◽  
Sheng Xing Wu ◽  
Hai Tao Zhao
Keyword(s):  
Mathematical Model ◽  
Finite Element Method ◽  
Finite Element ◽  
Thermal Stress ◽  
Solar Radiation ◽  
Numerical Models ◽  
Concrete Structures ◽  
Heat Of Hydration ◽  
Hardened Concrete ◽  
Concrete Wall

The purpose of the present study is to assess the effect of solar radiation on the development of thermal stress in hardening and hardened concrete structures. A mathematical model for solar radiation is investigated. A finite element method program is developed for the temperature and thermal stress analysis including the heat of hydration, creep, shrinkage, and ambient temperature, especially the solar radiation. Meanwhile, the effect of solar radiation on the concrete wall during its service life is considered. The results obtained from the numerical models show that for the hardening concrete wall, solar radiation reduce the stress at the first 36 hours on surface and first 48 hours in the center of the wall, after that the stresses both on surface and in the center of the wall increases quickly; for the hardened concrete wall, solar radiation increase the stress in the center of the wall. This program is useful to estimate the stress development and the effect of the solar radiation on the hardening and hardened concrete structures.

MATHEMATICAL MODEL FOR THE TRANSPORT OF OXYGEN IN THE LIVING TISSUE THROUGH CAPILLARY BED

2015 ◽  
Vol 15 (04) ◽  
pp. 1550055 ◽  
Author(s):  
M. A. KHANDAY ◽  
AIJAZ NAJAR
Keyword(s):  
Mathematical Model ◽  
Finite Element Method ◽  
Finite Element ◽  
Diffusion Equation ◽  
Oxygen Transport ◽  
Human Body ◽  
Oxygen Supply ◽  
Living Tissue ◽  
Capillary Bed ◽  
Living Tissues

Oxygen is essential for the survival of living tissues in the human body. The mechanism of oxygen transport in the human body is a subject of great concern. In the conditions like hypoxia and hypothermia, the amount of oxygen supply in the biological tissue loose homeostasis, thereby the concentration of O 2 and the liberation of CO 2 in the human body demands a special attention. The present study based on finite element method employed to the mass diffusion equation with suitable conditions has been established. The main objective of this work is to understand the behavior of O 2 through various compartments of the capillary bed. The concentration of O 2 at plasma and capillary layers has been estimated which in turn leads to understand the situation of oxygen transport during various situations.

An Eight-Node Hexahedral Finite Element with Rotational DOFs for Elastoplastic Applications

2019 ◽  
Vol 11 (1) ◽  
pp. 54-66
Author(s):  
Ayoub Ayadi ◽  
Kamel Meftah ◽  
Lakhdar Sedira ◽  
Hossam Djahara
Keyword(s):  
Mathematical Model ◽  
Finite Element ◽  
Plastic Zone ◽  
Displacement Vector ◽  
Small Strain ◽  
Benchmark Problems ◽  
Plasticity Model ◽  
Vector Approximation ◽  
Calculation Code

Abstract In this paper, the earlier formulation of the eight-node hexahedral SFR8 element is extended in order to analyze material nonlinearities. This element stems from the so-called Space Fiber Rotation (SFR) concept which considers virtual rotations of a nodal fiber within the element that enhances the displacement vector approximation. The resulting mathematical model of the proposed SFR8 element and the classical associative plasticity model are implemented into a Fortran calculation code to account for small strain elastoplastic problems. The performance of this element is assessed by means of a set of nonlinear benchmark problems in which the development of the plastic zone has been investigated. The accuracy of the obtained results is principally evaluated with some reference solutions.

Modal Analysis of the Axial Compressor Blade: Advanced Time-Dependent Electronic Interferometry and Finite Element Method

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Mykhaylo Tkach ◽  
Serhii Morhun ◽  
Yuri Zolotoy ◽  
Irina Zhuk
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Finite Element ◽  
High Reliability ◽  
Axial Compressor ◽  
Time Dependent ◽  
Experimental Setup ◽  
Vibration Modes ◽  
Compressor Blades ◽  
Isoparametric Finite Element

AbstractNatural frequencies and vibration modes of axial compressor blades are investigated. A refined mathematical model based on the usage of an eight-nodal curvilinear isoparametric finite element was applied. The verification of the model is carried out by finding the frequencies and vibration modes of a smooth cylindrical shell and comparing them with experimental data. A high-precision experimental setup based on an advanced method of time-dependent electronic interferometry was developed for this aim. Thus, the objective of the study is to verify the adequacy of the refined mathematical model by means of the advanced time-dependent electronic interferometry experimental method. The divergence of the results of frequency measurements between numerical calculations and experimental data does not exceed 5 % that indicates the adequacy and high reliability of the developed mathematical model. The developed mathematical model and experimental setup can be used later in the study of blades with more complex geometric and strength characteristics or in cases when the real boundary conditions or mechanical characteristics of material are uncertain.

Three Turnaround Heat Treating Studies

2003 ◽  
Author(s):  
Jaan Taagepera ◽  
Marty Clift ◽  
D. Mike DeHart ◽  
Keneth Marden
Keyword(s):  
Heat Treatment ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Stress ◽  
Thermal Stresses ◽  
Heat Treating ◽  
Element Analysis ◽  
Stress Profiles ◽  
Insight Into

Three vessel modifications requiring heat treatment were analyzed prior to and during a planned turnaround at a refinery. One was a thick nozzle that required weld build up. This nozzle had been in hydrogen service and required bake-out to reduce the potential for cracking during the weld build up. Finite element analysis was used to study the thermal stresses involved in the bake-out. Another heat treatment studied was a PWHT of a nozzle replacement. The heat treatment band and temperature were varied with location in order to minimize cost and reduction in remaining strength of the vessel. Again, FEA was used to provide insight into the thermal stress profiles during heat treatment. The fmal heat treatment study was for inserting a new nozzle in a 1-1/4Cr-1/2Mo reactor. While this material would ordinarily require PWHT, the alteration was proposed to be installed without PWHT. Though accepted by the Jurisdiction, this nozzle installation was ultimately cancelled.

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