Effects of Variable Thermal Properties on Moving-Band-Source Temperatures

1975 ◽  
Vol 97 (3) ◽  
pp. 1074-1078 ◽  
Author(s):  
J. Isenberg ◽  
S. Malkin
Keyword(s):  
Thermal Properties ◽  
Thermal Stresses ◽  
Temperature Gradients ◽  
Heat Sources ◽  
Moving Heat Source ◽  
Constant Property ◽  
Surface Temperatures ◽  
Transverse Temperature ◽  
Property Model ◽  
Moving Band

Temperatures calculated by moving-heat-source theory for machining and sliding processes are often sufficiently large that the assumption of temperature-independent thermal properties is invalid. In the present paper results of a numerical analysis are presented that consider the effects of variable thermal properties on the temperatures due to a moving-band source. Compared with the constant-property model, the maximum surface temperatures are found to be significantly higher with small Peclet numbers and strong heat sources, but the average surface temperatures within the band are much less affected by the variations of thermal properties with temperature. The variable-property model also indicates significantly larger transverse temperature gradients, a phenomenon that should cause greater thermal stresses.

A Six-Part Survey: Rocket Heat-Transfer Literature

1960 ◽  
Vol 82 (3) ◽  
pp. 155-169
Author(s):  
Thomas F. Irvine ◽  
R. W. Graham ◽  
G. Morrell ◽  
R. D. Turnacliff ◽  
J. H. Robinson ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Flow Separation ◽  
Rocket Engine ◽  
Heat Sources ◽  
Nozzle Wall ◽  
Fluid Property ◽  
Wall Materials

The survey has been divided into the following parts: Rocket-Engine Heat Sources; Rocket Cooling Techniques; Nozzle Wall Materials; Variable Fluid-Property Effects; Predictions of Thermal Properties; Flow Separation and Acoustic Effects.

scholarly journals Variation of thermal conductivity of DPPC lipid bilayer membranes around the phase transition temperature

2017 ◽  
Vol 14 (130) ◽  
pp. 20170127 ◽  
Author(s):  
Sina Youssefian ◽  
Nima Rahbar ◽  
Christopher R. Lambert ◽  
Steven Van Dessel
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Thermal Properties ◽  
Transition Temperature ◽  
Lipid Bilayer ◽  
Lipid Bilayers ◽  
Phase Transition Temperature ◽  
Temperature Gradients ◽  
Phase Behaviour ◽  
Gel Phase

Given their amphiphilic nature and chemical structure, phospholipids exhibit a strong thermotropic and lyotropic phase behaviour in an aqueous environment. Around the phase transition temperature, phospholipids transform from a gel-like state to a fluid crystalline structure. In this transition, many key characteristics of the lipid bilayers such as structure and thermal properties alter. In this study, we employed atomistic simulation techniques to study the structure and underlying mechanisms of heat transfer in dipalmitoylphosphatidylcholine (DPPC) lipid bilayers around the fluid–gel phase transformation. To investigate this phenomenon, we performed non-equilibrium molecular dynamics simulations for a range of different temperature gradients. The results show that the thermal properties of the DPPC bilayer are highly dependent on the temperature gradient. Higher temperature gradients cause an increase in the thermal conductivity of the DPPC lipid bilayer. We also found that the thermal conductivity of DPPC is lowest at the transition temperature whereby one lipid leaflet is in the gel phase and the other is in the liquid crystalline phase. This is essentially related to a growth in thermal resistance between the two leaflets of lipid at the transition temperature. These results provide significant new insights into developing new thermal insulation for engineering applications.

Bi-Layered Model of Interfacial Thermal Stresses with the Effect of Different Temperatures in the Layers

2011 ◽  
Vol 87 ◽  
pp. 63-70 ◽  
Author(s):  
Sujan Debnath ◽  
Muhammad Ekhlasur Rahman ◽  
Woldemichael Dereje Engida ◽  
M. V. V. Murthy ◽  
K.N. Seetharamu
Keyword(s):  
Thermal Stresses ◽  
Physical Design ◽  
Temperature Gradients ◽  
Interfacial Stress ◽  
Stress Model ◽  
Interfacial Stresses ◽  
Linear Temperature ◽  
Layered Model ◽  
Die Attach ◽  
Different Temperatures

An interfacial shearing and peeling stress model is proposed to account for different uniform temperatures and thickness wise linear temperature gradients in the layers. This upgraded model can be viewed as a more generic form to determine interfacial stresses under different temperature conditions in a bi-layered assembly. The selected shearing and peeling stress results are presented for the case of die and die attach as commonly seen in electronic packaging. The obtained results can be useful in interfacial stress evaluations and physical design of bi-material assemblies, which are used in microelectronics and photonic applications.

Thermal Analysis of Solids at High Peclet Numbers Subjected to Moving Heat Sources

1999 ◽  
Vol 121 (1) ◽  
pp. 182-186 ◽  
Author(s):  
O. Manca ◽  
B. Morrone ◽  
S. Nardini
Keyword(s):  
Thermal Field ◽  
Three Dimensional ◽  
Heat Losses ◽  
Transfer Model ◽  
Heat Sources ◽  
Moving Heat Source ◽  
Motion Direction ◽  
Thermal Fields ◽  
Diffusion Component ◽  
Conductive Thermal Field

A three-dimensional heat transfer model has been developed to obtain the conductive thermal field inside a brick-type solid under a moving heat source with different beam profiles. The problem in quasi-steady state has been approximated by neglecting the axial diffusion component; thus, for Peclet numbers greater than 5, the elliptic differential equation becomes a parabolic one along the motion direction. The dependence of the solution on the radiative and convective heat losses has been highlighted. Thermal fields are strongly dependent on different spot shapes and on the impinging jet; this situation allows control of the parameters involved in the technological process.

Effect of Compliance on Residual Stresses in Manufacturing with Moving Heat Sources

2021 ◽  
pp. 1-53
Author(s):  
Mitchell R. Grams ◽  
Patricio F. Mendez
Keyword(s):  
Residual Stresses ◽  
Thermal Stresses ◽  
Ad Hoc ◽  
Mathematical Treatment ◽  
Heat Sources ◽  
Plastic Part ◽  
Practical Applications ◽  
Tendon Force ◽  
Design Calculations ◽  
Force Concept

Abstract Manufacturing processes involving moving heat sources include additive manufacturing, welding, laser processing (cladding and heat treatment), machining, and grinding. These processes involve high local thermal stresses that induce plasticity and result in permanent residual stress and distortion. The residual stresses are typically calculated numerically at great computational expense despite the fact that the inelastic fraction of the domain is very small. Efforts to decouple the small plastic part from the large elastic part have led to the development of the tendon force concept. The tendon force can be predicted analytically for the case of infinitely rigid components; however, this limitation has prevented the broader use of the concept in practical applications. This work presents a rigorous mathematical treatment using dimensional analysis, asymptotics, and blending which demonstrates that the effect of geometric compliance depends on a single dimensionless group, the Okerblom number. Closed-form expressions are derived to predict the effect of compliance without the need for empirical ad-hoc fitting or calibration. The proposed expressions require input of only material properties and tabulated process parameters, and are thus ideally suited for use in metamodels and design calculations, as well as incorporation into engineering codes and standards.

A comparison of root surface temperatures using different obturation heat sources

1998 ◽  
Vol 24 (9) ◽  
pp. 617-620 ◽  
Author(s):  
Frances S. Lee ◽  
Joseph E. Van Cura ◽  
Ellen BeGole
Keyword(s):  
Root Surface ◽  
Heat Sources ◽  
Surface Temperatures

Evaluation of Mechanical and Thermal Stresses in Polymer Gear Teeth through Simulation Approach

2013 ◽  
Vol 302 ◽  
pp. 468-473 ◽  
Author(s):  
Per Lindholm ◽  
Jian Qin
Keyword(s):  
Thermal Properties ◽  
Thermal Stresses ◽  
Material Selection ◽  
Gear Tooth ◽  
Gear Wheel ◽  
Spur Gear ◽  
Contact Forces ◽  
Mechanical And Thermal Properties ◽  
Gear Mesh ◽  
Tensional Stress

One way to achieve lightweight and lubricant-free drive train is, among others, to convert conventional steel to polymer composite materials. This paper describes a part of this endeavor by taking a spur gear pair as a study object. One of the steel gear wheel is replaced with three different materials including Victrex PEEK 650G, Victrex PEEK 650CA30 and Luvocom PEEK 1105-8165 while keeping the gear geometry unchanged. Mechanical stresses and thermal properties are two major criteria for material selection at this stage. Therefore carbon fiber filled PEEK (Victrex PEEK 650CA30) and PEEK filled with thermal conductive minerals (Luvocom 1105-8165) are chosen to benchmark each of the criterion. The evaluation is done by modeling the gear mesh and analyzing the contact forces and heat generated in the gear tooth. The results show surface temperature on the tooth flanks, root tensional stress and contact pressure during the tooth mesh. The work suggests a guideline of materials selection. Depending on actual application a compromisation between mechanical and thermal properties often needs to be considered within the tolerance boundary in order to obtain optimized results. This work only deals with material selection. Gear design such as optimization of tooth geometry for polymer gears is out of the scope of this study and will not be discussed.

scholarly journals Propagation of Thermal Stresses in an Infinite Medium

1959 ◽  
Vol 11 (4) ◽  
pp. 237-244 ◽  
Author(s):  
F. J. Lockett ◽  
I. N. Sneddon
Keyword(s):  
Thermal Stresses ◽  
Infinite Medium ◽  
Nonuniform Distribution ◽  
The Body ◽  
Heat Sources ◽  
Dynamic Stresses ◽  
Elastic Bodies ◽  
State Of Stress ◽  
Body Forces ◽  
Uneven Heating

In the full linear theory of thermoelasticity there is a coupling between the thermal and the purely mechanical effects so that not only does a nonuniform distribution of temperature in the solid produce a state of stress but dynamical body forces or applied surface tractions produce variations in temperature throughout the body. In a recent paper (Eason and Sneddon, (2)) an account was given of the calculation of the dynamic stresses produced in elastic bodies, both infinite and semi-infinite, by uneven heating. In this paper we shall consider the propagation of thermal stresses in an infinite medium when, in addition to heat sources, there are present body forces which vary with the time.

Investigations of Transient Machined Workpiece Surface Temperature in High Speed Peripheral Milling Using Inverse Method

2012 ◽  
Vol 723 ◽  
pp. 14-19 ◽  
Author(s):  
Zhan Qiang Liu ◽  
Fan Zhang ◽  
Fu Lin Jiang
Keyword(s):  
Heat Source ◽  
Surface Temperature ◽  
High Speed ◽  
Inverse Method ◽  
Moving Heat Source ◽  
Peripheral Milling ◽  
Machined Surface ◽  
Workpiece Temperature ◽  
Surface Temperatures ◽  
1045 Steel

In high speed machining, temperature distribution in workpiece is the main factor which directly affects the surface integrity and dimensional accuracy of machined workpiece. In this paper, the machined workpiece temperature in high speed peripheral milling is analyzed through using moving heat source method and inverse method. Firstly, the workpiece to be machined is considered as a semi-infinite solid to model the transient surface temperature using arc-shaped moving heat source. Inverse method is then applied for the calculating of heat flux. Peripheral milling experiments of 1045 steel is performed with coated carbide insert The machined surface temperatures were measured during experiments. The measured results were found to be in agreement with the predicted ones by transient models for machined surface temperatures. These results confirm the conclusion that the transient workpiece temperature will decline when the cutting speed increases to a critical value.

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