Laminate Delamination Due to Thermal Gradients

1995 ◽  
Vol 117 (4) ◽  
pp. 386-390 ◽  
Author(s):  
J. W. Hutchinson ◽  
T. J. Lu
Keyword(s):  
Steady State ◽  
Heat Flow ◽  
Thermal Stresses ◽  
Temperature Gradients ◽  
Thermal Gradients ◽  
Steady State Analysis ◽  
Flow Through ◽  
Laminate Thickness ◽  
Fail Safe ◽  
Delamination Cracks

Flaw-induced delamination of orthotropic laminates subject to through-thickness temperature gradients is analyzed. A crack-like flaw impedes heat flow through the laminate, producing thermal stresses and crack tip stress intensities. The focus is on delamination cracks which propagate under steady-state conditions. The steady-state analysis becomes accurate for a crack whose length is about one laminate thickness. Moreover, the analysis provides realistic fail-safe criteria for excluding delamination.

Performance Indicators for Steady-State Heat Transfer Through Fin Assemblies

1996 ◽  
Vol 118 (2) ◽  
pp. 310-316 ◽  
Author(s):  
A. S. Wood ◽  
G. E. Tupholme ◽  
M. I. H. Bhatti ◽  
P. J. Heggs
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Heat Flow ◽  
Performance Indicators ◽  
Physical Parameters ◽  
State Heat ◽  
Extended Surface ◽  
Flow Through ◽  
Steady State Heat ◽  
Steady State Heat Transfer

A comparative study is presented of several models describing steady-state heat flow through an assembly consisting of a primary surface (wall) and attached extended surface (fin). Attention is focused on the validity of four performance indicators. The work shows that the augmentation factor is the only indicator capable of correctly predicting the behavioral trends of the rate of heat flow through the assembly as the influencing physical parameters are varied.

scholarly journals Steady-state heat flow through hollow clay bricks

2020 ◽  
Vol 834 ◽  
pp. 012021
Author(s):  
H Ghailane ◽  
M A Ahamat ◽  
M Md Padzi ◽  
S Beddu
Keyword(s):  
Steady State ◽  
Heat Flow ◽  
Clay Bricks ◽  
State Heat ◽  
Flow Through ◽  
Steady State Heat

scholarly journals Thermal Bridge Modeling and a Dynamic Analysis Method Using the Analogy of a Steady-State Thermal Bridge Analysis and System Identification Process for Building Energy Simulation: Methodology and Validation

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4422
Author(s):  
Heegang Kim ◽  
Myoungsouk Yeo
Keyword(s):  
Steady State ◽  
Heat Flow ◽  
Dynamic Analysis ◽  
Building Energy ◽  
Energy Simulation ◽  
Building Energy Simulation ◽  
Analysis Method ◽  
Identification Process ◽  
Thermal Bridge ◽  
Flow Through

It is challenging to apply heat flow through a thermal bridge, which requires the analysis of 2D or 3D heat transfer to building energy simulation (BES). Research on the dynamic analysis of thermal bridges has been underway for many years, but their utilization remains low in BESs. This paper proposes a thermal bridge modeling and a dynamic analysis method that can be easily applied to BESs. The main idea begins with an analogy of the steady-state analysis of thermal bridges. As with steady-state analysis, the proposed method first divides the thermal bridge into a clear wall, where the heat flow is uniform, and the sections that are not the clear wall (the thermal bridge part). For the clear wall part, the method used in existing BESs is applied and analyzed. The thermal bridge part (TB part) is modeled with the linear time-invariant system (LTI system) and the system identification process is performed to find the transfer function. Then, the heat flow is obtained via a linear combination of the two parts. This method is validated by comparing the step, sinusoidal and annual outdoor temperature response of the finite differential method (FDM) simulation. When the thermal bridge was modeled as a third-order model, the root mean square error (RMSE) of annual heat flow with the FDM solution of heat flow through the entire wall was about 0.1 W.

The Effect of Coatings on the Steady-State and Short Time Constriction Resistance for an Arbitrary Axisymmetric Flux

1985 ◽  
Vol 107 (1) ◽  
pp. 33-38 ◽  
Author(s):  
J. R. Dryden ◽  
M. M. Yovanovich ◽  
A. S. Deakin
Keyword(s):  
Thermal Properties ◽  
Steady State ◽  
Heat Flow ◽  
Contact Spot ◽  
One Dimensional ◽  
Constriction Resistance ◽  
Transient Heat Flow ◽  
Flow Through ◽  
Short Time ◽  
Short Times

The effect of a coating upon the short-time and steady-state constriction resistance is analyzed for an arbitrary axisymmetric contact spot flux. At very short times the expression obtained for R is identical to the expression for one-dimensional transient heat flow through a two-layer wall. At steady-state, the results of the analysis predict that the effect of the coating are mainly dependent on the relative thermal properties of the coating and substrate. The limiting cases, where the coating thickness approaches either zero or infinity, are discussed.

Morphological Evolution of Intragranular Void under the Thermal-Stress Gradient Generated by the Steady State Heat Flow in Encapsulated Metallic Films: Special Reference to Flip Chip Solder Joints

2008 ◽  
Vol 139 ◽  
pp. 151-156
Author(s):  
Tarik Omer Ogurtani ◽  
Oncu Akyildiz
Keyword(s):  
Thermal Stress ◽  
Steady State ◽  
Heat Flow ◽  
Thermal Stresses ◽  
Morphological Evolution ◽  
Stress Gradient ◽  
Lateral Spreading ◽  
Windward Side ◽  
State Heat ◽  
Steady State Heat

The morphological evolution of intragranular voids induced by the surface drift-diffusion under the action of capillary forces, electromigration (EM) forces, and thermal stress gradients (TSG) associated with steady state heat flow is investigated in passivated metallic thin films via computer simulation using the front-tracking method. As far as the device reliability is concerned, the most critical configuration for interconnect failure occurs even when thermal stresses are low if the normalized ratio of interconnect width to void radius is less than certain range of values (which indicates the onset of heat flux crowding). This regime manifests itself by the formation of two symmetrically disposed finger shape extrusions (pitchfork shape slits) on the upper and lower shoulders of the void surface on the windward side. The void growth (associated with supersaturated vacancy condensation) on the other hand inhibits anode displacement but enhances cathode and shoulder slit velocities drastically, which causes lateral spreading.

scholarly journals Thermal Bridge Modeling and a Dynamic Analysis Method Using the Analogy of a Steady-State Thermal Bridge Analysis and System Identification Process for Building Energy Simulation: Methodology and Validation

2020 ◽  
Author(s):  
Heegang Kim ◽  
Myoungsouk Yeo
Keyword(s):  
Steady State ◽  
Heat Flow ◽  
Dynamic Analysis ◽  
Building Energy ◽  
Energy Simulation ◽  
Building Energy Simulation ◽  
Analysis Method ◽  
Identification Process ◽  
Thermal Bridge ◽  
Flow Through

It is challenging to apply heat flow through a thermal bridge, which requires the analysis of 2D or 3D heat transfer to building energy simulation(BES). Research on the dynamic analysis of thermal bridges has been underway for many years, but their utilization remains low in BESs. This paper proposes a thermal bridge modeling and a dynamic analysis method that can be easily applied to BESs. The main idea begins with an analogy of the steady-state analysis of thermal bridges. As with steady-state analysis, the proposed method first divides the thermal bridge into a clear wall, where the heat flow is uniform, and the sections that are not the clear wall (the thermal bridge part). For the clear wall part, the method used in existing BESs is applied and analyzed. The thermal bridge part (TB part) is modeled with the linear time-invariant system (LTI system) and the system identification process is performed to find the transfer function. Then, the heat flow is obtained via a linear combination of the two parts. This method is validated by comparing the step, sinusoidal and annual outdoor temperature response of the finite differential method(FDM) simulation. When the thermal bridge was modeled as a third-order model, the root mean square error(RMSE) of annual heat flow with the FDM solution of heat flow through the entire wall was about 0.1W.

Temperature regulation and heat dissipation during flight in birds

1976 ◽  
Vol 65 (2) ◽  
pp. 471-482 ◽  
Author(s):  
J. R. Torre-Bueno
Keyword(s):  
Steady State ◽  
Heat Flow ◽  
Skin Temperature ◽  
Core Temperature ◽  
Heat Dissipation ◽  
Sturnus Vulgaris ◽  
The Body ◽  
Ambient Temperatures ◽  
Flow Through ◽  
Animal Skin

Core and skin temperature were measured by radiotelemetry in starlings (Sturnus vulgaris) during 30 min flights in a wind tunnel. Core temperature was independent of ambient temperature from 0 to 28 degrees C. The temporal mean of the monitored core temperature during flight was 42-7 degrees C in one bird and 44-0 degrees C in another. These temperatures are 2-4 degrees C higher than the resting temperature in starlings, and are among the highest steady-state temperatures observed in any animal. Skin temperature on the breast was within a few degrees of core temperature. In some locations skin temperature was higher at low ambient temperatures than at intermediate ambient temperatures. An analysis of the data shows that a high core temperature does not function as an aid to head dissipation. On the contrary, insulation is adjusted to maintain a high temperature, presumably because it is necessary for flight. The increase in skin temperature at low ambient temperatures is believed to be a result of a decrease in heat flow through the breast feathers brought about by feather adjustments, to compensate for an unavoidable increase in heat flow in unfeathered or poorly feathered parts of the body.

Effect of Stabilizing Thermal Gradients on Natural Convection in Rectangular Enclosures

1979 ◽  
Vol 101 (2) ◽  
pp. 238-243 ◽  
Author(s):  
S. Ostrach ◽  
C. Raghavan
Keyword(s):  
Steady State ◽  
Natural Convection ◽  
Theoretical Calculations ◽  
Vertical Gradient ◽  
Temperature Gradients ◽  
Horizontal Gradient ◽  
Thermal Gradients ◽  
Aspect Ratios ◽  
Different Temperatures ◽  
Prandtl Numbers

An experimental investigation is described of the effect of stabilizing thermal gradients on natural convection in silicone oils in rectangular enclosures with different aspect ratios. The Prandtl numbers are of the order of 105, Grashof numbers range up to 20, and the aspect ratios are 1 and 3. The thermal boundary conditions are established by imposing different temperatures on opposite walls of the enclosure so that there is simultaneous horizontal and vertical heat flow. The effect of stabilizing temperature gradients on flow established by horizontal gradients and the effect of horizontal temperature gradients on a stably stratified fluid are studied for ranges of the parameters. Streamline patterns are observed at steady-state and velocity profiles are calculated from streamline data and extrapolated with approximate theoretical calculations. It is found that the flow generated by a horizontal gradient is retarded by a stabilizing thermal gradient. The reduction is shown as a function of the relevent parameters. For the range of variables investigated complete stabilization of the fluid driven by a horizontal gradient does not seem possible by means of a vertical gradient. The steady state flow patterns obtained do not depend on the manner in which the flow is started, i.e., on the order in which the temperature differences are imposed.

Steady-state thermal stresses in an elastic solid containing an insulated penny-shaped crack

1975 ◽  
Vol 10 (1) ◽  
pp. 19-24 ◽  
Author(s):  
J R Barber
Keyword(s):  
Thermal Stress ◽  
Steady State ◽  
Heat Flow ◽  
Thermal Stresses ◽  
Mixed Boundary ◽  
Elastic Solid ◽  
Mixed Boundary Value Problem ◽  
Penny Shaped Crack ◽  
Shaped Crack ◽  
Axisymmetric Problems

A solution is given for the steady-state thermal stress and displacement field in an infinite elastic solid containing an insulated penny-shaped crack. The problem is reduced to a mixed-boundary-value problem for the half-space, making use of Green's isothermal solution for the thick elastic plate in complex harmonic potentials and a particular thermoelastic solution due to Williams. In the axisymmetric case, the complex potential reduces to the real harmonic function used by Shail in his solution for the external crack. To illustrate the use of the method in both axisymmetric and non-axisymmetric problems, complete solutionsare given for (1) a uniform heat flow and (2) a linearly varying heat flow disturbed by an insulated penny-shaped crack.

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