Analysis and Simulation of Thermal Transients and Resultant Stresses and Strains in TAB Packaging

1993 ◽  
Vol 115 (1) ◽  
pp. 34-38 ◽  
Author(s):  
M. A. Jog ◽  
I. M. Cohen ◽  
P. S. Ayyaswamy
Keyword(s):  
Thermal Stresses ◽  
Equivalent Stress ◽  
The Body ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Shear Stresses ◽  
Transfer Coefficients ◽  
Thermal Transients ◽  
Power Cycling ◽  
Accelerated Thermal Cycling

During normal power cycling of the electronic equipment, the differing coefficients of thermal expansion result in differential elongations. Because each level of packaging is subject to mounting constraints, the differential strains result in bending and shear stresses. Repeated duty cycling can cause fatigue at joints, at interfaces between different materials, at interconnection locations, or cause delamination of composite materials. Accelerated Thermal Cycling (ATC) is done to simulate the fatigue failures that may arise because of this power cycling. The current practice is to determine ATC stresses by assuming that the temperatures of various layers are equal and constant. In this study, we have relaxed the isothermal assumption and we provide results for thermal stresses and strains in a first level package. This is accomplished by accurately determining the transient temperature fields in various layers of the package. Temperature variations for different heat transfer coefficients have also been calculated. The results indicate that realistic estimates of thermal stresses and strains are only possible with models that allow for temperature variation in the body of the package. High equivalent stress values are obtained at the chip-heat sink interface and in the bumps connecting the leads to the chip.

A Three-Dimensional Finite Difference Solution for the Thermal Stresses in Railcar Wheels

1969 ◽  
Vol 91 (3) ◽  
pp. 891-896 ◽  
Author(s):  
G. E. Novak ◽  
B. J. Eck
Keyword(s):  
Computer Program ◽  
Thermal Stresses ◽  
Three Dimensional ◽  
Transient Temperature ◽  
Shear Stresses ◽  
Radial Temperature ◽  
Closed Form Solutions ◽  
Brake Application ◽  
History Of ◽  
Thin Disks

A numerical solution is presented for both the transient temperature and three-dimensional stress distribution in a railcar wheel resulting from a simulated emergency brake application. A computer program has been written for generating thermoelastic solutions applicable to wheels of arbitrary contour with temperature variations in both axial and radial directions. The results include the effect of shear stresses caused by the axial-radial temperature gradients and the high degree of boundary irregularity associated with this type of problem. The program has been validated by computing thermoelastic solutions for thin disks and long cylinders; the computed values being in good agreement with the closed form solutions. Currently, the computer program is being extended to general stress solutions corresponding to the transient temperature distributions obtained by simulated drag brake applications. When this work is completed, it will be possible to synthesize the thermal history of a railcar wheel and investigate the effects of wheel geometry in relation to thermal fatigue.

scholarly journals EFFECT OF THE TEMPORAL PROFILE OF THE FRICTION POWER ON THERMAL STRESSES DURING BRAKING

2017 ◽  
Author(s):  
A. A. Yevtushenko ◽  
M. Kuciej ◽  
K. Topczewska
Keyword(s):  
Heat Flow ◽  
Thermal Stresses ◽  
Temperature Fields ◽  
Frictional Heat ◽  
Transient Temperature ◽  
Flow Density ◽  
Temporal Profile ◽  
Friction Element ◽  
Friction Power ◽  
Brake Rotor

In this paper influence of the temporal profile of frictional heat flow density on the distributions of temperature and thermal stresses in a friction element during single braking was investigated. For this purpose a one-dimensional boundary-value heat conduction problem for a half-space body (which simulates a brake rotor) heated on the outer surface by the heat flux with different intensities was formulated and solved by means of Duhamel’s theorem. Solutions were obtained for ten temporal profiles of specific friction power, which are proportional to the intensity of frictional heat flow. Based on received transient temperature fields and Timoshenko’s model of thermal bending of a thick plate with unfixed edges, the analytical distributions of quasi-static thermal stresses in a friction element were found. Achieved solutions allow conducting numerical analysis of the distributions of temperature and thermal stresses in a brake rotor with different time profiles of the specific friction power.

Residual Thermal Stresses in a Fe3Al/Al2O3 Gradient Coating System

2008 ◽  
Vol 32 ◽  
pp. 71-74
Author(s):  
Jiang Ting Wang ◽  
Peter D. Hodgson ◽  
Jing De Zhang ◽  
Chun Hui Yang
Keyword(s):  
Plasma Spray ◽  
Thermal Stresses ◽  
Steel Substrate ◽  
Temperature Fields ◽  
Dominant Factor ◽  
Alumina Coating ◽  
Shear Stresses ◽  
Thermal Expansion Coefficients ◽  
Gradient Coating ◽  
Gradient Coatings

To combine the merits of both metals and ceramics into one material, many researchers have been studying the deposition of alumina coating using plasma spray on metal substrates. However, as the coatings are deposited at a high temperature, residual thermal stresses develop due to the mismatch of thermal expansion coefficients of the coating and substrate and these are responsible for the initiation and expansion of cracks, which induce the possible failure of the entire material. In this paper, the residual thermal-structural analysis of a Fe3Al/Al2O3 gradient coating on carbon steel substrate is performed using finite element modelling to simulate the plasma spray. The residual thermal stress fields are obtained and analyzed on the basis of temperature fields in gradient coatings during fabrication. The distribution of residual thermal stresses including radial, axial and shear stresses shows stress concentration at the interface between the coatings and substrate. The mismatch between steel substrate and composite coating is still the dominant factor for the residual stresses.

Residual Stresses in Strength Mismatched Welded Pipes

2017 ◽  
Author(s):  
Ali Mirzaee-Sisan ◽  
Junkan Wang
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Thermal Stresses ◽  
Structural Integrity ◽  
Welding Residual Stress ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Element Analysis ◽  
Girth Welds ◽  
Welded Pipe

It is commonly understood that residual stresses can have significant effects on structural integrity. The extent of such influence varies and is affected by material properties, manufacturing methods and thermal history. Welded components such as pipelines are subject to complex transient temperature fields and associated thermal stresses near the welded regions. These thermal stresses are often high in magnitude and could cause localized yielding around the deposited weld metal. Because of differential thermal expansion/contraction episodes, misfits are introduced into the welded regions which in turn generate residual stresses when the structure has cooled to ambient temperature. This paper is based on a recently completed Joint Industry Project (JIP) led by DNV GL. It briefly reviews published experimental and numerical studies on residual stresses and strength-mismatched girth welds in pipelines. Several Finite Element Analysis (FEA) models of a reeling simulation have been developed including mapping an initial axial residual stress (transverse to the weld) profile onto a seamless girth-welded pipe. The initial welding residual stress distribution used for mapping was measured along the circumference of the girth welds. The predicted residual stresses after reeling simulation was subsequently compared with experimental measurements.

Shorter Field Life in Power Cycling for Organic Packages

2006 ◽  
Vol 129 (1) ◽  
pp. 28-34 ◽  
Author(s):  
S. B. Park ◽  
Izhar Z. Ahmed
Keyword(s):  
Fatigue Life ◽  
Temperature Distribution ◽  
Flip Chip ◽  
Coefficient Of Thermal Expansion ◽  
Uniform Temperature ◽  
Transfer Coefficients ◽  
Solder Interconnects ◽  
Power Cycling ◽  
Plastic Ball ◽  
Accelerated Thermal Cycling

The importance of power cycling as a mean of reliability assessment was revisited for flip chip plastic ball grid array (FC-PBGA) packages. Conventionally, reliability was addressed empirically through accelerated thermal cycling (ATC) because of its simplicity and conservative nature of life prediction. It was well accepted and served its role effectively for ceramic packages. In reality, an assembly is subjected to a power cycling, i.e., nonuniform temperature distribution with a chip as the only heat source and other components as heat dissipaters. This non-uniform temperature distribution and different coefficient of thermal expansion (CTE) of each component make the package deform differently than the case of uniform temperature in ATC. Higher substrate CTE in a plastic package generates double curvature in the package deformation and transfers higher stresses to the solder interconnects at the end of die. This mechanism makes the solder interconnects near the end of die edge fail earlier than those of the highest distance to neutral point. This phenomenon makes the interconnect fail earlier in power cycling than ATC. Apparently, we do not see this effect (the die shadow effect) in ceramic packages. In this work, a proper power cycling analysis procedure was proposed and conducted to predict solder fatigue life. An effort was made for FC-PBGA to show the possibility of shorter fatigue life in power cycling than the one of ATC. The procedure involves computational fluid dynamics (CFD) and finite element analyses (FEA). CFD analysis was used to extract transient heat transfer coefficients while subsequent FEA–thermal and FEA–structural analyses were used to calculate temperature distribution and strain energy density, respectively.

A Method of Analysis of Transient Thermal Stresses in Thermorheologically Simple Viscoelastic Solids

1964 ◽  
Vol 31 (1) ◽  
pp. 47-53 ◽  
Author(s):  
K. C. Valanis ◽  
George Lianis
Keyword(s):  
Thermal Stresses ◽  
Perturbation Technique ◽  
Sufficient Conditions ◽  
Solid Sphere ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Temperature Dependent ◽  
Viscoelastic Solids ◽  
Temperature Dependent Properties ◽  
Transient Thermal

This paper is concerned with a perturbation technique suitable for the stress analysis of viscoelastic solids with temperature-dependent properties in the presence of nonuniform transient temperature fields. The problems of the infinite slab, solid sphere, and infinitely long viscoelastic cylinder are given solutions in the form of infinite series. Sufficient conditions for the convergence of the series are established.

On the Thermal Stresses Generated in Cylindrical Shells With Application to Gas Turbine Combustors

1982 ◽  
Author(s):  
H. A. Nied
Keyword(s):  
Gas Turbine ◽  
Thermal Stresses ◽  
Longitudinal Direction ◽  
Temperature Fields ◽  
Shear Stresses ◽  
Gas Turbine Combustor ◽  
Closed Form Solutions ◽  
Bending Stresses ◽  
Cooling Hole ◽  
Axisymmetric Temperature

The thermal stresses generated in a cylindrical shell due to axisymmetric temperature fields, which vary in the longitudinal direction, are examined by using an influence function formulation. Closed form solutions for the longitudinal, hoop and shear stresses are derived for any axially varying temperature distribution expressible by a Fourier expansion. The thermal stresses generated in a typical cylindrical gas turbine combustor cooled by periodically spaced circumferential bands of cooling holes are investigated using the derived solutions. It is shown that a critical pitch in the cooling hole spacing can create high bending stresses at the cooling holes which could contribute to thermal fatigue failure.

Experimental and Numerical Investigation of Temperature Fields in a Radial Turbine Wheel

2014 ◽  
Author(s):  
Mathias Diefenthal ◽  
Hailu Tadesse ◽  
Christian Rakut ◽  
Manfred Wirsum ◽  
Tom Heuer
Keyword(s):  
Temperature Distribution ◽  
Thermal Stresses ◽  
Commercial Vehicle ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Turbine Wheel ◽  
Numerical Investigations ◽  
Transient Temperature Distribution ◽  
Transient Temperature Field ◽  
Transient Operations

Due to increasing demands on the efficiency of modern Otto and Diesel engines, turbochargers are subjected to higher temperatures. In consequence rotor speed and temperature gradients in transient operations are more severe and therefore thermal and centrifugal stresses increase. To determine the life cycle of turbochargers more precisely, the exact knowledge of the transient temperature distribution in the turbine wheel is essential. To assess these temperature distributions, experimental and numerical investigations on a turbocharger of a commercial vehicle were performed. For this purpose, four thermocouples were applied on the shaft and the turbine wheel. The measured temperatures are used to determine the boundary conditions for the numerical calculations and to validate the results. In the numerical investigations three methods are used to determine and to analyse the transient solid body temperature distribution in respect of the fluid. The methods are compared and evaluated using the measured data. Based on the calculations the transient temperature field is discussed and conclusions concerning to the thermal stresses are drawn.

The Effect of Regulating Elements on Convective Heat Transfer along Shaped Heat Exchange Surfaces

2013 ◽  
Vol 34 (1) ◽  
pp. 5-16 ◽  
Author(s):  
Jozef Cernecky ◽  
Jan Koniar ◽  
Zuzana Brodnianska
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Cfd Simulation ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Temperature Fields ◽  
Transfer Coefficients ◽  
Heat Transfer Intensification ◽  
Heat Transfer Coefficients ◽  
Forced Air

Abstract The paper deals with a study of the effect of regulating elements on local values of heat transfer coefficients along shaped heat exchange surfaces with forced air convection. The use of combined methods of heat transfer intensification, i.e. a combination of regulating elements with appropriately shaped heat exchange areas seems to be highly effective. The study focused on the analysis of local values of heat transfer coefficients in indicated cuts, in distances expressed as a ratio x/s for 0; 0.33; 0.66 and 1. As can be seen from our findings, in given conditions the regulating elements can increase the values of local heat transfer coefficients along shaped heat exchange surfaces. An optical method of holographic interferometry was used for the experimental research into temperature fields in the vicinity of heat exchange surfaces. The obtained values correspond very well with those of local heat transfer coefficients αx, recorded in a CFD simulation.

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