bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinear Dynamic Analysis of Surface Mount Interconnects: Part I—Theory
Authors: Basaran C. , Chandaroy R.
Published: February 2008

Solder joints are commonly used in surface mount technology microelectronics packaging. It is well known that the dominant failure mode for solder joints is thermal fatigue. When semiconductor devices are used in a vibrating environment, such as in automotive and military applications, dynamic stresses contribute to the failure mechanism and in certain circumstances they can become the dominant failure cause. In this paper a unified constitutive model for Pb40/Sn60 solder joints is developed and then implemented in a finite element dynamic analysis procedure. The purpose of the material model and the implementation is to study the contribution of vibration induced strains to the fatigue life of solder interconnects in low cycle and high cycle fatigue. The proposed material model, which is based on the disturbed state concept (DSC), is used for a dynamic analysis of a solder joint in the following paper, Part II, Basaran and Chandaroy (1998).
Integrated Thermal Analysis of Natural Convection Air Cooled Electronic Enclosure
Authors: Tang L. , Joshi Y. K.
Published: February 2008

In the present paper, a methodology is described for the integrated thermal analysis of a laminar natural convection air cooled nonventilated electronic system. This approach is illustrated by modeling an enclosure with electronic components of different sizes mounted on a printed wiring board. First, a global model for the entire enclosure was developed using a finite volume computational fluid dynamics/heat transfer (CFD/CHT) approach on a coarse grid. Thermal information from the global model, in the form of board and component surface temperatures, local heat transfer coefficients and reference temperatures, and heat fluxes, was extracted. These quantities were interpolated on a finer grid using bilinear interpolation and further employed in board and component level thermal analyses as various boundary condition combinations. Thus, thermal analyses at all levels were connected. The component investigated is a leadless ceramic chip carrier (LCCC). The integrated analysis approach was validated by comparing the results for a LCCC package with those obtained from detailed system level thermal analysis for the same package. Two preferred boundary condition combinations are suggested for component level thermal analysis.
Analytical Derivation of the Self-Alignment Motion of Flip Chip Soldered Components
Authors: van Veen N.
Published: February 2008

A component aligned through the use of liquid solder bumps behaves like a mechanical oscillator system. The force constants for liquid solder bumps are derived analytically for simple model systems as well the damping factor and the resonance spectrum. It appears that for practical bump sizes the force constant in the vertical direction is an order of magnitude larger than the horizontal one. The damping factor is small and the system can easily be brought into resonance. From the derivation of the force constants combined with the dissociation energy a Morse potential can be constructed depicting the asymmetry in the potential energy curve.
Unsteady Wire Sweep Due to Transfer Molding in a 160L QFP Package
Authors: Chai H. , Zohar Y.
Published: February 2008

Wire sweep has been recognized as one of the major defects in encapsulation of electronic components by transfer molding. The phenomenon is very complicated as it is sensitive to a large number of parameters. In this experimental work, where a 160L QFP package used as the test vehicle, the detailed time-dependent wire displacement is measured for the following two different flow initial conditions: (i) the wire is immersed in the liquid and is displaced due to the acceleration of the flow from rest to the steady-state velocity, and (ii) the wire is surrounded by the ambient air and is displaced first due to the passage of the liquid front and then due to the hydrodynamic load. Significant differences have been observed between the two cases, with important implications for analytical and numerical studies of wire sweep.
Natural Convection Cooling of Vertical Rectangular Channels in Air Considering Radiation and Wall Conduction
Authors: Hall D. A. , Vliet G. C. , Bergman T. L.
Published: February 2008

Temperature distributions on the surfaces of vertical channels formed by parallel plates heated uniformly and symmetrically and cooled by conduction, radiation, and natural convection in air are determined numerically and experimentally. Effects of wall separation, thickness, thermal conductivity, and emissivity on the wall temperature distribution are determined. Both cases of controlled and uncontrolled channel edge leading and exit edge temperatures are examined. Optimum channel widths and correlations for the maximum wall temperature rise are offered for both the controlled and uncontrolled edge temperature conditions.
Failure Estimation of Semiconductor Chip During Wire Bonding Process
Authors: Ikeda T. , Miyazaki N. , Kudo K. , Arita K. , Yakiyama H.
Published: February 2008

Wire bonding, a process of the connection between a semiconductor chip and a lead frame by a thin metal wire, is one of the important processes of electronic packaging. This paper presents failure estimation of a silicon chip and a GaAS chip during a gold wire bonding process. The gold wire bonding process is carried out by pressing a gold ball made at a tip of the gold wire on a semiconductor chip and vibrating it by ultrasonic. High contact pressure is useful for shortening the process cycle, but it sometimes causes failure of the semiconductor chip. Elastic-plastic large deformation contact analyses are performed and the distributions of the stresses in these semiconductor chips are investigated. The possibility of failure of a semiconductor chip under usual wire bonding pressure is pointed out only for a GaAs chip.
Modeling the Deformation Behavior of a Sn-Pb Solder Alloy Using the Simplified Viscoplasticity Theory Based on Overstress (VBO)
Authors: Maciucescu L. , Sham T.-L. , Krempl E.
Published: February 2008

Stress-strain diagrams showing the influence of strain rate at five different high homologous temperatures for a Sn-Pb solder alloy are used to determine the material parameters in a minimal version of the viscoplasticity theory based on overstress (VBO), accounting for static recovery effects. VBO is a “unified” state variable theory that does not use a yield surface and has three state variables with appropriate growth laws. It is shown that the effects of strain rate can be modeled well by this theory that requires eight material parameters to describe the inelastic behavior. The behavior in tensile and cyclic strain-controlled loadings, ratcheting, and creep is predicted. The results compare very well with the experiments for tensile and cyclic loading. For the other tests no comparisons were made due to the lack of proper experimental data. The model is formulated in tensorial form and can be used for inelastic stress analyses of solder joints.
Wire Sweep Due to Transfer Molding in a 160L QFP Package Under Steady-State Conditions
Authors: Chai H. , Zohar Y.
Published: February 2008

Wire sweep has been recognized as a critical process defect which can result in device failure. The phenomenon is very complicated as it is sensitive to a large number of parameters. In this experimental work, the influence of some of the more important factors is investigated. These parameters include fluid-flow speed, wire-bond density, mold cavity height, and mold vent size. A 160L QFP package bonded with gold wires in a transparent mold is used as the test vehicle.
Hygrothermal Fracture Analysis of Plastic IC Package in Reflow Soldering Process
Authors: Lee Kang Yong , Lee Taek Sung
Published: February 2008

The purpose of this paper is to evaluate the delamination and fracture integrity of the integrated circuit (IC) plastic package under hygrothermal loading by the approaches of stress analysis and fracture mechanics. The plastic small outline J-lead (SOJ) package with a dimpled diepad under the reflow soldering process of infrared (IR) heating type is considered. On the package without a crack, the stress variation according to the change of the design variables such as the material and shape of the package is calculated and the possibility of delamination is considered. For the model fully delaminated between the chip and the dimpled diepad, J-integrals are calculated for the various design variables and the fracture integrity is discussed. From the results, optimal values of design variables to prevent the delamination and fracture of the package are obtained. In this study, the finite difference method (FDM) program to obtain the vapor pressure from the content of moisture absorbed into the package is developed.
Analysis of Solder Paste Release in Fine Pitch Stencil Printing Processes
Authors: Rodriguez G. , Baldwin D. F.
Published: February 2008

Advanced electronics packaging technologies such as chip scale packages, fine pitch ball grid arrays, and flip chip are pushing solder paste stencil printing to the limit. In order to achieve solder print deposits of the sizes required for emerging electronic packaging technology, a rigorous understanding of the process is required. This paper seeks to expand our understanding of the physical characteristics of stencil printing specifically focusing on the solder paste release process based on experimental and analytical approaches. First, designed experiments were conducted to identify the main process variables affecting final print quality. An in-situ measurement system using a high speed imaging system monitored the solder paste release process. Based on experimental observations, different modes of solder paste release and their corresponding mechanisms were identified. A model was developed to predict print quality for fine pitch applications. The proposed model was experimentally verified showing good agreement with measured values for fine pitch and very fine pitch printing. It was found that the cohesive and adhesive forces acting on the paste tend to govern the release process rather than the viscous and inertial forces.
Interior Stress for Axisymmetric Abrasive Indentation in the Free Abrasive Machining Process: Slicing Silicon Wafers With Modern Wiresaw
Authors: Yang F. , Kao I.
Published: February 2008

In wiresaw manufacturing processes, such as those in slicing silicon wafers for electronics fabrication, abrasive slurry is carried by high-speed wire (5 to 15 m/s), which exerts normal load to the surface via hydrodynamic effects and bow of taut wire. As a result, the abrasives carried by slurry are constrained to indent onto and roll over the surface of substrate. In this paper, the axisymmetric indentation problem in the free abrasive machining (FAM) is studied by modeling a rigid abrasive of different shapes pushing onto an elastic half space. Based on the harmonic property of dilatation, the closed-form solution of stress distribution inside the cutting material for three different indentation processes in common FAM process are presented: cylindrical and conical abrasives as well as uniform pressure distribution. Along the symmetrical axis, von-Mises stress is two times larger than that of local maximum shear stress for all three indentation conditions. The von-Mises stress is infinity at the contact point for sharp pointed indentation, a location of crack initiation and nucleation. For indentation by abrasive of flat surface, which also can be provided by the localized effects due to the hydrodynamic pressure acting on the surface, both the von-Mises and local maximum shear stress reach maximum underneath the contact zone.
Three-Dimensional Versus Two-Dimensional Finite Element Modeling of Flip-Chip Packages
Authors: Yao Q. , Qu J.
Published: February 2008

In this study, both two-dimensional and three-dimensional finite element analyses were used to study the stress distribution in and deflection of the flip chip assembly under thermal loading. It is found that the three-dimensional results compared favorably with experimental measurements, while the two-dimensional results consistently overestimate both stresses and deflection. Among the two-dimensional models, the plane stress assumption seems to yield results closer to the full three-dimensional predictions. Furthermore, three-dimensional models were used to investigate the effect of printed wiring board size on the overall deflection of the flip-chip assembly. This size effect of the printed wiring board has significant implications on the design of multi-chip modules. The results indicate that a square array placement pattern is preferable to a staggered array for multiple chip modules in order to reduce mechanical interaction between chips. For square arrays, such mechanical interaction between chips can be neglected when the minimum distance between adjacent chips is more than 2 times the chip size.
Numerical and Experimental Prediction of Transitional Characteristics of Flow and Heat Transfer in an Array of Heated Blocks
Authors: Asako Y. , Yamaguchi Y. , Faghri M.
Published: February 2008

Three-dimensional numerical analysis, for transitional characteristics of fluid flow and heat transfer in periodic fully developed region of an array of the heated square blocks deployed along one wall of the parallel plates duct, is carried out by using Lam-Bremhorst low-Reynolds-number two equation turbulence model. Computations were performed for Prandtl number of 0.7, in the Reynolds number range of 200 to 2000 and for two sets of geometric parameters characterizing the array. The predicted transitional Reynolds number is lower than the value for the parallel plate duct and it decreases with increasing the height above the module. Experiments were also performed for pressure drop measurements and for flow visualization and the results were compared with the numerical predictions.
An Analytical Comparison of Adsorption and Vapor Compression Air Conditioners for Electric Vehicle Applications
Authors: Aceves S. M.
Published: February 2008

This paper shows an analysis of the applicability of an adsorption system for electric vehicle (EV) air conditioning. Adsorption systems are designed and optimized to provide the required cooling for four combinations of vehicle characteristics and driving cycles. The resulting adsorption systems are compared with vapor compression air conditioners that can satisfy the cooling load. The objective function is the overall system weight, which includes the cooling system weight and the weight of the battery necessary to provide energy for air conditioner operation. The system with the minimum overall weight is considered to be the best. The results show the optimum values of all the variables, as well as temperatures and amounts adsorbed, for the adsorption and desorption processes. The results indicate that, for the conditions analyzed in this paper, vapor compression air conditioners are superior to adsorption systems, not only because they are lighter, but also because they have a higher COP and are more compact.
Simultaneous Measuring Method for Both Volumetric Flow Rates of Air-Water Mixture Using a Turbine Flowmeter
Authors: Minemura K. , Egashira K. , Ihara K. , Furuta H. , Yamamoto K.
Published: February 2008

A turbine flowmeter is employed in this study in connection with offshore oil field development, in order to measure simultaneously both the volumetric flow rates of air-water two-phase mixture. Though a conventional turbine flowmeter is generally used to measure the single-phase volumetric flow rate by obtaining the rotational rotor speed, the method proposed additionally reads the pressure drop across the meter. After the pressure drop and rotor speed measured are correlated as functions of the volumetric flow ratio of the air to the whole fluid and the total volumetric flow rate, both the flow rates are iteratively evaluated with the functions on the premise that the liquid density is known. The evaluated flow rates are confirmed to have adequate accuracy, and thus the applicability of the method to oil fields.
Experiments in Thermal Spallation of Various Rocks
Authors: Williams R. E. , Potter R. M. , Miska S.
Published: February 2008

The greatest limitation of the spallation process is its inability to spall (or to consistently spall) many rocks encountered in petroleum drilling and mining operations. The New Mexico Institute of Mining and Technology has conducted a series of experiments to investigate the possibility of expanding the use of the spallation process to the penetration of rocks generally considered not to be spallable. The methods used during this work were 1) spalling at temperatures below that produced by the stoichiometric burning of fuel oil and air, and 2) spalling by alternately heating and quenching the rock surfaces. No success was experienced in spalling at the lower temperatures, but initial tests showed the alternate heating and chilling system to be successful, particularly in penetrating travertine limestone. However, continued testing indicated that, unless the rocks are extremely uniform in composition, spalling will result in highly irregular holes or holes that cannot be directionally controlled.
An Appraisal of One-Dimensional Analytical Models for the Packed Bed Thermal Storage Systems Utilizing Sensible Heat Storage Materials
Authors: Adebiyi G. A. , Chenevert D. J.
Published: February 2008

This article gives an appraisal of existing analytical one-dimensional models for the packed bed thermal energy storage (TES) systems utilizing sensible heat storage (SHS) materials. The models include that of Schumann, which is for separate phases, but does not include axial conductivity (or dispersion) in the bed, and the single-phase model of Riaz which includes axial dispersion. An alternative axial conductivity model is proposed which compares well with the Schumann model when axial dispersion is negligible, but otherwise caters adequately for axial dispersion at the low Peclet number condition.
Comprehensive Modeling of Turbulent Flames With the Coherent Flame-Sheet Model—Part II: High-Momentum Reactive Jets
Authors: Beeri Z. , Blunsdon C. A. , Malalasekera W. M. G. , Dent J. C.
Published: February 2008

This paper describes the application of computational fluid dynamics (CFD) to the prediction of the characteristics of high-momentum vertical and horizontal flames in ambient air flows. The KIVA-II code has been modified by extending the range of boundary conditions and by the addition of the following: a version of the coherent flame-sheet model, Tesner’s soot generation and Magnussen’s soot oxidation model, and an implementation of the discrete transfer radiation model. To assess the accuracy of the complete model for prediction purposes, results are compared with experimental data. Predictions of temperature and flame profiles are in good agreement with data while predictions of radiative heat transfer are not entirely satisfactory.
Environmental Hazards due to Rupture of a Liquefied Propane Pipeline
Authors: Badr O. A. , El-Sheikh H. A.
Published: February 2008

Accidental leakages of liquefied propane from high-pressure pipelines may occur despite the use of sophisticated safety equipment and following strict monitoring procedures. Environmental impact of steady and transient leakages were considered from toxicity and flammability viewpoints for two specific scenarios of full pipe ruptures. For each case, calculated mass flow rate, velocity, and temperature of leaking gas were utilized in an EPA-based dispersion model to predict the ground level concentration profiles in the downwind and crosswind directions. For the specific pipeline conditions considered here, the first scenario of a nonjet release (a cloud) produced steady toxic and flammable zones which were about 20 times bigger than those produced in the transient case. The second scenario of a free vertical jet resulted in the formation of a flammable vertical plume, while at ground level it did not produce flammable nor toxic zones. A parametric study of the first scenario confirmed the expected effects of both the gas release time and the atmospheric stability on the size of the dangerous zones. Within the typical range, the wind speed was found to have opposite effects for steady and transient releases. For a steady release, the dangerous zone was wider for slower winds and vice versa for a transient case. Moreover, the size of the dangerous zone was found to be an exponential function of the pipe diameter, while the effect of the initial pipe pressure was insignificant.
Computer Simulation of a High-Temperature Thermal Energy Storage System Employing Multiple Families of Phase-Change Storage Materials
Authors: Adebiyi G. A. , Hodge B. K. , Steele W. G. , Jalalzadeh-Azar A. , Nsofor E. C.
Published: February 2008

Previous work by one of the authors entailed modeling of a packed bed thermal energy storage system utilizing phase-change materials (PCM). A principal conclusion reached is that the use of a single family of phase-change storage material may not in fact produce a thermodynamically superior system relative to one utilizing sensible heat storage material. This paper describes the model constructed for the high-temperature thermal energy storage system utilizing multiple families of phasechange materials and presents results obtained in the exercise of the model. Other factors investigated include the effect on system performance due to the thermal mass of the containment vessel wall and variable temperature of the flue gas entering the packed bed during the storage process. The results obtained indicate efficiencies for the system utilizing the five PCM families exceeding those for the single PCM family by as much as 13 to 26 percent. It was also found that the heat transfer to the containment vessel wall could have a significant detrimental effect on system performance.
Adiabatic Losses in Stirling Refrigerators
Authors: Bauwens L.
Published: February 2008

The Stirling cycle has been used very effectively in cryocoolers; but efficiencies relative to the Carnot limit are typically observed to peak for absolute temperature rations of about two, which makes it less suitable for low-lift refrigeration. The adiabatic loss appears to be responsible for poor performance at small temperature differences. In this paper, adiabatic losses are evaluated, for a temperature ratio of 2/3, taking into account the effect of phase angle between pistons, of volume ratio, of the distribution of the dead volume necessary of reduce the volume ration, and of the distribution of displacement between expansion and compression spaces. The study is carried out numerically, using an adiabatic stirling engine model in which cylinder flow is assumed to be stratified. Results show that the best location for the cylinder dead volume is on the compression side. Otherwise, all strategies used to trade off refrigeration for coefficient of performance are found to be roughly equivalent.
On the Scaling of the Visible Lengths of Jet Diffusion Flames
Authors: Li X.
Published: February 2008

Length of jet diffusion flames is of direct importance in many industrial processes and is analyzed by applying scaling method directly to the governing partial differential equations. It is shown that for jet-momentum-dominated diffusion flames, when the buoyancy effects are neglected, the flame length normalized by the burner exit diameter increases linearly with the Reynolds number at the burner exit in the laminar burning regime and decreases in inverse proportion to the Reynolds number in the transitional regime. For turbulent diffusion flames, the normalized flame lengths are independent of the burner exit flow conditions. It is further found that for vertical upward flames, the buoyancy effect increases the flame length in the laminar and transitional regime and reduces the length in the turbulent regime; while for vertical downward flames, the buoyancy effect decreases the flame length in the laminar and transitional regime and increases the length in the turbulent regime, provided that jet momentum is dominated, and there is no flame spreading out and then burning upward like a downward-facing pool fire. Hence, for turbulent flames the flame lengths depend on the Froude number, Fr, and increase (or decrease) slightly as Fr increases for upward (or downward) flames. By comparison, it is found that the foregoing theoretical results are in good agreement with the experimental observations reported in literature.
Effect of Burner Geometry on the Blowout Limits of Jet Diffusion Flames in a Co-Flowing Oxidizing Stream
Authors: Papanikolaou N. , Wierzba I.
Published: February 2008

The effects of changes in the jet nozzle geometry, i.e., nozzle shape and lip thickness, on the blowout limits of jet diffusion flames in a co-flowing air stream were experimentally investigated for a range of co-flow air stream velocities. Circular and elongated nozzles of different axes rations were employed. Preliminary results showed that nozzles with low major-to-minor axes ratios improved, while high ratios reduced, the blowout limit of attached flames compared with that for an equivalent circular nozzle. The nozzle shape had no apparent influence on the blowout limits lifted flames and the limiting stream velocity. The experimental blowout limits of lifted flames were found to be a function of the co-flowing stream velocity and jet discharge area. On the other hand, the stability of attached flames was a function of the co-flowing stream velocity, jet discharge area as well as the nozzle shape. The effect of premixing a fuel with the surrounding air was also studied. Generally, the introduction of auxiliary fuel into the surrounding stream either increased or decreased the blowout limit depending on the type of flame stabilization mechanism prior to blowout. The stability mechanism of the flame was found to be a function of the co-flow stream velocity and the auxiliary fuel employed.
An Investigation of Lean Combustion in a Natural Gas-Fueled Spark-Ignited Engine
Authors: Gupta M. , Bell S. R. , Tillman S. T.
Published: February 2008

Natural gas has been used extensively as an engine fuel in gas pipeline transmission applications and, more recently, as a fuel for transportation applications including both light-duty and heavy-duty vehicles. The objective of this work was to investigate the performance and emission characteristics of natural gas in an original equipment manufacturer (OEM), light-duty, spark-ignited engine being operated in the lean fueling regime and compare the operation with gasoline fueling cases. Data were acquired for several operating conditions of speed, throttle position, air-fuel equivalence ratio, and spark timing for both fuels. Results showed that for stoichiometric fueling, with a naturally aspirated engine, a power loss of 10 to 15 percent can be expected for natural gas over gasoline fueling. For lean operation, however, power increases can be expected for equivalence ratios below about φ = 0.80 with natural gas fueling as compared to gasoline. Higher brake thermal efficiencies can also be expected with natural gas fueling with maximum brake torque (MBT) timings over the range of equivalence ratios investigated in this work. Coefficient of variation (COV) data based on the indicated mean effective pressure (IMEP) demonstrated that the engine is much less sensitive to equivalence ratio leaning for natural gas fueling as compared to gasoline cases. The lean limit for a COV of 10 percent was about φ = 0.72 for gasoline and φ = 0.63 for natural gas. Lean fueling resulted in significantly reduced NOx levels where a lower plateau for NOx concentrations was reached at φ near or below 0.70, which corresponded to about 220 ppm. For natural gas fueling, this corresponded to about 1.21 gm/(kW-h). Finally, with MBT timings, relatively short heart release durations were obtained for lean fueling with natural gas compared to gasoline.
Development of an Experimentally Flexible Facility for Mixing-Combustion Interactions in Supersonic Flow
Authors: Segal C. , Young C. D.
Published: February 2008

A new experimental facility has been designed, built and calibrated to support research topics involving supersonic mixing and combustion and will be used to investigate: 1) molecular level mixing; 2) mixing-combustion coupling effects for gaseous and liquid fuels; and 3) atomization, droplet break-up, mixing, and combustion of high-energy/high-density slurry fuels in a supersonic airstream. The facility simulates flight enthalpies corresponding to altitudes between 26 and 36 km and flight Mach numbers up to 4.755. The major features of this facility are the geometric flexibility of the test section configuration, of the fuel injection, and of the experimental conditions, enabling the investigation of a broad range of topics. Parallel and transverse injection, independently controlled in four regions, is available. The construction of the test section is modular and the entrance Mach numbers can be varied between 1.6 and 3.6. An experimental program to define the test flow at the entrance of the facility’s test section is presented with emphasis on the test section entrance ture distribution and calibration. Selected research topics currently being investigated are summarized to highlight the usefulness of the present facility.
Thermomechanical Durability Analysis of Flip Chip Solder Interconnects: Part 1—Without Underfill
Authors: Darbha K. , Okura J. H. , Dasgupta A.
Published: February 2008

A generalized multi-domain Rayleigh-Ritz (MDRR) approach developed by Ling and Dasgupta (1995), is extended in this paper, to obtain the stress field in flip chip solder interconnects, under cyclic thermal loading. Elastic, Plastic and time-dependent visco-plastic analysis is demonstrated on flip chip solder interconnects. The method has been applied to other surface-mount interconnects in the past such as J-lead (Ling and Dasgupta, 1996a) and ball-grid joints (Ling and Dasgupta, 1997). The analysis results for the J-lead and ball grid joints have confirmed that the MDRR technique is capable of providing stress-strain hysteresis with adequate accuracy, at a fraction of the modeling effort required for finite element model generation and analyses. Nonlinear viscoplastic stress analysis results for flip chip interconnects without underfill are presented in this paper. The fatigue endurance of the solder joints is assessed by combining results from this stress analysis model with an energy-partitioning damage model (Dasgupta et al., 1992). The life predicted by the analytical damage model is compared with experimental results.
Thermoelastic Modeling of a PWB With Simulated Circuit Traces Subjected to Infrared Reflow Soldering With Experimental Validation
Authors: Polsky Y. , Ume I. C.
Published: February 2008

A bare, four copper layer printed wiring board with simple trace patterns was built for modeling and experimental validation purposes. In-plane elastic properties of the core materials in the board were measured as a function of temperature. Thermoelastic lamination theory was utilized to predict the warpage of the board when subjected to an infrared reflow process, with emphasis on studying the influence of thermal gradients through the board, its support conditions and CTE differential on the warpage process. Board layers with traces were approximated with quasi-homogeneous effective properties obtained using micromechanics theory. An experimental system that employs the shadow moird technique in a simulated infrared reflow environment was used to evaluate the warpage for comparison to modeled results.
Investigation of a New Lead Free Solder Alloy Using Thin Strip Specimens
Authors: Ren W. , Qian Z. , Lu M. , Liu S. , Shangguan D.
Published: February 2008

The thermomechanical behaviors of a new lead free solder and eutectic 63Sn37Pb are investigated in this paper. A series of tests including tensile, creep, and fatigue, are carried out on a computer controlled 6-axis mini-fatigue tester. The thin strip specimen is used in this research, which is specially designed and verified to be suitable for the testing of solder alloys and comparable to the data from the literature. Based on the experimental study, the new lead free solder alloy shows very attractive characteristics and may have potential applications in electronics packaging products.
Consideration of Parameter Scattering in Thermo-Mechanical Characterization of Advanced Packages
Authors: Winkler T. , Schubert A. , Kaulfersch E. , Michel B.
Published: February 2008

Much progress has been made in the simulation and verification of the thermo-mechanical behavior of plastic packages. On the other hand, until now there is a lack in the consideration of the scatter or uncertainty, respectively, of certain characteristics. A comparatively large scatter of local material properties or random geometrical imperfections can often be observed within the material compounds of electronic packages. The partial randomness of certain input parameters creates uncertainties in the finite element determination of mechanical quantities which are provided for thermo-mechanical reliability optimization and life time prediction. In the following the STOFEM stochastic finite element approach based on perturbation theory is applied as a part of the finite element simulation. It is used to find out some additional effects arising from uncertainties in the modeling, slightly varying parameters or probabilistic influences, respectively. In a second part of the paper, another approach to the consideration of random variations is discussed. It is based on the randomization of initially deterministic relations.
Thermal Destruction of Solid Wastes
Authors: Gupta A. K.
Published: February 2008

The United States generates the largest amount of solid waste per person in the world. The old practice of direct landfilling and storage is receiving greater public resistance and is attributing to the search for alternative disposal methods. The evergrowing problem of solid wastes requires environmentally benign and good public acceptance for the safe and ultimate disposal of the various kinds of solid wastes. Incineration and various kinds of mass burn-type systems have been used to reduce the volume and mass of the wastes, which can be characterized by their operational temperature. In all types of incineration systems, different kinds of gas clean-up devices are used to meet the local, state, and federal regulations for the gases before being released into the environment. A major concern over these systems have been in the by-products produced from these systems during their normal design and off-design point of operation. Indeed, the by-products generated from some incineration systems, under certain operational conditions, can be a health hazard and the solid residue may be leachable. Recent trends in advanced thermal destruction systems are described which can destroy the solid waste to the molecular level. Advanced systems can be designed to meet almost any emission standards. The use of oxygen-enriched air in place of air for the combustion of gases released from the solid waste reduces the amount of effluent gas, and, hence, the reduced size and cost of the gas clean-up system. The use of an excess enthalpy system offers attractive benefits in which the energy released from the waste is recycled back into the system under controlled conditions with the final desired objectives of reduced emissions, higher efficiency, and lower costs. Thermal destruction of solid wastes using advanced techniques makes good technical, environmental, economical, and human health and safety. The issues concerning recyclability, life cycle integration, and health effects from incineration are only expected to grow in the future.
Incorporation of Phase-Change Materials Into a Ground Thermal Energy Storage System: Theoretical Study
Authors: Rabin Y. , Korin E.
Published: February 2008

An investigation of a ground thermal energy storage system, which includes storage units containing phase-change materials (PCM), is presented. This study is related to a large-diameter helical heat exchanger, which is placed vertically in the ground. The PCM storage units under consideration have a cylindrical shell shape and are located inside and/or outside the helix. A modified numerical scheme for the Solution of heat transfer in the ground, in the PCM units, and within the heat exchanger pipe, is presented. The theoretical results show that the thermal diffusivity of the PCM dominates the thermal performance of the system. Incorporation of PCM storage units containing paraffin wax results in a reduction of the thermal efficiency in comparison with a system not containing these units. However, incorporation of PCM having the same thermal diffusivity as of the soil results in a significant improvement of the thermal performance.
A New Approach for Determining In-Situ Rock Strength While Drilling
Authors: Hoberock L. L. , Bratcher G. J.
Published: February 2008

A new method is developed for determining rock strength while drilling with a tri-cone roller bit. The technique employs the well-known “drill-off” test, using commonly measured drilling data, and does not require knowledge of drill bit parameters. The method was evaluated with drill-off test data collected from the Gas Research Institute’s SFE (staged field experiment) well no. 4 and compared with calculated in-situ compressive rock strengths provided by Hareland (1992). The results indicate that the proposed approach produces reasonable results and is easily implemented.
Operational Strategy of a Cogeneration System Under a Complex Utility Rate Structure
Authors: Yokoyama R. , Ito K.
Published: February 2008

An operational planning problem for a cogeneration system is discussed under a complex utility rate structure which imposes demand charges due to total utility consumption over a specified period as well as demand and energy charges due to hourly utility consumption. Operational strategy of constituent equipment and contract demands for total utility consumption are assessed so as to minimize the operational cost over the period subject to energy demand requirement. This problem is formulated as a large-scale mixed-integer linear programming (MILP) one, and it is solved efficiently by a revised decomposition method for MILP problems with block angular structure. Through a numerical study on a gas engine-driven cogeneration system installed in a hotel or an office building, the effect of rate structure on operational strategy is clarified.
Performance of a High-Solidity Wells Turbine for an OWC Wave Power Plant
Authors: Gato L. M. C. , Warfield V. , Thakker A.
Published: February 2008

The paper describes an experimental investigation, and presents the results of the aerodynamic performance of a high-solidity Wells turbine for a wave power plant. A monoplane turbine of 0.6 m rotor diameter with guide vanes was built and tested. The tests were conducted in unidirectional steady airflow. Measurements taken include flow rate, pressure drop, torque, and rotational speed, as well as velocity and pressure distributions. Experimental results show that the presence of guide vanes can provide a remarkable increase in turbine efficiency.
Thermal Destruction Behavior of Plastic and Nonplastic Wastes in a Laboratory-Scale Facility
Authors: Gupta A. K. , Ilanchezhian E. , Keating E. L.
Published: February 2008

Experimental and theoretical studies are presented from a laboratory-scale thermal destruction facility on the destruction behavior of surrogate plastic and nonplastic solid wastes. The nonplastic waste was cellulosic, while the plastic waste contained compounds, such as polyethylene, polyvinyl chloride, polystyrene, polypropylene, nylon, rubber, and polyurethane, or any of their desired mixtures. A series of combustion tests was performed with samples containing varying composition test was performed with samples containing varying composition of plastic and nonplastic. Experimental results are presented on combustion parameters (CO, excess air, residence time) and toxic emissions (dioxin, furan, metals). Equilibrium thermochemical calculations are presented on the thermal destruction behavior of samples under conditions of pyrolysis, combustion, and pyrolysis followed by combustion. Special interest is on the effect of waste properties and input operational parameters on chemistry and product composition. STANJAN and SOLGASMIX computer codes were used in the chemical equilibrium study. Analysis and interpretation of the data reveal the effect of waste feed composition on combustion parameters and dioxin, furan, and metals emission. Equilibrium calculation results are used to describe the experimentally observed trends for the thermal destruction behavior of these wastes. The results show significant influence of plastic on combustion characteristics, and dioxin, furan, and metals emission.
Combined Cycle Gas Turbine Power Plant With Coal Gasification and Solid Oxide Fuel Cell
Authors: Lobachyov K. , Richter H. J.
Published: February 2008

The United States has extensive coal resources; thus, it is important to consider coal as a fuel for electric power production. This work presents a theoretical study of a novel high-efficiency coal-fired power plant. In the proposed combined cycle power plant, the Conoco coal gasification process is linked with solid oxide fuel cells (SOFC) and state-of-the-art gas turbines. The overall efficiency of such a plant can be around 60 percent, considering realistic heat, pressure, and other losses in the different components of the plant. If an additional steam turbine is incorporated, the overall efficiency can be increased to about 62 percent.
Analysis and Design of an Air-Cycle Microclimate Cooling Device
Authors: Rahman M. M.
Published: February 2008

This paper presents an innovative concept of using air-cycle technology for the development of a microclimate cooling device for use by soldiers in the battlefield. The device is an integrated heat engine and heat pump which supplies air at a prescribed temperature and humidity for personal cooling of a soldier wearing protective ensembles, generates electrical energy to power communication equipment, and produces drinking water by condensing atmospheric moisture which may be very useful in desert warfare. It consists of a centrifugal compressor, two turbines or expanders, a combustion chamber, three heat exchangers, a water separator, and an electric generator. Atmospheric air is used as the working fluid in both the engine and cooling loops and diesel is used as the fuel for combustion. A detailed thermodynamic analysis and design optimization was performed. It was found that the system efficiency increases with operating pressure ratio, attains a maximum, and decreases with further increase of pressure ratio. The system efficiency was found to be also dependent on the air-fuel ratio, and the maximum efficiency was found to occur at a specific air-fuel ratio, for any given pressure ratio. The optimum operating condition determined from the thermodynamic analysis was used to outline a detailed design of the system.
Effect of Torsion on Stability, Dynamic Forces, and Vibration Characteristics in Drillstrings
Authors: Elsayed M. A. , Dareing D. W. , Vonderheide M. A.
Published: February 2008

Traditionally, the analysis of stability in drillstrings is based on longitudinal vibrations only. However, field experience indicates the presence of torsional effects in the form of modulations in longitudinal vibrations. Moreover, torsional dynamic forces are significant and lead to joint problems during drilling. In this paper, we discuss the effect of torsional vibrations on the stability and both longitudinal and torsional forces in drillstrings. Using a model of a typical drillstring that incorporates both longitudinal and torsional multi-degree of freedom, we develop the equations governing displacements and forces at any joint. Using time simulation techniques, we obtain the stability diagram and calculate the dynamic forces at any joint as a function of time. We finally show the effect of torsion on the nature of vibrations through frequency analysis, a technique that is useful in the interpretation of field measurements under various drilling conditions.
A Review of Multiphase Flow Through Chokes
Authors: Rastoin S. , Schmidt Z. , Doty D. R.
Published: February 2008

Three comprehensive mechanistic models (Ashford and Pierce, 1974; Sachdeva et al., 1986; Perkins, 1990) dealing with multiphase flow through chokes have been studied. Their common purpose is to determine the flow through a choke under both critical and subcritical flow. Except for their initial assumptions, these three models are basically the same and all are based on the energy equation. Performance of the model developed by Perkins (1990) was the best in a comparison test against a database of 1239 points. The other two models deviated up to 40 percent when compared to the Perkins model for large values of choke to pipe size ratios. A very important application of these models is in prediction of the pressure either upstream or downstream of the choke, given the flow rate through the choke and the known pressure. Pressure predictions against the flow direction (i.e., upstream of the choke) were foundto be in very good agreement with measurements. Not more than 13 percent average absolute error and 17 percent standard deviation were observed. Similar errors were reported for the downstream pressure predictions for data in the subcritical flow regime. However, downstream pressure predictions for data in the critical flow regime gave large errors, up to 40 percent, which were expected.
Mixed Convection in Non-Newtonian Fluids Along a Horizontal Plate in a Porous Medium
Authors: Kumari M. , Gorla Rama Subba Retty , Byrd L.
Published: February 2008

The problem of mixed convection from horizontal surfaces in a porous medium saturated with a power-law-type non-Newtonian fluid is investigated. The transformed conservation laws are solved numerically for the case of variable wall heat flux conditions. Results for the details of the velocity and temperature fields as well as the Nusselt number have been presented. The viscosity index ranged from 0.5–1.5.
A New Mechanism for FBC Agglomeration and Fouling in 100 Percent Firing of Petroleum Coke
Authors: Anthony E. J. , Iribarne A. P. , Iribarne J. V.
Published: February 2008

In an effort to clarify the causes of agglomeration and fouling in fluidized bed combustion of petroleum coke, a detailed study was made of samples taken from different locations of an industrial-sized CFBC boiler, including deposits formed after 7 and 96 days of operation. It was found that vanadium, the suspected cause of the agglomeration, does not accumulate in fouled regions and that no low melting oxides were present. Neither could any low melting eutectics be expected from the vanadium compounds identified. Therefore, the high concentrations of vanadium in the petroleum coke fuel cannot explain the formation of agglomerates. Fouling is attributed to molecular cramming effect caused by the nearly quantitative conversion of the CaO to CaSO4 and the absence of fuel-derived ash providing inert material, which could contribute discontinuities between the sintered anhydrite grains and prevent massive consolidation of deposits.