bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of Two Finite-Element Schemes for Feedback Control of a Timoshenko Beam
Authors: Tadi M. 
Published: March 2022

Abstract
This note is concerned with the application of two finite element schemes for use in designing feedback control laws for a Timoshenko slewing beam. The equations are presented in an abstract first order form. Feedback laws are obtained in the context of LQR theory. The effectiveness of two different finite element schemes in obtaining convergent functional gains are compared.
Robust Performance Analysis of Vibration Isolation Tables Using Tree-Structured Transfer Functions
Authors: Wilson Bruce H. , Erin Cem 
Published: March 2022

Abstract
The coefficients of physically-based models are often only known within certain bounds. Such parameter uncertainty complicates the control design problem. As eliminating all uncertainty is not a realistic option, formulating the model so that its behavior over the entire uncertainty space is easily determined can facilitate design and analysis. The model form suggested in this paper is a tree-structured transfer function. Bond graph theory provides the means to synthesize a transfer function with this structure. Both tree-structured and conventional transfer functions of a vibration isolation table, with five uncertain parameters, have been synthesized, and the former simplified the robust analysis problem more than the latter. The tree-structured transfer functions allowed the response envelope to be easily determined over key frequency ranges. The advantages of tree-structured over conventional transfer functions demonstrated in this paper suggest that this alternate form may be better suited for both nominal and robust analysis.
Performance Maximization of Internal Combustion Engine Idle Speed Control via Actuator Saturation
Authors: Herman Paul , Franchek Matthew A. 
Published: March 2022

Abstract
Presented in this paper is the design and implementation of a saturating idle speed controller for a Ford V-8 fuel injected engine subjected to a torque load disturbance. The performance specification for the controller design is |Δrpm| ≤ 140 rpm where the controlled input is the by-pass air valve (BPAV). The controller design is realized using a frequency domain approach developed in Herman and Franchek (1997). An experimental verification of the controller is presented. The performance objective is satisfied using saturation control during the engine speed transients.
Lateral Control of Vehicles Using Non-Linear Sliding Surfaces
Authors: Saraf Sujit , Tomizuka Masayoshi 
Published: March 2022

Abstract
Lateral controllers for vehicles on automated highways are required to ensure small tracking errors even while providing a comfortable ride. In addition, they must be robust to changes in operating conditions and road-vehicle parameters. Sliding mode control has been successfully used to provide robust lateral control. However, such control usually has a high gain nature, often resulting in poor ride quality. The problems of tire and actuator saturation are also not addressed explicitly. This paper proposes the use of non-linear sliding surfaces for lateral control of road vehicles, to take advantage of the robustness of sliding mode control while avoiding the possible problems of ride discomfort and tire or actuator saturation. Simulation results are presented.
A Complete Fault Diagnostic System for Longitudinal Control of Automated Vehicles
Authors: Rajamani Rajesh , Hedrick J. Karl , Howell Adam 
Published: March 2022

Abstract
A complete system for fault diagnostics of the longitudinal controllers in a platoon of automated vehicles is developed. The diagnostic system is designed to provide automated monitoring and fault identification of all the sensors and actuators used in the longitudinal control system, including radar sensors and inter-vehicle communication. The system uses several reduced-order nonlinear observers constructed from a longitudinal dynamic model of the vehicle. Multiple estimates of signals are obtained by designing each observer to utilize a different sensor measurement. Different combinations of all the available sensor signals and the observer estimates are then processed to construct a bank of 10 different residues. We show analytically that a fault in any of the sensors or actuators creates a unique subset of these residues to grow so as to enable exact identification of the faulty component.
Simulation results are presented to demonstrate the working of the fault diagnostic system in the presence of various faults.
On the Development of Boundary Layers in Non-Newtonian Fluids
Authors: Rajagopal K. R. 
Published: March 2022

Abstract
Boundary layers, regions of concentration of vorticity, appear adjacent to boundaries in the flow of a linearly viscous fluid at high Reynolds numbers. When the equations governing the flow of the linearly viscous fluid are appropriately non-dimensionalized, we find that the inertial term is multiplied by the Reynolds number, and this term while it is the only non-linear term in the equation is of lower order than the highest order term in the equation usually leading to a singular perturbation problem at high Reynolds numbers. The study of boundary layers in such fluids has led to significant developments in singular perturbation theory.
Viscoelastic Free Surface Jets and Filaments
Authors: Bechtel S. E. , Cao J. G. , Forest M. G. 
Published: March 2022

Abstract
In this paper we examine the necessary versus self-consistent consequences of a slender aspect ratio on viscoelastic free surface jet flows. As in Schultz & Davis (1982), the equations of the 3-D free surface jet problem are nondimensionalized with presumed disparate length scales in the transverse and axial directions, and a perturbation theory for the slender jet is obtained by positing an expansion in the slenderness parameter (i.e. the ratio ε of these scales). A different perturbation problem ensues for each regime of free jet behavior. We exhibit three regimes, one in which the slenderness scaling of the 3-D free surface jet problem forces a separation-of-variables (s-o-v) structure of the solution (that is, the radial coordinate explicitly factors out at each order in ε), another in which the s-o-v structure is not forced but is a solution, and a third in which the s-o-v structure is not a solution. These three regimes are prototypes for general filament behavior: of the many possible regimes, many are of the first type (the separation of variables structure is unique), many more are of the second type (the separation of variables solution exists but cannot be shown to be unique), and the rest are of the third type (if a slender solution exists it does not have a s-o-v structure).
A Heuristic Approach to Model Viscosity in the Momentum Equations
Authors: Gingold Harry , Gera Dinesh 
Published: March 2022

Abstract
A new approach to model viscosity in the conservation of momentum equations is presented and discussed. Coefficient of viscosity is modeled in such a way that it reaches asymptotically to infinity at the solid boundary but still yields a finite value for the shear stress at the solid wall. Basic objective of this research is to show that certain combinations of higher order normal velocity gradients become zero at the solid boundary. Modified solutions for the couette flow and poiseuille flow between parallel plates are obtained by modeling the coefficient of viscosity in a novel way. Also, viscous drag computed by our model is expected to yield higher values than the values predicted by the existing models, which matches closely to the experimental data.
Pulsatile Blood Flow in a Stenosed Artery
Authors: Pontrelli Giuseppe , Pedrizzetti Gianni 
Published: March 2022

Abstract
Unsteady axisymmetric flow in a constricted tube is studied. A shear-thinning model for viscosity of the blood is proposed. The motion equation is written in vorticity-streamfunction formulation and is integrated numerically by a finite difference scheme. The dependence of the flow on the dimensionless parameters has been investigated and differences with the newtonian case are discussed.
Flow of Yield-Stress Fluids in Complex Geometries
Authors: Vradis George C. 
Published: March 2022

Abstract
Experimental and computational results related to the flow of purely viscous non-Newtonian fluids exhibiting a yield stress are presented and discussed. A number of geometries and flow conditions have been analyzed representing both attached and separated flows of Bingham and Herschel-Bulkley fluids. The presence of a yield-stress is shown to significantly impact the flow characteristics, as compared to those in the case of a Newtonian fluid, in particular in the cases where separation of the flow would be expected.
Pulsating Viscoelastic Flow in Tubes of Arbitrary Cross-Section Shapes
Authors: Letelier Mario F. , Siginer Dennis A. 
Published: March 2022

Abstract
The axial velocity field in a tube of arbitrary cross-section geometry is determined for the case in which a viscoelastic fluid obeys a constitutive law of the multiple-integral type.
The flow is linearized by means of a perturbation scheme for small amplirud oscillations of the pressure gradient. At the first order for the velocity, a solution is found for cross-section contours of a wide variaty of shapes. In this method the no-slip boundary condition is imposed in contours whose shape depends on an infinite set of arbitrary functions that can be selected according to some guiding rules. In this manner, the resulting cross-sections approach ellipses, triangles, squares and many other regular and non-regular shapes. The analysis shows that very complex flow patterns, as depicted by isovel curves, develop according to the values of the fluid parameters and the solid boundary shapes. These results are necessary for further developments leading to the study of secondary flows.
The paper presents the analytical formulations and the flow fields associated to several tube geometries and different values of the fluid parameters.
A New Approach for Thermal Fatigue Testing of the Underfill/Passivation Interface
Authors: Gurumurthy Charan K. , Jiao Jinbao , Norris Larry G. , Hui Chung-Yuen , Kramer Edward J. 
Published: March 2022

Abstract
Delamination of the underfill/passivation interface due to thermal fatigue is a major cause for failure of DCA assemblies. Hence, we have developed a new technique based on a non-contact fiber optic displacement sensor to investigate the crack growth rate per cycle da/dN of an interfacial crack under thermal fatigue conditions. The sample is prepared as a multilayered cantilever beam by capillary flow of the underfill over a polyimide coated metallic beam. During thermal cycling the crack growth along the interface from the free end changes the displacement of this end of the beam and we measure this displacement at the lowest temperature in each thermal cycle. The change in beam displacement is converted into crack growth knowing the geometry of the specimen. The crack growth rate depends on the maximum difference in the strain energy release rate of the crack in each cycle. This paper outlines the theoretical basis of the technique and provides initial results obtained for a commercial underfill dispensed over a commercial (PMDA/ODA) polyimide. The technique was validated by comparing the crack growth measured by displacement changes with direct optical microscopy measurements of the crack length.
Potential Failure Sites in a Flip-Chip Package With and Without Underfill
Authors: Madenci E. , Shkarayev S. , Mahajan R. 
Published: March 2022

Abstract
The thermal integrity of an electronic package depends on the strength of the interface between dissimilar materials. Due to high thermo-mechanical stress concentrations arising from large temperature excursions, electronic packages become prone to cracking at regions with geometric and/or material discontinuities. Thus, the accurate calculation of the thermo-mechanical stresses in regions of high stress concentrations is critical to achieving a reliable design. These high-stress-concentration regions pose a major concern, especially in the design of flip-chip packages. Understanding the mechanisms for relaxing the high stress concentrations through the use of appropriate material properties, bump and adhesive joint geometry, and filler size in a flip-chip package will aid in design improvements for ensuring the thermo-mechanical reliability of electronic packages.
In this study, the effect of underfill on the level of stress concentrations is investigated and possible failure sites are identified by using a global/local finite element approach. The global elements capture the exact singular behavior of the stresses near the geometric and material discontinuities. Potential failure sites are established by applying concepts from fracture mechanics.
A New Approach to Calculate Atomic Flux Divergence by Electromigration
Authors: Sasagawa Kazuhiko , Nakamura Naoaki , Saka Masumi , Abé Hiroyuki 
Published: March 2022

Abstract
The atomic flux divergence obtained from current density and temperature in metal lines undamaged by electromigration is useful to predict the formation of initial void. In this study, a new method to calculate the atomic flux divergence used for predicting the formation of initial void is proposed considering two-dimensional distributions of current density and temperature and also simply considering the line structure not only of polycrystalline line but also of bamboo line. The flux divergence is formulated based on the Huntington-Grone’s equation and modeling of line structure. For the verification, electromigration phenomenon near the corner of an angled polycrystalline line, which results in two-dimensional distributions of current density and temperature, is treated as an example. The usefulness of the proposed method is discussed by comparison of the prediction of void formation near the corner with the experimental result.
Toughening of High Performance Epoxy Adhesives Using Core-Shell Particles
Authors: Sue Hung-Jue , Puckett P. Mac , Wang Yee Y. 
Published: March 2022

Abstract
Epoxy adhesives are commonly toughened by carboxylic terminated butadiene nitrile (CTBN) rubber to improve the T-peel and Lap-shear strength of adhesives. Unfortunately, many key material properties, such as glass-transition temperature (Tg), Young’s modulus, thermal expansion coefficient, and processability, will be compromised if CTBN rubber is utilized for toughening. Furthermore, CTBN rubber has been shown to be ineffective in toughening high performance, highly crosslinked thermosets. Novel rubber toughening approaches have to be sought to overcome the above-mentioned problems.
The present work focuses on the use of a core-shell particle (CSP) technology, which is comprised of either a rubber core or a rigid plastic core and a shell that stabilizes the dispersion of particles in thermosets. The results indicate that the toughness can be greatly improved by introducing the CSP for toughening. No reduction in Tg is observed. The modulus of elasticity of the CSP-toughened epoxy systems can be maintained if the core of CSP being utilized is rigid. Furthermore, since the viscosity of the toughened epoxy only increases slightly, no compromise in processability is made. These CSP may be suitable for toughening highly filled thermosets for electronic applications.
Opportunities and Needs for Interfacial Fracture Mechanics in Microelectronic Packaging Industry
Authors: Chen William T. , Questad David , Read David , Sammakia Bahgat 
Published: March 2022

Abstract
This paper will review the trends for semiconductors, the impact on electronic products, and the requirements on electronic packaging materials, design, reliability and manufacturing. There is an increasing realization that materials and mechanics principles can be utilized to great advantage in electronic packaging industry. New electronic packages such as ball grid array modules (BGA), chip scale packages (CSP), MicroVia substrates, and low temperature solder bump assemblies, present interesting opportunities for the utilization of fracture mechanics principles in the analysis and modeling of those packages. This paper will present, from a packaging engineer’s perspective, the utilization of interfaial fracture mechanics in the packaging community. Particular emphasis will be on fracture mechanics applied to interfaces in an assembled packaging structure.
An Experimental and Numerical Analysis of Near Tip Behavior in a Multi-Phase Material
Authors: Liu C. T. , Ravichandran G. 
Published: March 2022

Abstract
In this paper, the local strain fields near the crack tip in a multi-phase material subjected to two different strain rates (0.05 min−1 and 0.25 min−1) at room temperature were analyzed, experiment-ally and numerically. Precracked specimens made from polybutadiene rubber embedded with hard particles were used in the crack propaga-tion tests. A grid method was used to obtain the strain fields near the crack tip and a nonlinear finite element computer code was used to determine the near tip strain fields. The results of analyses show that a good correlation exists between the experimental and the numerical results.
The Mechanics of Hydride Formation and Embrittlement
Authors: Lufrano J. , Sofronis P. , Birnbaum H. K. 
Published: March 2022

Abstract
Transient hydrogen diffusion and hydride formation coupled with material deformation are studied in a hydride forming system. The concept of terminal solid solubility of hydrogen as affected by stress is described and the mode of hydrogen diffusion through the two-phase material (matrix+hydride) is discussed. Probabilistic precipitation of hydride is modeled in the neighborhood of a crack tip under mode I plane strain loading and a uniform initial hydrogen concentration below the stress free terminal solid solubility. A full transient finite element analysis allows for numerical monitoring of the development and expansion of the hydride zone. Information about the shape, size, and density of the hydride in the hydride zone is obtained. The mechanistic effects of the solute hydrogen and hydride formation on the stresses at the crack tip are analyzed and their consequence on the fracture toughness resistance of the material is calculated.
Yield Strength of Nitrogen Alloyed Duplex Steels: Hall-Petch Analysis and Micromechanical Predictions
Authors: Werner E. A. , Horvath W. , Prantl W. 
Published: March 2022

Abstract
For the prediction of the yield strength of nitrogen alloyed ferritic-austenitic duplex steels, accurate knowledge on the single phases’ yield strength and their geometrical arrangement within the duplex microstructure is required. Since the matrix-inclusion character of the phases markedly influences the yield strength σyd of duplex steels, linear models for σyd (Voigt-model) cannot serve for an accurate prediction of σyd. A non-linear rule of mixture, however, is a more sophisticated approach to calculate σyd. Micromechanical models combined with finite element computations are efficient tools to accurately predict the influence of the topology of the microstructure on σyd only if the yield strengths of the single phases are distinctly different, i.e. the yield strength ratio of ferrite to austenite ψ is larger than 2. Experiments on duplex steels show, however, a marked influence of the phase arrangement on σyd even for ψ ∼ 1. To explain this behavior a modified non-linear rule of mixture is proposed, which incorporates the in-situ yield strengths of the phases as upper and lower bounds for σyd. The discrepancy between the experiments (and their analysis) and the predictions from the micromechanical approach convincingly demonstrates the necessity to include crystallographic details such as dislocation-interface boundary interactions and misorientation and crystal structures of adjacent grains in improved micromechanical models for the yield strength of duplex steel microstructures.
Measurement and Quantification of Surface Roughness
Authors: Dewhurst Timothy B. , Mason Scott D. 
Published: March 2022

Abstract
The development of surface roughness during underlying bulk deformation is of critical importance to some metalforming industries such as beverage can and automobile manufacturers. This work is investigating the correlation between surface roughness and texture evolution within the material. The first phase of this work has concentrated on the measurement of surface roughness in compression specimens; various approaches to identifying meaningful metrics to quantify this roughness; and the documentation of the deformation path and texture evolution during the process. In identifying an appropriate metric for surface roughness, the work has focused on the use of fractals, standard statistical measures, and power spectrums. Each of these is evaluated for use in this type of study as it will be necessary in the near future to have a reliable method of comparing the experimental results to computer modeling for surface roughness. In the second phase of this work, polycrystal plasticity models will be used to track both texture evolution and the development of surface roughness during the deformation process. The computational results will be closely compared to the experimental results presented here.
Sustained-Load Cracking in Mill Annealed Ti-6Al-4V at Room Temperature
Authors: Lenets Youri , Thomas James P. , Nicholas Theodore 
Published: March 2022

Abstract
Sustained-load crack growth in the near threshold regime was studied at room temperature in a mill-annealed Ti-6Al-4V titanium alloy forging using mini-C(T) specimens in the C-L orientation. The observed sustained-load cracking behavior exhibited an apparent crack length dependence beyond that accounted for by the fracture mechanics parameter K. In addition, the initial value of K, applied after crack extension by fatigue, influenced the subsequent crack growth rates. The influence of the far-field specimen stresses on the hydrogen diffusion process at the crack tip and transient crack growth rate effects appear to be responsible for the observed behavior.
Predicting the Precipitation Hardening Response of Particle Strengthened Alloys Hardened by Ordered Precipitates
Authors: Fragomeni James M. , Hillberry Ben M. 
Published: March 2022

Abstract
A model/method was developed for predicting the precipitation hardening response of particle strengthened alloys hardened by ordered precipitates based on the microstructure, composition, and heat treatment, and utilizing a minimum number of experimental tests. The overall approach was based on the dislocation particle interaction mechanics, particle growth and coarsening, thermodynamics, and particle strengthening mechanisms applicable to precipitation hardened alloys. The model/method evaluates, from a minimum number of experimental tensile tests, several of the microstructural constants necessary in determining the precipitation strengthening response of a particle strengthened alloy. The materials that were used as vehicles to demonstrate the model were precipitation hardenable aluminum-lithium-zirconium and nickel-aluminum alloys. Utilizing these demonstration alloys, the method used a minimum number of four tensile tests to predict the variation in strength with aging time, aging temperature, and composition, for the underaged, the peak-aged, and the overaged conditions. Predictions of the precipitation strengthening response were made using the Wagner particle distribution model and the predicted results using this distribution model compared well with the experimental yield strength results.