Matching Items (210)
Description
With the increasing focus on developing environmentally benign electronic packages, lead-free solder alloys have received a great deal of attention. Mishandling of packages, during manufacture, assembly, or by the user may cause failure of solder joint. A fundamental understanding of the behavior of lead-free solders under mechanical shock conditions is lacking. Reliable experimental and numerical analysis of lead-free solder joints in the intermediate strain rate regime need to be investigated. This dissertation mainly focuses on exploring the mechanical shock behavior of lead-free tin-rich solder alloys via multiscale modeling and numerical simulations. First, the macroscopic stress/strain behaviors of three bulk lead-free tin-rich solders were tested over a range of strain rates from 0.001/s to 30/s. Finite element analysis was conducted to determine appropriate specimen geometry that could reach a homogeneous stress/strain field and a relatively high strain rate. A novel self-consistent true stress correction method is developed to compensate the inaccuracy caused by the triaxial stress state at the post-necking stage. Then the material property of micron-scale intermetallic was examined by micro-compression test. The accuracy of this measure is systematically validated by finite element analysis, and empirical adjustments are provided. Moreover, the interfacial property of the solder/intermetallic interface is investigated, and a continuum traction-separation law of this interface is developed from an atomistic-based cohesive element method. The macroscopic stress/strain relation and microstructural properties are combined together to form a multiscale material behavior via a stochastic approach for both solder and intermetallic. As a result, solder is modeled by porous plasticity with random voids, and intermetallic is characterized as brittle material with random vulnerable region. Thereafter, the porous plasticity fracture of the solders and the brittle fracture of the intermetallics are coupled together in one finite element model. Finally, this study yields a multiscale model to understand and predict the mechanical shock behavior of lead-free tin-rich solder joints. Different fracture patterns are observed for various strain rates and/or intermetallic thicknesses. The predictions have a good agreement with the theory and experiments.
ContributorsFei, Huiyang (Author) / Jiang, Hanqing (Thesis advisor) / Chawla, Nikhilesh (Thesis advisor) / Tasooji, Amaneh (Committee member) / Mobasher, Barzin (Committee member) / Rajan, Subramaniam D. (Committee member) / Arizona State University (Publisher)
Created2011
Description
Laminated composites are increasingly being used in various industries including <br/>automotive and aerospace. Under a variety of extreme loading conditions such as low and <br/>high-velocity impacts and crash, laminated composites delaminate. To understand how and<br/>when delamination occurs, two types of laboratory tests are conducted - End-notched <br/>Flexure (ENF) test and Double Cantilever Beam (DCB) test. The ENF test is designed to <br/>find the mode II interlaminar fracture toughness, and the DCB test, the mode I interlaminar <br/>fracture toughness. In this thesis, thermopressed Honeywell Spectra Shield® 5231 <br/>composite specimens made of ultra-high molecular weight polyethylene (UHMWPE), <br/>manufactured under two different pressures (3000 psi and 6000 psi), are tested in the <br/>laboratory to find its delamination properties. The test specimen preparation, experimental <br/>procedures, and data reduction to determine the mode I and mode II interlaminar fracture <br/>properties are discussed. The ENF test results show a 15.8% increase in strain energy <br/>release rate for the 6000 psi specimens when compared to the 3000 psi specimens. <br/>Conducting the DCB tests proved to be challenging due to the low compressive strength <br/>of the material and hence required modifications to the test specimens. An estimate of the <br/>mode I interlaminar fracture toughness was found for only two of the 6000 psi specimens.
ContributorsRyder, Chandler (Author) / Rajan, Subramaniam (Thesis director) / Khaled, Bilal (Committee member) / Neithalath, Narayanan (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
Early-age cracks in fresh concrete occur mainly due to high rate of surface evaporation and restraint offered by the contracting solid phase. Available test methods that simulate severe drying conditions, however, were not originally designed to focus on evaporation and transport characteristics of the liquid-gas phases in a hydrating cementitious microstructure. Therefore, these tests lack accurate measurement of the drying rate and data interpretation based on the principles of transport properties is limited. A vacuum-based test method capable of simulating early-age cracks in 2-D cement paste is developed which continuously monitors the weight loss and changes to the surface characteristics. 2-D crack evolution is documented using time-lapse photography. Effects of sample size, w/c ratio, initial curing and fiber content are studied. In the subsequent analysis, the cement paste phase is considered as a porous medium and moisture transport is described based on surface mass transfer and internal moisture transport characteristics. Results indicate that drying occurs in two stages: constant drying rate period (stage I), followed by a falling drying rate period (stage II). Vapor diffusion in stage I and unsaturated flow within porous medium in stage II determine the overall rate of evaporation. The mass loss results are analyzed using diffusion-based models. Results show that moisture diffusivity in stage I is higher than its value in stage II by more than one order of magnitude. The drying model is used in conjunction with a shrinkage model to predict the development of capillary pressures. Similar approach is implemented in drying restrained ring specimens to predict 1-D crack width development. An analytical approach relates diffusion, shrinkage, creep, tensile and fracture properties to interpret the experimental data. Evaporation potential is introduced based on the boundary layer concept, mass transfer, and a driving force consisting of the concentration gradient. Effect of wind velocity is reflected on Reynolds number which affects the boundary layer on sample surface. This parameter along with Schmidt and Sherwood numbers are used for prediction of mass transfer coefficient. Concentration gradient is shown to be a strong function of temperature and relative humidity and used to predict the evaporation potential. Results of modeling efforts are compared with a variety of test results reported in the literature. Diffusivity data and results of 1-D and 2-D image analyses indicate significant effects of fibers on controlling early-age cracks. Presented models are capable of predicting evaporation rates and moisture flow through hydrating cement-based materials during early-age drying and shrinkage conditions.
ContributorsBakhshi, Mehdi (Author) / Mobasher, Barzin (Thesis advisor) / Rajan, Subramaniam D. (Committee member) / Zapata, Claudia E. (Committee member) / Arizona State University (Publisher)
Created2011
ContributorsRyan, Russell (Performer) / Campbell, Andrew (Performer) / ASU Library. Music Library (Publisher)
Created2021-02-17
Description
Nuclear magnetic resonance (NMR) is an important phenomenon involving nuclear magnetic moments in magnetic field, which can provide much information about a wide range of materials, including their chemical composition, chemical environments and nuclear spin interactions. The NMR spectrometer has been extensively developed and used in many areas of research. In this thesis, studies in two different areas using NMR are presented. First, a new kind of nanoparticle, Gd(DTPA) intercalated layered double hydroxide (LDH), has been successfully synthesized in the laboratory of Prof. Dey in SEMTE at ASU. In Chapter II, the NMR relaxation studies of two types of LDH (Mg, Al-LDH and Zn, Al-LDH) are presented and the results show that when they are intercalated with Gd(DTPA) they have a higher relaxivity than current commercial magnetic resonance imaging (MRI) contrast agents, such as DTPA in water solution. So this material may be useful as an MRI contrast agent. Several conditions were examined, such as nanoparticle size, pH and intercalation percentage, to determine the optimal relaxivity of this nanoparticle. Further NMR studies and simulations were conducted to provide an explanation for the high relaxivity. Second, fly ash is a kind of cementitious material, which has been of great interest because, when activated by an alkaline solution, it exhibits the capability for replacing ordinary Portland cement as a concrete binder. However, the reaction of activated fly ash is not fully understood. In chapter III, pore structure and NMR studies of activated fly ash using different activators, including NaOH and KOH (4M and 8M) and Na/K silicate, are presented. The pore structure, degree of order and proportion of different components in the reaction product were obtained, which reveal much about the reaction and makeup of the final product.
ContributorsPeng, Zihui (Author) / Marzke, Robert F (Thesis advisor) / Dey, Sandwip Kumar (Committee member) / Neithalath, Narayanan (Committee member) / Chamberlin, Ralph Vary (Committee member) / Mccartney, Martha Rogers (Committee member) / Arizona State University (Publisher)
Created2013
Description
The Vocal Jazz ensemble, a uniquely American choral form, has grown and flourished in the past half century largely through the efforts of professionals and educators throughout the collegiate music community. This document provides historical data as presented through live and published interviews with key individuals involved in the early development of collegiate Vocal Jazz, as well as those who continue this effort currently. It also offers a study of the most influential creative forces that provided the spark for everyone else's fire. A frank discussion on the obstacles encountered and overcome is central to the overall theme of this research into a genre that has moved from a marginalized afterthought to a legitimate, more widely accepted art form. In addition to the perspective provided to future generations of educators in this field, this document also discusses the role of collegiate music academia in preserving and promoting the Vocal Jazz ensemble. The discussion relies on recent data showing the benefits of Vocal Jazz training and the need for authenticity towards its universal integration into college and university vocal performance and music education training.
ContributorsAmerind, Gregory (Author) / Kocour, Michael (Thesis advisor) / Carpenter, Ellon (Committee member) / Britton, David (Committee member) / Ryan, Russell (Committee member) / Arizona State University (Publisher)
Created2013
Description
This study focused on investigating the ability of a polymeric-enhanced high-tenacity fabric composite called CarbonFlex to mitigate damages from multi-natural hazards, which are earthquakes and tornadoes, in wood-framed structures. Typically, wood-framed shear wall is a seismic protection system used in low-rise wood structures. It is well-known that the main energy dissipation of the system is its fasteners (nails) which are not enough to dissipate energy leading to decreasing of structure's integrity. Moreover, wood shear walls could not sustain their stiffness after experiencing moderate wall drift which made them susceptible to strong aftershocks. Therefore, CarbonFlex shear wall system was proposed to be used in the wood-framed structures. Seven full-size CarbonFlex shear walls and a CarbonFlex wrapped structures were tested. The results were compared to those of conventional wood-framed shear walls and a wood structure. The comparisons indicated that CarbonFlex specimens could sustain their strength and fully recover their initial stiffness although they experienced four percent story drift while the stiffness of the conventional structure dramatically degraded. This indicated that CarbonFlex shear wall systems provided a better seismic protection to wood-framed structures. To evaluate capability of CarbonFlex to resist impact damages from wind-borne debris in tornadoes, several debris impact tests of CarbonFlex and a carbon fiber reinforced storm shelter's wall panels were conducted. The results showed that three CarbonFlex wall panels passed the test at the highest debris impact speed and the other two passed the test at the second highest speed while the carbon fiber panel failed both impact speeds.
ContributorsDhiradhamvit, Kittinan (Author) / Attard, Thomas L (Thesis advisor) / Fafitis, Apostolos (Thesis advisor) / Neithalath, Narayanan (Committee member) / Thomas, Benjamin (Committee member) / Arizona State University (Publisher)
Created2013
Description
The increased emphasis on the detrimental effects of the production of construction materials such as ordinary portland cement (OPC) have driven studies of the alkali activation of aluminosilicate materials as binder systems derived from industrial byproducts. They have been extensively studied due to the advantages they offer in terms of enhanced material properties, while increasing sustainability by the reuse of industrial waste and reducing the adverse impacts of OPC production. Ground granulated blast furnace slag is one of the commonly used materials for their content of calcium and silica species. Alkaline activators such as silicates, aluminates etc. are generally used. These materials undergo dissolution, polymerization with the alkali, condensation on particle surfaces and solidification under the influence of alkaline activators. Exhaustive studies exploring the effects of sodium silicate as an activator however there is a significant lack of work on exploring the effect of the cation and the effect of liquid and powder activators. The focus of this thesis is hence segmented into two topics: (i) influence of liquid Na and K silicate activators to explore the effect of silicate and hydroxide addition and (ii) influence of powder Na and K Silicate activators to explore the effect of cation, concentration and silicates. Isothermal calorimetric studies have been performed to evaluate the early hydration process, and to understand the reaction kinetics of the liquid and powder alkali activated systems. The reaction kinetics had an impact on the early age behavior of these binders which can be explained by the compressive strength results. It was noticed that the concentration and silica modulus of the activator had a greater influence than the cation over the compressive strength. Quantification of the hydration products resultant from these systems was performed via thermo gravimetric analysis (TGA). The difference in the reaction products formed with varying cation and silicate addition in these alkali activated systems is brought out. Fourier transform infrared (FTIR) spectroscopy was used to investigate the degree of polymerization achieved in these systems. This is indicative of silica and alumina bonds in the system. Differences in the behavior of the cation are attributable to size of the hydration sphere and polarizing effect of the cation which are summarized at the end of the study.
ContributorsDakhane, Akash (Author) / Neithalath, Narayanan (Thesis advisor) / Subramaniam, Dharmarajan (Committee member) / Mobashar, Barzin (Committee member) / Arizona State University (Publisher)
Created2013
Description
This document is intended to show the various kinds of stylistically appropriate melodic and rhythmic ornamentation that can be used in the improvisation of the Sarabandes by J.S. Bach. Traditional editions of Bach's and other Baroque-era keyboard works have reflected evolving historical trends. The historical performance movement and other attempts to "clean up" pre-1950s romanticized performances have greatly limited the freedom and experimentation that was the original intention of these dances. Prior to this study, few ornamented editions of these works have been published. Although traditional practices do not necessarily encourage classical improvisation in performance I argue that manipulation of the melodic and rhythmic layers over the established harmonic progressions will not only provide diversity within the individual dance movements, but also further engage the ears of the performer and listener which encourages further creative exploration. I will focus this study on the ornamentation of all six Sarabandes from J.S. Bach's French Suites and show how various types of melodic and rhythmic variation can provide aurally pleasing alternatives to the composed score without disrupting the harmonic fluency. The author intends this document to be used as a pedagogical tool and the fully ornamented Sarabandes from J.S. Bach's French Suites are included with this document.
ContributorsOakley, Ashley (Author) / Meir, Baruch (Thesis advisor) / Campbell, Andrew (Committee member) / Norton, Kay (Committee member) / Pagano, Caio (Committee member) / Ryan, Russell (Committee member) / Arizona State University (Publisher)
Created2013
Description
The purpose of the paper is to outline the process that was used to write a reduction for Henry Brant's Concerto for Alto Saxophone and Orchestra, to describe the improvements in saxophone playing since the premiere of the piece, and to demonstrate the necessity of having a reduction in the process of learning a concerto. The Concerto was inspired by internationally known saxophonist, Sigurd Rascher, who demonstrated for Brant the extent of his abilities on the saxophone. These abilities included use of four-octave range and two types of extended techniques: slap-tonguing and flutter-tonguing. Brant incorporated all three elements in his Concerto, and believed that only Rascher had the command over the saxophone needed to perform the piece. To prevent the possibility of an unsuccessful performance, Brant chose to make the piece unavailable to saxophonists by leaving the Concerto without a reduction. Subsequently, there were no performances of this piece between 1953 and 2001. In 2011, the two directors of Brant's Estate decided to allow for a reduction to be written for the piece so that it would become more widely available to saxophonists.
ContributorsAmes, Elizabeth (Pianist) (Author) / Ryan, Russell (Thesis advisor) / Levy, Benjamin (Committee member) / Hill, Gary (Committee member) / Campbell, Andrew (Committee member) / Arizona State University (Publisher)
Created2013