The variations of residual stress distributions on solder balls under the cyclic thermal load and aging processes are investigated in this thesis. The solidification phenomena for different shapes and materials of the solder balls during the reflow process are predicted by using the Surface Evolver program. The distribution of residual stress in the solder ball is calculated by employing the MARC finite element package. The temperature dependent material properties of the solders, i.e. 63Sn/37Pb and 96.5Sn/3.5Ag, are used in the residual stresses calculations. The variation of the residual stresses distributions of different solder balls under the temperature cycling test ( between ¡V40¢J and 85¢J ) and the aging test ( at 85¢J ) are simulated and studied. The effects of the solder parameters, i.e. the solder height and the pad geometry shapes on the residual stresses distribution are also studied. Besides, the same simulation and analysis has also applied on the solder ball with an unleaded solder 96.5Sn/3.5Ag. A better understanding about the variation of the residual stress in a solder ball is expected from this analysis.

Developments in micro and nano technology have great potential in many applications. Two applications that will be addressed in this work are self assembly of microdevices and Electrowetting in microfluidics. Capillary forces are the most critical factor in both of these techniques and need proper characterization. This thesis describes a detailed study of these forces and explains how they were utilized as an effective source of drive in high end applications. Self assembly is a promising alternative to conventional pick and place robotic assembly of micro components. Its benefits include parallel integration of parts with low equipment costs. Various approaches to self assembly have been demonstrated, yet demanding applications like assembly of micro-optical devices require increased positioning accuracy. This thesis proposes a new method for design of self assembly bonds that addresses this need. Current methods have zero force at the desired assembly position and low stiffness. The proposed method uses a substrate assembly feature to provide a high accuracy alignment guide to the part. The capillary bond region of the part and substrate are then modified to create a non-zero positioning force to maintain the part in the desired assembly position. Capillary force models show that this force aligns the part to the substrate assembly feature and reduces the sensitivity of part position to process variation. Thus, the new configuration analyzed proves substantial improvement in positioning accuracy of capillary self assembly. Guidelines are proposed for the design of an effective assembly bond using this new approach. Electrowetting is another application that has been successfully demonstrated as a means of drop manipulations in digital micro-fluidic devices. These demonstrations show that electrowetting actuation holds great promise, but there are also reports of erratic behavior and system degradation. While a method for electrowetting force measurement to track the degradation of the electrowetting response was demonstrated, this thesis analyzes some adverse effects in the electrowetting response due to variations during measurement of electrowetting forces, specially the variation of volume, the tilt in the part considered for measurements, and defective layer response.

Two topics relating to low gravity fluid behavior in satellite propellant tanks are considered. In the first, static case, the problem of liquid trapping is examined. Satellite propellant tank end caps optimized for weight are generally shallower and more oblate than hemispherical end caps of the same radius. However, these shallower end caps pose an interesting challenge for propellant management. In the absence of vanes, it is possible for liquid propellant to be trapped in the tank and become unusable. Understanding of how propellant tends to distribute itself in the bare, vaneless tank can be used to drive vane design to counteract these tendencies and ensure propellant remains where desired. The first section of this thesis aims to demonstrate methods that can be used to identify when, how, and why liquid trapping occurs in a given tank geometry. A fluid statics code called Surface Evolver is used to calculate possible fluid configurations for different propellant volumes, contact angles, and end cap designs. The specific case of a cylindrical tank with 2:1 ellipsoidal end caps is studied extensively for ranges of fill fractions and contact angles to illustrate the methods used. Results are computed for each possible propellant configuration: a spherical liquid-gas interface, an asymmetric liquid-gas interface, and a liquid ring. Analytical solutions are found and compared against Surface Evolver results for the spherical liquid-gas interface and liquid ring, showing excellent agreement. Results are also found for other aspect ratio ellipsoidal end caps, superellipsoidal end caps, and torispherical end caps. Each non-hemispherical dome design is found to be able to trap liquid away from the axis of the tank regardless of contact angle. The second part of this thesis, focusing on the dynamic case, details the development of an experimental payload designed to fly on Virgin Galactic’s SpaceShipTwo. This experiment is designed to obtain data on sloshing behavior of liquids in microgravity in response to rotation. The payload contains eight scaled down propellant tanks that are rotated while in microgravity, and the resulting slosh is recorded by video cameras inside the payload. The video will be analyzed after the experiment to extract data on damping rates and potentially positional data of the liquid-gas interface. The impact of constraints on the design of the overall experiment are discussed. The purpose of each component in the experiment is explained and justified relative to the design constraints. The remaining work that must be completed before flight on SpaceShipTwo is reviewed, highlighting the most significant unknowns.<br>

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Cette thèse a pour objet d'étudier la rhéologie des mousses 2D. Des mousses monodisperses sont soumises à une déformation cyclique localisée en régime quasistatique. Un dispositif expérimental sollicite la mousse par gonflage et dégonflage d'une bulle centrale (BC) et suit l'évolution de la pression de la BC au cours du temps. Au gonflage, les expériences ont montré que BC choisit une direction d'ouverture privilégiée. L'analyse de sa forme montre un régime isotrope où la bulle est ronde puis un régime anisotrope où la bulle est de forme pointue de direction aléatoire. Les expériences ont montré que, durant les deux premiers cycles, des changements topologiques (T1) se produisent partout dans la mousse. Après ce régime transitoire, les T1 se produisent uniquement à proximité de la BC de façon ordonnée et réversible. Dans ce régime, après chaque cycle, l'énergie de la mousse est identique. Donc toute l'énergie injectée est dissipée par les T1. Le calcul de l'énergie injectée a permis d'en déduire l'énergie moyenne dissipée par un T1. Enfin, une analyse plus fine montre que le T1 a un effet sur les autres bulles de la mousse. Pour cela nous avons calculé, lors d'un T1, les fluctuations de pression des bulles par le logiciel Surface Evolver ainsi que leurs déplacements. L'analyse montre une réponse quadripolaire de la mousse au T1. L'influence de la distance au T1 a montré une atténuation des sauts de pression. Cette atténuation se rapproche à la fois d'une loi de puissance ou d'une exponentielle, sans que l'on ait pu discriminer les deux comportements. Le meilleur ajustement exponentiel donne une longueur d'écrantage de 2 diamètres de bulles quelle que soit la taille de la mousse.

The inhibiting effect of a sharp edge on liquid spreading is well observed during drop interaction with textured surfaces. On groove-textured solid surfaces comprising unidirectional parallel grooves, the edge effect of posts results in the squeezing of drop liquid in the direction perpendicular to the grooves and the stretching of drop liquid along the grooves leading to anisotropy in drop flow, popularly known as wetting anisotropy which has been employed in several engineering applications. A recent study observed that the energy loss incurring at the edges of posts via contact angle hysteresis is primarily responsible for the anisotropic spreading of impacting drops on groove-textured surfaces. The present study aims to elucidate the role of edges on the spreading and receding dynamics of water drops. The experiments of drop impact are carried out on semi-infinite rectangular post comprising a pair of parallel 90-deg edges separated by a distance (post width) comparable to the diameter of impacting drop. The equilibrium shape of drops on the semi-infinite rectangular post is analyzed using open source computational tool Surface Evolver to optimize the ratio of initial droplet diameter to post width. Quantitative measurements of drop impact dynamics on semi-infinite rectangular posts are deduced by analysing high speed videos of impact process captured under three different camera views during experiments. Based on the role of post edges on impacting drops, different regimes of the impacting drops are characterized in terms of drop Weber number and the ratio of diameter of impacting drop to post width. Characteristic features of impact dynamics in each of the regimes are identified and discussed. It is seen that edges play a pivotal role on all stages of impact dynamics regardless of Weber number. Impacts in the regime of completely pinned drops on narrow posts are further analyzed to reveal characteristics of post-spreading oscillations.