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In the last decade, reliability problems have become a critical subject in power modules. Understanding design weakness and failure mechanisms of thick wire bond are two critical steps in managing the risk of wire bond heel crack which is the topic of this thesis. Although this thesis does not target a specific type of power modules, we note that thick wire bond heel crack failures occur in Insulated Gate Bipolar Transistors (IGBTs). In fact, our aim is to understand failure mechanism in 300μm thick wire bonds with different geometries and materials. Since these wires experience harsh environmental conditions and high load transients, the wires undergo repetitive flexural movement which causes heel crack due to fatigue. For the purpose of understanding this failure mechanism, two experimental setups are built and utilized. The first experimental setup loads the wires using constant currents and observes the response using a scanning laser vibrometer to measure the displacement. The second experimental setup applies repetitive prescribed displacement to the first foot of the wire and detects fatigue failure using a Wheatstone bridge. It is realized that wires have different displacement property depending on their geometry and material. Maximum displacements are observed for Al-H11 instead of CuCorAl and PowerCu.

The objective of this thesis was to identify differences in torque expression between three brands of metallic self-ligating brackets with stainless steel, TMA® and CuNiTi® wire and to compare active and passive designs. 150 of each Damon-3MX (Ormco Inc, Orange, CA, USA), SPEED (Strite Industries, Cambridge, Ontario, Canada) and In-Ovation-R (GAC, Bohemia, NY, USA) brackets were measured for torque expression (Nmm) in an Air-shields Isolette® infant incubator. Torque expression in SPEED and In-Ovation-R brackets began at approximately 7.5° vs. 12° with Damon-3MX. Clinically applicable torque expression (5-20Nmm) was observed from approximately 15-30° in SPEED & In-Ovation-R brackets with stainless steel wire. In Damon-3MX, comparable torsional moments were expressed from 18-30°. With TMA wire, SPEED exerted clinically applicable torsional moments from 18-39°, In-Ovation-R from 21-39° and Damon-3MX from 21-42°. For CuNiTi wire, SPEED expressed torsional moments of 5-20Nmm from 21-72°, In-Ovation-R from 24-63° and Damon-3MX from 27-78°. / Medical Science-Orthodontics

The fluid flow and heat transfer characteristics of the turbulent swirling flow of air through a heated annulus have been quantified. The motivation for this study was to improve the understanding of flow within a SIROSMELT top submerged industrial smelting lance. Within the lance, helical vane swirler flights are used to impart swirl to a coolant, so that heat transfer from the lance wall to the coolant is enhanced. A review of the literature revealed no information on the mean and turbulent flow structure for swirling flows in a heated annulus. (For complete abstract open document)

Techn. Universiẗat, Diss., 2005--Darmstadt.

Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 1998? / Title from screen page; viewed 7 Feb 2005. Includes bibliographical references. Also available in a print form.

Inaug.-Diss. (Ph. D.)--Friedrich-Wilhelms-Universität zu Berlin, 1894. / Includes bibliographical references.

Zugl.: Aachen, Techn. Hochsch., Diss., 2008

Inaug.-Diss. (Ph. D.)--Friedrich-Wilhelms-Universität zu Berlin, 1894. / Includes bibliographical references.