This book is about failure mechanisms in bearings and seals when high speeds or loads cause significant frictional heating. It is about how to predict and avoid these kinds of failures. The text is intended for the designer and mechanical engineer responsible for high-performance machinery. The subject matter is analytical and interdisciplinary. It incorporates transient heat flow, thermal deformation, and the fluid mechanics of thin films. A systematic effort has been made to define and condense these contributions into a set of tools that can solve practical problems. The primary goal of this book is to give modem engineers a set of guidelines and design criteria to help them avoid thermally coupled failures in machines. The most important features are (I) the systematic definition and treatment of specific phenomena, (2) the use of consistent nomenclature, and (3) the worked examples. Recent publications are incorporated, and completely new work is presented to fill in gaps in the existing literature. When thin viscous films are sheared at high rates, viscous heating can distort the solid boundary surfaces. The simplest configuration that shows this effect is the flow around a cylindrical journal that turns in a cylindrical bore. Thermal deformation can be the same magnitude as film thickness and can cause changes in the distribution of viscous heating. As a consequence, heating may be concentrated at small areas on the solid boundary surfaces and thus cause seizure when the critical temperature for a given material is reached.