Fundamentals of Friction

Extract

By most recent estimates, improved attention to friction and wear would save developed countries up to 1.6% of their gross national product—over $100 billion annually in the United States alone. It is thus not surprising that tribomaterials, materials designed for use in moving contact (sliding, rolling, abrasive, etc.) have for decades attracted the interests of materials scientists and mechanical and chemical engineers. However the field of tribology is hardly a recent one. Such tribological advances as Leonardo da Vinci's design of intricate gears and bearings (some of which were not built until the Industrial Revolution provided sufficiently strong materials) and the landmark 18th century development of a timepiece allowing accurate longitudinal positioning of ships at sea (accomplished via a self-lubricating wooden gear) could easily be termed “modern,” given the overall longevity of the field.

As important as tribomaterials are to technology, their discovery has usually been serendipitous. Materials scientists have frequently been able to provide explanations for why tribomaterials perform as well as they do. They have also been able to substantially improve the performance of tribomaterials through the development of new alloys, composites, and/or improved surface-engineering methods. They have however been far less successful at a priori design of tribomaterials with improved performance, largely because friction and wear processes have not been understood at the fundamental level.

The late 1980s marked the advent of renewed interest in fundamental areas of tribology, sparked by a number of new experimental and theoretical techniques that made it possible to study the force of friction in geometries that are well-defined at the nanometer scale.