scope:

Preface

Friction, wear, and erosion are terms that most people use in their daily lives. Most people accept the cost of sport shoes wearing out after 4 months of use; people accept wear of roadways and flooring; people accept 30,000 miles as the limiting use of an automobile before fan belts, brakes, and other components start to wear out.

On a larger scale, most industrialized countries accept about 7% of their gross domestic product as their annual cost of wear, erosion, and unwanted friction. As one example of this annual cost: 450 million auto tires were manufactured in 2006 [1]. Probably 100 million of these tires were required for new vehicles. The remaining 350 million were most likely used to replace worn tires. Assuming that one tire cost $100, this amounts to a cost of wear of 35 billion dollars. This is just one commodity. Another staggering cost is the energy (gasoline) consumed in overcoming friction losses in an automobile. Some estimates for these losses are that as much as 30% of a vehicle's engine horsepower is used in overcoming friction in the sliding components between the gasoline explosion in the cylinders and the traction force transmitted to the roadway.

The point is that friction, wear, and erosion (tribology) concerns cost each and every person, as well as the environment, dearly. However, the world does not have to regard these costs and environmental consequences as inevitable costs of technology. They can be addressed and almost always reduced by appropriate engineering action. People older than 50 years of age will probably remember when the average life of an automobile tire was only about 15,000 miles. Today tire life is typically about 40,000 miles. What happened?

Engineers and scientists worked on this tribology problem. Tires were redesigned to be stiffer, which reduced roadway slip and thus wear. Tire materials were also improved. Undoubtedly, many of these tire improvements came to happen through screening tests conducted in laboratories, bench tests, as they are called. Tire engineers certainly could never make full size tires and run them to death to assess every change that may work. Concepts were screened by bench tests and that is what this guide is about.

This guide reviews current friction, wear, erosion, and lubrication fundamentals and describes the bench tests that are most often used to study and solve tribology problems. Tests are compared and critiqued. Information is presented to help the reader select a test that he or she might use to address a tribology concern that they are responsible for solving. The overall objective of the guide is to lower the annual cost of wear, erosion, and unwanted friction through appropriate tribotesting.

The scope includes tests that are used to study engineering materials (metals, plastics, ceramics, composites, lubricants, coatings, treatments), tests used to solve tribology problems and limited product tribotesting (abrasivity of magnetic media, printer ribbons, web friction etc.). Tire tests are not included-sorry! The tests described in this guide are predominately standard tests developed by consensus through ASTM International. Many countries have standard tests in these same areas, but the tests described in this guide are probably included in country-specific test standards. For example, every country that has tribotesting standards probably has a standard on a pin-on-disk test, a reciprocating pin-on-flat test, a sled friction test, etc. These are the same tests described in this guide. This guide is applicable worldwide.

The intended readership of this guide comprises mostly people who do not normally work in the field: students, designers, maintenance personnel, researchers, and academicians. It will help these people research a particular form of wear or friction, what tests are available, the cautions with each test, and information on how the different tests compare in severity. Also, it discusses how well they simulate real life applications. Veteran tribologists will find this guide a useful reference for ASTM test numbers and test details.

In summary, this guide is about tests (mostly standards) available to address friction, wear, erosion, and lubrication problems. It will serve as a mentor for newcomers to tribology and a useful reference for practicing tribologists. There are 13 chapters. The first presents needed terms and definitions. It is followed by a chapter on the alternates to bench testing: expert systems, modeling, and simulations; then follows a chapter on testing methodology. There are several chapters on specific forms of wear: abrasion testing, adhesive wear testing, plastic/elastomer testing, lubricated wear testing, fretting testing, rolling wear testing, and erosion testing. The guide ends with chapters on friction testing; micro-, nano-, and biotribotests; and correlation of these tests with service.

This book is essentially a project of the ASTM Committee G02 on Wear and Erosion. They are acknowledged for their sponsorship and participation in the review process. This guide is the product of more than 40 years of tribotesting in industry on the part of the author and probably another hundred years of experience in government, industry and academia on the part of the six tribology professionals who reviewed this guide for correctness and completeness. I sincerely thank them for their contributions.

K. G. Budinski