Chapter 1-Identification of Different Types of Wear

DIAGNOSIS IS THE FIRST STEP IN SOLVING A medical problem, a car repair, or home repair problem-just about any problem. What is the nature of the problem? What does it look like? What is its severity? Some wear diagnoses are very fast and simple. For example, when the treads disappear on your automobile tires, you can be safe in assuming that abrasive wear from roadway contact removed enough material to warrant replacement. However, when an automobile engine starts to burn oil and have less power than normal, it may take some sleuthing to find out whether something has worn out. If so, what? Similarly, if a manufacturing machine is not working properly, some components that may be buried in the machine are worn. As with a medical diagnosis, the remedy can only come when the cause is identified. So too with friction, wear, and erosion. There is a need to identify the specific type of wear, friction, or erosion before proceeding to solve the problem. It is the purpose of this chapter to introduce some of the language of friction, wear, erosion, and lubrication and define various modes or types of friction, wear, and lubrication. The objective is to establish a foundation of process understanding before proceeding to discuss ASTM and other tests. This book concentrates on ASTM standard tests that focus on attrition of solids or friction between contacting solids. It will not discuss tests that are used by lubricant formulators to measure petroleum properties-only friction and wear tests that are likely to be performed by lubricant users. There are many physical property tests performed on lubricants. These are considered outside the scope of this guide. This book covers important friction tests and important tests in the various categories of wear, erosion, and lubricated wear. It starts with a discussion on simulations-models that can be used to make wear and friction tests unnecessary. It ends with a chapter on correlation of lab tests with service.