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The Wear Severity Classification feature is one of four parts of the Wear Particle Atlas CD-ROM. It provides an exclusive filtergram-based wear severity differentiation component which embraces 456 images and over 100 application cases in order to differentiate machine wear severity levels with improved consistency. The wear severity levels are divided into either10 levels (from Level 1 to Level 10) or 8 levels (Level 3 to Level 10). Each characterizes wear deterioration from initial wear to severe wear. An example for cutting wear particles is shown below.

Example of Cutting Wear Severity Index

To be objective in its differentiation, the Atlas first defines the "key features" for each severity level. This is the quantitative, measurable criterion based on the size distributions and wear-mode-related type distributions of the wear particles. Second, the Atlas provides 1-5 wear cases at each severity level that approximately meet the criteria of the designated severity level. Each example consists of 4 representative wear particle images. By matching both measurable criteria and visible images, a random wear particle sample can be coded with a certain severity level number. For example, the metal particles in an oil sample are:

• ferrous fatigue wear particles;
• the size of the fatigue wear particles is up to 100 µm, and
• the concentration of the fatigue wear particles ranging between 50-100 µm in size is 200-300/ml.

The quantitative features of this sample meet the criteria for Level 6 of the fatigue wear severity. Further, the features of the wear particles of this sample are equivalent or similar to those of the examples (cases) in the Atlas. Therefore, the wear severity level of this oil sample can be differentiated as 6.

As can be seen from the example below, the criteria of fatigue wear severity level 6 is:

• Up to 100 µm in size;
• Predominant laminar particles; and
• Concentration of laminar particles ranging between 50-100µm are greater than 100/ml

Example of Fatigue Wear, Severity Level 6

This differentiated Level 6 is a universal wear severity level. It can be defined as a "normal", or an "abnormal" or even a catastrophic condition. The determination depends on the criticality, operational environment, and expected life of the machine from which the particles came. For example, if this sample came from a large slow rolling bearing, this severity level 6 may be defined as a "mildly abnormal" wear condition. However, if this sample came from a critical gear system, this Level 6 maybe specified as an "unacceptable" or even a "severe" condition. It is from this perspective that the wear severity differentiation in the Atlas provides an approximate yardstick for measuring machine severity. This enables an activity, which currently is subjective, to be quantitative and standard.

Thank you for visiting the "Wear Severity Classification" feature of the Wear Particle Atlas CD-ROM. Additional features can be reviewed by returning to the Wear Particle Atlas CD-ROM Features Index.