Wear - Measurement

Measurement

Today there exist a couple of standard test methods for different types of wear to determine the amount of material removal during a specified time period under well-defined conditions.
The ASTM International Committee G-2 attempts to standardise wear testing for specific applications, which are periodically updated. The Society for Tribology and Lubrication Engineers (STLE) has documented a large number of frictional wear and lubrication tests. But all test methods have inbuilt limitations and do not give a true picture in every aspect.
This can be attributed to the complex nature of wear, in particular "industrial wear", and the difficulties associated with accurately simulating wear processes.(ref4)

A standard result review for wear tests, defined by the ASTM International and respective subcommittees such as Committee G-2, should be expressed as loss of material during wear in terms of volume. The volume loss gives a truer picture than weight loss, particularly when comparing the wear resistance properties of materials with large differences in density.
For example, a weight loss of 14 g in a sample of tungsten carbide + cobalt (density = 14000 kg/m³) and a weight loss of 2.7 g in a similar sample of aluminium alloy (density = 2700 kg/m³) both result in the same level of wear (1 cm³) when expressed as a volume loss. The inverse of volume loss can be used as a comparable index of wear resistance.
Standard wear tests are only used for comparative material ranking of a specific test parameter as stipulated in the test method. For more realistic values of material deterioration in industrial applications it is necessary to conduct wear testing under conditions simulating the exact wear process.(ref4)

The working life of an engineering component is expired when dimensional losses exceed the specified tolerance limits. Wear, along with other ageing processes such as fatigue and creep in association with stress concentration factors such as fracture toughness causes materials to progressively degrade, eventually leading to material failure at an advanced age.
Wear in industrial applications is one of a limited number of fault factors in which an object loses its usefulness and the economic implication can be of enormous value to the industry.(ref 4)

The Archard Equation is the classic wear prediction model - see Bisson