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To simulate CFA and OCA wear we have designed the ACTA Wear Machine.
Tooth brushing wear is simulated with a modified polishing machine. We are working on a page on that.

Introduction

P. Pallav, PhD

Results from brushing tests are incomparable to result from food wear experiments.

It is a common misunderstanding that wear resistance would be a material property. This is not true; wear and wear resistance are system properties. (Czichos, 1978)

Even if the wear rate of a certain material in a certain experiment is known, it is hardly possible to predict the wear of a new material in the same set up from the new physical properties, since a different material usually differs in several properties and the relative influence of each property in a specific system is normally hardly known accurately enough.

Wear depends, amongst others, on a myriad of physical and chemical properties of the acting surfaces, on the structure of the surfaces (roughness, inclusions, filler particles, etc.) and lubricant (saliva, adhesion, particles, etc.) and on the apparatus in which wear occurs. 

Just about the first law of tribology might be that nothing is certain. Anyone who is familiar with tribology will confirm this.
It is usually amazingly inaccurate, when the wear of a new material is predicted based on any set of material properties, as compared to materials which have been tested.

However, when the general wear equation (below) applies accurately enough, and when the wear rates of materials in a similar setup @ defined circumstances are known, a prediction of wear versus time can usually be made, by performing the appropriate integrals.

Rules of thumb

A The General Wear Equation.
If all other circumstances are constant, wear is, usually to a limited extent (see: B), proportional to pressure and velocity.
Wear rate = height loss
time span		 = dh/dt = k x p x v (Equation 1),
where h = height loss,
t = time lapse,
k = specific wear rate (a constant of proportionality)
p = pressure and
v = velocity.
B Changes in the set up or changes of the magnitude of the load (velocity, pressure), readily yield a completely different wear regime with a completely different wear rate.
C Wear tends to increase with friction and a contact between similar materials generally wears faster, since in this case the adhesion (friction) is usually stronger than in the case of dissimilar materials.
D Higher compression, tensile and shear strength, hardness and ductility generally decrease wear. However, hard materials tend to be brittle and ductile materials tend to be soft.
E High hardness and roughness are properties that may cause increased wear at an antagonist, as well as hard inclusions (filler particles in composites!) emerging from the surface (exclusions?).
F Lubricants (water too) normally reduce wear by means of qualities such as adhesion and viscosity. Particles transported by it however, generally increase wear, depending on the nature, size and quantity of the particles.

 

Czichos H (1978): Tribology - a Systems Approach to the Science and Technology of Friction, Lubrication and Wear. Elsevier Publ. Co., Amsterdam.

Peterson MB and Winer WO, eds. (1980): Wear Control Handbook. The American Society of Mechanical Engineers (ASME), New York.