INTRODUCTION

Many biologists don't want to know much about the ‘property testing’ of materials because it sounds extraneous to many problems and something that could be handled in a routine manner by qualified technicians. Why be bothered? While it is certainly true that some biomechanical investigations do not require any detailed knowledge of this, the material properties of foods lie at the heart of the analysis of dental function. Accordingly, I suggest that the reader at least skim this appendix before tackling Chapters 4 to 6. The aim is to make material properties simple to grasp and fun to contemplate. I include basic concepts, some examples and a reference list with more for those that need it.

THE BASICS

When a force loads a solid object, it distorts. In mechanics, this distortion is called deformation. If the object deforms sufficiently, then it cracks (fractures). To document these behaviours, mechanical tests need to record the force applied to the object and the deformation that this produces. There are two options: controlling the force to see how the deformation varies or vice versa. Prior to fracture, there is little difference what is chosen, but to understand what happens afterwards, it is best to control deformation because this controls the rate of crack growth much more effectively.

Information about the behaviour of the deformed object can be recorded conveniently on a force–displacement graph, such as that shown in Fig. A.1.