5.1: Introduction

The mechanical properties of metals are of huge importance. Most industrial sectors - aerospace, automotive, construction, energy, mining, processing etc - rely heavily on a wide range of metallic components. Commonly, these operate, intermittently or continuously, under highly demanding conditions (of temperature, chemical environment, irradiation and, particularly, applied mechanical load). Efficient design often leads to components being used under conditions close to various limits for the metal concerned. A range of mechanical properties are relevant, but the most important are those that dictate the onset and progression of plastic deformation, and subsequent fracture. They depend in a highly complex manner on microstructure, such that they must always be measured experimentally. Furthermore, the microstructure, and hence the properties, can change during service. Extended periods under various combinations of stress, temperature, irradiation, corrosive environments etc can cause significant changes. Central to this scenario, and indeed to the whole gamut of metal processing and usage, is the way in which mechanical testing of metals is carried out. Various types of test have been developed, but the most widely used are those based on uniaxial (tensile or compressive) loading. These appear simple, but in detail they are not. Another type of test in extensive use, also straightforward in principle, but not in detail, is indentation testing. This type of test has long been used to obtain semi-quantitative "hardness numbers", but it can also be employed in a more sophisticated manner to infer stress-strain curves. This TLP covers all of these tests and also provides some basic background to them.