Structural components must resist various applied loadings. Their nature is very diverse: aggressive environments, temperature and mechanical loads. However, we will only consider this last area in this book. Engineers must design parts so their deformations under these loads remain acceptable and they are not damaged or broken. In many cases structures need to be as light as possible, in order to save materials on the one hand, but above all to decrease energy consumption on the other hand. It is thus important to optimize the shape of parts and to choose the materials they are made of so that they perform without excessive deformations and without loss of integrity. Following design, problems can arise in service, such as crack initiation, which require calculations of the stress and strain distributions. Finally, failure assessments also require such analyses. To reach these objectives, more and more sophisticated design tools are available for engineers, provided that they are suitably supplied with reliable data concerning the mechanical behavior of materials. This is the aim of mechanical testing.

The design of a part requires the knowledge of the relations between applied loads and deformations, as well as the limits not to be exceeded at the risk of damage or fracture. This will be the case, for example, with the stiffness of a spring and with its yield load. More generally, these relations involve the stresses and the strains, and more precisely the two corresponding tensors. Solving the problem is achieved by integrating the three stress...