Metals and many plastics, for example, are more efficient at resisting tensile loads. Therefore, they are more commonly tested using tensile loading, depending on the application, of course. Materials, such as concrete, brick, and some ceramic products, are more often used in applications for their compressive loading properties and are, therefore, tested in compression. Again, it is important to choose the test that best reflects the loads and conditions the material will be subjected to in application or service.
For materials that are brittle only slight deformation occurs prior to fracture(FIG. A).
buckling—In addition to compressive failure by crushing of the material, compressive failure may occur by ( 1) elastic instability over the length of a column specimen due to nonaxiality of loading, (2) inelastic instability over the length of a column specimen, (3) a local instability, either elastic or inelastic, over a small portion of the gauge length, or (4) a twisting or torsional failure in which cross sections rotate over each other about the longitudinal specimen axis. These types of failures are all termed buckling as shown in Fig. C.
barreling—restricted deformation of the end regions of a test specimen under compressive load due to friction at the specimen end sections and the resulting nonuniform transverse deformation as shown schematically in fig. B.