Читать книгу Manual of Laboratory Testing Methods for Dental Restorative Materials - Paromita Mazumdar - Страница 15

Compressive testing is normally applied to materials that are expected to be placed in situations of occlusal loading. Since most of mastication forces are compressive in nature, it is important to investigate materials under this condition. To test compressive strength of a material, two axial sets of force are applied to a sample in an opposite direction, in order to approximate the molecular structure of the material. Here, cylindrical‐shaped specimens are tested. The dimensions of the samples should have a relation of length to diameter of 2 : 1. When this proportion is exceeded, it can result in undesirable bending of the specimen. In the same manner of tensile strength, nominal value of compressive strength also is determined by the reason of load by cross‐sectional area (Kgf/cm²). Stress–strain curve of investigated material is determined in the same manner as established to tensile tests. Thus, the elastic modulus can also be determined by the stress–strain ratio in the elastic region [11] (as shown in Figures 1.7 and 1.8).

Figure 1.7 Direction of force is perpendicular to the object.