Compressive strength

As a pressure resistance, the resistance of a material under the action of pressure forces, is referred to. Is the compressive stress greater than the compressive strength of the body, so it is destroyed. Most of the materials differ in their compressive and tensile strength, such as rocks or cast iron. An example of a material that can take up only compressive forces in the absence of limiting the transverse stretching, is sand.

The compressive strength is the ratio of tensile strength and cross-sectional area A of the sample body. It is usually expressed as force per unit area (N / mm ²), so the unit has a voltage.

The compressive strength is tested in the laboratory. Depending on the nature and implementation of this compression tests are distinguished:

• Unconfined compressive strength
• Biaxial compressive strength
• Triaxial compressive strength

In examining the unconfined compressive strength of the specimens can yield in the two lateral directions; in biaxial deformation is prevented in one of both lateral directions and the three-axial both. The compressive strength therefore increases in this order.

The test methods are defined in standards (DIN, Önorm ).

The compressive strength can also be directional. An example is rock, when the rock crevasses crossed or geschiefert. Another example is a timber, which is generally in the direction of the wood fibers and the strain has a higher compressive strength than perpendicular thereto.