2. Read and translate the text: Compressive Stress

Strength of materials is materials science applied to the study of engineering materials and their mechanical behavior in general (such as stress, deformation, strain and stress-strain relations). Strength is considered in terms of compressive strength, tensile strength, and shear strength, namely the limit states of compressive stress, tensile stress and shear stress respectively. The effects of dynamic loading are probably the most important practical part of the strength of materials, especially the problem of fatigue. Repeated loading often initiates brittle cracks, which grow slowly until failure occurs. Stress is the force applied per unit area.

Compressive stress (or compression) is the stress state when the material (compression member) tends to compact. A simple case of compression is the uniaxial compression induced by the action of opposite, pushing forces. Compressive strength for materials is generally higher than that of tensile stress, but geometry is very important in the analysis, as compressive stress can lead to buckling.

In engineering, buckling is a failure mode characterized by a sudden failure of a structural member that is subjected to high compressive stresses where the actual compressive stresses at failure are smaller than the ultimate compressive stresses that the material is capable of withstanding.

Compressive stress is the stress applied to materials resulting in their compaction (decrease of volume). When a material is subjected to compressive stress then this material is under compression. Usually compressive stress applied to bars, columns, etc. leads to shortening.

Loading a structural element or a specimen will increase the compressive stress until the reach of compressive strength. According to the properties of the material, failure will occur as yield for materials with ductile behavior (most metals, some soils and plastics) or as rupture for brittle behavior (geomaterials, cast iron, glass, etc).

As is known 'slender' structural elements (such as skeet columns or truss bars), increase of compressive force F leads to structural failure due to buckling at lower stress than the compressive strength, according to Euler.

Compressive stress has stress units (force per unit area), usually with negative values to indicate the compaction. However in geotechnical engineering, compressive stress is represented with positive values.

A compression member is a general class of structural elements of which a column is the most common specific example.

For a compression member, such as a column, the principal stress comes mainly from axial forces, that is forces that fall along one line, usually the centerline.

The strength of a short column is determined by strength limit of the material. The strength of a column of intermediate size is limited by its degree of inelasticity. A long column is constrained by the elastic limit (that is by Euler's formula).

3. Answer the following questions:

   1. What is stress?

   2. What kinds of stress do you know?

   3. What is compression?

   4. What do you know about buckling?

   5. What is specimen?

   6. With what values is compressive stress represented?

   7. What is constrained by Euler's formula?