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Encyclopedia > Compressive stress

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 behaviour (most metals, some soils and plastics) or as rupture for brittle behaviour (geomaterials, cast iron, glass, etc).

In long 'slender' structural elements (such as columns or truss bars), increase of compressive force F leads to failure due to buckling at lower stress than the compressive strength, according to Euler;

Fb = π2 x E x I / l2

The 'slenderness' of the element depends on its length, the way the ends are supported and its cross section. The slenderness is expressed with the letter lambda as; λ = lb / √(I/A)

With λ and σ = F/A, Euler's formula can be rewritten for the buckling stress as; σb = π2 x E / λ2

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

Compare: tensile stress

Results from FactBites:

 Arc tube with residual-compressive-stress layer for discharge lamp unit and method of manufacturing same - Patent ... (5448 words) As a result, the inventor discovered that retention of compressive stress produced in the pinch seal portions 5b during the arc tube manufacturing process causes a thermal stress in the glass layer in the pinch seal portion to disperse due to rise in the temperature occurring after turning the arc tube on. The compressive stress layer is previously formed in a predetermined wide region in the axial direction or/and the circumferential direction on the surface of hermetic contact between the glass layer and the electrode rod. Therefore, the compressive stress layer (the residual compressive stress layer) formed in the large range efficiently relaxes (absorbs) the thermal stress produced in the glass layer as the temperature is raised.
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