Elastic limit

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The elastic limit of a material is the size of the mechanical stress below which the material is elastic , i.e. i.e., it will return to its original shape when the load is removed (non-permanent / reversible deformation). If the elastic limit is exceeded, irreversible elongation or compression or plastic deformation occurs. The elasticity limit values ​​are used along with other material parameters for the calculation and determination of the strength and stability of mechanical constructions.

In the case of tensile stress, for example, the elastic limit is the point on the stress-strain diagram at which the stress curve deviates from the linear course, although this point is usually not clearly defined, but (also) depends on the measurement method:

  • schematic stress-strain diagram with pronounced yield point
    The yield point describes the stress up to which a material does not show any visible plastic strain. If the tension drops again when a further strain is applied, there is an upper yield point (index H for high ) and a lower yield point (index L for low ).
  • schematic stress-strain diagram with continuous start of flow and entered 0.2% proof stress
    In the case of materials with a continuous start of flow, however, the “yield point” cannot be clearly read from the diagram (see Fig .: where exactly does the elastic straight line end there?), And so in such cases a “ yield point ” is specified instead (symbol usually ), which can be clearly read in any case, namely the stress that results in a slight permanent deformation
    after releasing the load . How large this slight permanent deformation may be is indicated as an index, the usual value here is 0.2% in exceptional cases also 0.01% or 0.005%

See also