What are stretches?

Elongation describes the change in length of a material under tensile load and is given as a percentage in relation to the original length.

 

Types and meaning of stretching

  • Elastic elongation: The material returns completely to its original length after being relieved.
  • Plastic elongation: Part of the change in length remains permanent - typical for many thermoplastics under high loads.
  • Hysteresis strain (special case with elastomers): Internal friction converts part of the applied elastic energy into heat, so that a residual elongation remains after the load is removed. When the temperature increases, the elastomer can return to its original length (Gough-Joule effect).
  • Elongation at break: Is measured in the tensile test and describes the elongation until breakage

 

Materials with high elongation can deform considerably before they tear. These properties are ideal for dynamically loaded components such as Seals or spring elements.

 

Measurement of elongation

The elongation is determined in standardised tensile tests (e.g. DIN 53504, ISO 37). It is calculated as:
ε (%) = (l - l_0) / l_0 × 100

 

Example:

  • Initial length: 50 mm
  • Expansion length: 100 mm

Resulting elongation: 100%