Tensile testing

For the tensile test several machines of known manufacturers are available . With tese machines not only tensile but also compression, bend, dynamic load and pulsating stress tests can be carried out in material, component and functional testing. You also have a wide range of applications from plastic and rubber testings over paper, fabric, foam, steel and wire up to component testing.

Tensile test of metals

The method for the execution of tensile tests of metals at RT and the definition of the determined characteristic values ​​are specified in DIN EN ISO 6892-1:2009-12. 

The tensile test is used to determine the material behavior under uniaxial, evenly distributed over the cross section tension. For this purpose, a sample is evenly and smoothly stretched until a fracture occurs, and thereby load and extension of the sample is measured continuously.

The GWP provides tensile tests at the locations Munich, Leipzig and Dillingen in the Saarland.

Standards: DIN EN 10002-1, EN ISO 6892-1, ISO 6892, ASTM E 8, ASTM E 21, DIN 50154; DIN 50125

Tensile testing of plastics

The tensile testing according to DIN EN ISO 527 determines the tensile properties of plastics and plastic composites.

Tensile force and extensions are measured, tension and extension calculated and illustrrated as a diagram.  Further specific values can be calculated or rather directly read off in the tesnion- extension- diagram.

With the deformability behavior you can differ between 3 types of plastics:

  • Hard-stiff plastics: like e.g. polystyrene, hard-PVC or PMM. Their most important specific value is their tensile strength ơB.
  • Hard – but flexible plastics: These are plastics with distinctive tensile stress at yield ơS like e.g. hard-polyethylene or polyamide
  • Rubbery-elastic plastics: with high elongation at break ƐR like e.g. styrene-butadiene-rubber or soft-polyethylene

Another important material parameter ist he elasticity modulus, which markst he stiffness of a material.

Tensile testing of plastics
Tensile testing of plastics

Bake-hardening-index

The DIN EN 10325 specifies a procedure for the determination of yield stress increase by heat treatment (bake-hardening-index). Bake-hardening is a controlled aging process, which can lead back present carbon and nitrogen to the steel in solid solution. At this test an index is determined, which specifies the yield stress increase of a sample that was plastic elongated by 2 % and afterwards selected heat treated.

Standard: DIN EN 10325

Tensile testing with r- and n-value determination

For the characterization of transformation properties often the r- and n-values in the tensile testing are determined.

The ISO 10275 specifies a procedure for the determination of the consolidation exponent, often also called n-value, at flat metal samples, commonly metal sheet or band.  For the calculation of the n-value a test according to ISO 6892 is performed and with help of an axial clip gauge a tension-extension-diagram is created. The n-value is calculated over the whole area of the consistent plastic extension – normally from the start of the area of the consistent solidification, after passing the yield point, until shortly in front of the point, where the tensile strength Rm is calculated.

The r-value is the relation of logarithmic width distortion to logarithmic thickness changing. For the sample layer the same terms like for the n-value determination apply. An average r-value is calculated with the angular positions 0°, 45° and 90° to the direction of grain kept single values. With the r-value it is possible to determine if materials (metal sheets) behave anisotopic. Anisotopy gets clear when r0,r45 und r90 differ.

N-values and r-values are exclusively determined in thin sheets. Thin sheets are metal sheets with a production thickness of max. 3 mm. 

N-values and r-values are exclusively determined in thin sheets. Thin sheets are metal sheets with a production thickness of max. 3 mm. 

Tensile testing at elastomers

The standards ASTM D412 or the ISO 37 "Tensile Testing of rubber and elastomers" cover a wide range of materials, including thermoset and thermoplastic elastomers. The samples are usually poured or punched. To the characteristics, which are determined during such a tensile testing, among other things the ultimate tensile strength, the elongation of break, the tension with a certain stretch, the stretch with a certain tension as well as with some thermoplastic elastomers and Compounds the yield stress and stretching stretch belong.

Standards: ASTM D 412, ISO 37

Tensile test on leather

The determination of the tensile strength of leather is defined in DIN 53354. The tensile strength of leather is the possible tensile load of a leather until it tears. The tensile strength within the leather hide is very different in the longitudinal and transverse directions.

The tensile strength increases with increasing fat content of the leather. However, there are many other parameters, such as stiffness, age and beard, which influence the tensile direction. Leather is a natural product, therefore each hide behaves differently from the outset.

The tensile strength of cowhide leather is between 8 - 25 N/mm². The automotive industry requires at least 200 N per 5 cm.

Standards: DIN 53354, DIN EN ISO 3376