Notched tensile test

Pendulum hammer

The notched impact tensile test is usually carried out with a pendulum impact tester . It is used in materials testing to examine the behavior of test specimens at a relatively high impact speed and to evaluate the toughness or brittleness of plastics and elastomers .

In principle, the notched impact tensile test (use of notched test specimens) is particularly suitable for investigating materials for which the performance of impact bending tests and notched bar impact tests according to Augustin Georges Albert Charpy ( three-point bending arrangement) is unsuitable due to the nature of the test specimen (thickness, flexibility). Very thin, e.g. B. made of foils or very flexible test specimens ( elastomer materials ) can consequently be subjected to impact stress and thus their toughness properties can be assessed under sudden loading conditions.

Implementation of the method

The test is carried out in the notched impact tensile test with a relatively high rate of deformation. The method is suitable for test specimens made from molding compounds or taken from semi-finished products and molded parts and is used for production and quality assurance . With the conventional notched impact tensile test, it is also possible to record the mechanical anisotropy behavior by removing test specimens from test plates or components in different directions and testing them.

To carry out such experiments, pendulum impact machines are used, which are provided with the additional equipment necessary for impact tensile tests, such as special pendulum hammers and clamping devices.

The sample is usually designed as a rod with notches. The dimensions of the test body are:

• Length L = 80 mm
• Width W = 10 mm

The notch depth a of the notches on both sides is 2 mm each

To carry out notch impact tensile tests, the test specimens are fixed by means of a fixed clamping device on one side and cross-yoke clamping on the other side within the testing device of the pendulum hammer. After the pendulum hammer is released from its deflection position, the test specimens are suddenly loaded in the longitudinal direction until they break. This is why this test is known as the impact tensile test.

Parameters

As a result of the experiment, the impact work E _{c is} determined and then the conventional notched impact _tensile strength a _{tN is} determined:

${\displaystyle a_{\text{tN}}={\frac {E_{\mathrm {c} }}{b_{\mathrm {N} }\cdot h}}}$

For the determination of fracture mechanical parameters of foils and elastomers, an instrumentation of the conventional notched impact tensile test with force and displacement sensors is necessary. The method of the instrumented notched impact tensile test increases the informative value of the results obtained and enables the material properties to be optimized and the performance of components to be assessed better.

See also

• Pendulum hammer
• Pendulum
• Norms

Individual evidence

1. ↑ ^{a b} DIN EN ISO 8256. In: DIN German Institute for Standardization eV, 10772 Berlin, din.de. May 2005, accessed May 13, 2020 . 
2. ↑ Grellmann, W., Seidler, S .: Quality improvements for elastomers - application of the instrumented impact test . In: Polymer Testing, pp. 233-286. . 2013. doi : 10.3139 / 120.100575 .
3. ↑ Reincke, K .: Elastomeric Materials - Relationship between mixture recipe, structure and mechanical properties as well as deformation and fracture behavior. Habilitation. Martin Luther University Halle-Wittenberg Shaker Verlag, 2016, ISBN 978-3-8440-4637-3 .