Instrumented Tensile Impact Test (ITIT)
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Instrumented tensile impact test (ITIT)
General
The instrumented tensile-impact test (ITIT) is carried out with the aim of determining fracture mechanics values for films and elastomers, as well as for thermoplastics.
Validity of ITIT
By electronic instrumentation impact-tension pendulum impact test set-ups (see: impact loading pendulum impact tester), i.e. by fitting strain gauges or a piezoelectric force transducer to record the load--time curve, a better understanding of the toughness properties is achieved. It is possible to define and evaluate different energy contributions to the total deformation, as well as to determine measured variables such as the maximum load Fmax and the corresponding deformation lmax. In the context of material comparison or material optimisation, these measured variables provide important insights into the interpretation of the determined characteristic values for crack toughness.
Application of the method
Test specimens with metal-bladed notches on both sides (DENT-specimens, see Fig. 1) are used for the investigations.
| Fig. 1: | Fig. 1: Double-sided notched test specimen for carrying out the notched tensile impact test |
The selection of the pendulum hammer to be used – and thus the maximum energy delivered – depends on the properties (see: fracture mechanical testing) of the material under investigation. In some cases, the pendulum impact testers also feature additional units for precisely adjusting the angle of fall and, consequently, the pendulum hammer velocity. This means that, in this case, the fracture mechanics properties of plastics can also be characterised as a function of the loading speed (see: test speed). The test specimens have the dimensions L ≥ 64 mm, W = 10 mm and a total notch depth a = 2 mm. The clamped length l0 is 30 mm. The test setup is shown in Figs. 2 and 3 below.
| Fig. 2: | Schematic diagram of the test setup for the instrumented tensile-impact test (top view) |
| Fig. 3: | Test procedure for the instrumented tensile-impact test (side view) |
Specification of material values
Based on the results of the instrumented tensile- impact test, fracture mechanics values are calculated from the evaluated load–extension diagrams for the toughness characterisation. These toughness values are primarily Jd values, which quantify the resistance of the material under investigation to the propagation of an unstable crack. One advantage of these characteristic values compared with the notched tensile-impact toughness atN determined in the conventional tensile-impact test is, for example, their particular sensitivity to microstructure.
See also
- Fracture mechanical testing
- Electronic instrumentation
- MPK-Procedure MPK-ITIT
- Instrumented Charpy impact test
- Impact loading pendulum impact tester
- Impact loading plastics
- Toughness
References
- Reincke, K.: Testing of polymeric films. In: Grellmann, W., Seidler, S. (Eds.): Polymer Testing. Carl Hanser Munich (2022). 3rd. Edition, p. 643–678 (ISBN 978-1-56990-806-8; e-Book ISBN 978-1-56990-807-5; ePub ISBN 978-1-56990-802-2; see AMK-Library under A 22)
- MPK-Procedure MPK-ITIT (2012-06): Testing of Plastics – Instrumented Tensile-Impact Test (ITIT): Procedure for Determining the Crack Resistance Behaviour Using the Instrumented Tensile-Impact Test
- Grellmann, W.: Instrumented tensile-impact testing for product evaluation. In: Grellmann, W., Seidler, S. (Eds.): Polymer Testing. Carl Hanser, Munich (2022) 3rd Edition, pp. 272–279 (ISBN 978-1-56990-806-8; see AMK-Library under A 22)
- Reincke, K.: Bruchmechanische Bewertung von gefüllten und ungefüllten Elastomerwerkstoffe. Mensch & Buch Publishing, Berlin (2005), (ISBN 978-3-86664-021-4; see AMK-Library under B 1-13)
- Reincke, K., Grellmann, W.: Elastomers. Impact loading. In: Grellmann, W., Seidler, S.: Mechanical and Thermomechanical Properties of Polymers. Landolt-Börnstein. Volume VIII/6A3, Springer, Berlin (2014) pp. 502–509, (ISBN 978-3-642-55165-9; see AMK-Library under A 16)
- Reincke, K., Grellmann, W.: Approaches to characterise the mechanical properties of films and elastomers. In: Grellmann, W., Langer, B.: Deformation and Fracture Behaviour of Polymer Materials. Springer Series in Materials Science 247, Springer, Berlin Heidelberg (2017) 225–336 (ISBN 978-3-319-41877-3; e-Book: ISBN 978-3-319-41879-7; see AMK-Library under A 19)
For further literature references, see electronic instrumentation.