Micro-Damage Limit
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Micro-damage limit
Importance of introducing micro-damage limits
The Knowledge of the micro-damage limit of plastics is particularly important for an event-related interpretation of the deformation phases of stress tests (especially quasi-static tensile tests, bending tests, instrumented Charpy impact tests) and the dimensioning of plastic components (damage mechanics).
Definition of limit values and specification of quantitative values
The micro-damage limit is a range in which the first irreversible damage induced by loads occurs, which is usually invisible and is not characterised by a changed habitus in the stress–strain diagram.
The stress or strain in the transition from linear-viscoelastic to non-linear-viscoelastic behaviour (see: elasticity) can be used as a quantitative value for determining the onset of micro-damage, but it is not possible to determine these values precisely using conventional tensile testing alone.
Here, coupled measurement methods such as
- Instrumented Charpy impact test (ICIT) with acoustic emission,
- Tensile test and acoustic emission analysis,
- Tensile test/acoustic emission/thermography.
must be used, which react sensitively to structural changes in the material. In addition, morphological analyses must be carried out before and after loading.
The coupled measurement methods are also referred to in the literature as in-situ methods or sensor-based methods or hybrid methods of polymer diagnostics.
See also
- Laser extensometry
- Instrumented hardness testing – Method & Material parameters
- Polymer testing
- Heterogeneity
- Elasticity
References
- Grellmann, W., Langer, B.: Methods for Polymer Diagnostics for the Automotive Industry. Materialprüfung 55 (2013) 17–22 Download as pdf
- Bierögel, C.: Hybrid Methods of Polymer Diagnostics. In: Grellmann, W., Seidler, S. (Eds.): Polymer Testing. Carl Hanser, Munich (2022) 3rd Edition, pp. 497–514 (ISBN 978-1-56990-806-8; E-Book: ISBN 978-1-56990-807-5; see AMK-Library under A 22)