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- Dielectric relaxation (2)
- Microplastic (2)
- Microplastics (2)
- Analysis (1)
- Analytik (1)
- Beispiele industriell angew. automat (1)
- Components and Performance of a Test Equipment (1)
- Composite (1)
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Relaxation behaviour of thermoplastic polyurethanes with covalently attached nitroaniline dipoles
(2002)
Thermoplastic polyurethanes with covalently attached nitroaniline chromophores exhibit a strong high-temperature relaxation associated with a glass transition rather than the typical frequency-independent loss due to the aggregation of polymer chains via hydrogen bonds. This relaxation behaviour suggests the formation of an amorphous structure without separation into soft-segment and hard-segment phases. In such a structure, a field-induced orientation of molecular dipoles is stabilised by the high viscosity of the material below its glass transition. The dipole orientation yields a pyroelectric effect caused by dipole-density changes upon thermal expansion and contraction.
The changes in phase separation are investigated by varying the chain length of the soft-phase component and studying its influence on the calorimetric, dynamic-mechanical, and dielectrical properties. Good correlation was found between differential scanning calorimetry, dynamic-mechanical analysis and dielectric spectroscopy as well as measured and calculated pyroelectric coefficients. This leads to a uniform picture of the structural changes caused by the incorporation of nitroaniline chromophores into the polyurethane structure.
Visualization of material defects - modern approaches in acoustical and electrical NDE-methods
(2008)
Increasing demands in materials quality and cost effectiveness have led to advanced
standards in manufacturing technology. Especially when dealing with high quality
standards in conjunction with high throughput quantitative NDE techniques are vital to
provide reliable and fast quality control systems. Fast NDE-systems using a high degree
of automatisation can be used for both determining the degree of integrity of the
components under test and indicating a change of production parameters as well.
However, independently of the applied NDE method and the underlying physical
principle a reliable visualisation of hidden defects within the component under test is
based on a sufficient high signal to noise ratio (SNR) and a high spatial resolution. In this
talk we illuminate two standard NDT methods such as Ultrasonic Testing and Eddy
Current Testing and show their physical principles also discussing the interaction
between sound waves or induced eddy currents with different kinds of material defects.
This introduction substantiates the attainable SNR and spatial resolution of both methods
with respect to defect sizing and defect classification. As a first future prospect we report
on the SAFT-algorithm to improve SNR and spatial resolution paving the way for a flaw
sizing approach in ultrasonic inspection. As a second modern NDE approach we
represent the use of small magnetoresistance sensor arrays for EC testing of Al-laser
welds or for testing superconducting wires. The high sensitivity and small extent of GMR
sensors results in a remarkably SNR and spatial resolution offering new visualisation
techniques for defect localisation, defect characterization and tomography-like mapping
techniques.