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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.